Environment-friendly phenolic resin and preparation method thereof

Abstract

The preparation method comprises the following steps: mixing phenol and paraformaldehyde according to a molar ratio of 1: (0.5-0.7), heating to 45-50 DEG C, carrying out 300-400W microwave irradiation for 5-6 minutes, then adding lithium hydroxide, stirring for 8-10 minutes at 300-400r / min, continuously heating to 75-80 DEG C, adding a magnesium oxide-mesoporous carbon composite material, and carrying out heat preservation reaction under the condition of a pulsed magnetic field to obtain a phenolic prepolymer; and adding urea, triethylene tetramine and triethanolamine into the phenolic prepolymer, carrying out electron beam irradiation treatment, carrying out a heating reaction, and carrying out post-treatment. The preparation method disclosed by the invention is green and environment-friendly, the content of free phenol and free aldehyde in the generated wastewater is low, and the content of free phenol and free aldehyde in the product phenolic resin is low.

Description

Technical Field

[0001] The present invention relates to an environment-friendly phenolic resin and a preparation method thereof, belonging to the technical field of polymer materials. Background Art

[0002] Phenolic resin is a polymer compound with excellent properties, which is obtained by the condensation reaction of phenolic compounds and aldehyde compounds. Phenolic resin can maintain structural stability at high temperatures, is not easily decomposed or deformed, and can be widely used in high-temperature working environments. Phenolic resin has high strength and hardness, and has broad application prospects in mechanical parts and structural materials. In addition, phenolic resin is easy to process and can be processed into products of various shapes and sizes through various molding processes such as injection molding, pressing, and coating to meet the needs of different fields.

[0003] However, during the synthesis of phenolic resin, wastewater containing free phenol and free aldehyde is generated, which is extremely harmful to the environment. Taking free phenol as an example, low-concentration phenol can denature proteins, and high-concentration phenol can precipitate proteins. In severe cases, it can inhibit the central nervous system or damage liver and kidney functions, and strongly corrode the skin and mucous membranes. In addition, the residual free aldehyde in phenolic resin products will also endanger human health. The treatment of wastewater containing free phenol and free aldehyde is difficult, the treatment process is complex, and the cost is high, which affects the development of the phenolic resin production industry. If the generation of wastewater containing free phenol and free aldehyde can be reduced during the synthesis of phenolic resin, it will undoubtedly greatly relieve the production pressure of enterprises.

[0004] Patent CN102417570B discloses a preparation method of green phenolic resin, which includes the following steps:

[0005] (1) After dissolving 20-50 kg of phenol, add it into the reaction kettle. After steam heating, add 30-50 kg of formaldehyde. When the temperature in the reaction kettle rises to 45-55 °C, add 4.5-6 kg of catalyst, immediately cover the feeding hole. The temperature in the reaction kettle rises automatically due to exothermic reaction. Turn off the steam for heating. When the temperature in the reaction kettle rises to 96-98 °C, appropriately cool the jacket of the reaction kettle to avoid excessive temperature and pressure in the reaction kettle caused by severe exothermic reaction and poor heat dissipation, resulting in explosion polymerization. When the temperature in the reaction kettle drops to 90 °C, keep it warm for 1 hour and cool it below 40 °C to prepare a pre-condensed phenolic resin with very low molecular weight for standby;

[0006] (2) Add 15 - 30 kg of pre - condensed phenolic resin into the reaction kettle. After heating with steam, add 60 - 142 kg of formaldehyde and stir. When the temperature in the reaction kettle rises to 40 - 50 °C, add 19 - 39 kg of urea, 6 - 10 kg of melamine and 0.5 - 4 kg of catalyst. After feeding, immediately cover the feeding hole. Gradually raise the temperature in the reaction kettle to 65 - 75 °C and maintain for 15 - 30 minutes. Then raise the temperature in the reaction kettle to 85 - 92 °C and maintain for 1 hour and 30 minutes. Then carry out vacuum dehydration to obtain green phenolic resin.

[0007] This patented technology controls the reaction exotherm by gradually increasing the reaction temperature, enabling the raw materials to react fully, improving the uniformity of the product, and reducing the content of low - molecular - weight resin and raw materials. However, the free formaldehyde content in the finally obtained phenolic resin product can only be controlled to be less than 2.0%, which is still not ideal. Moreover, this patented technology cannot effectively reduce the free phenol content in the product, and the free phenol and free formaldehyde contents in the generated wastewater are also relatively high. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies of the above - mentioned existing technologies and provide an environmentally friendly phenolic resin and its preparation method, which is green and environmentally friendly.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions:

[0010] A preparation method of an environmentally friendly phenolic resin, the specific steps are as follows:

[0011] (1) First, mix phenol and paraformaldehyde according to a molar ratio of 1:0.5 - 0.7 and heat to 45 - 50 °C, irradiate with 300 - 400 W of microwave for 5 - 6 minutes. Then add lithium hydroxide and stir at 300 - 400 r / min for 8 - 10 minutes. Continue to heat to 75 - 80 °C, add magnesium oxide - mesoporous carbon composite material, and carry out heat - preservation reaction under pulsed magnetic field conditions to obtain a phenolic prepolymer;

[0012] (2) Then add urea, triethylenetetramine and triethanolamine to the phenolic prepolymer, carry out electron beam irradiation treatment, heat and react, and carry out post - treatment to obtain the phenolic resin.

[0013] Preferably, in step (1), the mixing heating rate is 8 - 10 °C / min, and the continuous heating rate is 3 - 5 °C / min.

[0014] Preferably, in step (1), the dosages of lithium hydroxide and magnesium oxide - mesoporous carbon composite material are 1 - 1.2% and 0.5 - 0.7% of the mass of phenol respectively.

[0015] Preferably, in step (1), the pulsed magnetic field conditions are: magnetic field strength 10 - 15 T, pulse width 8 - 10 ms, pulse interval 20 - 30 s.

[0016] Preferably, in step (1), the heat preservation reaction time is 4 to 5 hours.

[0017] Preferably, in step (1), the magnesium oxide-mesoporous carbon composite material is prepared by the following method: First, stir and dissolve magnesium nitrate in deionized water, then add mesoporous carbon, stir at room temperature (25 °C), stir and evaporate to dryness under water bath heating conditions, and dry to obtain a precursor. Finally, transfer the precursor to a tube furnace and calcine it under a nitrogen atmosphere to obtain the product.

[0018] More preferably, the dosage ratio of magnesium nitrate, deionized water, and mesoporous carbon is 0.5 to 0.7 g: 20 to 25 mL: 3 to 4 g, and the specific surface area of the mesoporous carbon is 1500 to 1700 m 2 / g, and the pore diameter is 8 to 10 nm.

[0019] More preferably, the stirring time at room temperature is 2 to 3 hours, and the water bath heating condition is 60 to 70 °C.

[0020] More preferably, the drying process conditions are: drying at 80 to 85 °C for 5 to 6 hours.

[0021] More preferably, the calcination process conditions are: calcination at 500 to 550 °C for 5 to 6 hours.

[0022] Preferably, in step (2), the mass ratio of the phenolic prepolymer, urea, triethylenetetramine, and triethanolamine is 10: 1 to 2: 0.5 to 0.7: 0.2 to 0.3.

[0023] Preferably, in step (2), 1Mev electron beam irradiation is used, and the total dose is 5 to 8 kGy.

[0024] Preferably, in step (2), the process conditions for the heating reaction are: reaction at 70 to 80 °C for 2 to 3 hours.

[0025] Preferably, in step (2), the post-treatment includes: adding acid to neutralize to neutral, filtering to obtain the solid, washing with water, and vacuum dehydrating.

[0026] More preferably, 0.5 mol / L hydrochloric acid solution is used for neutralization.

[0027] An environmentally friendly phenolic resin is obtained by the foregoing preparation method.

[0028] The beneficial effects of the present invention:

[0029] In the present invention, phenol and paraformaldehyde are first mixed in a molar ratio of 1:0.5 - 0.7 and heated to 45 - 50 °C, irradiated with microwave at 300 - 400 W for 5 - 6 minutes. Then lithium hydroxide is added, and stirred at 300 - 400 r / min for 8 - 10 minutes. It is continuously heated to 75 - 80 °C, and magnesium oxide - mesoporous carbon composite material is added, and the reaction is carried out under the condition of pulsed magnetic field to obtain a phenolic prepolymer. Then urea, triethylenetetramine and triethanolamine are added to the phenolic prepolymer, irradiated with electron beam, heated and reacted, and then post - treated. The preparation method of the present invention is green and environmentally friendly, the content of free phenol and free aldehyde in the generated wastewater is low, and the content of free phenol and free aldehyde in the product phenolic resin is low.

[0030] The present invention uses phenol and paraformaldehyde as raw materials, and prepares phenolic resin by polymerization reaction under the action of an alkaline catalyst. In the present invention, different alkaline catalysts are added step by step. Lithium hydroxide is added at a lower temperature first, and then magnesium oxide - mesoporous carbon composite material is added after heating to a higher temperature, controlling the polymerization rate, promoting the full reaction of raw materials, and fundamentally reducing the residues of free phenol and free aldehyde in wastewater and products. Compared with conventional alkaline catalysts, due to the existence of porous structure, magnesium oxide - mesoporous carbon composite material also helps the adsorption of raw materials and site - specific catalytic polymerization, which is beneficial to the full reaction of raw materials. And, the reaction is further promoted by carrying out the reaction under the condition of pulsed magnetic field.

[0031] In the present invention, urea, triethylenetetramine and triethanolamine are added to the phenolic prepolymer, and through electron beam irradiation treatment, the reaction activity is improved, the formation of phenolic resin is promoted, and the residues of free phenol and free aldehyde in wastewater and products are reduced. Detailed implementation mode

[0032] The present invention will be further elaborated below in combination with embodiments. It should be noted that the following description is only for explaining the present invention and does not limit its content.

[0033] Example 1:

[0034] A preparation method of an environmentally friendly phenolic resin is as follows:

[0035] (1) First, phenol and paraformaldehyde are mixed in a molar ratio of 1:0.5 and heated to 45 °C, irradiated with microwave at 300 W for 5 minutes. Then lithium hydroxide is added, and stirred at 300 r / min for 8 minutes. It is continuously heated to 75 °C, and magnesium oxide - mesoporous carbon composite material is added, and the reaction is carried out under the condition of pulsed magnetic field to obtain a phenolic prepolymer;

[0036] The mixing heating rate is 8 °C / min, and the continuous heating rate is 3 °C / min.

[0037] The dosages of lithium hydroxide and magnesium oxide - mesoporous carbon composite material are 1% and 0.5% of the mass of phenol respectively.

[0038] The pulsed magnetic field conditions are as follows: magnetic field strength 10 T, pulse width 8 ms, pulse interval 20 s.

[0039] The heat preservation reaction time is 4 hours.

[0040] The magnesium oxide-mesoporous carbon composite material is prepared by the following method: First, magnesium nitrate is stirred and dissolved in deionized water, then mesoporous carbon is added, and stirred at room temperature (25 °C) for 2 hours, stirred and evaporated to dryness under the condition of water bath heating at 60 °C, dried at 80 °C for 5 hours to obtain a precursor. Finally, the precursor is transferred to a tubular furnace and calcined at 500 °C for 5 hours in a nitrogen atmosphere to obtain the product. The dosage ratio of magnesium nitrate, deionized water, and mesoporous carbon is 0.5 g: 20 mL: 3 g, and the specific surface area of the mesoporous carbon is 1500 m 2 / g, and the pore diameter is 8 nm.

[0041] (2) Then, 0.1 kg of urea, 0.05 kg of triethylenetetramine, and 0.02 kg of triethanolamine are added to 1 kg of phenolic prepolymer, followed by electron beam irradiation treatment, heating reaction, and post-treatment to obtain the phenolic resin.

[0042] Irradiation is carried out with a 1 MeV electron beam, and the total dose is 5 kGy.

[0043] The process conditions for the heating reaction are: reaction at 70 °C for 2 hours.

[0044] The post-treatment includes: neutralizing with 0.5 mol / L hydrochloric acid solution to neutrality, filtering to obtain the solid, washing with water, and vacuum dehydration.

[0045] Example 2:

[0046] A preparation method of an environment-friendly phenolic resin is as follows:

[0047] (1) First, phenol and paraformaldehyde are mixed in a molar ratio of 1:0.7 and heated to 50 °C, irradiated with 400 W microwave for 6 minutes, then lithium hydroxide is added, stirred at 400 r / min for 10 minutes, and continuously heated to 80 °C. Then, the magnesium oxide-mesoporous carbon composite material is added, and heat preservation reaction is carried out under pulsed magnetic field conditions to obtain a phenolic prepolymer;

[0048] The mixing heating rate is 10 °C / min, and the continuous heating rate is 5 °C / min.

[0049] The dosages of lithium hydroxide and the magnesium oxide-mesoporous carbon composite material are 1.2% and 0.7% of the mass of phenol, respectively.

[0050] The pulsed magnetic field conditions are as follows: magnetic field strength 15 T, pulse width 10 ms, pulse interval 30 s.

[0051] The heat preservation reaction time is 5 hours.

[0052] The magnesium oxide-mesoporous carbon composite material is prepared by the following method: First, magnesium nitrate is stirred and dissolved in deionized water, then mesoporous carbon is added, and the mixture is stirred at room temperature (25 °C) for 3 hours, stirred and evaporated to dryness under the condition of water bath heating at 70 °C, dried at 85 °C for 6 hours to obtain a precursor. Finally, the precursor is transferred to a tubular furnace and calcined at 550 °C for 6 hours in a nitrogen atmosphere to obtain the product. The dosage ratio of magnesium nitrate, deionized water, and mesoporous carbon is 0.7 g: 25 mL: 4 g. The specific surface area of the mesoporous carbon is 1700 m 2 / g, and the pore diameter is 10 nm.

[0053] (2) Then, 0.2 kg of urea, 0.07 kg of triethylenetetramine, and 0.03 kg of triethanolamine are added to 1 kg of phenolic prepolymer, and the mixture is subjected to electron beam irradiation treatment, heated for reaction, and post-treated to obtain the phenolic resin.

[0054] Irradiation is carried out using a 1 MeV electron beam, and the total dose is 8 kGy.

[0055] The process conditions for the heating reaction are: reaction at 80 °C for 3 hours.

[0056] The post-treatment includes: neutralizing with 0.5 mol / L hydrochloric acid solution to neutrality, filtering to obtain the solid, washing with water, and vacuum dehydrating.

[0057] Example 3:

[0058] A preparation method of an environmentally friendly phenolic resin, the specific steps are as follows:

[0059] (1) First, phenol and paraformaldehyde are mixed in a molar ratio of 1:0.5 and heated to 50 °C, irradiated with 300 W microwave for 6 minutes, then lithium hydroxide is added, stirred at 300 r / min for 10 minutes, continuously heated to 75 °C, and a magnesium oxide-mesoporous carbon composite material is added, and heat preservation reaction is carried out under the condition of pulsed magnetic field to obtain a phenolic prepolymer;

[0060] The mixing heating rate is 10 °C / min, and the continuous heating rate is 3 °C / min.

[0061] The dosages of lithium hydroxide and magnesium oxide-mesoporous carbon composite material are 1.2% and 0.5% of the mass of phenol respectively.

[0062] The pulsed magnetic field conditions are: magnetic field strength 15 T, pulse width 8 ms, pulse interval 30 s.

[0063] The heat preservation reaction time is 4 hours.

[0064] The magnesium oxide-mesoporous carbon composite material is prepared by the following method: First, magnesium nitrate is stirred and dissolved in deionized water, then mesoporous carbon is added, and the mixture is stirred at room temperature (25 °C) for 3 hours, stirred and evaporated to dryness under a water bath heating condition of 60 °C, and dried at 85 °C for 5 hours to obtain a precursor. Finally, the precursor is transferred to a tubular furnace and calcined at 550 °C for 5 hours under a nitrogen atmosphere to obtain the product. The dosage ratio of magnesium nitrate, deionized water, and mesoporous carbon is 0.7 g: 20 mL: 4 g, and the specific surface area of the mesoporous carbon is 1500 m 2 / g, and the pore diameter is 10 nm.

[0065] (2) Then, 0.1 kg of urea, 0.07 kg of triethylenetetramine, and 0.02 kg of triethanolamine are added to 1 kg of phenolic prepolymer, and the mixture is subjected to electron beam irradiation treatment, heated for reaction, and post-treated to obtain the phenolic resin.

[0066] Irradiation is carried out using a 1 MeV electron beam, and the total dose is 5 kGy.

[0067] The process conditions for the heating reaction are: reaction at 70 °C for 3 hours.

[0068] The post-treatment includes: neutralizing with a 0.5 mol / L hydrochloric acid solution to neutrality, filtering to obtain the solid, washing with water, and vacuum dehydrating.

[0069] Example 4:

[0070] A preparation method of an environmentally friendly phenolic resin, the specific steps are as follows:

[0071] (1) First, phenol and paraformaldehyde are mixed in a molar ratio of 1:0.6 and heated to 48 °C, irradiated with 400 W of microwave for 5 minutes, then lithium hydroxide is added, stirred at 400 r / min for 9 minutes, continuously heated to 77 °C, and a magnesium oxide-mesoporous carbon composite material is added, and the reaction is carried out under insulation under pulsed magnetic field conditions to obtain a phenolic prepolymer;

[0072] The mixing heating rate is 9 °C / min, and the continuous heating rate is 4 °C / min.

[0073] The dosages of lithium hydroxide and the magnesium oxide-mesoporous carbon composite material are 1.1% and 0.6% of the mass of phenol, respectively.

[0074] The pulsed magnetic field conditions are: magnetic field strength 12 T, pulse width 9 ms, and pulse interval 25 s.

[0075] The insulation reaction time is 4 hours.

[0076] The magnesium oxide-mesoporous carbon composite material is prepared by the following method: First, magnesium nitrate is stirred and dissolved in deionized water, then mesoporous carbon is added, and the mixture is stirred at room temperature (25 °C) for 2 hours, stirred and evaporated to dryness under the condition of water bath heating at 65 °C, and dried at 82 °C for 5 hours to obtain a precursor. Finally, the precursor is transferred to a tubular furnace and calcined at 520 °C for 5 hours in a nitrogen atmosphere to obtain the product. The dosage ratio of magnesium nitrate, deionized water, and mesoporous carbon is 0.6 g: 22 mL: 3.5 g, and the specific surface area of the mesoporous carbon is 1600 m 2 / g, and the pore diameter is 9 nm.

[0077] (2) Then, 0.15 kg of urea, 0.06 kg of triethylenetetramine, and 0.01 kg of triethanolamine are added to 1 kg of phenolic prepolymer, and electron beam irradiation treatment, heating reaction, and post-treatment are carried out to obtain the phenolic resin.

[0078] Irradiation is carried out using a 1 MeV electron beam, and the total dose is 7 kGy.

[0079] The process conditions for the heating reaction are: reacting at 75 °C for 2.5 hours.

[0080] The post-treatment includes: neutralizing with 0.5 mol / L hydrochloric acid solution to neutrality, filtering to obtain the solid, washing with water, and vacuum dehydrating.

[0081] Comparative Example 1

[0082] A preparation method of an environmentally friendly phenolic resin is as follows:

[0083] (1) First, phenol and paraformaldehyde are mixed in a molar ratio of 1:0.5 and heated to 45 °C, irradiated with 300 W of microwave for 5 minutes, then lithium hydroxide is added, and the mixture is stirred at 300 r / min for 8 minutes, and then heated to 75 °C and kept reacting under the condition of pulsed magnetic field to obtain a phenolic prepolymer;

[0084] The mixing heating rate is 8 °C / min, and the continued heating rate is 3 °C / min.

[0085] The dosage of lithium hydroxide is 1% of the mass of phenol.

[0086] The pulsed magnetic field conditions are: magnetic field strength 10 T, pulse width 8 ms, and pulse interval 20 s.

[0087] The holding reaction time is 4 hours.

[0088] (2) Then, 0.1 kg of urea, 0.05 kg of triethylenetetramine, and 0.02 kg of triethanolamine are added to 1 kg of phenolic prepolymer, and electron beam irradiation treatment, heating reaction, and post-treatment are carried out to obtain the phenolic resin.

[0089] Irradiation is carried out using a 1 MeV electron beam, and the total dose is 5 kGy.

[0090] The process conditions for the heating reaction are: reacting at 70 °C for 2 hours.

[0091] The post-treatment includes: neutralizing to neutral with 0.5 mol / L hydrochloric acid solution, filtering to obtain the solid, washing with water, and vacuum dehydrating.

[0092] Comparative Example 2

[0093] A preparation method of an environmentally friendly phenolic resin, the specific steps are as follows:

[0094] (1) First, mix phenol and paraformaldehyde in a molar ratio of 1:0.5, heat to 45 °C, irradiate with 300 W microwave for 5 minutes, then add lithium hydroxide, stir at 300 r / min for 8 minutes, continue to heat to 75 °C, add magnesium oxide-mesoporous carbon composite material, and carry out a holding reaction under pulsed magnetic field conditions to obtain a phenolic prepolymer;

[0095] The mixing heating rate is 8 °C / min, and the continued heating rate is 3 °C / min.

[0096] The dosages of lithium hydroxide and magnesium oxide-mesoporous carbon composite material are 1% and 0.5% of the mass of phenol, respectively.

[0097] The pulsed magnetic field conditions are: magnetic field strength 10 T, pulse width 8 ms, pulse interval 20 s.

[0098] The holding reaction time is 4 hours.

[0099] The magnesium oxide-mesoporous carbon composite material is prepared by the following method: first, stir and dissolve magnesium nitrate in deionized water, then add mesoporous carbon, stir at room temperature (25 °C) for 2 hours, stir and evaporate to dryness under the condition of 60 °C water bath heating, dry at 80 °C for 5 hours to obtain a precursor, and finally transfer the precursor to a tubular furnace, and calcine at 500 °C for 5 hours in a nitrogen atmosphere to obtain it. The dosage ratio of magnesium nitrate, deionized water, and mesoporous carbon is 0.5 g:20 mL:3 g, and the specific surface area of the mesoporous carbon is 1500 m 2 / g, pore diameter 8 nm.

[0100] (2) Then add 0.1 kg of urea, 0.05 kg of triethylenetetramine, and 0.02 kg of triethanolamine to 1 kg of phenolic prepolymer, carry out a heating reaction and post-treatment to obtain the phenolic resin described.

[0101] The process conditions for the heating reaction are: reacting at 70 °C for 2 hours.

[0102] The post-treatment includes: neutralizing to neutral with 0.5 mol / L hydrochloric acid solution, filtering to obtain the solid, washing with water, and vacuum dehydrating.

[0103] Test Example

[0104] The wastewater generated during the preparation processes of Examples 1 to 4 and Comparative Examples 1 and 2 was collected separately, and the contents of free phenol and free aldehyde in the wastewater were detected. Also, the contents of free phenol and free aldehyde in the obtained phenolic resin products were detected. The results are shown in Table 1 and Table 2.

[0105] Among them, for the content of free aldehyde, referring to GB / T 18582-2020, the content of free formaldehyde was detected by the acetylacetone spectrophotometric method; for the content of free phenol, referring to GB / T 31604.46-2023, the content of free phenol was detected.

[0106] Table 1. Contents of free phenol and free aldehyde in wastewater

[0107] Free phenol content in wastewater (%) Free aldehyde content in wastewater (%) Example 1 0.10 0.05 Example 2 0.09 0.05 Example 3 0.08 0.04 Example 4 0.08 0.03 Comparative Example 1 2.32 2.29 Comparative Example 2 1.95 1.88

[0108] Table 2. Contents of free phenol and free aldehyde in phenolic resin

[0109] Free phenol content in phenolic resin (%) Free aldehyde content in phenolic resin (%) Example 1 0.05 0.02 Example 2 0.05 0.02 Example 3 0.04 0.02 Example 4 0.03 ＜0.01 Comparative Example 1 1.25 1.24 Comparative Example 2 1.07 1.03

[0110] As can be seen from Table 1 and Table 2, the contents of free phenol and free aldehyde in the wastewater obtained during the preparation processes of Examples 1 to 4 are low, and the contents of free phenol and free aldehyde in the obtained phenolic resin products are low, which is green and environmentally friendly.

[0111] In Comparative Example 1, the magnesium oxide-mesoporous carbon composite material was omitted, and in Comparative Example 2, the electron beam irradiation treatment was omitted. The contents of free phenol and free aldehyde in both the wastewater and the phenolic resin products increased significantly. This shows that the combined use of the basic catalysts and the synergistic effects of necessary pulsed magnetic field treatment, electron beam irradiation treatment, etc. adopted in the present invention promote the full reaction of the raw materials and reduce the generation of free phenol and free aldehyde.

[0112] Although the specific implementation manners of the present invention have been described above, it is not a limitation to the protection scope of the present invention. Based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A method for preparing an environmentally friendly phenolic resin, characterized in that: The specific steps are as follows: (1) firstly, phenol and paraformaldehyde are mixed in a molar ratio of 1:0.5-0.7, heated to 45-50°C, and irradiated with microwaves at 300-400W for 5-6 minutes, then lithium hydroxide is added, stirred at 300-400r / min for 8-10 minutes, and then heated to 75-80°C, magnesium oxide-mesoporous carbon composite material is added, and the mixture is kept warm for reaction under pulsed magnetic field conditions to obtain a phenolic prepolymer; (2) Then, urea, triethylenetetramine and triethanolamine are added to the phenolic prepolymer, and the phenolic prepolymer is irradiated with an electron beam, heated for reaction, and post-treated to obtain the phenolic resin.

2. The preparation method according to claim 1, characterized in that: In step (1), the mixing heating rate is 8 to 10°C / min, and the continued heating rate is 3 to 5°C / min.

3. The preparation method according to claim 1, characterized in that: In step (1), the amounts of lithium hydroxide and magnesium oxide-mesoporous carbon composite material used are 1-1.2% and 0.5-0.7% of the mass of phenol, respectively.

4. The preparation method according to claim 1, characterized in that: In step (1), the pulse magnetic field conditions are: magnetic field intensity 10-15T, pulse width 8-10ms, and pulse interval 20-30s.

5. The preparation method according to claim 1, characterized in that: In step (1), the heat preservation reaction time is 4 to 5 hours.

6. The preparation method according to claim 1, characterized in that: In step (1), the magnesium oxide-mesoporous carbon composite material is prepared by the following method: first, magnesium nitrate is stirred and dissolved in deionized water, then the mesoporous carbon is added, stirred at room temperature, stirred and evaporated under heating conditions in a water bath, and dried to obtain a precursor, and finally the precursor is transferred to a tubular furnace and calcined under a nitrogen atmosphere to obtain the precursor.

7. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of phenolic prepolymer, urea, triethylenetetramine and triethanolamine is 10:1-2:0.5-0.7:0.2-0.

3.

8. The preparation method according to claim 1, characterized in that: In step (2), 1 MeV electron beam irradiation is used, and the total dose is 5 to 8 kGy.

9. The preparation method according to claim 1, characterized in that: In step (2), the process conditions for the heating reaction are: 70-80° C. for 2-3 hours.

10. An environmentally friendly phenolic resin, characterized in that: The invention is obtained by the preparation method according to any one of claims 1 to 9.