A meta-aramid fibrid and a preparation method and application thereof

Abstract

The present application relates to the technical field of synthetic fiber manufacturing, in particular to a meta-aramid fibrid and a preparation method thereof.The preparation method provided by the present application utilizes electrostatic solution blowing technology combined with hot air traction to make meta-aramid polymer stock solution form superfine fibers, and then ultrasonic is performed to make the fibers stick together or disperse again, so that meta-aramid fibrid with a wide size distribution range is obtained, the thinner fibers can be used as a part of void filling when paper is made, the larger fibers provide better bonding capacity when paper is made, and the prepared paper has excellent bonding performance.Test results show that the meta-aramid fibrid prepared by the preparation method has a tensile strength of 3 kN / m, a longitudinal elongation of 8.4%, a transverse elongation of 6.1%, a longitudinal initial tear strength of 12.3 N, a transverse initial tear strength of 8.2 N, and a breakdown strength of 26.2 kV / mm.

Description

Technical Field

[0001] This invention relates to the field of synthetic fiber manufacturing technology, specifically to a meta-aramid precipitated fiber, its preparation method, and its application. Background Technology

[0002] Meta-aramid precipitated fibers are generally in the form of films or strips, possessing excellent mechanical properties, chemical stability, flame retardancy, and outstanding high-temperature resistance and insulation properties. As a key raw material for high-performance paper-based materials, meta-aramid precipitated fibers play a role in filling chopped fibers and bonding in meta-aramid paper. Its structure and properties are crucial to paper sheet formation and paper quality.

[0003] Currently, domestically produced aramid paper is mostly made by mixing aramid short fibers obtained from wet spinning with precipitated fibers and then preparing it through external hot pressing. However, the resulting aramid paper has poor cohesion and adhesion between the precipitated fibers and short fibers, which has a significant impact on the overall performance of the paper.

[0004] Studies have shown that smaller precipitated fibers can better fill pores, increasing paper density. The denser the paper, the greater its breaking strength. Conversely, larger precipitated fiber membrane structures result in stronger bonding with chopped fibers, leading to greater tear resistance in papermaking. Therefore, obtaining appropriately sized meta-aramid precipitated fibers is crucial for improving the performance of aramid paper. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a meta-aramid precipitated fiber, its preparation method and application. The preparation method provided by the present invention can obtain meta-aramid precipitated fibers with a wide size distribution range. When paper is made, the finer fibers can be used as the void filling part, and the larger fibers provide better bonding ability when paper is made. The resulting paper has excellent bonding performance and therefore higher paper strength.

[0006] This invention provides a method for preparing meta-aramid precipitated fibers, comprising the following steps:

[0007] The meta-aramid polymer dope is electrostatically melt-blown and spun under the action of a hot air stream. The resulting spun fabric is ultrasonicated in water to obtain meta-aramid precipitated fibers. The air pressure of the electrostatic melt-blowing is 0.1 MPa to 0.4 MPa, the voltage of the electrostatic melt-blowing is 18 kV to 25 kV, and the temperature of the hot air stream is 40℃ to 70℃.

[0008] The meta-aramid polymer dope of the present invention is electrostatically melt-blown and spun under the action of hot airflow. The receiving distance of the electrostatic melt-blown is 50 cm to 100 cm. Then the spun material is ultrasonically dispersed and shaped in water to form meta-aramid precipitated fibers. The frequency of the ultrasound is 27 kHz to 33 kHz and the power is 36 W to 44 W.

[0009] This invention involves adding the meta-aramid polymer dope to an electrostatic melt-blowing device, setting the air pressure and voltage for electrostatic melt-blowing, and simultaneously introducing a hot airflow to spin the meta-aramid polymer dope. Under the influence of an electrostatic field, gravity, and hot air stretching, the meta-aramid polymer dope forms ultrafine fibers. Simultaneously, under the action of the hot air, some solvent evaporates. Upon the ultrafine fibers falling onto the water surface, under the action of ultrasound, the fibers collide with each other and re-bond or disperse. At the same time, the internal solvent further exchanges with the water, and finally, the fibers solidify into meta-aramid precipitated fibers with a wide size distribution, appearing as fibrous strips or filamentous films. The meta-aramid precipitated fibers obtained by the preparation method of this invention have a size distribution range of 100 nm to 100 μm.

[0010] The solid content of the meta-aramid polymer dopant solution of the present invention is 3 wt% to 10 wt%, preferably 4 wt% to 8 wt%, and more preferably 4 wt% to 6 wt%. Specifically, the meta-aramid polymer dopant solution of the present invention is an N,N-dimethylacetamide solution of meta-aramid polymer, wherein the mass content of the meta-aramid polymer is the solid content of the meta-aramid polymer dopant solution. The temperature of the meta-aramid polymer dopant solution of the present invention is 40℃ to 70℃.

[0011] The meta-aramid polymer of this invention is obtained by reacting m-phenylenediamine and isophthaloyl chloride. Specifically, it is prepared by low-temperature polycondensation of m-phenylenediamine and isophthaloyl chloride in a solvent. In some embodiments of this invention, the solvent is selected from N,N-dimethylacetamide. In some embodiments of this invention, the molar concentration of m-phenylenediamine is 1.0 mol / L to 1.5 mol / L, and the excess ratio of isophthaloyl chloride is 0.99 to 1.01. In some embodiments of this invention, the reaction temperature is -5°C to 15°C, and the reaction time is 60 min to 120 min.

[0012] This invention also provides meta-aramid precipitated fibers obtained by the preparation method described in any of the above technical solutions, with a size distribution ranging from 100 nm to 100 μm. During papermaking, the finer fibers can act as void fillers, while the larger fibers provide better bonding ability, resulting in paper with excellent adhesion properties. Furthermore, this invention requires less coagulation bath during meta-aramid precipitated fiber forming compared to precipitator forming, reducing the pressure on wastewater treatment and making it suitable for continuous production.

[0013] This invention also provides paper products composed of aramid chopped fibers and meta-aramid precipitated fibers obtained by any of the above-described technical solutions. In some embodiments of this invention, aramid chopped fibers and the meta-aramid precipitated fibers in a mass ratio of (6-7):(3-4) are used for papermaking, followed by high-temperature and high-pressure treatment to obtain the paper products. The paper products obtained by this invention possess excellent bonding properties and strength due to the large size distribution range of the aforementioned meta-aramid precipitated fibers.

[0014] This invention provides a meta-aramid precipitated fiber, its preparation method, and its applications. The preparation method utilizes electrostatic melt blowing technology combined with hot air traction to form ultrafine fibers from a meta-aramid polymer solution. Subsequent ultrasonication further bonds or disperses these fibers, resulting in meta-aramid precipitated fibers with a wide size distribution. During papermaking, the finer fibers can fill voids, while larger fibers provide better bonding, resulting in paper with excellent adhesion properties. This invention's preparation method is for preparing meta-aramid precipitated fibers from meta-aramid polymers. This method is not applicable to para-aramid because para-aramid is typically obtained by low-temperature solution polymerization of p-phenylenediamine and terephthaloyl chloride, directly forming para-aramid resin, unlike the slurry state of meta-aramid, which cannot be directly formed into precipitated fibers in a coagulation bath. Experiments show that when the meta-aramid precipitated fibers obtained by the preparation method described in this invention are used to make paper products, the resulting paper products have a tensile strength of 3 kN / m, a longitudinal elongation of 8.4%, a transverse elongation of 6.1%, a longitudinal initial tear strength of 12.3 N, a transverse initial tear strength of 8.2 N, and a breakdown strength of 26.2 kV / mm. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the preparation method of meta-aramid ultrafine precipitated fiber according to the present invention;

[0016] Figure 2 This is a SEM image of the meta-aramid precipitated fiber product obtained in Example 2 of the present invention. Detailed Implementation

[0017] This invention discloses a meta-aramid precipitated fiber, its preparation method, and its application. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0018] The method for preparing meta-aramid ultrafine precipitated fibers according to the present invention firstly involves low-temperature solution polycondensation to obtain a polymer solution, then diluting the polymer solution to obtain an aramid dope, followed by electrostatic melt blowing to obtain meta-aramid ultrafine fibers, and finally ultrasonic molding to obtain meta-aramid precipitated fibers. Figure 1 As shown, Figure 1 This is a process flow diagram of the preparation method of meta-aramid ultrafine precipitation fiber according to the present invention.

[0019] The present invention will be further described below with reference to the embodiments: Example 1

[0020] 1.0 mol / L m-phenylenediamine was dissolved in N,N-dimethylacetamide, and an excess of isophthaloyl chloride at a ratio of 1:0.99 was added. The initial reaction temperature was controlled at 5°C, and low-temperature solution polycondensation was carried out for 120 min to obtain a meta-aramid polymer. The reaction temperature was then controlled at 50°C, and N,N-dimethylacetamide was added to prepare an aramid dope solution with a solid content of 4 wt%. The prepared aramid solution was added to an electrostatic melt-blowing device with a voltage of 25 kV, an air pressure of 0.1 MPa, a receiving distance of 80 cm, and a 60°C hot airflow. The ultrasonic frequency of the water bath was set to 30 kHz, and the ultrasonic power to 40 W. The solution was then spun into ultrafine fibers under the influence of electrostatic field, gravity, and hot air stretching. Some of the solvent evaporated, and as the ultrafine fibers fell onto the water surface, they collided and re-bonded or dispersed under the action of ultrasound. Simultaneously, the internal solvent and water underwent further solvent exchange, ultimately forming meta-aramid precipitated fibers with a wide size distribution, appearing as strips or films. The mechanical beating degree of these fibers was 45 SR. Under a fiber microscope, the fiber morphology was observed to be ribbon-like or film-like, with a minimum fiber diameter of 200 nm and a maximum of 20 μm. Example 2

[0021] 1.1 mol / L m-phenylenediamine was dissolved in N,N-dimethylacetamide, and an excess of isophthaloyl chloride at a ratio of 1:1 was added. The initial reaction temperature was controlled at 5°C, and low-temperature solution polycondensation was carried out for 100 min to obtain a meta-aramid polymer. The reaction temperature was then controlled at 50°C, and N,N-dimethylacetamide was added to prepare an aramid dope solution with a solid content of 6 wt%. The prepared aramid solution was added to an electrostatic melt-blowing device. The voltage was set to 20 kV, the air pressure to 0.1 MPa, the receiving distance to 50 cm, and a 40°C hot airflow was introduced. The ultrasonic frequency in the water bath was set to 27 kHz, and the ultrasonic power to 36 W. The solution was then spun into ultrafine fibers under the influence of electrostatic field, gravity, and hot air stretching. Some of the solvent evaporated. As the ultrafine fibers fell onto the water surface, they collided and re-bonded or dispersed under ultrasonic action. Simultaneously, the internal solvent exchanged further with the water, ultimately forming meta-aramid precipitated fibers with a wide size distribution, appearing as ribbons or films. The mechanical beating degree of these fibers was 35 SR. Under a microscope, the fiber morphology was observed as ribbons or films, with a minimum fiber diameter of 400 nm and a maximum of 30 μm. Figure 2 As shown, Figure 2 This is a SEM image of the meta-aramid precipitated fiber product obtained in Example 2 of the present invention. Example 3

[0022] 1.0 mol / L m-phenylenediamine was dissolved in N,N-dimethylacetamide, and an excess of isophthaloyl chloride at a ratio of 1:1.005 was added. The initial reaction temperature was controlled at 5°C, and low-temperature solution polycondensation was carried out for 120 min to obtain a meta-aramid polymer. The reaction temperature was then controlled at 50°C, and N,N-dimethylacetamide was added to prepare an aramid dope solution with a solid content of 4 wt%. The prepared aramid solution was added to an electrostatic melt-blowing device with a voltage of 18 kV, an air pressure of 0.4 MPa, a receiving distance of 80 cm, and a 60°C hot airflow. The ultrasonic frequency of the water bath was set to 28 kHz, and the ultrasonic power to 38 W. The solution was then spun into ultrafine fibers under the influence of electrostatic field, gravity, and hot air stretching. Some of the solvent evaporated, and as the ultrafine fibers fell onto the water surface, they collided and re-bonded or dispersed under the action of ultrasound. Simultaneously, the internal solvent and water underwent further solvent exchange, ultimately forming meta-aramid precipitated fibers with a wide size distribution, appearing as strips or films. The mechanical beating degree of these fibers was 40 SR. Under a fiber microscope, the fiber morphology was observed to be ribbon-like or film-like, with a minimum fiber diameter of 100 nm and a maximum of 50 μm. Example 4

[0023] 1.4 mol / L m-phenylenediamine was dissolved in N,N-dimethylacetamide, and an excess of isophthaloyl chloride at a ratio of 1:1.005 was added. The initial reaction temperature was controlled at 5°C, and low-temperature solution polycondensation was carried out for 100 min to obtain a meta-aramid polymer. The reaction temperature was then controlled at 60°C, and N,N-dimethylacetamide was added to prepare an aramid dope solution with a solid content of 8 wt%. The prepared aramid solution was added to an electrostatic melt-blowing device with a voltage of 25 kV, an air pressure of 0.4 MPa, a receiving distance of 100 cm, and a 70°C hot airflow. The ultrasonic frequency of the water bath was set to 30 kHz, and the ultrasonic power to 42 W. The solution was then spun into ultrafine fibers under the influence of electrostatic field, gravity, and hot air stretching. Some of the solvent evaporated, and as the ultrafine fibers fell onto the water surface, they collided and re-bonded or dispersed under the action of ultrasound. Simultaneously, the internal solvent and water underwent further solvent exchange, ultimately forming meta-aramid precipitated fibers with a wide size distribution, appearing as strips or films. The mechanical beating degree of these fibers was 30 SR. Under a fiber microscope, the fiber morphology was observed to be ribbon-like or film-like, with a minimum fiber diameter of 500 nm and a maximum of 40 μm.

[0024] Experimental Example 1

[0025] The meta-aramid precipitated fibers and chopped aramid fibers obtained in Example 1 were made into aramid paper in a paper machine at a ratio of 4:6. After high temperature and high pressure treatment, the resulting paper sheet had a thickness of 0.05 mm, tensile strength of 3 kN / m, elongation of 8.4% in the longitudinal direction and 6.1% in the transverse direction, initial tear strength of 12.3 N in the longitudinal direction and 8.2 N in the transverse direction, and breakdown strength of 26.2 kV / mm.

[0026] Experiment Example 2

[0027] Similar to Experiment 1, except that aramid paper was made using wet-spun precipitated fibers. The resulting paper sheet had a thickness of 0.05 mm, tensile strength of 2.6 kN / m, elongation of 5.5% in the longitudinal direction and 3.4% in the transverse direction, initial tear strength of 10.8 N in the longitudinal direction and 7.8 N in the transverse direction, and breakdown strength of 18.4 kV / mm.

[0028] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing meta-aramid precipitated fibers, characterized in that, Includes the following steps: S1) The meta-aramid polymer dope is electrostatically melt-blown and spun into ultrafine fibers under the action of hot airflow. The resulting spun material is then subjected to ultrasonic treatment in water. At the moment the ultrafine fibers fall onto the water surface, they collide with each other and re-bond or disperse under the action of ultrasound to obtain meta-aramid precipitated fibers. The temperature of the meta-aramid polymer dope is 40℃~70℃. The air pressure of the electrostatic melt blowing is 0.1 MPa to 0.4 MPa, and the voltage of the electrostatic melt blowing is 18 kV to 25 kV. The temperature of the hot airflow is 40℃~70℃.

2. The preparation method according to claim 1, characterized in that, The solid content of the meta-aramid polymer stock solution is 3 wt% to 10 wt%.

3. The preparation method according to claim 1, characterized in that, The meta-aramid polymer stock solution is an N,N-dimethylacetamide solution of meta-aramid polymer.

4. The preparation method according to claim 1, characterized in that, The frequency of the ultrasound is 27 kHz to 33 kHz and the power is 36 W to 44 W.

5. The preparation method according to claim 1, characterized in that, The receiving distance for the electrostatic meltblowing is 50 cm to 100 cm.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The meta-aramid polymer is obtained by reacting m-phenylenediamine with isophthaloyl chloride; The molar concentration of m-phenylenediamine is 1.0 mol / L to 1.5 mol / L, and the excess ratio of isophthaloyl chloride is 0.99 to 1.

01.

7. The preparation method according to claim 6, characterized in that, The reaction temperature is -5℃ to 15℃, and the reaction time is 60 min to 120 min.

8. The meta-aramid precipitated fiber obtained by any one of the preparation methods according to claims 1 to 7, characterized in that, Its size distribution ranges from 100 nm to 100 μm.

9. Paper products, characterized in that, It is composed of meta-aramid precipitated fibers obtained by any of the preparation methods described in claims 1 to 7.

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