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What are the precautions for spinning polyester fibers in the forming process
source：www.kingcharmgroup.com | Release time：2026-01-131、 Melt preparation and transportation: ensuring the purity and stability of raw materials
1. Slice drying pretreatment
The moisture content of polyester chips should be controlled below 0.005%, otherwise the moisture will vaporize during high-temperature melting, resulting in the formation of bubbles, wire breakage, or defects in the melt. Drying requires the use of a vacuum rotary drum dryer, with a temperature setting of 160-180 ℃ and a time of 4-6 hours, while avoiding excessive drying of the slices that may cause molecular chain degradation and affect melt viscosity.
2. Correct control of melting temperature
The melting temperature of the screw extruder is regulated in three stages: the feeding stage is 250-260 ℃, the compression stage is 265-275 ℃, and the metering stage is 270-280 ℃. The temperature deviation of the melt should be controlled within ± 2 ℃. Low temperature can lead to insufficient melting of the slices, uneven viscosity of the melt, and fluctuations in the thickness of the spun silk strands; Excessive temperature can cause thermal degradation of polyester molecules, decrease in melt viscosity, and decrease in fiber strength.
3. Melt filtration and impurity removal
The molten material needs to pass through a stainless steel metal filter (precision 20-40 μ m) or a candle filter to remove mechanical impurities and unmelted particles from the slices, prevent clogging of the micro holes in the spinneret, and ensure uniform wire forming. Regularly replace the filter screen to avoid impurities accumulating and causing fluctuations in melt pressure.
2、 Spinning board extrusion: ensuring the initial forming quality of the wire strip
1. Selection and maintenance of spinneret
The pore size and aspect ratio (usually 10:1-20:1) of the spinneret determine the fiber fineness and morphology, and should be selected according to the product specifications. Before use, the spinneret needs to be cleaned with ultrasonic waves to remove residual melt coking materials in the micropores; Regular cleaning of the board surface is required during use to prevent the melt from coking on the board surface and causing wire adhesion.
2. Stable control of melt pressure
The pressure of the melt passing through the spinneret needs to be kept stable, generally controlled at 10-30MPa. Pressure fluctuations can lead to inconsistent extrusion rates of various micropores and large deviations in filament line density. The melt pressure can be maintained constant by adjusting the screw speed and metering pump frequency.
3、 Cooling and solidification: determining the initial structure of the filament
1. Optimization of cooling air system parameters
A circular cooling air device should be installed below the spinneret, with a cooling air temperature controlled at 20-25 ℃, a wind speed of 0.3-0.8m/s, and a vertical and uniform wind direction. Excessive wind speed can cause uneven cooling of the filament, resulting in a skin core structure; If the wind speed is too slow, the cooling will be insufficient, and the filaments are prone to sticking, affecting subsequent stretching.
2. Control of cooling distance
The distance from the spinneret to the oiling device (cooling zone height) is generally 800-1200mm. If the distance is too short, the filament may not fully solidify and is prone to breakage when stretched; If the distance is too long, the rigidity of the wire increases and the tensile performance decreases.
4、 Stretching and shaping: improving fiber mechanical properties
1. Stretch temperature and fold control
The initial silk has low strength and high elongation, and needs to be subjected to hot stretching to improve its orientation. The stretching temperature is divided into two stages: room temperature stretching (room temperature) and hot stretching (80-120 ℃, heated by a hot water tank or hot roller), with a total stretching ratio of 3.5-5 times. Low stretching ratio, insufficient fiber orientation, and low strength; Excessive multiples increase fiber brittleness and decrease elongation at break.
2. Heat setting treatment
The stretched fibers have internal stress that needs to be eliminated by heat setting to improve dimensional stability. The setting temperature is 160-180 ℃, the time is 10-30 seconds, and the setting tension is moderate. The setting temperature is too low, the internal stress is not fully eliminated, and the fiber boiling water shrinkage rate is high; If the temperature is too high, the fiber molecular chains will lose orientation and the strength will decrease.
5、 Oiling and winding: ensuring subsequent processing performance
1. Uniformity of oiling
After cooling, the filament needs to be oiled in an oil tank or oil roller, with an oil concentration controlled at 5% -10% and an oiling rate of 0.3% -0.5%. The oil agent needs to evenly cover the surface of the filament to provide lubrication and anti-static effects, preventing the occurrence of fuzz and breakage during subsequent springing and weaving.
2. Winding speed and tension
The winding speed is adjusted according to the product specifications. The conventional polyester filament winding speed is 3000-4000m/min, and the tension is controlled at 0.1-0.3cN/dtex. Excessive winding tension can cause the silk cake to form tightly, leading to the formation of hard edges; If the tension is too low, the silk cake is prone to edge collapse, which affects subsequent rewinding.
6、 Process environment and equipment maintenance
1. Workshop environment control
The spinning workshop needs to maintain constant temperature and humidity, with a temperature of 22-28 ℃ and a relative humidity of 50% -60%, to prevent dust and oil from entering the production system and contaminating the melt and filament.
2. Regular maintenance of equipment
Regularly clean the coking materials in the screw and melt pipelines, check the accuracy of key components such as metering pumps, spinnerets, and hot rollers, and prevent equipment failures from causing fluctuations in process parameters.
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