During the production process of polyester spunbond nonwoven fabric, appearance quality problems are prone to occur. Compared with polypropylene, polyester production has the characteristics of high process temperature, high moisture content requirements for raw materials, high drawing speed requirements, and high static electricity. Therefore, the production difficulty is relatively high, and the probability of appearance quality problems is high. In severe cases, it may even affect customer use. Therefore, effectively classifying the appearance quality problems that exist in the production process, analyzing the main causes of various problems, and taking effective measures to prevent and avoid common appearance quality problems are the main tasks in the control of polyester spunbond production process.
Overview of Appearance Quality Issues of Polyester Spunbond Hot Rolled Non woven Fabric
There are various appearance quality issues with polyester spunbond hot-rolled non-woven fabrics. Based on years of experience, it can be mainly divided into three categories, as follows: the first category is appearance quality problems caused by spinning factors, such as pulp lumps, stiff fibers, hard lumps, insufficient stretching, unclear rolling points, etc. The second category is appearance quality problems caused by mesh laying factors, such as flipping, punching, continuous small horizontal stripes, vertical stripes, diagonal stripes, black threads, etc; The third type is appearance quality problems caused by environmental factors, such as black spots, mosquitoes, intermittent large horizontal stripes, etc. The article mainly analyzes the causes of these three types of problems and proposes corresponding preventive measures and solutions.
Appearance quality problems and reasons caused by spinning factors
Slurry blocks and stiff fibers
There are many reasons for the formation of lumps and stiff fibers, which have been introduced in many literature materials. The article only analyzes the main reasons for the formation of lumps and stiff fibers during normal production processes: (1) component leakage; (2) Excessive use or improper operation of the spinneret can cause damage to the micropores or foreign objects, resulting in poor wire output; (3) Dry slicing or adding masterbatch with excessively high water content; (4) The proportion of functional masterbatch added is too high: (5) the heating temperature in the local area of the screw extruder is too high; (6) Insufficient release time during start-up and shutdown, resulting in residual degraded melt inside; (7) The side blowing wind speed is too low, causing the fibers to shake too much due to external airflow interference, or the side blowing wind speed is too high, causing the fibers to shake too much.
Preventive measures: (1) When starting and stopping the production line, it is necessary to ensure sufficient release time, try to discharge the melt completely, and use a low melt index polypropylene hot washing system regularly; (2) Pay close attention to the cleaning and assembly processes of components to ensure their integrity on the machine. Before installing components, be sure to clean the melt outlet of the box body. (3) Standardize the use, inspection, and regular replacement of spray nozzles; (4) Strictly control the addition ratio of functional masterbatch, calibrate the addition device regularly, and appropriately reduce the spinning temperature by 3-5 ℃ according to changes in the addition amount; (5) Regularly check the moisture content and spinning viscosity reduction of dry slices to ensure that the moisture content of the main slices is ≤ 0.004% and the spinning characteristic viscosity reduction is ≤ 0.04; (6) Check the replaced faulty components and observe if the melt is visibly yellowed. If so, carefully inspect the heating system for localized high temperatures; (7) Ensure that the side blowing wind speed is between 0.4~0.8 m/s and make appropriate adjustments.
Insufficient stretching and hard lumps
Insufficient stretching and hard lumps are mainly caused by problems with the stretching device and stretching tube. The main reasons for insufficient stretching are as follows: (1) there are fluctuations in the overall stretching pressure; (2) Individual internal wear of the stretching device leads to insufficient stretching force; (3) Insufficient stretching is caused by foreign objects or dirt inside the stretching device. The main reasons for the formation of hard blocks are: (1) foreign objects or dirt in the stretching device and stretching tube causing wire hanging; (2) The surface of the wire separating plate is dirty and the wire separating effect is not good.
Preventive measures: (1) Clean the stretching device and stretching tube after shutdown; (2) Flow inspection must be carried out before the stretching machine is put into operation; (3) Regularly use specialized tools to clean the stretching device (4). Install electric pressure regulating valves on each row of compressed air main pipes to ensure stable stretching pressure; (5) After stopping the machine, carefully inspect all the shims and clean them thoroughly.
Unclear rolling points
The selection of raw materials, process adjustments, equipment selection, equipment failures, etc. may all lead to unclear rolling points. In the actual production process, this problem is mainly caused by fluctuations in the proportion of reinforcing masterbatch added in the spinning part and fluctuations in the rolling mill process: (1) faults in the reinforcing masterbatch adding device, resulting in changes in the addition ratio; (2) The temperature fluctuation of the rolling mill or the malfunction of the heating system cannot reach the set temperature; (3) The rolling mill pressure fluctuates or cannot reach the set internal pressure.
Preventive measures: (1) Regularly maintain and inspect the reinforcement masterbatch addition device to ensure normal operation of the equipment, while ensuring stable product batch numbers from suppliers; (2) Regularly maintain the rolling mill to ensure normal operation of the equipment; (3) Timely and effectively exhaust the heating system of the rolling mill, especially after equipment maintenance or system oil replenishment.
Appearance quality problems and reasons caused by mesh laying factors
Network flushing
The main reasons for punching the net are: (1) excessive stretching pressure, exceeding the process set value by 10%; (2) The inclination angle of the upper swing plate is too large or the distance between the falling point and the lower edge of the swing plate is too close; (2) Below
Low suction wind speed; (3) The mesh belt has been used for too long and some parts are dirty; (4) Partial area of the lower suction device is blocked.
Preventive measures: (1) Regular inspections to ensure stable stretching pressure; (2) Set appropriate suction air speed according to different product varieties; (3) Before the stretching machine is installed, a flow check must be carried out. If excessive flow is found, it should be replaced or manually adjusted to reduce the stretching pressure in a timely manner; (4) Before starting up, carefully check all swing angles and the distance from the bottom outlet of the stretching tube to the swing to ensure normal thread separation; (5) Regularly clean, replace the mesh belt, and clean the suction device.
Flipping the Net
The main reasons for flipping the net are: (1) severe yarn breakage during spinning, resulting in serious hanging of yarn at the outlet of the stretching tube; (2) The wire hanging device has serious wire hanging; (3) Insufficient fiber stretching at certain positions on the web, causing the web to flip over when passing through the pre pressing roller; (4) The local wind speed around the mesh laying machine is too high; (5) The surface roughness of the preloading roller does not meet the requirements, and there are burrs in some areas; (6) The temperature of the pre press roller is too low or too high. If the temperature is too low, the fiber web is easily blown up by the wind or sucked up due to static electricity during its movement. If the temperature is too high, the fiber web is easily entangled with the pre press roller, causing it to flip over.
Preventive measures: (1) Reduce the stretching pressure appropriately to ensure stable spinning; (2) For positions that are prone to hanging threads, use 400 grit sandpaper to polish them; (3) Ensure stable stretching pressure, replace the stretching device with insufficient stretching force, and ensure that the stretching pressure meets the design requirements before pressing down the pre pressing roller when starting up; (4) When heating the pre press roller, pay attention to exhaust to ensure that the system temperature meets the requirements. At the same time, adjust the set temperature of the pre press roller in a timely manner according to the specific situation of the product variety; (5) Regularly check the surface roughness of the pre press roller, and promptly send it for surface processing if there are any problems. Before starting up, check the roller surface and polish the areas with burrs; (6) During the production process, it is essential to keep the workshop closed to prevent local airflow disturbances.
Continuous small horizontal stripes
The reasons for the generation of continuous small horizontal stripes are: (1) inappropriate gap between the pre pressing rollers; (2) Partial fiber stretching is insufficient, resulting in uneven shrinkage when passing through the pre press roller. There are two situations: one is the full width range, where the stretching pressure of the entire row of fibers is low, and the other is the fixed width position, where the stretching force of the stretching device is insufficient; (3) The speed of the hot rolling mill does not match the speed of the pre press roller. If the speed of the hot rolling mill is too fast, it will cause tearing, while if the speed is too slow, it will cause severe delamination of the fiber web due to gravity when it leaves the mesh belt, resulting in fine horizontal stripes after hot rolling.
Preventive measures: (1) Adjust the appropriate pre pressing roller gap according to different production varieties; (2) Regularly inspect and adjust to ensure stable stretching pressure, and replace defective stretching devices in a timely manner: (3) Adjust the appropriate pre pressing roller speed based on the state of the fiber web after leaving the pre pressing roller on the mesh belt during production of different varieties, and adjust the matching speed of the hot rolling machine according to the condition of the fiber web leaving the mesh belt.
Vertical and diagonal lines
The main reasons for vertical and diagonal lines are: (1) high temperature of the pre press roller; (2) The speed of the hot rolling mill does not match the speed of the pre pressing roller, which leads to excessive tension in the fiber web; (3) The gap between the two ends of the pre press roller is inconsistent, and if the gap is too small, diagonal or vertical lines may appear on one side.
Preventive measures: (1) Set appropriate pre pressing roller temperature according to different production varieties; (2) Adjust the speed of the hot rolling mill and pre press roller according to the mesh laying status: (3) Correct the gap between the pre press roller and the mesh belt when stopping, and use special tools to ensure that the gap between the two ends is consistent when adjusting the gap between the pre press roller.
Black Thread
The reasons for black silk production are: (1) poor hygiene around the stretching device and swinging device; (2) The inside of the stretching tube is dirty and the broken fibers are close to the tube wall; (3) Mesh belt hanging wire.
Preventive measures: (1) Regularly clean the perimeter of the stretching device and swinging wire device to maintain cleanliness; (2) Regularly clean the stretching device and stretching tube; (3) Timely clean the mesh belt hanging wire and polish the frequently occurring hanging wire positions.
Appearance quality issues and their causes caused by environmental factors
Black Spot
The reasons for the black spots are:(1) poor hygiene around the spinning and spinning equipment;(2) The film has not been cleaned for a long time;
(3) Diesel forklift enters the workshop
Preventive measures:
(1) Regularly clean and keep the workshop clean; (2) Regularly clean the layout; (3) Diesel forklifts are prohibited from entering the workshop during normal production.
Mosquitoes and Mosquitoes
The reasons for mosquito production: (1) Moths, mosquitoes, termites, etc. are mainly caused by incomplete closure of the workshop or failure to enter and exit the workshop according to regulations; (2) Small black worms mainly breed in hygiene blind spots or local water accumulation areas inside the workshop.
Prevention and control measures: (1) Check the workshop and close it.
Horizontal stripes
Horizontal stripes refer to large intermittent stripes that appear regularly, usually once when the lower roll of a hot rolling mill rotates. The causes of this problem are: (1) low environmental humidity and high static electricity on the fiber web. When entering the hot rolling mill, the fiber web structure is damaged due to static electricity, resulting in fiber web misalignment; (2) The mismatch between the speed of the hot rolling mill and the speed of the pre press roll results in the separation and misalignment of the fiber web when it enters the hot rolling mill due to gravity induced static electricity.
Preventive measures:
(1) Install necessary humidification devices in the workshop to humidify when the ambient humidity is below 60%, ensuring that the humidity in the workshop is not less than 55%; (2) Adjust the appropriate speed of the hot rolling mill according to the state of the fiber web to ensure stable state when the fiber web enters the hot rolling mill.
Conclusion
There are many theoretical reasons for the appearance quality problems that occur in the production process of polyester spunbond hot-rolled non-woven fabric, and some reasons cannot be quantitatively analyzed. However, the causes of product appearance quality problems in the actual production process are not complex, and the difficulty of solving them is not high. Therefore, in order to reduce or even eliminate appearance quality issues in the production of polyester spunbond hot-rolled non-woven fabrics, it is necessary to strengthen management and provide necessary training to better meet customer requirements and improve enterprise efficiency.
Keywords: polyester spunbond fabric, appearance quality, spinning fabric, laying mesh, non-woven fabric
Post time: Aug-15-2024