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Melt compounding and pelletizing is used in instances where direct extrusion of dry-blend into a finished part is not possible or economical. The reasons may be frequent product changes, small batch sizes, difficult processing conditions, problematic storage or housekeeping and other logistical issues.
The plant diagram below shows a typical set-up for PVC processing lines, from handling and dosing of raw materials through dry-blend manufacturing in the pre-mixer, to compounding / pelletizing and pellet cooling.
The two-stage Coperion systems are equipped with a volumetric feeder, a vacu-um degassing unit and a pelletizer.
Complete turn-key plants are designed and built in collaboration with Coperion Waeschle.
| Plasticized PVC (PVC-P) |  |  |
| - | | PVC cable: insulation, sheathing and bed-ding compounds |
| - | | Shoe and shoe sole material (also PVC-P with blowing agent) |
| - | | Extrusion materials for profiles and hoses (including medical applications) |
| - | | Injection molding compounds |
| - | | Calendered film and sheets for flooring |
| Rigid PVC (PVC-U) | | |
| - | | Extruded profiles for interior and exterior uses |
| - | | Injection molding grades for fittings etc. |
| - | | Blow molding grades such as bottles, containers etc. |
| - | | Alloys and blends |
| - | | Films (calender feeding) |
| - | | Calendered films for packaging |
| Process stages | | |
| - | | Feeding of dry-blend from the hot mixer or heating-cooling mixer combination into the Kombiplast processing chamber |
| - | | Preheating, mixing and gelling the premix |
| - | | Possible feed of pigments and other com-ponents (solid or liquid) directly into the processing chamber |
| - | | Degassing the compound in the transition chute, using vacuum |
| - | | Conditioning and building up pressure for pelletizing, and / or screening of flexible PVC (cable compounds) in the single- discharge screw |
| - | | Eccentric dry-cut, wet-cut or underwater pelletizer |
| - | | Pneumatic conveying and cooling in a fluidized bed |
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