The Plastic Pelletizing Process: From Flakes to Uniform Pellets
In the modern plastics industry, pelletizing is a core link, transforming diverse plastic raw materials into plastic pellets with uniform specifications and stable performance. Plastic pelletizing is more than a simple process of melting and cutting; it is a systematic process integrating pretreatment, precision plasticization, efficient filtration, and intelligent molding. Every detail of the process directly impacts the gloss, uniformity, mechanical properties, and subsequent processing performance of the final pellets.
Phase One: Plastic Raw Material Sorting
The starting point of all high-quality recycled pellets begins with the precise identification and sorting of plastic raw materials.
Post-industrial recycled materials: Sourced directly from production facilities, these materials have never entered the consumer waste stream. For these materials, we recommend a simplified pretreatment process, typically requiring only crushing before entering the pelletizing stage. This shortens the process, reduces recycling costs, and produces a finished product with quality close to that of virgin material.
Post-consumer recycled materials: These materials originate from plastic products used in daily life, such as packaging bottles and daily necessities. They have a complex composition, often mixed with mud, oil, labels, metal, and even other types of plastic. KiTech offers a variety of sorting solutions, including manual sorting, wind power sorting, flotation tanks, and near-infrared spectroscopy, to effectively remove impurities and group similar materials, laying the foundation for pure raw materials for subsequent cleaning and pelletizing.
Second Stage: Crushing and Washing
1. Shredding and Crushing
Direct pelletizing is extremely difficult for large plastic products (such as barrels, frames, appliance housings, and plastic film). Our heavy-duty shredders and powerful crushers efficiently break them into uniformly sized flakes or chunks. This step not only reduces the material volume for easier conveying, but also significantly increases the material's specific surface area, ensuring more uniform heating during the subsequent melting process and better plasticization, thereby improving extrusion efficiency and product quality.
2. Deep Washing and Drying
Plastic Washing is a critical step in removing surface contaminants. Our integrated cleaning system typically includes multiple steps, including pre-washing, hot washing, and rinsing. By strategically adjusting the impact force of the water flow, the detergency of the cleaning agent, water temperature, and cleaning time, we can effectively remove stubborn impurities such as labels, sand, and oil stains. The subsequent high-speed friction dehydration and cyclone drying system quickly reduces the surface moisture of the material to extremely low levels, preventing quality issues such as bubbles and degradation during the pelletizing process caused by residual moisture.
Third Stage: Extrusion and Precision Filtration
1. This is the "heart" of plastic pelletizing, directly determining melt and pellet quality.
High-Efficiency Plasticizing Extrusion: Extruders are generally divided into two types: single-screw extruders and parallel twin-screw extruders. Single-screw extruders are suitable for stable pelletizing of most general-purpose plastics; twin-screw extruders, with their superior mixing, shearing, and self-cleaning capabilities, are particularly suitable for high-end applications such as filling, modification, and those requiring extremely high uniformity. KiTech extruders utilize a modular temperature control system, enabling precise temperature control in every section from the feed zone to the die head, ensuring complete and uniform plasticization of the plastic.
2. Precision Melt Filtration: To achieve the highest purity of plastic melt, it must pass through a screen changer after extrusion to enhance the product's color, transparency, and mechanical properties. KiTech offers a full range of screen changer solutions.
Plate Screen Changer: A single-plate, dual-station screen changer allows switching between two filters, boasting a large filtration area and enabling continuous screen changes. Equipped with ceramic heating, it precisely controls melt temperature and is suitable for high-volume continuous production lines (e.g., sheet, film, pipe, and pelletizing).
Cylinder Screen Changer: Utilizing cylindrical filter cartridges (single or double), this compact design offers an exceptionally large filtration area, making it particularly suitable for processing high-volume materials and enabling continuous filter changes. It is ideal for large-scale, high-volume recycling operations, particularly for processing recycled materials with high impurity content (e.g., PP, PE, PS, PA, and ABS).
Auto Laser Screen Changer: A fully automatic laser screen changer eliminates the frequent downtime and labor costs associated with traditional manual screen changers, achieving truly continuous operation. The core laser screen is made of durable 1.5 mm thick alloy steel, significantly extending its service life and reducing replacement frequency and costs.
Fourth Stage: Pelletizing and Packaging
After plasticization and filtration, the plastic melt passes through the die head and is cut into uniformly sized, tail-free, and non-sticky plastic pellets by a pelletizing system. There are three common plastic pelletizing methods: water ring pelletizing, strand pelletizing, and underwater pelletizing. KiTech Machinery can customize these methods based on user preferences.
Vibration and Drying: The pellets immediately enter a vibration drying system, which filters the plastic pellets and thoroughly removes surface moisture, ensuring dry pellets.
Intelligent Storage and Packaging: The dried, high-quality pellets are conveyed by air conveyor or elevator into a finished product silo. Finally, an automatic weighing and packaging system packages them into uniform bags or ton bags for easy storage, transportation, and sales.
KiTech Machinery is committed to helping customers reduce labor and operating costs and ensure consistent product quality through highly automated, integrated solutions.