A kind of lignin modified dicyclopentadiene phenol resin and preparation method thereof

Abstract

The present invention belongs to the field of functional resins and specifically relates to a lignin-modified dicyclopentadiene phenol resin and a preparation method thereof. The present invention utilizes phenol to phenolate bamboo lignin under alkaline conditions, and then uses methanesulfonic acid to catalyze the reaction of the phenolated bamboo lignin, phenol, and dicyclopentadiene to prepare the dicyclopentadiene phenol resin. This reduces the amount of phenol used in the dicyclopentadiene phenol resin and improves its heat resistance, corrosion resistance, and other properties, resulting in high bonding strength, friction resistance, and electrical insulation. Furthermore, the preparation method is simple, the reaction conditions are mild, and the production cost is low, meeting the environmental protection needs of modern society while also adhering to the principles of green chemistry and chemical atom economy.

Description

Technical Field

[0001] The invention belongs to the field of functional resins and relates to a lignin-modified dicyclopentadiene phenol resin and a preparation method thereof. Background Art

[0002] Dicyclopentadiene phenol resin is a thermoplastic resin widely used in paints, inks, and electronic packaging materials. Due to its complex structure, which includes benzene, five-membered rings, and six-membered rings, this resin exhibits excellent flame retardancy, water resistance, and electrical insulation properties, making it ideal for use in adhesives and battery packaging materials. Furthermore, dicyclopentadiene phenol resin does not release harmful gases such as formaldehyde during use and production, making it popular in the market.

[0003] Although dicyclopentadiene phenol resin has significant performance advantages, in the context of the current era of pursuing green synthesis, traditional synthesis methods are faced with certain challenges. Dicyclopentadiene phenol resin is produced by condensation reaction of dicyclopentadiene and phenol through the catalytic action of Lewis acid (AlCl3, BF3·Et2O, etc.) and protonic acid (H2SO4, etc.). BF3·Et2O (boron trifluoride etherate) is usually used as a catalyst, followed by neutralization reaction, washing the reaction with water to remove the catalyst, and finally evaporating the oligomer to obtain the final product. However, HF (hydrofluoric acid) will be produced during the removal of the catalyst by washing the reaction, corroding the equipment and requiring high instrumentation. The amount of phenol used in the manufacturing process is too much, resulting in a large amount of unreacted phenol in the final product, which not only causes a waste of resources but also may have a serious impact on the environment. This situation cannot meet the demand of modern society for environmental protection, and is also inconsistent with the principles of green chemistry and chemical atom economy.

[0004] Bamboo lignin is an amorphous biomacromolecule extracted from bamboo, belonging to the lignin family of compounds. It possesses the advantages of biomass compounds, such as biodegradability, environmental friendliness, and low toxicity. Its structure contains phenolic hydroxyl groups, similar to phenol, which provide numerous modification sites during reactions. As an excellent renewable resource, bamboo lignin is relatively inexpensive and can serve as a substitute for fossil resources, helping to reduce carbon emissions and promote green development. Therefore, bamboo lignin demonstrates great potential in the research and application of biomass synthetic resins. Summary of the Invention

[0005] To address the above problems, the present invention proposes a method for producing dicyclopentadiene phenol resin by using bamboo lignin to partially replace phenol. Bamboo lignin not only effectively replaces phenol in the reaction but also improves the performance of the resin. Because bamboo lignin is a macromolecular substance, it can effectively reduce the degree of polymerization of the cyclopentadiene resin, thereby increasing the softening point of the resin. The dicyclopentadiene phenol resin modified with bamboo lignin exhibits good corrosion resistance, thermal stability, a higher softening point, and a lower dielectric constant, meeting current demands for green chemistry and environmental protection.

[0006] In order to make the cyclopentadiene phenol resin have a higher softening point, the present invention provides a lignin-modified dicyclopentadiene phenol resin and a preparation method thereof. After bamboo lignin is phenolized under alkaline conditions, the phenolized bamboo lignin, phenol and dicyclopentadiene are reacted with methanesulfonic acid to prepare the dicyclopentadiene phenol resin. The specific steps are as follows:

[0007] (1) Phenol, bamboo lignin, and a phase transfer catalyst were added to a four-necked flask equipped with a stirrer, a condensation reflux apparatus, and a thermometer, and stirred at 70°C. A NaOH aqueous solution (concentration of 4.5 wt%) was added to adjust the pH to 12, and the mixture was heated to 95°C to 100°C with stirring, and refluxed for 1 hour.

[0008] (2) After the reaction is complete, wait for the solution to cool to room temperature, add hydrochloric acid to the solution, and adjust the pH to 2.5. Then, place the system in an open pot and continue heating to above 100°C for 0.5 hours to remove water from the system.

[0009] (3) After the above reaction is completed, dicyclopentadiene and methanesulfonic acid are added to the solution, and the mixture is refluxed at 100° C. to 140° C. (preferably 120° C.) for 3 to 6 hours (preferably 4 hours), and then cooled;

[0010] (4) The pH value is adjusted to neutral using a sodium hydroxide solution, and the obtained product is subjected to a reduced pressure dephenolization treatment to obtain a lignin-modified dicyclopentadiene phenol resin.

[0011] Furthermore, the mass ratio of phenol to bamboo lignin is 4:0.70-1.32; preferably, the mass ratio of phenol to bamboo lignin is 4:1.

[0012] Furthermore, the mass of the phase transfer catalyst is 0.8% to 0.9% of the total mass of bamboo lignin, phenol and dicyclopentadiene; and the phase transfer catalyst is cetyltrimethylammonium bromide (CTAB).

[0013] Furthermore, the mass ratio of phenol to dicyclopentadiene is 4.85-4.3:2.

[0014] Furthermore, the mass ratio of dicyclopentadiene to methanesulfonic acid is 10:0.38-1.16.

[0015] Furthermore, the vacuum degree of the reduced pressure dephenolization is -0.095 MPa, the temperature is 180-190° C., and the time is 2 hours.

[0016] The present invention uses bamboo lignin to replace part of phenol in the synthesis of dicyclopentadiene phenol resin, which can effectively reduce the amount of phenol used, thereby reducing the pollution impact of phenol and achieving green chemistry. At the same time, after phenolization of bamboo lignin, the bamboo lignin is reacted with phenol and dicyclopentadiene to prepare the dicyclopentadiene phenol resin, which effectively increases the softening point of the resin, improves the heat resistance, corrosion resistance and thermal stability of the resin, and reduces the dielectric constant. The entire reaction is simple and green, and because bamboo lignin is relatively cheap, the present reaction has better economic benefits than traditional reactions.

[0017] The advantages of the present invention are as follows:

[0018] 1. The present invention uses bamboo lignin as a raw material to replace phenol. Bamboo lignin is non-toxic, has a similar structure to phenol, is an excellent renewable resource, is relatively easy to obtain, and is relatively inexpensive. This can effectively reduce the amount of phenol used, thereby reducing phenol emissions as a pollutant. This substitution strategy conforms to the principles of green chemistry, contributes to environmentally friendly chemical production processes, and thus reduces the environmental impact of chemical production.

[0019] 2. The present invention phenolizes bamboo lignin under alkaline conditions, degrading the macromolecular structure of bamboo lignin. A small amount of bamboo lignin condenses with phenol, thereby increasing the molecular weight of the lignin, reducing the average molecular weight of the bamboo lignin and broadening the molecular weight distribution. The bamboo lignin molecule contains a guaiacyl unit (as shown in the following formula I), and one of the ortho positions of the phenolic hydroxyl group is substituted, thereby increasing the proportion of molecules with a degree of polymerization n=0 in the resin (the reaction of the guaiacyl unit with dicyclopentadiene is shown in the following formula II). The reduction in the degree of polymerization reduces the dielectric constant of the resin and simultaneously increases the softening point.

[0020] 3. The preparation method of the present invention has mild reaction conditions and is easy to operate.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the infrared spectrum of the lignin-modified dicyclopentadiene phenol resin prepared in Example 1. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the solutions of the invention, preferred embodiments of the invention will be described below in conjunction with specific examples, but this should not be construed as limiting the invention.

[0024] Unless otherwise specified, the experimental methods or test methods described in the following embodiments are all based on conventional methods; the reagents and materials are all obtained from conventional commercial channels or prepared using conventional methods unless otherwise specified.

[0025] Example 1

[0026] Take 24.2g of phenol in a four-necked flask, add 4.312g of lignin and 0.3429g of phase transfer catalyst hexadecyltrimethylammonium bromide, stir evenly at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, add hydrochloric acid dropwise, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C, maintaining for 0.5h. Add 0.7498g of methanesulfonic acid, 10g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction for 4h. After the reaction is completed, cool down and add sodium hydroxide dropwise to neutral. Use rotary evaporator to carry out vacuum distillation, vacuum degree is -0.095MPa, temperature is 180°C, time is 2h, discharging while hot, finally obtain lignin modified dicyclopentadiene phenol resin.

[0027] Figure 1 The infrared spectrum of the lignin-modified dicyclopentadiene phenol resin prepared in Example 1 is shown. Compared with the dicyclopentadiene phenol resin, the infrared spectrum at 751 cm -1 The characteristic peak of ortho-substituted lignin phenols is more obvious, and the experimental results prove that the modified lignin preparation is successful.

[0028] Example 2

[0029] Take 22.8g of phenol in a four-necked flask, add 5.7g of lignin and 0.3205g of phase-transfer catalyst hexadecyltrimethylammonium bromide, stir evenly at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, dropwise add hydrochloric acid, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C, maintaining for 0.5h. Add 0.77g of methanesulfonic acid, 10g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction 5h. After the reaction ends, cool down and add sodium hydroxide dropwise to neutral. Use rotary evaporator to carry out vacuum distillation, vacuum degree is-0.095MPa, temperature is 180°C, time is 2h, discharging while hot, finally obtain lignin-modified dicyclopentadiene phenol resin.

[0030] Example 3

[0031] Take 45.5g of phenol in a four-necked flask, add 11.4g of lignin and 0.6927g of phase transfer catalyst hexadecyltrimethylammonium bromide, stir evenly at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, add hydrochloric acid dropwise, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C, maintaining for 0.5h. Add 1.5981g of methanesulfonic acid and 20g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction for 4h. After the reaction is completed, cool down and add sodium hydroxide dropwise to neutral. Use rotary evaporator for vacuum distillation, vacuum degree is -0.095MPa, temperature is 180°C, time is 2h, discharging while hot, finally obtain lignin-modified dicyclopentadiene phenol resin.

[0032] Example 4

[0033] Take 21.5g of phenol in a four-necked flask, add 7.125g of lignin and 0.3127g of phase transfer catalyst hexadecyltrimethylammonium bromide, stir evenly at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, add hydrochloric acid dropwise, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C for 0.5h. Add 0.7594g of methanesulfonic acid and 10g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction for 4h. After the reaction is completed, cool and add sodium hydroxide dropwise to neutral. Use rotary evaporator for vacuum distillation, vacuum degree is -0.095MPa, temperature is 180°C, time is 2h, discharge while hot, and finally obtain lignin-modified dicyclopentadiene phenol resin.

[0034] Example 5

[0035] Take 24.2g of phenol in a four-necked flask, add 4.314g of lignin and 0.3458g of phase transfer catalyst hexadecyltrimethylammonium bromide, stir evenly at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, add hydrochloric acid dropwise, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C, maintaining for 0.5h. Add 0.3857g of methanesulfonic acid, 10g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction for 4h. After the reaction is completed, cool down and add sodium hydroxide dropwise to neutral. Use rotary evaporator to carry out vacuum distillation, vacuum degree is -0.095MPa, temperature is 180°C, time is 2h, discharging while hot, finally obtain lignin modified dicyclopentadiene phenol resin.

[0036] Example 6

[0037] Take 24.2g of phenol in a four-necked flask, add 4.299g of lignin and 0.3396g of phase transfer catalyst hexadecyltrimethylammonium bromide, stir evenly at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, add hydrochloric acid dropwise, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C, maintaining for 0.5h. Add 1.1558g of methanesulfonic acid and 10g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction for 4h. After the reaction is completed, cool down and add sodium hydroxide dropwise to neutral. Use rotary evaporator for vacuum distillation, vacuum degree is -0.095MPa, temperature is 180°C, time is 2h, discharging while hot, finally obtain lignin-modified dicyclopentadiene phenol resin.

[0038] Comparative Example 1

[0039] Take 19.95g of phenol in a four-necked flask, add 8.55g of lignin and 0.3295g of phase transfer catalyst hexadecyltrimethylammonium bromide, stir evenly at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, add hydrochloric acid dropwise, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C, maintaining for 0.5h. Add 1.2985g of methanesulfonic acid, 10g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction for 2h. After the reaction is completed, cool down and add sodium hydroxide dropwise to neutral. Use rotary evaporator to carry out vacuum distillation, vacuum degree is -0.095MPa, temperature is 180°C, time is 2h, discharging while hot, finally obtain lignin modified dicyclopentadiene phenol resin.

[0040] Comparative Example 2

[0041] Take 27.1g of phenol in a four-necked flask, add 1.43g of lignin, stir at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, dropwise add hydrochloric acid, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C, maintaining for 0.5h. Add 0.77g of methanesulfonic acid, 0.3423g of phase transfer catalyst hexadecyltrimethylammonium bromide, 10g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction 2h. After the reaction ends, cool down and add sodium hydroxide dropwise to neutral. Use rotary evaporator to carry out vacuum distillation, vacuum degree is-0.095MPa, temperature is 180°C, time is 2h, discharging while hot, finally obtain lignin modified dicyclopentadiene phenol resin.

[0042] Comparative Example 3

[0043] 28.5g of phenol was added to a four-necked flask, 0.77g of methanesulfonic acid, 0.3423g of a phase transfer catalyst, hexadecyltrimethylammonium bromide, and 10g of dicyclopentadiene. The mixture was stirred and heated to 120°C for 5h. After the reaction was completed, the mixture was cooled and sodium hydroxide was added dropwise until neutral. A rotary evaporator was used for vacuum distillation with a vacuum degree of -0.095MPa, a temperature of 180°C, and a time of 2h. The mixture was discharged while hot to obtain dicyclopentadiene phenol resin.

[0044] Comparative Example 4

[0045] 24.2g of phenol was placed in a four-necked flask, 4.286g of lignin and 0.3423g of a phase transfer catalyst, cetyltrimethylammonium bromide, were added, stirred at 70°C, and then a 4.5wt% NaOH aqueous solution was added to adjust the pH to 12. The mixture was heated to 100°C with stirring, refluxed under condensation, and insulated with stirring for 1 hour. After the reaction stopped, the solution was cooled to room temperature and hydrochloric acid was added dropwise to adjust the pH to 2.5. The system was left open and continued to heat, heated to 100°C, and maintained for 0.5h. 0.77g of AlCl3 and 10g of dicyclopentadiene were added, the mixture was heated to 120°C with stirring, and the reaction was stirred for 4h. After the reaction was completed, the mixture was cooled and sodium hydroxide was added dropwise until neutral. A rotary evaporator was used for vacuum distillation with a vacuum degree of -0.095MPa, a temperature of 180°C, and a time of 2h. The mixture was discharged while hot to finally obtain lignin-modified dicyclopentadiene phenol resin.

[0046] Comparative Example 5

[0047] Take 45.5g of phenol in a four-necked flask, add 11.4g of lignin and 0.6932g of phase transfer catalyst hexadecyltrimethylammonium bromide, stir evenly at 70°C, add a 4.5wt% NaOH aqueous solution to adjust the pH to 12, stir and heat to 100°C, condense and reflux, insulate and stir for 1 hour, after the reaction stops, wait for the solution to cool to room temperature, add hydrochloric acid dropwise, adjust the pH to 2.5. The system is exposed and continues to heat, warming to 100°C, maintaining for 0.5h. Add 1.53g of methanesulfonic acid, 20g of dicyclopentadiene, stirring and warming to 120°C, stirring reaction 4h. Cool after the reaction ends. Use rotary evaporator to carry out vacuum distillation, vacuum degree is-0.095MPa, temperature is 180°C, time is 2h, discharging while hot, finally obtain lignin modified dicyclopentadiene phenol resin.

[0048] The performance tests of the resins obtained in the embodiments of the present invention and the comparative examples are as follows. The softening point is measured using the LRHD-IV computerized asphalt softening point tester by the ring and ball method. The sample to be tested is placed in a sample ring placed on a metal plate. The sample ring and the metal plate are placed in an oil bath and heated until the resin melts. The temperature at which the resin just contacts the metal plate is recorded as the softening point temperature of the resin. The rotational viscosity is measured using a rotational viscometer. The free phenol in the synthesized resin is determined by gas chromatography. Instrument conditions: a hydrogen flame detector is used, the inlet temperature is 220°C, the FID detector temperature is 280°C, and the injection volume is 0.2μl. The nitrogen flow rate is 20mL / min; the hydrogen flow rate is 30mL / min; and the air flow rate is 300mL / min. The dielectric constant is measured using an Agilent 4291B radio frequency impedance analyzer. Instrument conditions: the frequency is set to 1GHz, the applied voltage is 1V, the sample is 1*1cm, and the thickness is 0.1cm. The test results are shown in Table 1.

[0049] Table 1 Properties of different resins

[0050] serial number Softening point / ℃ Rotational viscosity / P Aggregation speed / s Free phenol / % Dielectric constant Example 1 109.2 2.51 88 0.03 3.22 Example 2 127.4 2.43 87 0.02 3.15 Example 3 114.6 2.61 83 0.04 3.19 Example 4 84.3 2.46 86 0.02 3.11 Example 5 92.4 2.48 84 0.03 3.24 Example 6 110.5 2.44 86 0.03 3.21 Comparative Example 1 82.7 2.42 85 0.03 3.03 Comparative Example 2 82.3 2.39 92 0.04 3.37 Comparative Example 3 83.6 1.46 61 0.02 3.51 Comparative Example 4 64.5 2.48 84 0.03 3.28 Comparative Example 5 98 2.56 91 0.04 3.18

[0051] As can be seen from Table 1, the softening points of the examples of the present invention are all higher than those of the comparative examples, with the highest softening point of Example 2 being 127.4°C, significantly higher than that of Comparative Example 3. This indicates that the lignin-modified dicyclopentadiene phenol resin prepared using the present invention can significantly increase the softening point and has excellent heat resistance. The dielectric constants of the lignin-modified dicyclopentadiene phenol resins prepared in the examples are all lower than that of Comparative Example 3, which is not modified with lignin. This demonstrates that the dicyclopentadiene phenol resin modified with lignin significantly reduces the degree of polymerization of the resin, resulting in the product having better electrical insulation properties and lower dielectric loss.

[0052] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for preparing lignin-modified dicyclopentadiene phenol resin, characterized in that: The steps include: (1) Phenol, bamboo lignin, and a phase transfer catalyst were added to a container equipped with a stirrer, a condensation reflux device, and a thermometer, and stirred at 70°C. A NaOH aqueous solution was added to adjust the pH to 12, and the mixture was heated to 95°C to 100°C with stirring, and the mixture was refluxed for 1 hour. (2) After the solution has cooled to room temperature, hydrochloric acid is added to the solution to adjust the pH to 2.

5. The system is then placed in an open pot and heated to above 100°C to remove water from the system. (3) After the above reaction is completed, dicyclopentadiene and a catalyst are added to the solution, and the mixture is refluxed at 100° C. to 140° C. for 3 to 6 hours, and then cooled; (4) adjusting the pH to neutral using a sodium hydroxide solution, and subjecting the obtained product to a reduced pressure dephenolization treatment to obtain a lignin-modified dicyclopentadiene phenol resin; The phase transfer catalyst in step (1) is hexadecyltrimethylammonium bromide; The catalyst in step (3) is methanesulfonic acid.

2. The method for preparing the lignin-modified dicyclopentadiene phenol resin according to claim 1, wherein The concentration of the NaOH aqueous solution in step (1) is 4.5 wt %.

3. The method for preparing the lignin-modified dicyclopentadiene phenol resin according to claim 1, wherein: The mass ratio of phenol to bamboo lignin in step (1) is 4:0.70-1.

32.

4. The method for preparing the lignin-modified dicyclopentadiene phenol resin according to claim 1, wherein: The mass of the phase transfer catalyst in step (1) is 0.8-0.9% of the total mass of bamboo lignin, phenol and dicyclopentadiene.

5. The method for preparing the lignin-modified dicyclopentadiene phenol resin according to claim 1, wherein: In step (3), the mass ratio of phenol to dicyclopentadiene is 4.85-4.3:2; And / or, the mass ratio of dicyclopentadiene to catalyst is 10:0.38~1.

16.

6. The method for preparing the lignin-modified dicyclopentadiene phenol resin according to claim 1, wherein: The vacuum degree of the decompression dephenolization in step (4) is -0.095 MPa, the temperature is 180-190° C., and the time is 2 h.

7. A lignin-modified dicyclopentadiene phenol resin prepared according to the method according to any one of claims 1 to 6.

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