Bio-based multifunctional active nitrile resin and solvent-free green synthesis method thereof

Abstract

The invention discloses bio-based multifunctional active nitrile resin and a solvent-free green synthesis method thereof, and relates to the technical field of macromolecules. The solvent-free green synthesis method of the nitrile resin comprises the following steps: by taking bio-based phenols, phthalonitrile-containing amines and paraformaldehyde as raw materials, carrying out solvent-free melting reaction to obtain a crude product; recrystallizing the crude product in a low-boiling-point organic solvent, and drying to obtain a bio-based polyfunctional group active nitrile monomer; and pre-polymerizing the nitrile monomer, grinding, curing and molding to obtain the bio-based polyfunctional group active nitrile resin. The solvent-free green synthesis method is adopted, no solvent exists in the synthesis link, link pollution is avoided, the synthesis time is short, and the product yield is high; the obtained resin has active functional groups such as nitrile groups, benzoxazine and double bonds, integrates the structural performance characteristics of nitrile resin, benzoxazine resin and vinyl resin, is a good resin matrix of an advanced composite material, and expands the application field of the nitrile resin.

Description

Technical Field

[0001] The invention relates to the field of polymer technology, and in particular to a bio-based multi-functional active nitrile resin and a solvent-free green synthesis method thereof. Background Art

[0002] Nitrile resin is a high-performance thermosetting resin containing phthalonitrile, and it has excellent high temperature resistance, high strength, high modulus, chemical corrosion resistance, self-flaming retardant and other characteristics, and has broad application prospects in the fields of aerospace, shipbuilding, construction, electronic packaging, etc. The synthesis of nitrile resin mostly uses petroleum-based raw materials and needs to use chemical solvents that are easy to cause environmental pollution, but petroleum resources are gradually exhausted at present, and environmental pollution problems are becoming more and more serious. In order to solve these problems, researchers have synthesized a series of bio-based nitrile resins to replace petroleum-based nitrile resins. For example, patent CN106279682B discloses a kind of nitrile resin containing isosorbide structure synthesized with isosorbide as raw material, in polar solvent, with anhydrous potassium carbonate as catalyst, and 4-nitrophthalonitrile, and the nitrile resin excellent thermal performance can be suitable with petroleum-based nitrile resin. But these nitrile resins still inevitably use chemical solvents in the building-up process.

[0003] Generally, resins containing oxazine rings (a six-membered ring containing N and O) are called benzoxazine resins. Benzoxazine resin is a new type of high-performance specialty polymer with excellent high temperature resistance, mechanical properties, and flame retardancy. It is widely used in aerospace, transportation, construction and other industries. It is synthesized from phenols, amines and aldehydes through the Mannich reaction, which gives benzoxazine flexible molecular design. Researchers design benzoxazines with different functions by changing the type of phenol source, amine source or aldehyde of benzoxazine to meet the needs of various industries. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a bio-based multi-functional active nitrile resin and a solvent-free green synthesis method thereof. The solvent-free green synthesis method is adopted, and there is no solvent in the synthesis process, which avoids process pollution, shortens the synthesis time, and increases the product yield. The obtained resin has active functional groups such as nitrile, benzoxazine, and double bonds, and integrates the structural performance characteristics of nitrile resins, benzoxazine resins, and vinyl resins. It is a good resin matrix for advanced composite materials and expands the application field of nitrile resins.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a solvent-free green synthesis method of a bio-based multi-functional active nitrile resin is provided, comprising the following steps: (1) Synthesis: Bio-based phenols, phthalonitrile-containing amines and polyformaldehyde are used as raw materials, and a solvent-free melt reaction is performed to obtain a crude bio-based multi-functional active nitrile monomer product; (2) Purification: Recrystallizing the crude product of the bio-based multi-functional active nitrile monomer in a low-boiling point organic solvent, and drying to obtain the bio-based multi-functional active nitrile monomer; (3) Curing: The bio-based multi-functional active nitrile monomer is pre-polymerized and then ground, and then cured and molded to obtain a bio-based multi-functional active nitrile resin.

[0006] Furthermore, in step (1), the bio-based phenol is at least one of eugenol, isoeugenol, sesamol, schizone, resveratrol, guaiacol and magnolol.

[0007] Furthermore, in step (1), the phthalonitrile-containing amine is at least one of o- / m- / p-aminophthalonitrile, o- / m- / p-aminophenoxyphthalonitrile and bisaminophthalonitrile.

[0008] In step (1), the phthalonitrile-containing amine is 3-aminophenoxyphthalonitrile.

[0009] Furthermore, in step (1), the molar ratio of the phenol group, the amine group and the aldehyde group is 1:1:2-2.5.

[0010] Furthermore, in step (1), a solvent-free melt reaction is carried out at a temperature of 100-160°C for 2-8 hours.

[0011] Furthermore, in step (2), the low boiling point organic solvent is at least one of methanol, ethanol and ethyl acetate.

[0012] Furthermore, in step (2), the mixture is dried at 60°C and crushed.

[0013] Furthermore, in step (3), prepolymerization is performed at 200°C for 140-160 min, the powder is ground into powder after cooling, placed in a preheated mold, and cured at 200-240°C / 1-6 h, 250-290°C / 1-6 h, and 300-340°C / 1-6 h for at least one period, and demolding is performed after cooling.

[0014] Further, the product is prepolymerized at 200°C for 150 min, ground into powder after cooling, placed in a preheated mold, and cured at 200°C / 1 h, 210°C / 1 h, and 220°C / 2 h for at least one period, demolded after cooling, and placed in an oven for post-curing at 250°C / 4 h.

[0015] The present invention also provides a bio-based multi-functional active nitrile resin prepared by a solvent-free green synthesis method of the above-mentioned bio-based multi-functional active nitrile resin, the structural formula of which is as follows: Figure 1 shown.

[0016] The present invention has the following beneficial effects: 1. The present invention uses an amine containing phthalonitrile as an amine source, a bio-based phenol containing two functional groups as a phenol source, and polyformaldehyde as an aldehyde source, and uses a solvent-free method to synthesize a bio-based multi-functional active nitrile resin, which not only reduces pollution to the environment, but also expands the diversity of nitrile resins so that they can meet the needs of different fields.

[0017] 2. The present invention overcomes the need to use toxic chemical solvents in the traditional petroleum-based benzoxazine synthesis and adopts a solvent-free synthesis method, which has little pollution and is environmentally friendly.

[0018] 3. The present invention overcomes the insufficient functionality of bio-based benzoxazine, introduces phthalonitrile into benzoxazine to improve its thermal properties, and introduces other functional groups to give benzoxazine other additional functions, thereby expanding the application of bio-based benzoxazine.

[0019] 4. The bio-based multifunctional active nitrile resin of the present invention has a simple preparation process, low equipment cost, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the structural formula of bio-based multifunctional active nitrile resin; Figure 2 The hydrogen nuclear magnetic resonance spectra of the bio-based multifunctional active nitrile resins obtained in Examples 1 to 3; Figure 3 The carbon nuclear magnetic resonance spectra of the bio-based multifunctional active nitrile resins obtained in Examples 1 to 3; Figure 4 The stress-strain curves and compressive strength bar graphs of the bio-based multi-functional active nitrile resins obtained in Examples 1 to 3; Figure 5 Schematic diagram of the thermogravimetric curves of the bio-based multi-functional active nitrile resin obtained in Examples 1 to 3. DETAILED DESCRIPTION

[0021] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0022] Example 1 A bio-based multifunctional active nitrile resin and a solvent-free green synthesis method thereof, comprising the following steps: (1) Synthesis: 0.075 mol of 3-aminophenoxyphthalonitrile, 0.075 mol of eugenol and 0.1575 mol of polyformaldehyde were reacted at 100 °C for 4 h without solvent to obtain a crude product of a bio-based multifunctional active nitrile monomer; (2) Purification: The crude product of the bio-based multifunctional active nitrile monomer is recrystallized in ethanol at 70°C, cooled, dried at 60°C and crushed to obtain the bio-based multifunctional active nitrile monomer; (3) Curing: The bio-based multifunctional active nitrile monomer is prepolymerized at 200 °C for 150 min, ground into powder after cooling, placed in a preheated mold, and cured at 200 °C / 1 h, 210 °C / 1 h, and 220 °C / 2 h. After cooling, the mold is demolded and placed in an oven for post-curing at 250 °C / 4 h to obtain a bio-based multifunctional active nitrile resin.

[0023] Example 2 A bio-based multifunctional active nitrile resin and a solvent-free green synthesis method thereof, comprising the following steps: (1) Synthesis: 0.075 mol of 3-aminophenoxyphthalonitrile, 0.075 mol of eugenol and 0.1575 mol of polyformaldehyde were reacted at 120 °C for 4 h without solvent to obtain a crude product of a bio-based multifunctional active nitrile monomer; (2) Purification: The crude product of the bio-based multifunctional active nitrile monomer is recrystallized in ethanol at 70°C, cooled, dried at 60°C and crushed to obtain the bio-based multifunctional active nitrile monomer; (3) Curing: The bio-based multifunctional active nitrile monomer is prepolymerized at 200 °C for 150 min, ground into powder after cooling, placed in a preheated mold, and cured at 200 °C / 1 h, 210 °C / 1 h, and 220 °C / 2 h. After cooling, the mold is demolded and placed in an oven for post-curing at 250 °C / 4 h to obtain a bio-based multifunctional active nitrile resin.

[0024] Example 3 A bio-based multifunctional active nitrile resin and a solvent-free green synthesis method thereof, comprising the following steps: (1) Synthesis: 0.075 mol of 3-aminophenoxyphthalonitrile, 0.075 mol of eugenol and 0.1575 mol of polyformaldehyde were reacted at 140 °C for 4 h without solvent to obtain a crude product of a bio-based multifunctional active nitrile monomer; (2) Purification: The crude product of the bio-based multifunctional active nitrile monomer is recrystallized in ethanol at 70°C, cooled, dried at 60°C and crushed to obtain the bio-based multifunctional active nitrile monomer; (3) Curing: The bio-based multifunctional active nitrile monomer is prepolymerized at 200 °C for 150 min, ground into powder after cooling, placed in a preheated mold, and cured at 200 °C / 1 h, 210 °C / 1 h, and 220 °C / 2 h. After cooling, the mold is demolded and placed in an oven for post-curing at 250 °C / 4 h to obtain a bio-based multifunctional active nitrile resin.

[0025] Comparative Example 1 Petroleum-based nitrile resin: Weng Z, Song L, Qi Y, et al. Natural magnesium derivatives as platform chemicals for bio-based phthalonitrile thermoset: Achieving high performances without an external curing agent [J]. Polymer, 2021, 226: 123814. reported a biphenyl-type nitrile resin synthesized by nucleophilic substitution reaction. The resin monomer is 2,2′-dihydroxybiphenyl and tetranitrophthalonitrile as raw materials, dimethyl sulfoxide as reaction solvent, potassium carbonate as catalyst, and is synthesized at 40 °C for 48 h. The T of the biphenyl-type nitrile resin under nitrogen atmosphere 5% The temperature is 461 ℃ and the residual carbon rate is 74%.

[0026] Comparative Example 2 Petroleum-based benzoxazine: Reference Gnanapragasam S, Krishnan S, Arumugam H, et al. Synthesis and characterization of a novel high-performance benzoxazine frombenzaldehyde-based bisphenol[J]. Advances in Polymer Technology, 2018, 37(8):3056-3065. 0.2 mol of aniline, 0.1 mol of benzaldehyde-based bisphenol and 0.4 mol of polyformaldehyde were mixed and dissolved in 30 ml of 1,4-dioxane and reacted at 120 °C for 6 h to synthesize a petroleum-based benzoxazine resin monomer. The petroleum-based benzoxazine has a T of 1.3447 W under nitrogen atmosphere. 5%The temperature is 350 ℃ and the residual carbon rate is 43%.

[0027] Comparative Example 3 Petroleum-based vinyl resin: Zhang X, Wu J, Qin Z, et al. High-performance biobased vinyl ester resin with Schiff base derived from vanillin[J]. ACS Applied Polymer Materials, 2022, 4(4): 2604-2613. reported a commercial bisphenol A vinyl ester resin (VER901). Its T 5% The temperature is 381.1 ℃ and the residual carbon rate is 2.45%.

[0028] Comparative Example 4 Eugenol-type nitrile resin: Wang A, Dayo AQ, Zu L, et al. Bio-basedphthalonitrile compounds: Synthesis, curing behavior, thermomechanical and thermal properties[J]. Reactive and Functional Polymers, 2018, 127: 1-9. reported a eugenol nitrile resin prepared by using eugenol and 4-nitrophthalonitrile as raw materials, potassium carbonate as catalyst, and dimethyl sulfoxide as reaction solvent at 80 °C for 24 h. Its T 5% The temperature is 465 ℃, the residual carbon rate is 77.5%, and the tensile strength is 70.74 MPa.

[0029] Comparative Example 5 Eugenol-type benzoxazines: Thirukumaran P, Shakila Parveen A, Sarojadevi M. Synthesis and copolymerization of fully biobased benzoxazines from renewable resources [J]. ACS Sustainable Chemistry & Engineering, 2014, 2 (12): 2790-2801. reported a bio-based benzoxazines resin synthesized by a solvent-free method using eugenol as a phenol source, stearylamine as an amine source, and polyformaldehyde as an aldehyde source. Its thermal decomposition temperature (T 5%) is 313 ℃, and the residual carbon rate at 800 ℃ is 23.9%.

[0030] Comparative Example 6 Vanillin-based vinyl resin: Zhang X, Wu J, Qin Z, et al. High-performance biobased vinyl ester resin with Schiff base derived from vanillin[J]. ACS Applied Polymer Materials, 2022, 4(4): 2604-2613. reported a bio-based vinyl ester resin with Schiff base structure prepared by two-step reaction using renewable vanillin as raw material. The T 5% The temperature is 342 ℃, and the residual carbon rate at 800 ℃ is 34.4%.

[0031] Test example The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum of the bio-based multifunctional active nitrile resin (eugenol-type benzoxazine-nitrile resin monomer) obtained in Examples 1 to 3 are obtained, respectively. Figure 2 and Figure 3 At the same time, the stress-strain curves and compressive strength bar graphs of the bio-based multi-functional active nitrile resins obtained in Examples 1 to 3 were obtained, as shown in FIG. Figure 4 As shown; and obtain its thermal weight loss curve schematic diagram, such as Figure 5 shown.

[0032] Depend on Figure 2 It can be seen that the hydrogen spectra of benzoxazines synthesized at three temperatures are not much different, indicating that the structure of the synthesized substances is the same, and the purity of the substances increases with the increase of temperature. The single peak at 3.879 ppm (c) is caused by the H on -OCH3. The double peaks at 3.311 and 5.108 ppm (d and f) and the multiple peak at 5.956 ppm (e) are caused by the H on the allyl group [H2C=CH-CH2-]. The resonance peaks at 4.647 and 5.421 ppm (a and b) are caused by the two H on the oxazine ring. The peaks at 6.488-7.726 ppm are caused by the H on the benzene ring, of which the peak at 7.26 ppm is caused by the solvent deuterated chloroform.

[0033] Depend on Figure 3 It can be seen that each carbon on the synthesized monomer can be confirmed in the carbon spectrum. Combined with the hydrogen spectrum, it shows that the obtained monomer is a eugenol-type benzoxazine-nitrile resin.

[0034] Depend on Figure 4It can be seen that the strength of the bio-based multifunctional active nitrile resin is 170 MPa and above.

[0035] Depend on Figure 5 It can be seen that under nitrogen atmosphere, T 5% The highest temperature is 395 ℃, and the highest residual carbon rate at 800 ℃ is 73.2%.

[0036] The process conditions and performances of Examples 1 to 3 and Comparative Examples 1 to 6 were compared, and the results are shown in Table 1.

[0037] Table 1 Comparison of process conditions and performance As can be seen from Table 1, the present invention not only has a simple and pollution-free synthesis method and a short synthesis time, but also has good thermal properties and strength of the cured product samples.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A solvent-free green synthesis method of a bio-based multifunctional active nitrile resin, characterized in that: The following steps are involved: (1) Synthesis: Bio-based phenols, phthalonitrile-containing amines and polyformaldehyde are used as raw materials, and a solvent-free melt reaction is performed to obtain a crude bio-based multi-functional active nitrile monomer product; (2) Purification: Recrystallizing the crude product of the bio-based multi-functional active nitrile monomer in a low-boiling point organic solvent, and drying to obtain the bio-based multi-functional active nitrile monomer; (3) Curing: The bio-based multifunctional active nitrile monomer is pre-polymerized and then ground, and then cured and molded to obtain a bio-based multifunctional active nitrile resin.

2. The solvent-free green synthesis method of the bio-based multifunctional active nitrile resin according to claim 1, characterized in that: In step (1), the bio-based phenol is at least one of eugenol, isoeugenol, sesamol, schizone, resveratrol, guaiacol and magnolol.

3. The solvent-free green synthesis method of the bio-based multifunctional active nitrile resin according to claim 1, characterized in that: In step (1), the phthalonitrile-containing amine is at least one of o- / m- / p-aminophthalonitrile, o- / m- / p-aminophenoxyphthalonitrile and bis-aminophthalonitrile.

4. The solvent-free green synthesis method of the bio-based multifunctional active nitrile resin according to claim 1, characterized in that: In step (1), the molar ratio of phenol group, amine group and aldehyde group is 1:1:2-2.

5.

5. The solvent-free green synthesis method of the bio-based multifunctional active nitrile resin according to claim 1, characterized in that: In step (1), a solvent-free melt reaction is carried out at a temperature of 100-160°C for 2-8 hours.

6. The solvent-free green synthesis method of the bio-based multifunctional active nitrile resin according to claim 1, characterized in that: In step (2), the low boiling point organic solvent is at least one of methanol, ethanol and ethyl acetate.

7. The solvent-free green synthesis method of the bio-based multifunctional active nitrile resin according to claim 1, characterized in that: In step (2), the mixture is dried at 60°C and crushed.

8. The solvent-free green synthesis method of the bio-based multifunctional active nitrile resin according to claim 1, characterized in that: In step (3), prepolymerization is carried out at 200°C for 140-160 min, and the powder is ground into powder after cooling, placed in a preheated mold, and cured at 200-240°C / 1-6 h, 250-290°C / 1-6 h, and 300-340°C / 1-6 h for at least one period, and demolded after cooling.

9. A bio-based multi-functional active nitrile resin obtained by the solvent-free green synthesis method of the bio-based multi-functional active nitrile resin according to any one of claims 1 to 8.

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