Preparation method of carbon fiber slurry for improving uniformity performance of carbon paper

Abstract

The invention discloses a preparation method of carbon fiber slurry for improving uniformity performance of carbon paper, which comprises the following steps: step 1, chopping carbon fibers into 4-8mm, adding the carbon fibers into 0.5-1.5 mol / L NaOH solution, stirring, standing for 25-30 minutes, and removing grease impurities on the surfaces of the carbon fibers; step 2, heating the NaOH solution to 60-70 DEG C, then adding 1-5g / L of polydopamine into the NaOH solution, stirring until the color of the mixed solution becomes dark black, and modifying the carbon fibers by using the polydopamine; step 3, filtering and drying the modified carbon fibers to obtain polydopamine modified carbon fibers; 4, alkali lignin and urea are added into a 0.5-1.5 mol / L NaOH solution to form dispersion liquid, the concentration of the alkali lignin in the dispersion liquid is 1-2 wt%, the concentration of the urea in the dispersion liquid is 3-8 wt%, then the polydopamine modified carbon fibers are added into the dispersion liquid, and dispersion pretreatment is completed. The method can realize modification and dispersion of the carbon fibers, further can improve the paper forming performance of the carbon paper, and has the characteristics of low cost and easiness in implementation.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon paper, and in particular to a method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper. Background Art

[0002] Carbon fiber itself has many excellent properties and is often used to process into a variety of high-performance and composite biomass materials. The surface of carbon fiber is uneven, similar to a graphite structure with many grooves and protrusions all over its surface. These grooves reduce the friction between carbon fibers, making it difficult to disperse the carbon fibers. At the same time, the carbon fibers are connected together in the form of covalent bonds, which reduces the number of carbon fiber surface groups, reduces hydrophilicity, and is more likely to agglomerate in water, resulting in reduced surface performance and difficulty in dispersion. Therefore, the most important technology in the production of wet-laid carbon paper is to evenly disperse the carbon fibers in water and increase the strength of the paper. However, since carbon fibers are prone to flocculation and lack binding properties, how to pre-treat the carbon fibers during the manufacturing process to improve the uniformity and strength of the paper has become a common problem to be solved in the industry. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper. The present invention can achieve the modification and dispersion of carbon fibers, thereby improving the paper-forming performance of carbon paper, and has the characteristics of low cost and easy implementation.

[0004] The technical solution of the present invention is a method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, comprising the following steps:

[0005] Step 1, add carbon fiber to 0.5-1.5 mol / L NaOH solution, stir and let stand for 25-30 minutes to remove grease impurities on the surface of carbon fiber;

[0006] Step 2, heating the NaOH solution to 60-70° C., then adding 1-5 g / L of polydopamine to the NaOH solution and stirring until the color of the mixed solution turns dark black, and modifying the carbon fiber with polydopamine;

[0007] Step 3, filtering and drying the modified carbon fiber to obtain polydopamine modified carbon fiber;

[0008] Step 4: adding alkali lignin and urea to a 0.5-1.5 mol / L NaOH solution to form a dispersion, wherein the concentration of alkali lignin in the dispersion is 1-2wt%, and the concentration of urea is 3-8wt%, and then adding polydopamine-modified carbon fiber to the dispersion to complete the dispersion pretreatment.

[0009] In the above-mentioned method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, in step 1, the concentration of the sodium hydroxide solution is 1 mol / L.

[0010] In the aforementioned method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, in step 2, the heating temperature of the NaOH solution is 65°C.

[0011] In the aforementioned method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, in step 2, 3 g / L of polydopamine is added to the NaOH solution.

[0012] In the aforementioned method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, in step 3, the filtered modified carbon fiber is dried at 60°C.

[0013] In the aforementioned method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, in step 4, the concentration of alkali lignin in the dispersion is 1.5 wt %.

[0014] In the aforementioned method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, in step 4, the concentration of urea in the dispersion is 5 wt %.

[0015] In the aforementioned method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, the length of the carbon fiber is 6 mm.

[0016] Compared with the prior art, the present invention first utilizes polydopamine to modify carbon fiber, which can significantly improve the surface energy, wettability and surface roughness of carbon fiber, and then configures an alkali lignin-urea alkali solution system. Under this system, the active groups of alkali lignin are used to further modify the carbon fiber, thereby improving the hydrophilic group of the carbon fiber, thereby increasing the dispersion ability of the carbon fiber in the water phase, reducing the interaction force between carbon fibers, reducing the internal friction between carbon fibers, and achieving uniform dispersion of the carbon fiber. The carbon fiber pretreated by the present invention is used to make carbon paper, which can provide air permeability of carbon paper, reduce resistivity, and improve conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a dispersion diagram of carbon fibers in the examples. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0019] Embodiment 1: A method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, comprising the following steps:

[0020] Step 1, cut the carbon fiber into 4mm, then add the carbon fiber into 0.5mol / L NaOH solution, stir and let stand for 25min to remove grease impurities on the surface of the carbon fiber;

[0021] Step 2, heating the NaOH solution to 60° C., then adding 3 g / L of polydopamine to the NaOH solution and stirring until the color of the mixed solution turns dark black, and using polydopamine to modify the carbon fiber;

[0022] Step 3, filtering the modified carbon fiber and drying it at 60° C. to obtain polydopamine modified carbon fiber;

[0023] Step 4: adding alkali lignin and urea to a 1 mol / L NaOH solution to form a dispersion, wherein the concentration of alkali lignin in the dispersion is 2 wt %, and the concentration of urea is 3 wt %, and then adding polydopamine-modified carbon fiber to the dispersion to complete the dispersion pretreatment.

[0024] Embodiment 2: A method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, comprising the following steps:

[0025] Step 1, cut the carbon fiber into 6mm, then add the carbon fiber into 0.75mol / L NaOH solution, stir and let stand for 28min to remove grease impurities on the surface of the carbon fiber;

[0026] Step 2, heating the NaOH solution to 65° C., then adding 5 g / L of polydopamine to the NaOH solution and stirring until the color of the mixed solution turns dark black, and modifying the carbon fiber with polydopamine;

[0027] Step 3, filtering the modified carbon fiber and drying it at 60° C. to obtain polydopamine modified carbon fiber;

[0028] Step 4: adding alkali lignin and urea to a 1.25 mol / L NaOH solution to form a dispersion, wherein the concentration of alkali lignin in the dispersion is 2 wt %, and the concentration of urea is 8 wt %, and then adding polydopamine-modified carbon fiber to the dispersion to complete the dispersion pretreatment.

[0029] Embodiment 3: A method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, comprising the following steps:

[0030] Step 1, cut the carbon fiber into 8mm pieces, then add the carbon fiber into 1mol / L NaOH solution, stir and let stand for 30min to remove grease impurities on the surface of the carbon fiber;

[0031] Step 2, heating the NaOH solution to 70° C., then adding 1 g / L of polydopamine to the NaOH solution and stirring until the color of the mixed solution turns dark black, and modifying the carbon fiber with polydopamine;

[0032] Step 3, filtering the modified carbon fiber and drying it at 60° C. to obtain polydopamine modified carbon fiber;

[0033] Step 4: adding alkali lignin and urea to 1 mol / L NaOH solution to form a dispersion, wherein the concentration of alkali lignin in the dispersion is 1.5wt%, and the concentration of urea is 5wt%, and then adding polydopamine-modified carbon fiber to the dispersion to complete the dispersion pretreatment.

[0034] Embodiment 4: A method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, comprising the following steps:

[0035] Step 1, cut the carbon fiber into 6mm, then add the carbon fiber into 1.5mol / L NaOH solution, stir and let stand for 25min to remove grease impurities on the surface of the carbon fiber;

[0036] Step 2, heating the NaOH solution to 60° C., then adding 3 g / L of polydopamine to the NaOH solution and stirring until the color of the mixed solution turns dark black, and using polydopamine to modify the carbon fiber;

[0037] Step 3, filtering the modified carbon fiber and drying it at 65° C. to obtain polydopamine modified carbon fiber;

[0038] Step 4: adding alkali lignin and urea to a 1 mol / L NaOH solution to form a dispersion, wherein the concentration of alkali lignin in the dispersion is 2 wt %, and the concentration of urea is 4 wt %, and then adding polydopamine-modified carbon fiber to the dispersion to complete the dispersion pretreatment.

[0039] Embodiment 5: A method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, comprising the following steps:

[0040] Step 1, cut the carbon fiber into 6mm, then add the carbon fiber into 1mol / L NaOH solution, stir and let stand for 25min to remove grease impurities on the surface of the carbon fiber;

[0041] Step 2, heating the NaOH solution to 65° C., then adding 3 g / L of polydopamine to the NaOH solution and stirring until the color of the mixed solution turns dark black, and modifying the carbon fiber with polydopamine;

[0042] Step 3, filtering the modified carbon fiber and drying it at 60° C. to obtain polydopamine modified carbon fiber;

[0043] Step 4: adding alkali lignin and urea to 1 mol / L NaOH solution to form a dispersion, wherein the concentration of alkali lignin in the dispersion is 1.5wt%, and the concentration of urea is 5wt%, and then adding polydopamine-modified carbon fiber to the dispersion to complete the dispersion pretreatment.

[0044] Comparative Example 1: Prepare 1 mol / L sodium hydroxide solution, add carbon fiber and carry out ultrasonic stirring for 15 minutes, the power of ultrasonic stirring is 500W.

[0045] The applicant has demonstrated the dispersed carbon fibers of Examples 1-5 and Comparative Examples, as shown in FIG. Figure 1 As shown. Figure 1 It can be seen that in the comparative example, although the carbon fiber is dispersed by using alkali solution and ultrasonic treatment, there is still obvious agglomeration in some parts of the carbon fiber, and there are more agglomerations. The dispersion of the carbon fiber shown in Examples 1-5 of the present invention is greatly improved compared with that in Comparative Example 1, and the carbon fiber is more evenly dispersed. Further, the stability test of the carbon fiber was carried out by using a multiple light scattering instrument for three hours, and the data was recorded every half an hour. The results are shown in Table 1:

[0046] 30min 60min 90min 120min 150min 180min Example 1 10.17 18.13 24.14 28.18 30.94 32.92 Example 2 11.12 14.59 16.13 17.22 19.21 20.75 Example 3 9.16 12..92 15.93 16.25 18.56 20.02 Example 4 13.79 19.59 25.74 29.16 31.83 33.05 Example 5 6.16 9..92 11.93 13.25 14.2 15.02 Comparative Example 18.61 25.26 30.65 40.48 48.65 55.62

[0047] Table 1

[0048] It can be seen that the stability of the carbon fiber after pretreatment of the present invention is greatly improved compared with the comparative example, and it is not easy to flocculate when placed for a long time.

[0049] Furthermore, carbon fiber paper is made by wet process using the carbon fibers dispersed in Examples 1-5 and the comparative examples. The pretreated carbon fibers are divided into three parts on average, 800 mL of hot water is added to each part, and stirred to mix evenly. After mixing, an appropriate amount of dispersant APAM and 600 mL of cold water are added, and then the three solutions are simultaneously placed in a fiber standard deflaking machine for deflaking for 0.5 hours. After the deflaking is completed, the three solutions are poured into the same paper sheet forming machine for papermaking. After the paper sheet is made, first use filter paper to absorb the surface moisture, then set the pressure of the flat vulcanizer to 1000 kPa, take out the paper sheet and put it into the flat vulcanizer, and dry it under high pressure for 20 minutes. After drying, the final carbon paper is obtained, and then the performance of the carbon paper is tested in turn. Specific tests include:

[0050] 1. Air permeability experimental data: Use an air permeability tester to test the air permeability of carbon fiber. Select five points on the front and back of the carbon paper with different fiber lengths, record the air permeability of the ten points, and use the average value as the air permeability of the carbon fiber paper sample. The experimental data is shown in Table 2:

[0051] Air permeability (kN / m) Example 1 2060 Example 2 1920 Example 3 1890 Example 4 2030 Example 5 2200 Comparative Example 1220

[0052] Table 2

[0053] 2. Resistivity experimental data

[0054] The carbon fiber paper was cut into equal parts into the same samples, and 5 different points were selected on the front and back sides as the detection positions. The resistivity was measured respectively, and the resistivity values ​​of the 10 points were recorded and the average value was calculated. The experimental data are shown in Table 2:

[0055] Resistivity (mΩ·cm) Example 1 59.2 Example 2 67.8 Example 3 60.5 Example 4 54.8 Example 5 52.9 Comparative Example 100.3

[0056] Table 3

[0057] From the data in Table 2 and Table 3, it can be seen that the carbon paper made from the pretreated carbon fiber of the present invention can improve the air permeability of the carbon paper and reduce the resistivity. The air permeability and resistivity are one of the most important properties of the gas diffusion layer. From Table 2 and Table 3, it can be seen that the air permeability and resistivity of the carbon paper prepared from the pretreated carbon fiber in Example 5 are both optimal.

[0058] In summary, the present invention first utilizes the modification of carbon fiber by polydopamine, which can significantly improve the surface energy, wettability and surface roughness of carbon fiber, and then configures an alkali lignin-urea alkali solution system, in which the active groups of alkali lignin are used to further modify the carbon fiber, thereby improving the hydrophilic group of the carbon fiber, thereby increasing the dispersion ability of the carbon fiber in the aqueous phase, reducing the interaction force between carbon fibers, reducing the internal friction between carbon fibers, and achieving uniform dispersion of the carbon fiber. The carbon fiber pretreated by the present invention is used to make carbon paper, which can provide air permeability of carbon paper, reduce resistivity, and improve conductivity.

Claims

1. A method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper, characterized in that: The steps include: Step 1, chop the carbon fiber into 4-8 mm, then add the carbon fiber into 0.5-1.5 mol / L NaOH solution, stir and let stand for 25-30 minutes to remove grease impurities on the surface of the carbon fiber; Step 2, heating the NaOH solution to 60-70° C., then adding 1-5 g / L of polydopamine to the NaOH solution and stirring until the color of the mixed solution turns dark black, and modifying the carbon fiber with polydopamine; Step 3, filtering and drying the modified carbon fiber to obtain polydopamine modified carbon fiber; Step 4: adding alkali lignin and urea to a 0.5-1.5 mol / L NaOH solution to form a dispersion, wherein the concentration of alkali lignin in the dispersion is 1-2wt%, and the concentration of urea is 3-8wt%, and then adding polydopamine-modified carbon fiber to the dispersion to complete the dispersion pretreatment.

2. The method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper according to claim 1, characterized in that: In step 1, the concentration of the sodium hydroxide solution is 1 mol / L.

3. The method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper according to claim 1, characterized in that: In step 2, the NaOH solution is heated to 65°C.

4. The method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper according to claim 1, characterized in that: In step 2, 3 g / L of polydopamine was added to the NaOH solution.

5. The method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper according to claim 1, characterized in that: In step 3, the filtered modified carbon fiber is dried at 60°C.

6. The method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper according to claim 1, characterized in that: In step 4, the concentration of alkali lignin in the dispersion is 1.5 wt %.

7. The method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper according to claim 1, characterized in that: In step 4, the concentration of urea in the dispersion is 5 wt %.

8. The method for preparing carbon fiber slurry for improving the uniformity performance of carbon paper according to claim 1, characterized in that: The length of the carbon fiber is 6 mm.

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