A method of making porous nylon fibers

Abstract

This invention relates to the field of nylon fiber manufacturing technology and provides a method for preparing porous nylon fibers. The method includes feeding a sheath nylon, a crosslinking agent, and a core nylon into a die; the pore-forming agent decomposes to generate gas, which forms a uniform closed-cell structure in situ within the core nylon; in a fusing chamber, the crosslinking agent is sandwiched between the core nylon and the sheath nylon, generating a nylon material with a sheath-core nylon crosslinking structure; the nylon material is drawn out through a spinneret, bundled by an oiling roller, and oiled to form nylon fiber bundles; the nylon fiber bundles are graded, stretched, and wound to obtain the finished nylon fiber. This invention achieves this by using the gas from the decomposition of the pore-forming agent to form a uniform closed-cell structure in the core nylon; and by using the crosslinking agent to form a sheath-core nylon crosslinking structure with chemical bonding and low thermal conductivity between the core and sheath layers. This significantly reduces the thermal conductivity and weight of the nylon fiber while maintaining high strength, resulting in lightweight and warm nylon fibers.

Description

Technical Field

[0001] This invention belongs to the field of nylon fiber manufacturing technology, and particularly relates to a method for preparing porous nylon fibers. Background Technology

[0002] With the upgrading of demand for functional textiles, lightweighting and efficient warmth retention have become the core research and development directions for nylon fibers. Nylon 6 and nylon 66 are widely used in the textile industry due to their excellent mechanical properties, elastic recovery rate, and abrasion resistance. However, pure nylon fibers have a high thermal conductivity, reaching 0.337 W / m·K, which makes it difficult to meet the warmth retention requirements in low-temperature environments.

[0003] Currently, solutions to improve the warmth retention of nylon fibers mainly fall into two categories: one is structural modification, which achieves insulation by constructing a hollow structure to retain still air. For example, Chinese patent application CN205329254U discloses a novel lightweight and warm elastic yarn of nylon 6, which uses a twisted structure of hollow monofilaments and solid monofilaments. The hollow monofilament structure reduces the thermal conductivity of the fiber. However, the large cavity size of this fiber easily leads to a decrease in the fiber's mechanical strength, making it difficult to balance breaking strength.

[0004] Another approach is material composite modification, which involves combining low thermal conductivity materials with a nylon matrix. For example, Chinese patent application CN120311334A discloses a silica aerogel-nylon 6 composite fiber. This involves surface modification of the silica aerogel using an alcohol ester method, followed by blending and spinning with nylon 6 chips. The extremely low thermal conductivity of the aerogel enhances its warmth retention. However, this approach has significant drawbacks: the aerogel is highly hydrophilic and brittle, exhibiting poor compatibility with the nylon matrix. Complex surface modification and composite masterbatch preparation processes are required to prevent agglomeration, making the process cumbersome.

[0005] In conclusion, the existing technology obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the Invention

[0006] To address the aforementioned shortcomings, this invention provides a method for preparing porous nylon fibers, solving the technical problems of current nylon fibers having a single heat-insulating mechanism, complex processes, and low production efficiency.

[0007] To address the above problems, the present invention provides a method for preparing porous nylon fibers, comprising the following steps:

[0008] S1, feed the skin material into the skin extruder; feed the core material and core auxiliary materials into the core extruder;

[0009] Both the outer layer material and the core layer material are: spinning-grade nylon 6 chips;

[0010] The amount of core layer auxiliary material added is 1-3% of the mass of the core layer raw material;

[0011] The core layer auxiliary material includes fillers and porogens; the mass ratio of the filler to the porogen is 1~5:1; the porogen is azodicarbonamide;

[0012] S2, the sheath material forms molten sheath nylon in the sheath extruder; the core material and core auxiliary materials form molten core nylon in the core extruder;

[0013] S3, the outer layer nylon, crosslinking agent and core layer nylon are respectively fed into the mold, the mass percentage of the three is 40~90%:0.1~2%:10~60%; the crosslinking agent is 3-isocyanate-propyltriethoxysilane;

[0014] The die is provided with a core layer channel, an intermediate channel and a skin layer channel; the die is provided with a core layer feed pipe that connects to the core layer channel, an intermediate feed pipe that connects to the intermediate channel and a skin layer feed pipe that connects to the skin layer channel; the skin layer nylon, crosslinking agent and core layer nylon are respectively fed into the corresponding channels through the skin layer feed pipe, the intermediate feed pipe and the core layer feed pipe.

[0015] The die is also provided with a fusion cavity that connects the discharge ports of each channel; the fusion cavity is also connected to multiple spinnerets provided on the die.

[0016] The temperature of the die is 260°C; in the die, the pore-forming agent decomposes to produce N2 and CO2 gases, which form a uniform closed-cell structure with a pore size of 1~10μm in situ in the core nylon.

[0017] Within the fusion cavity, the crosslinking agent is sandwiched between the core nylon and the sheath nylon, and the following reaction occurs:

[0018] The amide groups of the crosslinking agent undergo a covalent bonding reaction with the amide groups of the core layer nylon to generate silane-modified core layer nylon;

[0019] The amide groups of the crosslinking agent undergo a covalent bonding reaction with the amide groups of the nylon skin to generate silane-modified nylon skin;

[0020] Silane-modified core nylon and silane-modified skin nylon undergo hydrolysis and condensation reactions to generate nylon material with a skin-core nylon cross-linked structure;

[0021] S4, after the nylon material is drawn out through the spinneret, it is bundled and oiled by the oiling roller to form nylon fiber bundles;

[0022] S5, nylon fiber bundles are graded and stretched by multiple guide rollers, and then wound into finished nylon fiber products.

[0023] According to the method for preparing porous nylon fiber of the present invention, the viscosity of the nylon 6 chips in step S1 is 2.4 dl / g to 2.6 dl / g, and the water content is ≤0.05%.

[0024] According to the method for preparing porous nylon fiber of the present invention, the filler in step S1 is: modified silica aerogel powder;

[0025] The modified silica aerogel powder has a particle size of 1~5μm, a porosity ≥95%, and a specific surface area of ​​600~1000 m². 2 / g.

[0026] According to the method for preparing porous nylon fibers of the present invention, the preparation steps of the modified silica aerogel powder include:

[0027] Z1, dry silica aerogel powder is dispersed in anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension; the mass ratio of silica aerogel powder to anhydrous ethanol is 1:20.

[0028] Z2, add 1% KH550 of the aerogel powder by mass, stir at 55℃ for 2 hours to obtain modified aerogel by grafting reaction.

[0029] Z3, centrifugal separation process, to obtain modified aerogel solid;

[0030] Z4 was washed three times with anhydrous ethanol; then dried under vacuum at 60°C for 4 hours to obtain the modified silica aerogel powder.

[0031] According to the method for preparing porous nylon fibers of the present invention, the core layer auxiliary material in step S1 is premixed before being added to the core layer extruder.

[0032] According to the method for preparing porous nylon fiber of the present invention, the screw speed of the extruder in step S2 is 200 rpm; the screw is divided into three temperature zones along the feeding direction; the screw temperatures of the three temperature zones are 210℃, 245℃ and 255℃ respectively;

[0033] The screw speed of the core extruder is 100 rpm; along the feeding direction, the screw is divided into three temperature zones; the screw temperatures of the three temperature zones are 190℃, 230℃ and 240℃ respectively.

[0034] According to the method for preparing porous nylon fiber of the present invention, the mass percentage of the sheath nylon, crosslinking agent and core nylon in step S3 is 50~80%:0.5~1%:15~20%.

[0035] According to the method for preparing porous nylon fibers of the present invention, the graded stretching in step S5 is a three-stage stretching with a stretching ratio of 3.0 times; the parameters of the three-stage stretching are as follows:

[0036] First stage of stretching: The guide roller rotates at 1200 m / min and the temperature is 60℃;

[0037] Second stage stretching: The guide roller rotates at 2400 m / min and the temperature is 120℃;

[0038] Third-stage stretching: The guide roller rotates at 3600 m / min and the temperature is 130℃.

[0039] According to the porous nylon fiber preparation method of the present invention, the winding speed of the winding forming in step S5 is 4000 m / min and the winding tension is 20 cN.

[0040] According to the method for preparing porous nylon fiber of the present invention, the crosslinking agent is stored in a crosslinking agent tank, the crosslinking agent tank is connected to a feeding pump, and the feeding pump is connected to a die; the feeding pump is a high-pressure pump.

[0041] The outer layer feed pipe, middle feed pipe, and core layer feed pipe of the die are respectively connected to the outer layer extruder, the feeding pump, and the core layer extruder.

[0042] The beneficial effects of this invention are: The invention forms a uniform closed-cell structure in the core nylon through the gas produced by the decomposition of the pore-forming agent; and a sheath-core nylon cross-linked structure with chemical bonding and low thermal conductivity network function is formed between the core and sheath layers through a cross-linking agent. This significantly reduces the thermal conductivity and weight of nylon fibers while maintaining high strength, resulting in lightweight and warm nylon fibers. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the fiber manufacturing equipment of the present invention;

[0044] Figure 2 yes Figure 1 A schematic diagram of the cross-sectional structure of the die;

[0045] Figure 3 yes Figure 2 Schematic diagram of the structure in the AA direction;

[0046] Figure 4 This is the decomposition reaction formula of the porogen of the present invention;

[0047] Figure 5 This is the reaction formula between the crosslinking agent and the core layer nylon of the present invention;

[0048] Figure 6 This is the reaction formula between the crosslinking agent and the nylon skin layer of the present invention;

[0049] Figure 7 This is the reaction formula between the core layer nylon and the sheath nylon of the present invention;

[0050] Figure 8 This is a scanning electron microscope image of the cross-section of the nylon fiber of the present invention;

[0051] In the diagram: 1-Sheet extruder, 2-Core extruder, 3-Crosslinking agent tank, 31-Feed pump; 4-Die, 41-Core channel, 411-Core feed pipe; 42-Intermediate channel, 421-Intermediate feed pipe; 43-Sheet channel, 431-Sheet feed pipe; 44-Fusion chamber, 45-Spinneret; 5-Oil roller, 51-Guide roller. Detailed Implementation

[0052] See Figure 1 This invention provides a method for preparing porous nylon fibers, comprising the following steps:

[0053] S1, put the skin material into the skin extruder 1; put the core material and core auxiliary materials into the core extruder 2;

[0054] Both the outer layer material and the core layer material are: spinning-grade nylon 6 chips;

[0055] The amount of core layer auxiliary material added is 1-3% of the mass of the core layer raw material;

[0056] The core layer auxiliary material includes fillers and pore-forming agents; the mass ratio of the fillers to the pore-forming agents is 1~5:1.

[0057] In one embodiment, the viscosity of the nylon 6 chips in step S1 is 2.4 dl / g to 2.6 dl / g, and the water content is ≤0.05%.

[0058] In one embodiment, the filler in step S1 is: modified silica aerogel powder;

[0059] The modified silica aerogel powder has a particle size of 1~5μm, a thermal conductivity of 0.013~0.020 W / (m·K), a porosity of ≥95%, and a specific surface area of ​​600~1000 m². 2 / g;

[0060] Furthermore, the preparation steps of the modified silica aerogel powder include:

[0061] Z1, dry silica aerogel powder is dispersed in anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension; the mass ratio of silica aerogel powder to anhydrous ethanol is 1:20.

[0062] Z2, add 1% KH550 (γ-aminopropyltriethoxysilane) of the aerogel powder by mass, stir at 55℃ for 2h to obtain modified aerogel by grafting reaction;

[0063] The grafting reaction process is as follows: KH550 hydrolyzes to generate silanol groups, which then undergo a condensation reaction with the silanol groups on the surface of the aerogel to obtain the modified aerogel.

[0064] Z3, centrifugal separation process, to obtain modified aerogel solid;

[0065] Z4 was washed three times with anhydrous ethanol; then, it was vacuum dried at 60°C for 4 hours to obtain the modified silica aerogel powder.

[0066] Preferably, the porogen is azodicarbonamide (ADC).

[0067] The azodicarbonamide has a purity of ≥99%, a decomposition temperature of 230~260℃, a decomposition rate of 1.2~1.5mg / s, and decomposition products of N2 and CO2 with no solid residue.

[0068] As one embodiment, the core layer auxiliary material in step S1 is premixed before being added to the core layer extruder 2; this ensures that when mixed in the core layer extruder 2, the pore-forming agent can be uniformly coated on the surface of the aerogel powder, avoiding uneven local gas generation or filler agglomeration during subsequent spinning.

[0069] Optionally, the premixing process involves placing the filler and pore-forming agent into a high-speed mixer and mixing for 30 minutes at room temperature and a speed of 300 rpm.

[0070] S2, the sheath material forms molten sheath nylon in the sheath extruder 1; the core material and core auxiliary materials form molten core nylon in the core extruder 2;

[0071] As one embodiment, the screw speed of the skin extruder 1 in step S2 is 200 rpm; along the feeding direction, the screw is divided into three temperature zones; the screw temperatures of the three temperature zones are 210℃, 245℃ and 255℃, respectively;

[0072] The screw speed of the core extruder 2 is 100 rpm; along the feeding direction, the screw is divided into three temperature zones; the screw temperatures of the three temperature zones are 190℃, 230℃ and 240℃ respectively.

[0073] S3, the outer layer nylon, crosslinking agent and core layer nylon are respectively fed into the inlet mold 4, and the mass percentage of the three is 40~90%: 0.1~2%: 10~60%;

[0074] Preferably, the mass percentages of the outer nylon, crosslinking agent, and core nylon in step S3 are 50-80%: 0.5-1%: 15-20%.

[0075] Preferably, the crosslinking agent is 3-isocyanate-propyltriethoxysilane.

[0076] See Figure 2 The die 4 is provided with a core layer channel 41, an intermediate channel 42, and a skin layer channel 43; the die 4 is provided with a core layer feed pipe 411 connecting the core layer channel 41, an intermediate feed pipe 421 connecting the intermediate channel 42, and a skin layer feed pipe 431 connecting the skin layer channel 43; the skin layer nylon, crosslinking agent, and core layer nylon are respectively fed into the corresponding channels through the skin layer feed pipe 431, the intermediate feed pipe 421, and the core layer feed pipe 411;

[0077] The die 4 is also provided with a fusion cavity 44 that connects the discharge ports of each channel; the fusion cavity 44 is also connected to a plurality of spinnerets 45 provided on the die 4.

[0078] The temperature of the die 4 is 260°C; see also Figure 4 In die 4, the pore-forming agent decomposes to produce N2 and CO2 gases, which form a uniform closed-cell structure with a pore size of 1~10μm in situ in the core nylon.

[0079] The gas produced by the decomposition of the pore-forming agent naturally evaporates during the subsequent spinning process, leaving no residue. This invention utilizes the gas from the decomposition of the pore-forming agent to form a uniform closed-cell structure in the core nylon layer. By leveraging the low thermal conductivity of this closed-cell structure, the thermal conductivity of the nylon fiber is reduced, simultaneously decreasing the fiber weight and achieving lightweighting.

[0080] Combination Figure 8 The porosity of the closed-cell structure in the core nylon is 10~30%.

[0081] Within the fusion cavity 44, the crosslinking agent is sandwiched between the core nylon and the sheath nylon, and the following reaction occurs:

[0082] See Figure 5 The amide groups of the crosslinking agent undergo a covalent bonding reaction with the amide groups of the core layer nylon to generate silane-modified core layer nylon;

[0083] See Figure 6 The amide groups of the crosslinking agent undergo a covalent bonding reaction with the amide groups of the nylon skin layer to generate silane-modified nylon skin layer.

[0084] See Figure 7 Silane-modified core nylon and silane-modified skin nylon undergo hydrolysis and condensation reactions to generate nylon material with a skin-core nylon cross-linked structure;

[0085] The nylon material of the present invention has two functions: chemical bonding and low thermal conductivity network. It can firmly connect the core layer and the skin layer, and reduce the thermal conductivity of the nylon material, thereby improving its heat retention performance.

[0086] See Figure 3 In one embodiment, the core layer channel 41 has a circular cross-sectional shape and is located at the center of the die 4; the intermediate channel 42 and the skin layer channel 43 are both annular channels, and their central axes coincide with the central axis of the core layer channel 41. Within the fusion cavity 44, the skin layer nylon, crosslinking agent, and core layer nylon can be uniformly mixed.

[0087] As one embodiment, the crosslinking agent is stored in a crosslinking agent tank 3, which is connected to a feeding pump 31, which is connected to an inlet mold 4; preferably, the feeding pump 31 is a high-pressure pump that pumps the crosslinking agent into the inlet mold 4.

[0088] The skin feed pipe 431, intermediate feed pipe 421 and core feed pipe 411 of the die 4 are respectively connected to the skin extruder 1, the feed pump 31 and the core extruder 2.

[0089] S4, after the nylon material is drawn out through the spinneret 45, it is bundled and oiled by the oiling roller 5 to form nylon fiber bundles;

[0090] Optionally, in step S4, the oiling agent is a special antistatic oiling agent for nylon, with an oiling rate of 0.8%, which reduces the coefficient of friction and avoids damage to the fibers during subsequent stretching.

[0091] S5, the nylon fiber bundle is graded and stretched by multiple guide rollers 51, and then wound into shape to obtain the finished nylon fiber product.

[0092] In one implementation, the graded stretching in step S5 is a three-stage stretching with a stretching ratio of 3.0 times; during the stretching process, the crosslinking agent can fully react to form a nylon crosslinked structure with a thickness of 200~500nm between the core layer and the skin layer;

[0093] Optionally, the parameters for the three-stage tension are as follows:

[0094] First stage of stretching: The rotational speed of the guide roller 51 is 1200 m / min, and the temperature is 60℃;

[0095] Second-stage stretching: The rotational speed of the guide roller 51 is 2400 m / min, and the temperature is 120℃;

[0096] Third-stage stretching: The rotational speed of the guide roller 51 is 3600 m / min, and the temperature is 130℃;

[0097] In one embodiment, the winding speed of the winding forming in step S5 is 4000 m / min, and the winding tension is 20 cN.

[0098] To illustrate the technical effects in detail, this invention uses the aforementioned method, changing the parameters of certain steps, to prepare multiple example samples. Simultaneously, to facilitate comparison of technical effects, comparative samples were prepared using the same raw materials without adding core layer additives.

[0099] The thermal conductivity, tensile strength, and core porosity of the fiber samples in each embodiment and comparative example were tested. Specific experimental parameters and test results are shown in Table 1. (Note: Table 1 only lists the varied parameters; the same parts and steps can be found above and will not be repeated here.)

[0100] Comparing the data from the examples and comparative examples, it can be seen that the thermal conductivity of the samples in each example is significantly lower than that of the comparative example; and the breaking strength of each example is not significantly reduced compared to the comparative example sample. This indicates that the present invention effectively improves the thermal insulation performance of nylon fibers by forming a uniform closed-cell structure in the core layer through the decomposition of gas by the pore-forming agent, while also exhibiting good strength.

[0101] Although the thermal conductivity of the comparative sample is higher than that of the example samples, it is significantly lower than that of existing pure nylon. Furthermore, the comparative sample exhibits a relatively higher breaking strength compared to the example samples. This indicates that the skin-core nylon cross-linked structure formed between the skin and core layers in this invention possesses both chemical bonding and a low thermal conductivity network function, effectively connecting the core and skin layers while simultaneously reducing the thermal conductivity of the nylon material and improving its warmth retention performance.

[0102] Table 1. Parameters and test results for each embodiment and comparative example.

[0103] .

[0104] In summary, this invention provides a method for preparing porous nylon fibers. The method involves using gases from the decomposition of a pore-forming agent to form a uniform closed-cell structure within the core nylon layer; and using a crosslinking agent to form a core-sheath crosslinked structure with chemical bonding and a low thermal conductivity network between the core and sheath layers. This significantly reduces the thermal conductivity and weight of the nylon fiber while maintaining high strength, resulting in lightweight and warm nylon fibers.

[0105] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for preparing porous nylon fiber, characterized in that, Includes the following steps: S1, feed the skin material into the skin extruder; feed the core material and core auxiliary materials into the core extruder; Both the outer layer material and the core layer material are: spinning-grade nylon 6 chips; The amount of core layer auxiliary material added is 1-3% of the mass of the core layer raw material; The core layer auxiliary material includes fillers and porogens; the mass ratio of the filler to the porogen is 1~5:1; the porogen is azodicarbonamide; S2, the sheath material forms molten sheath nylon in the sheath extruder; the core material and core auxiliary materials form molten core nylon in the core extruder; S3, the outer layer nylon, crosslinking agent and core layer nylon are respectively fed into the mold, the mass percentage of the three is 40~90%:0.1~2%:10~60%; the crosslinking agent is 3-isocyanate-propyltriethoxysilane; The die is provided with a core layer channel, an intermediate channel and a skin layer channel; the die is provided with a core layer feed pipe that connects to the core layer channel, an intermediate feed pipe that connects to the intermediate channel and a skin layer feed pipe that connects to the skin layer channel; the skin layer nylon, crosslinking agent and core layer nylon are respectively fed into the corresponding channels through the skin layer feed pipe, the intermediate feed pipe and the core layer feed pipe. The die is also provided with a fusion cavity that connects the discharge ports of each channel; the fusion cavity is also connected to multiple spinnerets provided on the die. The temperature of the die is 260°C; in the die, the pore-forming agent decomposes to produce N2 and CO2 gases, which form a uniform closed-cell structure with a pore size of 1~10μm in situ in the core nylon. Within the fusion cavity, the crosslinking agent is sandwiched between the core nylon and the sheath nylon, and the following reaction occurs: The amide groups of the crosslinking agent undergo a covalent bonding reaction with the amide groups of the core layer nylon to generate silane-modified core layer nylon; The amide groups of the crosslinking agent undergo a covalent bonding reaction with the amide groups of the nylon skin to generate silane-modified nylon skin; Silane-modified core nylon and silane-modified skin nylon undergo hydrolysis and condensation reactions to generate nylon material with a skin-core nylon cross-linked structure; S4, after the nylon material is drawn out through the spinneret, it is bundled and oiled by the oiling roller to form nylon fiber bundles; S5, nylon fiber bundles are graded and stretched by multiple guide rollers, and then wound into finished nylon fiber products.

2. The method for preparing porous nylon fiber as described in claim 1, characterized in that, The viscosity of the nylon 6 chips in step S1 is 2.4 dl / g to 2.6 dl / g, and the water content is ≤0.05%.

3. The method for preparing porous nylon fiber as described in claim 1, characterized in that, The filler in step S1 is: modified silica aerogel powder; The modified silica aerogel powder has a particle size of 1~5μm, a porosity ≥95%, and a specific surface area of ​​600~1000m². 2 / g.

4. The method for preparing porous nylon fiber as described in claim 3, characterized in that, The preparation steps of the modified silica aerogel powder include: Z1, dry silica aerogel powder is dispersed in anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension; the mass ratio of silica aerogel powder to anhydrous ethanol is 1:

20. Z2, add 1% KH550 of the aerogel powder by mass, stir at 55℃ for 2 hours to obtain modified aerogel by grafting reaction. Z3, centrifugal separation process, to obtain modified aerogel solid; Z4 was washed three times with anhydrous ethanol; then vacuum dried at 60°C for 4 hours to obtain the modified silica aerogel powder.

5. The method for preparing porous nylon fiber as described in claim 1, characterized in that, The core layer material in step S1 is premixed before being added to the core layer extruder.

6. The method for preparing porous nylon fiber as described in claim 1, characterized in that, The screw speed of the extruder in step S2 is 200 rpm; the screw is divided into three temperature zones along the feeding direction; the screw temperatures of the three temperature zones are 210℃, 245℃ and 255℃ respectively; The screw speed of the core extruder is 100 rpm; along the feeding direction, the screw is divided into three temperature zones; the screw temperatures of the three temperature zones are 190℃, 230℃ and 240℃ respectively.

7. The method for preparing porous nylon fiber as described in claim 1, characterized in that, The mass percentages of the outer nylon, crosslinking agent, and core nylon in step S3 are 50-80%: 0.5-1%: 15-20%.

8. The method for preparing porous nylon fiber as described in claim 1, characterized in that, The graded stretching in step S5 is a three-stage stretching with a stretching ratio of 3.0 times; the parameters for the three-stage stretching are as follows: First stage of stretching: The guide roller rotates at 1200 m / min and the temperature is 60℃; Second stage stretching: The guide roller rotates at 2400 m / min and the temperature is 120℃; Third-stage stretching: The guide roller rotates at 3600 m / min and the temperature is 130℃.

9. The method for preparing porous nylon fiber as described in claim 1, characterized in that, The winding speed in step S5 is 4000 m / min, and the winding tension is 20 cN.

10. The method for preparing porous nylon fiber according to any one of claims 1 to 9, characterized in that, The crosslinking agent is stored in a crosslinking agent tank, which is connected to a feeding pump, which is connected to a die; the feeding pump is a high-pressure pump. The outer layer feed pipe, middle feed pipe, and core layer feed pipe of the die are respectively connected to the outer layer extruder, the feeding pump, and the core layer extruder.

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