The toner formulation, consisting of resins, pigments, and additives, is processed in a blender to produce a premix. It may contain fines that must be reprocessed.

This premix is fed continuously to the twin-screw compounder (ZSK) via a metering device. The premix is added to the feed barrel
(barrel no. 1) via a chute.

The co-rotating, closely intermeshing screws of the ZSK twin-screw compounder convey and then compress the product in order to melt or plasticize it with the kneading elements in the plastification zone (barrels 2-3). During and after the plastification process, the individual components of the formulation are dispersed, mixed, and homogenized. To help in this task the screw rpm of the ZSK twin-screw compounder is adjustable. The throughput depends on the product quality, the feed behavior of the product, and the drive capacity of the ZSK twin-screw compounder. Another important criterion is the amount of fines to be processed and their grain structure. The throughput has to be matched to the corresponding values.

Barrel no. 4 has a vent port whose function is designed specifically for the processing of fines. The vent in barrel no. 7 is used depending on the formulation. It is possible to close the barrel or to devolatilize at atmospheric pressure or under vacuum.

The compounded melt is discharged vertically downwards at atmospheric pressure, through a die in the last barrel. The product is cooled and pre-pelletized in a cooling device as preparation for the subsequent grinding.

Plant for the production of toner.

1 Volumetric feeder 2 Extruder

3 Compact cooling 4 Pre-grinding

ZSK flange barrel with exchangeable, wear-resistant oval liner.
Highly wear-resistant ZSK kneading block with special internal profile.