Method for producing micron-scale and nano-scale lignin in pulping process

Abstract

The invention discloses a production method for producing micron-scale and nano-scale lignin in a pulping process, and relates to the technical field of pulping and papermaking. The method comprises the following steps: preparing dilute black liquor, mixing and stirring the dilute black liquor pump and plant sheets, pumping the dilute black liquor into a container C through a filter screen, simultaneously adding a high-boiling-point strong-polarity organic solvent into the container C to reduce the viscosity of the dilute black liquor, standing the dilute black liquor in the container C until the temperature is within the boiling point of the dilute black liquor, and separating out lignin particles. Pumping pure water of which the mass is 4-10 times that of the plant sheets into a pressure container B, heating to 80-98 DEG C, pumping liquid into a container D through a filter screen, adding magnesium chloride or zinc chloride into the container D, adding sodium sulfate, standing and cooling to room temperature, and separating out lignin particles; the particle size of precipitated lignin particles can be controlled, the method is very suitable for industrial production, the composite lignin particles can be further obtained, and the application effect is improved.

Description

Technical Field

[0001] The present invention discloses a production method for producing lignin at the micron and nanoscale during the pulping process, which relates to the technical field of pulp and paper making. Background Art

[0002] During the kraft or soda pulping process of paper pulp, the washing liquid for washing the cooked pulp is black and is called black liquor. The extraction of lignin from black liquor has been industrialized. The basic method is to add sulfuric acid to the alkaline black liquor to cause the lignin to flocculate and precipitate. After filtration, washing, and pressure filtration, de-alkalized industrial lignin is obtained.

[0003] When using lignin in polymer materials, it is required to have hot melt type, solubility, or nanoscale size, and for the direct utilization methods that are not melted or dissolved, the size requirements of lignin particles are more important. For example, as a filler for conventional plastics, its size requirement is below 50 μm. Another example is as an anti-aging agent for rubber, and its size requirement is below 20 nm. Currently, micro-nano lignin is usually prepared based on the anti-solvent method of adding acid precipitation and changing the polarity of the solution. However, in the existing methods, more solvents are added during the preparation process, and additional steps for removing solvents are required. Moreover, the existing methods cannot control the size of lignin particles according to requirements, nor can they further generate composite nanoparticles to improve the application effect of lignin particles. Summary of the Invention

[0004] In view of the problems of the prior art, the present invention provides a production method for producing lignin at the micron and nanoscale during the pulping process. The specific solution proposed by the present invention is as follows:

[0005] The present invention provides a production method for producing lignin at the micron and nanoscale during the pulping process, including:

[0006] Step 1: Under the high-temperature condition range of 120 - 170 °C, pump the black liquor in the paper pulp making process into pressure vessel A, and pump pure water at the same temperature into pressure vessel A to make the solid content concentration of the black liquor within the range of 5 - 12%, obtaining dilute black liquor.

[0007] Step 2: Pump the dilute black liquor into pressure vessel B, where there are plant flakes that have undergone vacuum degassing treatment. The weight of the plant flakes is 40% - 70% of the weight of the dilute black liquor, and the pH of the dilute black liquor is reduced to 8.9 - 11.4.

[0008] Step 3: Stir the plant flakes and dilute black liquor for a period of time, and then pump the dilute black liquor into container C through a filter. At the same time, add a high-boiling-point strongly polar organic solvent to container C, including propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide or ethylene glycol, in an amount of 1-4% of the volume of the dilute black liquor, to reduce the viscosity of the dilute black liquor. Let the dilute black liquor stand in container C until the temperature reaches within the boiling point of the dilute black liquor, and lignin particles will precipitate.

[0009] Step 4: Pump pure water into pressure vessel B in an amount 4-10 times the mass of the remaining plant flakes, heat it to 80-98 °C, and then pump the liquid into container D through a filter. At the same time, add magnesium chloride or zinc chloride to container D, with a concentration of 0.5-5 g / L, and add sodium sulfate at the same time, with a salt concentration of 5-50 g / L. Let the liquid stand and cool to room temperature in container D, and lignin particles will precipitate. The size of the lignin particles is 100-3000 nm. Adding a high-boiling-point strongly polar organic solvent reduces the viscosity of the dilute black liquor, facilitating the precipitation of the precipitated lignin particles. Adding sodium sulfate has a salting-out effect, promoting the precipitation of lignin. In addition, zinc chloride and magnesium chloride have the effects of assisting in dissolving and reducing the viscosity of polar polymers, making the formed lignin particles smaller.

[0010] Preferably, in step 2 of the method for producing lignin at the micro- and nano-scale during the pulping process, plant raw materials are selected from wood, straw, bamboo, wheat straw, and bagasse, and the plant raw materials are processed into plant flakes with a length and thickness not exceeding 0.2-0.5 mm.

[0011] Preferably, in step 3 of the method for producing lignin at the micro- and nano-scale during the pulping process, add nanoparticles of other materials to container C, so that the precipitated lignin particles are adsorbed on the surface of the nanoparticles of other materials, forming core-shell structured nano-lignin.

[0012] Preferably, the nanoparticles added in step 3 of the method for producing lignin at the micro- and nano-scale during the pulping process are silica particles, and the specific steps include:

[0013] Step 31: Stir the dilute black liquor in container C, control the temperature at 130 °C - 150 °C, and pump in silica sol under high pressure. The particle size of silica in the silica sol is 10 nm - 15 nm.

[0014] Step 32: Continuously stir and cool down in a gradient manner until the temperature drops to 60 °C, stop stirring, and let the dilute black liquor stand.

[0015] Step 33: Extract the sediment suspension at the bottom of container C and centrifuge to obtain the sediment.

[0016] Step 34: Add pure water to the sediment under an environment below 60 °C, stir, centrifuge, and remove the supernatant.

[0017] Step 35: Repeat step 34 2-4 times to obtain nano-lignin with a core-shell structure, wherein the core is silicon dioxide and the outer layer is nano-lignin particles.

[0018] Preferably, the nanoparticles added in step 3 of the method for producing micron- and nanometer-sized lignin during pulping are ground calcium carbonate particles, and the specific steps include:

[0019] Step 31: Stir the dilute black liquor in container C, control the temperature at 130-150°C, and pump in heavy calcium carbonate particles at high pressure. The particle size of heavy calcium carbonate is 400nm-500nm.

[0020] Step 32: Continue stirring and gradually cool down the temperature until the temperature drops to 60°C, stop stirring, and let the dilute black liquor stand.

[0021] Step 33: Extract the sediment suspension at the bottom of container C and centrifuge to obtain the sediment.

[0022] Step 34: Add pure water to the precipitate at a temperature below 60°C, stir, centrifuge, and remove the supernatant.

[0023] Step 35: Repeat step 34 2-4 times to obtain nano-lignin with a core-shell structure, wherein the inner core is calcium carbonate and the outer layer is nano-lignin particles.

[0024] Preferably, the nanoparticles added in step 3 of the method for producing micron- and nano-sized lignin during pulping are carbon black particles, and the specific steps include:

[0025] Step 31: Stir the dilute black liquid in container C, control the temperature at 130℃-150℃, and pump in the nano carbon black solution at high pressure. The carbon black particle size is 20nm-25nm.

[0026] Step 32: Continue stirring and gradually cool down the temperature until the temperature drops to 60°C, stop stirring, and let the dilute black liquor stand.

[0027] Step 33: Extract the sediment suspension at the bottom of container C and centrifuge to obtain the sediment.

[0028] Step 34: Add pure water to the precipitate at a temperature below 60°C, stir, centrifuge, and remove the supernatant.

[0029] Step 35: Repeat step 34 2-4 times to obtain nano-lignin with a core-shell structure, wherein the core is carbon black particles and the outer layer is nano-lignin particles.

[0030] The present invention also provides a nano-lignin with a core-shell structure, which is prepared by using the production method for producing lignin at the micro and nano scales during the pulping process, wherein the inner core is silica and the outer layer is nano-lignin particles.

[0031] The present invention also provides a nano-lignin with a core-shell structure, which is prepared by using the production method for producing lignin at the micro and nano scales during the pulping process, wherein the inner core is calcium carbonate and the outer layer is nano-lignin particles.

[0032] The present invention also provides a nano-lignin with a core-shell structure, which is prepared by using the production method for producing lignin at the micro and nano scales during the pulping process, wherein the inner core is carbon black particles and the outer layer is nano-lignin particles.

[0033] The present invention also provides an application of the nano-lignin with a core-shell structure. The nano-lignin composite with silica as the inner core and nano-lignin particles as the outer layer can be applied to the silicon-carbon industry, mainly used as the negative electrode material of new energy batteries. The nano-lignin composite with calcium carbonate as the inner core and nano-lignin particles as the outer layer can be applied in the coating field, such as in rubber coatings. The composite with carbon black as the inner core and nano-lignin as the outer shell can be applied in the tire and rubber industries, which can improve the tire life.

[0034] The beneficial effects of the present invention are as follows:

[0035] In the present invention, by adding plant flakes to the black liquor, the caustic soda in the black liquor is consumed and the temperature is gradually decreased, so as to control the precipitation of lignin. According to the addition amount of the plant raw material and the system temperature, the purpose of adjusting the lignin particle size is achieved, and lignin with a size ranging from nano to micro can be precipitated as required. Further, by adding nano-particles of other materials to the dilute black liquor in a high-temperature state, the precipitation of lignin is induced. During the precipitation process of lignin, it adsorbs and deposits on the nano-particles, and nano-micro sized lignin with a core-shell structure can be obtained easily embedded in the conventional pulping process, which is very suitable for industrial production. At the same time, composite lignin particles are obtained, improving the application effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, some simple drawings will be made for the sample data characterization in the implementation process of the present invention.

[0037] Figure 1 It is a dot chart of the solubility of lignin in sodium hydroxide solution (1 mol / L) versus temperature.

[0038] Figure 2Dot chart of the solubility of lignin in an environment with a temperature of 30°C and different pH values. The process of decreasing pH from high to low is the process of adding sulfuric acid to 1.0 mol / L sodium hydroxide solution.

[0039] Figure 3 SEM images of the wood chip surface and the adsorbed lignin. In the upper row of the figure, a, b, and c are the clean wood chip surfaces, and in the lower row, d, e, and f are the wood chip surfaces adsorbed with lignin.

[0040] Figure 4 Schematic diagram of the process of the present invention. Detailed implementation manners

[0041] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the cited embodiments do not limit the present invention.

[0042] Example 1

[0043] Separate lignin particles from pulping black liquor by using the method of the present invention. The specific process can be referred to as follows:

[0044] Step 1: Preparation of dilute black liquor: After the wood chips are cooked by the soda process, at the highest temperature condition of the cooking reaction, the pulp and black liquor are separated by filtration method, and the black liquor is pumped to pressure vessel A, and the high temperature condition range is 120 - 170°C. Pure water at the same temperature is pumped into pressure vessel A to make the solid content concentration of the black liquor within the range of 5 - 12%.

[0045] Step 2: Mix the fresh wood chips and the dilute black liquor: Use a high-pressure pump to pump the high-temperature dilute black liquor into pressure vessel B containing wood chips. Pressure vessel B and the wood chips are pre-vacuum degassed. The wood chips are sheet materials with a length and thickness not exceeding 0.2 - 0.5 mm, and the weight of the wood chips is 40% - 70% of the weight of the black liquor, and the wood chips are not cooked. The addition of the wood chips consumes the residual alkali in the dilute black liquor. After adding the wood chips, the pH of the dilute black liquor is reduced to 8.9 - 11.4.

[0046] Step 3: Precipitation of lignin micro-nanoparticles: Stir the wood chips and black liquor at a stirring speed of 100 - 300 rpm for 20 - 40 min. Stop stirring, pump the dilute black liquor into container C through a filter, and simultaneously add a high-boiling-point strong polar organic solvent to container C, including propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, or ethylene glycol, in an amount of 1 - 4% of the volume of the dilute black liquor to reduce the viscosity of the dilute black liquor. Let it stand in container C for 1 - 4 h. During this process, the temperature of the black liquor is reduced to within the boiling point of the black liquor, preferably 60 - 70 °C. The precipitated lignin particles gradually settle. The size of the lignin is 5 - 70 μm, belonging to micron lignin, and the yield can account for 40 - 70% of the total lignin in the black liquor. Micron lignin can be used as a filler in renewable plastics and biodegradable plastics, which can increase the bio-based content of the plastics.

[0047] Step 4: Pump pure water 4 - 10 times the mass of the plant flakes into pressure vessel B, heat it to 80 - 98 °C, and then pump the liquid into container D through a filter. At the same time, add magnesium chloride or zinc chloride to container D with a concentration of 0.5 - 5 g / L, and add sodium sulfate with a salt concentration of 5 - 50 g / L. Let the liquid stand in container D for 1 - 4 h and cool to room temperature of 15 - 30 °C. The precipitated lignin particles gradually settle. The size of the lignin is 100 - 3000 nm, and the yield can account for 20 - 50% of the total lignin in the black liquor. The end points of temperature increase and temperature decrease are the temperature difference. The relationship between the temperature difference and the yield of nano-lignin is shown in Table 2.

[0048] In this example, in step 1, the caustic soda in the black liquor reacts with the wood chips, and the pH value decreases, resulting in a decrease in the solubility of lignin. Table 1 lists the relationship between the addition amount of wood chips and the pH value of the black liquor. The dissolved lignin in the black liquor gradually precipitates due to the decrease in temperature and pH value. By controlling the ratio of wood chips to black liquor, the pH decrease value of the black liquor can be controlled within the alkaline range of 9 - 13, and nano-scale lignin can be obtained. If an excessive amount of wood chips is added, the pH will be lower, and the lignin size will become larger to the micron level, thereby regulating the precipitation particle size of lignin.

[0049] The plant flakes can also be selected from straw, bamboo, wheat straw, and bagasse. The preparation process is the same, and the effect can achieve the purpose of regulating the particle size of precipitated lignin.

[0050] Figure 3 Wood chips without adsorbed nano-lignin and wood chips with adsorbed nano-lignin are shown. By increasing the temperature, desorption occurs. The desorbed lignin is in the liquid and is nano-scale. Nano-scale lignin can be obtained through desorption. After desorption, the wood chips, because they have been treated with the alkaline substances in the black liquor, will reduce the amount of alkali used, shorten the pulping cooking time, and improve the fiber quality during the subsequent pulping process.

[0051] Example 2

[0052] In step 3 of Example 1, nanoparticles of other materials are added to container C, so that the precipitated lignin particles are adsorbed on the surface of the nanoparticles of other materials to form core-shell structured nano-lignin. The added nanoparticles can be nano-silica sol, nano-ground calcium carbonate particles, carbon black for nano-rubber, etc. The process can be referred to as follows:

[0053] Step 31: Stir the dilute black liquor in container C at a stirring speed of 600 rpm, control the temperature at 130°C - 150°C, and pump in 200 L of silica sol under high pressure. The particle size of silicon dioxide in the silica sol is 10 nm - 15 nm.

[0054] Step 32: Continuously stir for 20 min and cool down in a gradient manner until the temperature drops to 60°C, then stop stirring and let the dilute black liquor stand for 5 h.

[0055] Step 33: Extract the precipitate suspension at the bottom of container C and centrifuge it at a speed of 5000 rpm to obtain the precipitate. The centrifuged precipitate is the unpurified nano-lignin particles with a core of nano-silicon dioxide and an outer layer of lignin.

[0056] Step 34: Add pure water to the precipitate under an environment below 60°C, stir, centrifuge, and remove the supernatant.

[0057] Step 35: Repeat step 34 for 2 - 4 times to obtain the nano-lignin with a core-shell structure, with a core of silicon dioxide and an outer layer of nano-lignin particles, and the particle size is 30 - 45 nm. This silicon dioxide-lignin composite is mainly used in the silicon-carbon industry for the negative electrode materials of new energy batteries.

[0058] In the above process, if step 31 is changed to pump in ground calcium carbonate particles with a particle size of 500 nm, then in step 35, particles with a core of calcium carbonate and an outer layer of lignin are obtained, and the particle diameter is 1.0 - 1.2 μm. The lignin-calcium carbonate core-shell structured nanoparticles obtained by this method have utilization value in the coating field, and the lignin-carbon black core-shell structured nanoparticles have important value in the rubber field.

[0059] In the above process, if step 31 is changed to pump in a nano-carbon black solution with a carbon black particle size of 20 nm, then the core of the particles with a core-shell structure formed is carbon black and the shell is lignin particles, and the particle size is 35 - 50 nm. The carbon black-lignin composite is mainly used in the tire and rubber industries, and lignin has antioxidant properties, which can improve the tire life.

[0060] Table 1

[0061] Wood chip addition amount (%) 0 20 40 50 60 70 Black liquor pH 13.1 12.5 11.4 9.9 9.4 8.9

[0062] Table 2

[0063] Temperature difference °C 20 40 60 80 Lignin yield * 18.9 32.5 41.4 49.5

[0064] The above are the preferred embodiments of the present invention. Within the scope of the technical solution of the present invention, adjusting the types of reagents and the amounts of reagents used according to the actual situation can achieve the effects produced by the present invention.

[0065] The reagents involved in the method of the present invention are purchased or obtained as gifts through regular channels without special instructions.

[0066] The above-described embodiments are only preferred embodiments given to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are within the protection scope of the present invention. The protection scope of the present invention is subject to the claims.

Claims

1. A production method for producing lignin at the micron and nanometer scales during the pulping process, characterized by Comprising: Step 1: Under a high-temperature condition within the range of 120 - 170 °C, pump the black liquor in papermaking pulping into pressure vessel A, and pump pure water at the same temperature into pressure vessel A, finally making the solid content concentration of the black liquor within the range of 5 - 12%, to obtain dilute black liquor. Step 2: Pump the dilute black liquor into pressure vessel B. There are plant flakes with vacuum degassing treatment in pressure vessel B, and the weight of the plant flakes is 40% - 70% of the weight of the dilute black liquor, so that the pH of the dilute black liquor is reduced to 8.9 - 11.

4. Step 3: Stir the plant flakes and the dilute black liquor for a period of time, then pump the dilute black liquor into container C through a filter. At the same time, add a high-boiling-point strong polar organic solvent into container C, including propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide or ethylene glycol, adding 1 - 4% of the volume of the dilute black liquor, to reduce the viscosity of the dilute black liquor. Let the dilute black liquor stand in container C until the temperature reaches within the boiling point of the dilute black liquor, and lignin particles precipitate. Step 4: Pump pure water 4 - 10 times the mass of the plant flakes into pressure vessel B, heat it to 80 - 98 °C, then pump the liquid into container D through a filter. At the same time, add magnesium chloride or zinc chloride into container D, with a concentration of 0.5 - 5 g / L, and add sodium sulfate at the same time, with a salt concentration of 5 - 50 g / L. Let the liquid stand and cool to room temperature in container D, and lignin particles precipitate. The size of the lignin particles is 100 - 3000 nm.

2. A production method for producing lignin at the micron and nanoscale during the pulping process according to claim 1, characterized in that In step 2, select plant raw materials from wood, straw, bamboo, wheat straw, bagasse, and process the plant raw materials into plant flakes with a length and thickness not exceeding 0.2 - 0.5 mm.

3. A production method for producing lignin at the micron and nanometer scales during the pulping process according to claim 1, characterized in that in step 3, add nanoparticles of other materials into container C, so that the precipitated lignin particles are adsorbed on the surface of the nanoparticles of other materials, forming core-shell structured nano-lignin.

4. A production method for producing lignin at the micron and nanometer scales during the pulping process according to claim 3, characterized in that The nanoparticles added in step 3 are silicon dioxide particles, and the specific steps include: Step 31: Stir the dilute black liquor in container C, control the temperature at 130 °C - 150 °C, and pump in silica sol under high pressure. The particle size of silicon dioxide in the silica sol is 10 nm - 15 nm. Step 32: Continuously stir and cool down in a gradient manner until the temperature drops to 60 °C, stop stirring, and let the dilute black liquor stand. Step 33: Extract the sediment suspension at the bottom of container C and centrifuge to obtain the sediment. Step 34: Add pure water to the sediment under an environment below 60 °C, stir, centrifuge, and remove the supernatant. Step 35: Repeat step 34 for 2 - 4 times to obtain core-shell structured nano-lignin, with the core being silicon dioxide and the outer layer being nano-lignin particles.

5. A production method for producing lignin at the micron and nanometer scales during the pulping process according to claim 3, characterized in that The nanoparticles added in step 3 are heavy calcium carbonate particles, and the specific steps include: Step 31: Stir the dilute black liquor in container C, control the temperature at 130 °C - 150 °C, and pump in heavy calcium carbonate particles under high pressure. The particle size of the heavy calcium carbonate is 400 nm - 500 nm. Step 32: Continuously stir and cool down in a gradient manner until the temperature drops to 60 °C, stop stirring, and let the dilute black liquor stand. Step 33: Extract the sediment suspension at the bottom of container C and centrifuge to obtain the sediment. Step 34: Add pure water to the precipitate under an environment below 60°C, stir, centrifuge, and remove the supernatant. Step 35: Repeat Step 34 for 2 - 4 times to obtain nano-lignin with a core-shell structure, where the inner core is calcium carbonate and the outer layer is nano-lignin particles.

6. A production method for producing lignin at the micron and nanometer scales during the pulping process according to claim 3, characterized in that The nano-particles added in Step 3 are carbon black particles. The specific steps include: Step 31: Stir the dilute black liquor in Container C, control the temperature at 130°C - 150°C, and pump in the nano-carbon black solution under high pressure. The particle size of the carbon black is 20nm - 25nm. Step 32: Continuously stir and cool down in gradients until the temperature drops to 60°C, then stop stirring and let the dilute black liquor stand. Step 33: Extract the precipitate suspension at the bottom of Container C and centrifuge to obtain the precipitate. Step 34: Add pure water to the precipitate under an environment below 60°C, stir, centrifuge, and remove the supernatant. Step 35: Repeat Step 34 for 2 - 4 times to obtain nano-lignin with a core-shell structure, where the inner core is carbon black particles and the outer layer is nano-lignin particles.

7. A nano-lignin with a core-shell structure, characterized in that Obtained by using the production method of producing lignin at the microscale and nanoscale during the pulping process described in Claim 4.

8. A nano-lignin with a core-shell structure, characterized in that Obtained by using the production method of producing lignin at the microscale and nanoscale during the pulping process described in Claim 5.

9. A nano-lignin with a core-shell structure, characterized in that Obtained by using the production method of producing lignin at the microscale and nanoscale during the pulping process described in Claim 6.

10. Application using the nano-lignin with a core-shell structure according to any one of Claims 7 - 8.

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