Fine denier poys with uniform thermal stress, and preparation method and application thereof

Abstract

The application belongs to the technical field of spinning, and relates to fine denier POY with uniform thermal stress, a preparation method and application thereof. The preparation method comprises ring blowing air cooling, and the steps of ring blowing air cooling are as follows: the melt stream passes through a draft tube; 1 spool of fine denier POY is spun at each spool position, the thermal stress values of the fine denier POY spun at all spool positions are detected, and then an average thermal stress value mu1 is calculated; 1 spool of fine denier POY is continuously spun at each spool position, the thermal stress values of the fine denier POY continuously spun at all spool positions are detected; the thermal stress values of the fine denier POY continuously spun at each spool position are compared with mu1, the length of the draft tube is adjusted according to the comparison result, and the thermal stress of the fine denier POY continuously spun at each spool position is 0.97-1.03 times of mu1. The prepared fine denier POY has a thermal stress CV value of less than 2%, the uniformity of thermal stress is achieved, and the prepared DTY has excellent tension uniformity, quality grade and dyeing uniformity.

Description

Technical Field

[0001] This invention belongs to the field of spinning technology, and relates to a fine denier POY with uniform thermal stress, its preparation method and application. Background Technology

[0002] Fine denier POY (pre-oriented yarn) generally refers to fibers with a single filament fineness of less than 1.0 dtex. Due to its extremely fine fibers, it possesses advantages such as a soft hand feel, gentle luster, and a texture close to silk, making it widely used in high-end clothing fabrics such as imitation silk and wool. It can also be processed into DTY (dilatation-textured yarn). Therefore, researching the preparation technology of high-quality fine denier POY is of great significance.

[0003] In the production of fine denier POY, due to the rapid fiber cooling rate and the large number of spinneret orifices, traditional side-blowing cooling easily leads to uneven cooling and the formation of a "skin-core structure," resulting in poor fiber dyeing performance. Therefore, the industry commonly uses ring-blowing cooling to improve uniformity. However, existing ring-blowing technology still faces a significant challenge: the uniformity of thermal stress among POY spindles within the spinning unit is poor, resulting in a high CV value (coefficient of variation), especially in ultra-fine denier varieties, where the thermal stress CV value at the spinning unit is generally higher than 5.0%.

[0004] The uniformity of thermal stress in POY directly determines the tension uniformity of subsequent texturing processes, ultimately affecting the dyeing uniformity and quality grade (such as AA and AAA rates) of DTY products. Currently, while the industry can control thermal stress by adjusting temperature, these methods primarily improve the overall difference between spinning positions, with minimal effect on improving the uniformity of thermal stress between individual spindles within the spinning position. Therefore, reducing the difference in thermal stress values ​​between spindles, and thus stabilizing the overall thermal stress CV value of the spinning position at a low level (e.g., below 2.0%), becomes crucial for improving the quality of POY and its downstream products.

[0005] In the prior art, such as the utility model patent with authorization announcement number CN212741600U, an adjustable windless zone length ring blower box is provided. Although this technical solution facilitates the adjustment of the overall windless zone length during different batches of production, its adjustment is still a unified control of the entire spinning position, and cannot achieve independent and precise control of individual spindles. Therefore, it fails to fundamentally solve the core problem of uneven thermal stress between spindles.

[0006] In summary, in order to effectively improve the uniformity of thermal stress between spindles of fine denier POY, thereby significantly improving fiber dyeing performance and final product grade, it is urgent to improve and optimize existing fine denier POY preparation methods, especially the ring-blowing cooling system. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and to provide a fine denier POY with uniform thermal stress, its preparation method and application.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing fine denier POY with uniform thermal stress includes a ring-blowing cooling process, the steps of which are as follows:

[0010] (a) The molten flow enters m spinning positions, where m is a positive integer. Each spinning position is equipped with a ring blower box, and each ring blower box is equipped with n spindle positions, where n is an integer not less than 10. Each spindle position is equipped with a cylindrical filter element. The filter element has radial ventilation holes on its cylindrical wall. The ring blower enters the filter element from the outside through the ventilation holes to cool the molten flow inside the filter element. Each filter element is equipped with a non-airflow tube. The non-airflow tube is a tube with open ends. The tube wall of the non-airflow tube has no through holes. The ring blower cannot enter the non-airflow tube from the sides. The length of the non-airflow tube is less than the length of the filter element. The molten flow passes through the non-airflow tube.

[0011] (b) Each spindle first spins out 1 spindle of fine denier POY (for example, when preparing fine denier POY of the same batch number, there are 10 spinning positions, and each ring blower box has 10 spindles. All spinning positions first spin out a total of 100 spindles of fine denier POY). After detecting the thermal stress value of the fine denier POY spun out by all spindles first, the average thermal stress value μ1 is calculated.

[0012] (c) Each spindle continues to spin 1 spindle of fine denier POY, and the thermal stress value of the fine denier POY spun by all spindles is detected;

[0013] (d) Compare the thermal stress value of the fine denier POY spun from each spindle with μ1, make adjustments based on the comparison results, and return to step (c) after adjustment.

[0014] The adjustment refers to replacing the corresponding airless tube with a longer one for spindles where the thermal stress value of the fine denier POY produced is greater than 1.03 times μ1; and replacing the corresponding airless tube with a shorter one for spindles where the thermal stress value of the fine denier POY produced is less than 0.97 times μ1.

[0015] The principle of this invention is as follows:

[0016] The inventors have discovered that the high thermal stress CV value of fine denier POY is mainly related to the precision of the equipment, such as the difficulty in eliminating temperature differences caused by dimensional differences in the annular blower box.

[0017] When the thermal stress of a single ingot of fine denier POY exceeds the upper limit of the set value, the length of the airless duct is increased to reduce the influence of cooling air and delay cooling. When the thermal stress of a single ingot of fine denier POY is lower than the lower limit of the set value, the length of the airless duct is shortened to increase the influence of cooling air and accelerate cooling. This ensures that the difference in thermal stress value between different ingots of fine denier POY in the same batch is very small, achieving a thermal stress CV value of <2% for fine denier POY in the same batch. The thermal stress CV value is calculated as (σ / μ)×100%, where μ is the average thermal stress of fine denier POY in the same batch, and σ is the standard deviation of thermal stress in fine denier POY in the same batch.

[0018] The inventors also discovered that μ(1±0.03) is equivalent to a thermal stress CV value <2%, and this equivalence can be theoretically proven, as follows:

[0019] The specific thermal stress values ​​of a single-spindle fine denier POY are approximately symmetrically distributed on both sides of the average thermal stress value μ.

[0020] For this symmetrical distribution, the specific thermal stress values ​​of single-spindle fine denier POY within the interval [a, b] have a maximum value of (ba) / Where a = 0.97 μ and b = 1.03 μ;

[0021] σ≤(1.03μ-0.97μ) / =0.0173μ; thermal stress CV value = (σ / μ)×100%≤(0.0173μ / μ)×100%=1.73%, which satisfies the thermal stress CV value <2%, thus achieving uniform thermal stress in POY.

[0022] As a preferred technical solution:

[0023] In the preparation method of fine denier POY with uniform thermal stress as described above, in step (a), the length of the filter element is 190 mm and the length of the air duct is 20 mm.

[0024] In the above-described method for preparing fine denier POY with uniform thermal stress, in step (d), the length of the replaced airless tube is increased or decreased by 0.8-1.2 mm to ensure high precision in the increase or decrease of the length of the airless tube, which can prevent large fluctuations in the length of the airless tube and make the thermal stress value of the fine denier POY spun more accurately maintain at 0.97-1.03 times the average thermal stress value μ1.

[0025] In the above-described method for preparing fine denier POY with uniform thermal stress, in step (a), the top of the outer wall of the airless duct is fixed with a radial protrusion by welding, one-time molding, or other methods. This design ensures that the airless duct is detachably connected to the inside of the filter element through the protrusion, which not only prevents the airless duct from falling completely into the inside of the filter element, but also enables the quick installation and replacement of the airless duct from the top of the filter element.

[0026] As described above, in the preparation method of fine denier POY with uniform thermal stress, the protrusions are annular and have equal axial thickness. This design ensures that the airless tube hangs more stably on the top of the filter element, reducing the shaking and tilting of the airless tube caused by the ring blowing.

[0027] In the preparation method of fine denier POY with uniform thermal stress as described above, in step (a), the outer diameter of the airless duct is equal to the inner diameter of the filter element, thereby reducing the gap between the airless duct and the filter element and reducing the cooling of the inside of the airless duct by the annular air blowing.

[0028] The present invention also provides a fine denier POY with uniform thermal stress, which is prepared by the preparation method of fine denier POY with uniform thermal stress as described in any of the preceding claims, wherein the thermal stress CV value of all fine denier POY spun by all spindles is <2%.

[0029] As a preferred technical solution:

[0030] The above describes a type of thermally uniform fine denier POY, wherein the thermally uniform fine denier POY is polyester, nylon 6, or nylon 66.

[0031] The present invention also provides a method for preparing DTY using fine denier POY through a texturing process, wherein the fine denier POY is a type of thermally stress-uniform fine denier POY as described in any of the preceding claims;

[0032] The parameters for the texturing process are: stretch ratio 1.5-1.9, texturing speed 600-1000m / min, deformation temperature 170-200℃, setting temperature 120-150℃, false twist tension 20-25cN, winding tension 7-8cN, friction disc type PU disc, and D / Y ratio 1.5-1.7.

[0033] The present invention also provides a DTY, which is prepared by a method described above using fine denier POY through a texturing process;

[0034] The tension CV value of DTY is <2%, which is an indicator of tension uniformity. The tension CV value of DTY is measured online by the texturing machine. The quality grade of DTY is AA rate >95%, AAA rate >80%, and dyeing M rate >80%. Thermal stress is an indicator of the internal structure of the fiber. Equal thermal stress indicates that the orientation and crystallinity of the molecular chains inside the fiber are the same. Controlling the thermal stress CV value to <2% means controlling the fiber difference between spindles and ensuring high similarity of the internal structure of the fiber. Tension uniformity and dyeing uniformity are highly correlated with the internal structure of the fiber. The higher the similarity of the internal structure of the fiber, the better the tension uniformity and dyeing uniformity, and the higher the quality grade. Therefore, this invention controls the thermal stress CV value of fine denier POY in the same batch to <2%, so that the final DTY has excellent tension uniformity, dyeing uniformity and quality grade.

[0035] Beneficial effects:

[0036] (1) In the preparation of fine denier POY, the present invention achieves precise cooling during the ring blowing cooling by dynamically and finely adjusting the length of the airless tube, so that the prepared fine denier POY meets the thermal stress CV value <2%, and ensures the uniform thermal stress of fine denier POY.

[0037] (2) The method for preparing fine denier POY of the present invention is simple, feasible and low cost. It only requires a series of airless tubes of different lengths with a length difference accuracy of 0.8-1.2 mm. There is no need to make structural changes to existing spinning equipment such as ring blowers. It is applicable to existing spinning equipment.

[0038] (3) By controlling the thermal stress CV value of fine denier POY in the same batch to <2%, the present invention makes the final DTY have excellent tension uniformity, dyeing uniformity and quality grade. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a ductless structure;

[0040] Figure 2 This is a front view diagram without ductwork;

[0041] Figure 3 This is a top view diagram without ductwork;

[0042] Figure 4 This is a three-dimensional structural diagram of the air duct and filter element before assembly;

[0043] Figure 5 This is a front view diagram of the ductless air duct and filter element before assembly;

[0044] Figure 6 This is a structural diagram of the spinning box, airless duct, filter element, and ring blower box before assembly;

[0045] Figure 7 This is a schematic diagram of the filter element and the ring blower box after assembly;

[0046] Figure 8 This is a schematic diagram of the structure of the air ductless, filter element and ring blower box after assembly;

[0047] In the diagram, 1 is a ductless unit, 11 is a protrusion, 2 is a filter element, 21 is a ventilation hole, 3 is a ring blower box, 31 is an assembly hole, and 4 is a spinning box. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0049] The following are the relevant performance testing methods for each embodiment and comparative example:

[0050] (1) Thermal stress value of fine denier POY: After the fine denier POY is fully wound, the thermal stress value of each spindle of fine denier POY is tested using a thermal stress meter under the conditions of temperature of 170℃, pre-tension of 0.05±0.005cN / dtex, stretch ratio of 1.6 and test speed of 100m / min. The manufacturer of the thermal stress meter is Changzhou Bafang Lishi Textile Instrument Co., Ltd., and the model is YG367.

[0051] (2) Thermal stress CV values ​​of fine denier POY from the same batch:

[0052] Thermal stress CV value = (σ / μ) × 100%;

[0053] Where σ= σ is the standard deviation of thermal stress of fine denier POY in the same batch, Xi is the thermal stress value of a single ingot of fine denier POY in the same batch, μ is the average thermal stress of fine denier POY in the same batch, and N is the total number of ingots of fine denier POY in the same batch.

[0054] (3) CV value of DTY tension:

[0055] Tension CV value = (σ / μ) × 100%;

[0056] Where σ= σ is the standard deviation of tension of DTY in the same batch, Xi is the tension value of a single ingot of DTY in the same batch, μ is the average tension of DTY in the same batch, and N is the total number of single ingots of DTY in the same batch.

[0057] (4) DTY quality grade: tested according to standard Q / 320584 NPA003-2018.

[0058] (5) Dyeing M rate of DTY: The percentage of the number of spindles of DTY with dyeing uniformity ≥ 4.5 to the total number of spindles of all DTY. The dyeing uniformity grade is tested according to GB / T 6508-2015.

[0059] Example 1a

[0060] A method for preparing fine denier POY with uniform thermal stress, using the following method: Figures 1-8 The apparatus shown is used in the following steps:

[0061] (1) Prepare raw materials;

[0062] Melt: PET, intrinsic viscosity 0.6 dL / g;

[0063] (2) Melt transport;

[0064] The temperature of the melt is 280℃;

[0065] (3) Melt extrusion forms a melt stream;

[0066] The melt enters 10 spinning stations, each spinning station is equipped with a spinning box 4, each spinning box 4 is equipped with 10 spindles, each spindle is equipped with a spinning assembly, the temperature of the spinning box 4 is 288℃, the spinneret has 96 holes, the diameter of the spinneret is 85mm, and the orifice diameter of the spinneret is 0.15mm.

[0067] (4) Circular air blowing cooling;

[0068] (4.1) The melt stream enters 10 spinning positions. Each spinning position is equipped with a ring blower box 3. Each ring blower box 3 is equipped with 10 spindles. The top of the ring blower box 3 is equipped with an assembly hole 31 corresponding to each spindle. A cylindrical filter element 2 is installed in each assembly hole 31. The peripheral wall of the filter element 2 is equipped with ventilation holes 21. A non-air tube 1 is inserted in each filter element 2. The outer diameter of the non-air tube 1 is equal to the inner diameter of the filter element 2. The top of the outer wall of the non-air tube 1 is fixed with a radial protrusion 11 in a one-time forming method. The protrusion 11 is annular and the axial thickness of the protrusion 11 is equal. The protrusion 11 is hung on the top of the filter element 2. The non-air tube 1 and the filter element 2 are coaxial. The length of the filter element 2 is 190mm and the length of each non-air tube 1 is 20mm.

[0069] (4.2) Each spindle first spins out 1 spindle of fine denier POY, and a total of 100 spindles of fine denier POY are obtained. After detecting the thermal stress value of these 100 spindles of fine denier POY, the average thermal stress value μ1 is calculated.

[0070] (4.3) Each spindle continues to spin 1 spindle of fine denier POY, resulting in a total of 100 spindles of fine denier POY. The thermal stress value of these 100 spindles of fine denier POY is then tested.

[0071] (4.4) Compare the thermal stress value of the fine denier POY spun from each spindle with μ1, make adjustments based on the comparison results, and return to step (4.3) after adjustment.

[0072] The adjustment refers to the following: for spindles where the thermal stress value of the fine denier POY produced is greater than 1.03 times μ1, the corresponding airless tube 1 is replaced with a longer airless tube 1, increasing the length by 1.2 mm; for spindles where the thermal stress value of the fine denier POY produced is less than 0.97 times μ1, the corresponding airless tube 1 is replaced with a shorter airless tube 1, decreasing the length by 1.2 mm.

[0073] The thermal stress CV value of the fine denier POY produced in the same batch (i.e., all fine denier POY spun from the above 100 spindles) was 1.72%.

[0074] Example 1b

[0075] A method for preparing DTY using fine denier POY via a texturing process, wherein the fine denier POY is provided in Example 1a;

[0076] The parameters for the texturing process are: stretch ratio 1.6, texturing speed 750m / min, deformation temperature 180℃, setting temperature 140℃, false twist tension 20cN, winding tension 7cN, friction disc type PU disc, and D / Y ratio 1.65.

[0077] The tension CV value of the prepared DTY was 1.73%; the quality grade of DTY was AA (95.2%), AAA (80.1%), and M (83.0%).

[0078] Comparative Example 1a

[0079] A method for preparing fine denier POY differs from Example 1a only in that no air duct is added.

[0080] The thermal stress CV value of the fine denier POY produced in the same batch was 5.07%.

[0081] Compared with Example 1a, the thermal stress CV value of the same batch of fine denier POY in Comparative Example 1a increased by 3.35%. This is because Comparative Example 1a did not add a ductless airflow, the airflowless zone became shorter, the temperature difference of the melt stream during ring blowing cooling was large, which increased the difference in the internal fiber structure between spindles and made the thermal stress more dispersed.

[0082] Comparative Example 1b

[0083] A method for preparing DTY using fine denier POY via a texturing process, differing from Example 1b only in that the fine denier POY is provided by Comparative Example 1a.

[0084] The obtained DTY had a tension CV value of 4.96%, a quality grade of AA of 95.1%, a grade of AAA of 28.4%, and a staining grade of M of 29.5%.

[0085] Compared with Example 1b, the quality grade AA rate of DTY in Comparative Example 1b did not change significantly, the tension CV value increased by 3.23%, the AAA rate of DTY decreased by 51.7%, and the staining M rate decreased by 53.5%. This is because the thermal stress CV value of fine denier POY is higher, which leads to an increase in the tension CV value of DTY, a decrease in the AAA rate, and a decrease in the staining M rate.

[0086] Comparative Example 2a

[0087] A method for preparing fine denier POY differs from Example 1a only in that steps (4.2)-(4.4) are omitted, that is, the length of each airless duct is always 20mm, and the length of the airless duct is no longer dynamically adjusted.

[0088] The thermal stress CV value of the fine denier POY produced in the same batch was 4.01%.

[0089] Compared with Example 1a, the thermal stress CV value of the same batch of fine denier POY in Comparative Example 2a increased by 2.29%. This is because although a ductless filter element is installed inside the filter element, the length of the ductless filter element is not dynamically adjusted. The length of the ductless filter element is only relatively increased. The temperature difference of the melt stream during cooling still exists, resulting in the thermal stress still being dispersed.

[0090] Comparative Example 2b

[0091] A method for preparing DTY using fine denier POY via a texturing process, differing from Example 1b only in that the fine denier POY is provided by Comparative Example 2a.

[0092] The tension CV value of the prepared DTY was 4.03%; the quality grade of DTY was AA 95.3%, AAA 30.1%, and staining M 31.4%.

[0093] Compared with Example 1b, the quality grade AA rate of DTY in Comparative Example 2b did not change significantly, the tension CV value of DTY increased by 2.3%, the quality grade AAA rate of DTY decreased by 50%, and the dyeing M rate decreased by 51.6%. This is because the thermal stress CV value of fine denier POY is still relatively high, which leads to an increase in the tension CV value of DTY. The AAA rate of DTY is still not high, and the dyeing M rate is also reduced.

[0094] Example 2a

[0095] A method for preparing fine denier POY with uniform thermal stress, using the following method: Figures 1-8 The apparatus shown is used in the following steps:

[0096] (1) Prepare raw materials;

[0097] Melt: PET, intrinsic viscosity 0.65 dL / g;

[0098] (2) Melt transport;

[0099] The temperature of the melt is 282℃;

[0100] (3) Melt extrusion forms a melt stream;

[0101] The melt enters 10 spinning stations, each spinning station is equipped with a spinning box 4, each spinning box 4 is equipped with 10 spindles, each spindle is equipped with a spinning assembly, the temperature of the spinning box 4 is 290℃, the spinneret has 96 holes, the diameter of the spinneret is 85mm, and the orifice diameter of the spinneret is 0.15mm.

[0102] (4) Circular air blowing cooling;

[0103] (4.1) The melt stream enters 10 spinning positions. Each spinning position is equipped with a ring blower box 3. Each ring blower box 3 is equipped with 10 spindles. The top of the ring blower box 3 is equipped with an assembly hole 31 corresponding to each spindle. A cylindrical filter element 2 is installed in each assembly hole 31. The peripheral wall of the filter element 2 is equipped with ventilation holes 21. A non-air tube 1 is inserted in each filter element 2. The outer diameter of the non-air tube 1 is equal to the inner diameter of the filter element 2. The top of the outer wall of the non-air tube 1 is fixed with a radial protrusion 11 in a one-time forming method. The protrusion 11 is annular and the axial thickness of the protrusion 11 is equal. The protrusion 11 is hung on the top of the filter element 2. The non-air tube 1 and the filter element 2 are coaxial. The length of the filter element 2 is 190mm and the length of each non-air tube 1 is 20mm.

[0104] (4.2) Each spindle first spins out 1 spindle of fine denier POY, and a total of 100 spindles of fine denier POY are obtained. After detecting the thermal stress value of these 100 spindles of fine denier POY, the average thermal stress value μ1 is calculated.

[0105] (4.3) Each spindle continues to spin 1 spindle of fine denier POY, resulting in a total of 100 spindles of fine denier POY. The thermal stress value of these 100 spindles of fine denier POY is then tested.

[0106] (4.4) Compare the thermal stress value of the fine denier POY spun from each spindle with μ1, make adjustments based on the comparison results, and return to step (4.3) after adjustment.

[0107] The adjustment refers to the following: for spindles where the thermal stress value of the fine denier POY produced is greater than 1.03 times μ1, the corresponding airless tube 1 is replaced with a longer airless tube 1, increasing the length by 1.0 mm; for spindles where the thermal stress value of the fine denier POY produced is less than 0.97 times μ1, the corresponding airless tube 1 is replaced with a shorter airless tube 1, decreasing the length by 1.0 mm.

[0108] The thermal stress CV value of the fine denier POY produced in the same batch (i.e., all fine denier POY spun from the above 100 spindles) was 1.69%.

[0109] Example 2b

[0110] A method for preparing DTY using fine denier POY via a texturing process, wherein the fine denier POY is provided in Example 2a;

[0111] The parameters for the texturing process are: stretch ratio 1.6, texturing speed 750m / min, deformation temperature 180℃, setting temperature 140℃, false twist tension 21cN, winding tension 8cN, friction disc type PU disc, and D / Y ratio 1.65.

[0112] The tension CV value of the prepared DTY was 1.69%; the quality grade of DTY was AA 95.3%, AAA 81.2% and M staining 84.1%.

[0113] Example 3a

[0114] A method for preparing fine denier POY with uniform thermal stress, using the following method: Figures 1-8 The apparatus shown is used in the following steps:

[0115] (1) Prepare raw materials;

[0116] Melt: PET, intrinsic viscosity 0.70 dL / g;

[0117] (2) Melt transport;

[0118] The temperature of the melt is 285℃;

[0119] (3) Melt extrusion forms a melt stream;

[0120] The melt enters 10 spinning stations, each spinning station is equipped with a spinning box 4, each spinning box 4 is equipped with 10 spindles, each spindle is equipped with a spinning assembly, the temperature of the spinning box 4 is 290℃, the spinneret has 96 holes, the diameter of the spinneret is 85mm, and the orifice diameter of the spinneret is 0.15mm.

[0121] (4) Circular air blowing cooling;

[0122] (4.1) The melt stream enters 10 spinning positions. Each spinning position is equipped with a ring blower box 3. Each ring blower box 3 is equipped with 10 spindles. The top of the ring blower box 3 is equipped with an assembly hole 31 corresponding to each spindle. A cylindrical filter element 2 is installed in each assembly hole 31. The peripheral wall of the filter element 2 is equipped with ventilation holes 21. A non-air tube 1 is inserted in each filter element 2. The outer diameter of the non-air tube 1 is equal to the inner diameter of the filter element 2. The top of the outer wall of the non-air tube 1 is fixed with a radial protrusion 11 in a one-time forming method. The protrusion 11 is annular and the axial thickness of the protrusion 11 is equal. The protrusion 11 is hung on the top of the filter element 2. The non-air tube 1 and the filter element 2 are coaxial. The length of the filter element 2 is 190mm and the length of each non-air tube 1 is 20mm.

[0123] (4.2) Each spindle first spins out 1 spindle of fine denier POY, and a total of 100 spindles of fine denier POY are obtained. After detecting the thermal stress value of these 100 spindles of fine denier POY, the average thermal stress value μ1 is calculated.

[0124] (4.3) Each spindle continues to spin 1 spindle of fine denier POY, resulting in a total of 100 spindles of fine denier POY. The thermal stress value of these 100 spindles of fine denier POY is then tested.

[0125] (4.4) Compare the thermal stress value of the fine denier POY spun from each spindle with μ1, make adjustments based on the comparison results, and return to step (4.3) after adjustment.

[0126] The adjustment refers to the following: for spindles where the thermal stress value of the fine denier POY produced is greater than 1.03 times μ1, the corresponding airless tube 1 is replaced with a longer airless tube 1, increasing the length by 1.0 mm; for spindles where the thermal stress value of the fine denier POY produced is less than 0.97 times μ1, the corresponding airless tube 1 is replaced with a shorter airless tube 1, decreasing the length by 1.0 mm.

[0127] The thermal stress CV value of the fine denier POY produced in the same batch (i.e., all fine denier POY spun from the above 100 spindles) was 1.68%.

[0128] Example 3b

[0129] A method for preparing DTY using fine denier POY via a texturing process, wherein the fine denier POY is provided in Example 3a;

[0130] The parameters for the texturing process are: stretch ratio 1.6, texturing speed 750m / min, deformation temperature 180℃, setting temperature 140℃, false twist tension 25cN, winding tension 8cN, friction disc type PU disc, and D / Y ratio 1.65.

[0131] The tension CV value of the prepared DTY was 1.68%; the quality grade of DTY was AA (95.2%), AAA (81.1%), and M (84.2%).

[0132] Example 4a

[0133] A method for preparing fine denier POY with uniform thermal stress, using the following method: Figures 1-8 The apparatus shown is used in the following steps:

[0134] (1) Prepare raw materials;

[0135] Melt: PET, intrinsic viscosity 0.68 dL / g;

[0136] (2) Melt transport;

[0137] The temperature of the melt is 283℃;

[0138] (3) Melt extrusion forms a melt stream;

[0139] The melt enters 10 spinning stations, each spinning station is equipped with a spinning box 4, each spinning box 4 is equipped with 10 spindles, each spindle is equipped with a spinning assembly, the temperature of the spinning box 4 is 291℃, the spinneret has 96 holes, the diameter of the spinneret is 85mm, and the orifice diameter of the spinneret is 0.15mm.

[0140] (4) Circular air blowing cooling;

[0141] (4.1) The melt stream enters 10 spinning positions. Each spinning position is equipped with a ring blower box 3. Each ring blower box 3 is equipped with 10 spindles. The top of the ring blower box 3 is equipped with an assembly hole 31 corresponding to each spindle. A cylindrical filter element 2 is installed in each assembly hole 31. The peripheral wall of the filter element 2 is equipped with ventilation holes 21. A non-air tube 1 is inserted in each filter element 2. The outer diameter of the non-air tube 1 is equal to the inner diameter of the filter element 2. The top of the outer wall of the non-air tube 1 is fixed with a radial protrusion 11 in a one-time forming method. The protrusion 11 is annular and the axial thickness of the protrusion 11 is equal. The protrusion 11 is hung on the top of the filter element 2. The non-air tube 1 and the filter element 2 are coaxial. The length of the filter element 2 is 190mm and the length of each non-air tube 1 is 20mm.

[0142] (4.2) Each spindle first spins out 1 spindle of fine denier POY, and a total of 100 spindles of fine denier POY are obtained. After detecting the thermal stress value of these 100 spindles of fine denier POY, the average thermal stress value μ1 is calculated.

[0143] (4.3) Each spindle continues to spin 1 spindle of fine denier POY, resulting in a total of 100 spindles of fine denier POY. The thermal stress value of these 100 spindles of fine denier POY is then tested.

[0144] (4.4) Compare the thermal stress value of the fine denier POY spun from each spindle with μ1, make adjustments based on the comparison results, and return to step (4.3) after adjustment.

[0145] The adjustment refers to the following: for spindles where the thermal stress value of the fine denier POY produced is greater than 1.03 times μ1, the corresponding airless tube 1 is replaced with a longer airless tube 1, increasing the length by 0.8 mm; for spindles where the thermal stress value of the fine denier POY produced is less than 0.97 times μ1, the corresponding airless tube 1 is replaced with a shorter airless tube 1, decreasing the length by 0.8 mm.

[0146] The thermal stress CV value of the fine denier POY produced in the same batch (i.e. all fine denier POY spun from the above 100 spindles) was 1.66%.

[0147] Example 4b

[0148] A method for preparing DTY using fine denier POY via a texturing process, wherein the fine denier POY is provided in Example 4a;

[0149] The parameters for the texturing process are: stretch ratio 1.6, texturing speed 750m / min, deformation temperature 180℃, setting temperature 140℃, false twist tension 22cN, winding tension 8cN, friction disc type PU disc, and D / Y ratio 1.65.

[0150] The tension CV value of the prepared DTY was 1.67%; the quality grade of DTY was AA (95.3%), AAA (83.4%), and M (85.2%).

Claims

1. A method for preparing fine denier POY with uniform thermal stress, comprising a ring-blowing cooling step, characterized in that: The steps for ring-blown cooling are as follows: (a) The melt stream enters m spinning positions, where m is a positive integer. Each spinning position is equipped with a ring blower box (3). Each ring blower box (3) is equipped with n spindle positions, where n is an integer not less than 10. Each spindle position is equipped with a cylindrical filter element (2). The cylindrical wall of the filter element (2) is provided with radial ventilation holes (21). Each filter element (2) is equipped with a non-air duct (1). The length of the non-air duct (1) is less than the length of the filter element (2). The melt stream passes through the non-air duct (1). (b) Each spindle first spins out 1 spindle of fine denier POY. After detecting the thermal stress value of the fine denier POY spun out by all spindles, the average thermal stress value μ1 is calculated. (c) Each spindle continues to spin 1 spindle of fine denier POY, and the thermal stress value of the fine denier POY spun by all spindles is detected; (d) Compare the thermal stress value of the fine denier POY spun from each spindle with μ1, make adjustments based on the comparison results, and return to step (c) after adjustment. The adjustment refers to replacing the corresponding airless tube (1) with a longer airless tube (1) for spindles where the thermal stress value of the fine denier POY produced is greater than 1.03 times μ1; and replacing the corresponding airless tube (1) with a shorter airless tube (1) for spindles where the thermal stress value of the fine denier POY produced is less than 0.97 times μ1.

2. The method for preparing fine denier POY with uniform thermal stress as described in claim 1, characterized in that: In step (a), the length of the filter element (2) is 190 mm, and the length of the air duct (1) is 20 mm.

3. The method for preparing fine denier POY with uniform thermal stress as described in claim 2, characterized in that: In step (d), the length of the replaced airless duct (1) is increased or decreased by 0.8-1.2 mm.

4. The method for preparing fine denier POY with uniform thermal stress as described in claim 1, characterized in that: In step (a), a radial protrusion (11) is fixed to the top of the outer wall of the airless duct (1).

5. The method for preparing fine denier POY with uniform thermal stress as described in claim 4, characterized in that: The protrusion (11) is annular, and the axial thickness of the protrusion (11) is equal.

6. The method for preparing fine denier POY with uniform thermal stress as described in claim 1, characterized in that: In step (a), the outer diameter of the airless duct (1) is equal to the inner diameter of the filter element (2).

7. A fine denier POY with uniform thermal stress, characterized in that: The fine denier POY with uniform thermal stress was prepared by any one of claims 1-6, and the thermal stress CV value of all fine denier POY spun by all spindles was <2%.

8. A fine denier POY with uniform thermal stress as described in claim 7, characterized in that: Fine denier POY with uniform thermal stress is made of polyester, nylon 6, or nylon 66.

9. A method for preparing DTY using fine denier POY through a texturing process, characterized in that: The fine denier POY uses the thermally stress-uniform fine denier POY as described in any one of claims 7-8; The parameters for the texturing process are: stretch ratio 1.5-1.9, texturing speed 600-1000m / min, deformation temperature 170-200℃, setting temperature 120-150℃, false twist tension 20-25cN, winding tension 7-8cN, friction disc type PU disc, and D / Y ratio 1.5-1.

7.

10. A DTY, characterized in that: The method described in claim 9 for preparing DTY using fine denier POY through a texturing process is used; DTY tension CV value <2%; DTY quality grade AA rate >95%, AAA rate >80%, staining M rate >80%.

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