Screw granulator is a molding machine that can make materials into a specific shape. Granulator refers to the unit that adds different additives to the resin according to different purposes, and after heating, mixing, and extrusion molding, the resin raw materials are made into granular products suitable for secondary processing. Plastic granulators are widely used in petrochemical industry.
The underwater granulator is similar to the air granulator and water jet granulator. The equipment mainly covers: plastic granulator, single and double screw plastic extruder, plastic film blowing machine, bag making machine, printing machine, coating. Machine, tape machine, tape slitting machine, slitting machine, packing belt machine. Modified formulations are mainly based on alloy materials, especially PET, PC, ABS, (PP, PA) materials that are currently growing in application areas; plastic formulations have developed formulas such as cling film, degradation film, PET thickening and toughening, etc. . The difference is that it has a steady stream of water flowing through the die surface, but in direct contact with the die surface. The pelletizing chamber is sized just enough to allow the pelletizing knife to rotate freely across the die surface without limiting the temperature of the water flow. The molten polymer is extruded from the die, and the pellets are cut by a rotary knife. The pellets are taken out of the pelletizing chamber by the temperature-adjusted water and enter the centrifugal dryer. In the dryer, the water is drained back to the storage tank, cooled and recycled; the pellets are removed by a centrifugal dryer.
The bar production line has low cost, easy operation and convenient cleaning. This has its advantages for colorant compounding, as the replacement of two different batches of colorant must thoroughly clean the equipment. However, the disadvantage of the sliver making method is that the cooling section requires space, and its length is determined according to the temperature requirements of the polymer.
Most polymers must be compounded before being made into a final product, and then pelletized to become a marketable raw material. The power required by the pelletizer is directly proportional to the amount of extrusion and has an exponential relationship with the screen size. There are many different pelletizer designs, but all pelletizers can be divided into two categories: cold pelletizing systems and die face hot pelletizing systems. The main difference between the two is the timing of the pelletizing process. The cold pelletizing system pelletizes the solidified polymer at the end of the processing process; in the die face hot pelletizing system, the pellets are pelletized when the molten polymer emerges from the die, and the pellets are processed downstream cool down. Both types of pelletizing systems have their advantages and disadvantages.
Cold pelletizing system: Cold pelletizing system includes die, cooling zone (air-cooled or water-cooled), drying zone (if water-cooled) and pelletizing chamber. There are two major types of cold pelletizing systems, namely tablet granulators and bar pelletizers.
The molten polymer is extruded from a hot die and cut into pellets by a rotary knife that rotates against the die surface. This sweet grain system is characterized by its specially designed water jet pelletizing chamber. The water flows in a spiral around the flow until it flows out of the chamber. After the pellets are cut, they are thrown into the water stream for preliminary quenching. The granular water slurry is discharged into the granular slurry tank to be further cooled, and then sent to a centrifugal dryer to remove water.
The use of bar granulators is almost as long as that of tablet granulators. Including die, cooling section (water bath or blower), drying section (if water cooling is used) and pelletizing knife. The extruder or gear pump is used to extrude the molten polymer through a horizontally installed die to form a bar (modern die is processed by precision machining and uniformly heated to produce a bar of stable quality). After the strip is discharged from the mouth, it is cooled with a blower or air / vacuum facility, or with a water bath. If water cooling is used, the bar needs to pass through a drying section, blow off the moisture with forced ventilation, and then send the bar to the pelletizing room. Using the shearing action of a pair of fixed and rotating knives, the strip is accurately cut to the required length.
The shape design of the screw is changed, the screw pitch between the screws is increased, and the plastic can be fully plasticized and melted in the barrel during heating; the use of a variable diameter type increases the relative service life of the screw technically; High-strength 38CrMoAlA improves the performance of the entire machine.
Barrel The design of the barrel adopts 45 # steel after fine processing and quenching treatment, which has high hardness and certain wear resistance and corrosion resistance, and a certain size slot hole is set at the feeding end to facilitate feeding.
Heating system The heating system consists of heating coils, which are separately distributed outside the barrel. The materials in the barrel are uniformly heated and plasticized, and controlled by instruments on the electric cabinet to form automatic adjustment of the set temperature.
Cooling fan In order to achieve the stability of the temperature in the barrel, a cooling fan is added to the bottom of the barrel in the design, and the automatic cooling of the temperature when the temperature is too high increases the barrel temperature stability.
Machine head In order to keep the extruded plastic from extruding due to the decrease in temperature and insufficient fluidity. A heating coil with a certain power is added outside the machine head to ensure the normal fullness of the discharge. And the discharge hole set on the machine head is a parallel 15-hole type, which increases the discharge volume and increases the production speed. The machine head is a structure-type parallel extruder, and the thread is connected with the barrel, which can save time and labor when replacing the screen.
Pelletizing system After being cooled by the cooling system, the bar enters the pelletizer and is rolled into pellets for convenient packaging. The pelletizer is provided with a rolling feed wheel, which is automatically driven by the motor to the material body, and the rolling blade inside the body is cut off.