A highly fine aramid pulp fiber powder and its preparation process

Abstract

The present invention relates to the technical field of high-performance fiber and chemical fiber preparation, and in particular to a highly fibrillated aramid pulp fiber powder and a preparation process thereof. The preparation process comprises the following steps: Step 1: adding dimethyl sulfoxide, alkali solution, and para-aramid fiber to a blender in sequence, and stirring the mixture in a sealed manner to obtain an ultra-high-concentration fibrillated aramid pulp fiber mixed gel solution; Step 2: using water to degrade the ultra-high-concentration fibrillated aramid pulp fiber mixed gel solution to obtain wet aramid pulp fibers; Step 3: spreading the wet aramid pulp fibers into a thin layer to obtain aramid pulp fibers; and Step 4: using tap water to degrade the aramid pulp fibers, followed by filtration, collection, and vacuum drying to obtain highly fibrillated aramid pulp fiber powder. The present invention utilizes the principle of deprotonation using alkali solution / organic solvents, and achieves fibrillation of aramid fibers through relatively gentle hydrogen bond cleavage during the process, thereby increasing the content of fine fibers and achieving a minimum antennae of nanometers.

Description

Technical Field

[0001] This invention relates to the field of high-performance fiber and chemical fiber preparation technology, specifically to a highly fine aramid pulp fiber powder and its preparation process. Background Art

[0002] Aramid fiber, developed by DuPont in the 1960s, possesses excellent properties such as high strength, high modulus, and high temperature resistance, and is widely used in rail transportation, aerospace, and defense industries. Aramid pulp is a differentiated type of aramid fiber, obtained through fibrillation treatment. It exhibits extremely high adhesion and is often used as a reinforcing fiber in sealing and friction applications, making it an excellent reinforcing fiber. Aramid pulp has a light yellow appearance and a flocculent structure, containing abundant fine fibers while being flexible, heat-resistant, corrosion-resistant, and with low shrinkage. It is also an ideal soft reinforcing material. For example, using aramid pulp to reinforce gaskets provides good resilience and sealing properties, is safe and harmless, and can be used as a raw material for preparing sealing media for pipelines containing hydrocarbons and acids / alkalis in chemical plants. When used in friction materials, aramid pulp can serve as a substitute for asbestos fiber, not only reducing friction noise but also adjusting the coefficient of friction and improving friction stability.

[0003] Currently, there are two processes for preparing aramid pulp. One involves cutting, unwinding, and fibrillating aramid fabrics. The advantages of this process are higher crystallinity and strength, and excellent temperature resistance. However, the high strength of aramid fibers makes them difficult to separate and fibrillate, and the process involves high energy consumption and noise. The other process involves fiberizing aramid polymers to prepare aramid pulp, mainly through phase separation and controlled self-polymerization using chemical reagents. The problems with this process are low strength, poor temperature resistance, and difficulty in recovering the chemical reagents. Meanwhile, with the development of the shoe materials, rubber, and paper industries, the market demands aramid pulp fibers that can be mass-produced with a high content of fine fibers to meet the needs of refined and functional products. Furthermore, although there have been breakthrough reports in the nano-sizing of aramid fibers in recent years, there is still no technology for powdering this material, limiting the further application of aramid fibers. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a highly fine aramid pulp fiber powder and its preparation process.

[0005] This invention is achieved through the following technical solution:

[0006] A process for preparing highly fine aramid pulp fiber powder includes the following steps:

[0007] Step 1: Dimethyl sulfoxide, alkaline solution and para-aramid fiber are added sequentially, and then the mixture is sealed and stirred to obtain a mixed gel of ultra-high concentration fibrillated aramid pulp and fiber.

[0008] Step 2: Use water to decompose the ultra-high concentration fibrillated aramid pulp fiber mixed gel, then filter and collect to obtain wet aramid pulp fiber;

[0009] Step 3: Lay the wet aramid pulp fiber into a thin layer, and freeze and dry it to obtain aramid pulp fiber;

[0010] Step 4: Use tap water to loosen the aramid pulp fibers, then filter, collect, and vacuum dry to obtain highly fine aramid pulp fiber powder.

[0011] Preferably, in step 1, the para-aramid fiber is an aramid fiber with a para structure (1414), and the raw material source of the para-aramid fiber is para-aramid spinning, para-cutting, para-aramid fiber fabric or para-aramid fiber scraps.

[0012] Preferably, in step 1, the ratio of alkali solution, dimethyl sulfoxide, and para-aramid fiber is (4-6) mL: (400-500) mL: (5-7.5) g, wherein the alkali solution is a combination or any one of potassium hydroxide, calcium hydroxide, and sodium hydroxide, with a concentration of 0.8 g / mL to 1 g / mL, the stirring reaction time is (20-24) h, and the rotation speed is (300-600) r / min.

[0013] Preferably, in step 2, the ratio of ultra-high concentration fibrillated aramid pulp fiber mixed gel liquid to water is (400-500) mL: (800-1000) mL, wherein during disintegration, the rotation speed is (20000-40000) revolutions, and the filter screen used during filtration is 1800-2800 mesh.

[0014] Preferably, in step 3, the freezing temperature is (-0 to -60)℃, the freezing time is (8 to 12)h, the drying time is (10 to 12)h, and the thin layer thickness is (2 to 3)mm.

[0015] Preferably, in step 4, the ratio of aramid pulp fiber to tap water is 5g:200mL; during dissolution, the rotation speed is (10000~20000) revolutions.

[0016] Preferably, in step 4, the vacuum drying temperature is (60-120)℃ and the time is (5-10) hours.

[0017] An aramid pulp fiber obtained by a preparation process of highly fine aramid pulp fiber.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention discloses a process for preparing highly fine aramid pulp fiber powder, which includes steps such as alkaline fibrillation, pyrolysis solvent washing and separation, freeze drying to maintain morphology, hydrolytic dispersion tearing and crosslinking, and vacuum drying to collect powder. While ensuring that the aramid fiber obtains the finest fiber powder to the greatest extent, the process has the advantages of low energy consumption, no noise, and high efficiency.

[0020] To address the challenges of high energy consumption and difficulty in fine fiberization during conventional mechanical grinding of aramid pulp fibers, this paper utilizes the principle of deprotonation using alkaline solutions / organic solvents. Through a relatively mild hydrogen bond cleavage process, fibrillation of aramid fibers is achieved, increasing the content of fine fibers and reducing the minimum fiber size to the nanometer level.

[0021] An improvement was made to the existing chemical pyrolysis method, which can only obtain aramid nanofiber dispersions. The degree of pyrolysis was controlled by using a weakened alkali ratio, and the fine fiber morphology was maintained by freeze drying. Through hydraulic decomposition and re-tearing, uniform aramid pulp fiber fine fiber powder was prepared. This solved the problem of micro and nano aramid fibers easily forming films and self-adheding due to the scale effect. The fiber relaxation morphology after pyrolysis was preserved, which is more conducive to downstream industry applications.

[0022] The reagents used in the preparation process are all conventional pharmaceutical reagents, which are low in toxicity, inexpensive and readily available. The equipment used is all conventional instruments and equipment, which lays the foundation for the engineering of highly fine aramid pulp and improves the feasibility of the process.

[0023] The powder preparation technology provided by this invention avoids the inconvenience of liquids, reduces transportation costs and requirements, and also facilitates the use of aramid pulp in various industries. It can be directly added as a reinforcing component, avoiding the cumbersome process of downstream manufacturers removing dispersing agents.

[0024] Furthermore, the raw materials are all aramid fiber products with para-structure, which can realize the reuse of aramid scraps and waste, solve the problem of aramid fiber products not decomposing and degrading for a long time, thus harming the environment. At the same time, the universality of the raw materials can improve the market acceptance of aramid pulp fiber products in terms of cost. Attached Figure Description

[0025] Figure 1 This is a simplified process flow diagram of a highly fine aramid pulp fiber powder preparation method according to the present invention.

[0026] Figure 2 MorFi electron microscope image of the aramid pulp fiber prepared in Example 1;

[0027] Figure 3 Transmission electron microscopy image of the aramid pulp fiber tip prepared in Example 1;

[0028] Figure 4 MorFi electron microscope image of the aramid pulp fiber prepared in Example 2;

[0029] Figure 5 Transmission electron microscopy image of the aramid pulp fiber tips prepared in Example 2;

[0030] Figure 6 MorFi electron microscope image of the aramid pulp fiber prepared in Example 3;

[0031] Figure 7 MorFi electron microscope image of the aramid pulp fiber prepared in Example 4;

[0032] Figure 8 This is a MorFi electron microscope image of the aramid pulp fiber prepared in Example 5. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0034] This invention discloses a process for preparing highly fine aramid pulp fiber powder, comprising the following steps:

[0035] Step 1: Dimethyl sulfoxide, alkaline solution and para-aramid fiber are added to a mixer in sequence, and then the mixture is sealed and stirred to obtain a mixed gel of ultra-high concentration fibrillated aramid pulp and fiber.

[0036] Among them, para-aramid fiber is an aramid fiber with a para-structure (1414). The raw materials for para-aramid fiber are para-aramid spinning, para-cut stubs, para-aramid fiber fabrics, or para-aramid fiber scraps.

[0037] The ratio of alkali solution, dimethyl sulfoxide, and para-aramid fiber is (4-6) mL: (400-500) mL: (5-7.5) g, wherein the alkali solution is a combination or any one of potassium hydroxide, calcium hydroxide, and sodium hydroxide, with a concentration of 0.8 g / mL to 1 g / mL, the stirring reaction time is (20-24) h, and the stirring speed is (300-600) r / min.

[0038] Step 2: Use water to decompose the ultra-high concentration fibrillated aramid pulp fiber mixed gel solution, then filter and collect to obtain wet aramid pulp fiber; wherein, the ratio of ultra-high concentration fibrillated aramid pulp fiber mixed gel solution to water is (400~500) mL: (800~1000) mL.

[0039] Step 3: Spread the wet aramid pulp fiber into a thin layer and freeze and dry it to obtain aramid pulp fiber; wherein, during freezing, the temperature is (-0 to -60)℃ and the time is (8 to 12)h, the drying time is (10 to 12)h, and the thickness of the thin layer is (2 to 3)mm. The main purpose is to increase the specific surface area of ​​the freeze-drying. The same technical effect can be achieved by setting a different freezing time according to the thickness.

[0040] Step 4: The aramid pulp fibers are loosened using tap water, then filtered, collected, and vacuum dried to obtain highly fine aramid pulp fiber powder. The ratio of aramid pulp fiber to tap water is 5g:200mL, and the loosening rotation speed is (10000~20000) revolutions. The vacuum drying temperature is (60~120)℃, and the time is (5~10) hours.

[0041] The present invention provides a highly refined aramid pulp fiber powder preparation process that can achieve micronization of more than 79% of aramid pulp fibers, with the fibers containing nano-sized ends, and the resulting finished products are all in powder form. The process is low-noise, low-power, and highly operable, and has good social and economic benefits and application value.

[0042] Example 1

[0043] A highly finely fiberized aramid pulp fiber powder and its preparation method, comprising the following steps.

[0044] Step 1: Prepare an alkaline solution with a concentration of 0.8 g / mL using potassium hydroxide;

[0045] Step 2: Add the alkaline solution, dimethyl sulfoxide, and para-aramid fiber or para-aramid fiber fabric to a mixer in the order of 4 mL: 400 mL: 5 g, and stir at 300 r / min for 20 h to obtain a high-concentration aramid pulp fiber mixed gel solution.

[0046] Step 3: Transfer the obtained high-concentration aramid pulp fiber mixed gel solution to a standard pulp desolventizer, add tap water at a ratio of 400:800, desolvent for 20,000 revolutions to obtain aramid pulp fiber desolvent solution;

[0047] Step 4: Filter the aramid pulp fiber disintegration solution from the previous step through an 1800-mesh filter and collect the wet aramid pulp fiber.

[0048] Step 5: Spread the collected wet aramid pulp fibers into a 2mm thick layer, freeze at -0℃ for 12 hours, freeze-dry for 12 hours to obtain a freeze-dried aramid pulp fiber layer;

[0049] Step 6: Add the freeze-dried aramid pulp fiber thin layer to tap water at a ratio of 5g:200mL and decompose for 10,000 revolutions, then filter and collect it through a 2800-mesh filter.

[0050] Step 7: The obtained aramid pulp fiber is vacuum dried at 60°C for 10 hours to obtain highly fine aramid pulp fiber powder.

[0051] Reference Figure 2 , 3 The product prepared in Example 1 was in powder form. MorFi randomly photographed the fine fibers during the statistical process, showing the size and morphology of the prepared samples. Analysis shows that this example achieved 82.5% miniaturization of aramid pulp fibers, with an average fiber length of approximately 34 μm and a specific surface area of ​​15.6 m². 2 / g features low noise, low power consumption, and high operability in the process.

[0052] Example 2

[0053] A highly finely fiberized aramid pulp fiber powder and its preparation method, comprising the following steps.

[0054] Step 1: Prepare an alkaline solution with a concentration of 0.9 g / mL by mixing 3 g of potassium hydroxide and 3 g of calcium hydroxide;

[0055] Step 2: Add the alkaline solution, dimethyl sulfoxide, and para-aramid fiber or para-aramid fiber fabric to a mixer in the order of 6 mL: 450 mL: 6 g, and stir at 400 r / min for 22 h to obtain a high-concentration aramid pulp fiber mixed gel solution.

[0056] Step 3: Transfer the obtained high-concentration aramid pulp fiber mixed gel solution to a standard pulp desolventizer, add tap water at a ratio of 480mL:900mL, and desolvent for 25,000 revolutions to obtain aramid pulp fiber desolvent solution.

[0057] Step 4: Filter the aramid pulp fiber disintegration solution from the previous step through a 2000-mesh filter and collect the wet aramid pulp fiber;

[0058] Step 5: Spread the collected wet aramid pulp fibers into a 2.5 mm thick layer, freeze at -5℃ for 10 hours, freeze-dry for 11 hours to obtain a freeze-dried aramid pulp fiber layer;

[0059] Step 6: Add the freeze-dried aramid pulp fiber thin layer to tap water at a ratio of 5g:200mL and decompose for 15,000 revolutions, then filter and collect it through a 2800-mesh filter.

[0060] Step 7: Dry the obtained aramid pulp fiber under vacuum at 100℃ for 8 hours to obtain highly fine aramid pulp fiber powder.

[0061] Reference Figure 4 , 5The product prepared by the process in Example 2 is in powder form, achieving 87.4% fineness of aramid pulp fibers, with an average fiber length of approximately 29 μm and a specific surface area of ​​18.2 m². 2 / g features low noise, low power consumption, and high operability in the process.

[0062] Example 3

[0063] A highly finely fiberized aramid pulp fiber powder and its preparation method, comprising the following steps.

[0064] Step 1: Prepare an alkaline solution with a concentration of 1 g / mL using sodium hydroxide;

[0065] Step 2: Add the alkaline solution, dimethyl sulfoxide, and para-aramid fiber or para-aramid fiber fabric to a mixer in the order of 5 mL: 500 mL: 7 g, and stir at 500 r / min for 18 h to obtain a high-concentration aramid pulp fiber mixed gel solution.

[0066] Step 3: Transfer the obtained high-concentration aramid pulp fiber mixed gel solution to a standard pulp desolventizer, add tap water at a ratio of 500mL:1000mL, desolvent for 30,000 revolutions to obtain aramid pulp fiber desolvent solution;

[0067] Step 4: Filter the aramid pulp fiber disintegration solution from the previous step through a 2400-mesh filter and collect the wet aramid pulp fiber;

[0068] Step 5: Spread the collected wet aramid pulp fibers into a 3mm thick layer, freeze at -20℃ for 12 hours, freeze-dry for 12 hours to obtain a freeze-dried aramid pulp fiber layer;

[0069] Step 6: Add the freeze-dried aramid pulp fiber thin layer to tap water at a ratio of 5g:200mL and decompose for 20,000 revolutions. Then filter and collect the solution through a 2800-mesh filter.

[0070] Step 7: Dry the obtained aramid pulp fiber under vacuum at 120°C for 5 hours to obtain highly fine aramid pulp fiber powder.

[0071] Reference Figure 6 The product prepared in Example 3 is in powder form, achieving 81.3% fineness of aramid pulp fibers, with an average fiber length of approximately 30 μm and a specific surface area of ​​17.1 m². 2 / g features low noise, low power consumption, and high operability in the process.

[0072] Example 4

[0073] A highly finely fiberized aramid pulp fiber powder and its preparation method, comprising the following steps.

[0074] Step 1: Prepare an alkaline solution with a concentration of 1 g / mL by mixing 5 g of potassium hydroxide and 5 g of sodium hydroxide.

[0075] Step 2: Add the alkaline solution, dimethyl sulfoxide, and para-aramid fiber or para-aramid fiber fabric to a mixer in the order of 4 mL: 500 mL: 7.5 g, and stir at 600 r / min for 24 h to obtain a high-concentration aramid pulp fiber mixed gel solution.

[0076] Step 3: Transfer the obtained high-concentration aramid pulp fiber mixed gel solution to a standard pulp desolventizer, add tap water at a ratio of 500mL:9000mL, and desolvent for 40,000 revolutions to obtain aramid pulp fiber desolvent solution.

[0077] Step 4: Filter the aramid pulp fiber disintegration solution from the previous step through a 2800-mesh filter and collect the wet aramid pulp fiber.

[0078] Step 5: Spread the collected wet aramid pulp fibers into a 2mm thick layer, freeze at -60℃ for 8 hours, freeze-dry for 12 hours to obtain a freeze-dried aramid pulp fiber layer;

[0079] Step 6: Add the freeze-dried aramid pulp fiber thin layer to tap water at a ratio of 5g:200mL and decompose for 10,000 revolutions, then filter and collect it through a 2800-mesh filter.

[0080] Step 7: The obtained aramid pulp fiber is vacuum dried at 60°C for 10 hours to obtain highly fine aramid pulp fiber powder.

[0081] Reference Figure 7 The product prepared in Example 4 is in powder form, achieving 79.8% fineness of aramid pulp fibers, with an average fiber length of approximately 28 μm and a specific surface area of ​​16.8 m². 2 / g features low noise, low power consumption, and high operability in the process.

[0082] Example 5

[0083] A highly finely fiberized aramid pulp fiber powder and its preparation method, comprising the following steps.

[0084] Step 1: Prepare an alkaline solution with a concentration of 0.8 g / mL by mixing calcium hydroxide and sodium hydroxide;

[0085] Step 2: Add the alkaline solution, dimethyl sulfoxide, and para-aramid fiber or para-aramid fiber fabric to a mixer in the order of 6 mL: 500 mL: 5.5 g, and stir at 300 r / min for 22 h to obtain a high-concentration aramid pulp fiber mixed gel solution.

[0086] Step 3: Transfer the obtained high-concentration aramid pulp fiber mixed gel solution to a standard pulp desolventizer, add tap water at a ratio of 400mL:800mL, and desolvent for 30,000 revolutions to obtain aramid pulp fiber desolvent solution;

[0087] Step 4: Filter the aramid pulp fiber disintegration solution from the previous step through a 2800-mesh filter and collect the wet aramid pulp fiber.

[0088] Step 5: Spread the collected wet aramid pulp fibers into a 3mm thick layer, freeze at -60℃ for 8 hours, freeze-dry for 12 hours to obtain a freeze-dried aramid pulp fiber layer;

[0089] Step 6: Add the freeze-dried aramid pulp fiber thin layer to tap water at a ratio of 5g:200mL and decompose for 20,000 revolutions. Then filter and collect the solution through a 2800-mesh filter.

[0090] Step 7: The obtained aramid pulp fiber is vacuum dried at 80°C for 8 hours to obtain highly fine aramid pulp fiber powder.

[0091] Reference Figure 8 The technical product prepared in Example 5 is in powder form, achieving 81.9% fineness of aramid pulp fibers, with an average fiber length of approximately 32 μm and a specific surface area of ​​17.5 m². 2 / g features low noise, low power consumption, and high operability in the process.

[0092] Table 1. Aramid pulp yield and related technical parameters

[0093]

[0094] Table 1 shows the yield and related technical parameters of aramid pulp. Analysis reveals that the aramid pulp fiber powder prepared by the process route provided by this invention has a yield exceeding 96%, a fine fiber ratio exceeding 79%, and a specific surface area greater than 15 m². 2 / g.

[0095] Figure 3 , 5 The images shown are transmission electron microscope (TEM) images of the products prepared in Examples 1 and 2, respectively. Analysis reveals that the aramid pulp fibers have nanoscale terminal tentacles, which is unique to the aramid pulp prepared by the process disclosed in this invention. This is also another direct proof of the increased specific surface area, which is corroborated by the data in Table 1.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A process for preparing highly fine aramid pulp fiber powder, characterized in that, Includes the following steps: Step 1: Dimethyl sulfoxide, alkaline solution and para-aramid fiber are added sequentially, and then the mixture is sealed and stirred to obtain a mixed gel of ultra-high concentration fibrillated aramid pulp and fiber. Para-aramid fiber is an aramid fiber with a para-structure 1414. The raw materials for para-aramid fiber are para-aramid spinning, para-cut strands, para-aramid fiber fabrics, or para-aramid fiber scraps. The ratio of alkali solution, dimethyl sulfoxide, and para-aramid fiber is (4-6) mL: (400-500) mL: (5-7.5) g, wherein the alkali solution is a combination or any one of potassium hydroxide, calcium hydroxide, and sodium hydroxide, with a concentration of 0.8 g / mL to 1 g / mL, the stirring reaction time is 20-24 h, and the stirring speed is 300-600 r / min; Step 2: Use water to decompose the ultra-high concentration fibrillated aramid pulp fiber mixed gel solution, then filter and collect to obtain wet aramid pulp fiber; the ratio of ultra-high concentration fibrillated aramid pulp fiber mixed gel solution to water is (400~500) mL : (800~1000) mL, wherein, during decomposition, the rotation speed is 20000~40000 rpm, and the filter screen used during filtration is 1800 mesh~2800 mesh; Step 3: Lay the wet aramid pulp fiber into a thin layer, and freeze and dry it to obtain aramid pulp fiber; the freezing temperature is -0 to -60℃ and the time is 8 to 12 hours, the drying time is 10 to 12 hours, and the thickness of the thin layer is 2 to 3 mm. Step 4: Use tap water to loosen the aramid pulp fibers, then filter, collect, and vacuum dry to obtain highly fine aramid pulp fiber powder. The ratio of aramid pulp fiber to tap water is 5g:200mL; during dissolution, the rotation speed is 10,000 to 20,000 revolutions; during vacuum drying, the temperature is 60 to 120℃ and the time is 5 to 10 hours.

2. An aramid pulp fiber powder obtained by the preparation process of the highly fine aramid pulp fiber as described in claim 1.

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