Low-energy-consumption dry-method meta-position aramid fiber and production method thereof
By combining low-temperature polymerization and gradient curing with a reverse hot air system, the problems of high energy consumption and low solvent recovery efficiency in the production of meta-aramid fibers have been solved, realizing the production of low-energy, high-strength meta-aramid fibers, which are suitable for large-scale industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI ARAMID VALLEY NEW MATERIALS CO LTD
- Filing Date
- 2025-12-30
- Publication Date
- 2026-05-08
AI Technical Summary
Existing methods for producing meta-aramid fibers are energy-intensive, have low solvent recovery efficiency, cause serious environmental pollution, and have insufficient fiber strength, making it difficult to achieve large-scale industrial production.
The spinning solution is prepared by low-temperature polymerization, combined with dry spinning and gradient curing. A three-zone reverse hot air system and a condensation recovery system are used to achieve gradient cooling of the fiber and reverse evaporation of the solvent, reducing energy consumption and improving solvent recovery rate. The spinning solution is degassed and filtered under vacuum conditions. Gradient temperature control and reverse hot air system are used to ensure high fiber strength and low residue.
It achieves a 37% reduction in fiber energy consumption, an increase in solvent recovery rate to 98%, and an increase in fiber strength to 4.5 cN/dtex. It simplifies the process, reduces environmental pollution, and is suitable for large-scale industrial production.
Smart Images
Figure CN121992522A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of high-performance fiber manufacturing technology, and relates to a meta-aramid fiber and its production method. Specifically, it relates to a low-energy, green meta-aramid production method using N,N-dimethylacetamide as a solvent through dry spinning, and the meta-aramid fiber produced therefrom. Background Technology
[0002] Meta-aramid fiber is a key material in aerospace, special protection and other fields due to its excellent high temperature resistance, high strength, flame retardancy and electrical insulation. At present, the industrial production methods of meta-aramid fiber mainly include wet spinning, dry spinning and N,N-dimethylacetamide (DMAC) wet spinning. However, the above-mentioned existing technologies all have problems such as high energy consumption or large environmental pollution: (1) Wet spinning requires a large amount of coagulation bath and high energy consumption water washing, and the wastewater treatment burden is heavy; (2) Although traditional dry spinning does not require water washing, the hot air temperature is usually not lower than 280℃, resulting in extremely high energy consumption for solvent recovery; (3) DMAC wet spinning relies on water bath coagulation, and the subsequent drying energy consumption is high. (4) The energy consumption of the above methods is generally 8.5 to 12 kWh / kg fiber, and there are problems such as incomplete solvent evaporation and insufficient fiber densification.
[0003] Therefore, there is an urgent need to develop a method for producing meta-aramid fibers that is energy-efficient, has high fiber strength, is cost-controllable, and is suitable for large-scale industrial production, as well as a method for producing meta-aramid fibers based on this method. Summary of the Invention
[0004] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to: (1) provide a low-energy-consumption, high-strength meta-aramid fiber; (2) provide a method for producing meta-aramid fiber with low energy consumption, controllable cost, and suitability for large-scale industrial production.
[0005] To achieve the above-mentioned objectives, this invention provides a low-energy meta-aramid fiber. The spinning solution is prepared by low-temperature polymerization of m-phenylenediamine and isophthaloyl chloride in DMAC at a temperature not exceeding 10°C. The resulting solution is then dry-spun and gradient-cured to obtain the low-energy meta-aramid fiber. Gradient cooling and reverse solvent evaporation are performed within the spinning channel. The meta-aramid fiber has a strength of not less than 4.5 cN / dtex. The energy consumption in the production of the meta-aramid fiber is not more than 6.0 kWh / kg fiber, and the DMAC solvent recovery rate is not less than 98%.
[0006] To achieve the above-mentioned objective, this invention provides an industrial production method for preparing the aforementioned low-energy meta-aramid fiber, comprising the following steps:
[0007] S1. Polymerization and spinning solution preparation: m-phenylenediamine and isophthaloyl chloride are polymerized in DMAC at a temperature not exceeding 10°C to prepare poly(m-phenylenediamine isophthaloyl chloride) (PMIA) / DMAC spinning solution.
[0008] S2. Vacuum degassing and filtration: The above spinning solution is degassed under vacuum and then filtered.
[0009] S3. Dry spinning: The filtered spinning solution is pumped into the spinneret to obtain nascent fibers. The nascent fibers enter the spinning tunnel, where the hot air is controlled by a three-zone gradient temperature.
[0010] S4. Solvent recovery and heat energy circulation: The exhaust gas discharged from the spinning tunnel is introduced into the condensation system after heat exchange, and DMAC is recovered by condensation with a recovery rate of ≥98%; the waste heat released by condensation is reused with a heat recovery efficiency of ≥65%.
[0011] S5. Stretching and heat setting: After stretching and heat setting, the nascent fibers are obtained as meta-aramid fibers with a strength ≥4.5cN / dtex.
[0012] Furthermore, in the industrial production method of low-energy meta-aramid fiber provided by the present invention, in step "S1", the solid content of the spinning solution is 20-25 wt%, and the intrinsic viscosity of the spinning solution is ≥1.8 dL / g.
[0013] Furthermore, in the industrial production method of low-energy meta-aramid fiber provided by the present invention, in step "S2", the degassing temperature is 40-50℃, the degassing vacuum degree is ≤-0.095MPa, the degassing time is 30-60min, and the filtration accuracy is ≤5μm.
[0014] Furthermore, in the industrial production method of low-energy meta-aramid fiber provided by the present invention, in step "S3", the orifice diameter of the spinneret is 0.06-0.08 mm and the number of orifices is 1000-3000; the fiber is ejected from the spinneret at a temperature of 80-100°C.
[0015] Furthermore, in the industrial production method of low-energy meta-aramid fiber provided by this invention, in step "S3", the three-zone gradient temperature is as follows: the hot air temperature in the first zone (inlet section) is controlled at 120-140℃, and the wind speed is set to 0.8-1.2m / s; the hot air temperature in the second zone (middle section) is controlled at 100-120℃, and the wind speed is set to 1.5-2.0m / s; the hot air temperature in the third zone (outlet section) is controlled at 80-90℃, and the wind speed is set to 0.5-0.8m / s.
[0016] Furthermore, in the industrial production method of low-energy meta-aramid fiber provided by this invention, the height of the spinning tunnel is ≤5.5m, the spinning tunnel adopts a reverse three-zone hot air system, the first zone and the second zone are equipped with auxiliary air inlets and outlets, and the air inlets are equipped with auxiliary heating systems; fresh hot air enters from the air inlet at the bottom side wall of the third zone, flows upward and counter-currently through the second zone and the first zone, and is discharged from the air outlet at the upper side wall of the first zone; the maximum temperature of the spinning tunnel is not higher than 140℃.
[0017] Furthermore, in the industrial production method of low-energy meta-aramid fiber provided by the present invention, the air inlet is an annular perforated plate with an opening rate of 25% to 35%; the air outlet is an annular exhaust trough connected to a negative pressure fan.
[0018] Furthermore, in the industrial production method of low-energy meta-aramid fiber provided by the present invention, the condensation temperature in step "S4" is not higher than -10℃.
[0019] Furthermore, in the industrial production method of low-energy meta-aramid fiber provided by the present invention, in step "S4", the draw ratio is 1.5 to 2.5; the setting temperature is 180 to 220°C; and the setting time is 30 to 60 seconds.
[0020] The present invention has the following technical effects: (1) Breakthrough reduction in energy consumption: By integrating a gradient hot air coagulation and tail gas condensation heat recovery system, the total energy consumption is reduced to ≤5.8kWh / kg fiber, which saves more than 37% compared with the existing dry and wet processes (energy consumption is 9.2~11.5kWh / kg). (2) Significantly improved solvent recovery efficiency: The efficient recovery of single DMAC solvent is achieved, with a recovery rate of ≥98%, which is significantly higher than the existing dry (about 92%) and wet (about 85%, water-containing system) processes. (3) Milder process conditions and better product performance: While reducing the maximum hot air temperature of spinning from 280℃ in the existing dry process to 140℃, the strength of the obtained fiber is improved to ≥4.5cN / dtex, which is better than the comparative products. (4) Green and simple process: No water bath coagulation and wastewater treatment are required, which simplifies the process and reduces environmental protection costs, meeting the needs of green production. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of wind speed and temperature zoning used in this invention;
[0022] Figure 2 This is a schematic diagram of the recycling process used in this invention. Detailed Implementation
[0023] This invention provides an industrial production method for low-energy dry-process meta-aramid fibers, comprising the following steps:
[0024] S1. Polymerization and Spinning Solution Preparation: Under nitrogen protection, m-phenylenediamine and isophthaloyl chloride were polymerized at low temperature in DMAC to prepare PMIA / DMAC spinning solution. Low-temperature polymerization refers to controlling the polymerization temperature to ≤10℃. High-quality spinning solution is a prerequisite for achieving high-performance fiber dry spinning. The inventors discovered that only by preparing a high-viscosity spinning solution can the industrialization of subsequent spinning processes be guaranteed. Through extensive experiments, the inventors found that only by preparing PMIA / DMAC with a solid content of 20wt%–25wt% and an intrinsic viscosity ≥1.8 dL / g can the subsequent industrial production of this invention be realized.
[0025] S2. Vacuum Degassing and Filtration: The spinning solution is degassed under vacuum conditions and then filtered. High-quality spinning solution is a prerequisite for achieving high-performance dry spinning of fibers. The inventors discovered that only when the spinning solution meets high uniformity can subsequent spinning processes be industrialized. Through extensive experimentation, the inventors found that degassing the prepared spinning solution at 40–50°C and a vacuum degree ≤ -0.095 MPa for 30–60 minutes, followed by filtration with a precision ≤ 5 μm, meets the industrial production requirements of subsequent spinning processes in this invention. Degassing is mainly used to ensure the uniformity of the spinning solution, while filtration is mainly used to remove impurities.
[0026] S3. Dry spinning and gradient curing: The spinning solution is pumped into the spinneret to obtain nascent fibers. The nascent fibers enter the spinning tunnel, and the hot air is controlled by a three-zone gradient temperature. The spinneret has an orifice diameter of 0.06-0.08 mm, an orifice count of 1000-3000, and the fiber is ejected from the spinneret at a temperature of 80-100℃.
[0027] The resulting nascent fibers (filaments) enter a spinning tunnel with a height of ≤5.5m. The hot air inside the spinning tunnel is controlled by a three-zone gradient temperature. The specific wind speed and temperature distribution within the spinning tunnel are illustrated in the diagram. Figure 1 Zone 1 is the entrance area ( Figure 1 The temperature of T1 in the zone is 120-140℃, and the wind speed in zone 1 is ( Figure 1 The air intake in zone 1) is 0.8–1.2 m / s; zone 2, i.e., the middle section ( Figure 1 The temperature of T2 in zone 2 is 100-120℃, and the wind speed in zone 2 is ( Figure 1 The air intake (2) in the middle is 1.5-2.0 m / s; the third zone is the outlet zone ( Figure 1 The temperature of T3 in zone 3 is 80-90℃, and the wind speed in zone 3 is ( Figure 1 The intake airflow (3) is 0.5–0.8 m / s.
[0028] The design of the spinning tunnel and the hot air control method are aimed at achieving graded cooling of the fiber and reverse evaporation and solidification of the solvent, which is also a key innovation of this invention. The maximum temperature of the tunnel is controlled at 140℃, below the DMAC boiling point, but through high-velocity convection mass transfer and gradient temperature design, complete solvent evaporation (residual ≤0.5wt%) is achieved, avoiding fiber degradation and energy waste caused by high temperatures. The spinning tunnel adopts a reverse three-zone hot air system, such as... Figure 1 As shown, fresh hot air enters from the air inlet on the bottom side wall of Zone 3 (temperature 80-90℃), flows upwards against the current through Zones 2 and 1, and exits from the air outlet on the upper side wall of Zone 1. Zones 1 and 2 are equipped with auxiliary air inlets and outlets; the air inlets are equipped with an auxiliary heating system. The air inlet is an annular perforated plate with an opening ratio of 25-35%; the air outlet is an annular exhaust duct connected to a negative pressure fan to maximize the solvent concentration gradient, achieving a DMAC evaporation rate ≥99.5%.
[0029] S4. Solvent Recovery and Heat Cycle: After heat exchange, the exhaust gas from the spinning tunnel is introduced into the condensation system; for example... Figure 2 As shown, DMAC solvent is condensed and recovered at a low temperature of ≤-10℃, ensuring a solvent recovery rate of ≥98%; the waste heat released during the condensation process is used to preheat the incoming fresh air through a heat exchanger, realizing the recycling of heat energy, and the system heat recovery efficiency is ≥65%.
[0030] S5. Stretching and heat setting: The nascent fibers formed in the spinning tunnel are stretched, and the stretch ratio is controlled to be 1.5 to 2.5. Then, the stretched fibers are placed on hot rollers at 180 to 220°C for heat setting for 30 to 60 seconds, and finally high-performance meta-aramid fibers with a strength ≥ 4.5 cN / dtex are obtained.
[0031] Example 1
[0032] This embodiment uses commercially available m-phenylenediamine, isophthaloyl chloride, DMAC, etc., and the specific preparation steps are as follows:
[0033] (1) Polymerization and spinning solution preparation: Under nitrogen protection, 1000g of m-phenylenediamine was added to 4000g of DMAC solvent, and 685g of isophthaloyl chloride was slowly added dropwise while stirring in an ice bath. The reaction temperature was controlled at 8℃ to obtain a PMIA / DMAC spinning solution with a solid content of about 22wt% and an intrinsic viscosity of 2.1dL / g.
[0034] (2) Degassing and filtration: The above spinning solution was degassed for 45 minutes under vacuum conditions of 45℃ and -0.097MPa, and then passed through a filter with a filtration accuracy of 5μm.
[0035] (3) Dry spinning: The spinning solution is pumped to a spinneret with 2000 holes and a diameter of 0.07 mm, and extruded at 90°C to form nascent fibers. The fibers then enter a spinning tunnel with a height of 5.5 m. The tunnel is divided into three zones for hot air control: Zone 1 (inlet) temperature 130°C, air velocity 1.0 m / s; Zone 2 (middle section) temperature 110°C, air velocity 1.8 m / s; Zone 3 (outlet) temperature 85°C, air velocity 0.6 m / s. The outer wall of the tunnel is equipped with electric heating to maintain a stable temperature.
[0036] (4) Solvent recovery and heat cycle: The exhaust gas discharged from the tunnel first recovers waste heat through a heat exchanger, and then enters the condensation system for deep condensation at -15℃. The recovery rate of DMAC solvent was measured to be 98.5%. The recovered waste heat is used to preheat the air entering the system to achieve heat energy cycle.
[0037] (5) Stretching and setting: The pre-cured fiber is stretched at a stretch ratio of 2.0 and then set on a hot roller at 200°C for 45 seconds.
[0038] The prepared meta-aramid fibers have a fineness of 2.0 dtex and a breaking strength of 4.8 cN / dtex. Testing revealed a DMAC residue content of only 0.4 wt% in the fibers, an outlet fiber temperature of 88℃, and a smooth, non-adhesive surface. The overall energy consumption of the entire production process was calculated to be 5.6 kWh / kg fiber, with a heat recovery efficiency of 69.7%.
[0039] Example 2
[0040] This embodiment uses commercially available m-phenylenediamine, isophthaloyl chloride, DMAC, etc., and the specific preparation steps are as follows:
[0041] (1) Polymerization and spinning solution preparation: Same as in Example 1, using the same formula and conditions, a spinning solution with a solid content of about 22wt% and an intrinsic viscosity of 2.1dL / g was prepared.
[0042] (2) Degassing and filtration: Same as in Example 1, degassing was performed at 45°C and -0.097MPa for 45 minutes, followed by filtration through 5μm.
[0043] (3) Dry spinning: The spinning solution is sprayed out under the same conditions (90℃, 2000 holes, 0.07mm aperture). After the nascent fibers enter the tunnel, the hot air control parameters are adjusted as follows: Zone 1 temperature 140℃, wind speed 1.0m / s; Zone 2 temperature 120℃, wind speed 1.8m / s; Zone 3 temperature 90℃, wind speed 0.6m / s. The external insulation settings of the tunnel remain unchanged.
[0044] (4) Solvent recovery and thermal cycling: Same as in Example 1, the tail gas is condensed at -15℃ to recover DMAC.
[0045] (5) Stretching and shaping: Same as in Example 1, with a stretching ratio of 2.0, shaping on a hot roller at 200°C for 45 seconds.
[0046] The prepared meta-aramid fibers had a fineness of 2.0 dtex and a breaking strength of 4.6 cN / dtex. Testing revealed a DMAC residue content of 0.3 wt% in the fibers, an outlet fiber temperature of 92℃, and a smooth, non-adhesive surface. The overall energy consumption for the entire production process was calculated to be 5.8 kWh / kg fiber, with a heat recovery efficiency of 68.4% for the heat exchanger.
[0047] Example 3
[0048] This embodiment uses commercially available m-phenylenediamine, isophthaloyl chloride, DMAC, etc., and the specific preparation steps are as follows:
[0049] (1) Polymerization: m-phenylenediamine and isophthaloyl chloride were reacted in DMAC at 5°C to prepare a spinning solution with a solid content of 20.0 wt% and an intrinsic viscosity of 1.85 dL / g.
[0050] (2) Degassing and filtration: Same as in Example 1, degassing was performed at 45°C and -0.097MPa for 45 minutes, followed by filtration through 5μm.
[0051] (3) Spinning and curing: The spinning solution is sprayed out at 80℃. The hot air parameters of the tunnel are set as follows: Zone 1: 120℃, wind speed 0.8m / s; Zone 2: 100℃, wind speed 1.5m / s; Zone 3: 80℃, wind speed 0.5m / s.
[0052] (4) Use a draw ratio of 1.5 and set it on a hot roller at 180°C.
[0053] The fiber strength is 4.52 cN / dtex, the residual DMAC is 0.5 wt%, the solvent recovery rate is 98.1%, the comprehensive energy consumption is 5.3 kWh / kg, and the heat recovery efficiency of the heat exchanger is 72.3%.
[0054] Example 4
[0055] This embodiment uses commercially available m-phenylenediamine, isophthaloyl chloride, DMAC, etc., and the specific preparation steps are as follows:
[0056] (1) Polymerization: The reaction temperature was controlled at 10℃ to obtain a high solid content spinning solution with a solid content of 25.0wt% and an intrinsic viscosity of 2.4dL / g.
[0057] (2) Degassing and filtration: Same as in Example 1, degassing was performed at 45°C and -0.097MPa for 45 minutes, followed by filtration through 5μm.
[0058] (3) Spinning and curing: The spinning solution is sprayed out at 100℃. The hot air parameters of the tunnel are set as follows: Zone 1: 140℃, wind speed 1.2m / s; Zone 2: 120℃, wind speed 2.0m / s; Zone 3: 90℃, wind speed 0.8m / s.
[0059] (4) Use a draw ratio of 2.5 and set it on a hot roller at 220°C.
[0060] The fiber strength reaches 4.9 cN / dtex, the DMAC residue is 0.25 wt%, the solvent recovery rate is 98.2%, the comprehensive energy consumption is 5.8 kWh / kg, and the heat recovery efficiency of the heat exchanger is 66.4%.
[0061] Comparative Example 1 (using traditional wet spinning process)
[0062] Traditional wet spinning was employed. Using the same spinning solution as in Example 1, the fibers were extruded into a water-based coagulation bath for shaping, followed by multiple water washes and high-temperature drying. The resulting fibers had a strength of 4.1 cN / dtex, with a total energy consumption as high as 11.0 kWh / kg (mainly consumed in washing and drying). Furthermore, DMAC dissolved in water to form a dilute solution, resulting in high recycling costs; the actual effective solvent recovery rate was ~85%, and a large amount of wastewater was generated.
[0063] Comparative Example 2 (dry spinning, using constant temperature hot air, without gradient control)
[0064] The polymerization and spinning steps are the same as in Example 1, but the hot air gradient is eliminated, and the entire 5.5m tunnel is set to a constant temperature of 120℃ and a constant wind speed of 1.0m / s.
[0065] The fiber exhibits significant defects: a rough surface and a small amount of tangled fibers. Strength drops to 4.0 cN / dtex, and DMAC residue reaches as high as 1.2 wt%. To reduce the residue to acceptable levels, an additional temperature increase to 150°C is required, resulting in energy consumption rising to 6.5 kWh / kg.
[0066] It can be seen that simple constant-temperature hot air cannot achieve uniform and complete solvent removal at low temperatures. The gradient control of this invention (high-temperature rapid setting → medium-temperature enhanced diffusion → low-temperature gentle curing) is the key to achieving fiber structure densification, high strength, and low residue under low heat load, and its design is non-obvious.
[0067] Comparative Example 3 (using high-temperature polymerization)
[0068] The polymerization reaction temperature was increased to 25 °C, and the remaining steps were the same as in Example 1.
[0069] Due to the increased exothermic polymerization and side reactions, the intrinsic viscosity of the resulting spinning solution was only 1.5 dL / g, which compromised its properties. This resulted in a high breakage rate and poor spinnability during spinning. The final fiber strength was only 3.8 cN / dtex, and it contained numerous fuzzy fibers. High-quality spinning solution (high viscosity, high uniformity) is a prerequisite for achieving high-performance dry spinning.
Claims
1. A low energy meta-aramid fiber, characterized by A spinning solution is prepared by low-temperature polymerization of m-phenylenediamine and isophthaloyl chloride in DMAC at a temperature not exceeding 10°C. The solution is then dry-spun and gradient-cured to obtain low-energy meta-aramid fiber. Gradient cooling and reverse solvent evaporation are performed within the spinning tunnel. The strength of the meta-aramid fiber is not less than 4.5 cN / dtex. The energy consumption in the production of the meta-aramid fiber is not more than 6.0 kWh / kg fiber. The DMAC recovery rate is not less than 98%, and the heat recovery rate is not less than 65%.
2. An industrial production method for preparing low-energy meta-aramid fibers as described in claim 1, characterized in that... Including the following steps: S1. Polymerization and spinning solution preparation: Poly(m-phenylene diamine) and isophthaloyl chloride are polymerized in DMAC at a temperature not exceeding 10°C to prepare poly(m-phenylene isophthaloyl chloride) (PMIA) / DMAC spinning solution. S2. Vacuum degassing and filtration: The above spinning solution is degassed under vacuum and then filtered. S3. Dry spinning: The filtered spinning solution is pumped into the spinneret to obtain nascent fibers. The nascent fibers enter the spinning tunnel, where the hot air is controlled by a three-zone gradient temperature. S4. Solvent recovery and heat energy circulation: The exhaust gas discharged from the spinning tunnel is introduced into the condensation system after heat exchange, and DMAC is recovered by condensation with a recovery rate of ≥98%; the waste heat released by condensation is reused with a heat recovery efficiency of ≥65%. S5. Stretching and heat setting: After stretching and heat setting, the nascent fibers are obtained as meta-aramid fibers with a strength ≥4.5cN / dtex.
3. The industrial production method of low-energy meta-aramid fiber as described in claim 2, characterized in that, In step "S1", the solid content of the spinning solution is 20-25 wt%, and the intrinsic viscosity of the spinning solution is ≥1.8 dL / g.
4. The industrial production method of low-energy meta-aramid fiber as described in claim 2, characterized in that, In step "S2", the degassing temperature is 40-50℃, the degassing vacuum degree is ≤-0.095MPa, the degassing time is 30-60min, and the filtration accuracy is ≤5μm.
5. The industrial production method of low-energy meta-aramid fiber as described in claim 2, characterized in that, In step "S3", the spinneret has an orifice diameter of 0.06 to 0.08 mm and a number of orifices of 1000 to 3000; the fiber is ejected from the spinneret at a temperature of 80 to 100°C.
6. The industrial production method of low-energy meta-aramid fiber as described in claim 2, characterized in that, In step "S3", the three-zone gradient temperature is as follows: the hot air temperature in the first zone (inlet section) is controlled at 120-140℃, and the wind speed is set to 0.8-1.2m / s; the hot air temperature in the second zone (middle section) is controlled at 100-120℃, and the wind speed is set to 1.5-2.0m / s. The hot air temperature in the third zone (exit section) is controlled at 80-90℃, and the wind speed is set at 0.5-0.8m / s.
7. The industrial production method of low-energy meta-aramid fiber as described in claim 2, characterized in that, The spinning tunnel is ≤5.5m high and adopts a reverse three-zone hot air system. The first and second zones are equipped with auxiliary air inlets and outlets, and the air inlets are equipped with auxiliary heating systems. Fresh hot air enters from the air inlet at the bottom side wall of the third zone, flows upwards against the current through the second and first zones, and exits from the air outlet at the upper side wall of the first zone. The maximum temperature of the spinning tunnel is not higher than 140℃.
8. The industrial production method of low-energy meta-aramid fiber as described in claim 7, characterized in that... The air inlet is an annular perforated plate with an opening rate of 25% to 35%; the air outlet is an annular exhaust duct connected to a negative pressure fan.
9. The industrial production method of low-energy meta-aramid fiber as described in claim 2, characterized in that, In step "S4", the condensation temperature is not higher than -10°C.
10. The industrial production method of low-energy meta-aramid fiber as described in claim 2, characterized in that, In step "S4", the draw ratio is 1.5 to 2.5; the setting temperature is 180 to 220°C; and the setting time is 30 to 60 seconds.