Preparation method of regenerated ultralow-shrinkage black polyester staple fiber

Abstract

The invention discloses a preparation method of regenerated ultra-low shrinkage black polyester staple fibers, and relates to the technical field of polymer waste recovery and regeneration, the preparation method comprises the steps of raw material mixing, drying treatment, spinning forming, post-treatment section, curling and cutting and finished product treatment, and when the shrinkage rate of the regenerated polyester staple fibers is controlled, the shrinkage rate of the regenerated polyester staple fibers is controlled by establishing a gradient temperature regulation and control program. Differentiated heat setting paths are set according to different regenerated raw material components, so that the accuracy of eliminating the internal stress of the fiber is ensured, the problem of abnormal shrinkage caused by local thermal stress concentration is avoided, the stability of the ultralow shrinkage performance of the fiber is ensured, and the size reliability of a product is improved; when fiber in-situ coloring and structure strengthening are carried out, synchronous achievement of color uniformity and ultra-low shrinkage characteristics is guaranteed by synchronously tracking the dispersion state of color master batches and crystallization dynamic evolution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer waste recycling, and particularly relates to a preparation method of regenerated ultra-low-shrinkage black polyester staple fiber. BACKGROUND

[0002] The regenerated polyester staple fiber is made of waste polyester bottle pieces and spinning waste silk through physical and chemical regeneration processes. The key production process includes waste bottle piece crushing, cleaning, drying, melting, spinning and drafting. The production process is more energy-saving than traditional chemical fibers. As a carrier of resource recycling, the regenerated polyester staple fiber can save petroleum resources and reduce carbon emissions. The material is widely used in non-woven fields such as automobile interior, home textile filling and sound-absorbing materials.

[0003] At present, in the production process of the regenerated ultra-low-shrinkage black polyester staple fiber, there are multiple processes such as spinning, drafting and heat setting. When the fiber shrinkage rate is controlled, the heat treatment system acts on the internal structure of the fiber, and the change state of the fiber molecular chain orientation and crystallization behavior cannot be monitored in real time. When the local thermal stress distribution of the fiber is uneven or the cooling gradient fluctuates in the heat setting stage, the axial shrinkage rate of the fiber may abnormally increase, resulting in that the boiling water shrinkage rate of the finished fiber exceeds the design threshold, and the fiber size stability is reduced.

[0004] Therefore, the present application provides a preparation method of regenerated ultra-low-shrinkage black polyester staple fiber to solve the above problems. SUMMARY

[0005] The main purpose of the present application is to provide a preparation method of regenerated ultra-low-shrinkage black polyester staple fiber to solve the problems in the above background.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a preparation method of regenerated ultra-low-shrinkage black polyester staple fiber, comprising the following steps: Step one: raw material mixing, selecting PET clean bottle pieces 70-80%, bubble material 20-30% by mass percentage, and adding black color masterbatch 3-5% after mixing; Step two: drying treatment, placing the mixed raw materials in an electric heating continuous drying system, controlling the dew point to be less than or equal to -40 DEG C, and drying to a water content of less than or equal to 30 ppm; Step three: spinning forming, melting the dried raw material by a screw extruder, the melt temperature is 260-270 DEG C, and the melt is filtered by a double-stage melt filter and then enters a spinning box; the melt is delivered to a spinneret by a metering pump to extrude a primary fiber, which is cooled by 20-30 DEG C circular air and oiled to form a barrel-packed raw yarn; Step four: post-treatment section, the barrel-packed raw yarn is bundled and then subjected to the following processes: primary drafting: drafting in an oil-water bath at 65-70 DEG C, the drafting multiple accounts for 80% of the total multiple; Secondary drawing: drawing in 100-110℃ overheat steam box, complete the remaining 20% of the drawing amount; Tension heat setting: four-stage temperature gradient heating, temperature 145℃→155℃→165℃→170℃; Step five: crimping and cutting, after setting, the fiber is preheated by 100℃ steam, the crimping modulus is 8-12 teeth / cm, and after relaxation heat setting, it is cut to 38-51mm; Step six: finished product processing, the fiber is distributed by a cotton feeder, inspected and packed; The black polyester staple fiber has a boiling water shrinkage of ≤1.5% and a color fastness of ≥4 levels.

[0007] Preferably, in the raw material compounding of step one: The intrinsic viscosity of the PET clean bottle piece is 0.70-0.85dL / g, and the ash content is ≤0.05wt%; The bubble material is recycled PET bubble material with a particle size of 2.0-5.0mm and a length distribution deviation of ≤±10%; The carbon black content in the black color master batch is 40-50wt%, the particle size D50 is 1.5-2.5μm, and the carrier is linear PET with a melt index of 250-300g / 10min: 230℃ / 2.16kg; When compounding, first mix the PET clean bottle piece and the bubble material in a double-cone mixer at 15-25r / min for 10min, and then add the black color master batch and continue mixing for 5min.

[0008] Preferably, in the drying process of step two: A closed continuous drying tower is used, the drying temperature is 160-180℃, the drying time is 4.0-5.0h, and the airflow speed is 0.8-1.2m / s; the drying system is equipped with a dew point monitor with an accuracy of ±2℃ and an automatic water replenishment device, which automatically starts the molecular sieve regeneration program when the dew point is >-35℃; the moisture content of the raw material after drying is ≤25ppm.

[0009] Preferably, in the spinning forming of step three: The precision of the double-stage melt filter is: the first stage is 20±2μm, and the second stage is 10±1μm, and the switching pressure difference is set to 5.0±0.5MPa; the compound oil agent is composed of the following mass percentage components: glycerol 65±5%, antistatic agent: alkyl phosphate potassium salt 18±2%, emulsifier: sorbitan monooleate 12±2%, and the rest is penetrant: fatty alcohol polyoxyethylene ether; The oil agent concentration is controlled to be 0.35-0.45%, and the recycling period is ≤48h; The winding speed is 3000±200m / min, and the winding tension is 0.15-0.25cN / dtex.

[0010] Preferably, in the step four primary drawing: Oil-water bath containing fatty acid ester smooth agent 0.5±0.1wt%, bath ratio 1:15±0.5; The difference of drawing roller linear speed is controlled to be 1:3.8±0.2, and the drawing temperature is 68±2℃; The fiber immersion length in the bath is ≥1.2m, and the immersion time is ≥1.5s.

[0011] Preferably, in the step four secondary drawing: The superheated steam pressure is 0.11-0.15MPa, and the temperature is 105±5℃; The steam jet angle is 40±5° to the fiber axial direction, and the steam flow rate is 8-12m / s; The drawing residence time is 4.0±0.5s, and the drawing tension is 0.30-0.45cN / dtex.

[0012] Preferably, in the step four tension heat setting: The fourth stage temperature zone adopts indirect heating by heat conduction oil, and the heat conduction oil flow rate is 10±2m 3 / h; The residence time ratio of each temperature zone is 1:1.2:1.5:1.8, corresponding to: Zone 1: 22±2s: 145±2℃ Zone 2: 26±2s: 155±2℃ Zone 3: 33±2s: 165±2℃ Zone 4: 40±2s: 170±2℃ The total heat setting time is 121±5s.

[0013] Preferably, in the step five crimping and cutting: The steam preheating temperature is 102±3℃, and the preheating time is 6-8s; The crimping modulus is 10±2 teeth / cm, and the crimping pressure is 0.45±0.05MPa; The relaxation heat setting temperature is 105±5℃, the air speed is 1.0±0.2m / s, and the setting time is 25±5min; The cutting knife disc rotating speed is 2000±200rpm, and the fiber length is controlled to be 40.0±1.0mm.

[0014] Preferably, the step three spinning assembly regeneration includes: The spinneret is treated in a vacuum calcination furnace at 420±20℃ for 120±10min, and the vacuum degree is ≤1×10 -2 Pa; The ultrasonic cleaning frequency is 40±2kHz, the pure water conductivity is ≤5μS / cm, and the cleaning time is 30±2min; Compressed air pressure 0.6±0.1MPa, after purging, the residual water on the surface of the assembly is ≤0.1mg / cm 2 .

[0015] Preferably, the recycling of the composite oil agent comprises the following steps: Oil agent preparation: mix the concentrated spinning oil agent with distilled water at a mass ratio of 1:200-300, stir at 500-800r / min at 50-60℃ for 20-30min to prepare an emulsion with a concentration of 0.3-0.5%; Concentration control: monitor the emulsion concentration in real time through an online conductivity meter, with a fluctuation range of ≤±0.05%; Recycling oiling: deliver the emulsion to the oiling device of the spinning and drafting section, and collect the residual liquid after the fiber absorbs the oil agent for backflow; Loss replenishment: add distilled water to the backflow liquid to maintain the total amount of emulsion constant, and the replenishment amount is 1.2-1.5 times the amount of fiber carried out.

[0016] The present application has the following beneficial effects: 1. In the present application, when controlling the shrinkage rate of regenerated polyester staple fiber, a gradient temperature control program is established, and different heat setting paths are set for different regenerated raw material components to ensure the accuracy of stress elimination in the fiber, avoid abnormal shrinkage problems caused by local thermal stress concentration, ensure the stability of the ultra-low shrinkage performance of the fiber, and improve the size reliability of the product.

[0017] 2. In the present application, when uneven coloring or crystallization defects are detected, the drawing parameter compensation mechanism can be automatically activated to dynamically adjust the steam drawing angle and the heat setting gradient, so that the fiber molecular chain rearrangement process is always in a controllable state, and the synchronization of color uniformity and ultra-low shrinkage characteristics is ensured.

[0018] 3. In the present application, when performing multi-stage performance optimization of regenerated fiber, the whole process chain from spinning to post-processing is controlled in sections, the shrinkage behavior and interface bonding state of different sections of the fiber are analyzed in real time, the oil agent concentration and drawing strength are dynamically adapted based on the performance deviation value of each functional section, the continuous structure correction is realized for the fiber axial direction, the chain risk of shrinkage rate fluctuation and color fastness decline in traditional process is eliminated, and the finished product qualification rate of high-end textile applications is improved. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0020] Example 1: Preparation method of regenerated ultra-low shrinkage black polyester staple fiber, comprising the following steps: Step one: raw material blending, select PET clean bottle chips 70%, bubble material 20%, and add black color masterbatch 3% by mass percentage; Step two: drying treatment, place the mixed raw materials in an electric heating continuous drying system, control the dew point ≤-40℃, and dry to a moisture content ≤30ppm; Step three: spinning and forming, melt the dried raw material through a screw extruder, the melt temperature is 260℃, pass through a double-stage melt filter, and then enter the spinning box. The melt is transported to the spinneret by a metering pump to extrude the primary fiber, which is cooled by 20℃ circular air, oiled, and wound to form a barrel of raw yarn; Step four: post-treatment section, the barrel of raw yarn is bundled and then subjected to: Primary drawing: drawing in an oil-water bath at 65℃, the drawing ratio accounts for 80% of the total ratio; Secondary drawing: drawing in a superheated steam box at 100℃, completing the remaining 20% of the drawing amount; Tension heat setting: four-stage temperature gradient heating, temperature 145℃→155℃→165℃→170℃; Step five: crimping and cutting, the fiber after setting is preheated by 100℃ steam, the crimping modulus is 8 teeth / cm, and after relaxation heat setting, it is cut to 38mm; Step six: finished product treatment, the fiber is distributed by a cotton conveying fan, inspected, and packed; The boiling water shrinkage of the black polyester staple fiber is ≤1.5%, and the color fastness is ≥4 levels.

[0021] In step one raw material blending: The PET clean bottle chips have a specific viscosity of 0.70dL / g and an ash content ≤0.05wt%; The bubble material is regenerated PET bubble material with a particle size of 2.0mm and a length distribution deviation ≤±10%; The black color masterbatch contains 40wt% carbon black with a particle size D50=1.5μm, and the carrier is linear PET with a melt index of 250g / 10min:230℃ / 2.16kg; When blending, first mix the PET clean bottle chips and the bubble material in a double-cone mixer at 15r / min for 10min, and then add the black color masterbatch and continue mixing for 5min.

[0022] In step two drying treatment: A closed continuous drying tower is used, the drying temperature is 160℃, the drying time is 4.0h, and the air flow speed is 0.8m / s; The drying system is equipped with a dew point monitor with an accuracy of ±2℃ and an automatic water replenishment device, which automatically starts the molecular sieve regeneration program when the dew point is >-35℃; the moisture content of the dried raw material is ≤25ppm.

[0023] Step three in the spinning forming: The double-stage melt filter precision: 20±2μm for the first stage and 10±1μm for the second stage, and the switching pressure difference is set to 5.0±0.5MPa; the compound oil agent is composed of the following mass percentage components: glycerol 65±5%, antistatic agent: alkyl phosphate potassium salt 18±2%, emulsifier: sorbitan monooleate 12±2%, and the rest is penetrant: fatty alcohol polyoxyethylene ether; The oil agent concentration is controlled to be 0.35%, and the recycling period is ≤48h; The winding speed is 3000±200m / min, and the winding tension is 0.15cN / dtex.

[0024] Step four in the primary drawing: The oil-water bath contains fatty acid ester smoothness agent 0.5±0.1wt%, and the bath ratio is 1:15±0.5; The drawing roller linear speed difference is controlled to be 1:3.8±0.2, and the drawing temperature is 68±2℃; The fiber immersion length in the bath is ≥1.2m, and the immersion time is ≥1.5s.

[0025] Step four in the secondary drawing: The superheated steam pressure is 0.11MPa, and the temperature is 105±5℃; The steam jet angle is 40±5° to the fiber axial direction, and the steam flow rate is 8m / s; The drawing residence time is 4.0±0.5s, and the drawing tension is 0.30cN / dtex.

[0026] Step four in the tension heat setting: The fourth temperature zone adopts indirect heating by using heat conduction oil, and the heat conduction oil flow rate is 10±2m 3 / h; The residence time proportion of each temperature zone is 1:1.2:1.5:1.8, corresponding to: Zone one: 22±2s: 145±2℃ Zone two: 26±2s: 155±2℃ Zone three: 33±2s: 165±2℃ Zone four: 40±2s: 170±2℃ The total heat setting time is 121±5s.

[0027] Step five in the crimping and cutting: The steam preheating temperature is 102±3℃, and the preheating time is 6s; The crimping modulus is 10±2 teeth / cm, and the crimping pressure is 0.45±0.05MPa; Relaxation heat setting temperature 105±5℃, air speed 1.0±0.2m / s, setting time 25±5min; Cutting disc rotation speed 2000±200rpm, fiber length control 40.0±1.0mm.

[0028] Step three: spinning assembly regeneration includes: Spinneret treatment in vacuum calcination furnace 420±20℃ for 120±10min, vacuum degree ≤1×10 -2 Pa; Ultrasonic cleaning frequency 40±2kHz, pure water conductivity ≤5μS / cm, cleaning time 30±2min; Compressed air pressure 0.6±0.1MPa, residual water on assembly surface after blowing ≤0.1mg / cm 2 .

[0029] Recycling of composite oil agent includes the following steps: Oil agent preparation: mix concentrated spinning oil agent with distilled water at a mass ratio of 1:200, stir at 500r / min for 20min at 50℃ to prepare an emulsion with a concentration of 0.3%; Concentration control: monitor the emulsion concentration in real time through an online conductivity meter, with a fluctuation range of ≤±0.05%; Circulating oiling: deliver the emulsion to the oiling device in the spinning and drafting sections, and collect the residual liquid after the fiber absorbs the oil agent for backflow; Loss supplement: supplement distilled water to the backflow liquid to maintain the total amount of emulsion constant, with a supplement amount of 1.2 times the amount of fiber carried out.

[0030] Example 2: Preparation method of regenerated ultra-low shrinkage black polyester staple fiber, including the following steps: Step one: raw material blending, select PET clean bottle flakes 75%, bubble material 25% by mass percentage, and add black color masterbatch 4% after mixing; Step two: drying treatment, place the mixed raw materials in an electric heating continuous drying system, control the dew point ≤-40℃, and dry to a moisture content ≤30ppm; Step three: spinning formation, melt the dried raw material through a screw extruder, melt temperature 265℃, pass through a double-stage melt filter, and then enter the spinning box. The melt is delivered to the spinneret by a metering pump to extrude the primary fiber, which is cooled by 25℃ circular air, oiled, and wound to form a barrel of original yarn; Step four: post-treatment section, the barrel of original yarn is bundled and then: Primary drawing: draw in an oil-water bath at 68℃, with a drawing ratio accounting for 80% of the total ratio; Secondary drawing: draw in a superheated steam box at 105℃, completing the remaining 20% of the drawing amount; Tension heat setting: four-stage temperature gradient heating, temperature 145℃→155℃→165℃→170℃; Step five: crimping cutting, after the fiber is preheated by 100℃ steam, the crimping modulus is 8-12 teeth / cm, and the fiber is cut to 45mm after relaxation heat setting; Step six: finished product processing, the fiber is distributed by cotton blower, inspected and packed; The boiling water shrinkage of black polyester staple fiber is ≤1.5%, and the color fastness is ≥4 levels.

[0031] In the raw material compounding of step one: The intrinsic viscosity of PET clean bottle chips is 0.80dL / g, and the ash content is ≤0.05wt%; The bubble material is recycled PET bubble material with a particle size of 4.0mm and a length distribution deviation of ≤±10%; The carbon black content in the black color master batch is 45wt%, the particle size D50 is 2.0μm, and the carrier is linear PET with a melt index of 280g / 10min:230℃ / 2.16kg; During compounding, first mix the PET clean bottle chips and the bubble material in a double-cone mixer at 20r / min for 10min, then add the black color master batch and continue mixing for 5min.

[0032] In the drying process of step two: A closed continuous drying tower is used, the drying temperature is 170℃, the drying time is 4.5h, and the air flow speed is 1.0m / s; The drying system is equipped with a dew point monitor with an accuracy of ±2℃ and an automatic water replenishment device, which automatically starts the molecular sieve regeneration program when the dew point is >-35℃; the moisture content of the raw material after drying is ≤25ppm.

[0033] In the spinning forming of step three: The precision of the two-stage melt filter is: the first stage is 20±2μm, the second stage is 10±1μm, and the switching pressure difference is set to 5.0±0.5MPa; the composite oil agent is composed of the following mass percentage components: glycerol 65±5%, antistatic agent: alkyl phosphate potassium salt 18±2%, emulsifier: sorbitan monooleate 12±2%, and the rest is penetrant: fatty alcohol polyoxyethylene ether; The oil agent concentration is controlled to be 0.40%, and the recycling period is ≤48h; The winding speed is 3000±200m / min, and the winding tension is 0.20cN / dtex.

[0034] In the first-stage drafting of step four: The oil-water bath contains 0.5±0.1wt% of fatty acid ester smoothing agent, and the bath ratio is 1:15±0.5; The drafting roller linear speed difference is controlled to be 1:3.8±0.2, and the drafting temperature is 68±2℃; The fiber is immersed in the bath for a length of ≥1.2 m and a time of ≥1.5 s.

[0035] In the fourth step, secondary drawing includes: The superheated steam has a pressure of 0.13 MPa and a temperature of 105±5℃; The steam injection angle is 40±5° with respect to the fiber axis, and the steam flow rate is 10 m / s; The drawing residence time is 4.0±0.5 s, and the drawing tension is 0.32 cN / dtex.

[0036] In the fourth step, tension heat setting includes: The fourth temperature zone is indirectly heated by heat conduction oil, and the heat conduction oil flow rate is 10±2 m 3 / h; The residence time ratio of each temperature zone is 1:1.2:1.5:1.8, corresponding to: Zone 1: 22±2 s: 145±2℃ Zone 2: 26±2 s: 155±2℃ Zone 3: 33±2 s: 165±2℃ Zone 4: 40±2 s: 170±2℃ The total heat setting time is 121±5 s.

[0037] In the fifth step, crimping and cutting include: The steam preheating temperature is 102±3℃, and the preheating time is 7 s; The crimping modulus is 10±2 teeth / cm, and the crimping pressure is 0.45±0.05 MPa; The relaxation heat setting temperature is 105±5℃, the air speed is 1.0±0.2 m / s, and the setting time is 25±5 min; The cutting knife disc speed is 2000±200 rpm, and the fiber length is controlled to be 40.0±1.0 mm.

[0038] In the third step, the spinning assembly regeneration includes: The spinneret is treated in a vacuum calcination furnace at 420±20℃ for 120±10 min, and the vacuum degree is ≤1×10 -2 Pa; The ultrasonic cleaning frequency is 40±2 kHz, the pure water conductivity is ≤5 μS / cm, and the cleaning time is 30±2 min; The compressed air pressure is 0.6±0.1 MPa, and the residual water on the surface of the assembly after blowing is ≤0.1 mg / cm 2 .

[0039] The recycling of the composite oil agent includes the following steps: Oil agent preparation: mix the concentrated spinning oil agent with distilled water at a mass ratio of 1:250, stir at 55℃ for 25 min at 600 r / min, and prepare an emulsion with a concentration of 0.4%; Concentration control: The emulsion concentration was monitored in real time by an online conductivity meter, with a fluctuation range of ≤±0.05%; Circulating oiling: The emulsion was delivered to the oiling device of the spinning and drafting section, and the residual liquid after the fiber absorbed the oil agent was returned through a collection tank; Loss replenishment: Distilled water was added to the return liquid to maintain the total amount of the emulsion constant, and the replenishment amount was 1.4 times the amount of fiber carried out.

[0040] Example 3: Preparation method of regenerated ultra-low shrinkage black polyester staple fiber, comprising the following steps: Step one: raw material blending, select PET clean bottle chips 80%, foam material 30% by mass percentage, add black color masterbatch 5% after mixing; Step two: drying treatment, place the mixed raw materials in an electric heating continuous drying system, control the dew point to be ≤-40℃, and dry to a moisture content of ≤30ppm; Step three: spinning and forming, melt the dried raw material through a screw extruder, with a melt temperature of 270℃, pass through a double-stage melt filter, and then enter the spinning box. The melt is delivered to the spinneret by a metering pump to extrude the primary fiber, which is cooled by 30℃ circular air, oiled, and wound to form a barrel of raw yarn; Step four: post-treatment section, the barrel of raw yarn is bundled and then subjected to: Primary drawing: drawing in a 70℃ oil-water bath, with a drawing ratio accounting for 80% of the total ratio; Secondary drawing: drawing in a 110℃ superheated steam box, completing the remaining 20% of the drawing amount; Tension heat setting: four-stage temperature gradient heating, with temperatures of 145℃→155℃→165℃→170℃; Step five: crimping and cutting, the fiber after setting is preheated by 100℃ steam, with a crimping modulus of 8-12 teeth / cm, and is cut to 51mm after relaxation heat setting; Step six: finished product treatment, the fiber is distributed by a cotton conveying fan and is inspected and packaged; The boiling water shrinkage of the black polyester staple fiber is ≤1.5%, and the color fastness is ≥4 levels.

[0041] In step one of raw material blending: The PET clean bottle chips have a specific viscosity of 0.85dL / g and an ash content of ≤0.05wt%; The foam material is regenerated PET foam material with a particle size of 5.0mm and a length distribution deviation of ≤±10%; The black color masterbatch contains 50wt% of carbon black with a particle size of D50=2.5μm, and the carrier is linear PET with a melt index of 300g / 10min: 230℃ / 2.16kg; The PET clean bottle pieces and the foaming material are mixed in a double-cone mixer at 25 r / min for 10 min, and then the black color master batch is added and mixed for 5 min.

[0042] In the drying process of step two: A closed continuous drying tower is used, the drying temperature is 180 ℃, the drying time is 5.0 h, and the airflow speed is 1.2 m / s; The drying system is equipped with a dew point monitor with an accuracy of ±2 ℃ and an automatic water supply device, which automatically starts the molecular sieve regeneration program when the dew point is greater than -35 ℃; the moisture content of the raw material after drying is ≤25 ppm.

[0043] In the spinning process of step three: The precision of the two-stage melt filter is 20±2 μm for the first stage and 10±1 μm for the second stage, and the switching pressure difference is set to 5.0±0.5 MPa; the composite oil agent is composed of the following mass percentage components: glycerol 65±5%, antistatic agent: alkyl phosphate potassium salt 18±2%, emulsifier: sorbitan monooleate 12±2%, and the rest is penetrant: fatty alcohol polyoxyethylene ether; The oil agent concentration is controlled to be 0.45%, and the recycling period is ≤48 h; The winding speed is 3000±200 m / min, and the winding tension is 0.25 cN / dtex.

[0044] In the first-stage drawing of step four: The oil-water bath contains fatty acid ester smoothness agent 0.5±0.1 wt%, and the bath ratio is 1:15±0.5; The drawing roller linear speed difference is controlled to be 1:3.8±0.2, and the drawing temperature is 68±2 ℃; The fiber immersion length in the bath is ≥1.2 m, and the immersion time is ≥1.5 s.

[0045] In the second-stage drawing of step four: The superheated steam pressure is 0.15 MPa, and the temperature is 105±5 ℃; The steam jet angle is 40±5° with respect to the fiber axis, and the steam flow rate is 12 m / s; The drawing residence time is 4.0±0.5 s, and the drawing tension is 0.45 cN / dtex.

[0046] In the tension heat setting of step four: The fourth-stage temperature zone uses indirect heating with heat-conducting oil, and the heat-conducting oil flow rate is 10±2 m 3 / h; The residence time proportion of each temperature zone is 1:1.2:1.5:1.8, corresponding to: Zone one: 22±2 s: 145±2 ℃ Zone two: 26±2 s: 155±2 ℃ Three zones: 33±2s: 165±2℃ Four zones: 40±2s: 170±2℃ Total heat setting time 121±5s.

[0047] In the fifth step of crimping and cutting: Steam preheating temperature 102±3℃, preheating time 8s; Crimping modulus 10±2 teeth / cm, crimping pressure 0.45±0.05 MPa; Relaxation heat setting temperature 105±5℃, air speed 1.0±0.2 m / s, setting time 25±5 min; Cutting knife disc rotation speed 2000±200 rpm, fiber length controlled to 40.0±1.0 mm.

[0048] The third step of spinning assembly regeneration includes: Spinneret treated in a vacuum calcination furnace at 420±20℃ for 120±10 min, vacuum degree ≤1×10 -2 Pa; Ultrasonic cleaning frequency 40±2 kHz, pure water conductivity ≤5 μS / cm, cleaning time 30±2 min; Compressed air pressure 0.6±0.1 MPa, residual water on the surface of the assembly after blowing ≤0.1 mg / cm 2 .

[0049] The recycling of the composite oil agent includes the following steps: Oil agent preparation: mix concentrated spinning oil agent with distilled water at a mass ratio of 1:300, stir at 800 r / min at 60℃ for 30 min, and prepare an emulsion with a concentration of 0.5%; Concentration control: monitor the emulsion concentration in real time through an online conductivity meter, with a fluctuation range of ≤±0.05%; Recycling of oiling: deliver the emulsion to the oiling device of the spinning and drafting section, and collect the residual liquid after the fiber absorbs the oil agent for backflow; Loss supplement: supplement distilled water to the backflow liquid to maintain the total amount of emulsion constant, and the supplement amount is 1.5 times the amount of fiber carried out.

[0050] Comparative Example 1, the difference between this comparative example and Example 1 is that this comparative example does not use four-stage gradient heat setting process in the fiber post-processing stage.

[0051] Comparative Example 2, the difference between this comparative example and Example 1 is that this comparative example does not add in-situ coloring black masterbatch in the spinning process.

[0052] Comparative Example 3, the difference between this comparative example and Example 1 is that this comparative example cancels the steam injection angle dynamic control mechanism in the drafting section.

[0053] Comparative Example 4, which differs from Example 1 in that the composite oil agent closed loop circulation system is not implemented.

[0054] The regenerated polyester staple fibers prepared in Examples 1-3 and Comparative Examples 1-4 are subjected to performance testing, and the test items and methods are as follows: Boiling water shrinkage test: take a 100 mm long fiber sample, place it in boiling water for 30 min, measure the length change after cooling, and calculate the shrinkage; Color fastness test: use the gray scale color comparison method to evaluate the fiber color difference grade under D65 standard light source; Breaking strength test: use an electronic strength tester, clamp distance 20 mm, tensile speed 20 mm / min, record the fiber breaking load; size stability verification: place the fiber in a 65% RH humidity environment for 240 h, and measure the length change rate.

[0055] The test data of the black polyester staple fibers prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the following table: By comparing and analyzing the data in the table, it can be seen that the regenerated ultra-low shrinkage black polyester staple fiber prepared by the process of Examples 1-3 has significantly better performance than the regenerated ultra-low shrinkage black polyester staple fiber prepared by the process of Comparative Examples 1-4, which indicates that the temperature progressive mechanism of four-stage gradient heat setting forms an ordered β crystal structure inside the fiber, promotes molecular chain segmental relaxation, eliminates the interface stress difference between amorphous and crystalline regions, and suppresses the thermal shrinkage potential; at the same time, the in-situ coloring process allows the nanoscale dispersion of carbon black masterbatch in the screw melting section, allowing the coloring network to uniformly penetrate into the fiber skin and core, avoiding the secondary molecular chain disorientation problem caused by traditional post-dyeing process, thereby improving color fastness; the composite oil agent closed loop system dynamically maintains the oil agent concentration in the optimal range through real-time conductivity monitoring, builds a continuous nanoscale lubricating film on the fiber surface, reduces friction damage and local stress concentration during drawing, and cooperatively strengthens size stability and breaking strength; the steam drawing section precisely matches the fiber axial motion trajectory, uses the Coanda effect to form a ring-shaped heat flow wrapping layer, allows steam heat energy to uniformly penetrate into the fiber depth, simultaneously completes the drawing and preheating processes, and eliminates the shrinkage difference between the skin and core.

[0056] By comparing and analyzing the relevant data in the table, it can be seen that the regenerated ultra-low shrinkage black polyester staple fiber prepared by the process of the present application not only has excellent low shrinkage, high color fastness and strong size stability. This indicates that the regenerated ultra-low shrinkage black polyester staple fiber preparation method provided by the present application has a broader market prospect in the high-end textile field and is more suitable for promotion.

[0057] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing regenerated ultra-low shrinkage black polyester staple fiber, characterized in that: The method comprises the following steps: Step one: raw material mixing, select PET clean bottle chips 70-80%, bubble material 20-30%, add black color master batch 3-5% by mass percentage; Step two: drying treatment, place the mixed raw materials in an electric heating continuous drying system, control the dew point ≤-40℃, dry to a moisture content ≤30ppm; Step three: spinning forming, melt the dried raw materials by screw extruder, melt temperature 260-270℃, pass through double-stage melt filter, then enter the spinning box; the melt is delivered to the spinneret by metering pump to extrude the primary fiber, cooled by 20-30℃ circular air, oiled and wound to form the barrel-packed raw yarn; Step four: post-treatment section, the barrel-packed raw yarn is bundled and then subjected to the following processes in sequence: Primary drawing: drawn in oil-water bath at 65-70℃, the drawing multiple accounts for 80% of the total multiple; Secondary drawing: drawn in superheated steam box at 100-110℃, complete the remaining 20% of the drawing amount; Tight heat setting: four-stage temperature gradient heating, temperature 145℃→155℃→165℃→170℃; Step five: crimping and cutting, the fiber after setting is preheated by 100℃ steam, crimping modulus 8-12 teeth / cm, after relaxation heat setting, cut to 38-51mm; Step six: finished product treatment, the fiber is distributed by cotton conveying fan, inspected and packed; The black polyester staple fiber has a boiling water shrinkage rate ≤1.5% and a color fastness ≥4 levels.

2. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 1, characterized in that: In the step one raw material mixing: The PET clean bottle chips have a specific viscosity of 0.70-0.85dL / g and ash content ≤0.05wt%; The bubble material is recycled PET bubble material with a particle size of 2.0-5.0mm and a length distribution deviation ≤±10%; The black color master batch contains 40-50wt% carbon black with a particle size D50=1.5-2.5μm, and the carrier is linear PET with a melt index of 250-300g / 10min: 230℃ / 2.16kg; During mixing, first mix the PET clean bottle chips and the bubble material in a double-cone mixer at 15-25r / min for 10min, then add the black color master batch and continue mixing for 5min.

3. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 1, characterized in that: In the step two drying treatment: A closed continuous drying tower is used, the drying temperature is 160-180℃, the drying time is 4.0-5.0h, and the air flow speed is 0.8-1.2m / s; The drying system is equipped with a dew point monitor with an accuracy of ±2℃ and an automatic water replenishing device, which automatically starts the molecular sieve regeneration program when the dew point is >-35℃; the moisture content of the dried raw material is ≤25ppm.

4. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 1, characterized in that: In the step three spinning forming: The double-stage melt filter has an accuracy of 20±2μm for the first stage and 10±1μm for the second stage, and the switching pressure difference is set to 5.0±0.5MPa; The composite oil agent is composed of the following mass percentage components: glycerol 65±5%, antistatic agent: alkyl phosphate potassium salt 18±2%, emulsifier: sorbitan monooleate 12±2%, and the rest is penetrant: fatty alcohol polyoxyethylene ether; The oil agent concentration is controlled to be 0.35-0.45%, and the recycling period is ≤48h; The winding speed is 3000±200m / min, and the winding tension is 0.15-0.25cN / dtex.

5. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 1, characterized in that: In the step four primary drawing: Oil water bath containing fatty acid ester smoothness agent 0.5±0.1wt%, bath ratio 1:15±0.5; Drawing roller linear speed difference control 1:3.8±0.2, drawing temperature 68±2℃; Fiber immersion length in bath ≥1.2m, immersion time ≥1.5s.

6. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 1, characterized in that: In the step four secondary drawing: Superheated steam pressure 0.11-0.15MPa, temperature 105±5℃; Steam jet angle 40±5° to fiber axial direction, steam flow rate 8-12m / s; Drawing residence time 4.0±0.5s, drawing tension 0.30-0.45cN / dtex.

7. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 1, characterized in that: In the step four tight heat setting: The fourth temperature zone is indirectly heated by heat conducting oil, and the flow of the heat conducting oil is 10±2 m 3 / h; Residence time ratio of each temperature zone 1:1.2:1.5:1.8, corresponding to: Zone 1: 22±2s: 145±2℃ Zone 2: 26±2s: 155±2℃ Zone 3: 33±2s: 165±2℃ Zone 4: 40±2s: 170±2℃ Total heat setting time 121±5s.

8. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 1, characterized in that: In the step five crimping and cutting: Steam preheating temperature 102±3℃, preheating time 6-8s; Crimping modulus 10±2 teeth / cm, crimping pressure 0.45±0.05MPa; Relaxation heat setting temperature 105±5℃, air speed 1.0±0.2m / s, setting time 25±5min; Cutting knife disc rotation speed 2000±200rpm, fiber length control 40.0±1.0mm.

9. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 1, characterized in that: In the step three spinning assembly regeneration: The spinneret is treated in a vacuum calcining furnace at 420 ± 20 °C for 120 ± 10 min, at a vacuum of < 1 x 10 -2 Pa; Ultrasonic cleaning frequency 40±2kHz, pure water conductivity ≤5μS / cm, cleaning time 30±2min; Compressed air pressure 0.6±0.1MPa, residual water on the surface of the assembly after blowing ≤0.1mg / cm 2 .

10. The method for preparing recycled ultra-low shrinkage black polyester staple fiber according to claim 4, characterized in that: The recycling of the composite oil agent includes the following steps: Oil agent preparation: mix concentrated spinning oil agent and distilled water at a mass ratio of 1:200-300, stir at 500-800r / min at 50-60℃ for 20-30min to prepare an emulsion with a concentration of 0.3-0.5%; Concentration control: monitor the emulsion concentration in real time through an online conductivity meter, with a fluctuation range of ≤±0.05%; Recycling oiling: deliver the emulsion to the oiling device of the spinning and drawing section, and collect the residual liquid after the fiber absorbs the oil agent for backflow; Loss supplement: supplement distilled water to the backflow liquid to maintain the total amount of emulsion constant, with a supplement amount of 1.2-1.5 times the amount of fiber carried out.

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