Preparation method of lignin and carbon fiber synergistic oxidation modified acidic alcohol aqueous dispersion
The preparation method of acidic alcohol aqueous dispersion modified by synergistic oxidation of lignin and carbon fiber solves the problem of easy agglomeration during carbon fiber dispersion, and achieves uniform dispersion of carbon fiber and improved stability of composite material.
Patent Information
- Application Number
- CN202511268326.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-05
- Publication Date
- 2025-11-04
AI Technical Summary
Carbon fibers tend to agglomerate during dispersion, leading to uneven stress distribution within the composite material. Existing dispersants have poor stability, which limits their application.
A method for preparing an acidic alcohol aqueous dispersion modified by synergistic oxidation of lignin and carbon fiber involves oxidizing lignin and carbon fiber with nitric acid, followed by ultrasonic dispersion in an ethanol-nitric acid-water ternary dispersion system. This introduces negatively charged functional groups such as hydroxyl and carboxyl groups, enhancing electrostatic repulsion.
Uniform dispersion of long carbon fibers was achieved, which improved the stability and dispersion effect of the composite material, enhanced the repulsion between carbon fibers and the solution, and promoted the effective dispersion of carbon fibers.
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Figure CN120889128A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of carbon fiber dispersion technology, and in particular to a method for preparing an acidic alcohol aqueous dispersion in which lignin and carbon fiber are synergistically oxidized and modified. Background Technology
[0002] Carbon fiber possesses high strength, high temperature resistance, and excellent electrical conductivity, making it a promising material for lithium-ion battery separators. The surface of carbon fiber is primarily composed of graphitized carbon atoms (-cc-), lacking polar functional groups (such as hydroxyl and carboxyl groups), resulting in weak interfacial interactions with polar solvents or matrices and poor wettability. While carbon fiber diameters are only 7-10 μm, their lengths can reach millimeters. This high aspect ratio makes them prone to forming bundles or network aggregates through mechanical entanglement or van der Waals forces. The numerous voids within these aggregated carbon fibers lead to uneven stress distribution within the composite material, easily triggering crack propagation. The dispersion performance of carbon fiber is influenced by various factors, including carbon fiber length, type of dispersion solvent, surface functional groups, and dispersant. In pure water, carbon fiber dispersion is primarily due to electrostatic repulsion, while in ethanol, its dispersion performance is influenced by the synergistic effect of hydrogen bonding and hydrophobic interactions. Oxidation treatment (such as nitric acid oxidation) is an effective method to introduce polar functional groups such as carboxyl groups (-COOH) and hydroxyl groups (-OH) on the fiber surface. Water molecules combine with the functional groups on the surface of oxidized carbon fiber through hydrogen bonds to form a double electric layer structure, which disperses the fiber through electrostatic repulsion.
[0003] In addition, surfactant-based dispersants can adsorb onto the carbon fiber surface to form a charged layer or steric hindrance, inhibiting particle agglomeration. However, commonly used anionic stabilizers such as sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), and sodium oleate have problems such as poor stability and reaction with carbon fibers, which are not conducive to maintaining the stability of the carbon fiber dispersion and limit the application of carbon fibers.
[0004] In view of this, it is necessary to design an improved method for preparing an acidic alcohol aqueous dispersion with synergistic oxidative modification of lignin and carbon fiber to solve the above problems. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing an acidic alcohol aqueous dispersion modified by the synergistic oxidation of lignin and carbon fiber.
[0006] To achieve the above-mentioned objective, in a first aspect, the present invention provides a method for preparing an acidic alcohol aqueous dispersion modified by the synergistic oxidation of lignin and carbon fiber, comprising the following steps:
[0007] Lignin and carbon fibers are added to a nitric acid solution and reacted at 20-80℃ for 1-2 hours to obtain a mixture consisting of oxidized lignin, oxidized carbon fibers, and a nitric acid solution, wherein the length of the carbon fibers is 7-11 mm.
[0008] The mixture is added with an ethanol aqueous solution to form an ethanol-nitric acid-water ternary dispersion system; then, the obtained mixture is subjected to dispersion treatment under ultrasonic condition to obtain the acidic alcohol aqueous dispersion.
[0009] Preferably, the volume fraction of the nitric acid solution is 10-30 vol%, which is prepared by using a nitric acid aqueous solution with a concentration of 65-70 wt%, and the mass ratio of lignin, carbon fiber and volume of the nitric acid solution is (10-40) g:(10-40) g:1 L.
[0010] Preferably, the mass ratio of lignin to carbon fiber is 1:1, and the lignin is added in an amount of 10-40 g per 1 L of the nitric acid solution.
[0011] Preferably, the volume fraction of the ethanol aqueous solution is 40-60 vol%, and the volume ratio of the nitric acid solution to the ethanol aqueous solution is 1:1.
[0012] Preferably, the power of the ultrasonic is 60-80 W, the time is 10-30 min, and the temperature is 25-30℃.
[0013] Preferably, the ethanol-nitric acid-water ternary dispersion system is prepared by using the following components in the initial mixing volume ratio: ethanol 20-30 vol%, nitric acid 5-15 vol%, and the balance being water.
[0014] In the second aspect, the application provides a use of the acidic alcohol aqueous dispersion in the preparation of a battery separator material.
[0015] The application has the following beneficial effects:
[0016] 1. The application provides a preparation method of the acidic alcohol aqueous dispersion of lignin and carbon fiber synergistically oxidized and modified, which is realized by first oxidizing the lignin and the carbon fiber by using nitric acid and then subjecting to dispersion treatment in a specific dispersion system. In the oxidation process, the surface of the carbon fiber can be introduced with negatively charged functional groups such as hydroxyl and carboxyl groups, the free phenolic hydroxyl groups can be released by breaking the aryl ether of the lignin, and the nitro and carboxyl groups can be introduced into the side chain of the lignin, so as to increase the content of the negatively charged functional groups on the surface of the lignin, increase the electrostatic repulsion between the lignin and the carbon fiber, and facilitate the uniform dispersion of the long carbon fiber (length 7-11 mm).
[0017] 2. The preparation method provided by the application can improve the dispersion state of the dispersion by adjusting the lignin addition amount, the composition of the dispersion system and the ultrasonic condition in the preparation process, so as to finally obtain the acidic alcohol aqueous dispersion with uniform dispersion. BRIEF DESCRIPTION OF DRAWINGS
[0018] Figure 1An optical photograph of a paper sheet made by papermaking the dispersion liquid prepared in Example 1 of the present application;
[0019] Figure 2 An optical photograph of a paper sheet made by papermaking the dispersion liquid prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION
[0020] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0021] Here, it should also be noted that, in order to avoid obscuring the present application due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present application are shown in the accompanying drawings, and other details not closely related to the present application are omitted.
[0022] In addition, it should also be noted that the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or equipment.
[0023] The present application provides a preparation method of an acidic alcohol aqueous dispersion liquid of lignin and carbon fiber synergistically oxidized and modified, comprising the following steps:
[0024] The lignin and the carbon fiber are added into a nitric acid solution, and reacted at 20-80℃ for 1-2h, so that the lignin and the carbon fiber are oxidized by the nitric acid, and a mixture composed of oxidized lignin, oxidized carbon fiber and the nitric acid solution is prepared;
[0025] An alcohol aqueous solution is added into the mixture to form an alcohol-nitric acid-water ternary dispersion system; then, the obtained mixture is dispersed under ultrasonic condition, so that the dispersion liquid is prepared.
[0026] In the above technical solution, the lignin and the carbon fiber are first oxidized by the nitric acid, and then dispersed, so that, in the process of oxidation by the nitric acid, the carbon fiber surface can be introduced with negatively charged functional groups such as hydroxyl and carboxyl groups, the free phenolic hydroxyl groups are released from the broken aryl ether of the lignin, and the nitro and carboxyl groups are introduced into the side chain of the lignin, so as to increase the content of the negatively charged functional groups on the surface of the lignin, to increase the electrostatic repulsion between the lignin and the carbon fiber, and to achieve the purpose of dispersing the carbon fiber.
[0027] Specifically, the formation mechanism of the dispersion liquid is as follows: the low surface tension of the alcohol enables it to quickly penetrate into the gap between the carbon fiber bundles, to destroy the van der Waals force between the carbon fibers, and to reduce the physical agglomeration inside the carbon fibers; the introduction of the nitric acid and the presence of water can provide a polar acidic environment, so that a large amount of hydrogen ions (H+), which are positively charged, are adsorbed by the negatively charged functional groups on the surface of the oxidized carbon fiber and the oxidized lignin in the system, so as to realize the dispersion of the carbon fiber and the lignin.+ ), and the repulsion between the carbon fiber and the lignin and the repulsion between the carbon fiber and the solution are increased, so that the effective dispersion of the carbon fiber, especially the long carbon fiber, is realized.
[0028] In some embodiments, the mass ratio of the lignin to the carbon fiber is 1:1, the length of the carbon fiber is 7-11 mm, and the lignin is specifically alkali lignin. By controlling the mass ratio of the lignin to the carbon fiber to be 1:1, the effective dispersion of the carbon fiber can be ensured. If the lignin is added in an excessive amount, the carbon fiber is surrounded by an excessive amount of lignin due to the long length (millimeter level) of the carbon fiber and the small size (micron or nanometer level) of the lignin. At this time, the repulsion between the carbon fiber and the lignin is increased, and the repulsion between the carbon fibers is too small, resulting in a decrease in the dispersion performance of the carbon fiber. If the lignin is added in a small amount, the lignin for wrapping the carbon fiber is too small, and the repulsion between the carbon fiber and the lignin is not enough, so the dispersion purpose cannot be achieved.
[0029] In some embodiments, the nitric acid solution is prepared from concentrated nitric acid, the volume fraction of the concentrated nitric acid is 10-30 vol%, and the ratio of the mass (g) of the lignin, the mass (g) of the carbon fiber, and the volume (L) of the nitric acid solution is (10-40):(10-40):1. It should be noted that the concentrated nitric acid herein refers to a nitric acid aqueous solution with a concentration of 65-70 wt%, which corresponds to HNO3. + The concentration is 10.0-11.1 mol / L.
[0030] In some embodiments, the volume fraction of the ethanol aqueous solution is 40-60 vol%, the volume ratio of the nitric acid solution to the ethanol aqueous solution is 1:1, the volume fraction of the ethanol in the ethanol-nitric acid-water ternary dispersion system is 20-30 vol%, the volume fraction of the nitric acid is 5-15 vol%, and the balance is water. The sum of the volume fractions of the ethanol, the nitric acid, and the water is 100%.
[0031] In some embodiments, the power of the ultrasonic is 60-80 W, the time is 10-30 min, and the temperature is 25-30℃.
[0032] The preparation method of the lignin and carbon fiber synergistically oxidized acidic alcohol water dispersion liquid provided by the present application is further described below in combination with specific embodiments:
[0033] Embodiment 1
[0034] In this embodiment, a lignin and carbon fiber synergistically oxidized acidic alcohol water dispersion liquid is prepared, and the preparation method thereof includes the following steps:
[0035] 5g of carbon fiber with a length of 9mm and 5g of alkali lignin were added into 250mL of nitric acid solution, and nitration oxidation was carried out at 60℃ for 1.5h; after the reaction was completed, the reaction product was cooled to 25℃ to obtain a mixture composed of oxidized alkali lignin, oxidized carbon fiber and nitric acid solution; wherein the volume fraction of the nitric acid solution was 20vol%, which was obtained by slowly adding 50mL of concentrated nitric acid into 200mL of water and then diluting to 250mL in a volumetric flask;
[0036] The above mixture was added into an ethanol solution composed of 125mL of ethanol and 125mL of water, the volume fraction of ethanol was 50vol%, an ethanol-nitric acid-water ternary dispersion system with a volume ratio of 25:10:65 (i.e., the volume ratio of C2H5OH, HNO3 and H2O) was formed, and the concentrations of oxidized carbon fiber and oxidized lignin were both 10g / L; then, ultrasonic dispersion was carried out at 25℃ for 20min at a power of 70W to disperse the above mixture, and thus an acidic alcohol aqueous dispersion liquid with uniformly dispersed carbon fiber was prepared.
[0037] It should be noted that, unless otherwise specified, the reagents and raw materials used in the embodiments of the present application can be obtained by market purchase.
[0038] Example 2
[0039] In this embodiment, an acidic alcohol aqueous dispersion liquid of lignin and carbon fiber synergistically oxidized and modified was prepared, and the preparation method included the following steps:
[0040] 10g of carbon fiber with a length of 9mm and 10g of lignin were added into 250mL of nitric acid solution, and nitration oxidation was carried out at 40℃ for 2h; after the reaction was completed, the reaction product was cooled to 25℃ to obtain a mixture composed of oxidized lignin, oxidized carbon fiber and nitric acid solution; wherein the volume fraction of the nitric acid solution was 30vol%, which was obtained by slowly adding 75mL of concentrated nitric acid into 175mL of water and then diluting to 250mL in a volumetric flask;
[0041] The above mixture was added into an ethanol solution composed of 125mL of ethanol and 125mL of water, the volume fraction of ethanol was 50vol%, an ethanol-nitric acid-water ternary dispersion system with a volume ratio of 25:35:40 was formed, and the concentrations of oxidized carbon fiber and oxidized lignin were both 20g / L; then, ultrasonic dispersion was carried out at 25℃ for 25min at a power of 65W to disperse the above mixture, and thus an acidic alcohol aqueous dispersion liquid with uniformly dispersed carbon fiber was prepared.
[0042] Example 3
[0043] In this embodiment, an acidic alcohol aqueous dispersion liquid of lignin and carbon fiber synergistically oxidized and modified was prepared, and the preparation method included the following steps:
[0044] 8g of carbon fibers with a length of 11mm and 8g of lignin were added into 250mL of nitric acid solution, and nitration oxidation was carried out at 50℃ for 1h. After the reaction was completed, the reaction product was cooled to 25℃ to obtain a mixture composed of oxidized lignin, oxidized carbon fibers and nitric acid solution; wherein the volume fraction of the nitric acid solution was 25vol%, which was obtained by slowly adding 62.5mL of concentrated nitric acid into 187.5mL of water and then diluting to 250mL in a volumetric flask;
[0045] The above mixture was added into an ethanol solution composed of 100mL of ethanol and 150mL of water, and the volume fraction of ethanol was 40vol%, forming a ternary dispersion system of ethanol-nitric acid-water with a volume ratio of 20:12.5:67.5, and the concentrations of oxidized carbon fibers and oxidized lignin were both 16g / L. Then, the above mixture solution was dispersed at 25℃ for 15min with an ultrasonic power of 75W, and an acidic alcohol aqueous dispersion liquid with uniformly dispersed carbon fibers was prepared.
[0046] Examples 4 to 7
[0047] Examples 4 to 7 are only different from Example 1 in that the compositions of the parts of the ternary dispersion system are different from those of Example 1, and the rest of the experimental parameters and experimental conditions are the same as those of Example 1, which will not be repeated here.
[0048] The compositions of the ternary dispersion systems in Examples 1 to 7 and the properties of the dispersion liquids obtained under the corresponding conditions are shown in Table 1. As can be seen from the data in the table, the composition of the ternary dispersion system can affect the dispersibility of the dispersion liquid, and the dispersibility is better within a certain range. This is because the low surface tension of ethanol in the ternary dispersion system allows it to quickly penetrate into the gap between the carbon fiber bundles, destroy the van der Waals force between the carbon fibers, reduce the physical agglomeration inside the carbon fibers, and promote the dispersion of the carbon fibers. When the ethanol content is too low / high water content (Example 6), the surface tension provided by ethanol is not enough, resulting in insufficient dispersion capacity of the ternary system, and the carbon fibers cannot be effectively dispersed. When the ethanol content is too high / low water content (Example 7), the surface tension provided by ethanol is too large, and the dispersion environment space is limited, which cannot provide an effective dispersion solution environment for the carbon fibers. Therefore, only a limited space can be dispersed, and the carbon fibers are locally aggregated, the carbon fibers in the whole solution are not uniformly dispersed, and the dispersion effect is not good.
[0049] Table 1 Comparison of the compositions of the ternary dispersion systems in Examples 1 to 7 and the properties of the dispersion liquids obtained under the corresponding conditions
[0050]
[0051]
[0052] Examples 8 to 11
[0053] Examples 8 to 11 differ from Example 1 only in that the amount of carbon fiber and lignin added is different from Example 1, and the rest of the experimental parameters and experimental conditions are the same as Example 1, which will not be repeated here.
[0054] The amount of carbon fiber and lignin added in Example 1 and Examples 8 to 11 and the performance of the dispersion obtained under the corresponding conditions are compared in Table 2, and the data in the table show that too low or too high an amount of lignin cannot achieve good dispersion effect. This is because when the amount of lignin is too low, the amount of lignin is not enough to effectively disperse the carbon fiber; when the amount of lignin is too high, the carbon fiber is surrounded by an excessive amount of lignin (relative to the 1:1 mass ratio of lignin to carbon fiber), and the repulsion between carbon fiber and lignin increases, while the repulsion between carbon fiber and carbon fiber is less. Since the carbon fiber is long and the lignin particles are small, the dispersion performance of the carbon fiber may decrease because the repulsion between lignin and carbon fiber is less than the repulsion between carbon fiber and carbon fiber.
[0055] Table 2 Comparison of the amount of carbon fiber and lignin added in Example 1 and Examples 8 to 11 and the performance of the dispersion obtained under the corresponding conditions
[0056]
[0057] Examples 12 to 15
[0058] Examples 12 to 15 differ from Example 1 only in that the conditions for ultrasonic dispersion are different from Example 1, and the rest of the experimental conditions and experimental parameters are the same as Example 1, which will not be repeated here.
[0059] The conditions for ultrasonic dispersion in Example 1 and Examples 12 to 15 and the performance of the dispersion obtained under the corresponding conditions are compared in Table 3, and the results show that too short ultrasonic time cannot achieve good dispersion effect, while too long ultrasonic time will cause the dispersed carbon fiber to aggregate again, resulting in poor dispersion effect. Therefore, considering the ultrasonic dispersion time of 10-30 min, the dispersion effect is good and the energy consumption is low.
[0060] Table 3 Comparison of the conditions for ultrasonic dispersion in Example 1 and Examples 12 to 15 and the performance of the dispersion obtained under the corresponding conditions
[0061]
[0062] Comparative Example 1
[0063] Comparative Example 1 differs from Example 1 only in that the step of nitration and oxidation is omitted, i.e., after mixing the carbon fiber and lignin, they are directly added to a ternary dispersion system of ethanol-nitric acid-water in a volume ratio of 25:10:65 for dispersion, and the rest of the experimental parameters and experimental conditions are the same as Example 1, which will not be repeated here.
[0064] The optical photograph of the paper sheet made from the dispersion liquid prepared in Example 1 is shown in Figure 1, and the optical photograph of the paper sheet made from the dispersion liquid prepared in Comparative Example 1 is shown in Figure 2. Figure 1 Figure 2 By comparing the two figures, it can be seen that the paper sheet made from the carbon fibers dispersed in Example 1 is smooth and free of agglomeration, while the paper sheet made in Comparative Example 1 is not smooth and has agglomeration. It should be noted that the method for making the paper sheet is a common method in the art, and thus is not described in detail here.
[0065] Comparative Example 2
[0066] Comparative Example 2 differs from Example 1 only in that no lignin is added, i.e., after nitration and oxidation of the carbon fibers, the mixture is directly added to a ternary dispersion system of ethanol-nitric acid-water in a volume ratio of 25:10:65, and the rest of the experimental parameters and experimental conditions are the same as in Example 1, and thus are not described again here.
[0067] Comparative Example 3
[0068] Comparative Example 3 differs from Example 1 only in that the ternary dispersion system of ethanol-nitric acid-water is replaced by a dispersion system composed of nitric acid and water, i.e., 250 mL of water is added to the mixture obtained after nitration and oxidation, and the rest of the experimental parameters and experimental conditions are the same as in Example 1, and thus are not described again here. The performance comparison of the dispersion liquids obtained in Example 1 and Comparative Example 1 is shown in Table 4, which shows that too low (as low as 0) content of ethanol cannot achieve good dispersion effect, which is of the same type as the result of Example 6, and thus is not described again here.
[0069] Comparative Example 4
[0070] Comparative Example 4 differs from Example 1 only in that nitric acid is not used for oxidation of lignin and carbon fibers, but is replaced by a sulfuric acid solution of the same volume, forming a 20% sulfuric acid solution; after the oxidation reaction is completed, 125 mL of ethanol and 125 mL of water are added to the above mixture to form an ethanol solution with a volume fraction of 50 vol%, and a ternary dispersion system of ethanol-sulfuric acid-water in a volume ratio of 25:10:65 is formed, and the rest of the experimental parameters and experimental conditions are the same as in Example 1, and thus are not described again here.
[0071] The properties of the dispersions prepared in Example 1 and Comparative Examples 1 to 4 are compared in Table 4, and the results show that the stability of the dispersion prepared in Example 1 is better than that of Comparative Examples 1 to 4, because: sulfuric acid does not have the ability to oxidize lignin or carbon fibers, and under the conditions of Example 1, the oxidation by nitric acid can introduce negatively charged functional groups on the surface of carbon fibers and lignin, to increase the electrostatic repulsion between them, which is conducive to the uniform dispersion of carbon fibers; at the same time, during the subsequent dispersion process, the dispersion in the ternary dispersion system composed of ethanol, nitric acid and water can provide a favorable dispersion environment for the dispersion of carbon fibers by the surface tension provided by the ethanol molecules, and the strong polar acidic environment formed by nitric acid and water can increase the repulsion between carbon fibers and lignin and between carbon fibers and the solution. Under the combined action of the above factors, effective dispersion of carbon fibers can be achieved.
[0072] Table 4 Comparison of properties of dispersions prepared in Example 1 and Comparative Examples 1 to 4
[0073]
[0074] The above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.
Claims
1. A method for preparing an acidic alcohol aqueous dispersion synergistically oxidized and modified by lignin and carbon fiber, characterized in that, Includes the following steps: Lignin and carbon fibers are added to a nitric acid solution and reacted at 20-80℃ for 1-2 hours to obtain a mixture consisting of oxidized lignin, oxidized carbon fibers, and a nitric acid solution, wherein the length of the carbon fibers is 7-11 mm. An aqueous ethanol solution is added to the mixture to form an ethanol-nitric acid-water ternary dispersion system; then, the resulting mixture is dispersed under ultrasonic conditions to obtain the acidic alcohol-water dispersion.
2. The preparation method according to claim 1, characterized in that, The nitric acid solution has a volume fraction of 10-30 vol%, which is prepared from a nitric acid aqueous solution with a concentration of 65-70 wt%. The ratio of the mass of lignin, the mass of carbon fiber, and the volume of nitric acid solution is (10-40) g: (10-40) g: 1 L.
3. The preparation method according to claim 1, characterized in that, The mass ratio of lignin to carbon fiber is 1:
1. The rule for adding lignin is: 10-40g of lignin is added to every 1L of nitric acid solution.
4. The preparation method according to claim 1, characterized in that, The volume fraction of the ethanol-water solution is 40-60 vol%, and the volume ratio of the nitric acid solution to the ethanol-water solution is 1:
1.
5. The preparation method according to claim 1, characterized in that, The ultrasound power is 60-80W, the duration is 10-30min, and the temperature is 25-30℃.
6. The preparation method according to claim 2, characterized in that, The ethanol-nitric acid-water ternary dispersion system is composed of the following components in the initial mixing volume ratio: 20-30 vol% ethanol, 5-15 vol% nitric acid, and the remainder is water.
7. The application of an acidic alcohol aqueous dispersion prepared by any one of claims 1-6 in the preparation of battery separator materials.