PP Wiredrawing Melt Pump

Definition and Basic Principle

The PP wiredrawing melt pump is a key piece of equipment used in the polypropylene (PP) wiredrawing production process. Its main function is to accurately convey PP materials in a high - temperature molten state. Its working principle is based on that of a gear pump. Through a pair of meshing gears rotating inside the pump body, the melt is sucked in from the inlet and then, driven by the gears, is conveyed along the flow channels of the pump body to the outlet. During this process, the rotational speed of the gears and the volume between the teeth determine the amount of melt conveyed, thus achieving precise control of the flow rate of the PP melt.

Structural Composition

Pump Body: Usually made of high - strength alloy steel, it can withstand the high - temperature and high - pressure PP melt. The inside of the pump body has precisely machined flow channels to ensure the smooth passage of the melt. For example, some pump bodies adopt special inner - surface treatment processes to reduce the friction of the melt in the flow channels and prevent material retention and degradation.

Gear Assembly: This is the core part of the melt pump. The gears are generally made of high - quality alloy steel or special engineering plastics, with high - precision tooth profiles and good wear - resistance. The two gears are closely meshed. During the rotation process, one gear drives the other to rotate. Parameters such as the number of teeth, module, and tooth width of the gears are designed according to different flow requirements and melt characteristics.

Heating and Cooling Devices: Since PP needs to be kept in a molten state during the wiredrawing process, the melt pump is equipped with a heating device, usually an electric heating rod or heating coil, which can uniformly heat the pump body and the gear assembly to maintain the PP melt at an appropriate temperature. At the same time, to prevent PP degradation caused by excessive temperature, a cooling device such as a cooling water channel is also provided to control the temperature through circulating cooling water.

Sealing System: To prevent the leakage of the high - temperature and high - pressure PP melt, the melt pump adopts a high - performance sealing system. Common sealing methods include mechanical seals and packing seals. The mechanical seal uses a pair of sealing end faces perpendicular to the shaft. Under the action of fluid pressure and elastic elements, they remain closely fitted to prevent melt leakage. The packing seal achieves sealing by filling soft packing materials such as asbestos and polytetrafluoroethylene between the shaft and the pump body.

Performance Characteristics

High - Precision Flow Control: The PP wiredrawing melt pump can accurately control the flow rate of the PP melt, with the error controllable within a very small range. This is crucial for the quality of PP wiredrawing, as a stable flow rate can ensure that the thickness of the wire is uniform. For example, when producing PP wires with a diameter of 1 - 3mm, the melt pump can ensure that the diameter deviation of each wire does not exceed ±0.05mm.

Stable Pressure Output: It can stably output the PP melt within a certain pressure range, providing a stable pressure environment for the wiredrawing process. This helps to overcome the resistance of the melt at the die and spinneret, making the wiredrawing process smoother. At a high wiredrawing speed, stable pressure can prevent the melt from fluctuating in the pipeline, avoiding wire breakage or uneven thickness.

High Temperature and Wear Resistance: Due to the high temperature and certain viscosity of the PP melt, the melt pump needs to have good high - temperature resistance and wear - resistance. It can work stably for a long time in a high - temperature environment of 200 - 300°C, and the wear of the gears and the pump body is relatively small, resulting in a long service life. Under normal maintenance conditions, the service life of a PP wiredrawing melt pump can reach 3 - 5 years.

Good Compatibility: It is compatible with different types of PP raw materials and various additives. Whether it is homopolymer PP, copolymer PP, or PP materials added with antioxidants, lubricants, etc., the melt pump can effectively convey them without being affected by changes in the material composition.

Application Scenarios

PP Fiber Production: When producing PP fibers for applications such as textiles, geotextiles, and ropes, the PP wiredrawing melt pump is an essential device. It can accurately convey the PP melt to the spinning components to ensure the quality and output of the fibers. For example, when producing PP fibers for making carpets, the melt pump can provide a stable melt flow rate according to the process requirements, enabling the fibers to meet the standards for strength and toughness.

PP Woven Bag Production: For the wiredrawing process of PP woven bags, the melt pump can control the flow rate and pressure of the PP melt, producing PP wires with uniform thickness for the weaving of woven bags. During this process, a stable melt supply can improve the quality and production efficiency of woven bags. For example, in large - scale woven bag production factories, the melt pump can work continuously for several hours or even several days to provide a stable PP melt for the production line.

PP Strapping Tape Production: In the production of PP strapping tapes, the melt pump also plays an important role. It can ensure that the PP melt is evenly conveyed into the mold to produce strapping tapes with consistent quality. For example, when producing PP strapping tapes for the logistics industry, the extrusion melt pump can accurately control the melt flow rate according to the specifications of the strapping tapes, making the strength and size of the strapping tapes meet the standards.

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