Aramid fiber filter paper, preparation method therefor, and application thereof

Abstract

The present invention specifically relates to a preparation method for aramid fiber filter paper, comprising the following steps: step (1), adding aramid pulp fibers into a dispersion in multiple portions and subjecting same to dispersion treatment to obtain aramid fibers with graded size distribution, wherein the dispersion comprises a dispersant, a strong base and a solvent; step (2), mixing the aramid fibers with graded size distribution with water, and performing high-speed mechanical stirring to obtain a slurry of aramid fibers with graded size distribution; and step (3), processing and forming the slurry of aramid fibers with graded size distribution into shape to obtain aramid fiber filter paper. The present invention also relates to aramid fiber filter paper and an application thereof. The aramid fiber filter paper of the present invention has high filtration accuracy and low filtration resistance, and can be used as a hierarchical composite material.

Description

Aramid fiber filter paper, its preparation method and application Technical Field

[0001] This invention relates to the field of filter paper technology, and in particular to an aramid fiber filter paper, its preparation method, and its application. Background Technology

[0002] Currently, the water filtration materials for the water loop and auxiliary systems of domestic nuclear power plants mainly use glass fiber as raw material, generally manufactured using a wet molding process. Glass fiber is characterized by uniform fiber distribution, large dust holding capacity, low resistance, and high strength, making it an ideal water filtration material. However, glass fiber filter media contains silicon, which is easily released into the water loop. Considering that aramid fiber does not contain silicon, has high strength, and good radiation resistance, and that dispersed aramid fibers can achieve a finer diameter, aramid fiber can be used to replace glass fiber in the manufacture of nuclear-grade filter media.

[0003] Currently, conventional aramid pulp fibers are mostly micron-sized, resulting in low filtration accuracy after being processed into paper. Aramid membranes with higher filtration accuracy can be prepared using aramid fibers dispersed in DMSO / KOH, but aramid membranes have high resistance during filtration and cannot be further processed into filter cartridges.

[0004] Therefore, how to improve the filtration accuracy of aramid fiber filter paper while reducing filtration resistance has become a challenge for existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide an aramid fiber filter paper, its preparation method, and its application. The prepared aramid fiber filter paper has high filtration accuracy and low filtration resistance, and can be used as a layered composite material.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing aramid fiber filter paper includes the following steps:

[0008] Step (1): Aramid pulp fibers are added to a dispersion solution in multiple batches for dispersion treatment to obtain gradient-sized aramid mixed fibers; the dispersion solution includes a dispersant, a strong alkali and a solvent;

[0009] Step (2): Mix gradient-size aramid blended fibers with water, and obtain gradient-size aramid blended fiber slurry after high-speed mechanical stirring;

[0010] Step (3): The gradient-size aramid mixed fiber slurry is processed and shaped to obtain aramid fiber filter paper.

[0011] In this invention, in step (1), the diameter of the aramid pulp fiber is preferably (0.5-10) μm, and the length of the aramid pulp fiber is preferably (30-300) μm.

[0012] In this invention, in step (1), the aramid pulp fiber is preferably dried before use, and the drying temperature is preferably (120-160)℃, more preferably (130-150)℃; the drying time is preferably (12-36)h, more preferably (24-30)h.

[0013] In this invention, in step (1), the dispersant in the dispersion is preferably one or more of dimethylformamide, dimethyl sulfoxide, and diphenyl sulfone; the mass ratio of aramid pulp fiber to the volume ratio of the dispersant in the dispersion is preferably 2.5g:(100-1500)mL, more preferably 2.5g:(200-1000)mL, and most preferably 2.5g:(250-500)mL;

[0014] The alkali in the dispersion is preferably a strong alkali, more preferably one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide and barium hydroxide; the mass ratio of aramid pulp fiber to alkali in the dispersion is preferably (0.1-25):1, more preferably (1-20):1, and most preferably (5-15):1.

[0015] The solvent in the dispersion is preferably one or more of methanol, ethanol and water; the mass ratio of aramid pulp fiber to the volume ratio of solvent in the dispersion is preferably 2.5 g: (0.1-100) mL, more preferably 2.5 g: (1-50) mL, and most preferably 2.5 g: (10-30) mL.

[0016] In this invention, in step (1), the number of times the aramid pulp fiber is added is preferably (2-5), more preferably (3-4); the dispersion time of the aramid pulp fiber after each addition of the dispersion liquid is preferably (5-150) min, more preferably (10-120) min, and most preferably (30-60) min.

[0017] In this invention, in step (1), the dispersion treatment is preferably carried out under stirring conditions, and the stirring rate is preferably (300-500) rpm, more preferably 400 rpm; after the dispersion treatment is completed, the product of the dispersion treatment is preferably washed and filtered to obtain gradient size aramid mixed fibers.

[0018] In this invention, in step (2), the rotation speed of the high-speed mechanical stirring is preferably (2000-20000) r / min, more preferably (12000-18000) r / min; the high-speed mechanical stirring time is preferably (1-30) min, more preferably (5-25) min.

[0019] In this invention, the mass ratio of aramid pulp fiber in step (1) to water in step (2) is preferably 1:(90-110), more preferably 1:100.

[0020] The present invention also provides an aramid fiber filter paper, which is prepared according to the above method and is composed of aramid fibers with different diameter distributions.

[0021] The present invention also provides an application of aramid fiber filter paper as a layered composite material.

[0022] Beneficial technical effects of the present invention:

[0023] The aramid fiber filter paper of this invention, its preparation method, and its application involve first adding aramid pulp fibers to a dispersion solution multiple times and stirring. By controlling process parameters such as the composition of the dispersion solution, the number of additions, and the amount added, the aramid pulp fibers can be dispersed for different times, resulting in a gradient structure of aramid mixed fibers with different diameter distributions. During subsequent processing and molding, the gradient-sized aramid mixed fibers randomly overlap and interweave to form a loose porous structure, which can provide excellent filtration accuracy while reducing filtration resistance. Experiments show that the aramid fiber filter paper of this invention has a filtration efficiency of 99.98% for 0.45μm particles, with a clean pressure difference of (15-25) kPa. Attached Figure Description

[0024] Figure 1 is an electron microscope image of the overall aramid fiber filter paper prepared by the preparation method of Example 1;

[0025] Figure 2 is a micron-detail electron microscope image of the aramid fiber filter paper prepared by the preparation method of Example 1;

[0026] Figure 3 is an electron microscope image with dimensioned nanofibers of the aramid fiber filter paper prepared by the preparation method of Example 1;

[0027] Figure 4 is an electron microscope image of the interwoven region of microfibers and nanofibers in the aramid fiber filter paper prepared by the preparation method of Example 1.

[0028] Figure 5 is an electron microscope image of the overall aramid fiber filter paper prepared by the preparation method of Example 2;

[0029] Figure 6 is an electron microscope image of the micron-details of the aramid fiber filter paper prepared by the preparation method of Example 2;

[0030] Figure 7 is an electron microscope image of the aramid fiber filter paper nanofibers prepared by the preparation method in Example 2;

[0031] Figure 8 is an electron microscope image of the interwoven region of microfibers and nanofibers in the aramid fiber filter paper prepared by the preparation method of Example 2.

[0032] Figure 9 is an electron microscope image of the overall aramid fiber filter paper prepared by the preparation method of Example 3;

[0033] Figure 10 is a micron-detail electron microscope image of the aramid fiber filter paper prepared by the preparation method of Example 3;

[0034] Figure 11 is an electron microscope image with dimensioned nanofibers of the aramid fiber filter paper prepared by the preparation method of Example 3;

[0035] Figure 12 is an electron microscope image of the interwoven region of microfibers and nanofibers in the aramid fiber filter paper prepared by the preparation method of Example 3. Detailed Implementation

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “equivalent to”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0037] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] This invention provides a method for preparing aramid fiber filter paper, comprising the following steps:

[0039] Step (1): Aramid pulp fibers are added to a dispersion solution in multiple batches for dispersion treatment to obtain gradient-sized aramid mixed fibers; the dispersion solution includes a dispersant, an alkali, and a solvent;

[0040] Step (2): Mix gradient-size aramid blended fibers with water, and obtain gradient-size aramid blended fiber slurry after high-speed mechanical stirring;

[0041] Step (3): The gradient-size aramid mixed fiber slurry is processed and shaped to obtain aramid fiber filter paper.

[0042] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials for preparing aramid fiber filter paper, and commercially available products well known to those skilled in the art can be used.

[0043] In this invention, in step (1), the diameter of the aramid pulp fiber is preferably (0.5-10) μm, and the length of the aramid pulp fiber is preferably (30-300) μm. This invention does not have a specific limitation on the source of the aramid pulp fiber; commercially available products with diameters and lengths within the above ranges, well-known to those skilled in the art, can be used.

[0044] In this invention, in step (1), the aramid pulp fiber is preferably aramid pulp fiber produced by DuPont.

[0045] In this invention, in step (1), the aramid pulp fiber is preferably dried before use; the drying temperature is preferably (120-160)℃, more preferably (130-150)℃; the drying time is preferably (12-36)h, more preferably (24-30)h. In this invention, drying can remove moisture from the aramid pulp fiber, avoiding any impact on weighing.

[0046] In this invention, in step (1), the dispersant in the dispersion is preferably one or more of dimethylformamide, dimethyl sulfoxide, and diphenyl sulfone.

[0047] In this invention, during the dispersion treatment of aramid pulp fibers, hydrogen in the amide groups of aramid fibers is stripped to generate negatively charged polyanions. In the initial stage of the deprotonation process, the negative charge gradually accumulates on the aramid fiber molecular chains, and the resulting electrostatic repulsion force gradually splits the macroscopic aramid pulp fibers into PPTA microfiber bundles with an average size of (1-2) μm. As the degree of deprotonation increases, the electrostatic repulsion between polymer chains also gradually increases, providing the energy required to break the intermolecular hydrogen bonds between polymer chains, and finally obtaining aramid fibers with a high aspect ratio. The aramid fibers can be stably dispersed in the dispersant under the balance of electrostatic repulsion, van der Waals forces and π-π stacking.

[0048] In this invention, in step (1), the alkali in the dispersion is preferably a strong alkali, more preferably one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, and barium hydroxide. In this invention, the alkali acts as a dispersing aid, mainly working together with dimethyl sulfoxide to accelerate the dispersion of aramid fibers and deprotonate the aramid fibers, that is, to rapidly abstract hydrogen from the aramid molecules and form polyanions on the aramid surface.

[0049] In this invention, in step (1), the solvent in the dispersion is preferably one or more of methanol, ethanol, and water. The solvent selected in this invention can help the dispersion to more quickly remove protons from the aramid fibers, accelerate the deprotonation process, and speed up the dispersion rate of the aramid.

[0050] In this invention, in step (1), the preferred mass ratio of aramid pulp fiber to alkali in the dispersion is (0.1–25):1, more preferably (1–20):1, and most preferably (5–15):1. By limiting the mass ratio of aramid pulp fiber to alkali within the above range, this invention can accelerate the dispersion of aramid pulp fiber and shorten the dispersion time.

[0051] In this invention, in step (1), the preferred mass ratio of aramid pulp fiber to the volume ratio of dispersant in the dispersion is 2.5 g:(100-1500) mL, more preferably 2.5 g:(200-1000) mL, and most preferably 2.5 g:(250-500) mL. By limiting the mass ratio of aramid pulp fiber to the volume ratio of dispersant within the above range, this invention enables the aramid pulp fiber to be fully and stably dispersed.

[0052] In this invention, in step (1), the preferred mass ratio of aramid pulp fiber to solvent volume in the dispersion is 2.5 g:(0.1-100) mL, more preferably 2.5 g:(1-50) mL, and most preferably 2.5 g:(10-30) mL. By limiting the mass ratio of aramid pulp fiber to solvent volume within the above range, this invention can improve the dispersion rate of aramid pulp fiber and shorten the dispersion time.

[0053] In this invention, in step (1), the aramid pulp fiber is preferably added 2 to 5 times, more preferably 3 to 4 times. In this invention, the aramid pulp fiber is added to the dispersion multiple times, allowing the aramid pulp fiber to disperse for different times, thereby obtaining aramid mixed fibers with gradient sizes and different diameter distributions. During subsequent processing and molding, the gradient-size aramid mixed fibers are randomly interwoven to form a loose porous structure, which can provide good filtration accuracy while reducing filtration resistance. By limiting the number of times the aramid pulp fiber is added to the above range, this invention can adjust the distribution of aramid fibers in the gradient-size aramid mixed fibers, further improving the filtration accuracy of the aramid fiber filter paper and reducing the filtration resistance of the aramid fiber filter paper.

[0054] In this invention, when the aramid pulp fiber is added three times, the preferred mass ratio of the aramid pulp fiber added each time is (0.1-1):(0.5-2):(0.5-2), more preferably (0.1-0.5):(0.5-1.5):(0.5-1.5), and most preferably 0.5:1:1. By limiting the mass ratio of the aramid pulp fiber added each time to the above range, this invention ensures that the resulting gradient-size aramid mixed fibers have a suitable gradient size distribution, further improving the filtration accuracy of the filter paper and reducing filtration resistance.

[0055] In this invention, in step (1), the dispersion time after each addition of aramid pulp fibers is preferably (5-150) min, more preferably (10-120) min, and most preferably (30-60) min. In this invention, the dispersion treatment is preferably carried out under stirring conditions, and the stirring rate is preferably (300-500) rpm, more preferably 400 rpm. By limiting the dispersion time and stirring rate after each addition of aramid pulp fibers to the above ranges, this invention enables the dispersed aramid fibers to maintain their fiber morphology and have suitable diameter and length, further improving the filtration accuracy of the filter paper and reducing filtration resistance.

[0056] In this invention, after the dispersion treatment is completed in step (1), the product of the dispersion treatment is preferably washed and then filtered to obtain gradient-size aramid blended fibers. This invention does not impose any special limitations on the washing and filtering operations; washing and filtering operations well known to those skilled in the art can be used.

[0057] In this invention, in step (2), the rotational speed of the high-speed mechanical stirring is preferably (2000-20000) r / min, more preferably (12000-18000) r / min; the duration of the high-speed mechanical stirring is preferably (1-30) min, more preferably (5-25) min. By limiting the rotational speed and duration of the high-speed mechanical stirring within the above ranges, this invention enables more thorough dispersion of gradient-sized aramid blended fibers.

[0058] In this invention, the mass ratio of aramid pulp fiber in step (1) to water in step (2) is preferably 1:(90-110), more preferably 1:100. By limiting the mass ratio of aramid pulp fiber in step (1) to water in step (2) within the above range, this invention enables the dispersed gradient-size aramid mixed fibers to be more fully dispersed in water, which is beneficial for subsequent gradient-size aramid mixed fiber pulp processing and molding.

[0059] This invention does not impose any special limitations on the processing and molding of gradient-size aramid mixed fiber slurry; any filter paper processing and molding process well-known to those skilled in the art can be used. In this invention, the preferred processing and molding method in step (3) is as follows: the gradient-size aramid mixed fiber slurry is sequentially subjected to papermaking, primary hot pressing, sizing, secondary hot pressing, and cooling to obtain aramid fiber filter paper.

[0060] The present invention does not impose any special limitations on the papermaking operation; any papermaking operation known to those skilled in the art can be used.

[0061] In this invention, the preferred temperature for hot pressing the gradient-size aramid mixed fiber slurry is (80-90)℃, more preferably 85℃; the preferred time for hot pressing the gradient-size aramid mixed fiber slurry is (20-40) min, more preferably 30 min; the preferred pressure for hot pressing the gradient-size aramid mixed fiber slurry is (1-5) kPa, more preferably (2-4) kPa; preferably, hot pressing the gradient-size aramid mixed fiber slurry once dries the paper and makes the paper surface smooth.

[0062] In this invention, the adhesive solution used for sizing is preferably one or more of polyamide epichlorohydrin, polyacrylamide, and polyurethane.

[0063] In this invention, the amount of sizing is preferably (1-3)% of the paper mass after one hot pressing, more preferably 2% of the paper mass after one hot pressing. In this invention, sizing provides stiffness and hardness to the paper, improving its durability. By limiting the amount of sizing within the above range, this invention enables the paper to have good stiffness and hardness without adversely affecting its filtration performance.

[0064] In this invention, the preferred temperature for the secondary hot pressing is (80-90)℃, more preferably 85℃; the preferred time for the secondary hot pressing is (20-40) min, more preferably 30 min; and the preferred pressure for the secondary hot pressing is (1-5) kPa, more preferably (2-4) kPa. In this invention, the secondary hot pressing is used to dry the paper and smooth its surface.

[0065] This invention first involves adding aramid pulp fibers to a dispersion solution multiple times and stirring them. By controlling process parameters such as the composition of the dispersion solution, the number of additions, and the amount added, the aramid pulp fibers can be dispersed for different times and to different diameters, thereby obtaining aramid mixed fibers with a gradient structure and different diameter distributions. In the subsequent processing and molding process, the gradient-sized aramid mixed fibers randomly overlap and interweave together to form a loose porous structure, which can provide good filtration accuracy while reducing filtration resistance.

[0066] The present invention also provides an aramid fiber filter paper, which is prepared according to the above preparation method and is composed of aramid fibers with different diameter distributions.

[0067] In this invention, each square meter of aramid fiber filter paper preferably consists of 70g of aramid fibers with a diameter of (10-10000)nm. The volume percentage of aramid fibers with a diameter of (10-100)nm, aramid fibers with a diameter greater than 100nm and less than 500nm, aramid fibers with a diameter of (500-1000)nm, and aramid fibers with a diameter greater than 1μm and less than or equal to 10μm is preferably (10-20)%: (30-40)%: (30-40)%: (10-20)%.

[0068] The aramid fiber filter paper provided by this invention has high filtration accuracy, low filtration resistance, and high strength.

[0069] This invention also provides the application of the aforementioned aramid fiber filter paper as a layered composite material in filtration. The operation of applying the aramid fiber filter paper as a layered composite material in filtration is not particularly limited by this invention; any operation familiar to those skilled in the art for the application of filter paper in filtration can be used.

[0070] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0071] Example 1

[0072] This embodiment provides a method for preparing aramid fiber filter paper, including the following steps:

[0073] Step (1): Aramid pulp fibers are added to the dispersion solution in three batches for dispersion treatment to obtain gradient size aramid mixed fibers; the dispersion solution includes a dispersant, an alkali and a solvent;

[0074] Step (2): Mix gradient-size aramid blended fibers with water, and obtain gradient-size aramid blended fiber slurry after high-speed mechanical stirring;

[0075] Step (3): The gradient-size aramid mixed fiber slurry is processed and shaped to obtain aramid fiber filter paper.

[0076] In this embodiment, in step (1), the aramid pulp fiber is an aramid pulp fiber with a diameter of (0.5-10) μm and a length of (30-300) μm produced by DuPont;

[0077] The dispersion consisted of 0.5 g potassium hydroxide, 10 mL ethanol, 10 mL deionized water and 250 mL dimethyl sulfoxide. The mass ratio of aramid pulp fiber to potassium hydroxide was 5:1, the mass ratio of aramid pulp fiber to the volume ratio of dimethyl sulfoxide was 2.5 g: 250 mL, and the mass ratio of aramid pulp fiber to the total volume ratio of ethanol and deionized water was 2.5 g: 20 mL.

[0078] Aramid pulp fibers were dried at 150°C for 24 hours before being added to the dispersion solution for dispersion treatment;

[0079] Aramid pulp fiber was added to a dispersion solution in three separate steps to obtain the dispersed product. The first step involved adding 0.5 g of aramid pulp fiber to the dispersion solution and stirring at 400 rpm for 30 min. The second step involved adding 1 g of aramid pulp fiber to the dispersion solution and stirring at 400 rpm for 30 min. The third step involved adding 1 g of aramid pulp fiber to the dispersion solution and stirring at 400 rpm for 5 min.

[0080] The product from the dispersion treatment was washed and filtered three times with deionized water to obtain gradient-sized aramid blended fibers.

[0081] In this embodiment, in step (2), gradient-size aramid mixed fibers are mixed with 250g of deionized water and stirred at 15000r / min for 20min to obtain gradient-size mixed fiber slurry.

[0082] In this embodiment, in step (3), the gradient-size aramid mixed fiber slurry is used to make filter paper with a diameter of 21.5 cm using a papermaking machine. It is then hot-pressed at 85°C and 3 kPa for 30 min, and 2% of the paper mass of polyamide epichlorohydrin is added. It is then hot-pressed again at 85°C and 3 kPa for 30 min, and cooled to obtain aramid fiber filter paper.

[0083] The aramid fiber filter paper prepared by the method of this embodiment is composed of aramid fibers with different diameter distributions. The volume percentages of aramid fibers with diameters of (10-100) nm, aramid fibers with diameters greater than 100 nm and less than 500 nm, aramid fibers with diameters of (500-1000) nm, and aramid fibers with diameters of (1-10) μm are 10%:30%:40%:20%.

[0084] Example 2

[0085] The rest is the same as in Example 1, except that in step (1), the stirring time after the first addition of aramid pulp fiber to the dispersion is 60 min; and the stirring time after the second addition of aramid pulp fiber to the dispersion is 60 min.

[0086] The aramid fiber filter paper prepared by the method of this embodiment is composed of aramid fibers with different diameter distributions. The volume percentages of aramid fibers with diameters of (10-100) nm, aramid fibers with diameters greater than 100 nm and less than 500 nm, aramid fibers with diameters of (500-1000) nm, and aramid fibers with diameters of (1-10) μm are 15%:35%:35%:15%.

[0087] Example 3

[0088] The rest is the same as in Example 1, except that in step (1), the stirring time after the first addition of aramid pulp fiber to the dispersion is 150 min; and the stirring time after the second addition of aramid pulp fiber to the dispersion is 15 min.

[0089] The aramid fiber filter paper prepared by the method of this embodiment is composed of aramid fibers with different diameter distributions. The volume percentages of aramid fibers with diameters of (10-100) nm, aramid fibers with diameters greater than 100 nm and less than 500 nm, aramid fibers with diameters of (500-1000) nm, and aramid fibers with diameters of (1-10) μm are 20%:40%:30%:10%.

[0090] The aramid fiber filter paper prepared in Example 2 was observed using a scanning electron microscope. The SEM images obtained at different magnifications are shown in Figures 5 to 8, where Figure 5 is magnified 100 times, Figure 6 is magnified 500 times, Figure 7 is magnified 30,000 times, and Figure 8 is magnified 10,000 times.

[0091] The aramid fiber filter paper prepared in Example 3 was observed using a scanning electron microscope. The SEM images obtained at different magnifications are shown in Figures 9 to 12, where Figure 9 is magnified 50 times, Figure 10 is magnified 3000 times, Figure 11 is magnified 4950 times, and Figure 12 is magnified 100 times.

[0092] As can be seen from Figures 1-12, the aramid fiber filter paper prepared in Examples 1-3 has a porous structure, and the aramid fibers have different diameters.

[0093] The filtration efficiency, clean pressure difference, and dirt holding capacity of the aramid fiber filter paper prepared in Examples 1-3 for particles of different sizes were tested, and the results are shown in Table 1.

[0094] Table 1. Filtration efficiency, clean pressure differential, and dirt holding capacity of the aramid fiber filter paper prepared in Examples 1-3 for particles of different sizes.

[0095] As can be seen from Table 1, the aramid fiber filter papers prepared in Examples 1-3 all exhibit high filtration efficiency for particles with a diameter of 0.45 μm and low filtration resistance. The aramid fiber filter papers provided in Examples 1-3 demonstrate high filtration accuracy, low filtration resistance, and high strength.

[0096] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing aramid fiber filter paper, characterized in that, Includes the following steps: Step (1): Aramid pulp fibers are added to a dispersion solution in multiple batches for dispersion treatment to obtain gradient-sized aramid mixed fibers; the dispersion solution includes a dispersant, a strong alkali and a solvent; Step (2): Mix gradient-size aramid blended fibers with water, and obtain gradient-size aramid blended fiber slurry after high-speed mechanical stirring; Step (3): The gradient-size aramid mixed fiber slurry is processed and shaped to obtain aramid fiber filter paper.

2. The method for preparing aramid fiber filter paper according to claim 1, characterized in that, In step (1), the diameter of the aramid pulp fiber is (0.5-10) μm and the length of the aramid pulp fiber is (30-300) μm.

3. The method for preparing aramid fiber filter paper according to claim 1, characterized in that, In step (1), the aramid pulp fiber is dried before use at a temperature of (120-160)℃ for a time of (12-36)h.

4. The method for preparing aramid fiber filter paper according to claim 1, characterized in that, In step (1), the dispersant in the dispersion is one or more of dimethylformamide, dimethyl sulfoxide and diphenyl sulfone; the mass ratio of aramid pulp fiber to the volume ratio of dispersant in the dispersion is 2.5 g: (100-1500) mL. The alkali in the dispersion is a strong alkali; the mass ratio of aramid pulp fiber to the alkali in the dispersion is (0.1~25):1; The solvent in the dispersion is one or more of methanol, ethanol and water; the mass ratio of aramid pulp fiber to the volume ratio of solvent in the dispersion is 2.5 g: (0.1~100) mL.

5. The method for preparing aramid fiber filter paper according to claim 1, characterized in that, In step (1), the aramid pulp fiber is added 2 to 5 times; the dispersion time of the aramid pulp fiber after each addition of the dispersion liquid is 5 to 150 min.

6. The method for preparing aramid fiber filter paper according to claim 1, characterized in that, In step (1), the dispersion treatment is carried out under stirring conditions at a stirring rate of (300-500) rpm. After the dispersion treatment is completed, the product of the dispersion treatment is washed and filtered to obtain gradient size aramid mixed fibers.

7. The method for preparing aramid fiber filter paper according to claim 1, characterized in that, In step (2), the speed of the high-speed mechanical stirring is (2000~20000) r / min, and the time of high-speed mechanical stirring is (1~30) min.

8. The method for preparing aramid fiber filter paper according to claim 1, characterized in that, The mass ratio of aramid pulp fiber in step (1) to water in step (2) is 1:(90-110).

9. An aramid fiber filter paper, characterized in that, The aramid fiber filter paper is prepared by the method according to any one of claims 1-8, and is composed of aramid fibers with different diameter distributions.

10. The application of the aramid fiber filter paper according to claim 9, characterized in that, Used as a layered composite material.

Images