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What aspects need to be controlled in the production process of polyester fiber
source：www.kingcharmgroup.com | Release time：2025-11-051. Raw material refining process
This step determines the basic quality of the polymerization reaction, which requires removing impurities from the raw materials and stabilizing the composition ratio.
Control the purity of terephthalic acid (PTA) and ethylene glycol (EG), requiring a purity of over 99.9% to avoid impurities affecting the efficiency of polymerization reaction and the mechanical properties of fibers.
Adjusting the molar ratio of PTA to EG is usually controlled between 1:1.1 and 1:1.3. Imbalance in the ratio can lead to unstable polymerization degree and affect fiber strength.
2. Aggregation reaction stage
This is the key to generating polyester chips, which requires precise control of reaction temperature, pressure, and time to ensure uniform polymerization degree.
Temperature control in stages: The temperature in the ester exchange stage is controlled at 220-260 ℃, and gradually increased to 270-290 ℃ in the condensation stage. If the temperature is too high, it will cause the raw materials to decompose, and if it is too low, the reaction will be insufficient.
Control reaction pressure: High vacuum (vacuum degree ≤ 100Pa) should be maintained during the condensation stage to accelerate the discharge of small molecule by-products (such as EG) and promote the increase of polymer molecular weight.
Monitoring reaction time: The total reaction time is usually controlled within 4-6 hours. If the time is too long, it can lead to polymer degradation, while if it is too short, the degree of polymerization will be insufficient.
3. Spinning forming process
To convert polyester chips into primary fibers, it is necessary to control the melting state and spinning process to ensure uniform fiber diameter.
Control melting temperature: The temperature of each section of the screw extruder needs to be set in a gradient, usually between 270~290 ℃, and the temperature fluctuation should be controlled within ± 2 ℃ to avoid uneven melting of the slices and spinning breakage.
Adjust the spinning speed: The wire speed of the spinning head is generally controlled between 1000~3000m/min. If the speed is too fast, the fibers will be too fine and uneven, while if it is too slow, the production efficiency will be low.
Stable cooling conditions: Side blowing or ring blowing cooling is used, with cooling air temperature controlled at 20-30 ℃ and wind speed maintained at 0.5-1.5m/s to ensure rapid and uniform solidification of primary fibers and avoid structural defects.
4. Post processing steps
To improve fiber performance through stretching, shaping and other processes, it is necessary to control the stretching ratio and shaping temperature to lock in the fiber structure.
Control stretch ratio: Adjust according to the fiber application. The stretch ratio for civilian filament is usually 3-5 times, and for industrial filament it can be increased to 5-8 times. Insufficient stretch can lead to low fiber strength, while excessive stretch can easily cause breakage.
Adjusting the setting temperature: The setting temperature is generally between 120-180 ℃, which should be lower than the melting point of polyester (about 255 ℃), in order to eliminate internal stress in fibers, improve dimensional stability, and avoid shrinkage deformation during subsequent use.
Control winding tension: The tension during winding needs to be uniform, usually controlled at 5-20cN. Fluctuations in tension can cause poor winding forming and affect subsequent weaving processing.
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