The causes and countermeasures of polyester filament wool
1. The production of wool during the FDY production process of ordinary polyester filament
The polyester melt flows into the spinning box through the action of the booster pump, and then After spinning, cooling, oiling, stretching, shaping and other processes, the resulting product is fully drawn yarn FDY with a uniform sheath-core structure. When the spinning speed and cooling rate are very high, due to stress concentration, the cortex is subjected to greater tension, and the fiber cortex is prone to cracks, leading to lint. Therefore, it is very important to choose excellent cooling conditions to maintain a uniform radial structure. . The successful approach is to establish an effective slow cooling zone and use a side blowing device with a honeycomb shape, which can generate advection wind and achieve good cooling of the thin melt flow.
During the stretching process, as the processing speed (i.e. the second hot roller speed) increases, the output increases proportionally, the production cost decreases, and the dyeing uniformity improves. . However, when the processing speed is too high, product breakage and lint will increase, so a balance must be made to determine the appropriate processing speed. If the tension is low due to insufficient stretching, the shaking amplitude of the filament will increase, which will also cause filament and breakage. However, too high tension will have a negative effect on the formation and unwinding of the filament cake.
From the perspective of the relationship between the adhesion of oil and fiber fluff, maintaining a higher concentration of oil emulsion and silk oil content can reduce fiber fuzz. However, it is also necessary to prevent the oil concentration from being too high, which will lead to a decrease in oil permeability and a decrease in silk quality. The FDY oiling method can choose oiling by the oil nozzle or oiling by the tanker. Using a nozzle for oiling can effectively reduce the spinning tension, but the uniformity of oiling is not good, resulting in large tension fluctuations in the yarn during the stretching process and many dye spots on the product. Oil tanker is used for oiling. Although the oiling is uniform and the dyeing uniformity is good, the spinning tension is high, which increases the wool and breakage rates, increases consumption, and decreases the full roll rate. To this end, the oil tanker can be used for oiling, and the spinning tension can be effectively reduced by adjusting the oil tanker speed and the wrapping angle between the filament and the tanker, thereby reducing the occurrence of filaments and broken ends.
2. The generation of wool during the production process of special-shaped polyester filament FDY
In order to give the fiber excellent sparkle, feel and pilling resistance, and to give the fabric a unique style and excellent performance, it is often necessary to produce a type of special-shaped polyester filament in industry. However, special-shaped polyester filaments are often found in practice. Filaments and broken ends are common during filament production, and the design of the spinneret is a key component in manufacturing special-shaped fibers. For example, when using a rectangular hole-shaped spinneret to produce flat filaments, due to the uneven normal stress of the melt flowing through the hole wall, the extrusion expansion of the melt is also uneven, causing the fiber to become unstable during spinning and drawing. It is easy to produce a lot of hair and broken ends during the stretching process. The spinneret with dumbbell-shaped holes can effectively reduce the unevenness of melt extrusion expansion and effectively improve the degree of irregularity. The production of special-shaped yarn has higher requirements on the drying uniformity and moisture content of the slices than conventional fibers, so theoretically the drying conditions should be strengthened. However, compared with semi-matte slices, the crystallization speed of large glossy slices is significantly lower, and the slices are prone to adhesion. In severe cases, agglomeration will occur at the pre-crystallization feed, making production unable to proceed normally. Therefore, a gentler crystallization method should be used for pre-crystallization. Conditions, appropriately lower the pre-crystallization temperature, extend the residence time of the slices in the pre-crystallization, and make the slices reach a certain degree of crystallization to ensure that the slices do not stick during the drying process.
If the moisture content of dry slices is too high, or the viscosity of dry and wet slices drops too much, it will cause an increase in filament and breakage during the spinning process. The spinning temperature has a great influence on the processing performance of special-shaped yarns. Although lowering the spinning temperature is conducive to the increase of the special-shaped degree, it will increase the puffing effect of the melt spinneret, causing an increase in filament and breakage during the spinning process. It is ideal to choose a suitable spinning temperature such as 293°C, because it can take into account the degree of abnormality and at the same time produce relatively less wool and broken ends. The conditions of cooling forming are key parameters that affect the degree of deformation and the quality of post-stretched products. The faster the cooling, the higher the degree of deformation. However, due to the high degree of irregularity and the sheath-core structure that may be produced by rapid cooling, the fiber is prone to lint and breakage during the stretching process, and the dyeing performance is deteriorated. Therefore, in order to reduce lint and breakage, it is necessary to take into account the abnormal shape. Under the premise of maintaining the temperature, gentle cooling conditions should be adopted as much as possible.
Production and processing methods of polyester filament wool
1. Thermal Degradation of Polyester Melt
Polyester PET has good thermal stability, but is very sensitive to impurities. Pure PET begins to degrade at 250-300°C, but volatile products are not significantly released until above 350°C. The initiation process of degradation includes the heterocleavage of the ester site to generate carboxylic acid and vinyl ester end groups. The latter can undergo a transesterification reaction with the hydroxyethyl ester end group in polyester PET to release acetaldehyde, which is the most important Volatile products. CO is also observed at higher temperatures. Volatile products include CO2, CH4, C2H2, C2H4 and benzene, so the actual reaction is more complicated. The melt delivery pipeline is filled with gas phase heat medium. The gas phase heat medium main pipe distributes the heat medium vapor from the superheater to the jacket of the melt delivery pipeline, entering from the lowest point of each section.
Usually. Depending on the type of spinning production, the temperature of the heat medium vapor in the melt delivery pipeline is 280℃-290℃. The spinning box and the spinning components in it are heated by gas phase heat.Media heated. The heating situation is similar to that of the melt delivery pipe. The usual operating temperature range of the spinning box is 275-285°C. The melt passes from the polyester final polymerization kettle to before forming strands. They are all insulated by heat media. If the heat medium insulation temperature is too high. The longer the residence time of melt transportation is, the more serious the degradation of melt macromolecules will be. When the raw filament is formed by pressurization and extrusion by a metering pump and traction by a traction machine, the raw filament will have defects. It is easy to break and produce lint.
2. Tow cooling process
The ring blowing device is located in the spinning In the pressure air chamber directly below the wire assembly, its main function is to rapidly cool the molten polymer by blowing air into the thin stream of melt. The ring-blowing device evenly distributes the cooling air entering each spinning position to ensure high-quality, uniformly cooled tows. If the tow cooling blower is not clean enough and the air pressure and air volume are set improperly. Merging and breakage will occur. Produce hair. In view of the cooling problem, the built-in steel mesh of the ring blowing must be dust-free. If pollution occurs or the tows in the spinning position are vortexed due to the blowing, the ring blowing tube must be replaced; in order to ensure the normal blowing quality from the system, It is stipulated that the blowing screen of the ring blowing tube must be replaced regularly to ensure that the clean tows are cooled and blown to avoid lint caused by blowing.
3. The filament bundle passes through the wire path process
The melt flows from After the component extrudes the tow, it must go through the oiling roller, guide rod, upper and lower cleaning guides, spinning tunnel, large and small guide rollers, steering rollers, side rollers, tractors, etc. If they are in contact with the surface of the tow If it is not smooth and has defects, it will cause damage to the silk bundles and produce lint. In response to defects in the wire path, it is necessary to intensify the inspection of each roller to find problems, promptly deal with and replace them, and frequently correct the pin gap to reduce friction on the wire bundles, ensure that the wire path is in normal operation, and reduce the generation of filaments.
a. The rollers of the silk path
If the rollers of the silk path are not installed correctly. There are defects or burrs on the surface of the roller. When the filament bundles come into contact with them, the friction increases and filaments are produced.
b. Clean the wire guide up and down
Clean the guide wire up and down The device is composed of two parallel pins with a small gap in the middle, and the filament bundle passes through the two pins. The pin gap can be adjusted in the range of O.5-1.2 mm. Its main function is: once more filaments or defects appear, the filament bundle will be torn or broken. If the gap between the pins is not adjusted properly, the friction between the filament bundle and the filament bundle will increase as it passes, resulting in filaments or even the filament bundle being cut off.
4. Poor working conditions of spinning components
The spinning assembly is the key equipment of the short fiber device. In the production of short fibers, it plays the role of filtering and removing impurities from the melt, mixing and homogenizing the polyester melt, and evenly distributing the melt to every microorganism on the spinneret. L, and extruded from the spinneret to form filament bundles.
a. The component pressure rises abnormally
If the component pressure rises and falls sharply, the original fiber fineness , the breaking strength and elongation will change greatly, and even slub filaments will appear, breakage will occur, and wool filaments will appear.
b. Module leakage
Common forms of module leakage include: 2 types: One is internal and external leakage just 24 hours after being put on, and the melt seeps out from the entrance of the component. Because the amount of leakage is often large, the melt is in the form of white slurry dripping from the outer wall of the component; the other is after one week of being put on. The melt seeps out from the center bolt of the spinneret or the joint between the spinneret and the component body. Due to the leakage, the melt degrades after being retained at high temperature for a long time. The melt turns brown or black, and the degraded melt is extruded from the spinneret. , forming common black threads. Reasons for component leakage: The manufacturing accuracy and material defects of the sealing gasket seriously affect the sealing performance of the spinning component. This causes slurry leakage due to loose sealing after the components are put on the machine; defects in the manufacturing accuracy of the sealing gaskets in the spinneret have a particularly serious impact on spinning production. Under the pressure of the components, the melt penetrates into the larval-free area in the upper center of the spinneret to form a melt. Dead Angle, this part of the non-flowable melt gradually cracks until it turns yellow and turns black after a long period of high temperature. When the plate is repaired at the stop position, the cracked melt is pushed back by the cracking gas and penetrates back into the spinning area of the spinneret, causing black yarn to appear at the spinning position and a high breakage rate during operation. Leakage of the sealing gasket within the spinneret will also cause melt to seep out from the center bolt of the spinneret. Then it gradually spreads to the spinneret plate surface, causing black slurry to appear on the plate surface. The black slurry drips and adheres to the running tow, causing damage to it and producing hair and slurry blocks. In severe cases. Normal production cannot be carried out.
c. Poor panel repairing accuracy
The polyester short fiber device adopts Regular plate repair operations are carried out, and the repair interval is 48 hours. If the trimming accuracy is poor, lint will appear within 48 hours, and even ends may break periodically.
d. Solutions
Optimize the component sand loading plan, metal The quality and proportion of the filter sand affect the filtration performance of the component. In order to slow down the pressure increase of the component while ensuring the filtration performance of the component, filter sand with high compressive strength and no deformation under pressure of 25MPa is used, and the sand installation plan is Multiple optimizations have been carried out to gradually reduce the pressure boosting speed of components; secondly, to control component slurry leakage, the only way to improve the accuracy of sealing gaskets is to control the deviation of the thickness of the sealing gasket to 0.02 mm, with a maximum of no more than 0.04 mm, and to use better materials. Only the best sealing gasket can solve the problem of component leakage. </p
