What is the specific production process of polyester hot melt yarn?

What is the specific production process of polyester hot melt yarn?

The production process of polyester hot melt yarn mainly includes the following steps:

1. Raw material preparation
Polyester chip selection: Low melting point polyester chips are selected as the main raw material. The chemical composition of this chip is mainly polyester polymer, which is formed by terephthalic acid and ethylene glycol through ester exchange reaction. Its characteristic is that the melting point is low, generally between 85℃ and 180℃, which can meet the low melting point requirements of hot melt yarn during processing.
Raw material inspection: Strict quality inspection of polyester chips, including appearance, color, particle size, melting point range, viscosity and other indicators. Ensure that the raw materials meet the production standards to avoid broken wires and uneven thickness in subsequent production due to raw material quality problems.

2. Melt extrusion
Screw extruder preheating: Heat the screw extruder to the set temperature, usually around 200℃ to 260℃, and the specific temperature is adjusted according to the characteristics of the selected polyester chips. The preheating time is generally 1 to 2 hours to ensure uniform temperature inside the extruder and provide stable conditions for raw material melting.
Raw material input and melting: The qualified polyester chips are put into the screw extruder from the feed hopper. The screw rotates under the drive of the motor, pushing the raw materials forward and shearing and stirring them, so that they gradually melt into a uniform melt. In this process, the screw speed and feed rate must be controlled. Generally, the screw speed is 50 to 150 rpm. The feed rate is adjusted according to the equipment and output requirements to ensure the stable supply and quality of the melt.
Melt filtration: The melted polyester melt passes through the melt filter to remove impurities, unmelted particles and gels. The filter usually uses a multi-layer metal mesh or a sintered metal filter element with a filtration accuracy of 5 to 20 microns. Replace or clean the filter regularly to prevent blockage from affecting the melt flow.

3. Spinning molding
Metering pump delivery: The filtered melt enters the metering pump. The function of the metering pump is to accurately control the flow rate of the melt to ensure the uniform thickness of the fiber during the spinning process. The speed of the metering pump is set according to the required fiber fineness and output, generally between 10 and 30 rpm.
Spinning box and spinneret: After the melt comes out of the metering pump, it enters the spinning box. The temperature inside the spinning box is maintained at 220℃ to 260℃ to ensure that the melt maintains good fluidity before spinning. There are multiple spinneret holes on the spinneret, and the hole diameter is generally between 0.1 and 0.5 mm. The melt is extruded through the spinneret holes to form filaments. The material of the spinneret is usually high temperature and corrosion resistant alloy steel, and the surface is specially treated to reduce melt adhesion and spinneret hole clogging.
Cooling molding: The extruded filaments are quickly cooled and formed in the cooling device under the spinning box. The cooling method generally adopts side blowing or ring blowing, with a wind speed of 0.5 to 2 m/s and a temperature control of 15℃ to 30℃. The cooled fiber is initially formed, but still has a certain plasticity.

4. Oiling and winding
Oiling device: The formed fiber passes through the oiling device. The purpose of oiling is to form an oil film on the fiber surface to reduce the friction between the fibers and prevent the fibers from breaking and fluffing during the subsequent processing. It also helps the fiber bundling and winding. The amount of oiling is generally controlled between 0.3% and 1.0% of the fiber weight, and is adjusted according to the type and purpose of the fiber.
Winding device: The oiled fiber enters the winding device for winding and forming. The winding device includes components such as winding rollers, tension controllers and winding motors. The tension of the fiber is adjusted by the tension controller to keep the appropriate tightness during the winding process to avoid loose edges and collapsed edges. The winding speed is generally between 1000 and 3000 m/min, which is adjusted according to the fiber fineness and winding diameter.

5. Post-treatment (optional)
Heat setting: For some polyester hot melt products with high dimensional stability requirements, heat setting treatment is required. The wound fiber is placed in a heat setting furnace and heat treated at a certain temperature and tension. The temperature is generally between 150℃ and 200℃. The time is determined according to the variety and specification of the fiber, usually 1 to 3 hours. Heat setting can eliminate the internal stress generated by the fiber during the production process and improve the dimensional stability and thermal stability of the fiber.
Twisting: Some products need to be twisted to change the appearance and performance of the fiber. The twisting device rotates the twisting roller to give the fiber a certain twist. The twisting direction can be S twist or Z twist, and the twist is generally between 50 and 200 twists/m, which is adjusted according to the product’s usage requirements. The twisted fibers have better elasticity and wear resistance and can be used to produce high-quality textiles.

6. Inspection and packaging
Finished product inspection: Strict quality inspection of the produced polyester hot melt yarn, including appearance, fineness deviation, strength, elongation, melting point, thermal stability and other indicators. The appearance requires the fiber surface to be smooth, uniform in color, without obvious hair, broken yarn and oil stains; the fineness deviation is controlled within ±5%; the strength and elongation meet the product standards; the melting point and thermal stability meet the use requirements.
Packaging and warehousing: The qualified polyester hot melt yarn is packaged, and the packaging method is generally carton or plastic film packaging, which is customized according to customer needs. During the packaging process, attention should be paid to moisture and dust prevention to ensure that the quality of the fiber is not affected during transportation and storage. The packaged finished products are stored in the warehouse and wait for shipment.