Process for the preparation of a melt-spun far infrared polyamide fiber

Abstract

This invention relates to the technical field of functional fibers and discloses a method for preparing melt-spun far-infrared polyamide fibers, comprising the following steps: (1) coating SiO2 onto the surface of zinc-aluminum hydrotalcite using a sol-gel method, followed by calcination to obtain far-infrared powder; (2) modifying the surface of the far-infrared powder with a surface modifier to obtain modified far-infrared powder; (3) dispersing the modified far-infrared powder with a caprolactam solution, then mixing the mixture with water and a capping agent to perform a ring-opening reaction; (4) performing a polycondensation reaction while removing small molecules, and then directly conveying the melt to a spinning line for spinning to obtain far-infrared polyamide fibers. This invention coats the surface of hydrotalcite with SiO2, which broadens the far-infrared absorption range and improves the far-infrared emissivity of the fiber; and the in-situ polymerization method greatly improves the dispersibility of the modified far-infrared powder, thereby enhancing the spinning stability.

Description

Technical Field

[0001] This invention relates to the technical field of functional fibers, and in particular to a method for preparing melt-spun far-infrared polyamide fibers. Background Technology

[0002] Polyamide is a high-strength material used in fibers and engineering plastics. Polyamide fiber (nylon) is a high-performance synthetic fiber with excellent skin-friendliness, strength, and abrasion resistance, and is therefore widely used in civilian fibers and industrial fabrics. With economic development and improved living standards, the demands for textiles are increasingly focused on functionality and aesthetics. Traditional cold-weather clothing is mostly bulky and heavy, lacking in both aesthetics and comfort; therefore, developing highly efficient and warm textiles has a broad market prospect.

[0003] For example, Chinese patent CN102776600A discloses a method for preparing high-efficiency infrared polyamide fibers. This method uses a co-precipitation method to prepare magnesium aluminum hydrotalcite, which is then calcined to obtain a bimetallic oxide (MMO). 2% MMO is blended and granulated with polyamide chips, and then melt-spun to obtain far-infrared polyamide fibers. The hydrotalcite prepared by the co-precipitation method has a relatively large particle size, which will affect the mechanical properties of the fibers. This patent introduces far-infrared powder using a blending method, but blending results in poor dispersion of the far-infrared powder in the polyamide matrix, leading to unstable spinning and decreased performance. Chinese patent CN115385573A discloses a method for preparing graphene nylon fibers. This method mixes organically modified graphene with nylon chips to obtain graphene nylon chips, which are then melt-spun to obtain graphene nylon fibers, thus giving the nylon fibers far-infrared properties. However, graphene itself is black, which will affect or limit the dyeing effect of the functional fibers, making it difficult to obtain pure white and brightly colored textiles. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing melt-spun far-infrared polyamide fibers. The method utilizes hydrothermal preparation of hydrotalcite, resulting in smaller particle sizes and reduced fiber breakage. Coating the surface of the hydrotalcite with SiO2 broadens the far-infrared absorption range and increases the far-infrared emissivity of the fiber. Unlike blending methods, this invention employs an in-situ polymerization process for direct addition, resulting in a more uniform distribution of far-infrared functional powders in the melt, achieving the desired effect with a smaller addition amount. Furthermore, traditional polyamide fibers are produced using an intermittent spinning process involving polymerization, pelletizing, extraction, drying, and melt blending. The heating processes during melt pelletizing and remelting involve reverse reactions, generating new small molecules that alter the molecular weight distribution and reduce spinnability. Moreover, the extraction and drying processes consume significant energy, increasing the production cost of polyamide fibers. This invention utilizes a melt-spun process for polyamide fibers, resulting in more stable melt quality, more uniform dispersion of far-infrared functional powders, and superior performance of the resulting functional fibers. Simultaneously, it significantly simplifies the production process and further reduces fiber production costs.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention provides a method for preparing melt-spun far-infrared polyamide fibers, comprising the following steps:

[0007] (1) SiO2 was coated on the surface of zinc-aluminum hydrotalcite by sol-gel method and then calcined to obtain far-infrared powder;

[0008] (2) The surface of the far-infrared powder was modified by using a surface modifier to obtain modified far-infrared powder;

[0009] (3) Mix and disperse the modified far-infrared powder with caprolactam solution, then mix the mixture with water and end-capping agent to carry out ring-opening reaction;

[0010] (4) A polycondensation reaction is carried out, and small molecules are removed at the same time. The melt after removal is directly transported to the spinning line for spinning to obtain far-infrared polyamide fiber.

[0011] This invention employs a hydrothermal synthesis method to prepare zinc-aluminum hydrotalcite. By controlling the hydrothermal temperature and pH value, the particle size is controlled to the nanoscale, avoiding fiber breakage or spinneret blockage caused by excessively large particle sizes. SiO2 is uniformly coated onto the surface of the zinc-aluminum hydrotalcite using a sol-gel method, and after calcination, far-infrared powder exhibiting stronger absorption characteristics in the far-infrared region is obtained. Subsequently, the powder undergoes surface organic modification and is dispersed in molten caprolactam via in-situ polymerization. After high-speed mechanical stirring, water and a capping agent are added to initiate ring-opening and polycondensation reactions. After removing small molecules, a melt suitable for direct spinning is obtained. The melt is then fed to a spinning mill to obtain far-infrared polyamide fibers. This method achieves a synergistic effect in the infrared absorption band through chemical coating, while ensuring the spinnability and functionality of the fibers.

[0012] Far-infrared radiation primarily releases heat through radiation, with wavelengths ranging from 4 to 25 μm, and the strongest radiant energy occurring near a wavelength of 9 μm. SiO2 exhibits a high absorption peak at 9 μm, falling within the range of wavelengths most strongly absorbed by the human body. Furthermore, SiO2 is nearly transparent in the visible light range, making it suitable for preparing far-infrared textiles. The calcined zinc-aluminum hydrotalcite (ZALH) material shows significant far-infrared absorption peaks in the 6.5–25 μm range, while SiO2 has a strong absorption peak at 9 μm. Simple blending is insufficient to efficiently broaden the absorption range. The sol-gel method, which coats SiO2 onto the surface of ZALH, achieves interfacial coupling between the two phases, superimposing absorption bands, thereby broadening the far-infrared absorption range and increasing the far-infrared emissivity of the fibers.

[0013] Preferably, the zinc-aluminum hydrotalcite is prepared by hydrothermal synthesis.

[0014] Preferably, the preparation of the zinc-aluminum hydrotalcite includes the following steps: stirring a ZnCl2 solution, and sequentially adding Al(NO3)3·9H2O solution, Na2CO3 solution, and NaOH solution, wherein the pH of the mixture is 9-14; and subjecting the mixture to a hydrothermal synthesis reaction to obtain zinc-aluminum hydrotalcite.

[0015] Preferably, the amount of ZnCl2 solution and Al(NO3)3·9H2O solution added is such that the zinc-aluminum molar ratio is 2-4:1; the hydrothermal synthesis reaction is carried out by hydrothermal crystallization at 100-200℃ for 3-10 hours.

[0016] As a preferred embodiment, step (1) specifically includes the following steps: mixing anhydrous ethanol and water, dispersing zinc-aluminum hydrotalcite in the mixture, adjusting the pH to 7-12 to obtain an ethanol-water-zinc-aluminum hydrotalcite mixture, adding tetraethyl orthosilicate dropwise to the mixture under stirring at 30-60°C, stirring until a gel is formed, and then drying and calcining under vacuum to obtain far-infrared powder.

[0017] Preferably, the volume ratio of anhydrous ethanol to water is 2-5:1; the mass ratio of the ethanol-water mixture to zinc-aluminum hydrotalcite is 10-50:1; the zinc-aluminum molar ratio of the zinc-aluminum hydrotalcite is 2-4:1; and the amount of tetraethyl orthosilicate added is such that the molar ratio of SiO2 to zinc-aluminum hydrotalcite in the ethanol-water-zinc-aluminum hydrotalcite mixture is 2-4:1.

[0018] Preferably, the vacuum drying is performed at 50–100°C for 8–12 hours; the calcination is performed at 300–1000°C for 2–7 hours.

[0019] Calcination causes zinc-aluminum hydrotalcite to lose interlayer water, and SiO2 particles form nanocrystals.

[0020] Preferably, step (2) specifically includes the following steps: adding far-infrared powder to an organic solvent and stirring to obtain a dispersion; stirring the dispersion and refluxing, adding a surface modifier and continuing to stir, and after the reaction is completed, post-treatment is performed to obtain modified far-infrared powder.

[0021] Preferably, the surface modifier is a silane coupling agent; the amount of the surface modifier added is 1-5 wt% of the infrared powder; the temperature of the stirring and reflux is 23-90°C, and the stirring time is 1-5 h.

[0022] Preferably, in step (3), the amount of modified far-infrared powder added is 1-5 wt% of caprolactam, more preferably, the amount of modified far-infrared powder added is 3-5 wt% of caprolactam; the amount of water added is 1-5 wt% relative to caprolactam, and the amount of capping agent added is 0.1-0.5 wt%.

[0023] Preferably, in step (3), the copolymer component is added together with water and the capping agent and mixed with the mixture to carry out the ring-opening reaction; the amount of copolymer component added relative to caprolactam is 15-30 wt%; more preferably, the amount of copolymer component added is 15-25 wt%.

[0024] Preferably, in step (3), the copolymer component is one or more selected from polyamide salt, caprolactone, polycaprolactone, and polyester. The polyamide salt is -CO(CH2). a CONH(CH2) b NH- or NH2(CH2) y COOH, where a ranges from 0 to 10, b ranges from 1 to 10, and y ranges from 4 to 12.

[0025] Preferably, in step (3), the capping agent is one or more of adipic acid, acetic acid, terephthalic acid and phthalic acid.

[0026] Preferably, in step (3), the temperature of the ring-opening reaction is 210-250°C and the reaction pressure is controlled at 0.5-2.5 MPa; the reaction is terminated when the following conditions are met: the number average molecular weight of the obtained melt is 5000-30000.

[0027] Preferably, in step (4), the temperature of the polycondensation reaction is 210-270°C, and the reaction pressure is controlled at -0.1-3 MPa. The reaction is terminated when the following conditions are met: the number average molecular weight of the obtained product is 15,000-50,000, the extractable content is <4%, and the relative viscosity of the melt is 2.0-4.0.

[0028] Preferably, in step (4), the spinning temperature is 230–270°C.

[0029] Preferably, in step (4), the spun yarn is subjected to side blowing, with the side blowing temperature being 20-30℃, the air humidity being 60-80%, and the wind speed being 0.3-0.7m / s.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The hydrotalcite prepared by the hydrothermal method in this invention has a small particle size, which avoids fiber breakage or spinneret blockage caused by excessive particle size; coating SiO2 on the surface of the hydrotalcite will broaden the far-infrared absorption range and improve the far-infrared emissivity of the fiber.

[0032] (2) The present invention uses in-situ polymerization to introduce modified far-infrared powder into the polymerization system, which greatly improves its dispersibility in the polyamide matrix, improves spinning stability, and makes it durable and washable.

[0033] (3) Most traditional far-infrared powders are dark in color, which will affect the dyeing effect of fibers. The functional powder of this invention is white and will not affect the dyeing effect of functional fibers.

[0034] (4) The present invention adopts the polyamide melt direct spinning process. The modified melt can be directly spun to ensure the relative stability of the polymer molecular weight, thereby improving the spinnability and reducing the production cost of the fiber. Detailed Implementation

[0035] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0036] The preparation of melt-spun far-infrared polyamide fibers in this invention includes the following steps:

[0037] (1) Preparation of zinc-aluminum hydrotalcite: ZnCl2 solution was stirred, and Al(NO3)3·9H2O solution, Na2CO3 solution and NaOH solution were added dropwise in sequence. The pH of the mixed solution was 9-14 and the molar ratio of zinc to aluminum was 2-4:1. After stirring the above solution for 0.5-3h, hydrothermal synthesis reaction was carried out. Crystallization was carried out at 100-200℃ for 3-10h. After the hydrothermal reaction was completed, the solution was washed three times, filtered, dried and ground to obtain zinc-aluminum hydrotalcite.

[0038] (2) Preparation of far-infrared powder: Anhydrous ethanol and deionized water were mixed at a volume ratio of 2–5:1, with zinc-aluminum hydrotalcite dispersed in the mixture. The pH was adjusted to 7–12, and the mass ratio of the ethanol-water mixture to zinc-aluminum hydrotalcite was 10–50:1, resulting in an ethanol-water-zinc-aluminum hydrotalcite mixture. Tetraethyl orthosilicate (TEOS) was slowly added dropwise to the ethanol-water-zinc-aluminum hydrotalcite mixture under stirring at 30–60°C, so that the molar ratio of SiO2 to zinc-aluminum hydrotalcite was 2–4:1. The mixture was stirred until it reached a gel state. The wet gel was vacuum dried at 50–100°C for 8–12 h, and then calcined at 300–1000°C for 2–7 h to obtain far-infrared powder.

[0039] (3) Preparation of modified far-infrared powder: The far-infrared powder is placed in an isopropanol solution and stirred for 0.5 to 2 hours to obtain a dispersion; the dispersion is stirred and refluxed at 23 to 90°C, and 0.1 to 6 wt% of surface modifier relative to the far-infrared powder is added. After stirring for 1 to 5 hours, the mixture is cooled to room temperature to obtain a suspension; the suspension is filtered, washed, and dried at 50 to 80°C for 8 to 12 hours to obtain modified far-infrared powder.

[0040] (4) Ring-opening: The modified far-infrared powder is mixed with caprolactam solution in a mixing tank. The amount of far-infrared powder added is 1-5 wt% relative to caprolactam. The mixture is sheared and stirred for 0.5-2 h to ensure uniform dispersion of the powder in the caprolactam solution. Then, 15-30 wt% of copolymer component (selective addition), 1-5 wt% of water, and 0.1-0.5 wt% of end-capping agent are added relative to caprolactam. The mixing temperature is 80-140℃, and the mixture is stirred for 10-60 min. The resulting mixture is heated to carry out a ring-opening reaction at a temperature of 210-250℃ and a reaction pressure controlled at 0.5-2.5 MPa. The reaction is then terminated. The number average molecular weight of the obtained melt is 5000-30000.

[0041] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 210-270℃, the reaction pressure is controlled at -0.1-3MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 15000-50000, the extractable content is <4%, and the relative viscosity of the melt is 2.0-4.0.

[0042] (6) Spinning: The melt after removal is directly conveyed to the spinning box for spinning. The spinning temperature is 230-270℃, the side blowing air temperature is 20-30℃, the air humidity is 60-80%, and the wind speed is 0.3-0.7m / s to obtain far-infrared polyamide fiber.

[0043] In a specific embodiment of the present invention, the surface modifier is a silane coupling agent.

[0044] In a specific embodiment of the present invention, the copolymer component is one or more of a polyamide salt, caprolactone and / or its polymer, and a polyester condensate. The polyamide salt is -CO(CH2). a CONH(CH2) b NH- or NH2(CH2) y COOH, where a ranges from 0 to 10, b ranges from 1 to 10, and y ranges from 4 to 12.

[0045] In a specific embodiment of the present invention, the capping agent is one or more of adipic acid, acetic acid, terephthalic acid, and phthalic acid.

[0046] Example 1

[0047] (1) Preparation of zinc-aluminum hydrotalcite: ZnCl2 solution was stirred, and Al(NO3)3·9H2O solution, Na2CO3 solution and NaOH solution were added dropwise in sequence. The pH of the mixed solution was 12 and the molar ratio of zinc to aluminum was 2:1. After stirring the above solution for 0.5 h, hydrothermal synthesis reaction was carried out. Crystallization was carried out at 160℃ for 6 h. After the hydrothermal reaction was completed, the solution was washed three times, filtered, dried and ground to obtain zinc-aluminum hydrotalcite.

[0048] (2) Preparation of far-infrared powder: Anhydrous ethanol and deionized water were mixed at a volume ratio of 4:1, with zinc-aluminum hydrotalcite dispersed in the mixture. The mass ratio of the ethanol-water mixture to the zinc-aluminum hydrotalcite was 16.5:1. The pH was adjusted to 9 to obtain an ethanol-water-zinc-aluminum hydrotalcite mixture. TEOS was slowly added dropwise under stirring at 35°C to achieve a SiO2 to zinc-aluminum hydrotalcite molar ratio of 2:1, and the mixture was stirred until it reached a gel state. The wet gel was vacuum dried at 80°C for 12 hours and then calcined at 700°C for 4 hours to obtain far-infrared powder.

[0049] (3) Preparation of modified far-infrared powder: The far-infrared powder was placed in an isopropanol solution and stirred for 0.5 h to obtain a dispersion; the dispersion was stirred and refluxed at 35 °C, and 3 wt% of aminosilane coupling agent (KH550) relative to the far-infrared powder was added. After stirring for 1 h, the mixture was cooled to room temperature to obtain a suspension; the suspension was filtered, washed, and dried at 80 °C for 8 h to obtain the modified far-infrared powder.

[0050] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 1 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 15 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid were added relative to caprolactam. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number-average molecular weight of the obtained melt was 19280.

[0051] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 32360, the extractable content is <4%, and the relative viscosity of the melt is 2.18.

[0052] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0053] Example 2

[0054] The difference from Example 1 is that the amount of modified far-infrared powder added is 3 wt% relative to caprolactam.

[0055] Steps (1)-(3) are the same as in Example 1.

[0056] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 3 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 15 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid were added relative to caprolactam. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number average molecular weight of the obtained melt was 19000.

[0057] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 33652, the extractable content is <4%, and the relative viscosity of the melt is 2.20.

[0058] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0059] Example 3

[0060] The difference from Example 1 is that the amount of modified far-infrared powder added is 5 wt% relative to caprolactam.

[0061] Steps (1)-(3) are the same as in Example 1.

[0062] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 5 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 15 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid were added relative to caprolactam. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C and the reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number-average molecular weight of the obtained melt was 19576.

[0063] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 37520, the extractable content is <4%, and the relative viscosity of the melt is 2.5.

[0064] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0065] Example 4

[0066] The difference from Example 2 is that the amount of polyamide 66 salt added is 30 wt% relative to caprolactam.

[0067] Steps (1)-(3) are the same as in Example 1.

[0068] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 3 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 30 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid were added relative to caprolactam. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number-average molecular weight of the obtained melt was 19352.

[0069] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 32872, the extractable content is <4%, and the relative viscosity of the melt is 2.2.

[0070] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0071] Example 5

[0072] The difference from Example 2 is that polyamide 66 salt is not added.

[0073] Steps (1)-(3) are the same as in Example 1.

[0074] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 3 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 2.5 wt% water and 0.3 wt% terephthalic acid relative to caprolactam were added. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number-average molecular weight of the obtained melt was 19765.

[0075] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 35420, the extractable content is <4%, and the relative viscosity of the melt is 2.4.

[0076] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0077] Example 6

[0078] The difference from Example 2 is that the zinc-aluminum molar ratio is 4:1, and polyamide 66 salt is not added.

[0079] (1) Preparation of zinc-aluminum hydrotalcite: ZnCl2 solution was stirred, and Al(NO3)3·9H2O solution, Na2CO3 solution and NaOH solution were added dropwise in sequence. The pH of the mixed solution was 12 and the molar ratio of zinc to aluminum was 4:1. After stirring the above solution for 0.5 h, hydrothermal synthesis reaction was carried out. Crystallization was carried out at 160℃ for 6 h. After the hydrothermal reaction was completed, the solution was washed three times, filtered, dried and ground to obtain zinc-aluminum hydrotalcite.

[0080] (2) Preparation of far-infrared powder: Anhydrous ethanol and deionized water were mixed at a volume ratio of 4:1, with zinc-aluminum hydrotalcite dispersed in the mixture. The mass ratio of the ethanol-water mixture to the zinc-aluminum hydrotalcite was 16.5:1. The pH was adjusted to 9 to obtain an ethanol-water-zinc-aluminum hydrotalcite mixture. TEOS was slowly added dropwise under stirring at 35°C to achieve a SiO2 to zinc-aluminum hydrotalcite molar ratio of 2:1, and the mixture was stirred until it reached a gel state. The wet gel was vacuum dried at 80°C for 12 hours and then calcined at 700°C for 4 hours to obtain far-infrared powder.

[0081] (3) Preparation of modified far-infrared powder: The far-infrared powder was placed in an isopropanol solution and stirred for 0.5 h to obtain a dispersion; the dispersion was stirred and refluxed at 35 °C, and 3 wt% of aminosilane coupling agent (KH550) relative to the far-infrared powder was added. After stirring for 1 h, the mixture was cooled to room temperature to obtain a suspension; the suspension was filtered, washed, and dried at 80 °C for 8 h to obtain the modified far-infrared powder.

[0082] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 3 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 2.5 wt% water and 0.3 wt% terephthalic acid relative to caprolactam were added. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number-average molecular weight of the obtained melt was 19357.

[0083] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 34780, the extractable content is <4%, and the relative viscosity of the melt is 2.3.

[0084] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0085] Comparative Example 1

[0086] The difference from Example 1 is that no modified far-infrared powder is added.

[0087] (1) Ring-opening: The caprolactam solution was added to the mixing tank, followed by 15 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid relative to the caprolactam. The mixing temperature was 120°C, and the mixture was stirred for 60 min. The resulting mixture was then heated to carry out a ring-opening reaction at 220°C. The reaction pressure was controlled at 1.2 MPa, and the reaction was terminated. The number-average molecular weight of the obtained melt was 19274.

[0088] (2) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 32873, the extractable content is <4%, and the relative viscosity of the melt is 2.2.

[0089] (3) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain polyamide fiber.

[0090] Comparative Example 2

[0091] The difference from Example 2 is that unmodified far-infrared powder is added.

[0092] Steps (1)-(2) are the same as in Example 1.

[0093] (3) Ring-opening: The far-infrared powder and caprolactam solution were mixed in a mixing tank. The amount of far-infrared powder added was 3 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 15 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid were added relative to caprolactam. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number-average molecular weight of the obtained melt was 19783.

[0094] (4) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 34760, the extractable content is <4%, and the relative viscosity of the melt is 2.3.

[0095] (5) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0096] Comparative Example 3

[0097] The difference from Example 1 is that no modified far-infrared powder and polyamide 66 salt are added.

[0098] (1) Ring-opening: The caprolactam solution was added to the mixing tank, followed by 2.5 wt% water and 0.3 wt% terephthalic acid relative to the caprolactam. The mixing temperature was 120°C, and the mixture was stirred for 60 min. The resulting mixture was then heated to carry out the ring-opening reaction at 220°C. The reaction pressure was controlled at 1.2 MPa, and the reaction was terminated. The number-average molecular weight of the obtained melt was 18923.

[0099] (2) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 36752, the extractable content is <4%, and the relative viscosity of the melt is 2.4.

[0100] (3) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain polyamide fiber.

[0101] Comparative Example 4

[0102] The difference from Example 2 is that small molecules are not removed during the polycondensation reaction.

[0103] Steps (1)-(3) are the same as in Example 1.

[0104] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 3 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 15 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid were added relative to caprolactam. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number-average molecular weight of the obtained melt was 19826.

[0105] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, and the reaction is terminated without removing small molecules. The number average molecular weight of the obtained product is 31872, the extractable content is >9%, and the relative viscosity of the melt is 2.1.

[0106] (6) Spinning: The melt is directly conveyed to the spinning box for spinning. The spinning temperature is 260℃, the side blowing temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0107] Comparative Example 5

[0108] The difference from Example 2 is that the far-infrared powder contains only zinc aluminum hydrotalcite.

[0109] (1) Preparation of zinc-aluminum hydrotalcite: ZnCl2 solution was stirred, and Al(NO3)3·9H2O solution, Na2CO3 solution and NaOH solution were added dropwise in sequence. The pH of the mixed solution was 12 and the molar ratio of zinc to aluminum was 2:1. After stirring the above solution for 0.5 h, hydrothermal synthesis reaction was carried out. Crystallization was carried out at 160℃ for 6 h. After the hydrothermal reaction was completed, the solution was washed three times, filtered, dried and ground to obtain zinc-aluminum hydrotalcite.

[0110] (2) Preparation of far-infrared powder: The obtained zinc-aluminum hydrotalcite was calcined at 700℃ and kept at that temperature for 4 hours.

[0111] (3) Modified far-infrared powder: The far-infrared powder was placed in an isopropanol solution and stirred for 0.5 h to obtain a dispersion; the dispersion was stirred and refluxed at 35 °C, and 3 wt% of aminosilane coupling agent (KH550) was added. After stirring for 1 h, it was cooled to room temperature to obtain a suspension; the suspension was filtered, washed, and dried at 80 °C for 8 h to obtain the modified far-infrared powder.

[0112] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank at an addition amount of 3 wt% of caprolactam, and the mixture was sheared and stirred for 0.5 h. Then, 15 wt% of polyamide 66 salt, 2.5 wt% of water, and 0.3 wt% of terephthalic acid were added, and the mixing temperature was 120 °C. The mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at a ring-opening temperature of 220 °C and a reaction pressure controlled at 1.2 MPa. The reaction was then terminated, and the number-average molecular weight of the obtained melt was 19373.

[0113] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, and the reaction is terminated without removing small molecules. The number average molecular weight of the obtained product is 34172, the extractable content is <4%, and the relative viscosity of the melt is 2.2.

[0114] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0115] Comparative Example 6

[0116] The difference from Example 2 is that the far-infrared powder contains only SiO2.

[0117] Preparation of far-infrared powder: Anhydrous ethanol and deionized water were mixed at a volume ratio of 4:1, and the pH was adjusted to 9 to obtain an ethanol-water mixture. TEOS was slowly added dropwise to the ethanol-water mixture under stirring at 35°C until a gel was formed. The wet gel was vacuum dried at 80°C for 12 hours, then calcined at 700°C for 4 hours to obtain SiO2 powder.

[0118] (2) Preparation of modified far-infrared powder: SiO2 powder was placed in isopropanol solution and stirred for 0.5 h to obtain a dispersion; the dispersion was stirred and refluxed at 35 °C, and 3 wt% of aminosilane coupling agent (KH550) relative to SiO2 powder was added. After stirring for 1 h, it was cooled to room temperature to obtain a suspension; the suspension was filtered, washed, and dried at 80 °C for 8 h to obtain modified far-infrared powder.

[0119] (3) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 3 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 15 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid were added relative to caprolactam. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number average molecular weight of the obtained melt was 19532.

[0120] (4) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 33782, the extractable content is <4%, and the relative viscosity of the melt is 2.2.

[0121] (5) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0122] Comparative Example 7

[0123] The difference from Example 2 is that the far-infrared powder is a blend of zinc-aluminum hydrotalcite and SiO2.

[0124] (1) Preparation of zinc-aluminum hydrotalcite: ZnCl2 solution was stirred, and Al(NO3)3·9H2O solution, Na2CO3 solution and NaOH solution were added dropwise in sequence. The pH of the mixed solution was 12 and the molar ratio of zinc to aluminum was 2:1. After stirring the above solution for 0.5 h, hydrothermal synthesis reaction was carried out. Crystallization was carried out at 160℃ for 6 h. After the hydrothermal reaction was completed, the solution was washed three times, filtered, dried and ground to obtain zinc-aluminum hydrotalcite. Then it was calcined at 700℃ and kept at the temperature for 4 h.

[0125] (3) Preparation of silica powder: Anhydrous ethanol and deionized water were mixed at a volume ratio of 4:1 and the pH was adjusted to 9 to obtain an ethanol-water mixture. TEOS was slowly added dropwise to the ethanol-water mixture under stirring at 35°C until it reached a gel state. The wet gel was vacuum dried at 80°C for 12 hours and then calcined at 700°C for 4 hours to obtain SiO2 powder.

[0126] (3) Modified far-infrared powder: Zinc-aluminum hydrotalcite and SiO2 powder were placed in isopropanol solution, with the mass ratio of SiO2 to zinc-aluminum hydrotalcite being 2:1. After stirring for 0.5 h, a dispersion was obtained. The dispersion was stirred and refluxed at 35 °C, and 3 wt% of aminosilane coupling agent (KH550) was added. After stirring for 1 h, the mixture was cooled to room temperature to obtain a suspension. The suspension was filtered, washed, and dried at 80 °C for 8 h to obtain the modified far-infrared powder.

[0127] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank at an addition amount of 3 wt% of caprolactam, and the mixture was sheared and stirred for 0.5 h. Then, 15 wt% of polyamide 66 salt, 2.5 wt% of water, and 0.3 wt% of terephthalic acid were added, and the mixing temperature was 120 °C. The mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at a ring-opening temperature of 220 °C and a reaction pressure controlled at 1.2 MPa. The reaction was then terminated, and the number-average molecular weight of the obtained melt was 19620.

[0128] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 32524, the extractable content is <4%, and the relative viscosity of the melt is 2.2.

[0129] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0130] Comparative Example 8

[0131] The difference from Example 2 is that the far-infrared powder has too much SiO2 coating.

[0132] (1) Preparation of zinc-aluminum hydrotalcite: ZnCl2 solution was stirred, and Al(NO3)3·9H2O solution, Na2CO3 solution and NaOH solution were added dropwise in sequence. The pH of the mixed solution was 12 and the molar ratio of zinc to aluminum was 2:1. After stirring the above solution for 0.5 h, hydrothermal synthesis reaction was carried out. Crystallization was carried out at 160℃ for 6 h. After the hydrothermal reaction was completed, the solution was washed three times, filtered, dried and ground to obtain zinc-aluminum hydrotalcite.

[0133] (2) Preparation of far-infrared powder: Anhydrous ethanol and deionized water were mixed at a volume ratio of 4:1, with zinc-aluminum hydrotalcite dispersed in the mixture. The mass ratio of the ethanol-water mixture to zinc-aluminum hydrotalcite was 16.5:1. The pH was adjusted to 9 to obtain an ethanol-water-zinc-aluminum hydrotalcite mixture. TEOS was slowly added dropwise under stirring at 35°C to achieve a SiO2 to zinc-aluminum hydrotalcite molar ratio of 5:1, and the mixture was stirred until it reached a gel state. The wet gel was vacuum dried at 80°C for 12 hours and then calcined at 700°C for 4 hours to obtain far-infrared powder.

[0134] (3) Preparation of modified far-infrared powder: The far-infrared powder was placed in an isopropanol solution and stirred for 0.5 h to obtain a dispersion; the dispersion was stirred and refluxed at 35 °C, and 3 wt% of aminosilane coupling agent (KH550) relative to the far-infrared powder was added. After stirring for 1 h, the mixture was cooled to room temperature to obtain a suspension; the suspension was filtered, washed, and dried at 80 °C for 8 h to obtain the modified far-infrared powder.

[0135] (4) Ring-opening: The modified far-infrared powder was mixed with caprolactam solution in a mixing tank. The amount of modified far-infrared powder added was 3 wt% relative to caprolactam. The mixture was sheared and stirred for 0.5 h. Then, 15 wt% polyamide 66 salt, 2.5 wt% water, and 0.3 wt% terephthalic acid were added relative to caprolactam. The mixing temperature was 120 °C, and the mixture was stirred for 60 min. The resulting mixture was heated to carry out a ring-opening reaction at 220 °C. The reaction pressure was controlled at 1.2 MPa. The reaction was then terminated. The number average molecular weight of the obtained melt was 19672.

[0136] (5) Polycondensation: The ring-opening mixture is fed into a polycondensation reactor to carry out the polycondensation reaction. The polycondensation temperature is 230℃, the reaction pressure is controlled at 1.2MPa, the small molecules are removed under negative pressure, and the reaction is terminated. The number average molecular weight of the obtained product is 36937, the extractable content is <4%, and the relative viscosity of the melt is 2.3.

[0137] (6) Spinning: The melt after removal is directly transported to the spinning box for spinning. The spinning temperature is 260℃, the side blowing air temperature is 30℃, the air humidity is 60%, and the wind speed is 0.7m / s to obtain far-infrared polyamide fiber.

[0138] Table 1

[0139]

[0140] As shown in Table 1, the polyamide fibers prepared by in-situ polymerization with added far-infrared powder exhibit excellent far-infrared properties. Examples 1-3 show that adding more far-infrared powder results in better far-infrared performance of the polyamide fibers; however, excessive addition of far-infrared powder is detrimental to the mechanical properties of the polyamide fibers. Examples 2, 4, and 5 show that adding the copolymer component (polyamide 66 salt) reduces crystallinity, leading to decreased strength, but increases elongation at break, making the fibers softer. Furthermore, adding excessive copolymer component (polyamide 66 salt) not only significantly reduces strength but also affects far-infrared performance. Examples 2, 5, and 6 show that a higher zinc-aluminum molar ratio, i.e., a higher molar proportion of zinc, results in larger particle sizes of the hydrotalcite, which reduces far-infrared emissivity and mechanical properties.

[0141] Comparative Examples 1 and 3 show that without the addition of far-infrared powder, the far-infrared emissivity of the fibers is low, and the related textiles cannot provide warmth. Comparative Example 2 shows that without surface modification of the far-infrared powder, the interfacial forces between the far-infrared powder and polyamide phases weaken, resulting in poor compatibility and dispersibility in the polyamide matrix. Therefore, the far-infrared and mechanical properties of the polyamide fibers are also affected. Comparative Example 4 shows that the polyamide melt, without the removal of small molecules, has a high extractable content, making spinning impossible. Comparative Examples 5-8 show that the far-infrared emissivity of materials containing only zinc-aluminum hydrotalcite or SiO2 powder is lower than that of far-infrared powder with SiO2 coated on zinc-aluminum hydrotalcite. Furthermore, the simple physical blending of zinc-aluminum hydrotalcite and SiO2 leads to weak interfacial bonding, resulting in absorption peaks that are only independently superimposed rather than synergistically broadened. Therefore, the far-infrared performance of the polyamide fibers remains low. Excessive SiO2 coating on the surface of zinc-aluminum hydrotalcite will result in only reflecting the infrared absorption peak of SiO2, thus degrading the far-infrared performance of polyamide fibers.

[0142] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A process for the preparation of melt-spun far infrared polyamide fibers, characterized in that, The method comprises the following steps: (1) coating SiO2 on the surface of zinc-aluminum hydrotalcite by sol-gel method, wherein the molar ratio of zinc to aluminum of the zinc-aluminum hydrotalcite is 2-4:1, and the molar ratio of SiO2 to the zinc-aluminum hydrotalcite is 2-4:1, and then calcining to obtain far-infrared powder; (2) modifying the far-infrared powder by using a surface modifier KH550 to obtain modified far-infrared powder; (3) mixing and dispersing the modified far-infrared powder with a caprolactam solution, and then mixing the mixture with water and a capping agent to perform ring-opening reaction; (4) performing polycondensation reaction while removing small molecules, and directly conveying the melt to a spinning line for spinning to obtain far-infrared polyamide fiber.

2. The process for the preparation of melt-spun far infrared polyamide fibers according to claim 1, characterized in that, Step (1) specifically comprises the following steps: mixing anhydrous ethanol and water, dispersing zinc-aluminum hydrotalcite in the mixture, adjusting the pH to 7-12, and then adding tetraethyl orthosilicate dropwise under stirring at 30-60℃ until a gel is formed, and then vacuum drying, calcining to obtain far-infrared powder.

3. The process for the preparation of melt-spun far infrared polyamide fibers according to claim 2, characterized in that, The volume ratio of the anhydrous ethanol to water is 2-5:1; the mass ratio of the obtained ethanol-water mixture to the zinc-aluminum hydrotalcite is 10-50:1; and the amount of the added tetraethyl orthosilicate is such that the molar ratio of SiO2 to the zinc-aluminum hydrotalcite in the ethanol-water-zinc-aluminum hydrotalcite mixture is 2-4:

1.

4. The process for the preparation of melt-spun far infrared polyamide fibers according to claim 2 or 3, characterized in that, The vacuum drying is performed at 50-100℃ for 8-12h, and the calcining is performed at 300-1000℃ for 2-7h.

5. The process for the preparation of melt-spun far infrared polyamide fibers according to claim 1, characterized in that, In step (2), the amount of the added surface modifier is 1-5wt% of the far-infrared powder.

6. The process for the preparation of melt-spun far infrared polyamide fibers according to claim 1, characterized in that, In step (3), the amount of the added modified far-infrared powder is 1-5wt% of the caprolactam; and the amount of the added water is 1-5wt% of the caprolactam, and the amount of the added capping agent is 0.1-0.5wt% of the caprolactam.

7. The process for the preparation of melt direct spun far infrared polyamide fibers according to claim 1 or 5 or 6, characterized in that, In step (3), the copolymer component is added to the mixture together with the water and the capping agent to perform ring-opening reaction; the copolymer component is one or more of polyamide salt, caprolactone, poly caprolactone and polyester.

8. The process for the preparation of melt-spun far infrared polyamide fibers according to claim 1, characterized in that, In step (3), the temperature of the ring-opening reaction is 210-250℃, and the reaction pressure is controlled at 0.5-2.5MPa; and the reaction is terminated when the number average molecular weight of the obtained melt is 5000-30000.

9. The process for the preparation of melt-spun far infrared polyamide fibers according to claim 1 or 8, characterized in that, In step (4), the temperature of the polycondensation reaction is 210-270℃, and the reaction pressure is controlled at -0.1-3MPa; and the reaction is terminated when the number average molecular weight of the obtained product is 15000-50000, the content of extractable substance is <4%, and the relative viscosity of the melt is 2.0-4.

0.

10. The process for the preparation of melt direct spun far infrared polyamide fibers according to claim 1 or 8, characterized in that, In step (4), the temperature of the spinning is 230-270℃.

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