Process for the production of porous flat polyester fibers for filter materials

Abstract

This invention belongs to the field of polyester fiber technology and discloses a method for preparing porous flat polyester fibers for filter materials. The polyester melt is extruded through spinneret holes on a spinneret and then sequentially cooled, oiled, guided by a guide hook, pre-networked, rolled by a first hot roller, rolled by a second hot roller, and wound to obtain porous flat polyester fibers for filter materials. The spinneret has 288-384 spinneret holes. The pre-networking device includes two nozzles arranged vertically. The upper nozzle sprays air downwards at an angle, while the lower nozzle sprays air upwards at an angle, with a spray pressure of 0.05-0.06 MPa. This invention ensures that the oil can fully penetrate the porous flat fiber, improving the fiber's lubricity and antistatic properties, while avoiding the direct impact of excessive airflow pressure on the front end of the irregularly shaped fiber, thus preventing fuzz formation and effectively improving product quality and stability.

Description

Technical Field

[0001] This invention belongs to the field of polyester fiber technology and relates to a method for preparing porous flat polyester fibers for filter materials. Background Technology

[0002] Porous flat polyester fibers, due to their high porosity and uniform distribution, can effectively trap tiny particles (such as PM2.5, bacteria, and pollen), and are therefore widely used as filter materials to meet the stringent requirements for filtration performance in fields such as air purification and water treatment.

[0003] However, when applied to the preparation of filter materials, it is necessary to ensure that the fibers maintain good dispersion uniformity after the subsequent cutting process. To achieve this goal, the main network can be eliminated during the preparation process, but this will lead to poor oil permeability of the porous flat fibers. In addition, flat fibers have a large specific surface area and a larger contact area with the network air, which makes them prone to friction between filaments due to shaking during processing, thus causing quality problems such as fuzzy fibers and loose loops.

[0004] Patent application CN116676682A discloses a method for preparing fine denier recycled polyester fiber. The method improves the permeability of oil agent by setting the main network air pressure at 0.10~0.35MPa (lower than the industry standard of ≥0.38MPa). However, this air pressure will also create network nodes, affecting the dispersion uniformity after the subsequent cutting process.

[0005] Therefore, it is of great significance to study a method for preparing porous flat polyester fibers for filter materials in order to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to solve the problems existing in the prior art and to provide a method for preparing porous flat polyester fibers for filter materials.

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

[0008] A method for preparing porous flat polyester fibers for filter materials, wherein polyester melt is extruded through the spinneret holes on a spinneret and then sequentially cooled, oiled, guided by a guide hook, pre-networked, passed through a first hot roller, a second hot roller, and wound into shape to obtain porous flat polyester fibers for filter materials.

[0009] The spinneret has 288 to 384 spinneret holes;

[0010] The pre-network device used in the pre-network includes two nozzles arranged vertically; the nozzle of the upper nozzle sprays air downward at an angle with a pressure of 0.08~0.09MPa; the nozzle of the lower nozzle sprays air upward at an angle with a pressure of 0.05~0.06MPa.

[0011] The reason for choosing to use two nozzles within the same pre-networker, rather than the conventional dual-networker design, is that porous flat polyester fibers are prone to fuzzing. Firstly, the dual pre-networker design with a single nozzle requires essentially the same air pressure in both pre-networking stages to improve cohesion, reaching 0.08~0.09 MPa. This is equivalent to applying this pressure twice to impact the fiber bundle with airflow, and this airflow is a unidirectional, point-to-point blow towards the flat fiber cross-section, easily causing fuzzing. Secondly, each pre-networker has a U-shaped ceramic element at the front and rear (the vertical angle between the U-shaped ceramic element and the fiber bundle is 3~5°, which is existing technology). The purpose is to fix the fiber bundle in the middle of the networker, but the high coefficient of friction between the flat fiber and the U-shaped ceramic element easily leads to fuzzing, especially with two pre-networkers, which further increases the number of fuzz. The asymmetric dual-channel airflow design of this invention, by blowing airflow across the fiber bundle from above and below, achieves surface contact with the flat fiber cross-section, reducing the likelihood of fuzzing. Furthermore, eliminating one set of U-shaped ceramic elements also reduces fuzzing.

[0012] As a preferred technical solution:

[0013] In the method for preparing porous flat polyester fibers for filter materials as described above, the upper nozzle's nozzle orifice is tilted downwards at 30°~45°, and the lower nozzle's nozzle orifice is tilted upwards at 30°~45°. An tilt angle less than 30° corresponds to a smaller angle between the airflow and the direction of the fiber bundle's movement, making it easier for the airflow to reach the surface of the fiber bundle, resulting in poor oil penetration. An tilt angle greater than 45° corresponds to the airflow being nearly perpendicular to the direction of the fiber bundle's movement, resulting in a larger impact force from the airflow hitting the fiber bundle, which can easily cause fuzzing of the flat fibers.

[0014] The method for preparing porous flat polyester fiber for filter material as described above has a pre-network length of 6-8 cm, a nozzle diameter of 2-3 mm, and a distance of 2-3 cm between the upper and lower nozzles.

[0015] The method for preparing porous flat polyester fibers for filter materials as described above specifies that the porous flat polyester fibers for filter materials have a monofilament linear density variation coefficient ≤ 0.5%, a monofilament cross-sectional aspect ratio ≥ 2.7, an aspect ratio variation coefficient (CV) value ≤ 5%, a yarn evenness rate ≤ 1.54%, and a loose loop and fuzzy yarn degradation rate ≤ 1.5%. The low monofilament linear density variation coefficient and aspect ratio unevenness indicate good yarn uniformity; the high monofilament cross-sectional aspect ratio indicates high irregularity.

[0016] The above-described method for preparing porous flat polyester fibers for filter materials has a spinneret with an outer diameter of 88~105mm and an inner diameter of 77~93mm.

[0017] The area on the spinneret with a diameter <40mm is designated as the central zone, the area with a diameter ≥70mm is designated as the external stable zone, and the area between the central zone and the external stable zone is designated as the intermediate transition zone.

[0018] The spacing between any two adjacent spinnerets in the same ring in the central zone is 4.2 mm or more; the spacing between any two adjacent spinnerets in the same ring in the intermediate transition zone is 3.8 to 4.1 mm; and the spacing between any two adjacent spinnerets in the same ring in the outer stable zone is 3.7 to 3.8 mm.

[0019] The diameter of the area without spinnerets in the middle of the spinneret is 26~28mm, and the diameter of the outermost area with spinnerets is 77~93mm, which is the inner diameter of the spinneret.

[0020] In existing small-diameter spinnerets, the area without spinneret holes is generally 18-25mm in diameter (i.e., the spinneret holes are close to the inner ring), and the outer diameter of the spinneret is 76-87mm, with little variation in the distance between the spinneret holes in each ring. The inventors attempted to produce porous flat polyester fibers for filter materials under small-diameter spinnerets. Experiments revealed that significant turbulent vortices exist in the central circular area with a diameter <40mm during production, with wind speed fluctuations exceeding ±0.3m / s, leading to uneven cooling. Simultaneously, the radial oscillation amplitude of the fiber bundle in this area reaches as high as ±5mm after disturbance, easily causing inter-fiber collisions and resulting in a high degree of downgrading of loose and fuzzy fibers.

[0021] To address the aforementioned issues and enable the production of fibers with a high number of pores (288-384 pores) at small plate diameters, this invention improves the arrangement of the spinneret pores. The pore arrangement is changed from a uniform distribution to a gradient density from the inside out, significantly reducing the number of pores in the central region and increasing the pore spacing to over 4.2 mm. The pore spacing in the intermediate transition zone is 3.8-4.1 mm, and the pore spacing in the outer stable zone is 3.7-3.8 mm. This improvement results in two advantages: firstly, fewer inner filament bundles allow for better cooling air penetration; secondly, fewer inner filament bundles lead to lower heat generation, reducing the likelihood of turbulent vortices caused by large temperature differences between the inner and outer sides. Meanwhile, compared to existing technologies, this invention increases the diameter of the central area without spinnerets from 18-25mm to 26-28mm, and the diameter of the outermost ring with spinnerets from 76-87mm to 77-93mm. This provides a larger hole spacing for the spinneret arrangement (i.e., the diameter and circumference of each ring are increased, allowing for a greater number of holes and wider spacing, facilitating the passage of cooling air). Furthermore, the spacing between the rings is also larger, further facilitating the passage of cooling air. This prevents turbulent vortices caused by large temperature differences between the inner and outer sides.

[0022] In the above-described method for preparing porous flat polyester fibers for filter materials, the number of spinneret holes on the spinneret plate is 7 to 8, and the distance between any two adjacent loops is 8 to 10 mm.

[0023] The method for preparing porous flat polyester fibers for filter materials as described above, wherein the rate of reduction of loose loop fibers and fuzzy fibers in the porous flat polyester fibers for filter materials is ≤1%.

[0024] Invention principle:

[0025] The purpose of this invention is to provide a method for preparing porous flat polyester fibers for filter materials. Since it is used in filter materials, good uniformity of dispersion after cutting is required, so a main network is not needed (the main network improves cohesion but affects its dispersion after cutting). However, this would result in poor oil permeability of the porous flat fibers. At the same time, the flat fibers have a large specific surface area, resulting in a larger contact area with the network air, which easily leads to problems such as fuzzing and loose loops caused by friction between monofilaments due to shaking.

[0026] The inventors attempted to compensate for the problems caused by omitting the main network by changing the pre-network air pressure, but failed to achieve the desired effect. This is because flat fibers have a large specific surface area and 288-384 pores, making it difficult for a low pre-network air pressure to overcome the surface tension of the oil and the resistance between multiple filament bundles. This results in the oil forming an uneven oil film on the fiber surface, affecting antistatic properties and rendering the fiber unusable in subsequent processes. On the other hand, if the pre-network air pressure is too high, network nodes will be created. Since the fiber is flat, the conventional pre-network air pressure blows directly onto the filament bundles, which can easily fray the thinnest and most delicate longitudinal section of the flat fiber.

[0027] This invention employs an asymmetric dual-channel airflow design for the pre-network. The upper nozzle sprays air downwards at an angle, while the lower nozzle sprays air upwards at an angle. This cross-flow, opposing airflow towards the filament bundle prevents the formation of network nodes (unified airflow tends to generate periodic vortices, creating network nodes). The main airflow (upper nozzle) acts on the filament bundle at a pressure of 0.08~0.09 MPa. Without creating network nodes, the cross-flow pressure increases the contact area and time between the airflow and the filament bundle, allowing for better penetration of the oiling agent into the porous fibers and improving the oiling agent's permeability. The side airflow (lower nozzle) is reduced to 0.05~0.06 MPa, decreasing direct impact on the front ends of the irregularly shaped fibers and reducing fuzz formation. If the pressures of the main and side airflows are equal, the cross-flow towards the filament bundle will cancel each other out in terms of vertical force, resulting in a "static pressure zone" between the two nozzles, which affects the oiling agent permeability of the porous flat fibers. Therefore, the main airflow is selected at 0.08~0.09MPa, which is related to the downward movement direction of the filament bundle. This allows for the pre-network air pressure to be blown onto the filament bundle on longer filament bundles, thereby improving the permeability of the oil agent. The side airflow is selected at 0.05~0.06MPa, which can reduce fuzz while increasing the interference of the upward airflow and generating filament bundle amplitude.

[0028] This asymmetric dual-channel airflow design, with the main airflow and side airflow working in tandem, ensures that the oil can fully penetrate the porous, flat fibers, improving their lubricity and antistatic properties. It also prevents excessive airflow pressure from directly impacting the shaped fiber tips and causing fuzzing, thus effectively improving product quality and stability. Furthermore, this design meets customer requirements for uniform dispersion of the filter material after cutting, enhancing product performance.

[0029] Beneficial effects:

[0030] (1) The main airflow of the present invention acts on the main body of the filament bundle. Without generating network nodes, the air pressure of the upper and lower crosses blows towards the filament bundle, which increases the contact area and time between the airflow and the filament bundle, allowing the porous filament to better penetrate the oil agent and improve the permeability of the oil agent; while the side airflow is reduced to 0.05~0.06MPa, reducing the direct impact on the front end of the irregular fiber and reducing the generation of fuzz.

[0031] (2) This invention, through its asymmetric dual-channel airflow design, with the main airflow and side airflow working in tandem, ensures that the oil can fully penetrate into the porous flat fibers, improving the fibers' lubricity and antistatic properties. It also avoids the direct impact of excessive airflow pressure on the front end of the irregularly shaped fibers, thus preventing fuzz formation and effectively improving product quality and stability. Furthermore, this design meets customer requirements for uniform dispersion of the filter material after cutting, enhancing the product's performance. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the pre-networker used in this invention;

[0033] Figure 2 This is a schematic diagram of a single network ceramic component in the pre-networker of the present invention; a is a front view of the network ceramic component, b is a bottom view of a single nozzle in a, and c is a side view of a.

[0034] In the diagram, 1-upper nozzle, 2-lower nozzle, 3-upper ceramic piece, 4-lower ceramic piece, 5-filament bundle. Detailed Implementation

[0035] 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.

[0036] To ensure that the performance of the substances used in each embodiment and comparative example is fully disclosed, the manufacturers and brands of the substances are specified. Other products from manufacturers and brands that conform to the limitations of this invention are also feasible.

[0037] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0038] Linear density coefficient of variation (CV): The linear density of the sample to be tested was determined by twisting the yarn in GB / T 14343-2008 "Test Method for Linear Density of Chemical Fiber Filaments". After testing the linear density of the single filament 20 times, the linear density coefficient of variation (CV) was calculated based on the measured data. The calculation formula is: linear density coefficient of variation (CV) = linear density standard deviation / linear density average value.

[0039] Aspect ratio and aspect ratio unevenness: The aspect ratio and aspect ratio unevenness of the test samples were determined in accordance with the standard FZ / T 50002-2013 "Test Method for the Shape of Chemical Fibers". The test procedure was as follows: First, the cross-section of the sample was magnified by a microscope, then the length and width of the sample were calculated, and then the aspect ratio (aspect ratio = length / width) was calculated. A total of 40 aspect ratios were tested, and finally the aspect ratio unevenness was calculated based on the test results (aspect ratio unevenness = aspect ratio standard deviation / aspect ratio average).

[0040] Evenness: The evenness of the sample was tested using a USTER 5 evenness tester in accordance with GB / T 14346-2015 "Test Method for Evenness of Chemical Fiber Filaments - Capacitive Method". The specific procedure was as follows: the sample was first conditioned in an environment with a temperature of 20℃ and a humidity of 65% for 2 hours. Then, the sample was passed through the two plates of a capacitor at a uniform speed. The mass of the sample in each equal interval was converted into an electrical signal. The percentage of the standard deviation of all test electrical signals to the mean value is the evenness CV value. The test speed was 200 m / min and the test time for the sample was 2.5 min.

[0041] Downgrading rate of loose loop yarn and fuzzy yarn: Loose loop yarn is a single filament that is exposed on the end face of the roll in an arc or loop shape and is not broken. Fuzzy yarn is downgraded if there are more than 10 broken single filament defects on the surface of each yarn roll. Downgrading rate of loose loop yarn and fuzzy yarn = (number of loose loop yarn downgraded + number of fuzzy yarn downgraded) × 100% / total number of yarns.

[0042] Example 1

[0043] A method for preparing porous flat polyester fibers for filter materials, the specific process of which is as follows:

[0044] Polyester melt (the polyester raw materials are purified terephthalic acid (PTA) and ethylene glycol (EG), with PTA content of 70 wt%) is extruded through spinneret holes and then sequentially cooled, oiled, and guided by guide hooks, as follows: Figure 1 As shown, the fiber bundle 5 passes through the upper ceramic part 3, upper nozzle 1, lower nozzle 2, and lower ceramic part 4 of the pre-network, and then passes through the first hot roller, the second hot roller, and is wound to form a porous flat polyester fiber for filter material. The spinning temperature is 290℃, the slow cooler temperature is 311℃, the height of the windless zone is 45mm, the cooling air pressure is 60Pa, the speed of the first hot roller is 1800m / min, the temperature of the first hot roller is 92℃, the speed of the second hot roller is 3835m / min, the temperature of the second hot roller is 160℃, and the winding speed is 3800m / min.

[0045] The outer diameter of the spinneret is 88mm and the inner diameter is 77mm.

[0046] The spinneret has 288 spinneret holes, which are flat in shape, 0.6 mm long, 0.06 mm wide, and 0.4 mm deep.

[0047] The area on the spinneret with a diameter <40mm is designated as the central zone, the area with a diameter ≥70mm is designated as the external stable zone, and the area between the central zone and the external stable zone is designated as the intermediate transition zone.

[0048] The diameter of the area without spinnerets in the center of the spinneret is 26mm;

[0049] The spinneret has 7 loops of spinneret holes, which are numbered from the inside out as the 1st loop, 2nd loop, 3rd loop, 4th loop, 5th loop, 6th loop, and 7th loop.

[0050] The spacing between any two adjacent spinnerets in the first ring is 4.54 mm; the spacing between any two adjacent spinnerets in the second ring is 4.58 mm; the spacing between any two adjacent spinnerets in the third ring is 4.02 mm; the spacing between any two adjacent spinnerets in the fourth ring is 3.89 mm; the spacing between any two adjacent spinnerets in the fifth ring is 3.80 mm; the spacing between any two adjacent spinnerets in the sixth ring is 3.87 mm; and the spacing between any two adjacent spinnerets in the seventh ring is 3.78 mm.

[0051] The spacing between the first and second circles is 9mm, the spacing between the second and third circles is 8.5mm, the spacing between the third and fourth circles is 8.5mm, the spacing between the fourth and fifth circles is 8.5mm, the spacing between the fifth and sixth circles is 8.5mm, and the spacing between the sixth and seventh circles is 8mm.

[0052] like Figure 1 , Figure 2 As shown, the pre-network device used in the above pre-network includes two nozzles arranged vertically.

[0053] The nozzle 1 at the top is tilted 30° downwards and sprays air at a pressure of 0.08 MPa; the nozzle 2 at the bottom is tilted 30° upwards and sprays air at a pressure of 0.05 MPa.

[0054] The pre-network device is 6cm long, the nozzle diameter is 2mm, and the distance between the upper and lower nozzles is 2cm.

[0055] The filter material uses porous flat polyester fiber with a single filament linear density variation coefficient (CV) of 0.28%, a single filament cross-section aspect ratio of 2.7, an aspect ratio unevenness of 3.41%, a yarn unevenness of 1.03%, and a loose loop and fuzzy fiber degradation rate of 0.85%.

[0056] Comparative Example 1

[0057] A method for preparing porous flat polyester fiber for filter material is basically the same as in Example 1, except that the pressure of the air jet from the lower nozzle is adjusted to the pressure of the air jet from the upper nozzle, i.e., 0.08 MPa.

[0058] The final filter material was made with a 1.67% downgrade rate of loose loops and filaments of porous flat polyester fiber.

[0059] Comparing Comparative Example 1 and Example 1, it can be seen that the filter material prepared in this comparative example has an increased rate of downgrading of porous flat polyester fiber loose loop filaments and fuzzy filaments. This is because the air pressure of the main airflow and the side airflow are equal. Since the airflow is blown towards the filament bundle from top to bottom, the airflow will cancel out the vertical force with the filament bundle, resulting in a "static pressure zone" in the filament bundle between the two nozzles. This affects the oil permeability of the porous flat fiber, thus causing an increase in the downgrading rate of loose loop filaments. At the same time, since the side airflow is larger and blows upward towards the filament bundle, while the filament bundle moves downward, it is easy to blow the flat filaments into fuzz, resulting in an increase in the downgrading rate of fuzzy filaments.

[0060] Comparative Example 2

[0061] A method for preparing porous flat polyester fibers for filter materials is basically the same as in Example 1, except that the nozzles of the upper and lower nozzles are not tilted, but are set perpendicular to the fiber bundle.

[0062] The final filter material was made with a 1.71% downgrade rate of loose loops and filaments of porous flat polyester fiber.

[0063] Comparing Comparative Example 2 and Example 1, it can be seen that the filter material prepared in this comparative example has a higher rate of degradation of porous flat polyester fiber loose loop filaments and fuzzy filaments. This is because the filament bundle has a flat cross-section and a large specific surface area. If the pre-network air is blown vertically towards the filament bundle, the problem of fuzzy filaments and loose loop filaments caused by friction between the single filaments due to shaking is likely to occur.

[0064] Example 2

[0065] A method for preparing porous flat polyester fibers for filter materials, the specific process of which is as follows:

[0066] Polyester melt (the polyester raw materials are purified terephthalic acid (PTA) and ethylene glycol (EG), wherein the PTA content is 70.5 wt%) is extruded through the spinneret holes on the spinneret and then sequentially cooled, oiled, guided by the guide hook, pre-networked, rolled by the first hot roller, rolled by the second hot roller, and wound to form porous flat polyester fibers for filter materials; wherein the spinning temperature is 290℃, the slow cooler temperature is 312℃, the height of the windless zone is 45mm, the cooling air pressure is 65Pa, the speed of the first hot roller is 1790m / min, the temperature of the first hot roller is 94℃, the speed of the second hot roller is 3825m / min, the temperature of the second hot roller is 163℃, and the winding speed is 3790m / min;

[0067] The outer diameter of the spinneret is 95mm and the inner diameter is 84mm.

[0068] The spinneret has 306 spinneret holes, which are flat in shape, 0.6 mm long, 0.07 mm wide, and 0.4 mm deep.

[0069] The area on the spinneret with a diameter <40mm is designated as the central zone, the area with a diameter ≥70mm is designated as the external stable zone, and the area between the central zone and the external stable zone is designated as the intermediate transition zone.

[0070] The diameter of the area without spinnerets in the center of the spinneret is 27mm;

[0071] The spinneret has 7 loops of spinneret holes, which are numbered from the inside out as the 1st loop, 2nd loop, 3rd loop, 4th loop, 5th loop, 6th loop, and 7th loop.

[0072] The spacing between any two adjacent spinnerets in the first ring is 5.30 mm; the spacing between any two adjacent spinnerets in the second ring is 4.78 mm; the spacing between any two adjacent spinnerets in the third ring is 4.06 mm; the spacing between any two adjacent spinnerets in the fourth ring is 3.79 mm; the spacing between any two adjacent spinnerets in the fifth ring is 3.93 mm; the spacing between any two adjacent spinnerets in the sixth ring is 3.80 mm; and the spacing between any two adjacent spinnerets in the seventh ring is 3.77 mm.

[0073] The spacing between the first and second circles is 9.5mm, the spacing between the second and third circles is 10mm, the spacing between the third and fourth circles is 9mm, the spacing between the fourth and fifth circles is 9.5mm, the spacing between the fifth and sixth circles is 10mm, and the spacing between the sixth and seventh circles is 9mm.

[0074] The pre-network device used in the above pre-network consists of two nozzles arranged vertically.

[0075] The upper nozzle has its nozzle orifice tilted at 40° downwards, and the jet pressure is 0.09 MPa; the lower nozzle has its nozzle orifice tilted at 40° upwards, and the jet pressure is 0.06 MPa.

[0076] The pre-network device is 7cm long, the nozzle diameter is 3mm, and the distance between the upper and lower nozzles is 3cm.

[0077] The filter material uses porous flat polyester fiber with a single filament linear density variation coefficient (CV) of 0.31%, a single filament cross-section aspect ratio of 2.8, an aspect ratio unevenness of 2.89%, a yarn unevenness of 0.97%, and a loose loop and fuzzy fiber degradation rate of 0.89%.

[0078] Example 3

[0079] A method for preparing porous flat polyester fibers for filter materials, the specific process of which is as follows:

[0080] Polyester melt (the polyester raw materials are purified terephthalic acid (PTA) and ethylene glycol (EG), wherein the PTA content is 71 wt%) is extruded through the spinneret holes on the spinneret and then sequentially cooled, oiled, guided by the guide hook, pre-networked, rolled by the first hot roller, rolled by the second hot roller, and wound to obtain porous flat polyester fiber for filter material; wherein the spinning temperature is 292℃, the slow cooler temperature is 313℃, the height of the windless zone is 45mm, the cooling air pressure is 70Pa, the speed of the first hot roller is 1780m / min, the temperature of the first hot roller is 95℃, the speed of the second hot roller is 3815m / min, the temperature of the second hot roller is 165℃, and the winding speed is 3780m / min;

[0081] The outer diameter of the spinneret is 105 mm and the inner diameter is 93 mm.

[0082] The spinneret has 384 spinneret holes, which are flat in shape, 0.5 mm long, 0.06 mm wide, and 0.45 mm deep.

[0083] The area on the spinneret with a diameter <40mm is designated as the central zone, the area with a diameter ≥70mm is designated as the external stable zone, and the area between the central zone and the external stable zone is designated as the intermediate transition zone.

[0084] The diameter of the area without spinnerets in the center of the spinneret is 28mm;

[0085] The spinneret has 8 loops of spinneret holes, which are numbered from the inside out as the 1st loop, 2nd loop, 3rd loop, 4th loop, 5th loop, 6th loop, 7th loop, and 8th loop.

[0086] The spacing between any two adjacent spinnerets in the first ring is 6.28 mm; the spacing between any two adjacent spinnerets in the second ring is 4.91 mm; the spacing between any two adjacent spinnerets in the third ring is 4.10 mm; the spacing between any two adjacent spinnerets in the fourth ring is 3.86 mm; the spacing between any two adjacent spinnerets in the fifth ring is 3.84 mm; the spacing between any two adjacent spinnerets in the sixth ring is 3.80 mm; the spacing between any two adjacent spinnerets in the seventh ring is 3.77 mm; and the spacing between any two adjacent spinnerets in the eighth ring is 3.75 mm.

[0087] The spacing between the first and second circles is 9.5mm, the spacing between the second and third circles is 9.5mm, the spacing between the third and fourth circles is 9.5mm, the spacing between the fourth and fifth circles is 9.5mm, the spacing between the fifth and sixth circles is 9mm, the spacing between the sixth and seventh circles is 9mm, and the spacing between the seventh and eighth circles is 9mm.

[0088] The pre-network device used in the above pre-network consists of two nozzles arranged vertically.

[0089] The upper nozzle has its nozzle orifice tilted at 45° downwards, and the jet pressure is 0.09 MPa; the lower nozzle has its nozzle orifice tilted at 45° upwards, and the jet pressure is 0.06 MPa.

[0090] The pre-network device is 8cm long, the nozzle diameter is 3mm, and the distance between the upper and lower nozzles is 3cm.

[0091] The filter material uses porous flat polyester fiber with a single filament linear density variation coefficient (CV) of 0.27%, a single filament cross-section aspect ratio of 2.7, an aspect ratio unevenness of 3.16%, a yarn unevenness of 1.12%, and a loose loop and fuzzy fiber degradation rate of 0.93%.

[0092] Example 4

[0093] A method for preparing porous flat polyester fibers for filter materials, the specific process of which is as follows:

[0094] Polyester melt (the polyester raw materials are purified terephthalic acid (PTA) and ethylene glycol (EG), wherein the PTA content is 72wt%) is extruded through the spinneret holes on the spinneret and then sequentially cooled, oiled, guided by the guide hook, pre-networked, rolled by the first hot roller, rolled by the second hot roller, and wound to form porous flat polyester fibers for filter materials; wherein the spinning temperature is 290℃, the slow cooler temperature is 311℃, the height of the windless zone is 45mm, the cooling air pressure is 60Pa, the speed of the first hot roller is 1800m / min, the temperature of the first hot roller is 92℃, the speed of the second hot roller is 3835m / min, the temperature of the second hot roller is 160℃, and the winding speed is 3800m / min;

[0095] The outer diameter of the spinneret is 88mm and the inner diameter is 77mm.

[0096] The spinneret has 288 spinneret holes, which are flat in shape, 0.7 mm long, 0.06 mm wide, and 0.4 mm deep.

[0097] The area on the spinneret with a diameter <40mm is designated as the central zone, the area with a diameter ≥70mm is designated as the external stable zone, and the area between the central zone and the external stable zone is designated as the intermediate transition zone.

[0098] The diameter of the area without spinnerets in the center of the spinneret is 26mm;

[0099] The spinneret has 7 loops of spinneret holes, which are numbered from the inside out as the 1st loop, 2nd loop, 3rd loop, 4th loop, 5th loop, 6th loop, and 7th loop.

[0100] The spacing between any two adjacent spinnerets in the first ring is 4.54 mm; the spacing between any two adjacent spinnerets in the second ring is 4.58 mm; the spacing between any two adjacent spinnerets in the third ring is 4.02 mm; the spacing between any two adjacent spinnerets in the fourth ring is 3.89 mm; the spacing between any two adjacent spinnerets in the fifth ring is 3.80 mm; the spacing between any two adjacent spinnerets in the sixth ring is 3.87 mm; and the spacing between any two adjacent spinnerets in the seventh ring is 3.78 mm.

[0101] The spacing between the first and second circles is 9mm, the spacing between the second and third circles is 8.5mm, the spacing between the third and fourth circles is 8.5mm, the spacing between the fourth and fifth circles is 8.5mm, the spacing between the fifth and sixth circles is 8.5mm, and the spacing between the sixth and seventh circles is 8mm.

[0102] The pre-network device used in the above pre-network consists of two nozzles arranged vertically.

[0103] The upper nozzle has its nozzle orifice tilted 40° downwards to spray air at a pressure of 0.08 MPa; the lower nozzle has its nozzle orifice tilted 40° upwards to spray air at a pressure of 0.05 MPa.

[0104] The pre-network device is 7cm long, the nozzle diameter is 2mm, and the distance between the upper and lower nozzles is 2cm.

[0105] The filter material uses porous flat polyester fiber with a single filament linear density variation coefficient (CV) of 0.21%, a single filament cross-section aspect ratio of 3.1, an aspect ratio unevenness of 2.89%, a yarn unevenness of 1.08%, and a loose loop and fuzzy fiber degradation rate of 0.94%.

[0106] Example 5

[0107] A method for preparing porous flat polyester fibers for filter materials, the specific process of which is as follows:

[0108] Polyester melt (the polyester raw materials are purified terephthalic acid (PTA) and ethylene glycol (EG), wherein the PTA content is 71.5 wt%) is extruded through the spinneret holes on the spinneret and then sequentially cooled, oiled, guided by the guide hook, pre-networked, rolled by the first hot roller, rolled by the second hot roller, and wound to form porous flat polyester fibers for filter materials; wherein the spinning temperature is 290℃, the slow cooler temperature is 311℃, the height of the windless zone is 45mm, the cooling air pressure is 60Pa, the speed of the first hot roller is 1800m / min, the temperature of the first hot roller is 92℃, the speed of the second hot roller is 3835m / min, the temperature of the second hot roller is 160℃, and the winding speed is 3800m / min;

[0109] The outer diameter of the spinneret is 88mm and the inner diameter is 77mm.

[0110] The spinneret has 288 spinneret holes, which are flat in shape, 0.5 mm long, 0.06 mm wide, and 0.4 mm deep.

[0111] The diameter of the area without spinnerets in the center of the spinneret is 26mm;

[0112] The spinneret has 7 loops of spinneret holes, which are numbered from the inside out as the 1st loop, 2nd loop, 3rd loop, 4th loop, 5th loop, 6th loop, and 7th loop.

[0113] The spacing between any two adjacent spinnerets in the first ring is 4 mm; the spacing between any two adjacent spinnerets in the second ring is 4 mm; the spacing between any two adjacent spinnerets in the third ring is 3.75 mm; the spacing between any two adjacent spinnerets in the fourth ring is 3.75 mm; the spacing between any two adjacent spinnerets in the fifth ring is 3.75 mm; the spacing between any two adjacent spinnerets in the sixth ring is 3.8 mm; and the spacing between any two adjacent spinnerets in the seventh ring is 3.8 mm.

[0114] The spacing between the first and second circles is 7.6mm, the spacing between the second and third circles is 10mm, the spacing between the third and fourth circles is 9.6mm, the spacing between the fourth and fifth circles is 9.6mm, the spacing between the fifth and sixth circles is 8mm, and the spacing between the sixth and seventh circles is 9.7mm.

[0115] The pre-network device used in the above pre-network consists of two nozzles arranged vertically.

[0116] The upper nozzle has its nozzle orifice tilted at 35° downwards, and the jet pressure is 0.08 MPa; the lower nozzle has its nozzle orifice tilted at 35° upwards, and the jet pressure is 0.05 MPa.

[0117] The pre-network device is 7cm long, the nozzle diameter is 2mm, and the distance between the upper and lower nozzles is 2cm.

[0118] The filter material uses porous flat polyester fiber with a single filament linear density variation coefficient (CV) of 0.38%, a single filament cross-section aspect ratio of 2.8, an aspect ratio unevenness of 2.89%, a yarn unevenness of 1.54%, and a loose loop and fuzzy fiber degradation rate of 1.38%.

[0119] Example 6

[0120] A method for preparing porous flat polyester fibers for filter materials, the specific process of which is as follows:

[0121] Polyester melt (the polyester raw materials are purified terephthalic acid (PTA) and ethylene glycol (EG), wherein the PTA content is 70.5 wt%) is extruded through the spinneret holes on the spinneret and then sequentially cooled, oiled, guided by the guide hook, pre-networked, rolled by the first hot roller, rolled by the second hot roller, and wound to form porous flat polyester fibers for filter materials; wherein the spinning temperature is 292℃, the slow cooler temperature is 313℃, the height of the windless zone is 45mm, the cooling air pressure is 70Pa, the speed of the first hot roller is 1780m / min, the temperature of the first hot roller is 95℃, the speed of the second hot roller is 3815m / min, the temperature of the second hot roller is 165℃, and the winding speed is 3780m / min;

[0122] The outer diameter of the spinneret is 105 mm and the inner diameter is 93 mm.

[0123] The spinneret has 384 spinneret holes, which are flat in shape, 0.5 mm long, 0.06 mm wide, and 0.45 mm deep.

[0124] The diameter of the area without spinnerets in the center of the spinneret is 28mm;

[0125] The spinneret has 8 loops of spinneret holes, which are numbered from the inside out as the 1st loop, 2nd loop, 3rd loop, 4th loop, 5th loop, 6th loop, 7th loop, and 8th loop.

[0126] The spacing between any two adjacent spinnerets in the first ring is 4.5 mm; the spacing between any two adjacent spinnerets in the second ring is 4.5 mm; the spacing between any two adjacent spinnerets in the third ring is 4.05 mm; the spacing between any two adjacent spinnerets in the fourth ring is 4.05 mm; the spacing between any two adjacent spinnerets in the fifth ring is 4.05 mm; the spacing between any two adjacent spinnerets in the sixth ring is 4 mm; the spacing between any two adjacent spinnerets in the seventh ring is 4 mm; and the spacing between any two adjacent spinnerets in the eighth ring is 3.9 mm.

[0127] The spacing between the first and second circles is 14.3mm, the spacing between the second and third circles is 12mm, the spacing between the third and fourth circles is 12.9mm, the spacing between the fourth and fifth circles is 10.3mm, the spacing between the fifth and sixth circles is 9.3mm, the spacing between the sixth and seventh circles is 10.2mm, and the spacing between the seventh and eighth circles is 7.7mm.

[0128] The pre-network device used in the above pre-network consists of two nozzles arranged vertically.

[0129] The upper nozzle has its nozzle orifice tilted at 40° downwards, and the jet pressure is 0.09 MPa; the lower nozzle has its nozzle orifice tilted at 40° upwards, and the jet pressure is 0.06 MPa.

[0130] The pre-network device is 8cm long, the nozzle diameter is 3mm, and the distance between the upper and lower nozzles is 3cm.

[0131] The filter material uses porous flat polyester fiber with a single filament linear density variation coefficient (CV) of 0.46%, a single filament cross-section aspect ratio of 2.8, an aspect ratio unevenness of 3.43%, a yarn unevenness of 1.38%, and a loose loop and fuzzy fiber degradation rate of 1.47%.

Claims

1. A method for preparing porous flat polyester fibers for filter materials, characterized in that: After the polyester melt is extruded through the spinneret holes on the spinneret, it is sequentially cooled, oiled, guided by the guide hook, pre-networked, passed through the first hot roller, the second hot roller, and wound to form porous flat polyester fibers for filter materials. The spinneret has 288 to 384 spinneret holes; The pre-network device used in the pre-network includes two nozzles arranged vertically; the nozzle of the upper nozzle sprays air downward at an angle with a pressure of 0.08~0.09MPa; the nozzle of the lower nozzle sprays air upward at an angle with a pressure of 0.05~0.06MPa.

2. The method for preparing porous flat polyester fibers for filter materials according to claim 1, characterized in that, The nozzle at the top is tilted 30°~45° downwards to spray air, while the nozzle at the bottom is tilted 30°~45° upwards to spray air.

3. The method for preparing porous flat polyester fibers for filter materials according to claim 1, characterized in that, The pre-net device is 6-8cm long, the nozzle diameter is 2-3mm, and the distance between the upper and lower nozzles is 2-3cm.

4. A method for preparing porous flat polyester fibers for filter materials according to any one of claims 1 to 3, characterized in that, The filter material uses porous flat polyester fibers with a linear density variation coefficient of ≤0.5%, a cross-sectional aspect ratio of ≥2.7, a cross-sectional aspect ratio variation coefficient (CV) value of ≤5%, a yarn unevenness rate of ≤1.54%, and a rate of degradation of loose loop yarns and fuzzy yarns of ≤1.5%.

5. The method for preparing porous flat polyester fibers for filter materials according to claim 1, characterized in that, The outer diameter of the spinneret is 88~105mm, and the inner diameter is 77~93mm; The area on the spinneret with a diameter <40mm is designated as the central zone, the area with a diameter ≥70mm is designated as the external stable zone, and the area between the central zone and the external stable zone is designated as the intermediate transition zone. The spacing between any two adjacent spinnerets in the same ring in the central zone is 4.2 mm or more; the spacing between any two adjacent spinnerets in the same ring in the intermediate transition zone is 3.8 to 4.1 mm; and the spacing between any two adjacent spinnerets in the same ring in the outer stable zone is 3.7 to 3.8 mm. The diameter of the area without spinneret holes in the middle of the spinneret is 26~28mm.

6. The method for preparing porous flat polyester fibers for filter materials according to claim 5, characterized in that, The spinneret has 7 to 8 spinneret holes, and the spacing between any two adjacent spinnerets is 8 to 10 mm.

7. The method for preparing porous flat polyester fibers for filter materials according to claim 6, characterized in that, The filter material uses loose loop and wool fibers of porous flat polyester fiber with a degradation rate of ≤1%.

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