High-elongation para-aramid fiber and method of making same

Abstract

The application discloses a kind of high elongation p-aramid fiber and preparation method thereof, it is related to high-performance fiber material technical field, with p-phenylenediamine solution and p-phthaloyl chloride is continuously condensed in two steps in low temperature environment, obtains the poly-p-phenyleneterephthalamide polymer with intrinsic viscosity of 6.5dL / g~7.0dL / g;Polymer is dissolved in concentrated sulfuric acid with concentration of 97%~103%, is stirred and dissolved at 80~90 DEG C, obtains the liquid crystal state spinning dope with concentration of 18%~21%;Spinning dope is defoamed by vacuum, filtration, metering, and is extruded through spinneret, enters 20~30 DEG C coagulation bath through 3mm~20mm air layer, forms nascent fiber;Nascent fiber is sequentially neutralized, washed, dried, oiled, and is wound into shape with draft ratio of 2m / min~10m / min, and high elongation p-aramid fiber is prepared.The application is compared with prior art and has the advantages that molecular chain hydrogen bond density is regulated, condensed state structure is optimized, and process is accurately controlled.

Description

Technical Field

[0001] This invention relates to the field of high-performance fiber materials technology, specifically to a high-elongation para-aramid fiber and its preparation method. Background Technology

[0002] Para-aramid fiber is an aromatic polyamide fiber based on poly(p-phenylene terephthalamide). Due to its high strength, high modulus, and high-temperature resistance, it is widely used in aerospace, bulletproof materials, and industrial reinforcement. Its traditional preparation methods typically include low-temperature solution polycondensation, dry-jet wet spinning, and post-treatment drawing processes. Although para-aramid fibers possess excellent mechanical properties, their elongation at break is generally low, typically ≤3.0%, resulting in high brittleness and susceptibility to fracture under dynamic loads or complex deformation scenarios. This deficiency mainly stems from the following technical bottlenecks:

[0003] (1) Defects in molecular chain structure: In the traditional polycondensation process, the hydrogen bond density of PPTA molecular chains is too high, resulting in an overly regular arrangement of molecular chains, which restricts the slippage ability of chain segments and thus reduces the plastic deformation ability of the fiber. (2) Coarse control of process parameters: In the existing spinning process, parameters such as coagulation bath temperature, spinning solution concentration and draw ratio lack precise control, resulting in uneven porosity inside the fiber, which further weakens the elongation performance. (3) Insufficient functional modification: Existing technologies only optimize performance by adjusting process parameters, lacking active control methods for fiber molecular-level structure (such as introducing nano-reinforcing phases or molecular chain condensed state regulators), making it difficult to achieve a synergistic improvement in elongation and strength.

[0004] With the rapid development of flexible electronics, wearable devices and new energy vehicles, the market demand for aramid fibers with both high strength and high elongation is becoming increasingly urgent. There is an urgent need to design a high elongation para-aramid fiber and its preparation method to meet market demand. Summary of the Invention

[0005] The purpose of this invention is to provide a high-elongation para-aramid fiber and its preparation method. By using low-temperature two-step polycondensation, molecular chain hydrogen bond density control and dry-jet wet spinning process optimization, the technical problem of low elongation of traditional aramid fibers is solved.

[0006] Specifically, the technical solution provided by this invention is: a high-elongation para-aramid fiber, comprising the following steps:

[0007] Step 1, Low-temperature two-step polycondensation: p-phenylenediamine solution and terephthaloyl chloride are continuously polycondensed in two steps at low temperature to obtain a poly(p-phenylenediamine terephthaloyl chloride) polymer with an intrinsic viscosity of 6.5 dL / g to 7.0 dL / g;

[0008] Step 1.1: React p-phenylenediamine solution with 30% to 40% terephthaloyl chloride solution at -15℃ to 5℃;

[0009] Step 1.2: At 0℃~10℃, add the remaining 60%~70% of terephthaloyl chloride to carry out a secondary reaction to obtain a yellow powdered polymer;

[0010] Step 2, Dry-jet wet spinning: Dissolve the above polymer in concentrated sulfuric acid with a concentration of 97% to 103%, and stir at 80°C to 90°C to obtain a liquid crystal spinning solution with a concentration of 18% to 21%.

[0011] Step 3, spinning process: After vacuum degassing, filtration and metering, the spinning solution is extruded through a spinneret and enters a coagulation bath at 20℃ to 30℃ through a 3mm to 20mm air layer to form nascent fibers.

[0012] Step 4, Post-treatment: The nascent fibers are neutralized, washed, dried and oiled in sequence, and then wound into shape at a draw ratio of 2m / min to 10m / min to obtain high elongation para-aramid fibers.

[0013] Preferably, the molar ratio of p-phenylenediamine to terephthaloyl chloride is 1:1 to 1.05.

[0014] Preferably, the concentration of the spinning solution in the twin-screw dissolving machine is controlled at 18.5% to 19.5%.

[0015] Preferably, the coagulation bath temperature is 23℃~28℃.

[0016] Preferably, the drying process in the post-processing step uses a three-stage heating roller with temperatures of 100℃~150℃, 160℃~200℃, and 210℃~240℃ respectively.

[0017] Preferably, a high-elongation para-aramid fiber is also provided, prepared by the method of any one of claims 1 to 5, and satisfying the following performance parameters:

[0018] (1) Fiber single fiber fineness: 1.0D~2.5D;

[0019] (2) Elongation at break: 4.0%–5.0%;

[0020] (3) Elastic modulus: 80 GPa~100 GPa;

[0021] (4) Tensile strength: 18cN / dtex~24cN / dtex.

[0022] Preferably, the fiber draw ratio is 2 to 10.

[0023] In the molecular chain arrangement of the fiber, the hydrogen bond density is reduced by 10% to 20% compared with conventional para-aramid fibers, in order to improve the breaking elongation.

[0024] Preferably, the fibers are suitable for use in automotive hoses, tire reinforcement layers, or safety protection applications.

[0025] Preferably, 0.5% to 2% by mass of covalent organic framework (COF) is added to concentrated sulfuric acid. The COF is used to regulate the condensed state structure of the poly(p-phenylene terephthalamide) molecular chain.

[0026] Compared with the prior art, the advantages of this invention are: (1) Hydrogen bond density regulation of molecular chains: by low-temperature two-step polycondensation and COFs embedding, the hydrogen bond density is reduced by 10%-20%, significantly improving the chain segment slippage ability. (2) Optimization of condensed matter structure: the pore structure of COFs can induce PPTA molecular chains to form a nanocomposite structure of "rigid support-flexible connection", balancing strength and elongation. (3) Precise process control: the synergistic optimization of coagulation bath temperature, spinning solution concentration and draw ratio eliminates internal defects of the fiber and improves dynamic mechanical properties. Detailed Implementation

[0027] Example 1

[0028] This embodiment provides a high-elongation para-aramid fiber and its preparation method, specifically including:

[0029] I. Fiber Composition Design

[0030] (1) Main chain structure: The hydrogen bond density in the PPTA molecular chain is 10%-20% lower than that of conventional fibers. The molecular weight distribution is controlled by low-temperature two-step polycondensation, PDI=1.8-2.5, which reduces the molecular chain packing density and improves the chain segment slippage ability.

[0031] (2) Nano-reinforcing phase: Add 0.5%-2% by mass of covalent organic framework material COFs with a pore size of 1.0-3.0 nm and a specific surface area of ​​≥800 m² / g. It can be embedded between PPTA molecular chains to form a "rigid-flexible" synergistic network, which can improve elongation while maintaining strength.

[0032] (3) Surface modifier: Introduce a compound of phosphorus flame retardant and silane coupling agent in a mass ratio of 1:0.2-1:1 to improve the interfacial bonding force between the fiber and the matrix and prevent debonding under dynamic load.

[0033] II. Preparation Method

[0034] (1) At -15℃ to 5℃, p-phenylenediamine PPD is reacted with 30%-40% terephthaloyl chloride TPC to form oligomers;

[0035] (2) Heat to 0℃~10℃, add the remaining TPC to complete the polycondensation, and obtain a PPTA polymer with intrinsic viscosity of 6.5-7.0 dL / g.

[0036] Stepwise temperature control can suppress side reactions, ensure uniform activity at the ends of molecular chains, and reduce branching defects.

[0037] (3) Dry-jet wet spinning: Dissolve PPTA in concentrated sulfuric acid (97%-103%) containing 0.5%-2% COFs and stir at 80℃~90℃ to obtain a liquid crystal spinning solution of 18.5%-19.5%; enter the coagulation bath at 23℃~28℃ through a 3-20 mm air layer to form nascent fibers.

[0038] The introduction of COFs can regulate the condensed state structure of PPTA molecular chains, forming an alternating distribution of ordered microregions and amorphous regions, thereby improving elongation.

[0039] III. Post-processing technology

[0040] (1) The nascent fibers are dried by three-stage heated rollers at 100℃~150℃, 160℃~200℃, and 210℃~240℃ respectively to eliminate internal stress; they are then wound into shape at a draw ratio of 2-10 m / min to finally obtain fibers with a single fiber fineness of 1.0-2.5 D and a breaking elongation of 4.0%-5.0%. Graded drying and drawing can prevent the propagation of microcracks inside the fiber, while optimizing crystallinity and orientation.

[0041] Example 2

[0042] This embodiment provides a high-elongation para-aramid fiber and its preparation method, specifically including:

[0043] I. Fiber Composition Design

[0044] (1) Main chain structure: The hydrogen bond density in the PPTA molecular chain is reduced by 12% - 18% compared with conventional fibers. The molecular weight distribution is strictly controlled by low-temperature two-step polycondensation, PDI = 1.9 - 2.3, which reduces the compactness of the molecular chain and enhances the slip performance of the chain segments.

[0045] (2) Nano-reinforcing phase: Add 1% - 1.5% by mass of covalent organic framework material COFs with a pore size of 1.5 - 2.5 nm and a specific surface area ≥900 m² / g. It can be embedded between PPTA molecular chains to construct a "rigid-flexible" synergistic network, thereby improving elongation while maintaining fiber strength.

[0046] (3) Surface modifier: A compound of nitrogen-containing flame retardant and silane coupling agent is used in a mass ratio of 1:0.5 - 1:0.8 to improve the interfacial bonding force between the fiber and the matrix material and prevent debonding under dynamic load.

[0047] II. Preparation Method

[0048] (1) P-phenylenediamine (PPD) was reacted with 32% - 38% terephthaloyl chloride (TPC) in an environment of -10℃ to 3℃ to generate oligomers. This temperature range can effectively suppress the occurrence of side reactions, ensure uniform activity at the ends of molecular chains, and reduce the generation of branching defects.

[0049] (2) Raise the temperature to 2℃~8℃, add the remaining TPC to complete the polycondensation reaction, and obtain PPTA polymer with intrinsic viscosity of 6.6-6.9 dL / g.

[0050] (3) Dry-jet wet spinning: PPTA is dissolved in concentrated sulfuric acid (98%-102%) containing 1%-1.5% COFs and stirred at 82℃-88℃ to prepare a liquid crystal spinning solution with a concentration of 18.8%-19.2%; after passing through a 5-15 mm air layer, it enters a coagulation bath at 24℃-27℃ to form nascent fibers. The addition of COFs can regulate the condensed state structure of PPTA molecular chains, forming an alternating distribution of ordered micro-regions and amorphous regions, thereby improving the elongation of the fibers.

[0051] III. Post-processing technology

[0052] (1) The nascent fibers are dried by three-stage heating rollers at temperatures set sequentially at 110℃~140℃, 170℃~190℃, and 220℃~235℃ to eliminate internal stress. The fibers are then wound at a draw ratio of 3-8 m / min to produce fibers with a single fiber fineness of 1.2-2.2 D and a breaking elongation of 4.2%-4.8%. The graded drying and drawing process can prevent the propagation of microcracks inside the fibers and optimize the crystallinity and orientation of the fibers.

[0053] Example 3

[0054] This embodiment provides a high-elongation para-aramid fiber and its preparation method, specifically including:

[0055] I. Fiber Composition Design

[0056] (1) Main chain structure: The hydrogen bond density in the PPTA molecular chain is reduced by 15% - 20% compared with conventional fibers. The molecular weight distribution is precisely controlled by low-temperature two-step polycondensation, PDI = 2.0 - 2.4, which reduces the packing density of the molecular chain and improves the slippage ability of the chain segments.

[0057] (2) Nano-reinforcing phase: Add 0.8% - 1.8% by mass of covalent organic framework material COFs with a pore size of 1.2 - 2.8 nm and a specific surface area ≥850 m² / g. It can be embedded between PPTA molecular chains to form a "rigid-flexible" synergistic network structure, which can improve elongation while ensuring fiber strength.

[0058] (3) Surface modifier: A compound of boron flame retardant and silane coupling agent is selected with a mass ratio of 1:0.3 - 1:0.7 to improve the interfacial bonding performance between the fiber and the matrix and prevent debonding under dynamic load.

[0059] II. Preparation Method

[0060] (1) p-phenylenediamine (PPD) was reacted with 35%-40% terephthaloyl chloride (TPC) at -12℃ to 4℃ to generate oligomers. This temperature range can effectively suppress side reactions, ensure uniform activity at the ends of molecular chains, and reduce branching defects.

[0061] (2) Heat to 3℃~9℃, add the remaining TPC to complete the polycondensation reaction, and obtain PPTA polymer with intrinsic viscosity of 6.7-7.0 dL / g.

[0062] (3) Dry-jet wet spinning: PPTA is dissolved in concentrated sulfuric acid (97.5%-102.5%) containing 0.8%-1.8% COFs and stirred at 85℃-90℃ to prepare a liquid crystal spinning solution with a concentration of 19.0%-19.5%; after passing through an 8-18 mm air layer, it enters a coagulation bath at 25℃-28℃ to form nascent fibers. The introduction of COFs can regulate the condensed state structure of PPTA molecular chains, forming an alternating distribution of ordered micro-regions and amorphous regions, thereby improving the elongation of the fibers.

[0063] III. Post-processing technology

[0064] (1) The nascent fibers are dried by three-stage heating rollers at temperatures of 120℃~145℃, 175℃~195℃, and 225℃~240℃ respectively to eliminate internal stress; they are then wound into shape at a draw ratio of 4-9 m / min to finally obtain fibers with a single fiber fineness of 1.5-2.0 D and a breaking elongation of 4.3%-4.9%. Graded drying and drawing can prevent the propagation of microcracks inside the fiber, while optimizing crystallinity and orientation.

[0065] Example 4

[0066] This embodiment provides a high-elongation para-aramid fiber and its preparation method, specifically including:

[0067] I. Fiber Composition Design

[0068] (1) Main chain structure: The hydrogen bond density in the PPTA molecular chain is reduced by 13% - 17% compared with conventional fibers. The molecular weight distribution is precisely controlled by low-temperature two-step polycondensation, PDI = 1.7 - 2.2, which reduces the tightness of molecular chain packing and enhances the slippage ability of chain segments.

[0069] (2) Nano-reinforcing phase: Add 0.6% - 1.6% by mass of covalent organic framework material COFs with a pore size of 1.3 - 2.6 nm and a specific surface area ≥820 m² / g. It can be embedded between PPTA molecular chains to construct a "rigid-flexible" synergistic network, which can improve elongation while maintaining fiber strength.

[0070] (3) Surface modifier: A compound of sulfur-containing flame retardant and silane coupling agent is used in a mass ratio of 1:0.4 - 1:0.6 to improve the interfacial bonding force between the fiber and the matrix material and prevent debonding under dynamic load.

[0071] II. Preparation Method

[0072] (1) p-phenylenediamine (PPD) is reacted with 30%-35% terephthaloyl chloride (TPC) in an environment of -8℃ to 2℃ to generate oligomers. This temperature range can effectively suppress side reactions, ensure uniform activity at the ends of molecular chains, and reduce branching defects.

[0073] (2) Raise the temperature to 1℃~7℃, add the remaining TPC to complete the polycondensation reaction, and obtain PPTA polymer with intrinsic viscosity of 6.5-6.8 dL / g.

[0074] (3) Dry-jet wet spinning: PPTA is dissolved in concentrated sulfuric acid (98.5%-101.5%) containing 0.6%-1.6% COFs, and stirred at 80℃-85℃ to prepare a liquid crystal spinning solution with a concentration of 18.6%-19.0%. After passing through a 6-16 mm air layer, it enters a coagulation bath at 23℃-26℃ to form nascent fibers. The addition of COFs can regulate the condensed state structure of PPTA molecular chains, forming an alternating distribution of ordered micro-regions and amorphous regions, thereby improving the elongation of the fibers.

[0075] III. Post-processing technology

[0076] (1) The nascent fibers are dried by three-stage heating rollers at temperatures set sequentially at 115℃~135℃, 165℃~185℃, and 215℃~230℃ to eliminate internal stress in the fibers. The fibers are then wound at a draw ratio of 5-7 m / min to finally produce fibers with a single fiber fineness of 1.3-2.1 D and a breaking elongation of 4.1%-4.7%. The graded drying and drawing process can prevent the propagation of microcracks inside the fibers and optimize the crystallinity and orientation of the fibers.

[0077] In summary, this solution systematically solves the technical problem of low elongation of traditional para-aramid fibers through molecular-level structural design and process optimization, demonstrating significant innovation and industrial value.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high-elongation para-aramid fiber, characterized in that, Includes the following steps: Step 1, Low-temperature two-step polycondensation: p-phenylenediamine solution and terephthaloyl chloride are continuously polycondensed in two steps at low temperature to obtain a poly(p-phenylenediamine terephthaloyl chloride) polymer with an intrinsic viscosity of 6.5 dL / g to 7.0 dL / g; Step 1.1: React p-phenylenediamine solution with 30% to 40% terephthaloyl chloride solution at -15℃ to 5℃; Step 1.2: At 0℃~10℃, add the remaining 60%~70% of terephthaloyl chloride to carry out a secondary reaction to obtain a yellow powdered polymer; Step 2, Dry-jet wet spinning: Dissolve the above polymer in concentrated sulfuric acid with a concentration of 97% to 103%, and stir at 80°C to 90°C to obtain a liquid crystal spinning solution with a concentration of 18% to 21%. Step 3, spinning process: After vacuum degassing, filtration and metering, the spinning solution is extruded through a spinneret and enters a coagulation bath at 20℃ to 30℃ through a 3mm to 20mm air layer to form nascent fibers. Step 4, Post-treatment: The nascent fibers are neutralized, washed, dried and oiled in sequence, and then wound into shape at a draw ratio of 2m / min to 10m / min to obtain high elongation para-aramid fibers.

2. The method for preparing high-elongation para-aramid fiber according to claim 1, characterized in that, The molar ratio of p-phenylenediamine to terephthaloyl chloride is 1:1 to 1.

05.

3. The method for preparing high-elongation para-aramid fiber according to claim 1, characterized in that, The concentration of the spinning solution in the twin-screw dissolving machine is controlled at 18.5% to 19.5%.

4. The method for preparing high-elongation para-aramid fiber according to claim 1, characterized in that, The temperature of the coagulation bath is 23℃~28℃.

5. The method for preparing high-elongation para-aramid fiber according to claim 1, characterized in that, The drying process in the post-processing step uses a three-stage heating roller with temperatures ranging from 100℃ to 150℃, 160℃ to 200℃, and 210℃ to 240℃, respectively.

6. A high-elongation para-aramid fiber, characterized in that, Prepared by the preparation method according to any one of claims 1 to 5, and satisfying the following performance parameters: (1) Fiber single fiber fineness: 1.0D~2.5D; (2) Elongation at break: 4.0%–5.0%; (3) Elastic modulus: 80 GPa~100 GPa; (4) Tensile strength: 18cN / dtex~24cN / dtex.

7. The high elongation para-aramid fiber according to claim 6, characterized in that, The fiber has a draw ratio of 2 to 10.

8. The high elongation para-aramid fiber according to claim 6, characterized in that, The hydrogen bond density in the molecular chain arrangement of the fiber is 10% to 20% lower than that of conventional para-aramid fibers, thereby improving the elongation at break.

9. A high-elongation para-aramid fiber according to claim 6, characterized in that, The fibers are suitable for use in automotive hoses, tire reinforcement layers, or safety protection applications.

10. The high elongation para-aramid fiber according to claim 1, characterized in that, The concentrated sulfuric acid contains 0.5% to 2% by mass of covalent organic framework materials (COFs), which are used to regulate the condensed state structure of the poly(p-phenylene terephthalamide) molecular chain.