Modified lignin as well as preparation method and application thereof

Abstract

The invention relates to modified lignin as well as a preparation method and application thereof, and belongs to the technical field of chemical materials as well as preparation and application thereof. The preparation method comprises the following steps: acidifying and washing papermaking black liquid to obtain acidified lignin; deionized water is added, and the PH is adjusted with alkali liquor; adding glycidyl ether and a cosolvent for reaction; adding a silane coupling agent for reaction, centrifuging and washing to be neutral; performing vacuum drying and crushing to obtain modified lignin; and crushing to a micron level through a jet mill. The modified lignin can replace carbon black to be used as a reinforcing agent of a rubber material, has the advantages of being good in reinforcing effect, low in production cost, safe, environmentally friendly and the like, can endow rubber products with good tensile property, wear resistance, oxidation resistance and aging resistance, and is particularly suitable for rubber products with medium strength requirements and cost-emphasized or environmental protection properties.

Description

Technical Field

[0001] This invention belongs to the field of chemical materials and their preparation and application technology, specifically relating to a modified lignin, its preparation method and application. Background Technology

[0002] Lignin, an abundant organic polymer found in nature, is widely present in plant cell walls. It possesses a complex three-dimensional structure and contains numerous active groups such as phenolic and alcoholic hydroxyl groups. Some paper mills simply discharge or incinerate lignin-containing black liquor, causing significant resource waste and environmental pollution.

[0003] Carbon black, as an important reinforcing agent in the rubber industry, can significantly improve the mechanical properties of rubber and is widely used in the production of rubber products such as tires and conveyor belts. In recent years, some studies have found that lignin can partially replace traditional carbon black in rubber products. However, current technologies for extracting lignin from papermaking black liquor and applying it to rubber still have many shortcomings, such as complex preparation processes, high costs, poor compatibility with rubber, and large-scale agglomeration in rubber products, leading to a serious decline in the mechanical properties of the materials, which limits its large-scale industrial application. Therefore, how to develop an efficient, low-cost lignin modification method that can improve compatibility is a core problem that urgently needs to be solved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for preparing lignin-based materials that offers good reinforcing effects, low production costs, and is safe and environmentally friendly. This method enables lignin-based materials to replace carbon black and impart excellent tensile, abrasion-resistant, antioxidant, and anti-aging properties to rubber. At the same time, it enables the efficient utilization of industrial waste and reduces environmental pollution.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing modified lignin, which includes the following steps:

[0007] Step 1) Filter the black liquor of papermaking to remove solid impurities, add acidic substances to adjust the pH to 2-4, centrifuge, wash the filter cake with water until neutral, and vacuum dry at 65°C to obtain acid-precipitated lignin.

[0008] Step 2) Take the acid-precipitated lignin and put it into the reaction vessel. Add deionized water, adjust the pH to 10-12 with alkaline solution, raise the temperature to 50-70℃, and keep it at that temperature for 1-2 hours.

[0009] Step 3) Add glycidyl ether and co-solvent to the reaction vessel, heat to 70-80℃, keep at this temperature for 4-8 hours, cool to room temperature, and adjust the pH to 5.5-6.5 with acetic acid;

[0010] Step 4) Add silane coupling agent to the reaction vessel, heat to 65-85℃, keep warm for 2-6 hours, centrifuge, wash with water until neutral, vacuum dry at 65℃, and pulverize to obtain the modified lignin.

[0011] Furthermore, by weight, the lignin content of the papermaking black liquor described in step 1) is 5%-20%.

[0012] Further, by weight, the amount of acid-precipitated lignin used in step 2) is 10-20 parts, and the amount of deionized water is 30-60 parts.

[0013] Furthermore, the acidic substance in step 1) is 50% dilute sulfuric acid;

[0014] And / or, the alkaline solution in step 2) is 10% sodium hydroxide.

[0015] Further, by weight, the amount of glycidyl ether used in step 3) is 1-5 parts, and the amount of the cosolvent is 1-10 parts.

[0016] Further, by weight, the amount of silane coupling agent used in step 4) is 0.1-3 parts, and the silane coupling agent is one or more of KH-151, Si-69, KH550, KH560, and HMOS.

[0017] Further, the glycidyl ether mentioned in step 3) is one or more of itaconic acid glycidyl ether, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and bisphenol A diglycidyl ether;

[0018] The co-solvent is one or more of 1,4-dioxane, methanol, ethanol, and acetonitrile.

[0019] Furthermore, the modified lignin described in step 4) can be pulverized to the micron level using an air jet mill.

[0020] The present invention also provides a modified lignin, which is prepared by the modified lignin preparation method described above.

[0021] The present invention also provides the application of the modified lignin as described above as a raw material in the preparation of rubber composite materials.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) This invention uses papermaking black liquor as raw material to realize the high-value utilization of industrial waste, effectively reduce the pollution of the environment caused by direct discharge of black liquor, and at the same time reduce the cost of lignin extraction, which meets the requirements of green circular economy and sustainable development.

[0024] (2) The lignin prepared in this invention, through glycidyl ether modification, introduces more polar groups (such as hydroxyl groups and ether bonds) and flexible segments into the lignin molecule. Utilizing the synergistic effect of epoxy-carboxyl groups, the compatibility between lignin and the rubber matrix is ​​significantly improved. Further reaction with a silane coupling agent allows the siloxane bonds to react with the hydroxyl groups on the lignin surface, while the organic groups at the other end physically entangle with the rubber molecular chains, forming a stable "modified lignin-silane-rubber" bridging structure, effectively improving the interfacial compatibility between the filler and the rubber.

[0025] (3) This invention, through the triple innovation of “waste utilization + molecular modification + refined process”, reduces production costs and solves the problem of papermaking wastewater reuse compared with the existing technology. At the same time, the modified lignin provided can replace carbon black as a reinforcing agent for rubber products, and can give rubber good tensile, wear resistance, oxidation resistance and aging resistance properties. It is especially suitable for rubber products with medium strength requirements and those that focus on cost or environmental protection attributes. Detailed Implementation

[0026] The present invention is further illustrated below by way of examples, but these examples do not limit the invention to the scope of the embodiments described. Experimental methods in the following examples, unless otherwise specified, are performed according to conventional methods and conditions, or as selected in the product instructions. Unless otherwise specified, all reagents and materials are commercially available.

[0027] Example 1

[0028] Step 1: Filter 200 parts by weight of papermaking black liquor with a lignin content of 5% through a 325-mesh sieve to remove solid impurities, add 50% dilute sulfuric acid to adjust the pH to 3.0, centrifuge, wash the filter cake with water until neutral, and vacuum dry at 65°C to obtain acid-precipitated lignin.

[0029] Step 2: Take 10 parts by weight of acid-precipitated lignin, add 30 parts by weight of deionized water, adjust the pH to 10.0 with 10% sodium hydroxide solution, heat to 60℃, and keep warm for 1 hour;

[0030] Step 3: Add 1 part by weight of itaconic acid glycidyl ether and 3 parts by weight of ethanol, heat to 70°C, keep warm for 5 hours, cool to room temperature, and adjust the pH to 5.5 with acetic acid;

[0031] Step 4: Add 0.15 parts by weight of silane coupling agent KH-151 and 0.05 parts by weight of HMOS, heat to 70°C, keep warm for 2 hours, centrifuge, wash with water until neutral, vacuum dry at 65°C, and pulverize to obtain modified lignin.

[0032] Step 5: The modified lignin is pulverized to the micron level using an air jet mill.

[0033] Example 2

[0034] Step 1: Filter 250 parts by weight of papermaking black liquor with a lignin content of 10% through a 325-mesh sieve to remove solid impurities, add 50% dilute sulfuric acid to adjust the pH to 3.0, centrifuge, wash the filter cake with water until neutral, and vacuum dry at 65°C to obtain acid-precipitated lignin.

[0035] Step 2: Take 15 parts by weight of acid-precipitated lignin, add 45 parts by weight of deionized water, adjust the pH to 11.0 with 10% sodium hydroxide solution, heat to 65℃, and keep warm for 1 hour;

[0036] Step 3: Add 1 part by weight of itaconic acid glycidyl ether, 0.5 parts by weight of ethylene glycol diglycidyl ether, and 4 parts by weight of methanol. Heat to 70°C, keep warm for 5 hours, cool to room temperature, and adjust the pH to 6.0 with acetic acid.

[0037] Step 4: Add 0.15 parts by weight of silane coupling agent Si-69 and 0.07 parts by weight of HMOS, heat to 70°C, keep warm for 3 hours, centrifuge, wash with water until neutral, vacuum dry at 65°C, and pulverize to obtain modified lignin.

[0038] Step 5: The modified lignin is pulverized to the micron level using an air jet mill.

[0039] Example 3

[0040] Step 1: Filter 250 parts by weight of papermaking black liquor with a lignin content of 10% through a 325-mesh sieve to remove solid impurities, add 50% dilute sulfuric acid to adjust the pH to 3.0, centrifuge, wash the filter cake with water until neutral, and vacuum dry at 65°C to obtain acid-precipitated lignin.

[0041] Step 2: Take 15 parts by weight of acid-precipitated lignin, add 45 parts by weight of deionized water, adjust the pH to 11.0 with 10% sodium hydroxide solution, heat to 70℃, and keep warm for 2 hours;

[0042] Step 3: Add 1 part by weight of bisphenol A diglycidyl ether, 1 part by weight of itaconic acid glycidyl ether, and 5 parts by weight of 1,4-dioxane. Heat to 80°C, keep warm for 6 hours, cool to room temperature, and adjust the pH to 6.5 with acetic acid.

[0043] Step 4: Add 0.2 parts by weight of silane coupling agent KH550 and 0.05 parts by weight of HMOS, heat to 85°C, keep warm for 4 hours, centrifuge, wash with water until neutral, vacuum dry at 65°C, and pulverize to obtain modified lignin.

[0044] Step 5: The modified lignin is pulverized to the micron level using an air jet mill.

[0045] Example 4

[0046] Step 1: Filter 300 parts by weight of papermaking black liquor with a lignin content of 20% through a 325-mesh sieve to remove solid impurities, add 50% dilute sulfuric acid to adjust the pH to 3.0, centrifuge, wash the filter cake with water until neutral, and vacuum dry at 65°C to obtain acid-precipitated lignin.

[0047] Step 2: Take 20 parts by weight of acid-precipitated lignin, add 60 parts by weight of deionized water, adjust the pH to 11.0 with 10% sodium hydroxide solution, heat to 70℃, and keep warm for 2 hours;

[0048] Step 3: Add 2 parts by weight of ethylene glycol diglycidyl ether, 0.8 parts by weight of itaconic acid glycidyl ether, and 6 parts by weight of ethanol. Heat to 80°C, keep warm for 7 hours, cool to room temperature, and adjust the pH to 6.5 with acetic acid.

[0049] Step 4: Add 0.25 parts by weight of silane coupling agent KH560 and 0.04 parts by weight of HMOS, heat to 85°C, keep warm for 6 hours, centrifuge, wash with water until neutral, vacuum dry at 65°C, and pulverize to obtain modified lignin.

[0050] Step 5: The modified lignin is pulverized to the micron level using an air jet mill.

[0051] Example 5

[0052] Step 1: Filter 300 parts by weight of papermaking black liquor with a lignin content of 20% through a 325-mesh sieve to remove solid impurities, add 50% dilute sulfuric acid to adjust the pH to 3.0, centrifuge, wash the filter cake with water until neutral, and vacuum dry at 65°C to obtain acid-precipitated lignin.

[0053] Step 2: Take 20 parts by weight of acid-precipitated lignin, add 60 parts by weight of deionized water, adjust the pH to 11.0 with 10% sodium hydroxide solution, heat to 70℃, and keep warm for 2 hours;

[0054] Step 3: Add 3.6 parts by weight of ethylene glycol diglycidyl ether, 1.4 parts by weight of itaconic acid glycidyl ether, 5 parts by weight of ethanol, and 5 parts by weight of 1,4-dioxane. Heat to 80°C and keep warm for 7 hours. Cool to room temperature and adjust the pH to 6.5 with acetic acid.

[0055] Step 4: Add 3 parts by weight of silane coupling agent KH560, heat to 85℃, keep warm for 6 hours, centrifuge, wash with water until neutral, vacuum dry at 65℃, and pulverize to obtain modified lignin.

[0056] Step 5: The modified lignin is pulverized to the micron level using an air jet mill.

[0057] Example 6

[0058] Step 1: 230 parts by weight of papermaking black liquor with a lignin content of 16% were filtered through a 325-mesh sieve to remove solid impurities. 50% dilute sulfuric acid was added to adjust the pH to 3.0. The filter cake was centrifuged multiple times and washed with water until neutral. It was then vacuum dried at 65°C to obtain acid-precipitated lignin.

[0059] Step 2: Take 17 parts by weight of acid-precipitated lignin, add 40 parts by weight of deionized water, adjust the pH to 11.0 with 10% sodium hydroxide solution, heat to 70℃, and keep warm for 2 hours;

[0060] Step 3: Add 1 part by weight of itaconic acid glycidyl ether and 1 part by weight of ethanol, heat to 80°C, keep warm for 7 hours, cool to room temperature, and adjust the pH to 6.5 with acetic acid;

[0061] Step 4: Add 0.1 parts by weight of silane coupling agent Si-69, heat to 85°C, keep warm for 6 hours, centrifuge, wash with water until neutral, vacuum dry at 65°C, and pulverize to obtain modified lignin;

[0062] Step 5: The modified lignin is pulverized to the micron level using an air jet mill.

[0063] Comparative Example 1

[0064] Comparative Example 1 is unmodified lignin.

[0065] Comparative Example 2

[0066] Comparative Example 2 is the epoxidized lignin prepared according to Example 1 in the specific implementation method of patent CN117534882A.

[0067] Comparative Example 3

[0068] The only difference from Example 4 is that in step 3, “2 parts by weight of ethylene glycol diglycidyl ether, 0.8 parts by weight of itaconic acid glycidyl ether, and 6 parts by weight of ethanol” are replaced with “2 parts by weight of zinc acrylate with a concentration of 2 g / mL, 2 parts by weight of tetramethylthiuram monosulfide, and 6 parts by weight of ethanol”.

[0069] Comparative Example 4

[0070] The only difference from Example 4 is that in step 3, “2 parts by weight of ethylene glycol diglycidyl ether, 0.8 parts by weight of itaconic acid glycidyl ether, and 6 parts by weight of ethanol” are replaced with “2 parts by weight of 6000 mesh calcined kaolin”.

[0071] Comparative Example 5

[0072] Step 1: Concentrate 300 parts by weight of papermaking black liquor with a lignin content of 12% to 40% of the original weight to obtain concentrated black liquor;

[0073] Step 2: Add 20 parts by weight of concentrated black liquor and 60 parts by weight of deionized water to the reactor, adjust the pH to 11.0 with 10% sodium hydroxide solution, raise the temperature to 70°C, and keep it at that temperature for 2 hours.

[0074] Step 3: Add 3 parts by weight of itaconic acid glycidyl ether and 0.28 parts by weight of silane coupling agent KH560, stir and keep warm for 6 hours;

[0075] Step 4: Cool to room temperature, add acetic acid to adjust pH=6, centrifuge, wash with water until neutral, vacuum dry at 65℃, and pulverize to obtain modified lignin;

[0076] Step 5: The modified lignin is pulverized to the micron level using an air jet mill.

[0077] Comparative Example 6

[0078] Step 1: Concentrate 300 parts by weight of papermaking black liquor with a lignin content of 12% to 40% of the original weight to obtain concentrated black liquor;

[0079] Step 2: Add 20 parts by weight of concentrated black liquor, 10 parts by weight of 6000 mesh calcined kaolin and 1 part by weight of silane coupling agent SI-69 to the reactor, stir and keep warm for 1 hour.

[0080] Step 3: Cool to room temperature, add sulfuric acid to adjust pH to 3, centrifuge to remove most of the water, and wash with water until neutral;

[0081] Step 4: Vacuum dry at 85℃ for 6 hours, then pulverize to obtain modified lignin.

[0082] Implementation effect

[0083] Rubber preparation raw material formula:

[0084] 100 parts natural rubber, 30 parts carbon black, 20 parts modified / unmodified lignin, 2 parts aromatic oil, 2 parts stearic acid, 3 parts zinc oxide, 1.5 parts sulfur, 0.1 parts anti-scorching agent, 0.5 parts anti-aging agent, and 1.4 parts accelerator.

[0085] Preparation method

[0086] Natural rubber was added to a mixing mill and plasticized at 40°C for 2 minutes. Then, carbon black, modified lignin, and aromatic oil were added, and the mixture was mixed at 100°C until constant weight was achieved. Stearic acid and zinc oxide were added and mixed for 15 minutes. The material was then passed through a two-roll mill and left to stand for 4 hours. The mixed rubber was then added to the mixing mill, and sulfur, scorch inhibitor, anti-aging agent, and accelerator were added at 80°C and mixed for 3 minutes. The two-roll mill temperature was then set at 60°C, and the mixed rubber compound was passed through a two-roll mill for shaping. The mixed rubber was then vulcanized using a 2mm thick mold at 155°C for 30 minutes to obtain the modified lignin-natural rubber composite material.

[0087] Performance test results

[0088] The tensile strength and elongation at break of the samples were tested according to GB / T528-2009.

[0089] The tear strength of the samples was tested according to GB / T529-2008;

[0090] The abrasion resistance of the samples was determined according to GB / T1689-2014;

[0091] The antioxidant properties of the samples were determined according to GB / T3512-2014;

[0092] The anti-aging properties of the samples were determined according to GB / T3512-2014.

[0093] The following are the rubber performance data for the examples and comparative samples.

[0094]

[0095] As can be seen from the table, compared with the unmodified lignin of Comparative Example 1 and the lignin prepared by Comparative Example 2 (epoxidation modification), Comparative Example 3 (calcined kaolin modification), and Comparative Example 4 (zinc acrylate and tetramethylthiuramite monosulfide modification), the rubbers obtained by adding the modified lignin prepared in Examples 1-6 of this application have better tensile strength, elongation at break, tear strength, abrasion resistance, oxidation resistance, and aging resistance than Comparative Examples 1-4. This indicates that the modified lignin of this application forms a cross-linked network with the rubber, significantly improving compatibility and providing better reinforcing effect. Furthermore, Comparative Examples 5 and 6 used different preparation processes than those of this application to modify lignin, and the rubbers prepared from the modified lignin obtained from these examples also had inferior tensile strength, elongation at break, tear strength, abrasion resistance, oxidation resistance, and aging resistance compared to Examples 1-6.

[0096] The results show that, compared with existing products, the modified lignin prepared in Example 5 has a more ideal rubber reinforcing effect, and the rubber products prepared with it have better tensile, wear resistance, oxidation resistance and aging resistance.

[0097] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing modified lignin, characterized in that, It includes the following steps: Step 1) Filter the black liquor of papermaking to remove solid impurities, add acidic substances to adjust the pH to 2-4, centrifuge, wash the filter cake with water until neutral, and vacuum dry at 65°C to obtain acid-precipitated lignin. Step 2) Take the acid-precipitated lignin and put it into the reaction vessel. Add deionized water, adjust the pH to 10-12 with alkaline solution, raise the temperature to 50-70℃, and keep it at that temperature for 1-2 hours. Step 3) Add glycidyl ether and co-solvent to the reaction vessel, heat to 70-80℃, keep at this temperature for 4-8 hours, cool to room temperature, and adjust the pH to 5.5-6.5 with acetic acid; Step 4) Add silane coupling agent to the reaction vessel, heat to 65-85℃, keep warm for 2-6 hours, centrifuge, wash with water until neutral, vacuum dry at 65℃, and pulverize to obtain the modified lignin.

2. The method for preparing modified lignin according to claim 1, characterized in that, The lignin content of the black liquor used in step 1) is 5%-20%.

3. The method for preparing modified lignin according to claim 1, characterized in that, By weight, the amount of acid-precipitated lignin used in step 2) is 10-20 parts, and the amount of deionized water is 30-60 parts.

4. The method for preparing modified lignin according to claim 1, characterized in that, The acidic substance in step 1) is 50% dilute sulfuric acid; And / or, the alkaline solution in step 2) is 10% sodium hydroxide.

5. The method for preparing modified lignin according to claim 1, characterized in that, The amount of glycidyl ether used in step 3) is 1-5 parts by weight, and the amount of cosolvent used is 1-10 parts.

6. The method for preparing modified lignin according to claim 1, characterized in that, The amount of silane coupling agent used in step 4) is 0.1-3 parts by weight, and the silane coupling agent is one or more of KH-151, Si-69, KH550, KH560, and HMOS.

7. The method for preparing modified lignin according to claim 1, characterized in that, The glycidyl ether mentioned in step 3) is one or more of itaconic acid glycidyl ether, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and bisphenol A diglycidyl ether; The co-solvent is one or more of 1,4-dioxane, methanol, ethanol, and acetonitrile.

8. The method for preparing modified lignin according to claim 1, characterized in that, The modified lignin described in step 4) can be pulverized to the micron level using an air jet mill.

9. A modified lignin, characterized in that, It is prepared by the method of preparing modified lignin according to any one of claims 1 to 8.

10. The application of the modified lignin as described in claim 9 in the preparation of rubber composite materials.

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