A method for producing veneers from fine denier porous polyester fibers

Abstract

This invention belongs to the field of textile materials and processing technology, and relates to a method for producing veneers of fine denier porous polyester fiber. The method includes a spinning process and a cooling process, wherein the cooling process sequentially involves a first-stage annular air cooling, a second-stage annular air cooling, and a third-stage side-air cooling. At the boundary between the annular and side-air cooling zones, the hot air flowing downwards from the annular cooling zone, which affects the side-air cooling effect, is cooled and its downward movement is blocked. The specifications of the fine denier porous polyester fiber are 368-580 dtex / 548-576F. This invention uses a three-stage cooling process, and by reasonably setting parameters such as the annular air pressure, it avoids problems such as yarn twisting, fuzzing, breakage, and increased unevenness caused by improper annular air pressure, effectively reducing fiber quality issues.

Description

Technical Field

[0001] This invention belongs to the field of textile materials and processing technology, and relates to a method for producing veneers of fine denier porous polyester fibers. Background Technology

[0002] In the textile industry, polyester fibers, especially fine denier porous polyester fibers, enjoy wide applications due to their superior physical properties. Fabrics made from these fibers are not only lightweight but also possess excellent breathability, drape, and softness, making them the preferred material for high-end fabrics such as imitation silk and lightweight brushed fabrics, demonstrating promising market prospects and significant economic benefits. Specifically, fine denier porous polyester fibers with specifications of 368-580 dtex / 548-576F play an important role in high-end fabric manufacturing and many other fields.

[0003] However, the production of these high-performance fibers, especially in the pursuit of efficient and high-quality veneer production methods, faces a series of technical challenges. Traditional multi-strand plying production methods, such as those described in patent application CN101078135A, while improving production efficiency to some extent, are prone to problems such as poor fiber bundle cohesion and tail fiber dispersion during the winding and plying process. These issues severely affect the tail fiber yield in subsequent texturing processes, thereby reducing the overall product quality.

[0004] To address the aforementioned issues, a single-spindle production method has emerged. This method directly produces fibers using a single spinneret, which not only increases unit output but also effectively improves the bundled properties of the tail yarns. However, due to the large number of pores in fine denier polyester porous fibers, extremely high requirements are placed on the cooling process. Existing cooling processes are inadequate for handling such high-pore-count fibers. The literature (Discussion on the direct spinning process of high linear density fine denier polyester pre-oriented yarn single-spindle spinning [J]. Modern Textile Technology. 2013, (4): 1-3.) points out that when the ring blowing pressure is set too low, the cooling air volume is insufficient to cool the yarn bundle evenly and sufficiently, leading to an increase in yarn evenness and breakage, which seriously affects the continuity and uniformity of the fiber. Conversely, if the ring blowing pressure is increased, although the cooling speed can be accelerated, excessive cooling will cause the yarn bundle to vibrate violently, increasing the risk of quality defects such as yarn bundling, which is also not conducive to improving fiber quality.

[0005] Therefore, developing a cooling process that can effectively meet the production needs of polyester fine denier porous fiber veneer is key to improving the overall performance of the fiber, ensuring production efficiency and product quality. Summary of the Invention

[0006] The purpose of this invention is to solve the problems existing in the prior art and provide a method for producing veneers of polyester fine denier porous fibers.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for producing veneers of fine denier porous polyester fiber includes a spinning process of a spinning assembly and a cooling process, wherein the cooling process sequentially includes a first stage of ring-blowing cooling, a second stage of ring-blowing cooling, and a side-blowing cooling.

[0009] During the first stage of ring air cooling, the ring air pressure is 25-28Pa, and the length of the first ring air blower is 10-12cm.

[0010] During the second stage of ring air cooling, the ring air pressure is 32-35Pa, and the length of the second ring air blower is 8-14cm.

[0011] The total length of the first ring blower, the second ring blower, and the side blowing mesh is 66-73cm, and the side blowing speed is 0.60-0.70m / s;

[0012] At the junction of the annular air cooling zone and the side air cooling zone, the hot air flowing downward from the annular air cooling zone that affects the side air cooling effect is cooled and its downward movement is blocked.

[0013] The specifications of fine denier porous polyester fiber are 368-580 dtex / 548-576f.

[0014] Because polyester fine denier porous fibers have a large number of pores, when the ring-blowing air pressure is low, the cooling air volume is insufficient, failing to cool the fiber bundle evenly and fully, resulting in increased fiber unevenness and breakage. When the ring-blowing air pressure is high, the fiber bundle cools faster, intensifying fiber oscillation and causing problems such as yarn bundling. To solve this problem, this invention implements cooling in three stages: a first-stage ring-blowing cooling, a second-stage ring-blowing cooling, and a side-blowing cooling.

[0015] The first stage is the state before the molten stream is stretched and solidified. The fiber diameter gradually decreases from its maximum diameter in the windless zone (expansion zone at the spinneret exit) until it stabilizes. During this stage, a slightly lower annular blowing pressure (25-28 Pa) can prevent fiber tangling caused by excessive pressure. Since this is the expansion and stretching zone, the fiber is not fully solidified and is easily affected by the lateral force of the cooling air. Because the annular blowing pressure is relatively low at this stage, the length of the first annular blower is set to 10-12 cm to match this specific state of the fiber, reducing interference and preventing fiber vibration and tangling. If the annular blowing pressure is too high, the numerous fiber pores cause the incompletely solidified fiber to be impacted by the strong airflow, leading to lateral vibration, tangling, fuzzing, and even breakage. If the annular blowing pressure is too low, the cooling efficiency is insufficient, the molten stream cannot solidify in time, and the fiber is prone to breakage during subsequent stretching. If the length of the first ring blower is too large or too small, it will amplify the window effect of the wind pressure parameters, making the abnormal situation more serious.

[0016] The second stage is still the state before the fiber bundle solidifies. If the ring blowing pressure is too low, the air velocity in the center of the polyester fine denier porous fiber ring blower will be very low, resulting in poor cooling effect. This easily leads to a large radial temperature gradient difference in the cross-section of the fiber, causing differences in the radial cross-sectional structure of the fiber. This results in problems such as lower fiber breaking strength, increased evenness, and increased breakage frequency. If the ring blowing pressure is too high, adjacent monofilaments will vibrate at the same frequency, increasing the probability of yarn bundling to 3-5 times that under normal operating conditions. If the length of the second ring blower is too large, it will exacerbate the Bernoulli effect, increasing the frequency of transverse pulsating airflow impact on the fiber and causing significant shaking. If the length of the second ring blower is too small, the cooling air travels a short distance, leading to an increase in the proportion of residual melt in the fiber core layer, which in turn increases the fiber evenness.

[0017] Single-ring airflow cooling, due to its short cooling distance, can lead to segmented cooling abnormalities, similar to bamboo-joint filaments, resulting in abnormally high product evenness. This invention employs side-blowing cooling after the second ring airflow cooling. The side-blowing cooling conditions are relatively intense (side-blowing velocity of 0.60-0.70 m / s), allowing for rapid cooling of the fiber bundle. The total length of the first ring airflow duct, the second ring airflow duct, and the side-blowing mesh is 66-73 cm, ensuring uniform fiber cooling and good fiber evenness. Excessive side-blowing velocity can easily lead to a core-sheath structure. The high-speed airflow causes the fiber surface to vitrify instantaneously, forming a brittle sheath (this brittle sheath reduces the elongation at break by 30-40%), while the core melt flow is obstructed, leading to internal stress cracks. Insufficient side-blowing velocity results in inadequate cooling, causing elastic shrinkage of the fiber during stretching, increasing diameter fluctuations, and raising the unevenness of the finished fiber. However, if the length of the side-blowing mesh is too large or too small, it will amplify the window effect of the wind speed parameter, making the abnormal situation more serious.

[0018] Furthermore, due to the large number of pores in the fine denier porous polyester fiber, the temperature inside the second ring blower is high. When the filament bundle leaves the second ring blower, a large amount of hot air at a high temperature blows vertically downwards. At the moment the filament bundle contacts the side blower, the side blower is blocked by the hot air and heated up. This results in a worse cooling effect on the filament the further away from the side blower outlet. Therefore, this invention cools the hot air flowing downwards from the ring blower cooling zone that affects the side blower cooling effect at the junction of the ring blower cooling zone and the side blower cooling zone, and blocks its downward movement, thereby ensuring more uniform cooling when transitioning from ring blower to side blower.

[0019] As a preferred technical solution:

[0020] As described above, in a method for producing veneers of fine denier porous polyester fibers, the first ring blower and the second ring blower are the upper and lower sections of the same ring blower, the inner diameters of the first ring blower and the second ring blower are the same, the mesh size of the first ring blower is 0.110-0.114mm, and the mesh size of the second ring blower is 0.220-0.228mm.

[0021] The method for producing veneers of polyester fine denier porous fibers as described above involves cooling the hot air flowing downwards from the annular cooling zone, which affects the cooling effect of the side blowing, and preventing its downward movement at the junction of the annular cooling zone and the side blowing cooling zone, as follows:

[0022] A C-shaped plate is installed at the lower end of the second ring blower. The C-shaped plate is made of alloy with a thermal conductivity of 300-350W / m·K. It is hollow inside and connected to the circulating cooling water pipeline.

[0023] The area between the filament bundle and the second ring blower is a ring-shaped area, which consists of a symmetrical first semi-ring area and a second semi-ring area. The axis of symmetry of the two is parallel to the side-blowing mesh plate. The second semi-ring area is close to the side-blowing mesh plate, and the second semi-ring area completely coincides with the orthographic projection of the C-shaped plate.

[0024] In the above-described method for producing single-layer polyester fine denier porous fibers, the lower end face of the second ring blower is parallel to the horizontal plane, and the angle between the C-shaped plate and the horizontal plane is 30°. This avoids the downward hot air, which affects the side blowing cooling effect, becoming too disordered after being affected by the C-shaped plate, thus preventing adverse effects on the fiber bundle.

[0025] In the above-described method for producing veneers of fine denier porous polyester fiber, a second ring blower is installed on a blower frame. A hinge is installed at the bottom of the blower box, with the hinge's axis arranged horizontally and parallel to the side-blowing mesh plate. One hinge leaf is fixedly connected to the bottom of the blower box, and the other hinge leaf is fixedly connected to the C-shaped plate at the position closest to the side-blowing mesh plate. This leaf leaf is connected to the bottom of the blower box via a magnetic attraction device, resulting in a 30° angle between the C-shaped plate and the horizontal plane. When the stop position is reopened, the C-shaped plate is not needed. At this time, the magnetic attraction device is removed, allowing the C-shaped plate to hang down naturally under gravity.

[0026] In the above-described method for producing veneers of polyester fine denier porous fiber, the temperature of the circulating cooling water transported by the circulating cooling water pipeline is 23-25℃, and the flow rate is 0.08-0.1L / min.

[0027] The above-described method for producing veneers of fine denier porous polyester fiber comprises the following overall process flow: spinning assembly → cooling → spinning oiling → first guide roller → pre-networking → second guide roller → winding and forming.

[0028] The method for producing veneers of polyester fine denier porous fiber as described above includes a spinneret with a diameter of 120 mm, spinneret orifice diameter of 0.14-0.16 mm, spinneret orifice length of 0.50-0.52 mm, spinning box temperature of 287-289℃, windless zone length of 50-60 mm, cooling air temperature of 20-22℃, cooling air relative humidity of 75-85%, bundling height of 850-950 mm, first guide roller speed of 2680-2855 m / min, second guide roller speed of 2685-2860 m / min, pre-network pressure of 0.08-0.09 MPa, and winding speed of 2665-2840 m / min.

[0029] The method for producing veneers of polyester fine denier porous fiber as described above has the following characteristics: the tensile strength of the polyester fine denier porous fiber is ≥2.45 cN / dtex, the tensile strength CV value is ≤3.09%, the tensile elongation at break is 124.1-126.9%, the tensile elongation at break CV value is ≤2.81%, the yarn unevenness is ≤1.24%, the number of breaks is ≤2.5 times / 18 positions·24 hours, and the thermal stress deviation is ≤M×3%; M is the thermal stress center value, in cN.

[0030] Beneficial effects:

[0031] This invention performs cooling in three stages (first stage annular air cooling, second stage annular air cooling and side air cooling). By reasonably setting parameters such as annular air pressure, problems such as yarn twisting, fuzzing, yarn breakage and increased yarn unevenness caused by improper annular air pressure are avoided, effectively reducing fiber quality problems. Attached Figure Description

[0032] Figure 1 Front view of the device used for cooling the filament bundle;

[0033] Figure 2 A side view of the apparatus used for cooling the filament bundle;

[0034] Figure 3 A bottom view of the device used for cooling the filament bundle;

[0035] Among them, 1-wind box, 2-first ring air blower, 3-second ring air blower, 4-C-shaped plate, 5-side blowing mesh plate, 6-circulating cooling water conveying pipeline, 7-air blower frame, 8-hinge. Detailed Implementation

[0036] 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.

[0037] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0038] Tensile strength, tensile strength CV value, elongation at break, and elongation at break CV value: The polyester fibers prepared in each example were tested using a fully automatic single-yarn tensile testing machine (model YG023B-Ⅱ) according to GB / T 14344-2022 "Test Method for Tensile Properties of Chemical Fiber Filaments". The specific process was as follows: First, the polyester fibers were conditioned in an environment with a temperature of 20℃ and a humidity of 65% for 4 hours. Then, they were clamped by upper and lower clamps (clamping length of 250mm), and a pretension of 0.05cN / dtex was applied by a robotic arm to stabilize the polyester fibers. At the start of the test, the lower clamp was stretched uniformly at a speed of 1000mm / min until the fibers broke. Real-time data from the force sensor was recorded during the stretching process, and the relationship curve between strength and elongation was plotted using a data collection system. Finally, the tensile strength, tensile strength CV value, elongation at break, and elongation at break CV value of the fibers were obtained through data processing and analysis.

[0039] Evenness: According to the "Test Method for Evenness of Chemical Fiber Filaments - Capacitive Method" (GB / T 14346-2015), the USTER5 evenness tester was used for testing. The specific process is as follows: First, the filament bundle is placed in an environment with a temperature of 20℃ and a humidity of 65% for 2 hours to adjust the humidity. Then, the filament bundle is passed through the two plates of a capacitor at a uniform speed, and the mass in each equal interval is converted into an electrical signal. The percentage of the standard deviation of all test electrical signals to the average value is the evenness. The test speed is 200 m / min, and the filament bundle test time is 2.5 min.

[0040] Number of spindle breaks: Spindle breakage refers to the sudden breakage of a single filament during spinning. One spindle breakage is counted as one breakage. A statistical period of 10 days and 18 spindle positions is used as a statistical period. The number of spindle breaks in 24 hours and 18 spindle positions is calculated based on the average value.

[0041] Thermal stress deviation: Thermal stress deviation = measured thermal stress - thermal stress center value; The measured thermal stress is tested according to the standard "Dynamic Thermal Stress Test Method for Polyester Pre-oriented Yarn" (FZ / T 50051-2020) using a YG 367 thermal stress tester; Before the test, the yarn bundle is conditioned in an environment with a temperature of (20±2)℃ and a humidity of (65±5)% for 4 hours; Then, the yarn bundle is passed through the heating device and the drawing device at a specific speed and pre-tension (the specific speed and pre-tension parameters are set according to the standard); The tensile stress generated by the yarn bundle under heating conditions is the measured thermal stress; Thermal stress center value: For products produced under normal process conditions, the thermal stress center value is determined by negotiation between the supplier and the buyer after testing according to the standard "Dynamic Thermal Stress Test Method for Polyester Pre-oriented Yarn" (FZ / T 50051-2020).

[0042] A device for cooling filament bundles, such as Figures 1-3 As shown, it includes a wind box 1, a ring-shaped air duct, a C-shaped plate 4, a side-blowing mesh plate 5, a circulating cooling water conveying pipeline 6, an air duct frame 7, a hinge 8, and a magnetic suction device;

[0043] like Figure 1 , Figure 2 As shown, the ring blower consists of a first ring blower 2 located in the upper section and a second ring blower 3 located in the lower section. The inner diameters of the first ring blower 2 and the second ring blower 3 are the same. The length of the first ring blower 2 is 10-12cm, and the length of the second ring blower 3 is 8-14cm. The total length of the first ring blower 2, the second ring blower 3, and the side blowing mesh plate 5 is 66-73cm. The mesh aperture of the first ring blower 2 is 0.110-0.114mm, and the mesh aperture of the second ring blower 3 is 0.220-0.228mm.

[0044] like Figure 1 , Figure 3As shown, the C-shaped plate 4 is installed at the lower end of the second ring blower 3. The C-shaped plate 4 is made of alloy with a thermal conductivity of 300-350W / m·K. It is hollow inside and connected to the circulating cooling water supply pipeline 6. The lower end face of the second ring blower 3 is parallel to the horizontal plane, and the angle between the C-shaped plate 4 and the horizontal plane is 30°.

[0045] like Figure 3 As shown, the area between the filament bundle and the second ring blower 3 is a ring area. The ring area is composed of a symmetrical first semi-ring area and a second semi-ring area. The axis of symmetry of the two is parallel to the side blowing mesh plate 5. The second semi-ring area is close to the side blowing mesh plate 5. The second semi-ring area completely coincides with the orthographic projection of the C-shaped plate 4.

[0046] The second ring blower 3 is installed on the blower frame 7, and the hinge 8 is installed at the bottom of the air box 1. The axis of the hinge 8 is arranged horizontally and parallel to the side blowing mesh plate 5. One leaf of the hinge 8 is fixedly connected to the bottom of the air box 1, and the other leaf of the hinge 8 is fixedly connected to the C-shaped plate 4 at the position closest to the side blowing mesh plate 5. This leaf is connected to the bottom of the air box 1 through a magnetic attraction device.

[0047] Example 1

[0048] A method for producing veneers from fine denier porous polyester fibers, comprising the following specific steps:

[0049] (1) Synthesis of polyester melt;

[0050] The overall process flow is as follows: slurry preparation → first esterification → second esterification → pre-polymerization → final polymerization → polyester melt;

[0051] Relevant process parameters: slurry temperature is 65℃, slurry level is 80%, and the mass of PTA in the slurry accounts for 69% of the total mass of PTA and EG; the temperature of the first esterification is 260℃ and the pressure is 80KPa; the temperature of the second esterification is 268℃ and the pressure is 30KPa; the upper chamber temperature of the pre-polymerization is 276℃, the lower chamber temperature is 282℃, the upper chamber pressure is 10KPa, and the lower chamber pressure is 1.8KPa; the final polycondensation pressure is 180Pa, the inlet temperature of the final polycondensation is 280℃, the middle temperature is 283℃, and the outlet temperature is 286℃.

[0052] The intrinsic viscosity of the synthesized polyester melt is 0.62 dL / g;

[0053] (2) Spinning;

[0054] The overall process flow is as follows: spinning assembly spinning → first stage ring air cooling → second stage ring air cooling → side air cooling → spinning oiling → first guide roller → pre-networking → second guide roller → winding and forming;

[0055] The dimensional parameters of the spinneret in the spinning assembly are as follows: the diameter of the spinneret is 120 mm, the diameter of the spinneret orifice is 0.14 mm, and the length of the spinneret orifice is 0.52 mm.

[0056] The first-stage annular air cooling, the second-stage annular air cooling, and the side-blowing air cooling all employ the device for cooling the filament bundle as described above. The first-stage annular air cooling uses a first-ring air blower, the second-stage annular air cooling uses a second-ring air blower, and the side-blowing air cooling uses a side-blowing mesh plate. The relevant parameters of the device for cooling the filament bundle are as follows: the length of the first-ring air blower is 10cm, the length of the second-ring air blower is 14cm, the total length of the first-ring air blower, the second-ring air blower, and the side-blowing mesh plate is 66cm, the mesh aperture of the first-ring air blower is 0.11mm, the mesh aperture of the second-ring air blower is 0.22mm, and the thermal conductivity of the C-shaped plate is 300W / m·K. The temperature of the circulating cooling water transported by the circulating cooling water pipeline is 24℃, and the flow rate is 0.08L / min.

[0057] Relevant process parameters: spinning box temperature is 287℃; length of the windless zone is 56mm; cooling air temperature is 20℃; relative humidity of cooling air is 75%; during the first stage of ring-blown cooling, the ring-blown air pressure is 25Pa; during the second stage of ring-blown cooling, the ring-blown air pressure is 32Pa; during side-blown cooling, the side-blown air velocity is 0.6m / s; bundling height is 850mm; speed of the first guide roller is 2680m / min; speed of the second guide roller is 2685m / min; pre-network pressure is 0.08MPa; winding speed is 2665m / min.

[0058] The final polyester fine denier porous fiber has the following specifications: 368 dtex / 548f, breaking strength: 2.45 cN / dtex, breaking strength CV value: 2.73%, breaking elongation: 126.9%, breaking elongation CV value: 2.41%, yarn unevenness: 0.98%, number of breaks: 2.3 times / 18 positions·24 hours, thermal stress center value: 160 cN, thermal stress deviation: 3 cN.

[0059] Comparative Example 1

[0060] A method for producing veneers of fine denier porous polyester fibers differs from Example 1 only in that the ring blowing pressure is 23 Pa during the first stage of ring blowing cooling.

[0061] The final polyester fine denier porous fiber had a yarn unevenness of 1.45% and a breakage rate of 4.8 times / 18 positions·24 hours.

[0062] Compared with Example 1, the unevenness and number of breaks of polyester fine denier porous fiber were significantly increased. This is because during the first stage of cooling by the ring blowing air in Comparative Example 1, the ring blowing air pressure was relatively small and the cooling air volume was insufficient, which could not cool the fiber bundle evenly and fully, thus increasing the unevenness and number of breaks of the fiber bundle.

[0063] Comparative Example 2

[0064] A method for producing veneers of fine denier porous polyester fibers differs from Example 1 only in that the ring blowing pressure is 30 Pa during the second stage of ring blowing cooling.

[0065] The final polyester fine denier porous fiber had a yarn unevenness of 1.90% and a breakage rate of 6.3 times / 18 positions·24 hours.

[0066] Compared with Example 1, Comparative Example 2 showed a significant increase in the unevenness and number of breaks of polyester fine denier porous fibers. This is because during the second stage of annular air cooling in Comparative Example 2, the annular air pressure was relatively low and the cooling air volume was insufficient, which could not cool the fiber bundle evenly and fully, thus increasing the unevenness and number of breaks of the fiber bundle.

[0067] Comparative Example 3

[0068] A method for producing veneers of fine denier porous polyester fiber differs from Example 1 only in that the length of the first ring blower is 8 cm.

[0069] The final polyester fine denier porous fiber had a yarn unevenness rate of 1.41% and a breakage rate of 8.2 times / 18 positions·24 hours.

[0070] Compared with Example 1, Comparative Example 3 showed a significant increase in the unevenness and breakage rate of polyester fine denier porous fibers. This is because the length of the first ring blower in Comparative Example 3 was too short, which made it impossible to match the smaller ring blower pressure when the fiber was in the expansion zone and stretching zone before it was completely solidified. The insufficient length of the blower and the insufficient distance of the air pressure made the fiber easily affected by the lateral force of the cooling air, which led to increased lateral vibration of the fiber, which in turn caused filament bundling, fuzzing, and even breakage. It also led to an increase in the unevenness of the fiber.

[0071] Comparative Example 4

[0072] A method for producing veneers of fine denier porous polyester fiber differs from Example 1 only in that the length of the second ring blower is 16cm.

[0073] The final polyester fine denier porous fiber had a yarn unevenness rate of 1.49% and a breakage rate of 7.1 times / 18 positions·24 hours.

[0074] Compared with Example 1, Comparative Example 4 showed a significant increase in the evenness and number of breaks of polyester fine denier porous fiber. This is because the length of the second ring blower in Comparative Example 4 was too large, which aggravated the Bernoulli effect and greatly increased the frequency of the fiber being impacted by the transverse pulsating airflow, resulting in significant fiber shaking, which in turn increased the evenness and number of breaks.

[0075] Comparative Example 5

[0076] A method for producing veneers of fine denier porous polyester fiber differs from Example 1 only in that the total length of the first ring blower, the second ring blower, and the side-blowing mesh is 64cm.

[0077] The final polyester fine denier porous fiber had a yarn unevenness of 1.59%, a breakage rate of 10.1 times / 18 positions·24 hours, and a thermal stress deviation of 15.7 cN.

[0078] Compared with Example 1, Comparative Example 5 showed a significant increase in the unevenness of polyester fine denier porous fibers, the number of breakages, and the thermal stress deviation. This is because the total length of the first ring blower, the second ring blower, and the side blower plate in Comparative Example 5 was too small, and the cooling distance of the side blower was insufficient, which could not ensure that the fibers were cooled evenly, resulting in an increase in the unevenness of the finished fibers and an increase in the thermal stress deviation. On the other hand, due to uneven cooling, the fine denier porous fibers were bundled before they were fully cured and formed, resulting in insufficient fiber strength and difficulty in withstanding the external force of bundling, which led to an increase in breakages.

[0079] Comparative Example 6

[0080] A method for producing veneers of fine denier porous polyester fibers differs from Example 1 only in that the side-blowing air velocity is 0.5 m / s during side-blowing cooling.

[0081] The final polyester fine denier porous fiber had a yarn unevenness of 2.09%, a breakage rate of 11.4 times / 18 positions·24 hours, and a thermal stress deviation of 17.2 cN.

[0082] Compared with Example 1, Comparative Example 6 showed a significant increase in the evenness, breakage rate, and thermal stress deviation of the polyester fine denier porous fiber. This is because the side-blowing speed in Comparative Example 6 was too low. On the one hand, the fiber was not cooled sufficiently, resulting in elastic shrinkage during stretching and an increased diameter fluctuation, thus increasing the evenness of the finished fiber. On the other hand, since the fine denier porous fiber was bundled before it was fully cured, the fiber strength was insufficient and it could not withstand the bundled external force, resulting in an increase in breakage. In addition, the low side-blowing speed and the large number of holes in the fiber bundle resulted in inconsistent cooling effects between the areas near and far from the mesh during side-blowing, causing uneven shrinkage inside the fiber and leading to uneven thermal stress distribution, thus increasing the thermal stress deviation.

[0083] Example 2

[0084] A method for producing veneers from fine denier porous polyester fibers, comprising the following specific steps:

[0085] (1) Synthesis of polyester melt;

[0086] The overall process flow is as follows: slurry preparation → first esterification → second esterification → pre-polymerization → final polymerization → polyester melt;

[0087] Relevant process parameters: slurry temperature is 68℃, slurry level is 83%, and the mass of PTA in the slurry accounts for 69.5% of the total mass of PTA and EG; the temperature of the first esterification is 265℃ and the pressure is 90 kPa; the temperature of the second esterification is 270℃ and the pressure is 33 kPa; the upper chamber temperature of the pre-polymerization is 277℃, the lower chamber temperature is 280℃, the upper chamber pressure is 12 kPa, and the lower chamber pressure is 1.9 kPa; the final polycondensation pressure is 200 Pa, the inlet temperature of the final polycondensation is 281℃, the middle temperature is 285℃, and the outlet temperature is 288℃.

[0088] The intrinsic viscosity of the synthesized polyester melt is 0.63 dL / g;

[0089] (2) Spinning;

[0090] The overall process flow is as follows: spinning assembly spinning → first stage ring air cooling → second stage ring air cooling → side air cooling → spinning oiling → first guide roller → pre-networking → second guide roller → winding and forming;

[0091] The dimensional parameters of the spinneret in the spinning assembly are as follows: the diameter of the spinneret is 120 mm, the diameter of the spinneret orifice is 0.16 mm, and the length of the spinneret orifice is 0.5 mm.

[0092] The first-stage annular air cooling, the second-stage annular air cooling, and the side-blowing air cooling all employ the device for cooling the filament bundle as described above. The first-stage annular air cooling uses a first-ring air blower, the second-stage annular air cooling uses a second-ring air blower, and the side-blowing air cooling uses a side-blowing mesh plate. The relevant parameters of the device for cooling the filament bundle are as follows: the length of the first-ring air blower is 11cm, the length of the second-ring air blower is 13cm, the total length of the first-ring air blower, the second-ring air blower, and the side-blowing mesh plate is 72cm, the mesh aperture of the first-ring air blower is 0.113mm, the mesh aperture of the second-ring air blower is 0.226mm, and the thermal conductivity of the C-shaped plate is 350W / m·K. The temperature of the circulating cooling water transported by the circulating cooling water pipeline is 23℃, and the flow rate is 0.09L / min.

[0093] Relevant process parameters: spinning box temperature is 288.5℃; length of the windless zone is 52mm; cooling air temperature is 21.5℃; relative humidity of cooling air is 79%; ring blowing air pressure is 27Pa during the first stage of ring blowing cooling; ring blowing air pressure is 34Pa during the second stage of ring blowing cooling; side blowing air velocity is 0.7m / s during side blowing cooling; bundling height is 870mm; first guide roller speed is 2750m / min; second guide roller speed is 2755m / min; pre-network pressure is 0.09MPa; winding speed is 2740m / min.

[0094] The final polyester fine denier porous fiber has the following specifications: 510 dtex / 576f, breaking strength of 2.56 cN / dtex, breaking strength CV value of 2.81%, breaking elongation of 124.1%, breaking elongation CV value of 2.7%, yarn unevenness of 1.11%, number of breaks of 2 times / 18 positions·24 hours, thermal stress center value of 230 cN, and thermal stress deviation of 5 cN.

[0095] Comparative Example 7

[0096] A method for producing veneers of fine denier porous polyester fiber differs from Example 2 only in that the side-blowing air velocity is 0.8 m / s during side-blowing cooling.

[0097] The final polyester fine denier porous fiber had a yarn unevenness of 1.65%, a breakage rate of 7.8 times / 18 positions·24 hours, and a thermal stress deviation of 25.1 cN.

[0098] Compared with Example 2, the unevenness, number of breaks, and thermal stress deviation of polyester fine denier porous fiber were significantly increased in Comparative Example 7. This is because the side blowing speed in Comparative Example 7 was too high, and the high-speed airflow caused the fiber surface to vitrify instantly, resulting in an increase in the thermal stress deviation of the fiber. At the same time, when the side blowing speed is too high, core structure is more likely to occur, leading to an increase in unevenness and number of breaks.

[0099] Example 3

[0100] A method for producing veneers from fine denier porous polyester fibers, comprising the following specific steps:

[0101] (1) Synthesis of polyester melt;

[0102] The overall process flow is as follows: slurry preparation → first esterification → second esterification → pre-polymerization → final polymerization → polyester melt;

[0103] Relevant process parameters: slurry temperature is 70℃, slurry level is 88%, and the mass of PTA in the slurry accounts for 70% of the total mass of PTA and EG; the temperature of the first esterification is 268℃ and the pressure is 100KPa; the temperature of the second esterification is 273℃ and the pressure is 38KPa; the upper chamber temperature of the pre-polymerization is 278℃, the lower chamber temperature is 281℃, the upper chamber pressure is 13KPa, and the lower chamber pressure is 2KPa; the final polycondensation pressure is 250Pa, the inlet temperature of the final polycondensation is 282℃, the middle temperature is 284℃, and the outlet temperature is 286℃.

[0104] The intrinsic viscosity of the synthesized polyester melt is 0.625 dL / g;

[0105] (2) Spinning;

[0106] The overall process flow is as follows: spinning assembly spinning → first stage ring air cooling → second stage ring air cooling → side air cooling → spinning oiling → first guide roller → pre-networking → second guide roller → winding and forming;

[0107] The dimensional parameters of the spinneret in the spinning assembly are as follows: the diameter of the spinneret is 120 mm, the diameter of the spinneret orifice is 0.15 mm, and the length of the spinneret orifice is 0.51 mm.

[0108] The first-stage annular air cooling, the second-stage annular air cooling, and the side-blowing air cooling all employ the device for cooling the filament bundle as described above. The first-stage annular air cooling uses a first-ring air blower, the second-stage annular air cooling uses a second-ring air blower, and the side-blowing air cooling uses a side-blowing mesh plate. The relevant parameters of the device for cooling the filament bundle are as follows: the length of the first-ring air blower is 12cm, the length of the second-ring air blower is 8cm, the total length of the first-ring air blower, the second-ring air blower, and the side-blowing mesh plate is 73cm, the mesh aperture of the first-ring air blower is 0.114mm, the mesh aperture of the second-ring air blower is 0.228mm, and the thermal conductivity of the C-shaped plate is 320W / m·K. The temperature of the circulating cooling water transported by the circulating cooling water pipeline is 25℃, and the flow rate is 0.1L / min.

[0109] Relevant process parameters: spinning box temperature is 287.5℃; length of the windless zone is 50mm; cooling air temperature is 22℃; relative humidity of cooling air is 85%; during the first stage of ring-blowing cooling, the ring-blowing air pressure is 26Pa; during the second stage of ring-blowing cooling, the ring-blowing air pressure is 35Pa; during side-blowing cooling, the side-blowing air velocity is 0.64m / s; bundling height is 920mm; speed of the first guide roller is 2855m / min; speed of the second guide roller is 2860m / min; pre-network pressure is 0.08MPa; winding speed is 2840m / min.

[0110] The final polyester fine denier porous fiber has the following specifications: 580 dtex / 576f, breaking strength of 2.52 cN / dtex, breaking strength CV value of 2.6%, breaking elongation of 125.6%, breaking elongation CV value of 2.68%, yarn unevenness of 1.24%, number of breaks of 1.8 times / 18 positions·24 hours, thermal stress center value of 250 cN, and thermal stress deviation of 6 cN.

[0111] Comparative Example 8

[0112] A method for producing veneers of fine denier porous polyester fiber differs from Example 3 only in that the length of the first ring blower is 14cm.

[0113] The final polyester fine denier porous fiber had a yarn unevenness of 1.76% and a breakage rate of 8.4 times / 18 positions·24 hours.

[0114] Compared with Example 3, Comparative Example 8 showed a significant increase in the evenness and number of breaks of polyester fine denier porous fibers. This is because the excessive length of the first ring blower in Comparative Example 8 amplifies the window effect of the wind pressure parameters, resulting in a longer time for the fibers to be disturbed by the lateral force of the cooling wind, which intensifies the fiber vibration and leads to an increase in the evenness and number of breaks.

[0115] Comparative Example 9

[0116] A method for producing veneers of fine denier porous polyester fiber differs from Example 3 only in that the length of the second ring blower is 6 cm.

[0117] The final polyester fine denier porous fiber had a yarn unevenness of 1.85%, a breakage rate of 9.5 times / 18 positions·24 hours, and a thermal stress deviation of 21.4 cN.

[0118] Compared with Example 3, Comparative Example 9 showed a significant increase in the evenness, number of breaks, and thermal stress deviation of polyester fine denier porous fibers. This is because the length of the second ring blower in Comparative Example 9 was too small, resulting in a short cooling air action distance and an increased proportion of residual melt in the fiber core layer, which in turn increased the fiber evenness and thermal stress deviation. At the same time, the short length of the second ring blower caused the polyester fine denier porous fibers to enter the side blowing cooling prematurely. The side blowing cooling was relatively intense, causing the unshaped fibers to shake more, which increased the number of breaks.

[0119] Comparative Example 10

[0120] A method for producing veneers of fine denier porous polyester fiber differs from Example 3 only in that the total length of the first ring blower, the second ring blower, and the side-blowing mesh is 75cm.

[0121] The final polyester fine denier porous fiber had a yarn unevenness of 2.1%, a breakage rate of 12.8 times / 18 positions·24 hours, and a thermal stress deviation of 27.0 cN.

[0122] Compared with Example 3, Comparative Example 10 showed a significant increase in the evenness, number of breaks, and thermal stress deviation of polyester fine denier porous fibers. This is because the excessive total length of the first ring blower, the second ring blower, and the side blower in Comparative Example 10 amplifies the window effect of the wind speed parameter. Furthermore, the excessively long cooling length, which is close to the bundle gathering position of the fiber bundle, leads to increased spinning tension, resulting in increased evenness, number of breaks, and thermal stress deviation.

[0123] Comparative Example 11

[0124] A method for producing veneers of fine denier porous polyester fibers differs from Example 3 only in that the ring blowing pressure is 38 Pa during the second stage of ring blowing cooling.

[0125] The final polyester fine denier porous fiber had a yarn unevenness of 1.68% and a breakage rate of 6.7 times / 18 positions·24 hours.

[0126] Compared with Example 3, the unevenness and number of breaks of polyester fine denier porous fiber were significantly increased in Comparative Example 11. This is because the ring blowing pressure during the second stage of ring blowing cooling in Comparative Example 11 was too high, which caused adjacent monofilaments to vibrate at the same frequency, resulting in an increased probability of yarn bundling, and thus an increased unevenness and number of breaks.

[0127] Example 4

[0128] A method for producing veneers from fine denier porous polyester fibers, comprising the following specific steps:

[0129] (1) Synthesis of polyester melt;

[0130] The overall process flow is as follows: slurry preparation → first esterification → second esterification → pre-polymerization → final polymerization → polyester melt;

[0131] Relevant process parameters: slurry temperature is 75℃, slurry level is 90%, and the mass of PTA in the slurry accounts for 71% of the total mass of PTA and EG; the temperature of the first esterification is 270℃ and the pressure is 110KPa; the temperature of the second esterification is 275℃ and the pressure is 40KPa; the upper chamber temperature of the pre-polymerization is 280℃, the lower chamber temperature is 278℃, the upper chamber pressure is 15KPa, and the lower chamber pressure is 2.2KPa; the final polycondensation pressure is 300Pa, the inlet temperature of the final polycondensation is 281℃, the middle temperature is 285℃, and the outlet temperature is 287℃.

[0132] The intrinsic viscosity of the synthesized polyester melt is 0.628 dL / g;

[0133] (2) Spinning;

[0134] The overall process flow is as follows: spinning assembly spinning → first stage ring air cooling → second stage ring air cooling → side air cooling → spinning oiling → first guide roller → pre-networking → second guide roller → winding and forming;

[0135] The dimensional parameters of the spinneret in the spinning assembly are as follows: the diameter of the spinneret is 120 mm, the diameter of the spinneret orifice is 0.14 mm, and the length of the spinneret orifice is 0.51 mm.

[0136] The first-stage annular air cooling, the second-stage annular air cooling, and the side-blowing air cooling all employ the device for cooling the filament bundle as described above. The first-stage annular air cooling uses a first-ring air blower, the second-stage annular air cooling uses a second-ring air blower, and the side-blowing air cooling uses a side-blowing mesh plate. The relevant parameters of the device for cooling the filament bundle are as follows: the length of the first-ring air blower is 11cm, the length of the second-ring air blower is 10cm, the total length of the first-ring air blower, the second-ring air blower, and the side-blowing mesh plate is 69cm, the mesh aperture of the first-ring air blower is 0.112mm, the mesh aperture of the second-ring air blower is 0.224mm, and the thermal conductivity of the C-shaped plate is 330W / m·K. The temperature of the circulating cooling water transported by the circulating cooling water pipeline is 23℃, and the flow rate is 0.09L / min.

[0137] Relevant process parameters: spinning box temperature is 289℃; length of the windless zone is 60mm; cooling air temperature is 20.5℃; relative humidity of the cooling air is 82%; during the first stage of ring-blown cooling, the ring-blown air pressure is 28Pa; during the second stage of ring-blown cooling, the ring-blown air pressure is 33Pa; during side-blown cooling, the side-blown air velocity is 0.69m / s; bundling height is 950mm; speed of the first guide roller is 2685m / min; speed of the second guide roller is 2690m / min; pre-network pressure is 0.09MPa; winding speed is 2680m / min.

[0138] The final polyester fine denier porous fiber has the following specifications: 368 dtex / 576f, breaking strength of 2.58 cN / dtex, breaking strength CV value of 3.09%, breaking elongation of 124.9%, breaking elongation CV value of 2.81%, yarn unevenness of 1.15%, number of breaks of 2.5 times / 18 positions·24 hours, thermal stress center value of 160 cN, and thermal stress deviation of 4 cN.

[0139] Comparative Example 12

[0140] A method for producing veneers of fine denier porous polyester fibers differs from Example 4 only in that the ring blowing pressure is 30 Pa during the first stage of ring blowing cooling.

[0141] The final polyester fine denier porous fiber had a yarn unevenness of 1.8%, a breakage rate of 8.4 times / 18 positions·24 hours, and a thermal stress deviation of 16.4 cN.

[0142] Compared with Example 4, the unevenness, number of breaks, and thermal stress deviation of polyester fine denier porous fiber were significantly increased in Comparative Example 12. This is because the ring blowing pressure during the first stage of ring blowing cooling in Comparative Example 12 was too high. Due to the large number of fiber pores, the incompletely solidified fiber was impacted by the strong airflow, causing the fiber to vibrate laterally, resulting in filament bundling, fuzzing, and even breakage, which increased the unevenness and number of breaks. At the same time, the excessive ring blowing pressure caused uneven cooling of the inner and outer layers of the fiber, which worsened the uniformity of the forming process, thus increasing the thermal stress deviation.

[0143] Comparative Example 13

[0144] A method for producing veneers of fine denier porous polyester fibers differs from Example 4 only in that the apparatus for cooling the fiber bundle does not have a C-shaped plate.

[0145] The final polyester fine denier porous fiber had a yarn unevenness of 2.37%, a breakage rate of 10.6 times / 18 positions·24 hours, and a thermal stress deviation of 19.2 cN.

[0146] Compared with Example 4, Comparative Example 13 showed a significant increase in the evenness, breakage rate, and thermal stress deviation of the polyester fine denier porous fiber. This is because Comparative Example 13 did not cool the hot air flowing downward from the annular cooling zone, which affects the cooling effect of the side air, at the junction of the annular cooling zone and the side air cooling zone, and did not block its downward movement. Since the polyester fine denier porous fiber has a large number of pores, the temperature inside the second annular air blower is high. When the fiber bundle leaves the second annular air blower, a large amount of hot air with a high temperature will blow vertically downward. At the moment the fiber bundle contacts the side air, the side air will be blocked by the hot air and heated up. This will result in a worse cooling effect on the fiber the further away from the side air outlet, resulting in poor uniformity in the forming process and thus an increase in thermal stress deviation. In addition, due to the large difference between hot and cold airflow, it is easy to cause monofilament disorder, leading to an increase in evenness and breakage rate.

Claims

1. A method for producing a single sheet of polyester fine denier porous fiber, comprising a spinning process by a spinning assembly and a cooling process, characterized in that, The first-stage ring blowing cooling, the second-stage ring blowing cooling and the side blowing cooling are sequentially performed during the cooling; During the first-stage ring blowing cooling, the ring blowing pressure is 25-28 Pa, and the length of the first ring blowing cylinder is 10-12 cm; During the second-stage ring blowing cooling, the ring blowing pressure is 32-35 Pa, and the length of the second ring blowing cylinder is 8-14 cm; The total length of the first ring blowing cylinder, the second ring blowing cylinder and the side blowing net plate is 66-73 cm, and the side blowing speed is 0.60-0.70 m / s; At the junction of the ring blowing cooling zone and the side blowing cooling zone, the hot air flowing downward from the ring blowing cooling zone and affecting the side blowing cooling effect is cooled and blocked from moving downward, and the implementation is as follows: A C-shaped plate is installed at the lower end of the second ring blowing cylinder, the C-shaped plate is made of alloy, has a heat conductivity coefficient of 300-350 W / m·K, is hollow inside and is in communication with a circulating cooling water conveying pipeline; the lower end surface of the second ring blowing cylinder is parallel to the horizontal plane, and the included angle between the C-shaped plate and the horizontal plane is 30°; The area between the filaments and the second ring blowing cylinder is an annular area, which is composed of a first half-annular area and a second half-annular area, the symmetry axes of the two areas are parallel to the side blowing net plate, the second half-annular area is close to the side blowing net plate, and the second half-annular area is completely overlapped with the orthographic projection of the C-shaped plate; The specification of the polyester fine denier porous fiber is 368-580 dtex / 548-576 f; The cooling air temperature is 20-22 ℃.

2. The method according to claim 1, wherein the method is characterized by, The first ring blowing cylinder and the second ring blowing cylinder are two sections of the same ring blowing cylinder, the inner diameters of the first ring blowing cylinder and the second ring blowing cylinder are the same, the mesh hole diameter of the first ring blowing cylinder is 0.110-0.114 mm, and the mesh hole diameter of the second ring blowing cylinder is 0.220-0.228 mm.

3. The method according to claim 1, wherein the method is characterized by, The second ring blowing cylinder is installed on a cylinder frame, the bottom of the wind box is provided with a hinge, the shaft of the hinge is horizontally arranged and parallel to the side blowing net plate, one leaf of the hinge is fixedly connected with the bottom of the wind box, and the other leaf of the hinge is fixedly connected with the position closest to the side blowing net plate of the C-shaped plate and connected with the bottom of the wind box through a magnetic attraction device.

4. The method according to claim 1, wherein the method is characterized by, The circulating cooling water conveyed by the circulating cooling water conveying pipeline has a temperature of 23-25 ℃ and a flow rate of 0.08-0.1 L / min.

5. The method according to claim 1, wherein the method is characterized by, The overall process flow is as follows: spinning of the spinning assembly -> cooling -> spinning oiling -> first godet -> pre-networking -> second godet -> winding forming.

6. The method according to claim 5, wherein the method is characterized by, The diameter of the spinneret is 120 mm, the diameter of the spinneret hole is 0.14-0.16 mm, the length of the spinneret hole is 0.50-0.52 mm, the temperature of the spinning beam is 287-289 ℃, the length of the windless zone is 50-60 mm, the relative humidity of the cooling air is 75-85%, the bundling height is 850-950 mm, the speed of the first godet is 2680-2855 m / min, the speed of the second godet is 2685-2860 m / min, the pre-networking pressure is 0.08-0.09 MPa, and the winding speed is 2665-2840 m / min.

7. The method according to claim 5, wherein the method is characterized by, The breaking strength of the polyester fine denier porous fiber is greater than or equal to 2.45 cN / dtex, the breaking strength CV value is less than or equal to 3.09%, the breaking elongation is 124.1-126.9%, the breaking elongation CV value is less than or equal to 2.81%, the slub unevenness is less than or equal to 1.24%, the breakage frequency is less than or equal to 2.5 times / 18 positions*24 hours, and the thermal stress deviation is less than or equal to M*3%; M is a thermal stress central value, and the unit is cN.

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