A microporous polyester composite fiber with unidirectional moisture-wicking function and its spinning process

Abstract

This application relates to the field of chemical fiber manufacturing technology, specifically disclosing a microporous polyester composite fiber with unidirectional moisture-wicking function and its spinning process. It is made from raw materials comprising the following parts by weight: 75-88 parts polyethylene terephthalate matrix resin; 3-12 parts alkali-soluble copolyester chips; 4-9 parts polyoxyethylene grafted hydrophilic modifier; 1.5-6 parts organic pore-forming agent; 0.8-4 parts functional submicron particles; and 0.15-0.6 parts heat stabilizer. The preparation method is as follows: S1, raw material pretreatment; S2, melt blending; S3, composite spinning; and S4, post-treatment. The composite fiber of this application can be used to prepare high-performance sportswear, underwear, outdoor protective fabrics, and medical and health nonwoven fabrics, possessing advantages such as unidirectional moisture-wicking function, high mechanical strength, stable microporous structure, long-lasting hydrophilic effect, and processing thermal stability.

Description

Technical Field

[0001] This application relates to the field of chemical fiber manufacturing technology, and more specifically, to a microporous polyester composite fiber with unidirectional moisture-wicking function and its spinning process. Background Technology

[0002] Chemical fiber manufacturing technology transforms natural or synthetic polymers into fiber forms, finding wide application in clothing, medical, construction, transportation, and environmental protection fields. Its advantages lie in its ability to customize fibers with high strength, corrosion resistance, lightweight properties, UV resistance, and flame retardancy to meet diverse needs. In the clothing industry, synthetic fibers such as polyester and nylon are wear-resistant and easy to care for. In the medical field, absorbable sutures and artificial blood vessels significantly improve medical outcomes. In industry, high-strength materials such as carbon fiber drive lightweighting in aerospace and automotive sectors. This technology not only overcomes the limitations of natural fibers in terms of yield and performance but also reduces resource consumption and environmental pollution through recycling, combining economic efficiency with sustainability.

[0003] Related chemical fibers have been improved by constructing microporous structures on the fiber surface and inside through physical foaming or chemical etching. However, such methods are prone to uneven micropore distribution and decreased pore wall strength. Moreover, existing hydrophilic modifiers have poor compatibility with the matrix, making it difficult to form a stable hydrophilic network. At the same time, the introduction of alkali-soluble components often affects the overall mechanical properties and structural uniformity of the fiber due to poor dispersion during melt spinning. As a result, the resulting fibers are prone to microporous structure collapse after repeated use or post-treatment, significant reduction in unidirectional moisture wicking function, and problems such as insufficient tensile strength and poor wash resistance. Summary of the Invention

[0004] To address the problem that the microporous structure of polyester fibers is prone to collapse and the unidirectional moisture-wicking function is reduced due to the use of physical foaming or chemical etching methods for related chemical fibers, this application provides a microporous polyester composite fiber with unidirectional moisture-wicking function and its spinning process.

[0005] In a first aspect, this application provides a microporous polyester composite fiber with unidirectional moisture-wicking function, using the following technical solution: A microporous polyester composite fiber with unidirectional moisture-wicking function is made from the following raw materials in parts by weight: 75-88 parts of polyethylene terephthalate matrix resin; 3-12 parts of alkali-soluble copolyester chips; 4-9 parts of polyoxyethylene grafted hydrophilic modifier; 1.5-6 parts of organic pore-forming agent; 0.8-4 parts of functional submicron particles; and 0.15-0.6 parts of heat stabilizer.

[0006] By adopting the above technical solution, since polyethylene terephthalate matrix resin constitutes the mechanical skeleton of the fiber, alkali-soluble copolyester chips provide the basis for the subsequent formation of surface microporous structure through alkali treatment, polyoxyethylene grafted hydrophilic modifier introduces persistent hydrophilic segments into the fiber to achieve rapid moisture conduction, organic pore-forming agent can create micropores inside and on the surface of the fiber through dissolution or thermal decomposition after fiber forming to enhance capillary effect, functional submicron particles play a heterogeneous nucleation and reinforcement role to improve the crystallization behavior and mechanical properties of the fiber, and heat stabilizer inhibits thermal oxidative degradation during melt processing, the synergistic effect of each component ultimately yields a composite fiber with high mechanical properties, stable microporous structure and unidirectional moisture conduction function.

[0007] Preferably, the polyoxyethylene grafted hydrophilic modifier is one or more of polyethylene glycol monomethyl ether grafted copolyester, polyoxyethylene-polyoxypropylene block copolyether, or polyvinylpyrrolidone grafted polyester; the organic pore-forming agent is one or more of polyethylene glycol, polyvinyl alcohol, or polycaprolactone.

[0008] By adopting the above technical solution, since the selected polyoxyethylene grafted hydrophilic modifier contains both polyester-compatible segments and strongly hydrophilic polyoxyethylene or pyrrolidone segments in its molecular chain, it ensures its dispersion and interfacial bonding in the polyester matrix and forms stable hydrophilic channels on the fiber surface and inside. The selected organic pore-forming agent has thermal stability at the melt spinning temperature and can form microphase separation with the polyester matrix. It is easily selectively removed during post-treatment or subsequent alkali reduction process to form micropores with controllable pore size. Therefore, the combination of preferred raw materials further improves the hydrophilic durability and the regularity of the porous structure of the fiber, and strengthens the driving force of unidirectional moisture conduction.

[0009] Preferably, the functional submicron particles are one or more of submicron silica, submicron zinc oxide, or submicron calcium carbonate whiskers; the heat stabilizer is one or more of triphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, or pentaerythritol diphosphite (2,4-di-tert-butylphenyl) bis(2,4-di-tert-butylphenyl) phosphite.

[0010] By adopting the above technical solution, the selected functional submicron particles have high specific surface area and surface activity, which can act as nucleating agents during melt blending to promote the formation of a finer crystal structure in the polyester matrix. At the same time, their rigid particle characteristics help to improve the modulus and dimensional stability of the fiber. The selected phosphite heat stabilizer can efficiently capture peroxide free radicals generated during processing and decompose hydroperoxides, thereby blocking the thermal oxidation chain reaction of the polyester melt. Therefore, the optimal combination of raw materials ensures that the fiber melt has processing stability and excellent physical and mechanical properties of the final product under the conditions of introducing multiple modified components and complex processing.

[0011] Preferably, the composite fiber has a core-sheath composite structure, wherein the core layer is polyethylene terephthalate matrix resin, and the sheath layer is a hydrophilic modified component composed of alkali-soluble copolyester chips and a polyoxyethylene grafted hydrophilic modifier; the cross section of the composite fiber is trefoil, cross, Y, H or multi-leaf.

[0012] By adopting the above technical solution, the core-sheath composite structure concentrates the hydrophilic components on the fiber surface, enabling the fiber to quickly absorb sweat and transport it to the core layer when in contact with the skin. The hydrophobic matrix of the core layer forms a channel for directional moisture transport. Combined with the irregular cross-section design, the surface area of ​​the fiber is increased and more grooves and capillary gaps are formed. These structures work together to construct a directional moisture transfer path from the convex to the concave part of the cross-section or from the hydrophilic skin layer to the hydrophobic core layer. Therefore, the synergistic design of the core-sheath structure and the irregular cross-section achieves rapid absorption, directional diffusion and efficient evaporation of moisture from the fiber structure.

[0013] Secondly, this application provides a spinning process for microporous polyester composite fibers with unidirectional moisture-wicking function, using the following technical solution: A spinning process for a microporous polyester composite fiber with unidirectional moisture-wicking function includes the following steps: S1. Raw material pretreatment: Polyethylene terephthalate matrix resin and alkali-soluble copolyester chips are pre-crystallized and dried respectively, and polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent and functional submicron particles are vacuum dried respectively. S2. Melt blending: The dried polyethylene terephthalate matrix resin, alkali-soluble copolyester chips, polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent, functional submicron particles and heat stabilizer are melt blended in a twin-screw extruder to obtain a spinning melt. S3. Composite spinning: The spinning melt obtained in step S2 is conveyed to the irregular cross section spinneret through the core-sheath composite spinning assembly to perform melt spinning and obtain nascent composite fibers. S4. Post-processing: The nascent composite fibers obtained in step S3 are sequentially subjected to side-blowing cooling, oiling and bundling, multi-stage hot stretching and heat setting to obtain the microporous polyester composite fibers.

[0014] By adopting the above technical solution, the raw material pretreatment step provides a dry and stable material basis for subsequent melt blending, avoiding the hydrolytic degradation of polymers at high temperatures. The melt blending step allows multiple functional components to be uniformly dispersed in the polyester matrix under the high shear and mixing action of the twin screw and form a stable spinning melt. The composite spinning step shapes the homogeneous melt into nascent fibers with a core-sheath structure and irregular cross-section through specific components and spinnerets. The post-treatment step fixes the morphological structure of the fibers through cooling, stretching and heat setting, and develops the expected crystallization and orientation structure.

[0015] Preferably, in step S1, the drying temperature of the polyethylene terephthalate matrix resin is 130~160℃, the drying time is 6~14h, and the moisture content after drying is ≤40ppm; the drying temperature of the alkali-soluble copolyester chips is 110~140℃, the drying time is 4~10h; and the vacuum drying temperature of the polyoxyethylene grafted hydrophilic modifier is 50~80℃, the drying time is 3~8h.

[0016] By adopting the above technical solutions, the relatively high drying temperature and long drying time used for polyethylene terephthalate matrix resin are to remove trace amounts of moisture inside to meet its melt processing requirements. The slightly lower drying temperature used for alkali-soluble copolyester chips is to prevent them from sticking together or undergoing thermal oxidation due to their heat sensitivity. The lower vacuum drying temperature used for polyoxyethylene grafted hydrophilic modifiers is to avoid their thermal decomposition or melt adhesion, while removing surface adsorbed water to ensure their dispersibility during blending. Therefore, the graded and classified drying process is precisely controlled according to the thermal properties and hygroscopic characteristics of each raw material, providing a guarantee for obtaining high-quality spinning melt.

[0017] Preferably, in step S2, the melt blending temperature is 270~300℃, the main screw speed of the twin-screw extruder is 200~400 r / min, and the residence time of the melt in the extruder is 2~7 min.

[0018] By adopting the above technical solution, the set melt blending temperature range can ensure that the polyethylene terephthalate matrix resin is fully melted, while also taking into account the processing temperature of components such as alkali-soluble copolyester, organic pore-forming agent and hydrophilic modifier, thus avoiding overheating and decomposition. At the same time, the coordination of the main screw speed and residence time ensures that each component can obtain sufficient shear dispersion and distribution mixing in the melt, while allowing the heat stabilizer to play its full role and preventing excessive thermal degradation of the melt due to excessive residence time.

[0019] Preferably, in step S3, the temperature of the spinning box during composite spinning is 280~300℃, the spinning speed is 1200~3800m / min, the number of spinneret holes in the irregular cross-section spinneret is 36~168, and the volume ratio of the skin melt to the core melt in the skin-core composite spinning assembly is 1:4~2:3.

[0020] By adopting the above technical solution, since the spinning box temperature is slightly higher than the melt blending temperature to maintain good fluidity of the melt during the process of conveying it to the spinneret and to eliminate viscosity fluctuations, the selection of the spinning speed determines the pre-orientation and crystallization state of the fiber, providing conditions for the subsequent stretching process. The design of the number of holes in the shaped spinneret balances the single filament fineness and production efficiency, and the setting of the core-sheath melt volume ratio precisely controls the sheath thickness, ensuring that the hydrophilic modified layer provides sufficient moisture-wicking function without affecting the overall mechanical skeleton of the fiber. Therefore, the synergistic effect of various parameters in the composite spinning step is the key forming control point for accurately transforming homogeneous melt into nascent fibers with specific composite structures and cross-sectional morphologies.

[0021] Preferably, in step S3, before the nascent composite fiber is cooled by side blowing, an electrostatic field with an electric field strength of 3~15kV / cm is applied to the nascent fiber bundle at a distance of 1~5cm below the irregular cross-section spinneret, and the treatment time is 0.02~0.8s.

[0022] By adopting the above technical solution, an electrostatic field is applied at the critical stage when the melt stream just exits the spinneret and has not yet fully solidified. The electric field force will generate polarization and stretching effects on the melt surface, causing the molecular chains to be oriented in a certain way along the direction of the electric field. At the same time, the electric field will affect the distribution of the surface tension of the melt, which will help to form and maintain the edge of the irregular cross section clearly, and induce functional particles to accumulate on the fiber surface. Therefore, this electrostatic field treatment, as an external field-assisted means, further optimizes the microstructure of the nascent fiber from the perspective of molecular chain arrangement and morphological solidification, providing benefits for obtaining higher quality irregular composite fibers.

[0023] Preferably, in step S4, the side-blowing cooling air supply temperature is 20~28℃, the air supply velocity is 0.4~0.9m / s, and the relative humidity is 55%~75%; the total stretching ratio of the multi-stage hot stretching is 2.8~5.0 times, the stretching temperature is 90~150℃; the heat setting temperature is 150~190℃, and the heat setting time is 4~12min.

[0024] By adopting the above technical solution, the mild and uniform side-blowing cooling conditions allow the nascent fibers to solidify and crystallize at a controllable rate, which is conducive to forming a uniform core-sheath interface and a regular cross-sectional shape. Multi-stage hot stretching gradually stretches the fibers under conditions higher than the glass transition temperature, causing the macromolecular chains and aggregated structures to be highly oriented along the fiber axis and form a stable crystalline structure. At the same time, it promotes the extension of internal micropores along the stretching direction to form more capillary channels. The final heat setting treatment relaxes internal stress, improves crystallization, and fixes the fiber morphology at a higher temperature. Therefore, the post-treatment process, through the synergistic sequence and parameters of cooling, stretching, and heat setting, ultimately endows the composite fiber with excellent mechanical properties, dimensional stability, and a preset one-way moisture-wicking function.

[0025] In summary, this application has the following beneficial effects: 1. Because this application uses polyethylene terephthalate as the matrix, and synergistically combines alkali-soluble copolyester, polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent, functional submicron particles and heat stabilizer, the alkali-soluble copolyester provides a reactive substrate for subsequent micropore formation, the hydrophilic modifier constructs a durable hydrophilic network in the matrix, the organic pore-forming agent forms micropores that enhance capillary effect through subsequent treatment, and the submicron particles and heat stabilizer play the roles of reinforcing and stabilizing the processing, respectively, a microporous polyester composite fiber with excellent mechanical properties, stable structure and unidirectional moisture-wicking function is obtained.

[0026] 2. In this application, a combination of polyoxyethylene grafted hydrophilic modifier and organic pore-forming agent is preferred. The hydrophilic modifier contains segments compatible with polyester, ensuring its dispersion and interfacial bonding in the matrix, forming stable and non-migrating hydrophilic channels. The organic pore-forming agent can form controllable microphase separation with the matrix, which is easy to remove in subsequent processing to form regular micropores, thereby enhancing the fiber's moisture absorption, moisture conduction and water evaporation capabilities, thus obtaining superior and durable unidirectional moisture conduction performance.

[0027] 3. This application further adopts a core-sheath composite structure and irregular cross-section design, in which the hydrophilic component is confined in the sheath layer to capture moisture, while the hydrophobic core layer forms a dry channel for directional moisture transport. The irregular cross-section increases the fiber surface area and forms natural capillary grooves. This structural design allows moisture to be guided from the hydrophilic area on the fiber surface to the core and deep grooves, thus realizing the directional transfer of moisture from the surface to the inside and from the convex to the concave.

[0028] 4. The spinning method of this application ensures the processing stability of each raw material through graded drying pretreatment, then achieves uniform dispersion of multiple components through temperature-controlled and shear-controlled twin-screw melt blending, and then forms the target nascent fiber through core-sheath composite spinning and shaped spinneret. Finally, the fiber structure is solidified and improved by post-treatment processes including electrostatic field treatment, multi-stage hot stretching and heat setting. Therefore, microporous polyester composite fiber with controllable structure, stable performance and efficient preparation is obtained.

[0029] 5. The method of this application introduces electrostatic field treatment in the spinning process. Since this treatment is applied during the initial solidification stage of the melt stream, the electric field force can promote the pre-orientation of molecular chains along the fiber axis and assist in stabilizing the forming of irregular cross sections. This step, together with the cooling and stretching processes, improves the micro-orientation and crystal structure of the fiber, providing a structural basis for the extension of internal micropore channels and the improvement of final mechanical properties. Therefore, fibers with clear cross sections, uniform structure and more interconnected moisture-conducting channels are obtained. Attached Figure Description

[0030] Figure 1This is a flowchart of the spinning process for a microporous polyester composite fiber with unidirectional moisture-wicking function proposed in this application. Detailed Implementation

[0031] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] Technical concept: Related chemical fibers have been improved by constructing microporous structures on the fiber surface and inside through physical foaming or chemical etching. However, such methods are prone to uneven micropore distribution and decreased pore wall strength. Moreover, existing hydrophilic modifiers have poor compatibility with the matrix, making it difficult to form a stable hydrophilic network. At the same time, the introduction of alkali-soluble components often affects the overall mechanical properties and structural uniformity of the fiber due to poor dispersion during melt spinning. As a result, the resulting fibers are prone to microporous structure collapse after repeated use or post-treatment, significant reduction in unidirectional moisture wicking function, and problems such as insufficient tensile strength and poor wash resistance.

[0033] This application discloses a microporous polyester composite fiber with unidirectional moisture-wicking function and its spinning process. It is made from raw materials comprising the following parts by weight: 75-88 parts polyethylene terephthalate matrix resin; 3-12 parts alkali-soluble copolyester chips; 4-9 parts polyoxyethylene grafted hydrophilic modifier; 1.5-6 parts organic pore-forming agent; 0.8-4 parts functional submicron particles; and 0.15-0.6 parts heat stabilizer. The preparation method is as follows: S1, raw material pretreatment; S2, melt blending; S3, composite spinning; and S4, post-treatment.

[0034] This application uses polyethylene terephthalate as the matrix, and synergistically combines alkali-soluble copolyester, polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent, functional submicron particles and heat stabilizer. Among them, the alkali-soluble copolyester provides a reactive substrate for subsequent micropore formation, the hydrophilic modifier constructs a durable hydrophilic network in the matrix, the organic pore-forming agent forms micropores that enhance capillary effect through subsequent treatment, and the submicron particles and heat stabilizer play the roles of reinforcing and stabilizing the processing, respectively. Therefore, a microporous polyester composite fiber with excellent mechanical properties, stable structure and unidirectional moisture-wicking function is obtained.

[0035] Example 1: This example provides a microporous polyester composite fiber with unidirectional moisture-wicking function, which is made from the following raw materials in parts by weight: 75 parts of polyethylene terephthalate matrix resin; 3 parts of alkali-soluble copolyester chips; 4 parts of polyoxyethylene grafted hydrophilic modifier; 1.5 parts of organic pore-forming agent; 0.8 parts of functional submicron particles; and 0.15 parts of heat stabilizer.

[0036] The composite fiber is a polyoxyethylene grafted hydrophilic modifier, which is a polyethylene glycol monomethyl ether grafted copolyester; the organic pore-forming agent is polyethylene glycol; the functional submicron particles are submicron silica; the heat stabilizer is triphenyl phosphite; the composite fiber has a core-sheath composite structure, wherein the core layer is a polyethylene terephthalate matrix resin, and the sheath layer is a hydrophilic modifier composed of alkali-soluble copolyester chips and a polyoxyethylene grafted hydrophilic modifier; the cross-section of the composite fiber is trilobal.

[0037] The spinning process of the microporous polyester composite fiber with unidirectional moisture-wicking function mentioned above includes the following steps: S1. Raw material pretreatment: Polyethylene terephthalate matrix resin and alkali-soluble copolyester chips are pre-crystallized and dried respectively, and polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent and functional submicron particles are vacuum dried respectively. The drying temperature of the polyethylene terephthalate matrix resin was 130℃, the drying time was 6 hours, and the moisture content after drying was 30 ppm; the drying temperature of the alkali-soluble copolyester chips was 110℃, and the drying time was 4 hours; the vacuum drying temperature of the polyoxyethylene grafted hydrophilic modifier was 50℃, and the drying time was 3 hours.

[0038] S2. Melt blending: The dried polyethylene terephthalate matrix resin, alkali-soluble copolyester chips, polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent, functional submicron particles and heat stabilizer are melt blended in a twin-screw extruder to obtain a spinning melt. The melt blending temperature is 270℃, the main screw speed of the twin-screw extruder is 200r / min, and the residence time of the melt in the extruder is 2min.

[0039] S3. Composite spinning: The spinning melt obtained in step S2 is conveyed to the irregular cross section spinneret through the core-sheath composite spinning assembly to perform melt spinning and obtain nascent composite fibers. In the composite spinning process, the spinning box temperature is 280℃, the spinning speed is 1200m / min, the spinneret with irregular cross-section has 36 spinneret holes, and the volume ratio of the skin melt to the core melt in the skin-core composite spinning assembly is 20:80.

[0040] Before the nascent composite fibers are cooled by side blowing, an electrostatic field with an electric field strength of 3kV / cm is applied to the nascent fiber bundle 1cm below the irregular cross-section spinneret for 0.02s.

[0041] S4. Post-processing: The nascent composite fibers obtained in step S3 are sequentially subjected to side-blowing cooling, oiling and bundling, multi-stage hot stretching and heat setting to obtain microporous polyester composite fibers.

[0042] The side-blowing cooling system has an air supply temperature of 20℃, an air supply velocity of 0.4m / s, and a relative humidity of 55%; the total stretching ratio of the multi-stage hot stretching is 2.8 times, the stretching temperature is 90℃; the heat setting temperature is 150℃, and the heat setting time is 4min.

[0043] Example 2: This example provides a microporous polyester composite fiber with unidirectional moisture-wicking function, made from raw materials comprising the following parts by weight: 81.5 parts polyethylene terephthalate matrix resin; 7.5 parts alkali-soluble copolyester chips; 6.5 parts polyoxyethylene grafted hydrophilic modifier; 3.75 parts organic pore-forming agent; 2.4 parts functional submicron particles; and 0.375 parts heat stabilizer.

[0044] The composite fiber is a polyoxyethylene-polyoxypropylene block copolymer, which is a polyoxyethylene-polyoxypropylene grafted hydrophilic modifier. The organic pore-forming agent is polyvinyl alcohol. The functional submicron particles are submicron zinc oxide. The heat stabilizer is tris(2,4-di-tert-butylphenyl) phosphite. The composite fiber has a core-sheath composite structure, in which the core layer is polyethylene terephthalate matrix resin and the sheath layer is a hydrophilic modifier composed of alkali-soluble copolyester chips and a polyoxyethylene grafted hydrophilic modifier. The cross-section of the composite fiber is cross-shaped.

[0045] The spinning process of the microporous polyester composite fiber with unidirectional moisture-wicking function mentioned above includes the following steps: S1. Raw material pretreatment: Polyethylene terephthalate matrix resin and alkali-soluble copolyester chips are pre-crystallized and dried respectively, and polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent and functional submicron particles are vacuum dried respectively. The drying temperature of the polyethylene terephthalate matrix resin was 145℃, the drying time was 10h, and the moisture content after drying was 40ppm; the drying temperature of the alkali-soluble copolyester chips was 125℃, the drying time was 7h; and the vacuum drying temperature of the polyoxyethylene grafted hydrophilic modifier was 65℃, the drying time was 5.5h.

[0046] S2. Melt blending: The dried polyethylene terephthalate matrix resin, alkali-soluble copolyester chips, polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent, functional submicron particles and heat stabilizer are melt blended in a twin-screw extruder to obtain a spinning melt. The melt blending temperature is 285℃, the main screw speed of the twin-screw extruder is 300r / min, and the residence time of the melt in the extruder is 4.5min.

[0047] S3. Composite spinning: The spinning melt obtained in step S2 is conveyed to the irregular cross section spinneret through the core-sheath composite spinning assembly to perform melt spinning and obtain nascent composite fibers. In the composite spinning process, the spinning box temperature is 290℃, the spinning speed is 2500m / min, the spinneret with irregular cross-section has 102 spinneret holes, and the volume ratio of the skin melt to the core melt in the skin-core composite spinning assembly is 30:70.

[0048] Before the nascent composite fibers are cooled by side blowing, an electrostatic field with an electric field strength of 9kV / cm is applied to the nascent fiber bundle 3cm below the irregular cross-section spinneret for 0.41s.

[0049] S4. Post-processing: The nascent composite fibers obtained in step S3 are sequentially subjected to side-blowing cooling, oiling and bundling, multi-stage hot stretching and heat setting to obtain microporous polyester composite fibers.

[0050] The side-blowing cooling system has an air supply temperature of 24℃, an air supply velocity of 0.65m / s, and a relative humidity of 65%; the total stretching ratio of the multi-stage hot stretching is 3.9 times, the stretching temperature is 120℃; the heat setting temperature is 170℃, and the heat setting time is 8min.

[0051] Example 3: This example provides a microporous polyester composite fiber with unidirectional moisture-wicking function, which is made from the following raw materials in parts by weight: 88 parts of polyethylene terephthalate matrix resin; 12 parts of alkali-soluble copolyester chips; 9 parts of polyoxyethylene grafted hydrophilic modifier; 6 parts of organic pore-forming agent; 4 parts of functional submicron particles; and 0.6 parts of heat stabilizer.

[0052] The composite fiber is a polyoxyethylene-grafted hydrophilic modifier, which is a polyvinylpyrrolidone-grafted polyester; an organic pore-forming agent, which is polycaprolactone; functional submicron particles, which are submicron calcium carbonate whiskers; a heat stabilizer, which is bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite; and a core-sheath composite structure, wherein the core layer is a polyethylene terephthalate matrix resin, and the sheath layer is a hydrophilic modifier composed of alkali-soluble copolyester chips and a polyoxyethylene-grafted hydrophilic modifier; and the cross-section of the composite fiber is Y-shaped.

[0053] The spinning process of the microporous polyester composite fiber with unidirectional moisture-wicking function mentioned above includes the following steps: S1. Raw material pretreatment: Polyethylene terephthalate matrix resin and alkali-soluble copolyester chips are pre-crystallized and dried respectively, and polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent and functional submicron particles are vacuum dried respectively. The drying temperature of the polyethylene terephthalate matrix resin was 160℃, the drying time was 14h, and the moisture content after drying was 20ppm; the drying temperature of the alkali-soluble copolyester chips was 140℃, the drying time was 10h; and the vacuum drying temperature of the polyoxyethylene grafted hydrophilic modifier was 80℃, the drying time was 8h.

[0054] S2. Melt blending: The dried polyethylene terephthalate matrix resin, alkali-soluble copolyester chips, polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent, functional submicron particles and heat stabilizer are melt blended in a twin-screw extruder to obtain a spinning melt. The melt blending temperature is 300℃, the main screw speed of the twin-screw extruder is 400r / min, and the residence time of the melt in the extruder is 7min.

[0055] S3. Composite spinning: The spinning melt obtained in step S2 is conveyed to the irregular cross section spinneret through the core-sheath composite spinning assembly to perform melt spinning and obtain nascent composite fibers. In the composite spinning process, the spinning box temperature is 300℃, the spinning speed is 3800m / min, the spinneret with irregular cross-section has 168 spinneret holes, and the volume ratio of the skin melt to the core melt in the skin-core composite spinning assembly is 40:60.

[0056] Before the nascent composite fibers are cooled by side blowing, an electrostatic field with an electric field strength of 15kV / cm is applied to the nascent fiber bundle 5cm below the irregular cross-section spinneret for 0.8s.

[0057] S4. Post-processing: The nascent composite fibers obtained in step S3 are sequentially subjected to side-blowing cooling, oiling and bundling, multi-stage hot stretching and heat setting to obtain microporous polyester composite fibers.

[0058] The side-blowing cooling system has an air supply temperature of 28℃, an air supply velocity of 0.9m / s, and a relative humidity of 75%; the total stretching ratio of the multi-stage hot stretching is 5.0 times, the stretching temperature is 150℃; the heat setting temperature is 190℃, and the heat setting time is 12min.

[0059] Comparative Example 1: This comparative example is the same as that in Example 1, except that the amount of polyethylene terephthalate matrix resin used is 50 parts by weight, and the rest is the same as that in Example 1.

[0060] Comparative Example 2: This comparative example is the same as that in Example 1, except that the amount of alkali-soluble copolyester chips used is 20 parts by weight, and the rest is the same as in Example 1.

[0061] Comparative Example 3: This comparative example is the same as that in Example 1, except that the amount of organic pore-forming agent used is 0.5 parts by weight, and the rest is the same as that in Example 1.

[0062] Comparative Example 4: This comparative example refers to the content of Example 1, except that the melting and blending temperature in step S2 is 350°C, and the rest is the same as Example 1.

[0063] Comparative Example 5: This comparative example refers to the content of Example 1, except that the electrostatic field strength applied in step S3 is 25kV / cm, and the rest is the same as Example 1.

[0064] Comparative Example 6: This comparative example refers to the content of Example 1, except that in step S3, the volume ratio of the sheath melt to the core melt in the sheath-core composite spinning assembly is 60:40, and the rest is the same as in Example 1.

[0065] Performance testing Sample preparation: The microporous polyester composite fibers obtained in Examples 1-3 and Comparative Examples 1-6 were knitted into single-sided plain knitted fabrics with consistent unit area mass on a circular knitting machine of the same specification. All fabric samples were then subjected to moisture equilibration under standard temperature and humidity conditions, and uniformly subjected to alkali reduction treatment to dissolve the alkali-soluble copolyester components in the cortex to form a surface microporous structure. After treatment, they were further subjected to hydrophilic finishing and shaping to finally prepare standard fabric samples for performance testing.

[0066] Unidirectional moisture wicking performance test: Take a strip of fabric of specified size, immerse one end of it vertically in distilled water, and record the height of the water rising vertically along the fabric within a specific time period, i.e., the wicking height, which reflects the longitudinal water absorption rate of the fiber; at the same time, the unidirectional transfer index is tested using the drop method, a certain amount of test liquid is dropped onto the inner layer of the fabric, and the difference in moisture content between the inner and outer layers is measured after a specified time, and the ability index of moisture to be directionally transferred from the inner layer to the outer layer is calculated; the wicking height test refers to the national standard GB / T21655.1, and the unidirectional transfer index test refers to the industry standard FZ / T01071.

[0067] Table 1: Results of Unidirectional Moisture Conductivity Test

[0068] Fiber structure characterization: After liquid nitrogen brittle fracture, the fiber samples were sputter-coated with gold and placed under a scanning electron microscope to observe whether the cross-sectional shape was the designed irregular structure and whether the composite interface between the cortex and core was clear. At the same time, the fiber surface was observed at high magnification to confirm whether a uniform microporous structure was formed after alkali reduction treatment, and the size, distribution density and morphology of the micropores were evaluated to verify the synergistic pore-forming effect of the pore-forming agent and the irregular cross-section. This characterization was performed in accordance with the general methods of microscopic analysis of related materials.

[0069] Table 2: Fiber Structure Characterization Results

[0070] Mechanical property testing: A single fiber is held in a single-fiber tensile tester and stretched at a constant rate until it breaks. The maximum force and elongation at the point of break are recorded. After testing multiple samples, the average value is calculated to comprehensively evaluate whether the mechanical properties of the fiber meet the requirements of textile processing and application. This test is conducted in accordance with the national standard GB / T3916.

[0071] Table 3: Results of Mechanical Performance Tests

[0072] Durability testing: Fabric samples were washed multiple times in a household washing machine according to standard procedures. After washing and drying, the wicking height and unidirectional transfer index were tested again to observe the performance degradation. At the same time, more severe treatment conditions were simulated by placing the fibers in an alkaline solution of a specified concentration for a longer period of time to observe changes in surface structure and retention rate of mechanical properties, in order to evaluate the binding stability of functional components in the matrix. The water wash resistance test was conducted in accordance with the national standard GB / T12490. The alkali treatment stability was characterized by the mass loss rate and performance retention rate.

[0073] Table 4: Results of Water Washability

[0074] Table 5: Results of Alkali Resistance Treatment

[0075] Example Conclusion: Based on Examples 1-3 and Comparative Example 1, and in conjunction with Tables 1, 3, 4 and 5, it can be seen that the amount of polyethylene terephthalate (PET) matrix resin used is the basis for maintaining the structural integrity and functional stability of the fiber. Appropriate use can ensure that the fiber has high mechanical strength, durability and unidirectional moisture-wicking properties, while insufficient use will lead to structural weakening and performance degradation.

[0076] Based on Examples 1-3 and Comparative Example 2, and in conjunction with Table 2, it can be seen that the amount of alkali-soluble copolyester chips used needs to form a synergistic balance with the matrix resin. When the amount is appropriate, a controllable reactive substrate can be constructed in the skin layer to form uniform micropores. However, if the amount is too high, it will destroy the skin-core composite structure, resulting in the loss of micropores and affecting the moisture-wicking function.

[0077] As can be seen from Examples 1-3 and Comparative Example 3, and Table 2, the appropriate addition of organic pore-forming agent is the guarantee for the formation of regular microporous structure. It can enhance the capillary effect by constructing micropores on the fiber surface through controllable microphase separation and subsequent treatment, thereby improving the unidirectional moisture-wicking efficiency. However, if the amount is insufficient, an effective microporous channel cannot be formed.

[0078] Based on Examples 1-3 and Comparative Example 4, and in conjunction with Tables 1 and 3, it can be seen that controlling the melt blending temperature is a factor in achieving uniform dispersion and structural stability of multiple components. A suitable temperature is conducive to the compatibility of each component and the formation of micropores, while excessively high temperatures can lead to thermal degradation, thereby affecting the moisture conductivity and mechanical strength.

[0079] Based on Examples 1-3 and Comparative Example 5, and in conjunction with Tables 3 and 5, it can be seen that optimizing the intensity of electrostatic field treatment can promote the pre-orientation of molecular chains and the stability of irregular cross sections, thereby enhancing the uniformity of fiber structure and the permeability of moisture-conducting channels. However, excessive intensity can lead to structural defects, resulting in a decrease in mechanical properties and durability.

[0080] Based on Examples 1-3 and Comparative Example 6, and in conjunction with Tables 2, 3 and 4, it can be seen that a reasonable design of the volume ratio of the skin layer to the core layer in the skin-core composite structure can balance the hydrophilic moisture conduction and structural support functions. An appropriate ratio allows the hydrophilic skin layer to effectively capture moisture while the hydrophobic core layer transports it in a directional manner, thereby achieving efficient unidirectional moisture conduction and high durability. However, an imbalance in the ratio weakens the structural stability and performance.

[0081] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without providing any contribution, but such modifications are protected by patent law as long as they are within the scope of the claims of this application.

Claims

1. A microporous polyester composite fiber with unidirectional moisture-wicking function, characterized in that, It is made from the following raw materials in parts by weight: 75-88 parts polyethylene terephthalate matrix resin; 3-12 parts alkali-soluble copolyester chips; 4-9 parts polyoxyethylene grafted hydrophilic modifier; 1.5-6 parts organic pore-forming agent; 0.8-4 parts functional submicron particles; and 0.15-0.6 parts heat stabilizer.

2. The microporous polyester composite fiber with unidirectional moisture-wicking function according to claim 1, characterized in that, The polyoxyethylene grafted hydrophilic modifier is one or more of polyethylene glycol monomethyl ether grafted copolyester, polyoxyethylene-polyoxypropylene block copolyether, or polyvinylpyrrolidone grafted polyester; the organic pore-forming agent is one or more of polyethylene glycol, polyvinyl alcohol, or polycaprolactone.

3. The microporous polyester composite fiber with unidirectional moisture-wicking function according to claim 1, characterized in that, The functional submicron particles are one or more of submicron silica, submicron zinc oxide, or submicron calcium carbonate whiskers; the heat stabilizer is one or more of triphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, or pentaerythritol diphosphite (2,4-di-tert-butylphenyl) bis(2,4-di-tert-butylphenyl) phosphite.

4. The microporous polyester composite fiber with unidirectional moisture-wicking function according to claim 1, characterized in that, The composite fiber has a core-sheath composite structure, wherein the core layer is polyethylene terephthalate matrix resin, and the sheath layer is a hydrophilic modified component composed of alkali-soluble copolyester chips and a polyoxyethylene grafted hydrophilic modifier; the cross section of the composite fiber is trefoil, cross, Y, H or multi-leaf.

5. A spinning process for microporous polyester composite fibers with unidirectional moisture-wicking function, characterized in that, The microporous polyester composite fiber with unidirectional moisture-wicking function as described in any one of claims 1-4 comprises the following steps: S1. Raw material pretreatment: Polyethylene terephthalate matrix resin and alkali-soluble copolyester chips are pre-crystallized and dried respectively, and polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent and functional submicron particles are vacuum dried respectively. S2. Melt blending: The dried polyethylene terephthalate matrix resin, alkali-soluble copolyester chips, polyoxyethylene grafted hydrophilic modifier, organic pore-forming agent, functional submicron particles and heat stabilizer are melt blended in a twin-screw extruder to obtain a spinning melt. S3. Composite spinning: The spinning melt obtained in step S2 is conveyed to the irregular cross section spinneret through the core-sheath composite spinning assembly to perform melt spinning and obtain nascent composite fibers. S4. Post-processing: The nascent composite fibers obtained in step S3 are sequentially subjected to side-blowing cooling, oiling and bundling, multi-stage hot stretching and heat setting to obtain the microporous polyester composite fibers.

6. The spinning process of a microporous polyester composite fiber with unidirectional moisture-wicking function according to claim 5, characterized in that, In step S1, the drying temperature of the polyethylene terephthalate matrix resin is 130~160℃, the drying time is 6~14h, and the moisture content after drying is ≤40ppm; the drying temperature of the alkali-soluble copolyester chips is 110~140℃, the drying time is 4~10h; and the vacuum drying temperature of the polyoxyethylene grafted hydrophilic modifier is 50~80℃, the drying time is 3~8h.

7. The spinning process of a microporous polyester composite fiber with unidirectional moisture-wicking function according to claim 5, characterized in that, In step S2, the melt blending temperature is 270~300℃, the main screw speed of the twin-screw extruder is 200~400r / min, and the residence time of the melt in the extruder is 2~7min.

8. The spinning process of a microporous polyester composite fiber with unidirectional moisture-wicking function according to claim 5, characterized in that, In step S3, the temperature of the spinning box during composite spinning is 280~300℃, the spinning speed is 1200~3800m / min, the number of spinneret holes in the irregular cross section spinneret is 36~168, and the volume ratio of the skin melt to the core melt in the skin-core composite spinning assembly is 1:4~2:

3.

9. The spinning process of a microporous polyester composite fiber with unidirectional moisture-wicking function according to claim 5, characterized in that, In step S3, before the nascent composite fibers are cooled by side blowing, an electrostatic field with an electric field strength of 3~15kV / cm is applied to the nascent fiber bundle at a distance of 1~5cm below the irregular cross-section spinneret for a treatment time of 0.02~0.8s.

10. The spinning process of a microporous polyester composite fiber with unidirectional moisture-wicking function according to claim 5, characterized in that, In step S4, the side-blowing cooling air supply temperature is 20~28℃, the air supply velocity is 0.4~0.9m / s, and the relative humidity is 55%~75%; the total stretching ratio of multi-stage hot stretching is 2.8~5.0 times, the stretching temperature is 90~150℃; the heat setting temperature is 150~190℃, and the heat setting time is 4~12min.

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