Modified lignin as well as preparation method and application thereof

Abstract

The invention discloses modified lignin as well as a preparation method and application thereof, and belongs to the technical field of modified lignin preparation. The preparation method comprises dry modification and organic solvent modification. The dry modification comprises the following steps: adding an alkaline agent into lignin, uniformly mixing, adding a modifier, mixing, and heating for reaction to obtain modified lignin; the organic solvent modification comprises the following steps: dispersing lignin in an organic solvent, adding a modifier for reaction, and distilling out the organic solvent under negative pressure to obtain modified lignin; the modifier is alkenyl succinic anhydride or alkyl ketene dimer. According to the invention, alkenyl succinic anhydride and alkyl ketene dimer are adopted as modifiers to chemically modify lignin, so that the reaction activity of lignin can be remarkably improved, the lignin can form chemical bonding with a rubber matrix, the dispersity and compatibility of lignin in the rubber matrix are effectively improved, and the reinforcing effect of lignin on rubber is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of modified lignin preparation, and particularly relates to a modified lignin, a preparation method thereof and an application thereof. Background Art

[0002] Lignin is the second most abundant renewable polymer in nature, widely existing in plant cell walls, with an annual output of about 1.65 million tons. However, currently 95% of lignin is directly burned, and only less than 5% is used for value-added utilization. Lignin, as a green and renewable resource, has many advantages such as wide sources, light weight, and broad ecological adaptability. Industrial lignin mainly comes from the black liquor of the paper industry and the residues of the biorefinery industry. If not fully utilized, it will become waste and cause environmental pollution.

[0003] As a natural polymer, lignin has a complex molecular structure, containing active groups such as aromatic groups, phenolic hydroxyl groups, alcoholic hydroxyl groups, carboxyl groups, methoxy groups, conjugated double bonds, etc., having certain chemical activity, and a relatively large specific surface area. In theory, it can be used as a rubber reinforcing agent to replace carbon black. However, due to the easy formation of hydrogen bond aggregation of its surface polar groups and poor compatibility with non-polar rubber, it is difficult to be uniformly dispersed, which limits its application in the rubber field.

[0004] In order to solve the above problems, it is necessary to chemically modify lignin to improve its compatibility with non-polar rubber and at the same time improve the dispersibility of lignin in the rubber matrix. Summary of the Invention

[0005] In order to overcome the above technical problems existing in the prior art, the present invention provides a modified lignin, a preparation method thereof and an application thereof.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a preparation method of a modified lignin. The preparation method is dry modification, including: adding an alkaline agent to lignin, mixing evenly and then adding a modifier and mixing, heating and reacting to obtain the modified lignin;

[0008] The modifier is alkenyl succinic anhydride or alkyl ketene dimer. The carbon chain length of alkenyl succinic anhydride is C6 - C24, and the carbon chain length of alkyl ketene dimer is C10 - C20.

[0009] As a further scheme of the present invention: The dry modification specifically includes the following steps:

[0010] (1-1) Take lignin and place it in a stirring mixer, add an alkaline agent, and stir and mix evenly;

[0011] (1-2) Add the modifier and mix evenly again;

[0012] (1 - 3) Pour the mixture into a tray, place it in a forced-air drying oven, heat it up to 100 - 130 °C and react for 4 - 6 h to obtain the modified lignin.

[0013] As a further aspect of the present invention: The alkaline agent is at least one of anhydrous sodium carbonate, sodium hydroxide, and potassium hydroxide;

[0014] and / or, the carbon chain length of the alkenyl succinic anhydride is C12 - C18;

[0015] and / or, the carbon chain length of the alkyl ketene dimer is C14 - C18.

[0016] and / or, the dry modification includes the following raw materials in parts by weight: 100 parts of lignin, 3 - 7 parts of alkaline agent, and 130 - 170 parts of modifier.

[0017] As a further aspect of the present invention: After step (1 - 3), an operation of pulverizing the modified lignin is further included.

[0018] On the other hand, the present invention also provides a preparation method of modified lignin. The preparation method is organic solvent modification, including: dispersing lignin in an organic solvent, adding a modifier for reaction, and distilling out the organic solvent under negative pressure to obtain the modified lignin;

[0019] The modifier is alkenyl succinic anhydride or alkyl ketene dimer. The carbon chain length of alkenyl succinic anhydride is C6 - C24, and the carbon chain length of alkyl ketene dimer is C10 - C20.

[0020] As a further aspect of the present invention: The organic solvent modification specifically includes the following steps:

[0021] (2 - 1) Add lignin to a reaction kettle, add an organic solvent and stir to disperse;

[0022] (2 - 2) Carry out condensation reflux, heat up to 80 - 120 °C, add a modifier and react for 3 - 6 h;

[0023] (2 - 3) After the reaction is completed, carry out negative pressure distillation to distill out the organic solvent to obtain the modified lignin.

[0024] As a further aspect of the present invention: The organic solvent is at least one of 1,4 - dioxane, dimethyl sulfoxide, N,N - dimethylacetamide, and dichloromethane;

[0025] and / or, the carbon chain length of the alkenyl succinic anhydride is C12 - C18;

[0026] And / or, the carbon chain length of the alkyl ketene dimer is C14-C18;

[0027] And / or, the organic solvent modification includes the following raw materials in parts by weight: 100 parts of lignin, 350-500 parts of organic solvent, and 130-170 parts of modifier.

[0028] As a further aspect of the present invention: after step (2-3), it further includes the operations of drying and pulverizing the modified lignin.

[0029] In the third aspect of the present invention, a modified lignin is provided, which is prepared by the above-mentioned preparation method of modified lignin.

[0030] In the fourth aspect of the present invention, the modified lignin prepared by the above-mentioned preparation method of modified lignin, or the application of the above-mentioned modified lignin in rubber is also provided.

[0031] The beneficial effects of the present invention are as follows:

[0032] (1) In the present invention, alkenyl succinic anhydride and alkyl ketene dimer are used as modifiers to chemically modify lignin. On the one hand, the modifier can introduce a double bond structure into the lignin molecule, significantly improving the reaction activity of lignin, enabling it to form a chemical bond with the rubber matrix. At the same time, by introducing a long carbon chain, the dispersibility and compatibility of lignin in the rubber matrix are effectively improved, thereby enhancing the reinforcing effect of lignin on rubber. On the other hand, after modification, alkenyl succinic anhydride and alkyl ketene dimer can also undergo esterification or grafting reactions with polar groups such as hydroxyl groups of lignin, introducing hydrophobic alkyl chains on the surface of lignin, reducing its polarity, and enhancing its compatibility with the non-polar rubber matrix. The hydrophobic alkyl chains cover the surface of lignin, reducing the polar difference with rubber and promoting uniform dispersion. The ester bonds or covalent bonds formed by alkyl ketene dimer and lignin enhance the stability of lignin particles, avoiding re-agglomeration caused by shear force during rubber processing, thereby improving the tensile strength of rubber. In addition, the modified lignin is dispersed in the rubber matrix as a filler, forming physical crosslinking points, restricting the movement of rubber molecular chains, and further improving the modulus and anti-deformation ability of rubber.

[0033] (2) The dry modification process of the present invention has the characteristics of simple production process and small environmental pollution. The organic solvent modification process has the advantages of high reaction efficiency and recyclable solvent. Specific Embodiments

[0034] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions in the following examples are carried out according to conventional methods and conditions, or selected according to the product instructions. In addition, the reagents and raw materials used in the present invention are all commercially available.

[0035] Example 1

[0036] A preparation method of dry-modified lignin specifically includes the following steps:

[0037] Step 1: Take 100 parts of lignin and place it in a stirring mixer, add 4 parts of anhydrous sodium carbonate and 1 part of sodium hydroxide, and stir and mix evenly;

[0038] Step 2: Add 130 parts of alkenyl succinic anhydride with a carbon chain length of C6 and mix evenly again;

[0039] Step 3: Pour the mixture into a tray, place it in a forced-air drying oven, heat it to 105 °C and react for 6 h;

[0040] Step 4: Crush it with a crusher to D 97 to about 100 μm.

[0041] Example 2

[0042] A preparation method of lignin modified by the organic solvent method specifically includes the following steps:

[0043] Step 1: Take 100 parts of lignin and add it to a reaction kettle, add 350 parts of 1,4-dioxane and stir to disperse;

[0044] Step 2: Carry out condensation reflux, heat it to 90 °C, add 130 parts of alkenyl succinic anhydride with a carbon chain length of C6 and react for 6 h;

[0045] Step 3: After the reaction is completed, carry out vacuum distillation to distill out 1,4-dioxane;

[0046] Step 4: Dry it at 110 °C for 4 h, and crush it with a crusher to D 97 to about 100 μm.

[0047] Example 3

[0048] A preparation method of dry-modified lignin specifically includes the following steps:

[0049] Step 1: Take 100 parts of lignin and place it in a stirring mixer, add 3 parts of anhydrous sodium carbonate and 2 parts of sodium hydroxide, and stir and mix evenly;

[0050] Step 2: Add 150 parts of alkyl ketene dimer with a carbon chain length of C10 and mix evenly again;

[0051] Step 3: Pour the mixture into a tray, place it in a forced-air drying oven, heat it to 120 °C and react for 4 h;

[0052] Step 4: Crush it with a crusher to D 97 to about 100 μm.

[0053] Example 4

[0054] A preparation method of organosolv-modified lignin specifically includes the following steps:

[0055] Step 1: Take 100 parts of lignin and add it to a reaction kettle, then add 400 parts of 1,4-dioxane and stir to disperse;

[0056] Step 2: Carry out condensation reflux, heat up to 100 °C, add 150 parts of alkyl ketene dimer with a carbon chain length of C10 and react for 4 h;

[0057] Step 3: After the reaction is completed, carry out vacuum distillation to distill out 1,4-dioxane;

[0058] Step 4: Dry at 110 °C for 4 h and pulverize with a pulverizer to D 97 to about 100 μm.

[0059] Example 5

[0060] A preparation method of dry-modified lignin specifically includes the following steps:

[0061] Step 1: Take 100 parts of lignin and place it in a stirring mixer, add 3 parts of anhydrous sodium carbonate and 2 parts of sodium hydroxide, and stir and mix evenly;

[0062] Step 2: Add 50 parts of alkenyl succinic anhydride with a carbon chain length of C24 and 90 parts of alkyl ketene dimer with a carbon chain length of C20 and mix evenly again;

[0063] Step 3: Pour the mixture into a tray, place it in a forced-air drying oven, heat up to 130 °C and react for 3 h;

[0064] Step 4: Pulverize with a pulverizer to D 97 to about 100 μm.

[0065] Example 6

[0066] A preparation method of organosolv-modified lignin specifically includes the following steps:

[0067] Step 1: Take 100 parts of lignin and add it to a reaction kettle, then add 450 parts of dimethyl sulfoxide and stir to disperse;

[0068] Step 2: Carry out condensation reflux, heat up to 100 °C, add 50 parts of alkenyl succinic anhydride with a carbon chain length of C24 and 90 parts of alkyl ketene dimer with a carbon chain length of C20 and react for 4 h;

[0069] Step 3: After the reaction is completed, carry out vacuum distillation to distill out dimethyl sulfoxide;

[0070] Step 4: Dry at 110°C for 4 h and grind with a pulverizer to a D 97 of about 100 μm.

[0071] Example 7

[0072] A preparation method of dry-modified lignin specifically includes the following steps:

[0073] Step 1: Take 100 parts of lignin and place it in a stirring mixer, add 4 parts of anhydrous sodium carbonate and 1 part of sodium hydroxide, and stir and mix evenly;

[0074] Step 2: Add 100 parts of alkenyl succinic anhydride with a carbon chain length of C15 and 30 parts of alkyl ketene dimer with a carbon chain length of C16 and mix evenly again;

[0075] Step 3: Pour the mixture into a tray and place it in a forced-air drying oven, heat up to 105°C and react for 6 h;

[0076] Step 4: Grind with a pulverizer to a D 97 of about 100 μm.

[0077] Example 8

[0078] A preparation method of organic solvent-modified lignin specifically includes the following steps:

[0079] Step 1: Take 100 parts of lignin and add it to a reaction kettle, add 500 parts of N,N-dimethylacetamide and stir to disperse;

[0080] Step 2: Carry out condensation reflux, heat up to 110°C, add 100 parts of alkenyl succinic anhydride with a carbon chain length of C15 and 35 parts of alkyl ketene dimer with a carbon chain length of C16 and react for 3 h;

[0081] Step 3: After the reaction is completed, carry out vacuum distillation to distill out N,N-dimethylacetamide;

[0082] Step 4: Dry at 110°C for 4 h and grind with a pulverizer to a D 97 of about 100 μm.

[0083] Example 9

[0084] A preparation method of dry-modified lignin specifically includes the following steps:

[0085] Step 1: Take 100 parts of lignin and place it in a stirring mixer, add 4 parts of anhydrous sodium carbonate and 1 part of sodium hydroxide, and stir and mix evenly;

[0086] Step 2: Add 170 parts of alkyl ketene dimer with a carbon chain length of C14 and mix evenly again;

[0087] Step 3: Pour the mixture into a tray, place it in a forced-air drying oven, heat it to 110 °C and react for 4 h;

[0088] Step 4: Crush it with a crusher to D 97 of about 100 μm.

[0089] Example 10

[0090] A preparation method of organosolv-modified lignin specifically includes the following steps:

[0091] Step 1: Take 100 parts of lignin and add it to a reaction kettle, and add 400 parts of 1,4-dioxane to stir and disperse;

[0092] Step 2: Carry out condensation reflux, heat it to 110 °C, and react with 170 parts of alkyl ketene dimer with a carbon chain length of C14 for 5 h;

[0093] Step 3: After the reaction, carry out vacuum distillation to distill out 1,4-dioxane;

[0094] Step 4: Dry it at 110 °C for 4 h, and crush it with a crusher to D 97 of about 100 μm.

[0095] Comparative Example 1

[0096] The difference from Example 7 is only that the modifier is replaced with maleic anhydride.

[0097] Comparative Example 2

[0098] The difference from Example 8 is only that the modifier is replaced with maleic anhydride.

[0099] Comparative Example 3

[0100] The difference from Example 7 is only that no basic agent is added.

[0101] Comparative Example 4

[0102] The difference from Example 8 is only that the organic solvent N,N-dimethylacetamide is replaced with tetrahydrofuran.

[0103] Comparative Example 5

[0104] Prepare modified lignin by the method in Example 1 of Patent CN 110437468A, specifically including:

[0105] Dissolve 5 g of sodium lignosulfonate in 50 mL of deionized water in a 100 mL beaker, then slowly add 20 mL of concentrated hydrochloric acid, and then perform ultrasonic treatment. Control the ultrasonic power at 200 W and the ultrasonic time at 5 min, and then control the ultrasonic power at 600 W and the ultrasonic time at 20 min. After the ultrasonic treatment, neutralize the solution with sodium hydroxide to neutrality and precipitate it in ethanol. Vacuum-dry the precipitated activated sodium lignosulfonate to constant weight for standby.

[0106] Add 20 mL of dimethyl sulfoxide solvent and 2 g of activated sodium lignosulfonate to a 100 mL beaker. After complete dissolution, add 1.6 g of triethylamine and 3 g of isooctadecyl succinic anhydride, and then place the beaker in a microwave device. Control the reaction time at 10 min. After the reaction, precipitate the modified sodium lignosulfonate obtained in diethyl ether.

[0107] Comparative Example 6

[0108] The lignin was not modified.

[0109] Comparative Example 7

[0110] Blank sample, replace the amount of lignin with the same amount of carbon black.

[0111] Effect Example

[0112] (1) Rubber preparation raw material formula

[0113] Formula: 100 parts of natural rubber, 35 parts of carbon black, 15 parts of lignin / modified lignin, 5 parts of zinc oxide, 3 parts of stearic acid, 2.5 parts of sulfur, 0.4 part of accelerator TBBS.

[0114] (2) Preparation method

[0115] Processing technology:

[0116] 1. Add natural rubber to an internal mixer and plasticate at 40 °C for 1 min;

[0117] 2. Add carbon black, lignin / modified lignin, and process oil and mix for 15 min;

[0118] 3. Add stearic acid and zinc oxide and mix for 10 min. Thin-pass the material on a two-roll mill and let it stand for 4 h;

[0119] 4. Add the mixed rubber to an internal mixer, add sulfur, scorch retarder, and accelerator at 80 °C and mix for 3 min. Then set the temperature of the two-roll mill at 60 °C, thin-pass the mixed rubber on the two-roll mill for shaping, and then discharge and let it stand for at least 4 h and at most 24 h.

[0120] Vulcanization process: Weigh a certain mass of the mixed rubber and use a mold with a thickness of 2 mm for shaping and vulcanization. The temperature of the vulcanizer is 140 °C, the vulcanization time is 40 min, and the pressure is 10 MPa.

[0121] (3) Rubber property testing

[0122] Test the tensile strength and Shore hardness of the samples according to GB / T 528 - 2009 and GB / T 531.1 - 2008 respectively.

[0123] Table 1 shows the rubber property data of the samples in the examples and comparative examples.

[0124] Table 1

[0125]

[0126]

[0127] As can be seen from Table 1, compared with unmodified lignin, the tensile strength and hardness of the rubbers prepared by adding modified lignin in Examples 1 - 10 have been significantly improved. Among them, the effect of modifying lignin by the organic solvent method is better than that of the dry method.

[0128] Finally, it should also be noted that in the present invention, the terms "comprising", "including" or any other variant thereof are intended to cover non - exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0129] Although the present disclosure has been disclosed above through the description of specific embodiments of the present disclosure, it should be understood that those skilled in the art can design various modifications, improvements or equivalents to the present disclosure within the spirit and scope of the appended claims. These modifications, improvements or equivalents should also be considered to be included within the scope claimed by the present disclosure.

Claims

1. A preparation method of modified lignin, characterized in that, The preparation method is dry modification, which includes: adding an alkaline agent to lignin, mixing evenly, then adding a modifier and mixing, and heating for reaction to obtain the modified lignin; The modifier is alkenyl succinic anhydride or alkyl ketene dimer. The carbon chain length of alkenyl succinic anhydride is C6 - C24, and the carbon chain length of alkyl ketene dimer is C10 - C20.

2. The preparation method of the modified lignin according to claim 1, wherein The dry modification specifically includes the following steps: (1 - 1) Put lignin in a stirring mixer, add an alkaline agent, and stir and mix evenly; (1 - 2) Add the modifier and mix evenly again; (1 - 3) Pour the mixture into a tray, place it in a forced-air drying oven, heat to 100 - 130 °C and react for 3 - 6 h to obtain the modified lignin.

3. The preparation method of the modified lignin according to claim 1, characterized in that, The alkaline agent is at least one of anhydrous sodium carbonate, sodium hydroxide, and potassium hydroxide; And / or, the carbon chain length of the alkenyl succinic anhydride is C12 - C18; And / or, the carbon chain length of the alkyl ketene dimer is C14 - C18; And / or, the dry modification includes the following raw materials in parts by weight: 100 parts of lignin, 3 - 7 parts of alkaline agent, and 130 - 170 parts of modifier.

4. The preparation method of the modified lignin according to claim 2, wherein After step (1 - 3), an operation of pulverizing the modified lignin is further included.

5. A preparation method of modified lignin, characterized in that, The preparation method is organic solvent modification, which includes: dispersing lignin in an organic solvent, adding a modifier for reaction, and distilling out the organic solvent under negative pressure to obtain the modified lignin; The modifier is alkenyl succinic anhydride or alkyl ketene dimer. The carbon chain length of alkenyl succinic anhydride is C6 - C24, and the carbon chain length of alkyl ketene dimer is C10 - C20.

6. The preparation method of the modified lignin according to claim 5, characterized in that The organic solvent modification specifically includes the following steps: (2 - 1) Add lignin to a reaction kettle, add an organic solvent and stir to disperse; (2 - 2) Carry out condensation reflux, heat to 80 - 120 °C, add a modifier and react for 3 - 6 h; (2 - 3) After the reaction is completed, carry out negative pressure distillation to distill out the organic solvent to obtain the modified lignin.

7. The preparation method of the modified lignin according to claim 5, wherein, The organic solvent is at least one of 1,4 - dioxane, dimethyl sulfoxide, N,N - dimethylacetamide, and dichloromethane; And / or, the carbon chain length of the alkenyl succinic anhydride is C12 - C18; And / or, the carbon chain length of the alkyl ketene dimer is C14 - C18; And / or, the organic solvent modification includes the following raw materials in parts by weight: 100 parts of lignin, 350 - 500 parts of organic solvent, and 130 - 170 parts of modifier.

8. The preparation method of the modified lignin according to claim 6, wherein, After step (2 - 3), operations of drying and pulverizing the modified lignin are further included.

9. A modified lignin, which is prepared by the preparation method of the modified lignin described in claims 1 - 8.

10. An application of a modified lignin prepared by the preparation method of the modified lignin described in claims 1 - 8, or the modified lignin described in claim 9 in rubber.

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