Aramid fiber filter paper as well as preparation method and application thereof

Abstract

The invention particularly relates to a preparation method of aramid fiber filter paper, which comprises the following steps: step (1), aramid pulp fibers are added into a dispersion liquid for multiple times for dispersion treatment to obtain gradient-size aramid mixed fibers, and the dispersion liquid comprises a dispersing agent, strong base and a solvent; (2) mixing the gradient-size aramid fiber mixed fiber with water, and mechanically stirring at a high speed to obtain gradient-size aramid fiber mixed fiber slurry; and (3) processing and forming the gradient-size aramid fiber mixed fiber slurry to obtain the aramid fiber filter paper. The invention further relates to aramid fiber filter paper and application thereof. The aramid fiber filter paper disclosed by the invention is high in filter precision and low in filter resistance, and can be used as a hierarchical composite material.

Description

Technical Field

[0001] The invention relates to the technical field of filter paper, in particular to an aramid fiber filter paper and a preparation method and application thereof. Background Art

[0002] At present, the water filter materials of the water circuit and auxiliary system of domestic nuclear power plants are mainly made of glass fiber as raw material, which is generally made by wet molding process. It has the characteristics of uniform fiber distribution, large dust holding capacity, small resistance, and high strength. It is an ideal water filter material. However, glass fiber filter material contains silicon, which is easy to precipitate in the water circuit. Considering that aramid fiber does not contain silicon, has high strength, and has good radiation resistance, the dispersed aramid fiber can reach a finer diameter. Therefore, aramid fiber can be used to replace glass fiber to manufacture nuclear grade filter material.

[0003] Currently, most conventional aramid pulp fibers are microns in size, and have low filtration accuracy after being made into paper. Aramid fibers dispersed in DMSO / KOH can be used to prepare aramid membranes with higher filtration accuracy, but aramid membranes have high resistance during filtration and cannot be further made into filter elements for use.

[0004] Therefore, how to improve the filtration accuracy of aramid fiber filter paper while reducing the filtration resistance has become a difficult problem in the prior art. Summary of the invention

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

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

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

[0008] Step (1), adding aramid pulp fibers into a dispersion liquid for dispersion treatment in multiple times to obtain gradient-sized aramid mixed fibers; the dispersion liquid includes a dispersant, a strong base and a solvent;

[0009] Step (2), mixing the gradient-sized aramid mixed fibers with water, and obtaining a gradient-sized aramid mixed fiber slurry after high-speed mechanical stirring;

[0010] Step (3), processing and molding the gradient-sized aramid mixed fiber slurry to obtain aramid fiber filter paper.

[0011] In the present 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 the present invention, in step (1), the aramid pulp fiber is preferably dried before use, and the drying temperature is preferably (120-160)°C, more preferably (130-150)°C; the drying time is preferably (12-36)h, more preferably (24-30)h.

[0013] In the present invention, in step (1), the dispersant in the dispersion is preferably one or more of dimethylformamide, dimethyl sulfoxide and diphenyl sulfone; the volume ratio of the mass of the aramid pulp fiber to the dispersant in the dispersion is preferably 2.5 g: (100-1500) mL, more preferably 2.5 g: (200-1000) mL, and most preferably 2.5 g: (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 the aramid pulp fiber to the 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 volume ratio of the mass of aramid pulp fiber to the solvent in the dispersion is preferably 2.5g:(0.1-100)mL, more preferably 2.5g:(1-50)mL, and most preferably 2.5g:(10-30)mL.

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

[0017] In the present 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-sized aramid mixed fibers.

[0018] In the present 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 time of the high-speed mechanical stirring is preferably (1-30) min, more preferably (5-25) min.

[0019] In the present invention, the mass ratio of the aramid pulp fiber in step (1) to the 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 consists of aramid fibers with different diameter distributions.

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

[0022] Beneficial technical effects of the present invention:

[0023] The aramid fiber filter paper and its preparation method and application of the present invention first add aramid pulp fiber to the dispersion liquid for several times and stir, control the composition of the dispersion liquid, the number of times of adding and the amount of adding and other process parameters, so that the aramid pulp fiber can be dispersed for different times, thereby obtaining gradient structure aramid mixed fibers with different diameter distributions, and in the subsequent processing and forming process, the gradient size aramid mixed fibers are randomly overlapped and interwoven to form a loose porous structure, which can provide good filtering accuracy and reduce filtering resistance. Experiments show that the aramid fiber filter paper of the present invention has a filtering efficiency of 99.98% for 0.45μm particles, and a clean pressure difference of (15-25) kPa. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0027] Figure 4 This is an electron microscope image of the interwoven area of ​​micron fibers and nano fibers of the aramid fiber filter paper prepared by the preparation method of Example 1;

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

[0029] Figure 6 This is a micron detail electron microscope image of the aramid fiber filter paper prepared by the preparation method of Example 2;

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

[0031] Figure 8 This is an electron microscope image of the interwoven area of ​​micron fibers and nano fibers of the aramid fiber filter paper prepared by the preparation method of Example 2.

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

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

[0034] Fig.11 This is an electron microscope image of the aramid fiber filter paper nanofibers prepared by the preparation method of Example 3 with dimension marking;

[0035] Fig.12 This is an electron microscope image of the interwoven area of ​​micron fibers and nano fibers of the aramid fiber filter paper prepared by the preparation method of Example 3. DETAILED DESCRIPTION

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0037] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

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

[0039] Step (1), adding aramid pulp fibers into a dispersion liquid for dispersion treatment in multiple times to obtain gradient-sized aramid mixed fibers; the dispersion liquid includes a dispersant, an alkali and a solvent;

[0040] Step (2), mixing the gradient-sized aramid mixed fibers with water, and obtaining a gradient-sized aramid mixed fiber slurry after high-speed mechanical stirring;

[0041] Step (3), processing and molding the gradient-sized aramid mixed fiber slurry to obtain aramid fiber filter paper.

[0042] Unless otherwise specified, the present invention has no particular limitation on the sources of the raw materials for preparing the aramid fiber filter paper, and commercially available products known to those skilled in the art may be used.

[0043] In the present 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. The present invention has no particular limitation on the source of the aramid pulp fiber, and commercial products with diameters and lengths within the above ranges known to those skilled in the art can be used.

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

[0045] In the present invention, in step (1), the aramid pulp fiber is preferably dried before use; the drying temperature is preferably (120-160)°C, more preferably (130-150)°C; the drying time is preferably (12-36)h, more preferably (24-30)h. In the present invention, drying can remove moisture from the aramid pulp fiber to avoid affecting the weighing.

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

[0047] In the present invention, during the dispersion treatment of aramid pulp fibers, hydrogen in the amide groups of the aramid fibers is captured to generate negatively charged polyanions. In the initial stage of the deprotonation process, negative charges gradually accumulate on the aramid fiber molecular chains, and the generated electrostatic repulsion gradually splits the macroscopic aramid pulp fibers into PPTA microfiber bundles with an average size of (1 to 2) μm. As the degree of deprotonation increases, the electrostatic repulsion between polymer chains also gradually increases, providing the energy required to destroy the intermolecular hydrogen bonds between the polymer chains, and finally obtaining high aspect ratio aramid fibers. 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 the present invention, in step (1), the base in the dispersion is preferably a strong base, more preferably one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide and barium hydroxide. In the present invention, the base acts as a dispersing aid mainly together with dimethyl sulfoxide to accelerate the dispersion of aramid and deprotonate the aramid, that is, quickly capture hydrogen from the aramid molecules to form polyanions on the surface of the aramid.

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

[0050] In the present invention, in step (1), 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. The present invention limits the mass ratio of aramid pulp fiber to alkali within the above range, which can accelerate the dispersion of aramid pulp fiber and shorten the dispersion time.

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

[0052] In the present invention, in step (1), the volume ratio of the mass of the aramid pulp fiber to the 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. The present invention limits the volume ratio of the mass of the aramid pulp fiber to the solvent within the above range, which can increase the dispersion speed of the aramid pulp fiber and shorten the dispersion time.

[0053] In the present invention, in step (1), the number of times the aramid pulp fiber is added is preferably (2 to 5) times, and more preferably (3 to 4) times. In the present invention, the aramid pulp fiber is added to the dispersion liquid in multiple times, so that the aramid pulp fiber can be dispersed for different times, thereby obtaining gradient-sized aramid mixed fibers with different diameter distributions. In the subsequent processing and molding process, the gradient-sized aramid mixed fibers are randomly connected and interwoven together to form a loose porous structure, which can provide good filtration accuracy and reduce filtration resistance. The present invention limits the number of times the aramid pulp fiber is added to the above range, which can adjust the distribution of aramid fibers in the gradient-sized aramid mixed fibers, further improve the filtration accuracy of the aramid fiber filter paper, and reduce the filtration resistance of the aramid fiber filter paper.

[0054] In the present invention, when the aramid pulp fiber is added three times, the mass ratio of the aramid pulp fiber added each time is preferably (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. The present invention limits the mass ratio of the aramid pulp fiber added each time within the above range, so that the gradient-sized aramid mixed fiber obtained after dispersion has a suitable gradient size distribution, further improving the filtration accuracy of the filter paper and reducing the filtration resistance.

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

[0056] In the present invention, in step (1), after the dispersion treatment is completed, the product of the dispersion treatment is preferably washed and then filtered to obtain a gradient size aramid mixed fiber. The present invention has no special limitation on the washing and filtering operations, and the washing and filtering operations well known to those skilled in the art can be used.

[0057] In the present invention, in step (2), the speed of high-speed mechanical stirring is preferably (2000-20000) r / min, more preferably (12000-18000) r / min; the time of high-speed mechanical stirring is preferably (1-30) min, more preferably (5-25) min. The present invention limits the speed and time of high-speed mechanical stirring to the above range, which can make the gradient-sized aramid mixed fibers dispersed more fully.

[0058] In the present invention, the mass ratio of the aramid pulp fiber in step (1) to the water in step (2) is preferably 1: (90-110), and more preferably 1: 100. The present invention limits the mass ratio of the aramid pulp fiber in step (1) to the water in step (2) within the above range, so that the dispersed gradient-sized aramid mixed fibers can be more fully dispersed in water, which is beneficial to the subsequent processing and molding of the gradient-sized aramid mixed fiber slurry.

[0059] The present invention has no special limitation on the operation of processing and forming the gradient-sized aramid mixed fiber slurry, and the filter paper processing and forming process well known to those skilled in the art can be adopted. In the present invention, the processing and forming method in step (3) is preferably: the gradient-sized aramid mixed fiber slurry is subjected to papermaking, primary hot pressing, sizing, secondary hot pressing and cooling in sequence to obtain aramid fiber filter paper.

[0060] The present invention has no particular limitation on the papermaking operation, and any papermaking operation well known to those skilled in the art may be used.

[0061] In the present invention, the temperature for hot pressing the gradient-sized aramid mixed fiber slurry is preferably (80-90)°C, more preferably 85°C; the time for hot pressing the gradient-sized aramid mixed fiber slurry is preferably (20-40) min, more preferably 30 min; the pressure for hot pressing the gradient-sized aramid mixed fiber slurry is preferably (1-5) kPa, more preferably (2-4) kPa; preferably, the gradient-sized aramid mixed fiber slurry is hot pressed once to dry the paper and make the surface of the paper smooth.

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

[0063] In the present invention, the amount of sizing is preferably (1-3)% of the mass of the paper after one hot pressing, and more preferably 2% of the mass of the paper after one hot pressing. In the present invention, sizing can provide stiffness and hardness to the paper and improve the durability of the paper. The present invention limits the amount of sizing to the above range, which can make the paper have good stiffness and hardness without adversely affecting its filtering performance.

[0064] In the present invention, the temperature of the secondary hot pressing is preferably (80-90)°C, more preferably 85°C; the time of the secondary hot pressing is preferably (20-40) min, more preferably 30 min; the pressure of the secondary hot pressing is preferably (1-5) kPa, more preferably (2-4) kPa. In the present invention, the secondary hot pressing is used to dry the paper and make the surface of the paper flat.

[0065] The present invention first adds aramid pulp fibers into a dispersion liquid for multiple times and stirs them, and controls process parameters such as the composition of the dispersion liquid, the number of times of adding in batches and the amount of adding in batches, so that the aramid pulp fibers can be dispersed for different times and dispersed to different diameters, thereby obtaining gradient structure aramid mixed fibers with different diameter distributions. In the subsequent processing and molding process, the gradient size aramid mixed fibers are randomly overlapped and interwoven to form a loose porous structure, which can provide good filtration accuracy and reduce filtration resistance.

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

[0067] In the present invention, each square meter of aramid fiber filter paper is preferably composed of 70g of aramid fibers with a diameter of (10-10000)nm, wherein the volume percentages 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 are preferably (10-20)%: (30-40)%: (30-40)%: (10-20)%.

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

[0069] The present invention also provides the use of the aramid fiber filter paper as a layered composite material in filtration. The present invention has no special restrictions on the operation of using the aramid fiber filter paper as a layered composite material in filtration, and the operation of using filter paper in filtration well known to those skilled in the art can be used.

[0070] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0071] Example 1

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

[0073] Step (1), adding aramid pulp fibers into a dispersion liquid for dispersion treatment three times to obtain gradient-sized aramid mixed fibers; the dispersion liquid comprises a dispersant, an alkali and a solvent;

[0074] Step (2), mixing the gradient-sized aramid mixed fibers with water, and obtaining a gradient-sized aramid mixed fiber slurry after high-speed mechanical stirring;

[0075] Step (3), processing and molding the gradient-sized aramid mixed fiber slurry to obtain aramid fiber filter paper.

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

[0077] The dispersion consists 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 is 5:1, the volume ratio of aramid pulp fiber to dimethyl sulfoxide is 2.5 g:250 mL, and the total volume ratio of aramid pulp fiber to ethanol and deionized water is 2.5 g:20 mL.

[0078] The aramid pulp fiber was dried at 150°C for 24 h before being added to the dispersion solution for dispersion treatment;

[0079] Aramid pulp fiber was added to the dispersion liquid for dispersion treatment three times to obtain a dispersion product; 0.5 g of aramid pulp fiber was added to the dispersion liquid for the first time, and then stirred with a stirring paddle at 400 rpm for 30 minutes; 1 g of aramid pulp fiber was added to the dispersion liquid for the second time, and then stirred with a stirring paddle at 400 rpm for 30 minutes; 1 g of aramid pulp fiber was added to the dispersion liquid for the third time, and then stirred with a stirring paddle at 400 rpm for 5 minutes;

[0080] The dispersed product was washed and filtered three times with deionized water to obtain gradient-sized aramid mixed fibers.

[0081] In this embodiment, in step (2), the gradient-sized aramid mixed fibers are mixed with 250 g of deionized water and stirred at 15,000 r / min for 20 min to obtain a gradient-sized mixed fiber slurry.

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

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

[0084] Example 2

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

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

[0087] Example 3

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

[0089] The aramid fiber filter paper prepared by the preparation method of this embodiment is composed of aramid fibers with different diameter distributions, and the volume percentages of aramid fibers with a diameter of (10-100) nm, aramid fibers with a diameter greater than 100 nm and less than 500 nm, aramid fibers with a diameter of (500-1000) nm and aramid fibers with a diameter 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, and the SEM images obtained at different magnifications were as follows: Figures 5 to 8 As shown, Figure 5 To magnify 100 times, Figure 6 To magnify 500 times, Figure 7 To magnify 30,000 times, Figure 8 Magnified 10,000 times.

[0091] The aramid fiber filter paper prepared in Example 3 was observed using a scanning electron microscope, and the SEM images obtained at different magnifications were as follows: Figures 9 to 12 As shown, Fig. 9 To magnify 50 times, Fig.10 To magnify 3000 times, Fig.11 To magnify 4950 times, Fig.12 Magnified 100 times.

[0092] from Figures 1 to 12 It can be seen that 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 papers prepared in Examples 1 to 3 for particles of different particle sizes were tested. The results are shown in Table 1.

[0094] Table 1 Filtration efficiency, clean pressure difference and dirt holding capacity of aramid fiber filter paper prepared in Examples 1 to 3 for particles of different particle sizes

[0095]

[0096] It can be seen from Table 1 that the aramid fiber filter papers prepared in Examples 1-3 have a high filtration effect on particles with a diameter of 0.45 μm and a low filtration resistance. The aramid fiber filter papers provided in Examples 1-3 have high filtration accuracy, low filtration resistance and high strength.

[0097] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing aramid fiber filter paper, characterized in that: The steps include: Step (1), adding aramid pulp fibers into a dispersion liquid for dispersion treatment in multiple times to obtain gradient-sized aramid mixed fibers; the dispersion liquid includes a dispersant, a strong base and a solvent; Step (2), mixing the gradient-sized aramid mixed fibers with water, and obtaining a gradient-sized aramid mixed fiber slurry after high-speed mechanical stirring; Step (3), processing and molding the gradient-sized aramid mixed fiber slurry 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, the drying temperature is (120-160)°C, and the drying time is (12-36) hours.

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 volume ratio of the mass of the aramid pulp fiber to the dispersant in the dispersion is 2.5g: (100-1500)mL; The alkali in the dispersion is a strong alkali; the mass ratio of the 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 volume ratio of the mass of the aramid pulp fiber to the solvent in the dispersion is 2.5g: (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; and the dispersion time of the aramid pulp fiber after each addition of the dispersion liquid is 5 to 150 minutes.

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-sized aramid mixed fibers.

7. The method for preparing aramid fiber filter paper according to claim 1, characterized in that: In step (2), the rotation speed of the high-speed mechanical stirring is (2000-20000) r / min, and the time of the 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 the aramid pulp fiber in step (1) to the water in step (2) is 1:(90-110).

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

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

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