Halogen-free phosphorus-free intrinsic flame-retardant type three-functionality benzoxazine monomer, nitrogen-rich resin, preparation method and application of halogen-free phosphorus-free intrinsic flame-retardant type three-functionality benzoxazine monomer
By designing halogen-free and phosphorus-free trifunctional benzoxazine monomers and melamine catalysts, nitrogen-rich benzoxazine resins with high cross-linking density are formed, solving the problems of flammability of polymer materials and flame retardant pollution, and achieving halogen-free and phosphorus-free intrinsic flame retardant properties with high heat resistance and flame retardancy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUAIBEI OASIS NEW MATERIAL CO LTD
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-19
AI Technical Summary
Existing polymer materials are flammable and decompose at high temperatures, and halogenated and phosphorus-based flame retardants pose health hazards and pollution problems. The flame retardant performance of existing benzoxazine resins has limited improvement and the process is complex.
A halogen-free and phosphorus-free trifunctional benzoxazine monomer was designed. Through the reaction of 2,4,4'-trihydroxybenzophenone with monoamines and aldehydes, and the addition of melamine as a catalyst, a nitrogen-rich benzoxazine resin with high crosslinking density was formed. The flame retardant properties were improved by utilizing nitrogen flame retardancy and hydroxyl hydrogen bonding.
It achieves intrinsic flame retardant properties without halogens or phosphorus, and has excellent heat resistance and flame retardant properties, high glass transition temperature, low heat release capacity and high char residue, making it suitable for aerospace, electronic communication and other fields.
Smart Images
Figure CN122059968A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer materials technology, specifically relating to halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomers, nitrogen-rich resins, preparation methods, and applications. Background Technology
[0002] The issues that humanity must face and address in the 21st century are protecting nature, protecting the environment, and protecting human health. While polymer materials are widely used in daily life, their susceptibility to decomposition at high temperatures and their continued combustion under flames severely limit their application in aerospace, electronics, communications, and transportation. Research shows that while halogenated flame retardants can improve the flame retardancy of polymer materials, their decomposition products can be harmful to human health. Phosphorus-based flame retardants can also improve the flame retardancy of polymer materials, but their poor thermal stability and high volatility, especially the production of large amounts of harmful fumes, have led to their gradual banning globally. It is noteworthy that intrinsically flame-retardant polymer materials do not require any flame-retardant additives and reduce flammability without sacrificing physical properties. Therefore, current theoretical and applied research in the field of polymer flame retardancy is developing towards halogen-free, phosphorus-free, and intrinsically flame-retardant materials.
[0003] Since the 1990s, benzoxazine resins have attracted significant attention from both academia and industry. Benzoxazine monomers form six-membered heterocyclic compounds via the Mannich reaction of phenols, amines, and aldehydes, which then undergo ring-opening polymerization during curing, resulting in benzoxazine resins with a network structure similar to phenolic resins. Benzoxazine resins possess a series of advantages, including no need for strong acid or base catalysts during curing, no release of small molecules during polymerization, and excellent mechanical, thermal, and electrical insulation properties. Currently, research on improving the flame retardant properties of benzoxazine resins has garnered widespread attention. One method involves constructing composite resin systems with other high-performance resins such as epoxy resins and synergizing them with phosphorus- or halogen-containing flame retardants to enhance flame retardancy. However, this method is complex and presents pollution problems. Another approach involves directly preparing highly crosslinked benzoxazine resins through benzoxazine monomer structural design to improve flame retardancy, and then synergizing them with phosphorus- and / or halogen-containing flame retardants to further enhance flame retardancy. Studies have shown that while increasing the crosslinking density can improve the thermal stability and flame retardancy of resins to some extent, it cannot significantly enhance the flame retardancy of benzoxazine resins. Although the introduction of flame retardants further improves the flame retardancy of benzoxazine resins, pollution problems still exist. Therefore, designing and preparing halogen-free, phosphorus-free, intrinsically flame-retardant benzoxazine resins with excellent flame retardant properties is of great significance. Summary of the Invention
[0004] The purpose of this invention is to provide a halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomer, a nitrogen-rich resin, a preparation method, and its applications. This invention provides a halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomer, which can be used to prepare a halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin. The resulting benzoxazine resin achieves intrinsic flame retardancy without any flame-retardant additives and exhibits excellent heat resistance and flame-retardant properties. The preparation method is simple, and the raw materials are economical and readily available.
[0005] To achieve the above objectives, the following technical solution is adopted: The first aspect of this invention provides a halogen-free, phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomer, which is a benzoxazine monomer with any structure shown in Formula 1:
[0006] or
[0007] or Formula 1 A second aspect of the present invention provides a method for preparing the above-mentioned benzoxazine monomer, comprising the following steps: 2,4,4'-Trihydroxybenzophenone, a monoamine, and an aldehyde compound are mixed in an organic solvent, wherein the monoamine is aniline, furfurylamine, or m-aminophenylacetylene. The pH is then adjusted to 2.5-3.5 with acid, and the mixture is reacted at 65-115°C for 8-130 hours under a nitrogen atmosphere. The mixture is then filtered and purified to obtain the final product. The structural formula of 2,4,4'-Trihydroxybenzophenone is shown in Formula 2.
[0008] Equation 2.
[0009] According to the above scheme, the molar ratio of phenolic hydroxyl, amino, and aldehyde functional groups in 2,4,4'-trihydroxybenzophenone, monoamine, and aldehyde compounds is 1:1:2.
[0010] According to the above scheme, the aldehyde compound mentioned in step 1 is formaldehyde or paraformaldehyde.
[0011] The reaction equation is as follows:
[0012]
[0013]
[0014] n = 1 ~ 100.
[0015] According to the above scheme, the acid used for pH adjustment is acetic acid, and the mass of acetic acid is 5% to 15% of the total mass of the reactants.
[0016] According to the above scheme, preferably, the preparation method of the above benzoxazine monomer is as follows: aldehyde compound and monoamine are added to an organic solvent, and after adjusting the pH range with acid, the reaction is carried out at 65~115℃ for 6~10h under a nitrogen atmosphere, and then 2,4,4'-trihydroxybenzophenone is added, and the reaction is continued at 65~115℃ for 2~120h.
[0017] According to the above scheme, the organic solvent used in the preparation of benzoxazine monomer is any one or a mixture of toluene, xylene, ethanol, chloroform, N,N-dimethylformamide, 1,4-dioxane, and tetrahydrofuran.
[0018] According to the above scheme, the purification process involves pouring the reaction solution into a methanol solution to precipitate, obtaining a milky white suspension. After standing, the supernatant is removed to obtain a brown precipitate. The brown precipitate is then dried and ground to obtain the benzoxazine monomer.
[0019] According to the above scheme, the preparation method of 2,4,4'-trihydroxybenzophenone is as follows: resorcinol and p-hydroxybenzoic acid are in a ratio of 1-1.3:0.9, boron trifluoride diethyl ether is used as a catalyst, high-boiling-range petroleum ether is used as a reaction solvent, the reaction temperature is 90-120℃, the reaction time is 2-6 h, after the reaction is completed, the mixture is cooled to room temperature, cold distilled water is added to wash and neutralize the residual catalyst, centrifuged, filtered and dried to obtain 2,4,4'-trihydroxybenzophenone yellow powder.
[0020] The reaction equation is as follows:
[0021] A third aspect of the present invention provides a halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin, which is prepared by curing any of the benzoxazine monomers shown in Formula 1 in the presence of melamine.
[0022] According to the above scheme, the mass ratio of melamine to benzoxazine monomer is 1:100 to 1:10.
[0023] The fourth aspect of this invention provides a method for preparing a halogen-free, phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin, comprising the following steps: dissolving the benzoxazine monomer in an organic solvent, adding melamine, wherein the mass ratio of melamine to benzoxazine monomer is 1:100 to 1:10, mixing evenly, and then curing at 80 to 180°C for 1 to 10 hours to obtain a halogen-free, phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin.
[0024] According to the above scheme, the organic solvent used in the halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin is any one or a mixture of toluene, xylene, ethanol, chloroform, N,N-dimethylformamide, 1,4-dioxane, and tetrahydrofuran.
[0025] The design of the halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomer and nitrogen-rich resin of this invention is fundamentally different from existing research on benzoxazine flame retardancy. This invention first designs and provides a halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomer as shown in Formula 1. Then, melamine is introduced during the monomer curing process to prepare the flame-retardant resin. Melamine can both catalyze the ring-opening polymerization of the trifunctional benzoxazine of this invention and form a nitrogen-rich benzoxazine resin with a highly cross-linked network structure with benzoxazine. As a novel curing catalyst, melamine can reduce the negative impact of steric hindrance and promote the polymerization of the trifunctional benzoxazine monomer. The trifunctional benzoxazine monomer is obtained by reacting 2,4,4'-trihydroxybenzophenone with a monoamine (aniline, furfurylamine, m-aminophenylacetylene). These trifunctional benzoxazine monomers have more cross-linking points than difunctional monomers, and theoretically can form a polymer network structure with a higher cross-linking density. However, due to its dense structure and significant steric hindrance, melamine can, to some extent, hinder the polymerization reaction. Melamine, as a weak base catalyst, allows its active amino groups to attack carbon atoms on the benzoxazine ring, promoting ring-opening polymerization to form a phenolic Mannich bridge structure. This effectively lowers the curing temperature of benzoxazine, thereby promoting the polymerization of trifunctional benzoxazine monomers. Furthermore, melamine can combine with the protonated nitrogen atoms formed by the ring-opening of benzoxazine to form a stable tribranched structure, resulting in a highly cross-linked network structure based on the triazine ring. Therefore, this nitrogen-rich benzoxazine resin with its highly cross-linked structure has a higher molecular weight, cross-linking density, and higher heat resistance than ordinary trifunctional benzoxazine resins. Additionally, its nitrogen content releases nitrogen gas, which does not support combustion, during thermal decomposition and promotes char formation, further enhancing the flame retardancy of the benzoxazine resin.
[0026] This invention also features unique design aspects for the benzoxazine monomer. The electron-withdrawing carbonyl group derived from 2,4,4'-trihydroxybenzophenone helps lower the energy range of the oxazine ring-opening process. Furthermore, the catalytic synergistic effect of melamine enables this trifunctional benzoxazine monomer to be used for curing benzoxazine resins, exhibiting low curing temperatures (minimum 80°C, maximum 180°C) and short curing times, while ordinary benzoxazine monomers typically have curing temperatures above 220°C, thus effectively improving their processability. In addition, the carbonyl group can form new hydrogen bonds with the hydroxyl groups generated from the benzoxazine ring-opening process, which also contributes to improving the thermal properties and flame retardancy of the trifunctional benzoxazine resin. Furfurylamine, derived from renewable resources, is chosen as the amine source, as it is widely available, environmentally friendly, and conserves petroleum resources. The synthesized 2,4,4'-trihydroxybenzophenone / furfurylamine type benzoxazine monomer exhibits a further cross-linking reaction of its furan ring during the benzoxazine ring-opening curing process. This furan ring forms new cross-linking bonds with the nitrogen atoms on the Mannich bridges formed after the oxazine ring opens, effectively increasing the cross-linking density of the cured resin. This leads to an increase in the glass transition temperature and thermal stability of the cured resin, while also significantly improving its flame retardant properties. Furthermore, the presence of oxygen atoms in furfurylamine allows for the formation of new hydrogen bonds with the hydroxyl groups generated during the benzoxazine ring-opening process. This effectively enhances the hydrogen bonding of the benzoxazine resin, further improving its heat resistance and flame retardancy. In particular, the 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene type benzoxazine monomer synthesized by selecting m-aminophenylacetylene as the amine source can undergo a polymerization reaction during the ring-opening reaction of benzoxazine curing, forming a new benzene ring with the other two carbon-carbon triple bonds. This effectively increases the crosslinking density of the cured resin. Moreover, the increase in the content of benzene rings with high heat resistance in the resin also leads to an increase in the glass transition temperature and thermal stability of the cured resin, especially significantly improving the flame retardant properties of the resin.
[0027] The beneficial effects of this invention are: (1) This invention provides a halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomer, which can be used to prepare halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin. Furthermore, the provided halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin exhibits excellent heat resistance and flame-retardant properties, and has a high glass transition temperature (280–410 °C). o C) High char content (50-75%), low limiting oxygen index (37.5-45.5), and low heat release capacity (20-70 J g). -1 K -1 Furthermore, all of them achieve a flame retardant rating of V-0. They can be widely used in aerospace, electronic communications, microelectronic devices, friction materials, and other fields.
[0028] (2) The preparation methods of the halogen-free and phosphorus-free intrinsic flame-retardant trifunctional benzoxazine monomer and the halogen-free and phosphorus-free intrinsic flame-retardant trifunctional benzoxazine nitrogen-rich resin provided by the present invention are simple to prepare and have high production efficiency.
[0029] This invention adjusts the pH of the system by adding acid, which promotes the formation of N-hydroxymethylamine intermediates of amines under acidic conditions and activates the ortho-hydroxyl position of triphenols, making 2,4,4'-trihydroxybenzophenone, monoamines and aldehydes more prone to cyclization reactions. This effectively increases the cyclization rate of oxazine rings (>95%) and the yield (>90%), successfully synthesizing the target product, a trifunctional benzoxazine monomer.
[0030] Furthermore, this invention uses boron trifluoride diethyl ether as a catalyst and high-boiling-range petroleum ether as a reaction solvent in the synthesis of 2,4,4'-trihydroxybenzophenone. This method is inexpensive, non-toxic, and offers advantages such as short reaction time (2 h), simple post-processing, high yield (>90%), and high purity (99.9%). It is easily industrialized and can be used for the efficient synthesis of trifunctional benzoxazine monomers. This invention solves the problems of high solvent toxicity, cumbersome post-processing, and reaction times exceeding 10 h in existing 2,4,4'-trihydroxybenzophenone synthesis techniques.
[0031] In addition, in the preparation of the halogen-free and phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin provided by the present invention, melamine is introduced during the curing process of benzoxazine monomers. Melamine, as a novel curing catalyst, can reduce the negative impact of steric hindrance, promote the polymerization of trifunctional benzoxazine monomers, and form a nitrogen-rich benzoxazine resin with a highly cross-linked network structure with benzoxazine. Attached Figure Description
[0032] Figure 1 : FTIR spectrum of 2,4,4'-trihydroxybenzophenone (T) prepared in Example 1; Figure 2 Nuclear magnetic resonance (NMR) of 2,4,4'-trihydroxybenzophenone (T) prepared in Example 1 1 H-NMR (a) and 13 C-NMR (b) spectrum; Figure 3 Mass spectrometry (MS) spectrum of 2,4,4'-trihydroxybenzophenone (T) prepared in Example 1; Figure 4 : FTIR spectra of 2,4,4'-trihydroxybenzophenone / aniline (Ta), 2,4,4'-trihydroxybenzophenone / furfurylamine (Tf), and 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene (Tm) type benzoxazine prepared in Example 2; Figure 5 Dynamic thermomechanical analysis (DMA) spectra of the 2,4,4'-trihydroxybenzophenone / aniline (poly(Ta)), 2,4,4'-trihydroxybenzophenone / furfurylamine (poly(Tf)), and 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene (poly(Tm)) type benzoxazine resins prepared in Example 8; Figure 6 Micro-combustion calorimetry (MCC) spectra of the 2,4,4'-trihydroxybenzophenone / aniline (poly(Ta)), 2,4,4'-trihydroxybenzophenone / furfurylamine (poly(Tf)), and 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene (poly(Tm)) type benzoxazine resins prepared in Example 8. Detailed Implementation
[0033] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
[0034] Example 1 Preparation of 2,4,4'-trihydroxybenzophenone: Resorcinol, p-hydroxybenzoic acid, and 4 mL of boron trifluoride diethyl ether solution were added to a reaction vessel containing high-boiling-range petroleum ether. The molar ratio of resorcinol to p-hydroxybenzoic acid was 1:0.9. The reaction was carried out at 100°C for 2 h. After the reaction was completed, the reaction solution was poured into cold distilled water to wash and neutralize the residual catalyst. The solution was then centrifuged, filtered, and dried to obtain a yellow powder of 2,4,4'-trihydroxybenzophenone.
[0035] like Figure 1 The image shown is the infrared spectrum of 2,4,4'-trihydroxybenzophenone prepared in this embodiment, at 3368 cm⁻¹. -1 The characteristic absorption peak representing the phenolic hydroxyl group -OH is at 1602 cm⁻¹. -1 The characteristic absorption peak representing C=O is at 3026 cm⁻¹. -1 The peak at 2895 cm⁻¹ represents the stretching vibration of CH on the benzene ring. -1 The peak at this location represents the stretching vibration of -CH2. Figure 2 Nuclear magnetic resonance (NMR) of 2,4,4'-trihydroxybenzophenone (T) prepared in this embodiment. 1 H-NMR (a) and 13 C-NMR (b) spectrum, as shown Figure 2 As shown, the hydrogen and carbon atoms of the 2,4,4'-trihydroxybenzophenone prepared in this embodiment correspond one-to-one with the spectrum. Figure 3The mass spectrometry (MS) spectrum of 2,4,4'-trihydroxybenzophenone (T) prepared in Example 1 is shown below. Figure 3 As shown, a characteristic peak of 2,4,4'-trihydroxybenzophenone (T) was observed at 233 nm, with no impurity peaks, indicating a very pure chemical structure and few impurities. In summary, this embodiment demonstrates the successful synthesis of the product 2,4,4'-trihydroxybenzophenone.
[0036] Example 2 Preparation of trifunctional benzoxazine monomers: 4.60 g (0.02 mol) of 2,4,4'-trihydroxybenzophenone prepared in Example 1, along with a monoamine (5.58 g (0.06 mol) aniline, 5.82 g (0.06 mol) furfurylamine, or 7.02 g (0.06 mol) m-aminophenylacetylene) and 3.60 g (0.12 mol) paraformaldehyde, were added to a 250 mL three-necked flask equipped with a condenser, magnetic stirrer, and thermometer. The molar ratio of phenolic hydroxyl, amino, and aldehyde functional groups was 1:1:2. Then, 75 mL of tetrahydrofuran solvent was added, followed by acetic acid, with the mass of acetic acid being 5% of the total mass of the reactants. After thorough mixing, the mixture was heated to 65 °C under a nitrogen atmosphere and reacted for 130 h. After the reaction was completed, the reaction solution was poured into 100 mL of methanol solution to precipitate, resulting in a milky white suspension. After standing for 12 hours, the supernatant was removed to obtain a brown precipitate. The brown precipitate was then vacuum-dried at 60 °C for 8 hours. Finally, the dried product was ground to obtain a brown powder, which consisted of three trifunctional benzoxazine monomers: 2,4,4'-trihydroxybenzophenone / aniline (Ta), 2,4,4'-trihydroxybenzophenone / furfurylamine (Tf), and 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene (Tm) type benzoxazine monomers, with oxazine ring formation rates of 97%, 96%, and 95%, and yields of 93%, 91%, and 90%, respectively. Figure 4 The image shows the infrared spectra of the three trifunctional benzoxazine monomers prepared in this embodiment, at 928 cm⁻¹. -1 The characteristic absorption peaks of the oxazine ring are at 1242 and 1168 cm⁻¹. -1 These are the characteristic absorption peaks of COC and CNC on the oxazine ring, respectively, at 1601 cm⁻¹. -1 The peak corresponds to the stretching vibration of C=O. These results indicate that the synthesized product in this embodiment is a trifunctional benzoxazine monomer containing a carbonyl group, and its molecular structure is shown in Formula 1.
[0037] Example 3 Preparation of trifunctional benzoxazine monomers: 23.0 g (0.1 mol) of 2,4,4'-trihydroxybenzophenone prepared in Example 1, along with monoamines (27.9 g (0.3 mol) aniline, 29.1 g (0.3 mol) furfurylamine, 35.1 g (0.3 mol) m-aminophenylacetylene), and 18.0 g (0.6 mol) paraformaldehyde, were added to a 250 mL three-necked flask equipped with a condenser, magnetic stirrer, and thermometer. The molar ratio of phenolic hydroxyl, amino, and aldehyde functional groups was 1:1:2. Then, 150 mL of toluene solvent was added, followed by acetic acid, with the mass of acetic acid being 15% of the total mass of the reactants. After thorough mixing, the mixture was heated to 115 °C under a nitrogen atmosphere and reacted for 8 h. After the reaction was completed, the reaction solution was poured into 200 mL of methanol solution to precipitate, resulting in a milky white suspension. After standing for 12 h, the supernatant was removed to obtain a brown precipitate. The brown precipitate was then vacuum dried at 80 °C for 8 h. Finally, the dried product was ground to obtain a brown powder, which consisted of three trifunctional benzoxazine monomers, Ta, Tf, and Tm, with cyclocyclization rates of 99%, 98%, and 98%, and yields of 97%, 96%, and 93%, respectively.
[0038] Example 4 Preparation of trifunctional benzoxazine monomers: 4.60 g (0.02 mol) of 2,4,4'-trihydroxybenzophenone prepared in Example 1, along with a monoamine (5.58 g (0.06 mol) aniline, 5.82 g (0.06 mol) furfurylamine, and 7.02 g (0.06 mol) m-aminophenylacetylene), and 3.60 g (0.12 mol) formaldehyde, with a molar ratio of phenolic hydroxyl, amino, and aldehyde functional groups of 1:1:2, were added to a 250 mL three-necked flask equipped with a condenser, magnetic stirrer, and thermometer. Then, 75 mL of a toluene / ethanol mixed solvent (toluene to ethanol volume ratio of 1:1) was added, followed by acetic acid, with the acetic acid mass being 10% of the total reactant mass. After thorough mixing, the mixture was heated to 80 °C under a nitrogen atmosphere and reacted for 10 h. Then, 2,4,4'-trihydroxybenzophenone was added, and the reaction continued for another 120 h. Finally, the reaction solution was poured into 100 mL of methanol solution to precipitate, resulting in a milky white suspension. After standing for 12 h, the supernatant was removed to obtain a brown precipitate. The brown precipitate was then vacuum dried at 60 °C for 8 h. Finally, the dried product was ground to obtain a brown powder, which consists of three trifunctional benzoxazine monomers, Ta, Tf, and Tm, with oxazine ring formation rates of 98%, 97%, and 96%, respectively, and yields of 96%, 96%, and 94%, respectively.
[0039] Example 5 Preparation of trifunctional benzoxazine monomers: 23.0 g (0.1 mol) of 2,4,4'-trihydroxybenzophenone prepared in Example 1, along with a monoamine (27.9 g (0.3 mol) aniline, 29.1 g (0.3 mol) furfurylamine, 35.1 g (0.3 mol) m-aminophenylacetylene), and 18.0 g (0.6 mol) paraformaldehyde, with a molar ratio of phenolic hydroxyl, amino, and aldehyde functional groups of 1:1:2, were added to a 250 mL three-necked flask equipped with a condenser, magnetic stirrer, and thermometer. Then, 150 mL of N,N-dimethylformamide solvent was added, followed by acetic acid, with the acetic acid mass being 12% of the total reactant mass. After thorough mixing, the mixture was heated to 100 °C for 6 h under a nitrogen atmosphere, and then 2,4,4'-trihydroxybenzophenone was added to continue the reaction for another 2 h. Finally, the reaction solution was poured into 200 mL of methanol solution to precipitate, resulting in a milky white suspension. After standing for 12 h, the supernatant was removed to obtain a brown precipitate. The brown precipitate was then vacuum dried at 120 °C for 8 h. Finally, the dried product was ground to obtain a brown powder, which consists of three trifunctional benzoxazine monomers, Ta, Tf, and Tm, with cyclocyclization rates of 99%, 98%, and 97%, and yields of 96%, 95%, and 93%, respectively.
[0040] Example 6 Preparation of trifunctional benzoxazine nitrogen-rich resin: The trifunctional benzoxazine monomer prepared in Example 2 was dissolved in tetrahydrofuran solvent, and then melamine was added. The mass ratio of melamine to benzoxazine monomer was 1:20. After mixing evenly, the mixture was poured into a polytetrafluoroethylene curing mold and placed in a vacuum drying oven at 80°C for 8 hours. Then, it was cured at 100°C, 120°C, 140°C, 160°C, and 180°C for 1 hour to obtain three types of trifunctional benzoxazine nitrogen-rich resins. The glass transition temperatures (DMA) of the trifunctional benzoxazine nitrogen-rich resins of 2,4,4'-trihydroxybenzophenone / aniline, 2,4,4'-trihydroxybenzophenone / furfurylamide, and 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene are 300℃, 370℃, and 400℃, respectively. The char residues (TGA) at 800℃ can reach 55%, 65%, and 70%, respectively. The limiting oxygen index (GB 2406-80) is as low as 39.5, 43.5, and 44.5, respectively. The heat release capacity (MCC) is as low as 50 J g, respectively. -1 K -1 30J g -1 K -1 20J g -1 K -1 All flame retardant properties are rated V-0 (UL-94).
[0041] Example 7 Preparation of trifunctional benzoxazine nitrogen-rich resin: The trifunctional benzoxazine monomer prepared in Example 3 was dissolved in toluene solvent, and then melamine was added. The mass ratio of melamine to benzoxazine monomer was 1:10. After mixing evenly, the mixture was poured into a polytetrafluoroethylene curing mold and placed in a hot press. The mold was heated at 180°C for 1 hour and hot-pressed. The pressure was released and the air was vented once every 15 minutes in between to prepare three types of trifunctional benzoxazine nitrogen-rich resins. The glass transition temperatures (DMA) of the trifunctional benzoxazine nitrogen-rich resins of 2,4,4'-trihydroxybenzophenone / aniline, 2,4,4'-trihydroxybenzophenone / furfurylamide, and 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene are 310℃, 380℃, and 410℃, respectively. The char residues (TGA) at 800℃ can reach 60%, 68%, and 75%, respectively. The limiting oxygen index (GB 2406-80) is as low as 41.5, 44.7, and 45.5, respectively. The heat release capacity (MCC) reaches 45 J g, respectively. -1 K -1 37J g -1 K -1 24J g -1 K -1 All flame retardant properties are rated V-0 (UL-94).
[0042] Example 8 Preparation of trifunctional benzoxazine nitrogen-rich resin: The trifunctional benzoxazine monomer prepared in Example 4 was dissolved in 1,4-dioxane solvent, and then melamine was added. The mass ratio of melamine to benzoxazine monomer was 1:50. After mixing evenly, the mixture was poured into a polytetrafluoroethylene curing mold and placed in a vacuum drying oven at 80°C for 8 hours. Then, it was cured at 100°C, 120°C, 140°C, 160°C, and 180°C for 2 hours each to obtain three types of trifunctional benzoxazine nitrogen-rich resins. The glass transition temperatures (DMA) of the 2,4,4'-trihydroxybenzophenone / aniline, 2,4,4'-trihydroxybenzophenone / furfurylamide, and 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene type trifunctional benzoxazine nitrogen-rich resins were 283°C, 357°C, and 390°C, respectively. Figure 5 The residual char rate at 800℃ (TGA) can reach 53%, 64%, and 68%, respectively; the limiting oxygen index (GB 2406-80) can reach 38.7, 43.1, and 44.7, respectively; and the heat release capacity (MCC) can reach 46 J / g. -1 K -1 40J g -1 K -1 38J g -1 K-1 And the peak temperature with the highest heat release rate (T) PHRR The temperatures reached 446℃, 476℃, and 481℃ respectively. Figure 6 All of them have a flame retardant rating of V-0 (UL-94).
[0043] Example 9 Preparation of trifunctional benzoxazine nitrogen-rich resin: The trifunctional benzoxazine monomer prepared in Example 5 was dissolved in xylene solvent, and then melamine was added. The mass ratio of melamine to benzoxazine monomer was 1:100. After mixing evenly, the mixture was poured into a polytetrafluoroethylene curing mold and placed in a hot press. The mold was heated at 80°C for 4 hours and hot-pressed. The pressure was released and the air was vented once every 15 minutes in between to obtain three types of trifunctional benzoxazine nitrogen-rich resins. The glass transition temperatures (DMA) of the trifunctional benzoxazine nitrogen-rich resins of 2,4,4'-trihydroxybenzophenone / aniline, 2,4,4'-trihydroxybenzophenone / furfurylamide, and 2,4,4'-trihydroxybenzophenone / m-aminophenylacetylene are 280℃, 350℃, and 390℃, respectively. The char residues (TGA) at 800℃ can reach 50%, 55%, and 60%, respectively. The limiting oxygen index (GB 2406-80) can reach 37.5, 39.5, and 41.5, respectively. The heat release capacity (MCC) reaches 70 J g, respectively. -1 K -1 50J g -1 K -1 40J g -1 K -1 All flame retardant properties are rated V-0 (UL-94).
[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A halogen-free, phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomer, characterized in that: For any of the benzoxazine monomers shown in Formula 1: or or Formula 1.
2. The method for preparing the halogen-free, phosphorus-free intrinsically flame-retardant trifunctional benzoxazine monomer according to claim 1, characterized in that: Includes the following steps: 2,4,4'-Trihydroxybenzophenone, a monoamine, and an aldehyde compound are mixed in an organic solvent, wherein the monoamine is aniline, furfurylamine, or m-aminophenylacetylene. The pH is then adjusted to 2.5-3.5 with acid, and the mixture is reacted at 65-115°C for 8-130 hours under a nitrogen atmosphere. The mixture is then filtered and purified to obtain the final product. The structural formula of 2,4,4'-Trihydroxybenzophenone is shown in Formula 2. Equation 2.
3. The preparation method according to claim 2, characterized in that: The molar ratio of phenolic hydroxyl, amino, and aldehyde functional groups in 2,4,4'-trihydroxybenzophenone, monoamines, and aldehydes is 1:1:
2.
4. The preparation method according to claim 2, characterized in that: The acid used for pH adjustment is acetic acid, and the mass of acetic acid is 5% to 15% of the total mass of the reactants.
5. The preparation method according to claim 2, characterized in that: Aldehydes and monoamines are added to an organic solvent, and after adjusting the pH range with acid, they are reacted at 65-115°C for 6-10 hours under a nitrogen atmosphere. Then, 2,4,4'-trihydroxybenzophenone is added, and the reaction is continued at 65-115°C for 2-120 hours.
6. The preparation method according to claim 2, characterized in that: The aldehyde compound is formaldehyde or paraformaldehyde; The organic solvent used in the preparation of benzoxazine monomers is any one or a mixture of toluene, xylene, ethanol, chloroform, N,N-dimethylformamide, 1,4-dioxane, and tetrahydrofuran. The purification process involves pouring the reaction solution into a methanol solution to precipitate the mixture, resulting in a milky white suspension. After standing, the supernatant is removed to obtain a brown precipitate. The brown precipitate is then dried and ground to obtain the benzoxazine monomer.
7. The preparation method according to claim 2, characterized in that: The preparation method of 2,4,4'-trihydroxybenzophenone is as follows: resorcinol and p-hydroxybenzoic acid are in a ratio of 1-1.3:0.9, boron trifluoride diethyl ether is used as a catalyst, high-boiling-range petroleum ether is used as a reaction solvent, the reaction temperature is 90-120℃, the reaction time is 2-6 h, after the reaction is completed, the mixture is cooled to room temperature, washed with cold distilled water to neutralize the residual catalyst, centrifuged, filtered and dried to obtain 2,4,4'-trihydroxybenzophenone yellow powder. The reaction equation is as follows: 。 8. A halogen-free, phosphorus-free, intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin, characterized in that: It is prepared by curing any of the benzoxazine monomers shown in Formula 1 of claim 1 in the presence of melamine.
9. The halogen-free, phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin according to claim 8, characterized in that: The mass ratio of melamine to benzoxazine monomer is 1:100 to 1:
10.
10. The preparation method of the halogen-free, phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin according to claim 8, comprising the following steps: The benzoxazine monomer is dissolved in an organic solvent, and melamine is added. The mass ratio of melamine to benzoxazine monomer is 1:100 to 1:
10. After mixing evenly, the mixture is cured at 80 to 180°C for 1 to 10 hours to obtain a halogen-free, phosphorus-free intrinsically flame-retardant trifunctional benzoxazine nitrogen-rich resin.