Production process of environment-friendly phenolic resin

Abstract

The application discloses a production process of environment-friendly phenolic resin and belongs to the technical field of high polymer material preparation. In the application, modified lignin is used to replace part of phenol which is expensive and toxic in the reaction, and the replacement rate of the modified lignin is more than 50%; and non-toxic glyoxal is used to replace part of formaldehyde in the reaction, so that the use amount of the formaldehyde is reduced; and the obtained phenolic resin has a free phenol content of less than 1% and a free formaldehyde content of less than 0.3%.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation technology, specifically to a production process for an environmentally friendly phenolic resin. Background Technology

[0002] Phenolic resin, also known as Bakelite powder, is an important type of synthetic resin. It possesses excellent acid resistance, mechanical properties, and heat resistance, and has wide applications in the chemical and materials fields. Its synthesis primarily involves the condensation reaction of phenol and aldehyde. These raw materials are all derived from petroleum products, making them not only expensive but also non-renewable. Current phenolic resin production processes involve the addition of large amounts of phenol and formaldehyde, which are carcinogenic, and the release of free aldehydes during production and application can negatively impact human health.

[0003] Therefore, providing an environmentally friendly production process for phenolic resin is of great significance. Summary of the Invention

[0004] Based on the problems existing in the background technology, the present invention provides an environmentally friendly production process for phenolic resin, which uses renewable modified lignin and non-toxic ethylene glycol to replace part of the phenol and formaldehyde in the reaction, thereby reducing the amount of toxic substances used and reducing the burden on the environment.

[0005] This invention is implemented through the following technical solutions: This invention discloses a production process for environmentally friendly phenolic resin, comprising the following steps: S1. Lignin modification: Dissolve lignin in sodium hydroxide solution, add urea, stir to react, and after the reaction is complete, use hydrochloric acid solution to adjust the pH of the reaction solution to neutral. Separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin. S2. Add modified lignin, phenol and pure water to reactor 1, heat to 65-75℃ and stir for 1-2 hours to obtain reactant A; S3. Add phenol, pure water and sodium hydroxide to reactor 2, heat to 65-80℃, add formaldehyde and glyoxal mixture dropwise, and continue stirring the reaction for 1-1.5h after the addition is complete to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, add toughening agent, stir and react for 1-1.5 h, adjust the temperature of reactor 2 to 90-100℃, continue to add formaldehyde and glyoxal mixture dropwise, stir and react for 1-1.5 h, cool to room temperature, and distill the product under reduced pressure to prepare environmentally friendly phenolic resin.

[0006] Furthermore, the lignin in step S1 is alkali lignin.

[0007] Further, in step S1, the concentration of sodium hydroxide solution is 8-10%, and the mass ratio of lignin, sodium hydroxide solution and urea is (30-40):(50-60):(6-8).

[0008] Further, in step S2, the mass ratio of modified lignin, phenol and pure water is (50-70):(25-35):(50-60).

[0009] Further, in step S3, the mass ratio of phenol, pure water and sodium hydroxide is (20-30):(5-10):(0.8-1).

[0010] Further, the mass ratio of the formaldehyde and glyoxal mixture in step S3 to the phenol in step S3 is (20-30):(20-30); the mass ratio of formaldehyde to glyoxal is 1:(0.6-0.8).

[0011] Furthermore, in step S4, the mass ratio of reactant A to reactant B is (2-3.7):1.

[0012] Furthermore, in step S4, the amount of toughening agent used is 0.8-1% of the total weight of reactants A and B; the toughening agent is polyvinyl alcohol or polyethylene glycol.

[0013] Furthermore, the mass ratio of formaldehyde and glyoxal used in step S4 to that used in step S3 is (50-70):(20-30); the mass ratio of formaldehyde to glyoxal is 1:(0.6-0.8).

[0014] Further, in step S4, the product is distilled under reduced pressure until the viscosity is 200-700 mPa·s.

[0015] The beneficial effects of this invention are: 1. In this invention, lignin is modified at room temperature and under normal pressure, which has low process requirements and helps to expand production; sodium hydroxide and urea aqueous solution can degrade lignin, reduce the molecular weight of lignin, increase the reactive sites, enhance the reactivity of modified lignin, and facilitate subsequent steps.

[0016] 2. In this invention, modified lignin is used to replace part of the expensive and toxic phenol in the reaction, and the substitution rate of modified lignin reaches more than 50%; non-toxic glyoxal is used to replace part of the formaldehyde in the reaction, reducing the amount of formaldehyde used. The free phenol content in the prepared phenolic resin is <1%, and the free formaldehyde content is <0.3%. Detailed Implementation

[0017] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0018] Example 1 S1. Lignin modification: Dissolve 50g of alkali lignin in 60g of 8% sodium hydroxide solution, add 7g of urea, stir and react for 36h. After the reaction is complete, adjust the pH of the reaction solution to neutral using 10% hydrochloric acid solution, separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin. S2. Add 60g of modified lignin, 30g of phenol and 60g of pure water to reactor 1, heat to 65℃ and stir for 1h to obtain reactant A; S3. Add 25g phenol, 8g pure water and 1g sodium hydroxide to reactor 2, heat to 70℃, add 15g formaldehyde and 10g glyoxal mixture dropwise, and continue stirring the reaction for 1.5h after the addition is complete to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, and add 2g of toughening agent polyethylene glycol. After stirring for 1 hour, adjust the temperature of reactor 2 to 90℃, and continue to add 35g of formaldehyde and 25g of glyoxal mixture. Stir for 1.5 hours, cool to room temperature, and distill the product under reduced pressure until the viscosity of the product is 500mPa·s to prepare environmentally friendly phenolic resin.

[0019] Example 2 S1. Lignin modification: Dissolve 50g of alkali lignin in 60g of 8% sodium hydroxide solution, add 7g of urea, stir and react for 36h. After the reaction is complete, adjust the pH of the reaction solution to neutral using 10% hydrochloric acid solution, separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin. S2. Add 70g of modified lignin, 30g of phenol and 60g of pure water to reactor 1, heat to 65℃ and stir for 1h to obtain reactant A; S3. Add 30g phenol, 8g pure water and 1g sodium hydroxide to reactor 2, heat to 70℃, add 17g formaldehyde and 13g glyoxal mixture dropwise, and continue stirring the reaction for 1.5h after the addition is complete to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, and add 2.2g of toughening agent polyethylene glycol. After stirring for 1 hour, adjust the temperature of reactor 2 to 90℃, and continue to add 40g of formaldehyde and 30g of glyoxal mixture. Stir for 1.5 hours, cool to room temperature, and distill the product under reduced pressure until the viscosity of the product is 500mPa·s to prepare environmentally friendly phenolic resin.

[0020] Comparative Example 1 115g of phenol, 60g of pure water and 1g of sodium hydroxide were added to a reactor and heated to 90°C. 85g of formaldehyde was added dropwise. After the addition was complete, the mixture was stirred and reacted for 1.5h. The mixture was then cooled to room temperature, and the product was distilled under reduced pressure until the viscosity of the product was 500mPa·s, thus obtaining phenolic resin.

[0021] Comparative Example 2 S1. Add 60g of alkali lignin, 30g of phenol and 60g of pure water to reactor 1, heat to 65℃ and stir for 1h to obtain reactant A; S2. Add 25g phenol, 8g pure water and 1g sodium hydroxide to reactor 2, heat to 70℃, add 15g formaldehyde and 10g glyoxal mixture dropwise, and continue stirring the reaction for 1.5h after the addition is complete to obtain reactant B; S3. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, and add 2g of toughening agent polyethylene glycol. After stirring for 1 hour, adjust the temperature of reactor 2 to 90℃, and continue to add 35g of formaldehyde and 25g of glyoxal mixture. Stir for 1.5 hours, cool to room temperature, and distill the product under reduced pressure until the viscosity of the product is 500mPa·s to prepare phenolic resin.

[0022] Comparative Example 3 S1. Lignin modification: Dissolve 50g of alkali lignin in 60g of 8% sodium hydroxide solution, control the reaction temperature at 120℃, stir the reaction for 2h, after the reaction is completed, use 10% hydrochloric acid solution to adjust the pH of the reaction solution to neutral, separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin; S2. Add 60g of modified lignin, 30g of phenol and 60g of pure water to reactor 1, heat to 65℃ and stir for 1h to obtain reactant A; S3. Add 25g phenol, 8g pure water and 1g sodium hydroxide to reactor 2, heat to 70℃, add 15g formaldehyde and 10g glyoxal mixture dropwise, and continue stirring the reaction for 1.5h after the addition is complete to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, and add 2g of toughening agent polyethylene glycol. After stirring for 1 hour, adjust the temperature of reactor 2 to 90℃, and continue to add 35g of formaldehyde and 25g of glyoxal mixture. Stir for 1.5 hours, cool to room temperature, and distill the product under reduced pressure until the viscosity of the product is 500mPa·s to prepare phenolic resin.

[0023] Comparative Example 4 S1. Lignin modification: Dissolve 50g of alkali lignin in 60g of 8% sodium hydroxide solution, add 7g of urea, stir and react for 36h. After the reaction is complete, adjust the pH of the reaction solution to neutral using 10% hydrochloric acid solution, separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin. S2. Add 90g of modified lignin, 30g of phenol and 60g of pure water to reactor 1, heat to 65℃ and stir for 1h to obtain reactant A; S3. Add 30g phenol, 8g pure water and 1g sodium hydroxide to reactor 2, heat to 70℃, add 17g formaldehyde and 13g glyoxal mixture dropwise, and continue stirring the reaction for 1.5h after the addition is complete to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, and add 2.2g of toughening agent polyethylene glycol. After stirring for 1 hour, adjust the temperature of reactor 2 to 90℃, and continue to add a mixture of 45g formaldehyde and 35g glyoxal. Stir for 1.5 hours, cool to room temperature, and distill the product under reduced pressure until the viscosity of the product is 500mPa·s to prepare phenolic resin.

[0024] Comparative Example 5 S1. Lignin modification: Dissolve 50g of alkali lignin in 60g of 8% sodium hydroxide solution, add 7g of urea, stir and react for 36h. After the reaction is complete, adjust the pH of the reaction solution to neutral using 10% hydrochloric acid solution, separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin. S2. Add 60g of modified lignin, 30g of phenol and 60g of pure water to reactor 1, heat to 65℃ and stir for 1h to obtain reactant A; S3. Add 25g phenol, 8g pure water and 1g sodium hydroxide to reactor 2, heat to 70℃, add 15g formaldehyde and 10g glyoxal mixture dropwise, and continue stirring the reaction for 1.5h after the addition is complete to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, stir and react for 1 hour, adjust the temperature of reactor 2 to 90°C, continue to add 35g of formaldehyde and 25g of glyoxal mixture, stir and react for 1.5 hours, cool to room temperature, and distill the product under reduced pressure until the viscosity of the product is 500 mPa·s to prepare phenolic resin.

[0025] Comparative Example 6 S1. Lignin modification: Dissolve 50g of alkali lignin in 60g of 8% sodium hydroxide solution, add 7g of urea, stir and react for 36h. After the reaction is complete, adjust the pH of the reaction solution to neutral using 10% hydrochloric acid solution, separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin. S2. Add 60g of modified lignin, 30g of phenol and 60g of pure water to reactor 1, heat to 65℃ and stir for 1h to obtain reactant A; S3. Add 25g phenol, 8g pure water and 1g sodium hydroxide to reactor 2, heat to 70℃, add 25g formaldehyde dropwise, and continue stirring the reaction for 1.5h after the addition is complete to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, and add 2g of toughening agent polyethylene glycol. After stirring for 1 hour, adjust the temperature of reactor 2 to 90℃, continue to add 60g of formaldehyde, stir for 1.5 hours, cool to room temperature, and distill the product under reduced pressure until the viscosity of the product is 500mPa·s to prepare phenolic resin.

[0026] Comparative Example 7 S1. Lignin modification: Dissolve 50g of alkali lignin in 60g of 8% sodium hydroxide solution, add 7g of urea, stir and react for 36h. After the reaction is complete, adjust the pH of the reaction solution to neutral using 10% hydrochloric acid solution, separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin. S2. Add 60g of modified lignin, 30g of phenol and 60g of pure water to reactor 1, heat to 65℃ and stir for 1h to obtain reactant A; S3. Add 25g phenol, 8g pure water and 1g sodium hydroxide to reactor 2, heat to 70℃, add 10g formaldehyde and 15g glyoxal mixture dropwise, and continue stirring the reaction for 1.5h after the addition is complete to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, and add 2g of toughening agent polyethylene glycol. After stirring for 1 hour, adjust the temperature of reactor 2 to 90℃, and continue to add a mixture of 25g formaldehyde and 35g glyoxal. Stir for 1.5 hours, cool to room temperature, and distill the product under reduced pressure until the viscosity of the product is 500mPa·s to prepare phenolic resin.

[0027] Test case The free phenol and free formaldehyde contents of the phenolic resins prepared in Examples 1-2 and Comparative Examples 1-7 were tested, and the testing of free phenol and free formaldehyde contents was carried out in accordance with GB / T 14732-2017. The prepared phenolic resins were applied to plywood, and their bonding strength was determined according to the relevant methods in GB / T 17657-2013.

[0028] Table 1 Example 1 52 41 0.68 0.15 1.95 Example 2 54 43 0.52 0.11 1.87 Comparative Example 1 - - 5.71 2.57 1.21 Comparative Example 2 52 (Lignin unmodified) 41 1.84 0.49 1.40 Comparative Example 3 52 (Modified without urea) 41 1.49 0.27 1.59 Comparative Example 4 60 44 0.88 0.23 1.61 Comparative Example 5 52 41 0.57 0.18 1.47 Comparative Example 6 52 - 0.64 0.86 1.52 Comparative Example 7 52 59 0.47 0.19 1.48 As shown in Table 1, the phenolic resins prepared in Examples 1 and 2 using modified lignin and glyoxal instead of phenol and formaldehyde exhibit good bonding strength, with free phenol content <1% and free formaldehyde content <0.3%. In Comparative Example 1, the phenolic resin prepared using phenol and formaldehyde showed a significant decrease in bonding strength, indicating excessively high levels of free phenol and formaldehyde, which could have environmental impacts. In Comparative Example 2, where lignin was not modified, the levels of free phenol and formaldehyde in the phenolic resin were significantly increased, and the bonding strength decreased. This indicates that the modified lignin in this invention has enhanced activity, helping to reduce free formaldehyde and improve bonding strength. In Comparative Example 3, where sodium hydroxide was used to modify lignin, the bonding strength of the phenolic resin prepared from lignin without urea modification was significantly reduced, and the levels of free phenol and formaldehyde were also higher than in Example 1. In Comparative Example 4, the content of modified lignin was increased, and a decreasing trend was observed in the bonding strength of the phenolic resin. The content of modified lignin should be reasonably controlled during the preparation process. In Comparative Example 5, no toughening agent was added, and the bonding strength of the phenolic resin decreased. In Comparative Example 6, glyoxal was not used to replace formaldehyde, and a significant increase in formaldehyde content was observed, leading to a decrease in bonding strength. The results from Comparative Examples 1 and 6 show that the modified lignin in this invention can reduce both the free phenol and free formaldehyde content of the phenolic resin. In Comparative Example 7, the content of glyoxal was increased, and a decrease in the bonding strength of the phenolic resin was observed, indicating that an appropriate amount of glyoxal can improve the bonding strength of the phenolic resin.

[0029] The beneficial effects of the above invention are as follows: In this invention, the mixing and dissolution of modified lignin and phenol in step S2 is detected by a mixing degree detection system, the mixing uniformity index W is calculated by a calculation module and compared with a threshold T, and the control module adjusts the working status of the mixing system based on the final analysis results of the calculation module, thereby realizing automated control of stirring. This avoids insufficient dissolution of modified lignin and phenol due to excessively short stirring time, and also avoids waste of resources due to excessively long stirring time.

[0030] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A production process for environmentally friendly phenolic resin, characterized in that, Includes the following steps: S1. Lignin modification: Dissolve lignin in sodium hydroxide solution, add urea, stir to react, and after the reaction is complete, use hydrochloric acid solution to adjust the pH of the reaction solution to neutral. Separate the precipitated solid precipitate from the solution, wash the precipitate with distilled water until neutral and dry it to obtain modified lignin. S2. Add modified lignin, phenol and pure water to reactor 1, heat to 65-75℃ and stir for 1-2 hours to obtain reactant A; wherein the mass ratio of modified lignin, phenol and pure water is (50-70):(25-35):(50-60); S3. Add phenol, pure water and sodium hydroxide to reactor 2, heat to 65-80℃, add a mixture of formaldehyde and glyoxal dropwise, the mass ratio of formaldehyde to glyoxal is 1:(0.6-0.8), after the addition is complete, continue stirring the reaction for 1-1.5h to obtain reactant B; S4. Maintain the temperature in reactor 2, add reactant A dropwise to reactant B, and add a toughening agent, which is polyvinyl alcohol or polyethylene glycol. After stirring and reacting for 1-1.5 hours, adjust the temperature of reactor 2 to 90-100℃, and continue to add a mixture of formaldehyde and glyoxal, with a mass ratio of formaldehyde to glyoxal of 1:(0.6-0.8). Stir and react for 1-1.5 hours, cool to room temperature, and distill the product under reduced pressure to prepare environmentally friendly phenolic resin.

2. The production process of the environmentally friendly phenolic resin according to claim 1, characterized in that, The lignin in step S1 is alkali lignin.

3. The production process of the environmentally friendly phenolic resin according to claim 1, characterized in that, In step S1, the concentration of sodium hydroxide solution is 8-10%, and the mass ratio of lignin, sodium hydroxide solution and urea is (30-40):(50-60):(6-8).

4. The production process of the environmentally friendly phenolic resin according to claim 1, characterized in that, In step S3, the mass ratio of phenol, pure water and sodium hydroxide is (20-30):(5-10):(0.8-1).

5. The production process of the environmentally friendly phenolic resin according to claim 1, characterized in that, The mass ratio of the amount of formaldehyde and glyoxal mixture used in step S3 to the amount of phenol used in step S3 is (20-30):(20-30).

6. The production process of the environmentally friendly phenolic resin according to claim 1, characterized in that, In step S4, the mass ratio of reactant A to reactant B is (2-3.7):

1.

7. The production process of the environmentally friendly phenolic resin according to claim 1, characterized in that, In step S4, the amount of toughening agent used is 0.8-1% of the total weight of reactants A and B.

8. The production process of the environmentally friendly phenolic resin according to claim 1, characterized in that, The mass ratio of formaldehyde and glyoxal used in step S4 to that used in step S3 is (50-70):(20-30).

9. The production process of the environmentally friendly phenolic resin according to claim 1, characterized in that, Step S4: Distill under reduced pressure until the viscosity of the product is 200-700 mPa·s.