Granulation process is not required to be finished on land, it can also be carried out underwater. For an underwater granulator, a steady stream of water flows over the surface of die plate, and the molten polymer is extruded from the die. In the drier, water is transferred into storage tank, cooled and reused, and the granules are processed with centrifugal drier to remove water.
The production line of strip features low price, easy operation as well as convenient cleaning, and this is meaningful for the production processes of different materials because the equipment should be entirely cleaned if two different coloring materials are processed one after another. However, this method also has some disadvantages. For example, the cooling section takes up some space, and its length is determined by the temperature of polymer. Before most polymers are made into end products, mixing procedure is a must, then granulation is carried out. In addition, the power required by the granulator has a direct proportion to extrusion amount, and has an exponential relationship with filter size.
There are many different designs for distributor, but all the agglomerators can be divided into two categories, cold cutting system and die surface hot cutting system. The major difference of these two systems lies in the cutting time of particles. For the cold cutting system, at the end of processing, the polymers are solidified, and then are cut. For the die surface hot cutting system, the molten polymers are cut when they are at the die, and then the particles are cooled at later process.