TNT High-Density Fiber Dyeing (CHD, PHD, CS, DAP)

Long ago POZZI introduced a new technique for dyeing high-density loose fibres loaded in baskets: this technology has now been extended to the dyeing of tops, bumps and tow.

The system relies on the use of a "basket” module in which the loose fibres are loaded and moved to the various working stations.
The main advantages of this technique are:
  • Levelling out of differences in the loading density and, thus, improve the result in dyeing uniformity
  • A greater loading capacity than the one that can be obtained with traditional systems and, as a result, a reduction in the number of machines required to produce the same amount of material.
  • Reduction in the bath ratio to 1:5 and, therefore, considerable reductions in the consumption of steam, electricity, auxiliaries and water.
  • A reduction in labour due to the limited number of manual operations involved.
  • A reduction in the amount of space required for stocking the dyed material.

High-density loose fibres are produced using specific machinery during all phases of production:
the material is loaded into baskets using a PHD mod. wet press which enables a high loading density to be obtained.
The baskets prepared in this way are loaded on the dyeing machines.
After dyeing, the baskets are hydroextracted.
The following operation is the removal of the dyed loose fibres from the baskets.
The cake may be plucked while this operation is performed.
Using the GIR plucking machine, the loose fibres lifted from the basket are opened by a toothed wheel and conveyed to the drying chamber or directly to the packing press.
This solution is particularly suited to medium capacities with fibres lenght of up to 30 mm.
Alternatively, an automatic DAP extractor may be used for removing the dyed fibres from the basket.
A special PHD-top loading press is also used for dyeing Tops.
Tops are set in the PHD press container, which automatically lifts to operators waist height and, in a single operation, are pressed and closed in the dyeing basket with a density of 400 Kg/m3.

The first advantage is the elimination of rereeling: boreless Tops with a diameter of 400 or 600 mm, or material in the form of Bumps, can be dyed in the same package delivered by the various manufacturers.
Machines can generally hold 1 or 2 baskets.
After dyeing, the baskets are hydroextracted and then can be moved inside the hydroextractor.
The Tops can be removed from the baskets using an automatic DAP extractor and the cake of material can be handled and stored on pallets.

The material can be dried using a dielectric drying chamber where the Tops are inserted and return to their original form, as a result of the action of the steam generated during the drying process.            
 The Tow producing technology is exactly the same as the one described for Tops.
As for the machinery, only the loading press has different characteristics, which may be summarized as follows:
  •     Alternating rotation of basket during loading phase.
  •     Special Towfeeding device with folder mounted on a rotating column.
  •     Device for wetting material during loading.
A loading density of 500-600 Kg/m3 may be obtained.
The high-density dyeing system applied to tow processing has provided an alternative to continuous dyeing which often has its application limited by minimum lot size.
The hydroextractor has a special device for adding oil to the fibre.
After centrifugation, the basket is unloaded on a pallet.
Drying can be performed on a belt machine on which the tow is laid.


a 2-basket machine with preparation tank

PR80 press

basket press

DAP extractor

the automatic opener/extractor for baskets