A two-stage heat setting method for polyamide 6 DTY dyeing

Abstract

This invention discloses a two-stage heat-setting method for dyeing nylon 6 DTY, comprising: feeding nylon 6 DTY yarn into a sealed activation chamber containing organic solvent vapor, and performing swelling pretreatment through a hot flow of organic solvent vapor to obtain pre-activated yarn; transferring the pre-activated yarn to a liquid dye bath containing disperse dye, nonionic leveling agent, penetration promoter, and pH buffer system for low-temperature diffusion dyeing to obtain colored yarn; dehydrating the colored yarn and then sending it to a first heat-setting zone for dry heat setting to obtain pre-set yarn; and sending the pre-set yarn to a second heat-setting zone for relaxation heat treatment in a mixed flow containing gaseous silane components to obtain the finished set yarn. This invention can improve the dye penetration uniformity and heat-setting stability of nylon 6 DTY after dyeing, reduce dye migration, color spots, and heat shrinkage fluctuations, and improve the color fastness and dimensional stability of the yarn.

Description

Technical Field

[0001] This invention relates to the field of synthetic fiber dyeing and finishing technology, and in particular to a two-stage heat setting method for dyeing nylon 6 DTY. Background Technology

[0002] Nylon 6 DTY holds a significant market position in sportswear, high-end underwear, and industrial textiles due to its high strength, abrasion resistance, excellent elasticity, and soft hand feel. As the textile industry moves towards higher quality, greener practices, and functionalization, the market demands higher standards for the dyeing uniformity, colorfastness, and dimensional stability of nylon 6 DTY. Traditional nylon 6 DTY processing typically employs a dyeing-then-setting or dyeing-then-setting process, utilizing high temperature and pressure to promote dye molecule diffusion. However, with the increasingly widespread application of finer denier and porous fibers, existing technologies often struggle to balance the conflict between dyeing depth and fiber physical properties when processing high-performance nylon fabrics, leading to significant challenges in areas such as wash fastness, hand softness, and shrinkage control.

[0003] In existing technologies, dyeing nylon 6 DTY primarily relies on increasing the bath temperature to overcome the dense molecular packing structure in the amorphous regions of the fiber. However, simple physical heating easily leads to uneven fiber heating, resulting in severe warp defects or color differences. Furthermore, conventional single-stage heat setting processes often employ constant high temperatures for instantaneous treatment. While this method can initially fix the fiber dimensions, the high thermal sensitivity of nylon 6 molecular chains means that a single high-temperature impact can accumulate significant residual thermal stress within the fiber. When the fiber leaves the heat field, this incompletely released internal stress causes irreversible dimensional shrinkage and deformation of the fabric during subsequent wear or washing. In addition, during dry heat setting, dye molecules, lacking effective chemical or physical locking mechanisms, readily migrate to the fiber surface, resulting in a significant reduction in the surface color brightness of the finished yarn and a decrease in wet rubbing fastness and soaping fastness.

[0004] Currently, while some industry attempts have tried to improve dyeing results by adding chemical auxiliaries, most of these methods suffer from insufficient penetration and poor color fixation. Existing heat setting equipment typically has vague temperature control zones and lacks tension compensation and gradient transition mechanisms for fibers transitioning from a liquid to a gas phase environment. This technological gap causes the yarn to suffer severe mechanical friction and thermal shock during dehydration, drying, and setting, thereby damaging the microstructure of the fiber surface.

[0005] Developing a novel heat-setting method that can achieve deep activation of fiber molecular chains, precise control of dye spatial distribution, and improve dimensional stability through gradient stress release has become an urgent problem to be solved in the nylon dyeing and finishing industry. Summary of the Invention

[0006] The purpose of this invention is to provide a two-stage heat setting method for dyeing nylon 6 DTY, which solves at least one of the above-mentioned technical problems. It can improve the uniformity of dye penetration and heat setting stability after dyeing nylon 6 DTY, reduce dye migration, color spots and heat shrinkage fluctuations, and improve the color fastness and dimensional stability of yarn.

[0007] The embodiments of the present invention are implemented as follows:

[0008] A two-stage heat setting method for dyeing nylon 6 DTY, comprising:

[0009] S100, nylon 6 DTY yarn is fed into a sealed activation chamber containing organic solvent vapor. The yarn undergoes swelling pretreatment by the hot airflow of the organic solvent vapor to obtain pre-activated yarn.

[0010] S200, the pre-activated yarn is transferred to a liquid dyeing bath containing disperse dye, nonionic leveling agent, penetration promoter and pH buffer system, and low-temperature diffusion dyeing is performed to obtain colored yarn.

[0011] S300, the dyed yarn is dehydrated and then sent to the first heat setting zone for dry heat setting to obtain the initially set yarn.

[0012] S400, the initially set yarn is fed into the second heat set zone, which is connected in series with the first heat set zone. The yarn undergoes relaxation heat treatment in a mixed airflow containing gaseous silane components to obtain the set finished yarn.

[0013] In a preferred embodiment of the present invention, in the above-described two-stage heat setting method for dyeing nylon 6 DTY, in S100, the organic solvent vapor includes at least one of m-cresol vapor, benzyl alcohol vapor, and ethylene glycol butyl ether vapor.

[0014] The vapor concentration in the sealed activation chamber is 5% to 15%, the treatment temperature is 90°C to 110°C, the treatment time is 10s to 30s, and the running tension of the nylon 6DTY yarn in the sealed activation chamber is controlled at 0.05cN / dtex to 0.15cN / dtex.

[0015] Its technical effect is that by controlling the swelling and activation of nylon 6 DTY, the amorphous region of the fiber can form expansion channels that allow dye to enter in advance, thereby reducing the diffusion resistance in the subsequent dyeing stage.

[0016] In a preferred embodiment of the present invention, in the above-described two-stage heat setting method for dyeing nylon 6 DTY, in step S200,

[0017] The disperse dye is at least one of anthraquinone disperse dyes and azo disperse dyes, with a mass concentration of 0.8 g / L to 3.5 g / L.

[0018] The nonionic leveling agent is a polyoxyethylene ether-based nonionic leveling agent with a mass concentration of 2.0 g / L to 10.0 g / L.

[0019] The penetrant is an aliphatic penetrant with sulfonic acid groups, and the mass concentration is 1.0 g / L to 4.0 g / L.

[0020] The pH buffer system includes acetic acid and sodium acetate, and the pH value of the liquid phase staining bath is 4.8 to 6.2.

[0021] The temperature in the liquid phase dye bath is controlled between 50°C and 70°C.

[0022] Its technical effect is that, through the synergistic effect of low-temperature diffusion dyeing and buffer system, the dye can be uniformly introduced into the fiber under mild conditions, reducing surface overload and local enrichment, improving dyeing uniformity, and reducing the risk of color spots, color difference and dye migration.

[0023] In a preferred embodiment of the present invention, in the above-described two-stage heat setting method for dyeing nylon 6 DTY, in step S300, the colored yarn is sequentially passed through a liquid-pressing roller group and a liquid-equalizing guide roller group for dehydration treatment.

[0024] The linear pressure of the padding roller assembly is 0.15MPa to 0.45MPa, and the running tension of the colored yarn in the padding roller assembly is 0.05 cN / dtex to 0.18 cN / dtex. The free dye liquor on the surface of the colored yarn is squeezed out, and the liquid carry-over rate after padding is 20% to 35%.

[0025] The surface temperature of the liquid leveling guide roller group is 45℃~65℃, the wrap angle of the colored yarn on the liquid leveling guide roller group is 25°~65°, the running speed of the colored yarn in the liquid leveling guide roller group is 70 m / min~200 m / min, and the colored yarn after rolling is subjected to liquid film homogenization treatment.

[0026] The technical advantage lies in the following: if the liquid carryover rate is too high, a large amount of instantaneous vapor will be generated at high temperatures, causing dye migration (color spots) on the fiber surface; if it is too low, the dye will have difficulty migrating into the fiber under dry heat. By first squeezing out the free dye liquor and then homogenizing the residual liquid film, the liquid carryover state when entering the first heat setting zone is more stable. This not only avoids dye migration caused by instantaneous vaporization at high temperatures, but also reserves suitable liquid phase conditions for the directional migration of dye in subsequent heat setting.

[0027] In a preferred embodiment of the present invention, in the above-described two-stage heat setting method for dyeing nylon 6 DTY, in S300, the first heat setting zone adopts a hot air circulation dry heat setting structure.

[0028] The temperature of the first heat setting zone is 175℃~195℃, and the hot air velocity is 1.5m / s~4.5m / s.

[0029] The operating tension in the first heat setting zone is 0.10 cN / dtex to 0.25 cN / dtex, and the operating speed is 80 m / min to 220 m / min.

[0030] The first heat setting zone is equipped with a flow guiding and shaping plate and a partitioned dehumidification port. The colored yarn is hot-air circulating and setting in a dry and hot environment to obtain the initially set yarn.

[0031] Its technical effect is that the initial structure of the yarn is locked and the internal stress is reorganized through the first stage of dry heat setting, so that the dye forms a relatively stable distribution inside the fiber.

[0032] In a preferred embodiment of the present invention, in the above-described two-stage heat setting method for dyeing nylon 6 DTY, a buffer transition section is provided between the first heat setting zone and the second heat setting zone, and the initially set yarn enters the second heat setting zone after passing through the buffer transition section.

[0033] The buffer transition section is set along the tensioning path of the initial shaping yarn.

[0034] The length of the buffer transition section is 0.8 m to 2.5 m, the ambient temperature is 120℃ to 160℃, and the relative humidity is 10% to 35%. A temperature gradient transition is performed before the initially shaped yarn enters the second heat-setting zone.

[0035] Its technical effect is that by setting a buffer transition zone for temperature and humidity, it avoids the sudden cooling and heating shock caused by the initial heat-setting yarn directly entering the second heat-setting zone, so that the yarn stress release is more gradual, reducing shrinkage fluctuations and structural unevenness.

[0036] In a preferred embodiment of the present invention, in the above-described two-stage heat setting method for dyeing nylon 6 DTY, in S400, the mixed gas flow includes an inert carrier gas, water vapor, and a gaseous silane component.

[0037] The volume fraction of gaseous silane in the mixed gas stream is 0.2% to 1.2%, the volume fraction of water vapor is 0.8% to 3.0%, and the remainder is inert carrier gas.

[0038] The gaseous silane component is selected from at least one of methyltriethoxysilane, vinyltriethoxysilane, and aminopropyltriethoxysilane.

[0039] Its technical effect is that, through the synergistic effect of gaseous silane components and water vapor, a denser and more stable interface is formed on the yarn surface, which inhibits the migration path of residual dyes and improves the color fastness and surface durability of the yarn.

[0040] In a preferred embodiment of the present invention, in the above-described two-stage heat setting method for dyeing nylon 6 DTY, in S400, the initial setting yarn is in an overfeed operation state when it enters the second heat setting zone, with an overfeed rate of 3% to 8%.

[0041] The temperature of the second heat-setting zone is 145℃~175℃, and the velocity of the mixed airflow is 1.0 m / s~3.5 m / s.

[0042] The operating tension in the second heat setting zone is 0.06 cN / dtex to 0.18 cN / dtex, and the operating speed is 60 m / min to 180 m / min.

[0043] The second heat setting zone is equipped with segmented air supply outlets, side air supply outlets, and tail exhaust outlets.

[0044] Its technical effect is that by combining overfeed relaxation with segmented airflow, the residual stress of the initially set yarn is fully released in the second heat set zone and the final structural integration is completed, reducing shrinkage difference, abnormal crimping and subsequent thermal dimensional drift.

[0045] In a preferred embodiment of the present invention, in the above-described two-stage heat setting method for dyeing nylon 6 DTY, the first heat setting zone, the buffer transition zone, and the second heat setting zone are arranged sequentially on the same continuous conveyor line.

[0046] The continuous conveyor line includes independent temperature-controlled housings respectively corresponding to the first heat-setting zone, the buffer transition section, and the second heat-setting zone.

[0047] A partition air curtain assembly is provided between adjacent independent temperature control housings to reduce airflow exchange between adjacent temperature zones.

[0048] An online tension adjustment component is provided in the buffer transition section. The online tension adjustment component includes an active yarn feeding roller, a driven yarn stabilizing roller, and a tension detection roller. A yarn path is formed between the active yarn feeding roller and the driven yarn stabilizing roller. The tension of the initially set yarn is adjusted and the path is guided during the conveying process from the first heat setting zone to the second heat setting zone.

[0049] Its technical advantages are: through continuous conveying and temperature zone isolation and coordinated control, the yarn can achieve stable transfer and tension closed-loop adjustment between the two heat setting stages, reducing fluctuations caused by manual transfer and improving the continuity of the entire line operation and the consistency of the process.

[0050] In a preferred embodiment of the present invention, in the two-stage heat setting method for dyeing nylon 6 DTY described above, after S400 is completed, the finished yarn is sequentially sent to the first-stage cooling section and the second-stage cooling section for graded cooling, and then wound.

[0051] The primary cooling section uses cold air at 15°C to 25°C to perform primary cooling on the finished yarn.

[0052] The secondary cooling section uses balanced air at 25°C to 35°C to perform secondary cooling on the finished yarn after primary cooling, controlling the surface temperature of the finished yarn to not exceed 50°C when it enters the winding station.

[0053] Its technical effect is that by using a graded cooling method of rapid cooling followed by balanced slow cooling, the heat-set yarn structure is fully frozen and thermal stress is relieved before winding, reducing shrinkage, adhesion and shape rebound after winding, and improving the stability of finished product storage and transportation.

[0054] The beneficial effects of the embodiments of the present invention are:

[0055] This invention relates to a two-stage heat-setting method for dyeing nylon 6 DTY. By continuously and synergistically designing nylon 6 DTY dyeing and two-stage heat setting, a progressive processing chain is formed along the process path: pre-activation—diffusion dyeing—preliminary locking—secondary relaxation—graded cooling. This allows the fiber to complete swelling control, dye penetration, microstructure restructuring, and residual stress release at different stages. Compared to single-stage heat setting or direct high-temperature fixation, this invention can more fully utilize the adjustable space of the fiber's amorphous region, improve the uniformity of dye molecule penetration into the fiber interior, reduce surface enrichment and color unevenness, thereby improving dyeing depth, dyeing uniformity, and overall color fastness. It is particularly beneficial for improving color fading, migration, and batch fluctuations in nylon 6 DTY during subsequent use and processing.

[0056] This invention discloses a two-stage heat-setting method for dyeing nylon 6 DTY. In the first heat-setting zone, a dry heat cycling method is used to initially fix the structure of the dyed yarn, allowing the fibers to complete initial thermal shrinkage and microcrystalline rearrangement under high temperature and controllable tension. This suppresses abnormal crimping, dimensional shrinkage, and localized deformation caused by stress imbalance within the dyed yarn. A buffer transition zone provides a gradient transition in temperature and humidity. Then, in the second heat-setting zone, a mixed airflow containing gaseous silane components is introduced for relaxation heat treatment, forming a more stable barrier layer on the fiber surface and further releasing residual thermal stress. This two-stage synergistic mechanism makes the thermal response of the outer and inner layers of the yarn more consistent, effectively reducing shrinkage differences, width fluctuations, and inconsistent hand feel after heat setting, and improving the dimensional stability, appearance stability, and post-processing adaptability of the finished yarn.

[0057] This invention presents a two-stage heat-setting method for dyeing nylon 6DTY. By coordinating the processes of liquid removal, liquid leveling rollers, continuous conveying, temperature zone isolation, and staged cooling, it reduces uneven heat setting and energy waste caused by excessive dye liquor carryover. Continuous operation is achieved through online tension adjustment and segmented temperature control, reducing the need for manual intervention and the risk of fluctuations caused by process changes. The process of this invention is seamless, and the equipment configuration is relatively simplified. It can reduce dye liquor residue, rework rate, and energy loss while ensuring setting effect, thereby improving production efficiency and process stability. It is suitable for large-scale continuous processing of nylon 6DTY after dyeing. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0059] This invention provides a two-stage heat setting method for dyeing nylon 6 DTY, comprising: S100, feeding nylon 6 DTY yarn into a sealed activation chamber containing organic solvent vapor, wherein the organic solvent is converted into an aerosol state by ultrasonic atomization or thermal flash evaporation system, so that it is uniformly dispersed inside the chamber and a constant vapor pressure is maintained, and swelling pretreatment is performed by the hot flow of the organic solvent vapor, inducing moderate breakage of hydrogen bonds between nylon 6 molecular chains and generating a microporous effect, so that the macromolecular chain segments in the amorphous region of the fiber change from a tightly packed state to a loose metastable state, thereby obtaining pre-activated yarn; S200, transferring the pre-activated yarn to a liquid phase dye bath containing disperse dye, nonionic leveling agent, penetration promoter and pH buffer system, wherein the metastable microstructure generated after activation guides dye molecules to penetrate into the fiber cortex through capillary effect without the need for high temperature and high pressure, and during the dyeing process, the yarn passes through the fiber by alternating immersion and pressing with multiple rollers. In step S300, the dye bath is used to increase the exchange frequency of the dye solution inside the yarn bundle, and low-temperature diffusion dyeing is performed to obtain dyed yarn; in step S400, the dyed yarn is dehydrated and then sent to the first heat setting zone for dry heat setting. Through instantaneous high-temperature impact, the dye molecules are driven to further penetrate from the fiber surface to the core layer, and the heat energy is used to promote the reconstruction of the fiber microcrystalline structure, and the initial crystallization and reorganization are completed simultaneously, encapsulating and locking the dye molecules in the fiber macromolecular skeleton to obtain the initially set yarn; in step S400, the initially set yarn is sent to the second heat setting zone, which is set in series with the first heat setting zone. Relaxation heat treatment is performed in a mixed airflow containing gaseous silane components. The hydrolysis and condensation reaction of silane components in a humid and hot environment is used to build a nanoscale cross-linked protective network in situ on the fiber surface, thereby eliminating residual thermal stress and blocking the dye migration path to obtain the set finished yarn.

[0060] In S100, the organic solvent vapor includes at least one of m-cresol vapor, benzyl alcohol vapor, and ethylene glycol butyl ether vapor; the vapor concentration in the sealed activation chamber is 5% to 15%, the treatment temperature is 90°C to 110°C, and the treatment time is 10s to 30s. In order to ensure that the solvent molecules penetrate the yarn bundle uniformly in a very short time, a forced convection fan is provided in the chamber, and the dynamic balance of the concentration field is ensured by hot air circulation. The running tension of the nylon 6DTY yarn in the sealed activation chamber is controlled at 0.05cN / dtex to 0.15cN / dtex.

[0061] Its technical effect is that by controlling the swelling and activation of nylon 6 DTY, the amorphous region of the fiber can form expansion channels that allow dye to enter in advance, thereby reducing the diffusion resistance in the subsequent dyeing stage.

[0062] In S200, the disperse dye is at least one of anthraquinone disperse dyes and azo disperse dyes, with a mass concentration of 0.8 g / L to 3.5 g / L; the nonionic leveling agent is a polyoxyethylene ether nonionic leveling agent with a mass concentration of 2.0 g / L to 10.0 g / L; the penetrant is an aliphatic penetrant with sulfonic acid groups, with a mass concentration of 1.0 g / L to 4.0 g / L; the pH buffer system includes acetic acid and sodium acetate, and the pH value of the liquid phase dye bath is 4.8 to 6.2; the temperature in the liquid phase dye bath is controlled at 50°C to 70°C.

[0063] Its technical effect is that, through the synergistic effect of low-temperature diffusion dyeing and buffer system, the dye can be uniformly introduced into the fiber under mild conditions, reducing surface overload and local enrichment, improving dyeing uniformity, and reducing the risk of color spots, color difference and dye migration.

[0064] In step S300, the colored yarn is sequentially passed through a liquid-pressing roller group and a liquid-leveling guide roller group for dehydration treatment. The linear pressure of the liquid-pressing roller group is 0.15MPa to 0.45MPa, and the running tension of the colored yarn in the liquid-pressing roller group is 0.05 cN / dtex to 0.18 cN / dtex, which removes the free dye liquor from the surface of the colored yarn, resulting in a liquid carry-over rate of 20% to 35% after pressing. The surface temperature of the liquid-leveling guide roller group is 45℃ to 65℃, the wrap angle of the colored yarn on the liquid-leveling guide roller group is 25° to 65°, and the running speed of the colored yarn in the liquid-leveling guide roller group is 70 m / min to 200 m / min, which performs liquid film homogenization treatment on the pressed colored yarn. The surface of the liquid distribution guide roller assembly is covered with an ultra-fine porous hydrophilic ceramic layer, which can correct local differences in the roll-up rate through physical adsorption and secondary distribution, ensuring that the difference in liquid film thickness distribution in the circumferential direction of the yarn is less than 2%.

[0065] The technical advantage lies in the following: if the liquid carryover rate is too high, a large amount of instantaneous vapor will be generated at high temperatures, causing dye migration (color spots) on the fiber surface; if it is too low, the dye will have difficulty migrating into the fiber under dry heat. By first squeezing out the free dye liquor and then homogenizing the residual liquid film, the liquid carryover state when entering the first heat setting zone is more stable. This not only avoids dye migration caused by instantaneous vaporization at high temperatures, but also reserves suitable liquid phase conditions for the directional migration of dye in subsequent heat setting.

[0066] In S300, the first heat setting zone adopts a hot air circulation dry heat setting structure; the temperature of the first heat setting zone is 175℃~195℃, and the hot air speed is 1.5m / s~4.5m / s; the operating tension in the first heat setting zone is 0.10cN / dtex~0.25cN / dtex, and the operating speed is 80m / min~220m / min; the hot air is vertically sprayed onto the yarn path through a slit nozzle driven by a variable frequency fan to form a highly efficient turbulent heat exchange effect, quickly remove moisture, and induce polyamide molecular chain segment recombination; the first heat setting zone is equipped with a flow guiding and shaping plate and a partitioned dehumidification port, and the colored yarn is hot air circulated and set in a dry heat environment to obtain the initially set yarn.

[0067] Its technical effect is that the initial structure of the yarn is locked and the internal stress is reorganized through the first stage of dry heat setting, so that the dye forms a relatively stable distribution inside the fiber.

[0068] A buffer transition section is provided between the first heat-setting zone and the second heat-setting zone. The initially set yarn enters the second heat-setting zone after passing through the buffer transition section. The buffer transition section is set along the tensioning path of the initially set yarn. The length of the buffer transition section is 0.8 m to 2.5 m, the ambient temperature is 120℃ to 160℃, and the ambient relative humidity is 10% to 35%. The microenvironment humidity is adjusted in real time by an adaptive high-frequency humidification spray head to balance the moisture gradient inside and outside the fiber, prevent the fiber surface from becoming brittle due to excessive dryness and generate static electricity accumulation, and perform a temperature gradient transition before the initially set yarn enters the second heat-setting zone.

[0069] Its technical effect is that by setting a buffer transition zone for temperature and humidity, it avoids the sudden cooling and heating shock caused by the initial heat-setting yarn directly entering the second heat-setting zone, so that the yarn stress release is more gradual, reducing shrinkage fluctuations and structural unevenness.

[0070] In S400, the mixed gas flow includes an inert carrier gas, water vapor, and a gaseous silane component. The volume fraction of the gaseous silane component in the mixed gas flow is 0.2%–1.2%, the volume fraction of the water vapor is 0.8%–3.0%, and the remainder is the inert carrier gas. The gaseous silane component is selected from at least one of methyltriethoxysilane, vinyltriethoxysilane, and aminopropyltriethoxysilane. This gaseous component is injected into an independent vaporization chamber via a high-precision electronic metering pump and introduced into the setting zone along with the preheated inert carrier gas. Under heated conditions, it undergoes a de-alcoholization condensation reaction with the residual hydroxyl or terminal amide groups on the surface of the initially set yarn to form a covalently bonded hydrophobic layer.

[0071] Its technical effect is that, through the synergistic effect of gaseous silane components and water vapor, a denser and more stable interface is formed on the yarn surface, which inhibits the migration path of residual dyes and improves the color fastness and surface durability of the yarn.

[0072] In S400, the initially set yarn is in an overfeed state when it enters the second heat setting zone, with an overfeed rate of 3% to 8%; the temperature of the second heat setting zone is 145℃ to 175℃, and the velocity of the mixed airflow is 1.0 m / s to 3.5 m / s; the operating tension in the second heat setting zone is 0.06 cN / dtex to 0.18 cN / dtex, and the operating speed is 60 m / min to 180 m / min; the second heat setting zone is equipped with segmented air inlets, lateral air inlets, and tail-end exhaust inlets; the second heat setting zone is equipped with cross-blowing air channels, which induce controlled radial vibration of the yarn bundle by alternating the direction of the airflow jet, accelerating the molecular chain segments to return to thermodynamic steady state and eliminating torque stress during processing.

[0073] Its technical effect is that by combining overfeed relaxation with segmented airflow, the residual stress of the initially set yarn is fully released in the second heat set zone and the final structural integration is completed, reducing shrinkage difference, abnormal crimping and subsequent thermal dimensional drift.

[0074] The first heat-setting zone, the buffer transition section, and the second heat-setting zone are sequentially arranged on the same continuous conveyor line. The continuous conveyor line includes independent temperature-controlled housings corresponding to the first heat-setting zone, the buffer transition section, and the second heat-setting zone, respectively. A separating air curtain assembly is provided between adjacent independent temperature-controlled housings to reduce airflow exchange between adjacent temperature zones. The air curtain adopts a laminar flow blowing mode, forming a local high-pressure air curtain at the housing connection slit, effectively preventing the dry, hot air of the first zone from interpenetrating with the silane-containing mixed gas of the second zone and preventing thermal interference. An online tension adjustment assembly is provided within the buffer transition section. The online tension adjustment assembly includes an active yarn feeding roller, a driven yarn stabilizing roller, and a tension detection roller. A yarn path is formed between the active yarn feeding roller and the driven yarn stabilizing roller, adjusting the tension and guiding the path of the initially set yarn during its conveying process from the first heat-setting zone to the second heat-setting zone.

[0075] Its technical advantages are: through continuous conveying and temperature zone isolation and coordinated control, the yarn can achieve stable transfer and tension closed-loop adjustment between the two heat setting stages, reducing fluctuations caused by manual transfer and improving the continuity of the entire line operation and the consistency of the process.

[0076] After S400 is completed, the finished yarn is sequentially fed into a primary cooling section and a secondary cooling section for graded cooling before winding. The primary cooling section uses cold air at 15°C to 25°C to perform primary cooling on the finished yarn. The secondary cooling section uses balanced air at 25°C to 35°C to perform secondary cooling on the finished yarn after primary cooling, controlling the surface temperature of the finished yarn to not exceed 50°C when it enters the winding station. During the graded cooling process, cooling ducts are arranged around the yarn path, providing an all-around cooling field through honeycomb porous diffusers, and simultaneously spraying a fine emulsion of antistatic oil to restore the lubricity of the fiber surface.

[0077] Its technical effect is that by using a graded cooling method of rapid cooling followed by balanced slow cooling, the heat-set yarn structure is fully frozen and thermal stress is relieved before winding, reducing shrinkage, adhesion and shape rebound after winding, and improving the stability of finished product storage and transportation.

[0078] To further illustrate the technical means of the present invention, three representative embodiments and a comparative example are given below.

[0079] Specific implementation examples provided by the present invention are shown in Table 1, with 70D / 48F nylon 6 DTY yarn selected as the experimental object.

[0080] Table 1: Components and Process Parameters of a Two-Stage Heat Setting Method for Dyeing Nylon 6DTY

[0081]

[0082] (1) Experimental steps of Examples 1-3

[0083] Swelling pretreatment: Nylon 6DTY yarn is fed into a closed activation chamber, where an ultrasonic atomization system converts the organic solvent into an aerosol state and maintains a constant vapor pressure. Under a specified operating tension, the yarn is pre-activated by a hot flow of organic solvent vapor, inducing fiber molecular chain recombination.

[0084] Low-temperature diffusion dyeing: The pre-activated yarn is transferred to a liquid dye bath. The yarn passes through the dye bath by alternating immersion with multiple rollers, which increases the exchange frequency of the dye solution inside the yarn bundle. Diffusion dyeing is carried out under conditions of 50°C to 70°C.

[0085] Liquid removal and dry heat setting: The colored yarn passes through the liquid-absorbing roller group and the liquid-equalizing guide roller group with an ultra-fine microporous hydrophilic ceramic layer on the surface in sequence. After the liquid content is precisely controlled at 20% to 35%, it is sent into the first heat setting zone for dry heat setting to initially lock the fiber structure.

[0086] Relaxation heat treatment: After the initial set yarn is cooled in the buffer transition section, it enters the second heat set zone in an overfeed state. The gaseous silane component undergoes a de-alcoholization condensation reaction with water vapor in the mixed airflow, and a nano-level cross-linked protective network is built in situ on the fiber surface. The residual stress is released simultaneously to obtain the finished yarn.

[0087] Staged cooling: The finished yarn is cooled to below 50°C by first-stage cold air and second-stage balanced air before being wound.

[0088] (2) Experimental steps for the comparative example

[0089] The raw 6DTY nylon yarn was placed in a conventional high-temperature and high-pressure dyeing vat and dyed at 120°C for 30 minutes. After dyeing, it was centrifuged and dehydrated without homogenization treatment and then dried. Subsequently, it was sent to a single-stage dry heat setting machine for setting at 185°C. The operating tension was set to 0.3cN / dtex, without overfeeding treatment or silane gas phase treatment.

[0090] (3) Performance testing steps

[0091] Dyeing uniformity test: Ten test points were randomly selected on the same batch of finished yarns using a spectrophotometer to measure the K / S value and calculate its coefficient of variation (CV).

[0092] Color fastness testing: Wash fastness was tested according to GB / T3921 standard, and wet rubbing fastness was tested according to GB / T3920 standard to evaluate its wash resistance and abrasion resistance.

[0093] Dimensional stability test: The length is... The yarn was soaked in boiling water for 30 minutes, then removed, dried, and its length was measured. Calculate the boiling water shrinkage rate .

[0094] Surface morphology observation: Use scanning electron microscopy (SEM) to observe whether a uniform silane cross-linked film has formed on the yarn surface.

[0095] Table 2: Performance Test Results Comparison Table

[0096]

[0097] The performance test results are shown in Table 2.

[0098] The example group achieved higher K / S values ​​at lower temperatures. Solvent vapor pre-activation broke down the dense molecular packing of nylon 6, and the resulting expanded channels significantly improved dye uptake efficiency.

[0099] The CV value of the embodiment decreased by more than 60% compared with the comparative example, which proves that the liquid equalization guide roller group can accurately control the liquid film thickness and effectively eliminate the dye migration phenomenon during high-temperature setting.

[0100] The comparative example had a significantly higher boiling water shrinkage rate due to the lack of overfeed relaxation; while the example, through two-stage gradient shaping and overfeed operation, fully released the internal thermal stress of the fiber, giving the product excellent dimensional stability.

[0101] The high fastness performance of the examples confirms that the cross-linked protective layer formed by the gaseous silane component constructs a physical barrier on the fiber surface, which greatly inhibits the outward migration of dye in a wet environment.

[0102] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A two-stage heat setting method for dyeing nylon 6 DTY, characterized in that, include: S100, Nylon 6 DTY yarn is fed into a closed activation chamber, which contains organic solvent vapor. The yarn is pre-treated by the hot airflow of the organic solvent vapor to obtain pre-activated yarn. S200, the pre-activated yarn is transferred to a liquid dyeing bath, which contains disperse dye, nonionic leveling agent, penetration promoter and pH buffer system, and low-temperature diffusion dyeing is performed to obtain colored yarn; S300, the dyed yarn is dehydrated and then sent to the first heat setting zone for dry heat setting to obtain the initially set yarn; S400, the initially set yarn is fed into the second heat set zone, which is connected in series with the first heat set zone. The yarn undergoes relaxation heat treatment in a mixed airflow containing gaseous silane components to obtain the set finished yarn.

2. The two-stage heat setting method for dyeing nylon 6DTY according to claim 1, characterized in that, In S100, the organic solvent vapor includes at least one of m-cresol vapor, benzyl alcohol vapor, and ethylene glycol butyl ether vapor; The vapor concentration in the sealed activation chamber is 5% to 15%, the treatment temperature is 90°C to 110°C, the treatment time is 10s to 30s, and the running tension of the nylon 6DTY yarn in the sealed activation chamber is controlled at 0.05cN / dtex to 0.15cN / dtex.

3. The two-stage heat setting method for dyeing nylon 6DTY according to claim 1, characterized in that, In S200, The disperse dye is at least one of anthraquinone disperse dyes and azo disperse dyes, with a mass concentration of 0.8 g / L to 3.5 g / L; The nonionic leveling agent is a polyoxyethylene ether-based nonionic leveling agent with a mass concentration of 2.0 g / L to 10.0 g / L. The penetrant is an aliphatic penetrant with sulfonic acid groups, and its mass concentration is 1.0 g / L to 4.0 g / L; The pH buffer system includes acetic acid and sodium acetate, and the pH value of the liquid phase staining bath is 4.8 to 6.2; The temperature in the liquid phase dye bath is controlled between 50°C and 70°C.

4. The two-stage heat setting method for dyeing nylon 6DTY according to claim 1, characterized in that, In S300, the colored yarn is sequentially passed through a liquid-removing roller group and a liquid-equalizing guide roller group for dehydration treatment. The linear pressure of the padding roller assembly is 0.15MPa to 0.45MPa, and the running tension of the colored yarn in the padding roller assembly is 0.05 cN / dtex to 0.18 cN / dtex. The free dye liquor on the surface of the colored yarn is squeezed out, and the liquid carry-over rate after padding is 20% to 35%. The surface temperature of the liquid leveling guide roller group is 45℃~65℃, the wrap angle of the colored yarn on the liquid leveling guide roller group is 25°~65°, the running speed of the colored yarn in the liquid leveling guide roller group is 70 m / min~200 m / min, and the colored yarn after rolling is subjected to liquid film homogenization treatment.

5. The two-stage heat setting method for dyeing nylon 6DTY according to claim 1, characterized in that, In S300, the first heat setting zone adopts a hot air circulation dry heat setting structure; The temperature of the first heat-setting zone is 175℃~195℃, and the hot air velocity is 1.5m / s~4.5m / s; The operating tension in the first heat setting zone is 0.10 cN / dtex to 0.25 cN / dtex, and the operating speed is 80 m / min to 220 m / min; The first heat setting zone is equipped with a flow guiding and shaping plate and a partitioned dehumidification port. The colored yarn is hot-air circulating and setting in a dry and hot environment to obtain the initially set yarn.

6. The two-stage heat setting method for dyeing nylon 6DTY according to claim 1, characterized in that, A buffer transition section is provided between the first heat setting zone and the second heat setting zone, and the initially set yarn enters the second heat setting zone after passing through the buffer transition section; The buffer transition section is set along the tensioning path of the initially shaped yarn; The length of the buffer transition section is 0.8 m to 2.5 m, the ambient temperature is 120℃ to 160℃, and the relative humidity is 10% to 35%. A temperature gradient transition is performed before the initially shaped yarn enters the second heat-setting zone.

7. The two-stage heat setting method for dyeing nylon 6DTY according to claim 1, characterized in that, In S400, the mixed gas flow includes an inert carrier gas, water vapor, and a gaseous silane component; The volume fraction of gaseous silane in the mixed gas stream is 0.2% to 1.2%, the volume fraction of water vapor is 0.8% to 3.0%, and the remainder is inert carrier gas; The gaseous silane component is selected from at least one of methyltriethoxysilane, vinyltriethoxysilane, and aminopropyltriethoxysilane.

8. The two-stage heat setting method for dyeing nylon 6DTY according to claim 1, characterized in that, In S400, the initially set yarn is in an overfeed operation state when it enters the second heat set zone, with an overfeed rate of 3% to 8%. The temperature of the second heat-setting zone is 145℃~175℃, and the velocity of the mixed airflow is 1.0 m / s~3.5 m / s; The operating tension in the second heat-setting zone is 0.06 cN / dtex to 0.18 cN / dtex, and the operating speed is 60 m / min to 180 m / min; The second heat setting zone is equipped with segmented air supply outlets, side air supply outlets, and tail exhaust outlets.

9. The two-stage heat setting method for dyeing nylon 6DTY according to claim 6, characterized in that, The first heat setting zone, the buffer transition section, and the second heat setting zone are arranged sequentially on the same continuous conveyor line; The continuous conveyor line includes independent temperature-controlled housings respectively corresponding to the first heat-setting zone, the buffer transition section and the second heat-setting zone; A partition air curtain assembly is provided between adjacent independent temperature control housings; An online tension adjustment component is installed within the buffer transition section.

10. The two-stage heat setting method for dyeing nylon 6DTY according to claim 1, characterized in that, After S400 is completed, the shaped finished yarn is sequentially sent to the first-level cooling section and the second-level cooling section for graded cooling, and then wound. The primary cooling section uses cold air at 15°C to 25°C to perform primary cooling on the finished yarn. The secondary cooling section uses balanced air at 25°C to 35°C to perform secondary cooling on the finished yarn after primary cooling, controlling the surface temperature of the finished yarn to not exceed 50°C when it enters the winding station.

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