High-moisture-absorption polyamide fiber and preparation method of fabric of high-moisture-absorption polyamide fiber
By introducing hydrophilic groups into nylon fibers and regulating β crystal forms, combining multi-stage stretching and dynamic relaxation processes, the problem of insufficient hygroscopic properties of traditional nylon fibers is solved, high hygroscopicity and rapid drying effects are achieved, and the wear comfort of the fabric is improved.
Patent Information
- Application Number
- CN202510682319.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-26
- Publication Date
- 2025-07-25
AI Technical Summary
Traditional nylon fiber has poor moisture absorption performance, resulting in poor wear comfort in fabrics. The existing modification methods are difficult to take into account both rapid moisture absorption, long-lasting coolness and wear comfort.
Through the synergistic effects of hydrophilic groups introduction, crystallinity regulation and the increase in the proportion of β-crystalline crystals, the copolymerization method is used to modify nylon fibers, and the multi-stage stretching and dynamic relaxation process are used to form highly hygroscopic fibers, combining nanoporous silica and titanium dioxide to improve performance.
The nylon fiber has been improved by 1.5 times, and it can quickly absorb moisture and dry quickly, significantly improving the coolness and heat and humidity comfort.
Smart Images
Figure CN120366923A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of fibers, and particularly to a preparation method of highly moisture-absorbent polyamide fibers and their fabrics. Background Art
[0002] With the popularization of a healthy lifestyle for sports, the market demand for high-performance sportswear is increasing day by day. Polyamide fibers have advantages such as high strength and good abrasion resistance, and are widely used in the textile field. However, traditional polyamide fibers have poor moisture absorption performance, resulting in poor wearing comfort of the fabrics made from them. Especially in environments such as sports and high temperatures, the sweat generated by the human body cannot be absorbed and dissipated by the fabric in time, affecting the wearing experience. Although existing modification methods such as chemical coating or finishing with auxiliaries can partially improve the performance, they generally have problems such as poor durability of the functions and affecting the hand feeling of the fabric, and it is difficult to balance the multiple requirements of moisture absorption and quick drying, long-lasting cool feeling and wearing comfort. There is an urgent need to develop new polyamide fibers to fundamentally solve these technical contradictions. Summary of the Invention
[0003] The purpose of the present invention is to overcome the above-mentioned defects or problems existing in the background art, and provide a preparation method of highly moisture-absorbent polyamide fibers and their fabrics. Through the synergistic effects of introducing hydrophilic groups, regulating the crystallinity and increasing the proportion of β-crystalline form, the moisture absorption performance of polyamide fibers is improved.
[0004] To achieve the above purpose, each embodiment of the present invention adopts the following technical solutions but is not limited to the following:
[0005] The first technical solution relates to a preparation method of highly moisture-absorbent polyamide fibers, including the following steps: Step 1, chemical modification: carrying out hydrophilic chemical modification on polyamide raw materials and blending with ordinary polyamide; Step 2, melt spinning: melting by gradient heating and extruding through a spinneret and cooling to form nascent fibers; Step 3, primary hot stretching: carrying out preliminary stretching at a temperature higher than the glass transition temperature of polyamide to induce the orientation of α-crystalline form; Step 4, secondary wet heat stretching: directionally inducing the transformation of α-crystalline form to β-crystalline form in a saturated steam environment; Step 5, tertiary dynamic relaxation: using temperature oscillation treatment to stabilize the β-crystalline form and expand the amorphous region; Step 6, winding and forming.
[0006] The second technical solution is based on the first technical solution. Among them, in Step 1 of chemical modification, the copolymerization method is adopted, polyethylene glycol, terephthalic acid and caprolactam are copolymerized to form hydrophilic modified polyamide, and a silane coupling agent is added; the dosage of polyethylene glycol is 3%; in the blend, the molar ratio of ordinary polyamide to modified polyamide is 9:1; the dosage of the silane coupling agent is 0.5%.
[0007] The third technical solution is based on the second technical solution. In step 2, melt spinning is carried out using a screw extruder. The gradient heating is divided into three zones. The temperature of the first zone is 240°C, the temperature of the second zone is 260°C, and the temperature of the third zone is 265°C. The orifice shape of the spinneret is circular, the orifice diameter is 0.18 mm, and the number of orifices is 34. Cooling is carried out by side blowing, with a temperature of 17 - 19°C, a humidity of 70 - 80%, and a wind speed of 0.4 m / s.
[0008] The fourth technical solution is based on the first technical solution. In step 3, the first-stage hot stretching is carried out at 180°C, the stretching ratio is 2.5 times, and the stretching rate is 300 m / min.
[0009] The fifth technical solution is based on the first technical solution. In step 4, the second-stage wet heat stretching is carried out in a saturated steam environment at 90 - 100°C, the stretching ratio is 1.8 times, and the humidity is maintained at 100% RH.
[0010] The sixth technical solution is based on the first technical solution. In step 5, the third-stage dynamic relaxation uses a temperature oscillation of 120 - 60°C, an oscillation frequency of 1 Hz, a period of 60 s, a total duration of 20 min, and the tension is controlled at 0.5 cN / dtex.
[0011] The seventh technical solution is based on the first technical solution. In step 6, the fiber winding and forming are completed by controlling the tension under constant temperature and moisture-proof conditions. The winding speed is 3200 m / min, the winding tension is 18 - 22 cN, and the forming environment temperature is controlled at 25°C.
[0012] The eighth technical solution is based on the second technical solution. In step 1, it is suitable to add reflective heat-insulating particles and a matting agent to the blend. Among them, the reflective heat-insulating particles are nano-porous silica, and the matting agent is titanium dioxide.
[0013] The ninth technical solution is based on any one of the first to eighth technical solutions. A highly moisture-absorbent polyamide fiber is made by using the preparation method of the above-mentioned highly moisture-absorbent polyamide fiber. The crystallinity of the polyamide fiber is 35 - 42%, among which the proportion of the β crystal form is 35 - 45%, and nano-scale pores with a size of 10 - 50 nm are distributed on the surface.
[0014] The tenth technical solution is based on the ninth technical solution. A fabric is woven from 85% of the above-mentioned highly moisture-absorbent polyamide fiber and 15% spandex, using a high-needle plain stitch, with a gram weight of 140 g / m 2 , and a width of 58 inches. The fabric is treated by beam dyeing and gradient setting processes and is finished with a hydrophilic auxiliary agent.
[0015] As can be seen from the descriptions of the various embodiments of the present invention above, compared with the prior art, the various embodiments of the present invention have the following
[0016] Advantages:
[0017] In the first technical solution and related embodiments, the preparation method adopts the copolymerization method. By copolymerizing polyethylene glycol, hydrophilic groups (-OH) are introduced, and the ratio of β-crystalline form to amorphous region is regulated through a multi-stage stretching-relaxation process, achieving a 1.5-fold increase in the moisture absorption of nylon fibers.
[0018] In the second technical solution and related embodiments, the crystallinity of ordinary nylon is about 50%. The copolymerization of hydrophilic organic substances disrupts the regularity of molecular chains and reduces the initial crystallinity of the yarn (from 50% → 45%). Polyethylene glycol increases the hydrophilic groups (-OH) in the amorphous region. The silane coupling agent enhances the binding force of the copolymer and prevents spinning breakage.
[0019] In the third technical solution and related embodiments, three-zone gradient heating ensures the melt uniformity. The specifications of the spinneret control the fiber fineness to match the nylon 40D / 34F specification. Compared with the ordinary process, the side-blowing process can rapidly cool to form low-crystallinity nascent fibers and inhibit the generation of α-type crystals.
[0020] In the fourth technical solution and related embodiments, the temperature of the first-stage hot stretching is 180°C for high-temperature stretching (50°C higher than the glass transition temperature of nylon), which fully disentangles the molecular chains to form an α-crystalline form orientation skeleton, and the crystallinity is increased from 45% to 50%, laying a structural foundation for subsequent crystal form transformation. An appropriate stretching rate can avoid filament breakage caused by excessive stress concentration of molecular chains.
[0021] In the fifth technical solution and related embodiments, water molecules in saturated steam at 90 - 100°C can penetrate the amorphous region, playing a plasticizing role, destroying the hydrogen bond network of the α-crystalline form, inducing the molecular chains to reconstruct into the β-crystalline form, and enhancing the moisture absorption. The stretching temperature is close to the critical temperature for the formation of the β-crystalline form, and the stretching ratio can promote the transformation from the α-crystalline form to the β-crystalline form in the plasticized state, resulting in the proportion of the β-crystalline form increasing to about 35%. High humidity during stretching can reduce the friction between molecular chains and reduce stretching stress damage.
[0022] In the sixth technical solution and related embodiments, the temperature oscillation from 120 - 60°C forms an "elastic crystal boundary" between the β-crystalline form and the amorphous region, which refers to a reversible stretching structure at the junction of the β-crystalline form and the amorphous region, allowing the molecular chains to reversibly stretch when the humidity changes. The high-temperature section promotes chain segment relaxation, and the low-temperature section freezes the metastable structure. The oscillation frequency matches the time scale of molecular chain conformation adjustment, and the total duration ensures the stabilization of the β-crystalline form, with the final proportion ≥ 40%. Tension control releases internal stress, maintains a slight tension to prevent shrinkage, and retains the orientation structure.
[0023] In the seventh technical solution and related embodiments, the winding and forming process ensures uniform forming of the yarn bobbin and avoids moisture absorption and moisture regain.
[0024] In the eighth technical solution and related embodiments, nanoporous silica is evenly dispersed in the fiber matrix to reflect external infrared rays and directly reflect infrared heat to the external space to avoid infrared heat accumulation on the surface. Titanium dioxide eliminates fiber gloss.
[0025] In the ninth technical solution and related embodiments, the β-crystal form is the result of rapid crystallization under the spinning process, providing yarn flexibility; the amorphous region is a state where the molecular chains do not have time to arrange into the crystalline region, which is the main channel for water diffusion and provides elastic recovery of the yarn. After dynamic relaxation, the proportion of the β-crystal form in the crystalline region becomes the majority, and the amorphous region also expands, providing more channels for water storage, and the nano-scale pores provide physical channels for water adsorption. The hygroscopicity is about 1.5 times higher than that of existing nylon yarns, achieving rapid moisture absorption and quick drying, greatly improving the cool feeling and thermal comfort.
[0026] In the tenth technical solution and related embodiments, the ratio of 85% nylon and 15% spandex achieves a balance between a fabric stretch recovery rate of 50% and moisture absorption and quick drying. The fabric is treated with a hydrophilic additive to achieve efficient water transfer. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0028] Figure 1 This is a schematic diagram of a β-crystal form of a highly hygroscopic nylon fiber according to an embodiment;
[0029] Figure 2 This is a schematic diagram of an α-crystal form of a highly hygroscopic nylon fiber according to an embodiment of the present invention. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are preferred embodiments of the present invention and should not be regarded as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0031] In the claims, description and the above-mentioned drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" etc. are for distinguishing different objects rather than for describing a specific order.
[0032] In the claims, description and above-mentioned drawings of the present invention, unless otherwise clearly defined, for orientation terms, such as the use of terms "center", "horizontal", "longitudinal", "level", "vertical", "top", "bottom", "inner", "outer", "upper", "lower", "front", "rear", "left", "right", "clockwise", "counterclockwise", etc. to indicate orientation or positional relationship are based on the orientation and positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, so it should not be construed as limiting the specific protection scope of the present invention.
[0033] In the claims, description and above-mentioned drawings of the present invention, unless otherwise clearly defined, if the terms "fixed connection" or "fixedly connected" are used, they should be understood in a broad sense, that is, any connection method without displacement relationship and relative rotation relationship between the two, that is to say, it includes non-removable fixed connection, removable fixed connection, being integrated as one body, and being fixedly connected through other devices or elements.
[0034] In the claims, description and above-mentioned drawings of the present invention, if the terms "comprise", "have" and their variants are used, they are intended to mean "including but not limited to".
[0035] See Figure 1 and Figure 2 , a preparation method of highly hygroscopic polyamide fiber, which realizes the improvement of fiber hygroscopic performance through the synergistic effect of introducing hydrophilic groups, regulating crystallinity and increasing the proportion of β-crystal form, and includes the following steps:
[0036] Step 1: Chemical modification
[0037] Carry out hydrophilic chemical modification on polyamide raw materials and blend them with ordinary polyamide. Specifically, use the copolymerization method to carry out hydrophilic chemical modification on polyamide raw materials. Copolymerize polyethylene glycol, terephthalic acid and caprolactam to form hydrophilic modified polyamide, and the dosage of polyethylene glycol is 3%. In the blend, the molar ratio of ordinary polyamide to modified polyamide is 9:1, and 0.5% of silane coupling agent KH-550 is added. In addition, reflective heat insulation particles and matting agents can also be added to the blend according to needs, where the reflective heat insulation particles are nano-porous silica and the matting agent is titanium dioxide. The nano-porous silica is uniformly dispersed in the fiber matrix, reflecting external infrared rays and directly reflecting the infrared heat to the external space to avoid the accumulation of infrared heat on the surface. Titanium dioxide eliminates the gloss of the fiber. Specifically, the particle size of the nano-porous silica is 5 nm, the pore diameter is 2 - 3 nm, and the addition amount is 5%. The addition amount of titanium dioxide is 1%.
[0038] In this embodiment, polyamide 6 is used for the polyamide. The crystallinity of ordinary polyamide is about 50%. The copolymerization of hydrophilic organic substances disrupts the regularity of the molecular chain and reduces the initial crystallinity of the yarn (from 50% → 45%). Polyethylene glycol increases the hydrophilic groups (-OH) in the amorphous region. The silane coupling agent enhances the binding force of the copolymer and prevents spinning breakage. Through chemical modification, hydrophilic groups (-OH) are introduced into the polyamide molecular chain to construct a core structure for water adsorption.
[0039] Step 2: Melt spinning
[0040] After melting by gradient heating, it is extruded through a spinneret and cooled to form nascent fibers. Specifically, a screw extruder is used for melt spinning, and a gradient heating method is adopted, with heating in three zones. The temperature in the first zone is 240 °C, the temperature in the second zone is 260 °C, and the temperature in the third zone is 265 °C to ensure the uniformity of the melt. A spinneret with a circular orifice is selected, with an orifice diameter of 0.18 mm and 34 holes to control the fiber fineness and match the polyamide 40D / 34F specification. Side blow cooling is used, with a cooling temperature of 17 - 19 °C, a humidity of 70 - 80%, and a wind speed of 0.4 m / s. Compared with the ordinary process, this side blow process can quickly cool to form nascent fibers with low crystallinity and inhibit the formation of α-type crystals.
[0041] Step 3: Primary hot drawing
[0042] Preliminary drawing is carried out at a temperature higher than the glass transition temperature of polyamide to induce the orientation of the α crystal form. Specifically, primary hot drawing is carried out at 180 °C, with a drawing ratio of 2.5 times and a drawing speed of 300 m / min.
[0043] Hot drawing at 180 °C (50 °C higher than the glass transition temperature of polyamide) can fully disentangle the molecular chains, form a skeletal structure with α crystal form orientation, and increase the crystallinity from 45% to 50%, laying a structural foundation for subsequent crystal form transformation. An appropriate drawing speed can avoid filament breakage caused by excessive stress concentration of the molecular chains.
[0044] Step 4: Secondary wet-heat drawing
[0045] Oriented induction of the transformation from α crystal form to β crystal form is carried out in a saturated steam environment. Specifically, secondary wet-heat drawing is carried out in a saturated steam environment at 90 - 100 °C, with a drawing ratio of 1.8 times and a humidity maintained at 100% RH.
[0046] The molecular chains of the α crystal form are arranged in a fully trans conformation in parallel, forming a dense monoclinic crystal system structure. The dense structure hinders the penetration of water molecules and has poor hygroscopicity; the molecular chains of the β crystal form have a twisted conformation, forming a pseudo-hexagonal crystal system structure. The loose structure allows water molecules to enter the amorphous region and has strong hygroscopicity.
[0047] Saturated steam water molecules at 90 - 100 °C can penetrate the amorphous region, playing a plasticizing role, breaking the hydrogen bond network of the α-crystalline form, inducing the molecular chain to reconstruct into the β-crystalline form, and enhancing the hygroscopicity. This stretching temperature is close to the critical temperature for the formation of the β-crystalline form. The stretching ratio can promote the transformation from the α-crystalline form to the β-crystalline form in the plasticized state, resulting in the proportion of the β-crystalline form increasing to about 35%. High humidity during stretching can reduce the friction between molecular chains and reduce tensile stress damage.
[0048] Step 5: Tertiary dynamic relaxation
[0049] Use temperature oscillation treatment to stabilize the β-crystalline form and expand the amorphous region. Specifically, use temperature oscillation treatment at 120 - 60 °C, with an oscillation frequency of 1 Hz, a period of 60 s, a total duration of 20 min, and a tension control of 0.5 cN / dtex. The temperature oscillation at 120 - 60 °C forms an "elastic crystal boundary" between the β-crystalline form and the amorphous region, that is, a reversible stretching structure at the junction of the β-crystalline form and the amorphous region, allowing the molecular chain to reversibly stretch when the humidity changes. The high-temperature section promotes the relaxation of chain segments, and the low-temperature section freezes the metastable structure. The oscillation frequency matches the time scale of molecular chain conformation adjustment, and the total duration ensures the stabilization of the β-crystalline form, with a final proportion of ≥40%. Tension control can release internal stress, maintain a micro-tension to prevent shrinkage, and retain the oriented structure.
[0050] Step 6: Winding and forming
[0051] Control the tension under constant temperature and moisture-proof conditions to complete the winding and forming of the fiber. Specifically, the winding speed is 3200 m / min, the winding tension is 18 - 22 cN, and the forming environment temperature is controlled at 25 °C to ensure uniform forming of the bobbin and avoid moisture absorption and moisture regain.
[0052] In this embodiment, the preparation method uses the copolymerization method, introducing hydrophilic groups (-OH) through polyethylene glycol copolymerization, and regulating the ratio of the β-crystalline form and the amorphous region through a multi-stage stretching-relaxation process to achieve an improvement in the hygroscopicity of nylon fibers.
[0053] A highly hygroscopic nylon fiber is made by the above preparation method, with a crystallinity of 35 - 42%, where the proportion of the β-crystalline form is 35 - 45%, and nano-scale pores with a size of 10 - 50 nm are distributed on the surface, and the moisture absorption rate reaches 1.15 times its own weight.
[0054] The β-crystalline form is the result of rapid crystallization under the spinning process, providing yarn flexibility; the amorphous region is the state where the molecular chain has no time to arrange into a crystalline region and is the main channel for water diffusion, providing yarn elastic recovery. After dynamic relaxation, the proportion of the β-crystalline form in the crystalline region becomes the majority, and the amorphous region also expands, bringing more channels for water storage. The nano-scale pores provide a physical channel for water adsorption. The hygroscopicity of this highly hygroscopic nylon fiber is about 1.5 times higher than that of existing nylon, achieving rapid moisture absorption and quick drying, and greatly improving the cool feeling and thermal and moisture comfort.
[0055] A fabric is prepared from the above-mentioned highly moisture-absorbent polyamide fiber. The fabric is treated by beam dyeing and gradient setting processes and finished with a hydrophilic auxiliary agent. The following is the specific preparation process.
[0056] 1. Fabric type
[0057] This fabric is a single-sided fabric with a high-needle weft plain stitch structure, with a weight of 140 g / m 2 , a width of 58 inches, and the fabric composition consists of 85% of the above-mentioned highly moisture-absorbent polyamide and 15% spandex.
[0058] 2. Selection of dyeing equipment
[0059] A beam dyeing machine is selected for dyeing operations. Among them, the high-temperature and high-pressure beam dyeing machine has significant advantages. The fabric dyed by it has a smooth and crisp surface and will not wrinkle during the dyeing process. Moreover, in the entire dyeing and finishing process, the fabric is not prone to common quality problems such as snagging, pressing damage, and "chicken claw pattern", which can effectively guarantee the quality of the dyed fabric.
[0060] 3. Dyeing formula
[0061] Water softener: NORM157, dosage is 0.35 g / L.
[0062] Sodium acetate: dosage is 0.5 g / L.
[0063] Leveling agent: ACID16, dosage is 1.5%.
[0064] Glacial acetic acid (HAC): dosage is 0.25 g / L.
[0065] Dye:
[0066] SNACIDYELLOWL058, dosage is 0.285%.
[0067] SNACIDREDL544, dosage is 0.046%.
[0068] SNACIDGREYL055, dosage is 0.360%.
[0069] Dyeing temperature: set at 98 °C.
[0070] Heat preservation time: maintained for 20 min.
[0071] Bath ratio: configured according to a ratio of 1:20.
[0072] 4. Type of setting machine
[0073] A Yuanxin Y7000 (J10) setting machine is selected, and this model uses natural gas as the energy supply.
[0074] 5. Finalization parameters
[0075] a. Embryo determination
[0076] Machine speed and temperature: Set the machine speed to 28m / min and the temperature to 205℃.
[0077] Rack overfeed: The rack overfeed length is 162cm and the overfeed ratio is 25%.
[0078] b. Drying + finished product + pre-shrinking
[0079] Machine speed and temperature: Set the machine speed to 35m / min and the temperature to 195℃.
[0080] Rack overfeed: The rack overfeed length is 164cm and the overfeed ratio is 20%.
[0081] 6. Functional additives process
[0082] Additives: Choose Huntsman HVD liq functional additive.
[0083] Process: The padding treatment method is adopted. HVD liq additive is formulated into a solution with a concentration of 10-50g / l, and the padding treatment is carried out at room temperature to ensure that the fabric has a liquid carrying rate of about 80-90%, followed by a drying operation.
[0084] The additive has the characteristics of hydrophilicity and softener. It can achieve efficient water transfer under ideal conditions, giving the fabric an extremely soft feel. At the same time, the stain removal of the fabric treated with it is significantly improved, and there is basically no tendency of thermal migration.
[0085] The moisture regain test results of the fabrics prepared in the above examples and the control sample (ordinary nylon fabric) were compared.
[0086] Table 1 Performance test results of the embodiment
[0087]
[0088] Note: The data in Table 1 are obtained according to the national standard test method.
[0089] The description of the above specification and embodiments is used to explain the protection scope of the present invention, but does not constitute a limitation on the protection scope of the present invention. Through the enlightenment of the present invention or the above embodiments, ordinary technicians in this field can obtain modifications, equivalent substitutions or other improvements to the embodiments of the present invention or part of the technical features thereof through logical analysis, reasoning or limited experiments, which should be included in the protection scope of the present invention.
Claims
1. A method for preparing highly moisture-absorbent polyamide fiber, characterized in that, It includes the following steps: Step 1, chemical modification: hydrophilic chemical modification is carried out on nylon raw materials and blended with ordinary nylon; Step 2, melt spinning: after melting by gradient heating, it is extruded through a spinneret and cooled to form nascent fibers; Step 3, primary hot stretching: preliminary stretching is carried out at a temperature higher than the glass transition temperature of nylon to induce α-crystalline orientation; Step 4, secondary wet-heat stretching: in a saturated steam environment, α-crystalline is directionally induced to transform into β-crystalline; Step 5, tertiary dynamic relaxation: temperature oscillation treatment is used to stabilize β-crystalline and expand the amorphous region; Step 6, winding and forming.
2. The preparation method of a highly moisture-absorbing polyamide fiber according to claim 1, characterized in that the steps The chemical modification in 1 adopts the copolymerization method, polyethylene glycol, terephthalic acid and caprolactam are copolymerized to form hydrophilic modified nylon, and a silane coupling agent is added; the dosage of polyethylene glycol is 3%; in the blend, the molar ratio of ordinary nylon to modified nylon is 9:1; the dosage of the silane coupling agent is 0.5%.
3. The preparation method of a highly moisture-absorbent polyamide fiber according to claim 1, characterized in that, The melt spinning in Step 2 uses a screw extruder. The gradient heating is divided into three zones. The temperature of the first zone is 240°C, the temperature of the second zone is 260°C, and the temperature of the third zone is 265°C; the hole shape of the spinneret is circular, the hole diameter is 0.18 mm, and the number of holes is 34; cooling is carried out by side blowing, with a temperature of 17 - 19°C, a humidity of 70 - 80%, and a wind speed of 0.4 m / s.
4. The preparation method of a highly moisture-absorbent polyamide fiber according to claim 1, characterized in that, The primary hot stretching in Step 3 is carried out at 180°C, the stretching ratio is 2.5 times, and the stretching rate is 300 m / min.
5. The preparation method of a highly moisture-absorbent polyamide fiber as described in claim 1, characterized in that, The secondary wet-heat stretching in Step 4 is carried out in a saturated steam environment at 90 - 100°C, the stretching ratio is 1.8 times, and the humidity is maintained at 100% RH.
6. The preparation method of a highly moisture-absorbing polyamide fiber as claimed in claim 1, characterized in that, The tertiary dynamic relaxation in Step 5 adopts a temperature oscillation of 120 - 60°C, an oscillation frequency of 1 Hz, a period of 60 s, a total duration of 20 min, and the tension is controlled at 0.5 cN / dtex.
7. The preparation method of a highly moisture-absorbent polyamide fiber as described in claim 1, characterized in that, In Step 6, fiber winding and forming are completed by controlling the tension under constant temperature and moisture-proof conditions; the winding speed is 3200 m / min, the winding tension is 18 - 22 cN, and the temperature of the forming environment is controlled at 25°C.
8. The preparation method of a highly moisture-absorbent polyamide fiber according to claim 2, characterized in that, In Step 1, it is suitable to add reflective heat-insulating particles and a matting agent to the blend. Among them, the reflective heat-insulating particles are nano-porous silica, and the matting agent is titanium dioxide.
9. A highly moisture-absorbent polyamide fiber, characterized in that, It is made by using the preparation method of a highly hygroscopic nylon fiber as described in any one of claims 1 to 8. The crystallinity of the nylon fiber is 35 - 42%, among which the proportion of β-crystalline is 35 - 45%, and there are 10 - 50 nm nano-scale pores on the surface.
10. A fabric, characterized in that, Interwoven with 85% of a highly moisture-absorbent polyamide fiber as described in claim 9 and 15% of spandex, using a high-needle plain stitch, with a weight of 140 g / m 2 , a width of 58 inches; the fabric is treated by beam dyeing and gradient setting processes and finished with a hydrophilic auxiliary agent.