A pt-fa based flame retardant bio-based copolymer resin and a method of making the same

Abstract

The application discloses a kind of flame-retardant bio-based copolymer resin based on PT-fa, to obtain mixed resin with bio-based benzoxazine monomer PT-fa and bisphenol A-aniline type benzoxazine BA-a as raw material, then, mixed resin is heat cured to obtain flame-retardant bio-based copolymer resin Poly (PT-fa / BA-a) based on PT-fa, the obtained copolymer resin has high thermal stability and high flame retardant performance;The PT-fa is prepared by solvent-free synthesis method with hydroxyl tyrosol, furfurylamine and polyformaldehyde as raw material, the obtained monomer has high purity.The glass transition temperature T g of the Poly (PT-fa / BA-a) is 180-300 DEG C;The temperature T di of 5% thermal weight loss under nitrogen atmosphere is 328-340 DEG C, the carbon residue rate Y c at 800 DEG C is 38-60%;Heat release capacity HRC is 80-175 J / g·K, and the total heat release THR is 10-21 kJ / g.The preparation method comprises the following steps: 1, the preparation of bio-based benzoxazine monomer PT-fa;2, the preparation of flame-retardant bio-based copolymer resin based on PT-fa.

Description

Technical Field

[0001] The present invention relates to the technical field of functional polymer materials, and in particular to a flame-retardant bio-based copolymer resin based on PT-fa and a preparation method thereof. Background Art

[0002] Benzoxazines are widely used in fields such as electronic packaging and aerospace due to their advantages, such as strong molecular designability, excellent heat resistance and flame retardancy, and good dielectric properties. Among them, bisphenol A-aniline benzoxazine BA-a has become the most commercially successful benzoxazine due to its simple synthesis process and low cost. However, BA-a suffers from poor heat resistance and flame retardancy.

[0003] The conventional method for solving the problem of heat resistance and flame retardancy of BA-a is to copolymerize BA-a resin with other high-performance benzoxazine resins to achieve modification. This type of method also has the advantage that while improving the performance of the copolymerized resin, there is no compatibility problem. For example, existing document 1 (Wang T, Wang Z, Pan ZC, et al. Synthesis of novel allylamine-fluorene based benzoxazine and its copolymerization with typical benzoxazine: Curing behavior and thermal properties [J]. New Journal of Chemistry. 2024-10-12) copolymerizes BA-a with a fluorenyl-containing benzoxazine monomer, significantly improving the heat resistance of the copolymerized resin (Tg increased by 15 ° C, Tdi increased by 12.7%). However, the technical problem with this technical solution is that the synthetic raw materials of the fluorenyl benzoxazine monomer come from fossil resources, which does not meet the requirements of green and environmental protection.

[0004] However, there are no reports on the solvent-free synthesis of benzoxazine copolymerized with BA-a from biomass raw materials. For example, in the existing document 2 ([1] Shitong, Ren, Xiangyan, et al. A fully bio-based benzoxazine as latent catalyst for bisphenol A / aniline-based benzoxazine - Science Direct [J]. Materials Today Communications, 20(C): 100568-100568.2024-10-13), although biomass raw materials were used to synthesize benzoxazine monomers, the solvent used in this technical solution was ethyl acetate.

[0005] The advantages of solvent-free methods include energy conservation, environmental friendliness, and environmental protection. However, they have not yet been realized because they require both the raw materials and the products to have low melting points. However, the benzoxazine resins currently available for this application all have highly rigid structures, resulting in high melting points for both the raw materials and monomers used, making them impractical for solvent-free synthesis. For example, existing document 3 (An apigenin-based bio-benzoxazine with three polymerizable functionalities: sustainable synthesis, thermal latent polymerization, and excellent thermal properties of its thermosets, Polymer Chemistry, 2020, 11, 5800-5809) uses apigenin and furfural amine as the main raw materials to synthesize an all-biomass benzoxazine monomer. The initial thermal decomposition temperature Tdi of the cured resin is 384°C, the heat release capacity HRC is 20.2 J / g·K, and the total heat release THR is 9.4 kJ / g. The molecules used in this technical method have a highly rigid structure, and the melting point of its monomer is as high as 174°C. This property determines that the monomer cannot be prepared by a solvent-free synthesis method. This technical solution adopts a solvent method for preparation, specifically using toluene as the reaction medium.

[0006] Therefore, the problem existing in this technical solution is that toxic solvents are used as raw materials on the surface. In addition to causing environmental pollution problems under high temperature reaction conditions, toxic solvents are also present in residual materials, affecting subsequent application ranges. Therefore, it can be confirmed that the fundamental problem of this type of technical solution is: due to the basic properties of its monomers, it is impossible to adopt a solvent-free method to prepare it, thereby unable to meet the requirements of environmental protection. For example, existing document 4 (Smart and sustainable design of latent catalyst-containing benzoxazine-bio-resins and application studies) is copolymerized with BA-a using a solvent-free method blending method with high melting point green benzoxazine. Although this technical solution has adopted a solvent-free method blending method, due to the presence of solid-liquid blending, there is a phenomenon of uneven mixing, thereby affecting the stability of the obtained resin.

[0007] In order to solve the above-mentioned solid-liquid blending problem, it is necessary to use a green benzoxazine with a low melting point and copolymerize it with BA-a to prepare a resin to overcome it. Therefore, the applicant of the present invention used hydroxytyrosol and furfurylamine as raw materials and synthesized a new low-melting-point benzoxazine PT-fa through a solvent-free method. Moreover, the cured resin Poly(PT-fa) has high heat resistance and high flame retardancy - the heat release capacity HRC is 21.3J / g·K and the total heat release THR is 2.9kJ / g. That is, the tests have shown that the HRC and THR of Poly(PT-fa) are lower than the HRC and THR values ​​of the cured resin of the existing all-bio-based benzoxazine synthesized by the solvent-free method, and has excellent flame retardant properties. However, during the research process, the applicant found that when PT-fa is used alone for the curing reaction, due to the violent curing reaction process, a large number of pores appear in the cured resin, that is, the technical solution has a technical problem that it cannot be molded, that is, PT-fa cannot be used alone. Summary of the Invention

[0008] In view of the deficiencies in the prior art, the present invention provides a flame retardant bio-based copolymer resin based on PT-fa and a preparation method thereof.

[0009] The basic principle of this method is to first prepare the low-melting-point bio-based benzoxazine monomer PT-fa using hydroxytyrosol, furfurylamine, and paraformaldehyde as raw materials. This low-melting-point benzoxazine monomer enables a smooth solvent-free synthesis and more uniform mixing with the BA-a resin, thereby ensuring the performance stability of the copolymer resin. PT-fa and BA-a are then blended in a solvent-free manner and further thermally polymerized to obtain the copolymer resin. This method not only significantly improves the heat resistance and flame retardancy of the BA-a resin but also solves the problem of PT-fa being unable to form.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A flame-retardant bio-based copolymer resin based on PT-fa is prepared by using a bio-based benzoxazine monomer PT-fa and bisphenol A-aniline benzoxazine BA-a as raw materials to obtain a mixed resin. The mixed resin is then thermally cured to obtain a flame-retardant bio-based copolymer resin based on PT-fa, Poly(PT-fa / BA-a). The obtained copolymer resin has high thermal stability and high flame retardancy.

[0012] The PT-fa is prepared using hydroxytyrosol, furfurylamine and paraformaldehyde as raw materials through a solvent-free synthesis method, and the obtained monomer has high purity;

[0013] The glass transition temperature T of the Poly (PT-fa / BA-a) g 180-300℃;

[0014] The temperature T when the Poly (PT-fa / BA-a) loses 5% of its weight under nitrogen atmosphere di The carbon residue rate Y at 328-340℃ and 800℃ c 38-60%;

[0015] The heat release capacity HRC of the Poly (PT-fa / BA-a) is 80-175 J / g·K, and the total heat release THR is 10-21 kJ / g.

[0016] 5. A method for preparing a flame-retardant bio-based copolymer resin based on PT-fa, comprising the following steps:

[0017] Step 1, preparation of the bio-based benzoxazine monomer PT-fa, comprising mixing hydroxytyrosol, furfurylamine, and paraformaldehyde in a certain molar ratio, and conducting a Mannich condensation reaction under certain conditions by a solvent-free method. After completion of the reaction, the mixture is recrystallized and dried to obtain the bio-based benzoxazine monomer, referred to as PT-fa.

[0018] In the step 1, the molar ratio of hydroxytyrosol, furfurylamine and paraformaldehyde is 1:2:4;

[0019] In step 1, the conditions for the Mannich condensation reaction are: in an oil bath with stirring, the reaction temperature is 110° C., and the reaction time is 6 h;

[0020] In the step 1, the recrystallization operation is carried out in ethanol;

[0021] Step 2, preparation of a flame-retardant bio-based copolymer resin based on PT-fa. First, under certain conditions, the PT-fa obtained in step 1 and bisphenol A-aniline benzoxazine BA-a are completely melted to obtain a mixed resin. Then, the molten mixed resin is placed in a mold. Finally, the mixed resin is cured to obtain a flame-retardant bio-based copolymer resin based on PT-fa, referred to as Poly(PT-fa / BA-a).

[0022] In step 2, the mass ratio of PT-fa to BA-a is 2:(3-38); the conditions for completely melting PT-fa and BA-a to obtain a mixed resin are: under stirring conditions, heating temperature is 115-140° C., and heating time is 5-30 minutes;

[0023] In step 2, the curing conditions are divided into 4 stages:

[0024] Stage 1: curing temperature is 180°C and curing time is 1h;

[0025] Stage 2: curing temperature is 200°C and curing time is 1h;

[0026] Stage 3: curing temperature is 220°C and curing time is 1h;

[0027] Stage 4 is a curing temperature of 240°C and a curing time of 2 hours.

[0028] The technical effects of the present invention can be seen from the following tests:

[0029] The HRMS test results show that the mass-to-charge ratio is 397.1740, which is consistent with [C 22 H 25 N2O5] + The difference from the theoretical value of the mass-to-charge ratio of 397.1764 is negligible. The test results show that PT-fa was successfully synthesized.

[0030] FTIR analysis revealed that PT-fa contained characteristic peaks for CN, COC, oxazine rings, ethylene in the ethanol group, and hydroxyl groups. These results confirmed the successful synthesis of PT-fa.

[0031] go through1 HNMR test results show that PT-fa contains characteristic hydrogen spectrum of methylene on furan ring, benzene ring, oxazine ring, methylene connecting furan ring and ethylene, and no obvious impurity peak. The test results show that PT-fa is successfully synthesized, and has high purity.

[0032] After 13 CNMR test results show that PT-fa contains characteristic carbon spectrum of methylene on oxazine ring, methylene connecting furan ring and ethylene. The test results show that PT-fa is successfully synthesized.

[0033] After DSC test results show that the curing exothermic peak of PT-fa is narrow and sharp, and its curing reaction is violent, which directly leads to local temperature too high, thereby causing sample decomposition and bubble generation. The curing exothermic peak of (PT-fa / BA-a)-40 is wide and low, and copolymerization of PT-fa and BA-a can effectively avoid the problem of sample decomposition caused by local temperature too high due to violent curing reaction.

[0034] After macroscopic morphology test results show that Poly(PT-fa) resin contains a large amount of bubbles and cannot be formed, that is, it does not have formability, and Poly(PT-fa / BA-a)-40 is a black solid with toughness and no bubbles, that is, it has formability.

[0035] After FTIR test results show that the characteristic peaks of C-N, C-O-C and oxazine ring disappear, and the test results show that

[0036] (PT-fa / BA-a)-40 undergoes ring-opening crosslinking reaction to form cured resin Poly(PT-fa / BA-a)-40.

[0037] After TGA test results show that the temperature T di of Poly(PT-fa / BA-a)-40 is 338℃ at 5% thermal weight loss under nitrogen atmosphere, and the carbon residue rate Y c of 800℃ is 49.9%. The test results show that Poly(PT-fa / BA-a)-40 has good thermal stability.

[0038] After DMA test results show that the glass transition temperature T g of Poly(PT-fa / BA-a)-40 is 242.1℃. The test results show that Poly(PT-fa / BA-a)-40 has good heat resistance.

[0039] MCC testing results show that Poly(PT-fa / BA-a)-40 has a heat release capacity (HRC) of 110.8 J / g·K and a total heat release rate (THR) of 13.9 kJ / g. These test results demonstrate that Poly(PT-fa / BA-a)-40 exhibits excellent flame retardancy.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] 1. The present invention uses biomass (hydroxytyrosol, furfurylamine) as the main raw materials, and synthesizes and purifies bio-based benzoxazine monomer (PT-fa) without solvent or in the green solvent ethanol. The PT-fa synthesized in the present invention has excellent processability and a melting point (Tm) of 113.8°C;

[0042] 2. The benzoxazine resin (poly(PT-fa)) prepared by the present invention has a Tdi of 326°C, a carbon residue (Yc) of 65.8% at 800°C, an HRC of 21.3 J / g·K, and a THR of 2.9 kJ / g. Both HRC and THR values ​​are lower than those of all bio-based benzoxazine cured resins synthesized by solvent-free methods. Poly(PT-fa) not only has good thermal stability but also excellent flame retardancy.

[0043] 3. The present invention utilizes the low melting point of PT-fa and blends it with a commercial benzoxazine monomer (BA-a) in a molten state to prepare a copolymer resin Poly(PT-fa / BA-a). The copolymer resin overcomes the defect that poly(PT-fa) cannot be molded;

[0044] 4. When the PT-fa content of the copolymer resin of the present invention is 40%, that is, Poly(PT-fa / BA-a)-40, its Tg, Tdi and Tg, Tdi and Yc are increased by 78.6°C, 10°C and 11.8% respectively compared with the commercial resin; HRC and THR are reduced by 33% and 35% respectively; the addition of PT-fa significantly improves the heat resistance and flame retardancy of the commercial resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is the synthetic reaction formula and chemical structure of the bio-based benzoxazine monomer (PT-fa) in Example 1 of the present invention;

[0046] Figure 2 is the Fourier transform infrared (FTIR) spectrum of PT-fa in Example 1 of the present invention;

[0047] Figure 3 is the hydrogen nuclear magnetic resonance (1H NMR) spectrum of PT-fa in Example 1 of the present invention;

[0048] Figure 4 is the carbon nuclear magnetic resonance (13C NMR) spectrum of PT-fa in Example 1 of the present invention;

[0049] Figure 5 is the high resolution mass spectrometry (HRMS) of PT-fa in Example 1 of the present invention;

[0050] Figure 6 The differential scanning calorimetry (DSC) curves of (PT-fa / BA-a)-40, PT-fa, BA-a, and (PT-fa / BA-a)-20 in Example 1, Comparative Example 1, Comparative Example 2, and Example 2 of the present invention are shown;

[0051] Figure 7 Macroscopic morphology photos of Poly(PT-fa / BA-a)-40, Poly(BA-a), and Poly(PT-fa / BA-a)-20 in Example 1, Comparative Example 2, and Example 2 of the present invention

[0052] Figure 8 The FTIR spectra of Poly(PT-fa / BA-a)-40 and Poly(PT-fa / BA-a)-20 in Examples 1 and 2 of the present invention are as follows:

[0053] Figure 9 The thermogravimetric analysis (TGA) curves of Poly(PT-fa / BA-a)-40, Poly(BA-a), and Poly(PT-fa / BA-a)-20 in Example 1, Comparative Example 2, and Example 2 of the present invention are shown;

[0054] Figure 10 Dynamic mechanical analysis (DMA) curves of Poly(PT-fa / BA-a)-40, Poly(BA-a), and Poly(PT-fa / BA-a)-20 in Example 1, Comparative Example 2, and Example 2 of the present invention;

[0055] Figure 11 Heat release rate (HRR)-temperature curves of the bio-based benzoxazine Poly(PT-fa / BA-a)-40, Poly(BA-a), and Poly(PT-fa / BA-a)-20 in the micro combustion calorimetry (MCC) test of Example 1, Comparative Example 2, and Example 2 of the present invention;

[0056] Figure 12 This is a macroscopic morphology photograph of Poly(PT-fa) in Comparative Example 1 of the present invention;

[0057] Figure 13 is the TGA curve of Poly(PT-fa) in Comparative Example 1 of the present invention;

[0058] Figure 14 This is the HRR-temperature curve of the MCC test of the bio-based benzoxazine Poly (PT-fa) in Comparative Example 1 of the present invention;

[0059] Figure 15 This is the HRR-temperature curve of the MCC test of the bio-based benzoxazine Poly(PT-fa / BA-a)-10 in Example 3 of the present invention;

[0060] Figure 16 This is the HRR-temperature curve of the bio-based benzoxazine Poly(PT-fa / BA-a)-5 in the MCC test in Example 4 of the present invention. DETAILED DESCRIPTION

[0061] The present invention is further described in detail through embodiments and in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0062] Example 1

[0063] A method for preparing a flame-retardant bio-based copolymer resin based on PT-fa comprises the following steps:

[0064] Step 1, preparation of the bio-based benzoxazine monomer PT-fa, with the molar ratio of hydroxytyrosol, furfurylamine and paraformaldehyde being 1:2:4, 10.962g of hydroxytyrosol, 13.809g of furfurylamine and 8.542g of paraformaldehyde are mixed, i.e., the total mass of the raw materials is 33.313g, and a Mannich condensation reaction is carried out in an oil bath with stirring at a reaction temperature of 110°C and a reaction time of 6h using a solvent-free method. After completion of the reaction, the bio-based benzoxazine monomer, referred to as PT-fa, is obtained after recrystallization and drying;

[0065] The recrystallization operation is carried out in ethanol.

[0066] In order to prove the successful synthesis of PT-fa, HRMS test was performed. Figure 1 As shown, the measured value of the mass-to-charge ratio is 397.1740, which is consistent with [C 22 H 25 N2O5] + The difference from the theoretical value of the mass-to-charge ratio of 397.1764 is negligible. The test results show that PT-fa was successfully synthesized.

[0067] In order to further prove the successful synthesis of PT-fa and confirm the composition of PT-fa, FTIR test was performed. The test results are as follows Figure 2 As shown in the figure, PT-fa contains characteristic peaks of CN, COC, oxazine ring, ethylene in ethanol group, and hydroxyl group. The test results show that PT-fa was successfully synthesized.

[0068] In order to further prove the successful synthesis and purity of PT-fa, 1 H NMR testing and 13 C NMR test.

[0069] 1 The results of H NMR tests are as follows Figure 3 As shown, PT-fa contains characteristic H-H peaks for the furan ring, the benzene ring, the methylene group on the oxazine ring, and the methylene group connecting the furan ring and the ethylene group, with no other significant impurity peaks. These results demonstrate that PT-fa was successfully synthesized and of high purity.

[0070] 13 C NMR test results are as follows Figure 4 As shown, PT-fa contains characteristic carbon atoms of the methylene group on the oxazine ring, the methylene group connected to the furan ring, and the ethylene group. These test results indicate that PT-fa was successfully synthesized.

[0071] To verify the yield of PT-fa, the mass of PT-fa obtained in step 1 was weighed. The mass of PT-fa was 28.019 g, and calculation showed that the yield of PT-fa was 84.1%.

[0072] The bio-based benzoxazine monomer PT-fa was synthesized for the first time and there is no existing synthetic reaction formula. According to the above HRMS test, FTIR test and NMR test, it can be confirmed that the synthetic reaction formula of PT-fa is as follows: Figure 5 As shown, PT-fa was synthesized by a solvent-free Mannich condensation reaction using hydroxytyrosol, furfurylamine and paraformaldehyde as reactants under heating conditions.

[0073] Since PT-fa was synthesized for the first time and there is no existing thermal performance data, DSC test was performed to prove the thermal performance of PT-fa, i.e. its processing performance. Figure 6 As shown in Figure 2, the melting point of PT-fa is 113.8°C, and the peak curing temperature is 224.9°C. The test results show that PT-fa has a low melting point and curing temperature, which directly leads to the solvent-free synthesis method of PT-fa, that is, PT-fa has excellent processing properties.

[0074] Step 2, preparation of a flame-retardant bio-based copolymer resin based on PT-fa. First, under stirring conditions, 5.713 g of PT-fa obtained in step 1 and 8.570 g of bisphenol A-aniline benzoxazine BA-a are completely melted at a heating temperature of 130° C. for 10 minutes to obtain a mixed resin. Then, the molten mixed resin is placed in a mold. Finally, the mixed resin is cured to obtain a flame-retardant bio-based copolymer resin based on PT-fa, referred to as Poly(PT-fa / BA-a). In the specific embodiment 1, the amount of PT-fa added to the copolymer resin obtained is 40 wt.%, so it is referred to as Poly(PT-fa / BA-a)-40.

[0075] The curing is divided into 4 stages,

[0076] Stage 1: curing temperature is 180°C and curing time is 1h;

[0077] Stage 2: curing temperature is 200°C and curing time is 1h;

[0078] Stage 3: curing temperature is 220°C and curing time is 1h;

[0079] Stage 4 is a curing temperature of 240°C and a curing time of 2 hours.

[0080] In order to prove that Poly(PT-fa / BA-a)-40 has the properties of formability, DSC test was carried out. The test results are as follows Figure 6 As shown, the curing exotherm peak of (PT-fa / BA-a)-40 is broad and short. These test results indicate that the curing reaction of PT-fa / BA-a)-40 is mild, effectively avoiding the problem of excessive local temperatures caused by a vigorous curing reaction, which can lead to sample decomposition.

[0081] Therefore, in order to further prove the molding performance of Poly(PT-fa / BA-a)-40, macromorphology test was carried out. Figure 7 As shown in the figure, Poly(PT-fa / BA-a)-40 is a tough black solid without bubbles, which means it has formability.

[0082] In order to prove the successful preparation of Poly(PT-fa / BA-a)-40, FTIR test was performed. The test results are as follows Figure 8 As shown in the figure, the characteristic peaks of CN, COC, and oxazine ring disappear, indicating that the oxazine ring undergoes a ring-opening crosslinking reaction to form the cured resin Poly(PT-fa / BA-a)-40.

[0083] In order to prove the thermal stability of Poly(PT-fa / BA-a)-40, thermal gravimetric analysis (TGA) was performed.Figure 9 As shown, the temperature T when Poly(PT-fa / BA-a)-40 loses 5 wt.% of weight under nitrogen atmosphere is di The carbon residue rate Y at 338℃ and 800℃ c The test results show that Poly(PT-fa / BA-a)-40 has good thermal stability.

[0084] In order to prove that Poly(PT-fa / BA-a)-40 has heat resistance, dynamic mechanical analysis (DMA) test was performed. The test results are as follows: Figure 10 As shown, the glass transition temperature T of Poly(PT-fa / BA-a)-40 g The test results show that Poly(PT-fa / BA-a)-40 has good heat resistance.

[0085] In order to prove that Poly(PT-fa / BA-a)-40 has flame retardant properties, micro combustion calorimetry MCC test was carried out. The test results are as follows Figure 11 As shown in the figure, the heat release capacity HRC of Poly(PT-fa / BA-a)-40 is 110.8J / g·K, and the total heat release THR is 13.9kJ / g. The test results show that Poly(PT-fa / BA-a)-40 has excellent flame retardant properties.

[0086] In order to further demonstrate the moldable properties of Poly (PT-fa / BA-a), Comparative Example 1 is provided, which is a bio-based benzoxazine resin cured with PT-fa alone, that is, to demonstrate the role of BA-a in the copolymer resin; at the same time, in order to demonstrate the role of PT-fa in the copolymer resin, Comparative Example 2 is provided, which is a bisphenol A-aniline type benzoxazine resin cured with BA-a alone.

[0087] It is noted that the bisphenol A-aniline benzoxazine resin Poly (BA-a) is a commercial resin, and its raw material, bisphenol A-aniline benzoxazine BA-a, is also prepared by a solvent-free method and is commercially available.

[0088] Comparative Example 1

[0089] A method for preparing a bio-based benzoxazine resin cured solely by PT-fa, wherein the steps not specifically described are the same as those in Example 1, except that in step 2, BA-a is not added, thereby obtaining a bio-based benzoxazine resin cured solely by PT-fa, referred to as Poly(PT-fa).

[0090] In order to prove the molding performance of Poly(PT-fa), DSC test was carried out. The test results are as follows Figure 6As shown in the figure, the curing exothermic peak of PT-fa is narrow and sharp. The test results show that the violent curing reaction of PT-fa directly leads to excessively high local temperature, which causes the sample to decompose and generate bubbles.

[0091] In order to further prove the molding performance of Poly(PT-fa), macromorphology test was carried out. The test results are as follows Figure 12 As shown, there are a lot of bubbles in the Poly(PT-fa) resin, which cannot be molded, that is, it does not have moldability.

[0092] In order to prove the thermal stability of Poly(PT-fa), TGA test was carried out. The test results are as follows Figure 13 As shown, the temperature T at which Poly(PT-fa) loses 5% of its weight under nitrogen atmosphere is di The carbon residue rate Y at 326℃ and 800℃ c The test results show that Poly(PT-fa) has good thermal stability.

[0093] In order to prove that Poly(PT-fa) has flame retardant properties, micro combustion calorimetry MCC test was carried out. The test results are as follows Figure 14 As shown, Poly(PT-fa) has a heat release capacity (HRC) of 21.3 J / g·K and a total heat release rate (THR) of 2.9 kJ / g. These test results demonstrate that both the HRC and THR of Poly(PT-fa) are lower than those of existing solvent-free synthesized, all-bio-based benzoxazine cured resins, demonstrating that Poly(PT-fa) possesses excellent flame retardant properties.

[0094] Compared with Example 1, it can be seen that although the T di It dropped by 12℃, c The flame retardant properties of Poly(PT-fa) are improved by 15.9%, the HRC is reduced by 89.5 J / g·K, and the THR is reduced by 11 kJ / g. In other words, the flame retardant properties of Poly(PT-fa) are better than those of Poly(PT-fa / BA-a)-40. However, since Poly(PT-fa) does not have formability, it cannot meet the requirements of practical applications. Therefore, only Poly(PT-fa / BA-a)-40 meets the practical requirements.

[0095] Comparative Example 2

[0096] A method for preparing a bisphenol A-aniline benzoxazine resin based on BA-a alone curing, wherein the steps not specifically described are the same as those in Example 1, except that step 1 is not required, and in step 2, PT-fa is not added, to obtain a bisphenol A-aniline benzoxazine resin, referred to as Poly(BA-a).

[0097] The DSC test results of BA-a are as follows Figure 1 As shown in the figure, the curing exothermic peak of BA-a is broad and short. The test results show that the curing reaction of BA-a is mild and the molding processability is good.

[0098] In order to prove the forming performance of Poly(BA-a), macromorphology test was carried out. The test results are as follows Figure 7 As shown, Poly(BA-a) is a tough black solid with no bubbles, indicating that it is moldable. Compared with Example 1, there is no significant difference in the macromorphology between Poly(BA-a) and Poly(PT-fa / BA-a)-40.

[0099] The TGA test results of Poly(BA-a) are as follows Figure 9 As shown, the T of Poly(BA-a) di The carbon residue rate Y at 328℃ and 800℃ c Compared with Example 1, the T di Relative to Poly(BA-a) T di Increased by 10℃; Y of Poly(PT-fa / BA-a)-20 c Y relative to Poly(BA-a) c The results showed that the thermal stability of Poly(PT-fa / BA-a)-40 was significantly improved compared to Poly(BA-a).

[0100] The DMA test results of Poly(BA-a) are as follows Figure 10 As shown, the Tg of Poly(BA-a) is 163.5°C. Compared with Example 1, the Tg of Poly(PT-fa / BA-a)-20 is significantly higher by 78.6°C, or 48.1%, relative to that of Poly(BA-a). These test results demonstrate that the addition of PT-fa to form a copolymer resin significantly improves heat resistance.

[0101] The MCC test results of Poly(BA-a) are as follows Figure 11As shown, the heat release capacity (HRC) of Poly(BA-a) is 166.2 J / g·K, and the total heat release (THR) is 21.5 kJ / g. Compared with Example 1, the HRC of Poly(PT-fa / BA-a)-20 is only 66.6% of that of Poly(BA-a), and the THR of Poly(PT-fa / BA-a)-20 is only 64.7% of that of Poly(BA-a). These test results demonstrate that the addition of PT-fa to form a copolymer resin improves flame retardancy.

[0102] By comparing Example 1 and Comparative Example 1, it can be seen that the copolymer resin Poly(PT-fa / BA-a) formed by adding PT-fa to BA-a has significantly improved thermal stability and flame retardant properties compared to commercial Poly(BA-a).

[0103] In order to demonstrate the effect of the amount of PT-fa added on the properties of the copolymer resin, Examples 2, 3 and 4 are provided, in which the copolymer resins were prepared with PT-fa additions of 40 wt.%, 10 wt.% and 5 wt.%, respectively.

[0104] Example 2

[0105] A method for preparing a flame-retardant bio-based copolymer resin based on PT-fa with a PT-fa addition amount of 20 wt.%. Unless otherwise specified, the steps are the same as those in Example 1, except that: in step 2, the mass ratio of PT-fa to BA-a is 20:80, that is, 6.054 g PT-fa and 24.216 g BA-a are blended. The resulting flame-retardant bio-based copolymer resin based on PT-fa is abbreviated as Poly(PT-fa / BA-a)-20.

[0106] The DSC test results of (PT-fa / BA-a)-20 are as follows Figure 6 As shown, the curing exotherm peak of (PT-fa / BA-a)-20 is broad and short. These test results indicate that the curing reaction of (PT-fa / BA-a)-20 is mild, effectively avoiding the problem of excessive local temperatures caused by a vigorous curing reaction, which can lead to sample decomposition.

[0107] Therefore, in order to further prove the molding performance of Poly(PT-fa / BA-a)-20, macromorphology test was carried out. Figure 7 As shown, Poly(PT-fa / BA-a)-40 is a tough, black solid with no bubbles, indicating moldability. Compared with Example 1, there is no significant difference in the macromorphology between Poly(PT-fa / BA-a)-20 and Poly(PT-fa / BA-a)-40.

[0108] In order to prove the successful preparation of Poly(PT-fa / BA-a)-20, FTIR test was performed. The test results are as follows Figure 8 As shown in Figure 1, the characteristic peaks of CN, COC, and oxazine rings disappear. Comparing the test results with those in step 1, it can be seen that PT-fa undergoes a ring-opening crosslinking reaction to form a cured resin Poly(PT-fa).

[0109] The TGA test results of Poly(PT-fa / BA-a)-20 are as follows Figure 9 As shown, the T of Poly(PT-fa / BA-a)-20 di The carbon residue rate Y at 335℃ and 800℃ c Compared with Example 1, it can be seen that increasing the amount of PT-fa added can improve the thermal stability of the copolymer resin.

[0110] The DMA test results of Poly(PT-fa / BA-a)-20 are as follows Figure 10 As shown, the T of Poly(PT-fa / BA-a)-20 g The temperature is 219.3° C. Compared with Example 1, it can be seen that increasing the amount of PT-fa added can improve the heat resistance of the copolymer resin.

[0111] The MCC test results of Poly(PT-fa / BA-a)-20 are as follows Figure 11 As shown, the heat release capacity (HRC) of Poly(PT-fa / BA-a)-20 is 142.5 J / g·K, and the total heat release (THR) is 17.7 kJ / g. Compared with Example 1, increasing the amount of PT-fa can improve the flame retardancy of the copolymer resin.

[0112] Example 3

[0113] A method for preparing a copolymer resin based on PT-fa and BA-a with a PT-fa addition amount of 10 wt.%. Unless otherwise specified, the steps are the same as those in Example 1, except that: in step 2, the mass ratio of PT-fa to BA-a is 10:90, that is, 1.534 g PT-fa and 13.81 g BA-a are blended. The resulting PT-fa-based flame-retardant bio-based copolymer resin is abbreviated as Poly(PT-fa / BA-a)-10.

[0114] The MCC test results of Poly(PT-fa / BA-a)-10 are as follows Figure 15 As shown in the figures, the heat release capacity HRC of Poly(PT-fa / BA-a)-10 is 174.4 J / g·K, and the total heat release THR is 19.8 kJ / g. Compared with Example 1, it can be seen that reducing the amount of PT-fa added reduces the flame retardant properties of the copolymer resin.

[0115] Example 4

[0116] A method for preparing a copolymer resin based on PT-fa and BA-a with a PT-fa addition amount of 5 wt.%. Unless otherwise specified, the steps are the same as those in Example 1, except that: in step 2, the mass ratio of PT-fa to BA-a is 5:95, that is, 1.054 g PT-fa and 20.026 g BA-a are blended. The resulting PT-fa-based flame-retardant bio-based copolymer resin is referred to as Poly(PT-fa / BA-a)-5.

[0117] The MCC test results of Poly(PT-fa / BA-a)-5 are as follows Figure 16 As shown in the figures, the heat release capacity HRC of Poly(PT-fa / BA-a)-5 is 174.0 J / g·K, and the total heat release THR is 21.0 kJ / g. Compared with Example 1, it can be seen that reducing the amount of PT-fa added reduces the flame retardant properties of the copolymer resin.

[0118] It can be seen from Examples 1, 2, 3, and 4 that as the amount of PT-fa added to BA-a increases, the thermal stability and flame retardancy of the resulting copolymer resin are significantly improved; however, excessive addition will lead to a significant decrease in the molding performance of the copolymer resin. Therefore, when the addition amount of PT-fa is 40 wt.%, the overall performance is optimal.

Claims

1. A flame retardant bio-based copolymer resin based on PT-fa, characterized in that: A mixed resin is prepared using the bio-based benzoxazine monomer PT-fa and bisphenol A-aniline benzoxazine BA-a as raw materials. The mixed resin is then thermally cured to obtain a flame-retardant bio-based copolymer resin (Poly(PT-fa / BA-a)) based on PT-fa. The resulting copolymer resin has high thermal stability and high flame retardancy. The PT-fa is prepared using hydroxytyrosol, furfurylamine and paraformaldehyde as raw materials through a solvent-free synthesis method, and the obtained monomer has high purity.

2. The flame retardant bio-based copolymer resin based on PT-fa according to claim 1, characterized in that: The glass transition temperature T of the Poly (PT-fa / BA-a) g It is 180-300℃.

3. The flame retardant bio-based copolymer resin based on PT-fa according to claim 1, characterized in that: The temperature T when the Poly (PT-fa / BA-a) loses 5% of its weight under nitrogen atmosphere di The carbon residue rate Y at 328-340℃ and 800℃ c It is 38-60%.

4. The flame retardant bio-based copolymer resin based on PT-fa according to claim 1, characterized in that: The heat release capacity HRC of the Poly (PT-fa / BA-a) is 80-175 J / g·K, and the total heat release THR is 10-21 kJ / g.

5. A method for preparing a flame retardant bio-based copolymer resin based on PT-fa, characterized in that The following steps are involved: Step 1, preparation of the bio-based benzoxazine monomer PT-fa, comprising mixing hydroxytyrosol, furfurylamine, and paraformaldehyde in a certain molar ratio, and conducting a Mannich condensation reaction under certain conditions by a solvent-free method. After completion of the reaction, the mixture is recrystallized and dried to obtain the bio-based benzoxazine monomer, referred to as PT-fa. Step 2, preparation of a flame-retardant bio-based copolymer resin based on PT-fa. First, under certain conditions, the PT-fa obtained in step 1 and bisphenol A-aniline benzoxazine BA-a are completely melted to obtain a mixed resin. Then, the molten mixed resin is placed in a mold. Finally, the mixed resin is cured to obtain a flame-retardant bio-based copolymer resin based on PT-fa, referred to as Poly(PT-fa / BA-a).

6. The preparation method according to claim 5, characterized in that: In the step 1, the molar ratio of hydroxytyrosol, furfurylamine and paraformaldehyde is 1:2:

4.

7. The preparation method according to claim 5, characterized in that: In step 1, the conditions for the Mannich condensation reaction are: in an oil bath with stirring, the reaction temperature is 110° C., and the reaction time is 6 h; In the step 1, the recrystallization operation is carried out in ethanol.

8. The preparation method according to claim 5, characterized in that: In step 2, the mass ratio of PT-fa to BA-a is 2:(3-38); the conditions for completely melting PT-fa and BA-a to obtain a mixed resin are: under stirring conditions, the heating temperature is 115-140°C, and the heating time is 5-30 minutes.

9. The preparation method according to claim 5, characterized in that: In step 2, the curing conditions are divided into 4 stages: Stage 1: curing temperature is 180°C and curing time is 1h; Stage 2: curing temperature is 200°C and curing time is 1h; Stage 3: curing temperature is 220°C and curing time is 1h; Stage 4 is a curing temperature of 240°C and a curing time of 2 hours.

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