Abstract: The invention relates to a method for processing PET polymers in order to form PET pellets. A PET melt is granulated in an underwater granulator in order to form PET pellets, wherein the process water is driven at a temperature below the glass transition temperature of the used PETs in order to produce a golf ball-like surface structure on the pellets during the underwater granulation process.

Abstract: An underwater pelletizer including a die plate, a cutting chamber housing having a cutting chamber and a rotatably drivable cutter head, which is arranged in the cutting chamber for dividing melt strands output from the die plate into pellets. The cutting chamber is flushed through by process water which can be introduced through at least one inlet into the cutting chamber and, together with the cut pellets, can be discharged from the cutting chamber via an outlet. A plurality of flow channels and/or chambers are provided in the cutting chamber housing for generating different process water streams, which include at least one co-rotating flow path passing through at least one cutter head channel through the rotating cutter head, as well as at least one flow path which does not co-rotate and which leads from a fixed inlet into the cutting chamber.

Abstract: A pelletizer with a rotatably drivable cutter head for dividing material strands output from a die plate into pellets, the cutter head being drivingly connected to a drive motor via a drive shaft, and with a feed device for axial adjustment of the cutter head relative to the die plate in the direction of the cutter head axis of rotation. A spindle element of a spindle drive stage of the feed device is configured as a spindle sleeve which is axially firmly seated on the rotating drive shaft between the drive motor and the cutter head. The drive shaft is connected to the cutter head in an axially-fixed and rotationally-fixed manner and transmits the axial movement of the spindle sleeve to the cutter head.

Abstract: A cutter hub and blade assembly supported and driven for rotational and axial movement in relation to the die face of a die plate in an underwater pelletizer including a positive control of such axial movement to obtain and maintain optimal axial position of the cutter hub and blades during the pelletizing operation and to minimize wear of the mechanical components involved. Positive control of the axial movement of the cutter hub and blades is obtained by a hydraulic/pneumatic actuation system controlling an elongated motion rod that extends through a driven hollow motor shaft. One end of the motion rod is connected with a hydraulic/pneumatic control and the other end of the rod is connected to a cutter hub holder that supports the cutter hub and blades for axial movement toward or away from the die face.

Abstract: An adjustable sectioned water flow guide stationarily mounted in the water box of an underwater pelletizer to adjust the flow of pressurized water through the water box in order to accommodate a range of variable process requirements, such as pellet size, water flow, water temperature, melt flow, etc., while preventing pellet distortion and die hole freezing. The length and surface configuration of the water flow guide may be readily adapted through selection of an appropriate number of grooved or ungrooved sections to optimize fluid flow for particular pelletizer applications.

Abstract: An adjustable sectioned water flow guide stationarily mounted in the water box of an underwater pelletizer to adjust the flow of pressurized water through the water box in order to accommodate a range of variable process requirements, such as pellet size, water flow, water temperature, melt flow, etc., while preventing pellet distortion and die hole freezing. The length and surface configuration of the water flow guide may be readily adapted through selection of an appropriate number of grooved or ungrooved sections to optimize fluid flow for particular pelletizer applications.

Abstract: A cutter hub and blade assembly is supported and driven for rotational and axial movement in relation to the die face of a die plate in an underwater pelletizer. The supporting and driving arrangement includes a positive control of axial movement of the cutter hub and blades in relation to the die face as the cutter hub and blades are moved toward and away from the die face to obtain and maintain optimal axial position for the pelletizing operation and to minimize wear on the mechanical components involved. Positive control of the axial movement of the cutter hub and blades is obtained by a hydraulic/pneumatic actuation system controlling an elongated motion rod extending through a driven hollow motor shaft with one end of the motion rod connected with a hydraulic/pneumatic control and the other end being connected to a cutter hub holder that supports the cutter hub and blades to move the cutter hub and blades toward or away from the die face.

Abstract: A filter-replacement cassette for an extruder. A housing (1) has at least one bore. The bores (2 & 3) extend above and below and at a right angle to the horizontally flowing plastic. A cartridge (4 or 5) that accommodates a replaceable filter (5) slides back and forth inside each bore. The object is to facilitate start-up operation. The cartridge accordingly has at least one tap (7, bore 15, or bore 45) permanently integrated into it in addition to the replaceable filter. The housing accommodates either a cartridge or a start-up outlet bore (16, 36, or 47). While the cartridge is in a prescribed position, the start-up outlet bore can communicate with the cartridge's tap and with an intake channel (13 or 31) for the extrudate.