A bio-based benzoxazine monomer modified epoxy resin and preparation method thereof

Abstract

The present invention discloses a bio-based benzoxazine monomer-modified epoxy resin and a preparation method thereof. The method comprises: reacting guaiacol, ethanolamine, and paraformaldehyde to obtain a bio-based benzoxazine monomer; reacting the bio-based benzoxazine monomer with phosphorus oxychloride in a solvent to obtain a benzoxazine phosphate monomer; and uniformly mixing the benzoxazine phosphate as a modifying curing agent, a bio-based diamine Priamine 1074 as a toughening curing agent, and a bisphenol A-type epoxy resin (DGEBA). The mixture is poured into a mold, and then heated and cured to obtain the bio-based benzoxazine monomer-modified epoxy resin. The bio-based benzoxazine monomer-modified epoxy resin obtained by the present invention has strong mechanical properties and thermal stability, as well as excellent adhesion, flame retardancy, low dielectric properties, and biodegradability.

Description

Technical Field

[0001] The invention relates to a bio-based benzoxazine monomer modified epoxy resin and a preparation method thereof, belonging to the technical field of natural resource modification. Background Art

[0002] With increasing awareness of global resource and environmental issues, coupled with the rapid depletion of petroleum energy, energy crises and environmental problems have become unavoidable and must be addressed head-on. The search for natural, renewable resources to replace traditional petroleum-based feedstocks in the synthesis of polymer materials has become a research hotspot. Guaiacol and Priamine 1074, derived from lignin-degrading phenols and plant oil extracts, respectively, are both renewable forestry biomass resources. While Priamine 1074 can be used as a curing agent for epoxy resins, its low crosslink density, poor thermal stability, flammability, poor degradation, and low mechanical strength limit its application.

[0003] Benzoxazine resins are a new class of thermosetting resins developed from traditional phenolic resins. They offer advantages such as flexible molecular design, excellent thermal stability, and low dielectric properties, showing potential for application in aerospace, hydrophobic flame retardancy, anti-corrosion and antimicrobial properties, and electronic communications. Unlike traditional thermosetting resins, benzoxazine resins can be made from natural, renewable resources in addition to fossil feedstock. Currently, monomers for benzoxazine resins have been synthesized from renewable resources, achieving breakthroughs in raw material sourcing and performance improvements. Their flexible molecular design allows for the introduction of a variety of reactive groups. Furthermore, the ring-opening process of benzoxazine monomers forms numerous phenolic hydroxyl and tertiary amine groups. These phenolic hydroxyl groups can participate in the ring-opening reaction of epoxy groups to form a cross-linked network, while the tertiary amine groups also promote this reaction. Furthermore, the benzoxazine backbone further enhances the rigidity and thermal stability of the molecular chain, making benzoxazine monomers an excellent epoxy resin modification and curing agent. Summary of the Invention

[0004] To address the defects of epoxy resins in the prior art, such as low mechanical strength and poor thermal stability, the present invention provides a bio-based benzoxazine monomer-modified epoxy resin and a preparation method thereof. The prepared bio-based benzoxazine monomer-modified epoxy resin increases the resin's molecular chain rigidity and nitrogen and phosphorus content, thereby imparting high tensile strength, excellent thermal stability, and superior non-flammability. The introduction of phosphate bonds imparts the resin with improved flame retardancy and recyclability. Furthermore, the resin exhibits good hydrophobicity, adhesion, and low dielectric properties.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] A bio-based benzoxazine monomer modified epoxy resin, characterized in that: its raw material components include: bio-based benzoxazine phosphate monomer TBP, bio-based diamine Priamine 1074 and bisphenol A diglycidyl ester DGEBA;

[0007] Their structural formulas are:

[0008]

[0009] The present invention also provides a method for preparing a bio-based benzoxazine monomer modified epoxy resin, comprising the following steps:

[0010] (1) reacting guaiacol, ethanolamine, and paraformaldehyde to obtain a bio-based benzoxazine monomer;

[0011] (2) adding a bio-based benzoxazine monomer and phosphorus oxychloride into a solvent for reaction to obtain a bio-based benzoxazine phosphate monomer;

[0012] (3) mixing the bio-based benzoxazine phosphate monomer, the bio-based diamine Priamine 1074, and bisphenol A diglycidyl ester evenly and pouring the mixture into a mold, and then heating and curing the mixture to obtain a bio-based benzoxazine monomer-modified epoxy resin;

[0013] The reaction process is:

[0014]

[0015] Preferably, the reaction temperature in step (1) is 60° C. to 90° C., and the reaction time is 12 to 18 hours.

[0016] Preferably, the reaction temperature in step (2) is 0°C to 10°C, and the reaction time is 24 to 36 hours.

[0017] Preferably, the molar ratio of the sum of the molar amount of the oxazine ring of the bio-based benzoxazine phosphate monomer and the molar amount of the active hydrogen of the bio-based diamine Priamine 1074 to the epoxy group of bisphenol A diglycidyl ester is 1:1.

[0018] Preferably, the mass ratio of the phosphorus content of the bio-based benzoxazine phosphate monomer to the total of the bio-based benzoxazine phosphate monomer, the bio-based diamine Priamine 1074 and bisphenol A diglycidyl ester is 0.95:100 to 2.46:100.

[0019] Preferably, the curing reaction in step (3) is an autocatalytic reaction system.

[0020] Preferably, the guaiacol, paraformaldehyde and bio-based diamine Priamine 1074 are derived from lignin, biomethanol and vegetable oil, respectively.

[0021] Preferably, the temperature rising and curing procedure is:

[0022] After pre-curing at 60-100°C for 4-8 hours, cure at 100-150°C for 4-6 hours, and finally cure at 150-200°C for 2-4 hours, then cool down.

[0023] Preferably, the cooling process is to cool to room temperature at a cooling rate of 5 to 8°C / min.

[0024] The technologies not mentioned in this invention are all referred to the prior art.

[0025] (1) The bio-based benzoxazine monomer-modified epoxy resin of the present invention exhibits strong mechanical properties and good thermal stability, as well as excellent adhesion, hydrophobicity, flame retardancy, and degradation properties. Its room temperature tensile strength can reach 53 MPa, and its tensile modulus can reach 875 MPa. The temperature for 5% thermal weight loss is above 316°C, and the carbon residue at 800°C is 37.4%, both of which far exceed those of Priamine 1074-cured bisphenol A epoxy resin DGEBA without the addition of benzoxazine monomer. Furthermore, it achieves a V-0 rating in the UL-94 flame retardancy test, with an LOI of 32.5%, a water contact angle of up to 117°, and is completely degradable under alkaline conditions at 120°C.

[0026] (2) The preparation method of the bio-based benzoxazine monomer modified epoxy resin of the present invention comprises adding trifunctional benzoxazine phosphate (TBP) and Priamine 1074 formed by the reaction of benzoxazine monomer (GE) with phosphorus oxychloride to bisphenol A diglycidyl ester (DGEBA) for curing. This is a method of using bio-based products as modified curing agents in the synthesis of thermosetting resins, reducing the use of petroleum-based compounds and complying with the concept of green development. The obtained bio-based benzoxazine monomer modified epoxy resin can be used in flame retardant materials, carbon fiber reinforced composite materials, adhesives, low dielectric materials and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the FT-IR spectrum of GU, EA, GE and TBP;

[0028] Figure 2 are the FT-IR patterns of TBP, DGEBA, and EP-TBP-2.46%;

[0029] Figure 3 is the DMA graph of epoxy resin modified with different proportions of bio-based benzoxazine monomer;

[0030] Figure 4 This is the tensile diagram of epoxy resin modified with different proportions of bio-based benzoxazine monomer;

[0031] Figure 5 is the TGA graph of epoxy resin modified with different proportions of bio-based benzoxazine monomer;

[0032] Figure 6 This is a shear diagram of epoxy resin modified with different proportions of bio-based benzoxazine monomer;

[0033] Figure 7 This is the UL-94 vertical burning diagram of epoxy resin modified with different proportions of bio-based benzoxazine monomer;

[0034] Figure 8 This is the water contact angle diagram of epoxy resin modified with different proportions of bio-based benzoxazine monomer before and after immersion in water for 10 days;

[0035] Figure 9 This is the dielectric property diagram of EP-TBP-2.46%;

[0036] Figure 10 FT-IR images of EP-TBP-2.46% before and after degradation in ethanolamine. DETAILED DESCRIPTION

[0037] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0038] FT-IR (Fourier transform infrared spectroscopy) was performed using a Nicolet IS50 infrared spectrometer with a scanning wavelength from 4000 cm -1 -400cm -1 .

[0039] The tensile test was carried out according to GB13022-91 standard.

[0040] Dynamic thermomechanical analysis (DMA) was performed using a TADMAQ800 dynamic thermomechanical analyzer in tensile mode. The specimens were cut into rectangular strips with a cross-section of 5 mm x 1 mm, with an 18 mm distance between the clamps. Analysis was performed at a heating rate of 3°C / min at a frequency of 1 Hz between -50 and 150°C, and changes in storage modulus, loss modulus, and tan δ were recorded.

[0041] TGA (thermogravimetric analysis) nitrogen was used as the protective gas, and the heating rate was 10°C / min, from 25°C to 800°C.

[0042] The contact angle test was performed using a Drop Meter A-200 contact angle meter.

[0043] The shear test method is as follows: First, a 100 mm x 25 mm x 1 mm stainless steel substrate was cleaned with deionized water and isopropyl alcohol. A mixture of uncured TBP, Priamine 1074, and DGEBA was then applied between two polished stainless steel substrates, bonded together to an overlap of 12.5 mm x 25 mm and a thickness of 0.2 mm, and then cured.

[0044] The UL-94 vertical burning test was conducted in accordance with ASTM D3801 on a CZF-5 burning test machine (Beijing Zhuorui Technology Co., Ltd., China) with a specimen size of 130 × 13 × 3 mm 3 .

[0045] The dielectric properties were tested using an Agilent 4294A precision impedance analyzer with a frequency range of 1 MHz to 10 MHz.

[0046] Example 1

[0047] A bio-based benzoxazine monomer, the synthesis route of which is:

[0048]

[0049] A method for preparing a bio-based benzoxazine monomer comprises the following steps:

[0050] The starting materials, 10 g of guaiacol (GU), 4.92 g of ethanolamine (EA), and 4.84 g of paraformaldehyde, were added to a round-bottom flask and reacted at 70°C for 20 h using chloroform as the solvent. After the reaction, the product was washed three times with NaOH and three times with deionized water, and then recrystallized from ethanol to obtain a white powder: bio-based benzoxazine monomer (GE).

[0051] A bio-based trifunctional benzoxazine phosphate monomer, the synthesis route of which is:

[0052]

[0053] A method for preparing a bio-based trifunctional benzoxazine phosphate monomer comprises the following steps:

[0054] Dissolve 10g of bio-based benzoxazine monomer (GE) and 4.84g of triethylamine in dichloromethane. Add 2.44g of phosphorus oxychloride dropwise in an ice-water bath at 0-5°C. Stir for 30 minutes and then allow to react at room temperature for 30 hours. After the reaction, wash three times with saturated sodium chloride and three times with deionized water. Recrystallize with ethanol to obtain a white powder: bio-based trifunctional benzoxazine phosphate monomer (TBP).

[0055] The FT-IR images of GU, EA, GE and TBP are shown in Figure 2. Figure 1 As shown, GU is at 3515cm-1 The characteristic peaks of phenolic hydroxyl group and EA at 3289 cm -1 and 3166cm -1 The amino doublet at 3377 cm -1 The alcoholic hydroxyl peak at 1210 cm -1 and 1073cm -1 The COC stretching vibration peak of the oxazine ring appears at 922 cm -1 The absorption peak at 3377 cm is the characteristic peak of the oxazine ring, which proves the successful synthesis of GE. -1 The characteristic peak of the alcoholic hydroxyl group at the position of α-Hydroxy-L ... -1 The absorption peak of PO bond appears at 1018 cm -1 The characteristic absorption peak of the oxazine ring was retained, proving that TBP was successfully synthesized by the reaction of GE and phosphorus oxychloride.

[0056] The preparation process of bio-based benzoxazine monomer modified epoxy resin is as follows:

[0057] Thoroughly mix 3.8g of bio-based trifunctional benzoxazine phosphate (TBP) and 10g of bisphenol A epoxy resin (DGEBA) in DMSO at 80°C. After thorough mixing, remove excess DMSO by rotary evaporation. Add 4.6g of Priamine 1074 and stir thoroughly. The mixture is then quickly poured into a PTFE mold. Pre-cure at 80°C for 6 hours, then cure at 120°C for 3 hours, 150°C for 3 hours, and finally at 180°C for 1 hour. The temperature is then cooled to room temperature at a rate of 6°C / min to yield a bio-based benzoxazine monomer-modified epoxy resin (EP-TBP-0.95%).

[0058] Example 2

[0059] The preparation method of bio-based trifunctional benzoxazine phosphate monomer (TBP) is based on the method described in Example 1.

[0060] The preparation process of bio-based benzoxazine monomer modified epoxy resin is as follows:

[0061] Thoroughly mix 7.6g of bio-based trifunctional benzoxazine phosphate (TBP) and 10g of bisphenol A epoxy resin (DGEBA) in DMSO at 80°C. After thorough mixing, remove excess DMSO by rotary evaporation. Add 2.3g of Priamine 1074 and stir thoroughly. The mixture is then quickly poured into a PTFE mold. Pre-cure at 80°C for 6 hours, then at 120°C for 3 hours, 150°C for 3 hours, and finally at 180°C for 1 hour. The temperature is then cooled to room temperature at a rate of 6°C / min to yield a bio-based benzoxazine monomer-modified epoxy resin (EP-TBP-1.76%).

[0062] Example 3

[0063] The preparation method of bio-based trifunctional benzoxazine phosphate monomer (TBP) is based on the method described in Example 1.

[0064] The preparation process of bio-based benzoxazine monomer modified epoxy resin is as follows:

[0065] Thoroughly mix 11.4g of bio-based trifunctional benzoxazine phosphate (TBP) and 10g of bisphenol A epoxy resin (DGEBA) in DMSO at 80°C. After thorough mixing, remove excess DMSO by rotary evaporation and quickly pour into a PTFE mold. Pre-cure at 80°C for 6 hours, then at 120°C for 3 hours, 150°C for 3 hours, and finally at 180°C for 1 hour. The mixture is then cooled to room temperature at a rate of 6°C / min to obtain a bio-based benzoxazine monomer-modified epoxy resin (EP-TBP-2.46%).

[0066] The FT-IR spectra of TBP, DGEBA and EP-TBP-2.46% are shown in Figure 2. Figure 2 As shown, EP-TBP-2.46% at 3375 cm -1 The hydroxyl absorption peak at 922 cm -1 The characteristic absorption peak of the oxazine ring at 916 cm -1 The epoxy characteristic absorption peaks at the junction completely disappeared. The changes in these characteristic peaks confirmed the successful preparation of bio-based benzoxazine monomer modified epoxy resin (EP-TBP-2.46%).

[0067] Comparative Example

[0068] The preparation process of bio-based diamine Priamine 1074 cured epoxy resin is as follows:

[0069] Thoroughly stir 6.9g of Priamine 1074 and 10g of bisphenol A epoxy resin (DGEBA) until uniformly mixed, then quickly pour into a PTFE mold. Precure at 80°C for 6 hours, then at 120°C for 3 hours, and then at 150°C for 3 hours. Then, cool to room temperature at a rate of 6°C / min to obtain the bio-based diamine Priamine 1074-cured epoxy resin (EP-TBP-0%).

[0070] DMA chart of bio-based benzoxazine monomer modified epoxy resin Figure 3 As shown in Figure a, it can be seen that the bio-based benzoxazine monomer modified epoxy resin shows a transition from glassy state to rubbery state. At 25 ° C, the storage modulus (E') of EP-TBP-2.46% is 4720MPa, while that of EP-TBP-0% is only 1188MPa, which is 1 / 4 of EP-TBP-2.46%. Figure 3 b It can be seen that with the increase of TBP content, the T g The T of EP-TBP-2.46% also increases. g The T of EP-TBP-0% is 113.7℃, which is much higher than that of EP-TBP-0%. g (56℃).

[0071] The tensile curves of epoxy resin modified with different proportions of bio-based benzoxazine monomer are shown in Figure 2. Figure 4 As shown in the figure, the tensile modulus of the bio-based benzoxazine monomer-modified epoxy resin increases with increasing TBP content, while the elongation at break decreases in the opposite direction. EP-TBP-1.76% exhibits the highest tensile strength, reaching 53 MPa. EP-TBP-2.46%, with the highest TBP content, achieves tensile strength and modulus of 49 MPa and 875 MPa, respectively. Its tensile strength and modulus are four times and 13 times higher than those of EP-TBP-0% without TBP.

[0072] The TGA graphs of epoxy resin modified with different proportions of bio-based benzoxazine monomer are shown in Figure 2. Figure 5 As shown in the figure, it can be seen that the thermal stability of the bio-based benzoxazine monomer modified epoxy resin increases with the increase of TBP addition. Compared with EP-TBP-0% without TBP, the T 5％ It increased from 192°C to 296°C, an increase of 104°C. Not only that, its carbon residue rate at 800°C (37.4%) reached 47 times that of EP-TBP-0% (0.8%). This is due to the introduction of TBP, which improves the thermal stability of the polymer.

[0073] Shear diagrams of epoxy resin modified with different proportions of bio-based benzoxazine monomers are shown in Figure 2. Figure 6As shown in the figure, it can be seen that the shear strength of the epoxy resin modified with bio-based benzoxazine monomer first increases and then decreases with the increase of TBP addition, reaching a maximum value of 9.8MPa at EP-TBP-1.76%, showing excellent adhesion to metal. This change pattern is consistent with the tensile strength.

[0074] UL-94 vertical burning test of epoxy resin modified with different proportions of bio-based benzoxazine monomers Figure 7 As shown in the figure, the flame retardancy of the bio-based benzoxazine monomer-modified epoxy resin increases with increasing TBP addition. The flame retardancy ratings of EP-TBP-0% without TBP and EP-TBP-0.95% with a phosphorus content of 0.95% are NR, indicating no flame retardancy. When the phosphorus content reaches 1.76%, EP-TBP-1.76% achieves a V-0 flame retardancy rating, with no droplet formation. This demonstrates that the addition of TBP significantly improves the flame retardancy of the polymer.

[0075] The water contact angle of the bio-based benzoxazine monomer modified epoxy resin before and after immersion in water for one week is shown in the figure below. Figure 8 As shown in the figure, the water contact angle of the bio-based benzoxazine monomer-modified epoxy resin increases with increasing TBP addition. The water contact angle of EP-TBP-2.46% is the highest before water immersion, at 117°. After one week of water immersion, the water contact angle of EP-TBP-2.46% decreases slightly to 111°. However, the water contact angle of EP-TBP-0% decreases significantly, from 92° to 77°, a decrease of 27.2%. These results demonstrate that the addition of TBP enhances the polymer's hydrophobicity.

[0076] In addition, the dielectric constant of EP-TBP-2.46% at 10 MHz is 3.5 and the dielectric loss is 0.0008 ( Figure 9 ), has good dielectric properties and is suitable for high-frequency electronic packaging materials.

[0077] The degradation process of the bio-based benzoxazine monomer-modified epoxy resin is as follows: 5 g of the sample (EP-TBP-2.46%) is added to a single-necked flask, followed by a mixed solution of 20 mL of 1N NaOH and 40 mL of ethanolamine. The temperature is raised to 120°C and stirred thoroughly. After the sample is fully degraded, the solvent is evaporated to obtain the EP-TBP-2.46% degradation product.

[0078] FT-IR images of EP-TBP-2.46% before and after degradation are shown in Figure 2. Figure 10 As shown in the figure, it can be seen that the degradation product of EP-TBP-2.46% is at 3285 cm -1 The absorption peaks at 1259 cm- -1The P=O bond absorption peak at 1182 cm -1 This indicates that the phosphate bond was amidated by ethanolamine, thus achieving rapid degradation.

[0079] The bio-based benzoxazine monomer-modified epoxy resin (EP-TBP polymer) prepared by the present invention exhibits strong mechanical properties and thermal stability, as well as excellent adhesion, flame retardancy, hydrophobicity, and biodegradability. Its room temperature tensile strength reaches 53 MPa and its tensile modulus reaches 875 MPa. The temperature for 5% thermal weight loss is above 296°C, the carbon residue at 800°C reaches 37.4%, and its UL-94 vertical flammability reaches V-0, all of which far exceed those of Priamine 1074-cured epoxy resin DGEBA (EP-TBP-0%) without the addition of benzoxazine monomer (TBP). Furthermore, the EP-TBP polymer exhibits a shear strength against metal of 9.8 MPa, a water contact angle of 117°, a dielectric loss as low as 0.0008, and rapid amidation degradation under alkaline conditions.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A bio-based benzoxazine monomer modified epoxy resin, characterized in that: Its raw material components include: bio-based benzoxazine phosphate monomer TBP, bio-based diamine Priamine 1074 and bisphenol A diglycidyl ester DGEBA; Their structural formulas are:

2. The method for preparing a bio-based benzoxazine monomer-modified epoxy resin according to claim 1, wherein: The following steps are involved: (1) reacting guaiacol, ethanolamine, and paraformaldehyde to obtain a bio-based benzoxazine monomer; (2) adding a bio-based benzoxazine monomer and phosphorus oxychloride into a solvent for reaction to obtain a bio-based benzoxazine phosphate monomer; (3) The bio-based benzoxazine phosphate monomer, bio-based diamine Priamine 1074 and bisphenol A diglycidyl ester are mixed evenly and poured into a mold, and then heated and cured to obtain a bio-based benzoxazine monomer-modified epoxy resin.

3. The method for preparing a bio-based benzoxazine monomer-modified epoxy resin according to claim 2, wherein: The reaction temperature in step (1) is 60° C. to 90° C., and the reaction time is 12 to 18 hours.

4. The method for preparing a bio-based benzoxazine monomer-modified epoxy resin according to claim 2, wherein: The reaction temperature in step (2) is 0°C to 10°C, and the reaction time is 24 to 36 hours.

5. The method for preparing a bio-based benzoxazine monomer modified epoxy resin according to claim 2, wherein: The molar ratio of the sum of the molar amount of the oxazine ring of the bio-based benzoxazine phosphate monomer and the molar amount of the active hydrogen of the bio-based diamine Priamine 1074 to the epoxy group of bisphenol A diglycidyl ester is 1:

1.

6. The method for preparing a bio-based benzoxazine monomer modified epoxy resin according to claim 2 or 5, wherein: The mass ratio of the phosphorus content of the bio-based benzoxazine phosphate monomer to the total mass of the bio-based benzoxazine phosphate monomer, the bio-based diamine Priamine 1074 and bisphenol A diglycidyl ester is 0.95:100 to 2.46:

100.

7. The method for preparing a bio-based benzoxazine monomer modified epoxy resin according to claim 2, wherein: The curing reaction in step (3) is an autocatalytic reaction system.

8. The method for preparing a bio-based benzoxazine monomer-modified epoxy resin according to claim 2, wherein: The guaiacol, paraformaldehyde and diamine Priamine 1074 are derived from lignin, biomethanol and vegetable oil respectively.

9. The method for preparing a bio-based benzoxazine monomer-modified epoxy resin according to claim 2, wherein: The temperature rising and curing procedure is: After pre-curing at 60-100°C for 4-8 hours, cure at 100-150°C for 4-6 hours, and finally cure at 150-200°C for 2-4 hours, then cool down.

10. The method for preparing a bio-based benzoxazine monomer modified epoxy resin according to claim 9, wherein: The cooling process is to cool the temperature to room temperature at a cooling rate of 5 to 8°C / min.

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