Para-aramid fiber treatment method based on microwave-infrared synergistic field effect

Abstract

The invention provides a para-aramid fiber processing method based on a microwave-infrared synergistic field effect, and relates to the technical field of high-performance fiber manufacturing. The treatment method comprises the following steps: carrying out heat treatment on undried para-aramid fibers to obtain para-aramid fibers subjected to heat treatment; wherein the heat treatment comprises microwave treatment, infrared treatment and gas quenching shock cooling treatment which are sequentially carried out. According to the processing method of the para-aramid fiber, a'microwave unwrapping-infrared orientation-shock cooling locking 'three-section energy field cooperation mechanism is adopted, gradient energy field time sequence action is performed on the undried fiber, and a'dynamic self-alignment effect' of a molecular chain is triggered, so that the elastic modulus and the orientation degree are remarkably improved.

Description

Technical Field

[0001] This invention relates to the technical field of high-performance fiber manufacturing, and in particular to a method for processing para-aramid fibers based on microwave-infrared synergistic field effect. Specifically, it relates to a production method that utilizes the microwave and infrared synergistic field effect to rapidly heat-treat undried fibers, thereby significantly improving fiber modulus through molecular chain orientation control. Background Technology

[0002] Poly(p-phenylene terephthalamide) (PPTA) possesses excellent properties such as ultra-high strength, high modulus, high temperature resistance, acid and alkali resistance, and light weight. Its strength is 5-6 times that of steel wire, its modulus is 2-3 times that of steel wire or glass fiber, and its toughness is twice that of steel wire, while its weight is only about 1 / 5 of that of steel wire. It does not decompose or melt at 560 degrees Celsius. Thanks to the ultra-high strength, modulus, and excellent acid, alkali, and high temperature resistance of aramid fibers, they are widely used in military, aerospace, lightweight optical cables, and automotive weight reduction, among other fields, offering irreplaceable advantages.

[0003] The industry is currently facing three major technical challenges: (1) Low thermal efficiency: Traditional hot air / hot roller drying has low heat transfer efficiency (<50℃ / min) and insufficient molecular chain rearrangement; (2) High temperature damage risk: High temperature heat treatment (≥500℃) can easily lead to carbonization of fiber surface and a decrease in breaking elongation of more than 30%; (3) Energy consumption and precision control bottleneck: Existing equipment has high energy consumption and poor temperature control precision (±5℃ or more), resulting in the CV value (coefficient of variation) of key indicators such as fiber fineness and modulus exceeding 5%.

[0004] CN118241330A discloses an aramid spinning post-processing system and method. The post-processing system includes a drying device, a drawing device, and a setting device. Multiple microwave heaters and infrared temperature measuring devices are arranged along the aramid spinning feed direction in the drying device, drawing device, and setting device. While it uses microwave heating to address the problem of uneven fiber heating, it is limited to optimizing temperature control precision (adjusting microwave power through infrared temperature feedback) and does not address the core issue of molecular chain orientation. The described "multi-stage drying channel" design may lead to distortion and deformation of the fiber molecular chains.

[0005] CN109763374A discloses a flexible far-infrared heating aramid nanofiber film and its preparation method, including the following steps: (1) stirring carbon nanotubes in a mixed solution of concentrated sulfuric acid and concentrated nitric acid to obtain a uniformly dispersed modified carbon nanotube solution; injecting deionized water into the para-aramid nanofiber solution in the DMSO / KOH system under high pressure while stirring to obtain an aramid nanofiber solution dispersed in the DMSO / KOH / H2O mixed system; (2) filtration the para-aramid nanofiber solution dispersed in the DMSO / KOH / H2O mixed system with deionized water under vacuum. (2) Wash with water and ethanol until gelatinous, then disperse in deionized water to obtain para-aramid nanofiber solution; (3) Add phosphoric acid solution to para-aramid nanofiber solution to react and obtain modified para-aramid nanofiber solution; (4) Mix modified carbon nanotube solution and modified para-aramid nanofiber solution, the mass ratio of carbon nanotube to para-aramid nanofiber after mixing is (30-70):(70-30), and then disperse by ultrasonication to obtain CNTs@ANFs mixed solution; (5) Paper and dry CNTs@ANFs mixed solution to obtain flexible far-infrared heating aramid nanofiber film. Its infrared technology is mainly used for material heating rather than fiber orientation modification, and the process is complicated (requiring concentrated sulfuric acid / nitric acid treatment of carbon nanotubes), and cannot be used for continuous fiber production.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a method for processing para-aramid fibers based on microwave-infrared synergistic field effects, aiming to provide a high-modulus processing method and system for para-aramid fibers with low energy consumption, high efficiency, and precise structural control. The core objective is to rapidly heat-treat undried fibers through microwave and infrared synergistic field effects, significantly improving the uniformity and orientation of fiber molecular chains, thereby achieving a leapfrog increase in fiber modulus.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a method for processing para-aramid fibers based on microwave-infrared synergistic field effect, the method comprising: Undried para-aramid fibers are heat-treated to obtain heat-treated para-aramid fibers; wherein the heat treatment includes microwave treatment, infrared treatment and gas quenching treatment performed sequentially.

[0009] Furthermore, the moisture content of the undried para-aramid fiber is 20-40%, preferably 26-30%.

[0010] Furthermore, the frequency of the microwave processing is 0.9~4 GHz, preferably 2.45 GHz.

[0011] Furthermore, the temperature of the microwave treatment is 60~90℃.

[0012] Furthermore, the microwave treatment time is 40~70 s, preferably 60 s.

[0013] Furthermore, the infrared processing is performed in the mid-wave infrared band, preferably in the 3~5 μm band.

[0014] Furthermore, the infrared processing temperature is 80~290℃.

[0015] Furthermore, the infrared processing time is 20-40 s, preferably 30 s.

[0016] Furthermore, the gas quenching and rapid cooling treatment specifically involves spraying gas mist onto the para-aramid fibers to cause a rapid drop in their temperature.

[0017] Furthermore, the temperature of the aerosol spray is -60 to -10°C.

[0018] Furthermore, the cooling rate of the gas quenching rapid cooling treatment is ≥50℃ / s.

[0019] Furthermore, the gas quenching and rapid cooling treatment time is 1~20 s.

[0020] Furthermore, the undried para-aramid fiber is prepared by the following steps: Para-aramid fibers and concentrated sulfuric acid are mixed, dissolved, and degassed to obtain a spinning slurry; The spinning slurry is spun by dry-jet wet spinning, and then coagulated in a coagulation bath, alkali washed, and water washed in sequence to obtain the undried para-aramid fiber.

[0021] Furthermore, the mass ratio of the para-aramid to concentrated sulfuric acid is 1:(4~5).

[0022] Furthermore, the dissolution temperature is 80~90℃, and the dissolution time is 30~60 min.

[0023] Furthermore, the spinning process parameters include: the diameter of the spinneret is 0.03~0.2 mm, the number of holes is 500~1500, and the spinning speed is 280~750 m / min.

[0024] Furthermore, the coagulation bath is 10 wt% dilute sulfuric acid; the coagulation temperature is 0~10℃; and the coagulation time is 1~30 s.

[0025] Furthermore, the alkaline solution used in the alkaline washing is a 25% calcium hydroxide aqueous solution; the temperature of the alkaline washing is 10~30℃; and the washing time is 1~30 s.

[0026] Furthermore, the temperature of the water wash is 30~50℃; the washing time is 1~30 s.

[0027] In a second aspect, the present invention provides a para-aramid fiber, which is obtained by the para-aramid fiber processing method based on microwave-infrared synergistic field effect described in the first aspect.

[0028] Furthermore, the elastic modulus of the para-aramid fiber is 120 GPa or higher, preferably 121 to 132 GPa.

[0029] Furthermore, the orientation degree of the para-aramid fiber is 87% or higher, preferably 87.8 to 89.8%.

[0030] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for processing para-aramid fibers described in this invention uses a three-stage energy field synergistic mechanism of “microwave unwinding-infrared orientation-rapid cooling locking” to trigger the “dynamic self-alignment effect” of molecular chains by applying gradient energy field sequential action to the undried fibers, which significantly improves the elastic modulus and orientation degree. The elastic modulus increases from 111~118 GPa in the traditional process to 121~132 GPa, an increase of more than 12%; the orientation degree increases from 86.4~87.9% to 87.8~89.8%.

[0031] (2) The quality and efficiency of the treatment method for para-aramid fibers described in this invention are significantly improved. The total treatment time is 90~120 s, which is more than 60% shorter than the traditional process (the traditional process is ≥300 s), and the production efficiency is greatly improved.

[0032] (3) The method for processing para-aramid fibers described in this invention uses non-contact heating to avoid fiber damage; it does not require organic solvents, is environmentally friendly, and is suitable for continuous production. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1Scanning electron microscope image of para-aramid fibers obtained by the processing method provided in Embodiment 1 of the present invention.

[0035] Figure 2 Scanning electron microscope image of para-aramid fibers obtained by the processing method provided in Embodiment 2 of the present invention.

[0036] Figure 3 Scanning electron microscope image of para-aramid fibers obtained by the processing method provided in Embodiment 3 of the present invention.

[0037] Figure 4 This is a scanning electron microscope image of the para-aramid fibers obtained by the processing method provided in Comparative Example 1 of the present invention.

[0038] Figure 5 This is a scanning electron microscope image of the para-aramid fibers obtained by the processing method provided in Comparative Example 2 of the present invention.

[0039] Figure 6 This is a scanning electron microscope image of the para-aramid fibers obtained by the processing method provided in Comparative Example 3 of the present invention.

[0040] Figure 7 The graph shows the orientation degree of the para-aramid fibers obtained by the processing methods provided in the various embodiments and comparative examples of the present invention. Detailed Implementation

[0041] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In a first aspect, the present invention provides a method for processing para-aramid fibers based on microwave-infrared synergistic field effect, the method comprising: Undried para-aramid fibers are heat-treated to obtain heat-treated para-aramid fibers; wherein the heat treatment includes microwave treatment, infrared treatment and gas quenching treatment performed sequentially.

[0044] It should be noted that this invention creatively proposes a three-stage energy field synergistic mechanism of "microwave unwinding-infrared orientation-rapid cooling locking", specifically microwave unwinding, infrared orientation, and rapid cooling locking (MIR-Treatment). By applying gradient energy field sequentially to the undried fibers, the "dynamic self-alignment effect" of the molecular chains is triggered.

[0045] This invention provides an energy field synergy mechanism: (1) Microwave segment: Molecular-level "micro-boiling" is generated by utilizing the dielectric loss of water molecules, which instantly reduces the resistance to chain segment movement (activation energy is reduced from 210 kJ / mol to 85 kJ / mol), and dissociates hydrogen bond entanglement points. (2) Infrared segment: CN bond stretching vibration is selectively excited, forming a directional thermal energy gradient in the fiber axis, driving the chain segments to slide and orient along the tension direction. (3) Gas quenching and rapid cooling: Instantaneous solidification of the liquid crystal structure is achieved through phase change kinetic control.

[0046] As an optional implementation, the moisture content of the undried para-aramid fiber is 20-40%, for example, it can be 20%, 22%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, 35%, 36%, 38%, 40%, etc.

[0047] In a preferred embodiment, the moisture content of the undried para-aramid fiber is 26-30%.

[0048] It should be noted that the moisture content control window is 20~40% (optimal 28±2%), which forms a "molecular bearing" lubricating layer, reducing the resistance to chain segment migration by 60%.

[0049] As an optional implementation, the frequency of the microwave processing is 0.9~4 GHz, for example, it can be 0.9 GHz, 1 GHz, 1.5 GHz, 2 GHz, 2.5 GHz, 3 GHz, 3.5 GHz, 4 GHz, etc.

[0050] In a preferred embodiment, the frequency of the microwave processing is 2.45 GHz.

[0051] As an optional implementation, the temperature of the microwave treatment is 60~90℃, for example, it can be 60℃, 65℃, 70℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 88℃, 90℃, etc.

[0052] It should be noted that the processing method described in this invention achieves precise temperature gradient control, with the microwave zone at 80±5℃, to prevent water molecule evaporation.

[0053] As an optional implementation, the microwave processing time is 40~70 s, for example, it can be 40 s, 42 s, 45 s, 48 ​​s, 50 s, 52 s, 55 s, 58 s, 60 s, 62 s, 65 s, 68 s, 70 s, etc.

[0054] In a preferred embodiment, the microwave treatment time is 60 s.

[0055] As an optional implementation, the infrared processing is performed in the mid-wave infrared band.

[0056] As an optional implementation, the infrared processing band is 3~5 μm, for example, it can be 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5 μm, etc.

[0057] As an optional implementation, the infrared processing temperature is 80~290℃, for example, it can be 80℃, 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, 220℃, 240℃, 260℃, 280℃, 290℃, etc.

[0058] It should be noted that the processing method described in this invention achieves precise temperature gradient control, with the infrared region at 260±2℃ (below the thermal decomposition threshold of 300℃).

[0059] As an optional implementation, the infrared processing time is 20~40 s, for example, it can be 20 s, 22 s, 24 s, 25 s, 26 s, 28 s, 30 s, 32 s, 34 s, 35 s, 36 s, 38 s, 40 s, etc.

[0060] In a preferred embodiment, the infrared processing time is 30 seconds.

[0061] As an optional implementation, the gas quenching and cooling treatment specifically involves spraying gas mist onto the para-aramid fibers to cause a sudden drop in temperature.

[0062] As an optional implementation, the temperature of the aerosol spray is -60 to -10°C, for example, it can be -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, etc.

[0063] As an optional implementation, the cooling rate of the gas quenching rapid cooling treatment is ≥50℃ / s, for example, it can be 50℃ / s, 52℃ / s, 54℃ / s, 56℃ / s, 58℃ / s, 60℃ / s, 70℃ / s, 80℃ / s, 90℃ / s, 100℃ / s, 120℃ / s, 140℃ / s, 150℃ / s, 200℃ / s, etc.

[0064] As an optional implementation, the gas quenching and rapid cooling treatment time is 1~20 s, for example, it can be 1 s, 2 s, 4 s, 5 s, 6 s, 8 s, 10 s, 12 s, 14 s, 15 s, 16 s, 18 s, 20 s, etc.

[0065] It should be noted that the processing method described in this invention achieves timing control: microwave-dominated period (first 40~70 s, optimal 60 s), infrared-dominated period (last 20~40 s, optimal 30 s), gas quenching (cooling rate ≥50℃ / s), and instantaneous solidification of the liquid crystal structure is achieved through phase change kinetic control.

[0066] As an optional implementation, the undried para-aramid fiber is prepared by the following steps: Para-aramid fibers and concentrated sulfuric acid are mixed, dissolved, and degassed to obtain a spinning slurry; The spinning slurry is spun by dry-jet wet spinning, and then coagulated in a coagulation bath, alkali washed, and water washed in sequence to obtain the undried para-aramid fiber.

[0067] As an optional implementation, the mass ratio of the para-aramid to concentrated sulfuric acid is 1:(4~5), for example, it can be 1:4, 1:4.2, 1:4.4, 1:4.5, 1:4.6, 1:4.8, 1:5, etc.

[0068] As an optional implementation, the dissolution temperature is 80~90℃, for example, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, etc., and the dissolution time is 30~60 min, for example, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0069] As an optional implementation, the spinning process parameters include: the diameter of the spinneret orifice is 0.03~0.2 mm, for example, 0.03 mm, 0.05 mm, 0.06 mm, 0.08 mm, 0.1 mm, 0.12 mm, 0.14 mm, 0.16 mm, 0.18 mm, 0.2 mm, etc.; the number of orifices is 500~1500, for example, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, etc.; and the spinning speed is 280~750 m / min, for example, 280 m / min, 300 m / min, 350 m / min, 400 m / min, 450 m / min, 500 m / min, 550 m / min, 600 m / min, 650 m / min, etc. m / min, 700 m / min, 750 m / min, etc.

[0070] As an optional implementation, the coagulation bath is 10 wt% dilute sulfuric acid.

[0071] As an optional implementation, the solidification temperature is 0~10℃, for example, it can be 0℃, 2℃, 4℃, 6℃, 8℃, 10℃, etc.; the solidification time is 1~30 s, for example, it can be 1 s, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, etc.

[0072] As an optional implementation, the alkaline solution used in the alkaline washing is an aqueous solution of calcium hydroxide.

[0073] As an optional implementation, the temperature of the alkaline washing is 10~30℃, for example, it can be 10℃, 15℃, 20℃, 25℃, 30℃, etc.; the time of the alkaline washing is 1~30 s, for example, it can be 1 s, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, etc.

[0074] As an optional implementation, the water washing temperature is 30~50℃, for example, it can be 30℃, 35℃, 40℃, 45℃, 50℃, etc.; the water washing time is 1~30 s, for example, it can be 1 s, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, etc.

[0075] In a second aspect, the present invention provides a para-aramid fiber, which is obtained by the para-aramid fiber processing method based on microwave-infrared synergistic field effect described in the first aspect.

[0076] As an optional embodiment, the elastic modulus of the para-aramid fiber is 120 GPa or more, preferably 121 to 132 GPa.

[0077] As an optional embodiment, the orientation degree of the para-aramid fiber is 87% or more, preferably 87.8 to 89.8%.

[0078] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0079] Example 1 This embodiment provides a high-modulus para-aramid fiber, and the preparation steps of the high-modulus para-aramid fiber are as follows: (a) Dissolve 100 kg of PPTA in 412 kg of concentrated sulfuric acid (concentration 19.5 wt%), dissolve at 83°C for 30 min, and then degas to obtain spinning slurry; (b) The spinning slurry is spun by dry-jet wet spinning. After passing through a spinneret with a diameter of 0.05 mm and 1000 holes, the spinning speed is 350 m / min. Then, it is coagulated in a coagulation bath, washed with alkali and water in sequence to obtain undried para-aramid fibers with a moisture content of 28%. The coagulation bath is 10 wt% dilute sulfuric acid, the coagulation temperature is 6℃, and the coagulation time is 10s; the alkaline washing uses a 25 wt% calcium hydroxide aqueous solution, the alkaline washing temperature is 20℃, and the alkaline washing time is 20s; the water washing temperature is 40℃, and the water washing time is 25s. (c) The undried para-aramid fiber is subjected to heat treatment, including microwave treatment zone: 2.45 GHz, 80℃ constant temperature treatment for 60 s; infrared treatment zone: 3~5 μm band, 260℃ directional radiation for 30 s, infrared thermal imaging to monitor the temperature distribution in real time (ΔT<2℃); gas quenching and locking zone: -50℃ gas mist spray, the fiber temperature drops to 50℃ within 3 s, and then it is wound to obtain the finished 1420 D para-aramid high modulus fiber.

[0080] Figure 1 A scanning electron microscope (SEM) image of the para-aramid fibers obtained by the processing method provided in Embodiment 1 of the present invention, as shown below. Figure 1 As shown, the surface is very flat and smooth.

[0081] Example 2 This embodiment provides a high-modulus para-aramid fiber, and the preparation steps of the high-modulus para-aramid fiber are as follows: (a) Dissolve 100 kg of PPTA in 412 kg of concentrated sulfuric acid (concentration 19.5 wt%), dissolve at 83°C for 30 min, and then degas to obtain spinning slurry; (b) The spinning slurry is spun by dry-jet wet spinning. After passing through a spinneret with a diameter of 0.05 mm and 1000 holes, the spinning speed is 350 m / min. Then, it is coagulated in a coagulation bath, washed with alkali and water in sequence to obtain undried para-aramid fibers with a moisture content of 28%. The coagulation bath is 10 wt% dilute sulfuric acid, the coagulation temperature is 6℃, and the coagulation time is 10 s; the alkaline washing uses a 25 wt% calcium hydroxide aqueous solution, the alkaline washing temperature is 20℃, and the alkaline washing time is 20 s; the water washing temperature is 40℃, and the water washing time is 25 s. (c) The undried para-aramid fiber is subjected to heat treatment, including microwave treatment zone: 2.45 GHz, 60℃ constant temperature treatment for 40 s; infrared treatment zone: 3~5 μm band, 220℃ directional radiation for 20 s, infrared thermal imaging to monitor the temperature distribution in real time (ΔT<2℃); gas quenching and locking zone: -50℃ gas mist spray, the fiber temperature drops to 50℃ within 3 s, and then it is wound to obtain the finished 1420 D para-aramid high modulus fiber.

[0082] Figure 2 A scanning electron microscope (SEM) image of the para-aramid fibers obtained by the processing method provided in Embodiment 2 of the present invention, as shown below. Figure 2 As shown, the fiber surface is smooth and uniform.

[0083] Example 3 This embodiment provides a high-modulus para-aramid fiber, and the preparation steps of the high-modulus para-aramid fiber are as follows: (a) Dissolve 100 kg of PPTA in 412 kg of concentrated sulfuric acid (concentration 19.5 wt%), dissolve at 83°C for 30 min, and then degas to obtain spinning slurry; (b) The spinning slurry is spun by dry-jet wet spinning. After passing through a spinneret with a diameter of 0.05 mm and 1000 holes, the spinning speed is 350 m / min. Then, it is coagulated in a coagulation bath, washed with alkali and water in sequence to obtain undried para-aramid fibers with a moisture content of 28%. The coagulation bath is 10 wt% dilute sulfuric acid, the coagulation temperature is 6℃, and the coagulation time is 10 s; the alkaline washing uses a 25 wt% calcium hydroxide aqueous solution, the alkaline washing temperature is 20℃, and the alkaline washing time is 20 s; the water washing temperature is 40℃, and the water washing time is 25 s. (c) The undried para-aramid fiber is subjected to heat treatment, including microwave treatment zone: 2.45 GHz, 90℃ constant temperature treatment for 70 s; infrared treatment zone: 3~5 μm band, 290℃ directional radiation for 40 s, infrared thermal imaging to monitor the temperature distribution in real time (ΔT<2℃); gas quenching and locking zone: -50℃ gas mist spray, the fiber temperature drops to 50℃ within 3 s, and then it is wound to obtain the finished 1420 D para-aramid high modulus fiber.

[0084] Figure 3 A scanning electron microscope (SEM) image of the para-aramid fibers obtained by the processing method provided in Embodiment 3 of the present invention, as shown below. Figure 3 As shown, the fiber surface is smooth, but has a few spots.

[0085] Comparative Example 1 This comparative example provides a para-aramid fiber, and the preparation steps of the para-aramid fiber are as follows: (a) Dissolve 100 kg of PPTA in 412 kg of concentrated sulfuric acid (concentration 19.5 wt%), dissolve at 83°C for 30 min, and then degas to obtain spinning slurry; (b) The spinning slurry is spun by dry-jet wet spinning. After passing through a spinneret with a diameter of 0.05 mm and 1000 holes, the spinning speed is 350 m / min. Then, it is coagulated in a coagulation bath, washed with alkali and water in sequence to obtain undried para-aramid fibers. The coagulation bath is 10 wt% dilute sulfuric acid, the coagulation temperature is 6℃, and the coagulation time is 10s; the alkaline washing uses a 25% calcium hydroxide aqueous solution, the alkaline washing temperature is 20℃, and the alkaline washing time is 20s; the water washing temperature is 40℃, and the water washing time is 25s. (c) The undried para-aramid fiber is heat-treated by using a hot roller contact method to dry the fiber at a temperature of 260°C for 240 seconds, and then wound up to obtain the finished 1420 D para-aramid fiber.

[0086] Figure 4 The image shown is a scanning electron microscope (SEM) image of the para-aramid fibers obtained by the processing method provided in Comparative Example 1 of this invention. Figure 4 As shown, the fiber surface is basically smooth, but there are a few scratches.

[0087] Comparative Example 2 This comparative example provides a para-aramid fiber, which differs from Example 1 only in that, in step (c), the heat treatment in the infrared treatment zone is no longer performed; the other steps are the same as in Example 1.

[0088] Figure 5The image shown is a scanning electron microscope (SEM) image of the para-aramid fibers obtained by the processing method provided in Comparative Example 2 of this invention. Figure 5 As shown, the fiber surface is basically smooth, but has a few minor bumps.

[0089] Comparative Example 3 This comparative example provides a para-aramid fiber, which differs from Example 1 only in that, in step (c), the heat treatment in the microwave treatment zone is no longer performed; the other steps are the same as in Example 1.

[0090] Figure 6 The image shown is a scanning electron microscope (SEM) image of the para-aramid fibers obtained by the processing method provided in Comparative Example 3 of this invention. Figure 6 As shown, the fiber surface is basically smooth, but there are a few cracks.

[0091] Test Example 1 Test samples: para-aramid high-modulus fibers prepared in Examples 1-3 and para-aramid fibers prepared in Comparative Examples 1-3.

[0092] Test method: (1) Linear density: Tested according to ASTM D1907; (2) Strength: Tested according to ASTM D7269 (American standard); (3) Modulus: Tested according to ASTM D7269 American standard; (4) Elongation at break: Tested according to ASTM D7269.

[0093] The specific test results are shown in Table 1 below: Table 1

[0094] As shown in Table 1, the method for treating para-aramid fibers described in this invention utilizes a three-stage energy field synergistic mechanism of "microwave unwinding - infrared orientation - rapid cooling and locking" to trigger the "dynamic self-alignment effect" of molecular chains by applying a gradient energy field to the undried fibers, thereby significantly improving the elastic modulus. Specifically, the elastic modulus increases from 111~118 GPa in the traditional process to 121~132 GPa, an increase of more than 12%.

[0095] Test Example 2 Test samples: para-aramid high-modulus fibers prepared in Examples 1-3 and para-aramid fibers prepared in Comparative Examples 1-3.

[0096] Test method: Orientation degree: The orientation degree of aramid fibers was tested using wide-angle X-ray diffraction (XRD).

[0097] The specific test results are shown in Table 2 below. Figure 7 As shown: Table 2

[0098] As shown in Table 2, the method for treating para-aramid fibers described in this invention utilizes a three-stage energy field synergistic mechanism of "microwave unwinding - infrared orientation - rapid cooling and locking". By applying a gradient energy field to the undried fibers in a sequential manner, the "dynamic self-alignment effect" of the molecular chains is triggered, resulting in a significant improvement in the degree of orientation, which increases from 86.4~87.9% to 87.8~89.8%.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating para-aramid fibers based on microwave-infrared synergistic field effect, characterized in that, The processing method includes: Undried para-aramid fibers are heat-treated to obtain heat-treated para-aramid fibers; wherein the heat treatment includes microwave treatment, infrared treatment and gas quenching treatment performed sequentially.

2. The method for treating para-aramid fibers based on microwave-infrared synergistic field effect according to claim 1, characterized in that, The moisture content of the undried para-aramid fiber is 20-40%, preferably 26-30%.

3. The method for treating para-aramid fibers based on microwave-infrared synergistic field effect according to claim 1, characterized in that, The frequency of the microwave processing is 0.9~4 GHz, preferably 2.45 GHz; Preferably, the temperature of the microwave treatment is 60~90℃; Preferably, the microwave treatment time is 40-70 s, and more preferably 60 s.

4. The method for treating para-aramid fibers based on microwave-infrared synergistic field effect according to claim 1, characterized in that, The infrared processing is performed in the mid-wave infrared band, preferably 3~5 μm. Preferably, the infrared processing temperature is 80~290℃; Preferably, the infrared processing time is 20-40 s, and more preferably 30 s.

5. The method for treating para-aramid fibers based on microwave-infrared synergistic field effect according to claim 1, characterized in that, The gas quenching and cooling process specifically involves spraying gas mist onto the para-aramid fiber to cause a rapid drop in the temperature of the para-aramid fiber. Preferably, the temperature of the aerosol spray is -60 to -10°C; Preferably, the cooling rate of the gas quenching rapid cooling treatment is ≥50℃ / s; Preferably, the gas quenching and rapid cooling treatment time is 1~20 s.

6. The method for treating para-aramid fibers based on microwave-infrared synergistic field effect according to claim 1, characterized in that, The undried para-aramid fiber was prepared by the following steps: Para-aramid fibers and concentrated sulfuric acid are mixed, dissolved, and degassed to obtain a spinning slurry; The spinning slurry is spun by dry-jet wet spinning, and then coagulated in a coagulation bath, alkali washed, and water washed in sequence to obtain the undried para-aramid fiber.

7. The method for treating para-aramid fibers based on microwave-infrared synergistic field effect according to claim 6, characterized in that, The mass ratio of para-aramid to concentrated sulfuric acid is 1:(4~5); Preferably, the dissolution temperature is 80~90℃, and the dissolution time is 30~60 min; Preferably, the spinning process parameters include: the diameter of the spinneret is 0.03~0.2 mm, the number of holes is 500~1500, and the spinning speed is 280~750 m / min.

8. The method for treating para-aramid fibers based on microwave-infrared synergistic field effect according to claim 6, characterized in that, The coagulation bath is dilute sulfuric acid; the coagulation temperature is 0~10℃; and the coagulation time is 1~30 s. Preferably, the alkaline solution used in the alkaline washing is an aqueous solution of calcium hydroxide; the temperature of the alkaline washing is 10~30℃; and the washing time is 1~30 s. Preferably, the water washing temperature is 30~50℃; the water washing time is 1~30 s.

9. A para-aramid fiber, characterized in that, The para-aramid fiber is obtained by the method for processing para-aramid fibers based on microwave-infrared synergistic field effect as described in any one of claims 1 to 8.

10. The para-aramid fiber according to claim 9, characterized in that, The elastic modulus of the para-aramid fiber is 120 GPa or higher, preferably 121-132 GPa; Preferably, the orientation degree of the para-aramid fiber is 87% or higher, and more preferably 87.8 to 89.8%.

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