Bio-based pentanediamine-based benzoxazine monomers, resins, and methods of making and using the same

Abstract

The application belongs to the technical field of high polymer materials, and discloses a bio-based pentanediamine-based benzoxazine monomer, a resin, and a preparation method and application thereof. The bio-based pentanediamine-based benzoxazine monomer is prepared by a Mannich reaction with phenolic compounds, paraformaldehyde and bio-based pentanediamine as raw materials, and further heat-cured to obtain a benzoxazine resin. The bio-based pentanediamine is used as a main raw material for synthesizing the benzoxazine resin, thereby reducing the use of petroleum-based raw materials from the source, expanding the application field of the bio-based pentanediamine, and the bio-based raw material is a renewable resource, which conforms to the concept of green and sustainable development. The benzoxazine resin obtained by heat curing has good heat resistance, mechanical properties and good low dielectric properties.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to benzoxazine monomers, resins, preparation methods and applications based on bio-based pentanediamine. Background Technology

[0002] Benzoxazine resin, as a novel thermosetting resin, is widely used in aerospace, automotive manufacturing, electronic devices, and many other fields. Its monomers are prepared by condensation reactions of phenolic compounds, primary amine compounds, and paraformaldehyde, etc., and then undergo ring-opening reactions under high temperature or with a catalyst to form polybenzoxazine, without generating small molecules during ring-opening polymerization. Furthermore, benzoxazine resin has the following advantages: ① high heat resistance; ② excellent electrical insulation properties; ③ good mechanical properties; ④ high flexibility in molecular design; ⑤ no release of small molecules during curing; ⑥ low porosity and near-zero shrinkage of the cured product, etc. These advantages make benzoxazine resin a promising new high-performance resin with the potential for widespread application in various fields.

[0003] To date, the raw materials for synthesizing benzoxazine resins have primarily come from petroleum products. However, petroleum is a non-renewable resource, and its extraction and utilization place significant pressure on Earth's resources. Furthermore, due to the finite nature of petroleum resources, long-term reliance on petroleum-based raw materials will lead to resource depletion. The refining and processing of petroleum generates substantial amounts of pollutants and greenhouse gases, causing severe environmental impacts, including air, water, and soil pollution. This is inconsistent with the strategies and principles of sustainable development. Therefore, developing renewable bio-based raw materials to replace petroleum-based raw materials is of great significance in order to reduce environmental harm and decrease dependence on finite resources. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing benzoxazine resins by providing a benzoxazine monomer based on bio-based pentanediamine and its preparation method, using renewable biomass as raw material, which conforms to the strategy and concept of environmental protection and sustainable development; and the thermosetting resin prepared based on this monomer has low dielectric, high heat resistance and high toughness properties.

[0005] Another object of the present invention is to provide a thermosetting resin with both high temperature resistance and low dielectric constant prepared from the above-mentioned benzoxazine monomer based on bio-based pentanediamine, and a method thereof.

[0006] Another object of the present invention is to provide uses for the above-mentioned thermosetting resin.

[0007] Bio-based pentanediamine is a bio-based raw material, typically produced from vegetable oils. It can be obtained by reacting glycerides from vegetable oils with carbamates. Bio-based pentanediamine is commonly used as an intermediate in polyamide polymers, which can be used to produce products such as coatings, adhesives, elastomers, and plastics.

[0008] The production and application of bio-based pentanediamine aligns with the concept of sustainable development because it reduces dependence on petroleum-based feedstocks and mitigates environmental impact to some extent. Therefore, introducing bio-based pentanediamine as an amine source into benzoxazine, and then using different phenolic compounds (including bio-based phenols such as cashew phenol, vanillin, and capsaicin) as phenolic sources, holds promise for preparing benzoxazine resins with varying properties.

[0009] The benzoxazine monomer based on bio-based pentanediamine provided by this invention has one of the following structural formulas:

[0010]

[0011] Wherein, R1 and R2 independently represent -H, -CH3, -F, -Cl, -CF3, -NO2, -C6H5, -OCH3, -CHO, -C(CH3)3, -C3H5, and -C, respectively. 15 H 32 -C 15 H 30 -C 15 H 28 -C 15 H 26 One of them.

[0012]

[0013] Where R1 independently represents -H, -CH3, -F, -Cl, -CF3, -NO2, -C6H5, -OCH3, -CHO, -C(CH3)3, -C3H5, -C 15 H 32 -C 15 H 30 -C 15 H 28 -C 15 H 26 One of them; R2 represents a substituent directly attached to the benzene ring, independently representing one of -O-, -CH2-, -SO2-, -CF2-, -C(CH2)2-, -CO-, -C(CF3)2;

[0014]

[0015] Among them, phenolic compounds are triphenols, and R represents the substituent structure of polyphenols, which can be any one of alkyl, aryl or phosphate groups;

[0016] This invention also provides a method for preparing a bio-based pentanediamine benzoxazine monomer. Using phenolic compounds, bio-based pentanediamine, and paraformaldehyde or an aqueous formaldehyde solution as raw materials, the bio-based benzoxazine monomer is prepared via the Mannich reaction. Specifically, the phenolic compound, bio-based pentanediamine, and paraformaldehyde or an aqueous formaldehyde solution are mixed in an organic solvent, then reacted at 60-160°C for 1-10 hours, followed by post-treatment to obtain the benzoxazine monomer. The molar ratio of the phenolic hydroxyl group in the phenolic compound, the amino group in the bio-based pentanediamine, and the aldehyde group in the paraformaldehyde is 1:1:2-3; the formaldehyde concentration in the aqueous formaldehyde solution is 35-40%.

[0017] The bio-based pentanediamine is a bio-based 1,5-pentanediamine, which can be prepared by microbial fermentation or enzymatic conversion.

[0018] The organic solvent is at least one of toluene, chloroform, dioxane, ethanol, dimethyl sulfoxide, ethyl acetate, xylene, N,N-dimethylformamide, etc.

[0019] When the phenolic compound is a monophenolic compound, the preparation method of the benzoxazine monomer of bio-based pentanediamine is as follows: Under stirring conditions, bio-based pentanediamine is added dropwise to reaction system I, which consists of the phenolic compound, paraformaldehyde or an aqueous formaldehyde solution, and an organic solvent. The reaction is then carried out at 60-160℃ for 1-10 hours, followed by post-treatment to obtain the benzoxazine monomer. During the dropwise addition, the temperature of reaction system I is 30-60℃.

[0020] The monofunctional phenolic compound is at least one of the following phenols:

[0021]

[0022] When the phenolic compound is a bisphenol or triphenol, the preparation method of the benzoxazine monomer of bio-based pentanediamine is as follows: Under stirring conditions, bio-based pentanediamine is added dropwise to reaction system II, which is formed by paraformaldehyde or an aqueous formaldehyde solution and an organic solvent. Then, the phenolic compound is added, and the reaction is carried out at 60-160℃ for 1-10 hours. After post-treatment, the benzoxazine monomer is obtained. During the dropwise addition, the temperature of reaction system II is room temperature.

[0023] The bisphenol compound is one of the following phenols:

[0024]

[0025] The trifunctional phenolic compound is at least one of the following phenols:

[0026]

[0027] The preparation method of the above-mentioned bio-based pentanediamine benzoxazine monomer includes the following post-processing after the reaction: after the obtained reaction solution is cooled to room temperature and separated into layers, the organic phase is washed with sodium hydroxide aqueous solution and water in sequence until neutral, and then the organic phase is subjected to vacuum distillation to obtain the benzoxazine monomer.

[0028] The present invention also discloses a benzoxazine resin, which is obtained by gradient thermosetting at 140-220℃ using the above-mentioned benzoxazine monomer based on bio-based pentanediamine as raw material, and the curing reaction time is 8-20h. In a preferred embodiment, staged thermosetting is adopted, and the specific conditions are: 140-150℃, heat preservation reaction for 2-4h; 160-170℃, heat preservation reaction for 2-4h; 180-190℃, heat preservation reaction for 2-4h; 200-220℃, heat preservation reaction for 2-4h.

[0029] The present invention also provides the application of the above-mentioned benzoxazine resin in the preparation of fiber-reinforced composite materials, printed circuit boards, coatings, adhesives, or semiconductor packaging materials. Products made from this resin can still be used normally in high-temperature environments, and when used in materials related to printed circuit boards, it helps to ensure a faster signal propagation rate and lower information loss.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) This invention provides a benzoxazine monomer based on bio-based pentanediamine, which is introduced into benzoxazine through molecular design, solving the problem of a single source of reaction raw materials; moreover, bio-based raw materials are renewable resources, which are in line with the concept of green and sustainable development.

[0032] (2) The method for preparing benzoxazine monomer based on bio-based pentanediamine provided by the present invention uses bio-based 1,5-pentanediamine, paraformaldehyde and phenolic compounds as raw materials. By adjusting the order and method of adding each raw material, it is beneficial to avoid side reactions, generate gel, and ensure that the reaction proceeds normally, so that the generated benzoxazine has a higher ring-closure rate and higher purity; and the prepared benzoxazine monomer has a clear structure, stable intermediate products, is easy to process and mold, and has excellent reactivity.

[0033] (3) The benzoxazine resin obtained by thermosetting using the benzoxazine monomer prepared in this invention as raw material has good heat resistance, mechanical properties and good low dielectric properties.

[0034] (4) The benzoxazine thermosetting resin prepared by the present invention can be used to prepare fiber reinforced composite materials, printed circuit boards, coatings, adhesives or semiconductor packaging materials. It has excellent heat resistance, low dielectric constant and dielectric loss factor, excellent performance, simple product preparation process, easy operation and strong practicality. Attached Figure Description

[0035] Figure 1 The FTIR spectrum of the benzoxazine monomer (i.e., PH-p) prepared in Example 1;

[0036] Figure 2 The benzoxazine monomer (i.e., PH-p) prepared in Example 1 1 H NMR spectrum;

[0037] Figure 3 Storage modulus-temperature curve of the benzoxazine resin (i.e., PPH-p) prepared in Example 1;

[0038] Figure 4 Tanδ-temperature curve of the benzoxazine resin (i.e., PPH-p) prepared in Example 1;

[0039] Figure 5 The dielectric constant-frequency of the benzoxazine resin (i.e., PPH-p) prepared in Example 1;

[0040] Figure 6 Dielectric loss-frequency of the benzoxazine resin (i.e., PPH-p) prepared in Example 1;

[0041] Figure 7 The FTIR spectrum of the benzoxazine monomer (i.e., VA-p) prepared in Example 6;

[0042] Figure 8 The benzoxazine monomer (i.e., VA-p) prepared in Example 6 1 H NMR spectrum. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are part of the present invention.

[0044] The following method for preparing bio-based 1,5-pentanediamine can be found in patent application CN110468167A.

[0045] Example 1

[0046] This embodiment provides a method for preparing phenol (structural formula as shown in (1)) / bio-based pentanediamine type benzoxazine monomer, the specific steps of which are as follows:

[0047] In a three-necked round-bottom flask equipped with a magnetic stirrer and a spherical condenser, 0.2 mol of phenol, 0.44 mol of paraformaldehyde and 100 g of xylene were added sequentially. The reaction temperature was then controlled at 50 °C. After the temperature stabilized, 0.1 mol of bio-based 1,5-pentanediamine was added dropwise over 1.5 h. The reaction temperature was then set to 125 °C and the reaction was continued for 3 h. After the reaction was completed, the organic phase was washed with sodium hydroxide aqueous solution and then washed with water until neutral (pH = 7). The resulting solution was then subjected to vacuum distillation to finally obtain the phenol / bio-based pentanediamine type benzoxazine monomer (i.e., pH-p) (structural formula as shown in (2)). The calculated product yield was approximately 94.3%.

[0048]

[0049] The prepared product, a phenol / bio-based pentanediamine-type benzoxazine monomer, was analyzed by infrared spectroscopy and mass spectrometry. The measured FTIR and mass spectrometry results were obtained. 1 The H NMR spectrum is shown in [reference]. Figure 1 and Figure 2 As shown.

[0050] Figure 1 921cm -1 An absorption peak of the oxazine ring appeared at [value missing] cm⁻¹, and the COC symmetric stretching vibration and antisymmetric stretching vibration appeared at 1033 and 1224 cm⁻¹, respectively. -1 CNC telescopic vibration occurred at 1137cm. -1 The bisubstituted peak of the benzene ring appears at 1488 cm⁻¹. -1 ; 2934 and 2857cm -1 The characteristic peak corresponds to the methylene group in pentanediamine. The FTIR spectrum essentially confirms the successful synthesis of the PH-p monomer.

[0051] from Figure 2 As can be seen, the chemical shifts of hydrogen in the oxazine rings -Ar-CH2-N- and -O-CH2-N- are (a) 3.95 ppm and (b) 4.78 ppm, respectively, with an integral area ratio of a:b = 3.99:4, indicating the presence of a benzoxazine cyclic structure in the product. The chemical shifts of the relevant hydrogen (Ar-H) on the benzene ring are between 7.23 and 6.64 ppm. The chemical shifts of the hydrogen on the methylene group of the pentanediamine are (c) 2.60 ppm, (d) 1.49 ppm, and (e) 1.29 ppm, respectively, with an integral area ratio of c:d:e = 4.21:4.21:1.80. 1 The HNMR spectrum basically confirms that the PH-p monomer was successfully synthesized.

[0052] The monomer was placed in a pre-prepared mold, and the monomer was thermocured under the following conditions: 140℃ for 2 hours, 160℃ for 2 hours, 180℃ for 2 hours, and 200℃ for 2 hours. After cooling, phenol / bio-based pentanediamine benzoxazine resin (i.e., PPH-p) was obtained.

[0053] The storage modulus-temperature curve and Tanδ-temperature curve of the prepared resin PPH-p are shown in the figure below. Figure 3 and Figure 4 As shown. The storage modulus of PPH-p at 50℃ is 2.76 GPa, T g The temperature is 205℃.

[0054] The dielectric constant-frequency and dielectric loss-frequency of the prepared resin PPh-p are as follows: Figure 5 and Figure 6 As shown, the dielectric constant and dielectric loss of PPH-p at 1MHz are 2.42 and 0.0147, respectively.

[0055] In addition, the bending properties of the prepared resin PPH-p were tested, and the deflection was 4.99 mm, the bending strength was 75 MPa, and the bending modulus was 3.2 GPa.

[0056] The test results above show that the benzoxazine resin obtained by thermosetting phenol / bio-based pentanediamine benzoxazine monomer has good heat resistance, mechanical properties, and low dielectric properties. It can be used to prepare fiber-reinforced composite materials, printed circuit boards, coatings, adhesives, or semiconductor packaging materials.

[0057] Example 2

[0058] This embodiment provides a method for preparing α-naphthol (structural formula as shown in (3)) / bio-based pentanediamine-type benzoxazine monomer, the specific steps of which are as follows:

[0059] In a three-necked round-bottom flask equipped with a magnetic stirrer and a spherical condenser, 0.2 mol of phenol-naphthalene α, an aqueous solution of formaldehyde (concentration of 35-40%, formaldehyde 0.44 mol), and 100 g of organic solvent dioxane were added sequentially. The reaction temperature was then controlled at 45 °C. After the temperature stabilized, 0.1 mol of bio-based 1,5-pentanediamine was added dropwise over 2 hours. The reaction temperature was then set to 75 °C and the reaction was continued for 5 hours. After the reaction was completed, the organic phase was washed with an aqueous solution of sodium hydroxide and then washed with water until neutral (pH = 7). The resulting solution was then subjected to vacuum distillation to finally obtain the α-naphthol / bio-based pentanediamine type benzoxazine monomer (i.e., αNA-p) (structural formula as shown in (4)). The calculated product yield was approximately 97.6%.

[0060]

[0061] The monomer was placed in a pre-prepared mold, and the monomer was thermocured under the following conditions: 140℃ for 2 hours, 160℃ for 2 hours, 180℃ for 2 hours, and 200℃ for 2 hours. After cooling, phenol-naphthalene α / bio-based pentanediamine benzoxazine resin (i.e., PαNA-p) was obtained.

[0062] Example 3

[0063] This embodiment provides a method for preparing bisphenol A (structural formula as shown in (5)) / bio-based pentanediamine benzoxazine monomer, the specific steps of which are as follows:

[0064] In a three-necked round-bottom flask equipped with a magnetic stirrer and a spherical condenser, 0.44 mol of paraformaldehyde and 100 g of organic solvent (xylene / toluene (V:V = 1:1)) were added sequentially. At room temperature, 0.1 mol of bio-based 1,5-pentanediamine was added dropwise over 2.5 h. Then, 0.1 mol of bisphenol A was added, and the reaction temperature was set to 100 °C and the reaction was continued for 6 h. After the reaction was completed, the organic phase was washed with sodium hydroxide aqueous solution and then washed with water until neutral (pH = 7). The resulting solution was then subjected to vacuum distillation to finally obtain the bisphenol A / bio-based pentanediamine type benzoxazine monomer (i.e., BA-p) (structural formula as shown in (6)). The calculated product yield was approximately 79.8%.

[0065]

[0066] The monomer was placed in a pre-prepared mold, and the monomer was thermocured under the following conditions: 150℃ for 4 hours, 170℃ for 4 hours, 190℃ for 4 hours, and 220℃ for 4 hours. After cooling, bisphenol A / bio-based pentanediamine benzoxazine resin (i.e., PBA-p) was obtained.

[0067] Example 4

[0068] This embodiment provides a method for preparing bisphenol F (structural formula as shown in (7)) / bio-based pentanediamine-type benzoxazine monomer, the specific steps of which are as follows:

[0069] In a three-necked round-bottom flask equipped with a magnetic stirrer and a spherical condenser, 0.44 mol of paraformaldehyde and 100 g of organic solvent toluene were added sequentially. At room temperature, 0.1 mol of bio-based 1,5-pentanediamine was added dropwise over 1 hour. Then, 0.1 mol of bisphenol F was added, and the reaction temperature was set to 105 °C. The reaction was continued for 8 hours. After the reaction was completed, the organic phase was washed with sodium hydroxide aqueous solution and then washed with water until neutral (pH = 7). The resulting solution was then subjected to vacuum distillation to finally obtain the bisphenol F / bio-based pentanediamine type benzoxazine monomer (i.e., BF-p) (structural formula as shown in (8)). The calculated product yield was approximately 81.4%.

[0070]

[0071] The monomer was placed in a pre-prepared mold, and the monomer was thermocured under the following conditions: 150℃ for 3 hours, 170℃ for 3 hours, 190℃ for 3 hours, and 210℃ for 3 hours. After cooling, bisphenol F / bio-based pentanediamine benzoxazine resin (i.e., PBF-p) was obtained.

[0072] Example 5

[0073] This embodiment provides a method for preparing triphenol 1,1,1-tris(4-hydroxyphenyl)ethane (structural formula as shown in (9)) / bio-based pentanediamine type benzoxazine monomer, the specific steps of which are as follows:

[0074] In a three-necked round-bottom flask equipped with a magnetic stirrer and a spherical condenser, formaldehyde aqueous solution (concentration of 35-40%, formaldehyde 0.66 mol) and 150 g of organic solvent dimethyl sulfoxide were added sequentially; at room temperature, 0.15 mol of bio-based 1,5-pentanediamine was added dropwise over 1 h; then 0.1 mol of 1,1,1-tris(4-hydroxyphenyl)ethane was added, and the reaction temperature was set to 145 °C, and the reaction was continued for 9 h; after the reaction was completed, the organic phase was washed with sodium hydroxide aqueous solution, and then washed with water until neutral (pH=7), and then the resulting solution was subjected to vacuum distillation to finally obtain the triphenol / bio-based pentanediamine type benzoxazine monomer (i.e., ET-p) (structural formula as shown in (10)), and the calculated product yield was approximately 81.4%.

[0075]

[0076] The monomer was placed in a pre-prepared mold, and the monomer was thermocured under the following conditions: 140℃ for 4 hours, 160℃ for 4 hours, 180℃ for 4 hours, and 200℃ for 4 hours. After cooling, bisphenol F / bio-based pentanediamine benzoxazine resin (i.e., PET-p) was obtained.

[0077] Example 6

[0078] This embodiment provides a method for preparing a fully bio-based vanillin (structural formula as shown in (11)) / pentanediamine type benzoxazine monomer, the specific steps of which are as follows:

[0079] In a three-necked round-bottom flask equipped with a magnetic stirrer and a spherical condenser, 0.2 mol vanillin, 0.44 mol paraformaldehyde and 100 g organic solvent ethanol were added sequentially. The reaction temperature was then controlled at 55 °C. After the temperature stabilized, 0.1 mol of bio-based 1,5-pentanediamine was added dropwise over 3 hours. The reaction temperature was then set to 70 °C and the reaction was continued for 4 hours. After the reaction was completed, the organic phase was washed with sodium hydroxide aqueous solution and then washed with water until neutral (pH = 7). The resulting solution was then subjected to vacuum distillation to finally obtain the fully bio-based vanillin / pentanediamine type benzoxazine monomer (i.e., VA-p) (structural formula as shown in (12)). The calculated product yield was approximately 84.3%.

[0080]

[0081]

[0082] The prepared product, a fully bio-based vanillin / pentanediamine benzoxazine monomer, was analyzed by infrared spectroscopy and mass spectrometry. The FTIR and mass spectrometry results were obtained. 1 The H NMR spectrum is shown in [reference]. Figure 7 and Figure 8 As shown.

[0083] from Figure 7 It can be seen that the characteristic absorption peak of the oxazine ring appears at 896 cm⁻¹. -1 The COC antisymmetric stretching vibration appears at 1231 cm⁻¹. -1 CNC stretching vibration appeared at 1143cm. -1 ; 2937 and 2855cm -1 The absorption peak belongs to the methylene group in pentanediamine; the characteristic peak of the aldehyde group appears at 1683 cm⁻¹. -1 The substitution peaks of the benzene ring appeared at 1584 and 1492 cm⁻¹, respectively. -1 The FTIR spectrum confirms the successful synthesis of the VA-p monomer.

[0084] from Figure 8It can be seen that the chemical shifts of the hydrogen atoms on the methylene groups at -O-CH2-N- and -Ar-CH2-N- in the oxazine ring are (c) 5.03 ppm and (d) 4.04 ppm, respectively, with an integrated area ratio of c:d = 4:4. The chemical shifts of the hydrogen atoms related to the benzene ring (Ar-H) are between 7.32 and 7.13 ppm. The chemical shifts of the hydrogen atoms on the methoxy and aldehyde groups of vanillin are 3.95 and 9.80 ppm, respectively, with an integrated area ratio of a:b = 6.11:2.10. The chemical shifts of the hydrogen atoms on the methylene groups of pentanediamine are (e) 2.74 ppm, (f) 1.56 ppm, and (g) 1.25 ppm, respectively, with an integrated area ratio of e:f:g = 4.08:3.95:1.90. 1 The 1H NMR spectrum can basically confirm that the VA-p monomer was successfully synthesized.

[0085] The monomer was placed in a pre-prepared mold, and the monomer was thermocured under the following conditions: 140℃ for 2 hours, 160℃ for 2 hours, 180℃ for 2 hours, and 200℃ for 2 hours. After cooling, a fully bio-based vanillin / pentanediamine benzoxazine resin (i.e., PVA-p) was obtained.

[0086] Example 7

[0087] This embodiment provides a method for preparing a fully bio-based guaiacol (structural formula as shown in (13)) / pentanediamine type benzoxazine monomer, the specific steps of which are as follows:

[0088] In a three-necked round-bottom flask equipped with a magnetic stirrer and a spherical condenser, 0.2 mol of guaiacol, an aqueous formaldehyde solution (concentration of 35-40%, formaldehyde 0.44 mol), and 100 g of organic solvent toluene were added sequentially. The reaction temperature was then controlled at 40 °C. After the temperature stabilized, 0.1 mol of bio-based 1,5-pentanediamine was added dropwise over 2 hours. The reaction temperature was then set to 95 °C and the reaction was continued for 6 hours. After the reaction was completed, the organic phase was washed with an aqueous sodium hydroxide solution and then washed with water until neutral (pH = 7). The resulting solution was then subjected to vacuum distillation to finally obtain the fully bio-based guaiacol / pentanediamine type benzoxazine monomer (i.e., GU-p) (structural formula as shown in (14)). The calculated product yield was approximately 91.3%.

[0089]

[0090] The monomer was placed in a pre-prepared mold, and the monomer was thermocured under the following conditions: 140℃ for 2 hours, 160℃ for 2 hours, 180℃ for 2 hours, and 200℃ for 2 hours. After cooling, a fully bio-based guaiacol / pentanediamine benzoxazine resin (PGU-p) was obtained.

[0091] Example 8

[0092] This embodiment provides a method for preparing pyrogallol A (structural formula as shown in (15)) / bio-based pentanediamine benzoxazine monomer, the specific steps of which are as follows:

[0093] In a three-necked round-bottom flask equipped with a magnetic stirrer and a spherical condenser, 0.66 mol of paraformaldehyde and 120 g of organic solvent N,N-dimethylformamide were added sequentially. At room temperature, 0.15 mol of bio-based 1,5-pentanediamine was added dropwise over 3 h. Then, 0.1 mol of pyrogallol A was added, and the reaction temperature was set to 135 °C. The reaction was continued for 9 h. After the reaction was completed, the organic phase was washed with sodium hydroxide aqueous solution and then washed with water until neutral (pH = 7). The resulting solution was then subjected to vacuum distillation to finally obtain the pyrogallol A / pentanediamine type benzoxazine monomer (i.e., TRI-p) (structural formula as shown in (16)). The calculated product yield was approximately 79.7%.

[0094]

[0095]

[0096] The monomer was placed in a pre-prepared mold, and the monomer was thermocured under the following conditions: 150℃ for 4 hours, 170℃ for 4 hours, 190℃ for 4 hours, and 220℃ for 4 hours. After cooling, a pyrogallol A / pentanediamine type benzoxazine resin (i.e., PTRI-p) was obtained.

[0097] Therefore, the benzoxazine resins in the above embodiments of the present invention not only have a higher glass transition temperature (205°C), but also a lower dielectric constant (2.42) and dielectric loss (0.0147). They are more suitable for applications requiring high heat resistance and low loss, such as the preparation of fiber-reinforced composite materials, printed circuit boards, coatings, adhesives, or semiconductor packaging materials.

[0098] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A pentanediamine-based benzoxazine monomer characterized in that, It has one of the following structural formulas: ； （Ⅰ） Wherein, R1 and R2 independently represent one of -H, -CH3, -F, -Cl, -CF3, -NO2, -C6H5, -OCH3, -CHO, -C(CH3)3, and -C3H5, respectively; ； （Ⅱ） Wherein, R1 independently represents one of -H, -CH3, -F, -Cl, -CF3, -NO2, -C6H5, -OCH3, -CHO, -C(CH3)3, -C3H5; R2 represents a substituent directly attached to the benzene ring, independently representing one of -O-, -CH2-, -SO2-, -CF2-, -C(CH3)2-, -CO-, -C(CF3)2-; ; or ; or 。 2. A process for the preparation of the pentanediamine-based benzoxazine monomer of claim 1, characterized by, A phenolic compound, 1,5-pentanediamine, and paraformaldehyde or an aqueous formaldehyde solution are mixed in an organic solvent and then reacted at 60-160℃ for 1-10 h. After post-treatment, a benzoxazine monomer is obtained. The molar ratio of the phenolic hydroxyl group in the phenolic compound, the amino group in the 1,5-pentanediamine, and the aldehyde group in the paraformaldehyde or aqueous formaldehyde solution is 1:1:2-3.

3. The method of preparing a pentanediamine-based benzoxazine monomer according to claim 2, wherein, The organic solvent is at least one selected from toluene, chloroform, dioxane, ethanol, dimethyl sulfoxide, ethyl acetate, xylene, and N,N-dimethylformamide.

4. The method of preparing a pentanediamine-based benzoxazine monomer according to claim 2 or 3, characterized in that, When the phenolic compound is a monofunctional phenolic compound, the preparation method of benzoxazine monomer based on pentanediamine is as follows: Under stirring conditions, 1,5-pentanediamine is added dropwise to reaction system I, which is formed by phenolic compound, paraformaldehyde or formaldehyde aqueous solution and organic solvent, and then reacted at 60-160℃ for 1-10h, and then post-processed to obtain benzoxazine monomer; during the dropwise addition, the temperature of reaction system I is 30-60℃; The monophenolic compound is one of the following phenols: 。 5. The method of preparing a pentanediamine-based benzoxazine monomer according to claim 2 or 3, characterized in that, When the phenolic compound is a bifunctional or trifunctional phenolic compound, the preparation method of benzoxazine monomer based on pentanediamine is as follows: Under stirring conditions, 1,5-pentanediamine is added dropwise to reaction system II formed by paraformaldehyde or formaldehyde aqueous solution and organic solvent, and then the phenolic compound is added. The reaction is carried out at 60-160℃ for 1-10 h, and then post-processed to obtain benzoxazine monomer; during the dropwise addition, the temperature of reaction system II is room temperature; The bisphenol compound is one of the following phenols: ； The triphenolic compound is one of the following phenols: 。 6. The method of preparing a pentanediamine-based benzoxazine monomer according to claim 2, wherein, The post-reaction process is as follows: after the reaction solution is cooled to room temperature, the organic phase is washed with sodium hydroxide aqueous solution and water in sequence until neutral, and then the organic phase is subjected to vacuum distillation to obtain benzoxazine monomer.

7. A benzoxazine resin characterized in that, The product is obtained by gradient thermosetting at 140-220℃ using the benzoxazine monomer based on pentanediamine as described in claim 1 as the raw material, with a curing reaction time of 8-20h.

8. The benzoxazine resin according to claim 7, wherein, The process employs a phased thermosetting method, with the following specific conditions: 140-150℃, heat preservation reaction for 2-4 hours; 160-170℃, heat preservation reaction for 2-4 hours; 180-190℃, heat preservation reaction for 2-4 hours; 200-220℃, heat preservation reaction for 2-4 hours.

9. The use of the benzoxazine resin according to claim 7 or 8 for the production of fiber reinforced composites, printed circuit boards, coatings, adhesives or semiconductor encapsulating materials.

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