Compounding & Co-extrusion - Fields of application

Gear pumps for compounding

Plastic compounding is a continual, multi-stage process using extruders where polymers and additives are mixed with each other in the melt phase. The discharge materials are dosed in the extruder. The material is mixed into a homogeneous melt in the extruder and then formed into small pellets in a granulator. A gear pump is normally in front of the granulator, which provides constant pressure build-up for consistent granulate. The end products include mono-pigment, additive master batches as well as filler and reinforced-fiber compounds. Large gear pumps are used in particular during the compounding of polyolefins such as LDPE, LLDPE, HDPE and PP.

To the pumps program

Gear pump solutions for compoundiong tasks

The WITTE pump program for use in compounding and for the manufacture and processing of e.g. Polyolefins.

Melt pumps of the [BOOSTER] series for compounding

Shafts
Rotary feedthrough
Housing bore / heating channel
Friction bearing
Threaded shaft seal drive side
Threaded shaft seal

Shafts

Different types of gears are available for the BOOSTER melt pumps in the compounding version. Depending on the polymer used, you can choose between straight or helical teeth, as well as between gears in the standard width or narrower widths.
Rotary feedthrough

In order to keep the process temperature constant, the shafts of the compounding pumps can be tempered. This ensures the consistent product quality even at higher flow rates, since the temperature of the melt can be maintained at a constant temperature level.
Housing bore / heating channel

The housing of the BOOSTER melt pumps is equipped with heating bores for hydraulic temperature control. The holes are usually set that the largest possible heat transfer surface is available. The temperatures can be regulated precisely.
Friction bearing

The established WITTE friction bearing technology ensures a reliable build-up of the hydrodynamic lubricant film in the bearings. Special pockets ensure good lubrication film build-up and reliable heat dissipation from the bearings.
Threaded shaft seal drive side

For secure operation of the melt pumps, these are equipped with a total of 4 threaded shaft seals. For particularly sensitive polymers, the pump can also be equipped with the "Bleeding Bearing technology". The bearing lubrication flow is directed out of the pump through the seal. This avoids any degenerated material due to lubrication, which returns to the product flow and have negatively affects to the product quality. The committee is thereby minimized.
Threaded shaft seal

In compounding, plastics are refined for later use by adding or blending additives. Compounding serves to specifically optimise the properties of the plastic, tailored to its later use.

The refinement of plastics is usually carried out with the aid of a twin screw extruder. This so-called twin-screw extruder conveys the polymer through two intermeshing, rotating screws to the extruder outlet or the next process stage. The material passes through different zones in the extruder, where it is melted and converted into a plastic moulding compound with the addition of additives. Talc, release agents, fibres, antioxidants and various other additives are used in the compounding process.

By adding the additives, physical, thermal, electrical or even aesthetic properties of the plastic are changed in the plastic compounding process.

The BOOSTER series for safe and reliable operation in compounding. Melt pump for high-viscosity co-polymer in compounding design with cooled shafts and narrower gears for reduced bearing loads.