SPEROTTO RIMAR

Continuous Dry-Cleaning
How to improve dramatically the colour fastness in all poly-cotton fabrics?

The COLOR version of many NOVA models originates from the necessity of improving the colour fastness and increasing the shade brightness of piece dyed articles made with synthetic fibres and namely polyester, or polyester containing blends.

Nova Color is really a special machine
for specialists in dyeing and
finishing who can not be
satisfied with conventional technologies.

The important sectors are 100% polyester, polyester/viscose, polyester/acetate, polyester/elastan, polyester/wool & wool/polyester/elastan.
The disperse dyestuffs used to dye the polyester fibre are water insoluble and, once they have been made to physically diffuse within the fibre by means of HT boiling, the "unfixed" superficial portion can be hardly removed by a simple soaping and rinsing.
That is why an after dyeing chemical treatment of the fabric is absolutely required if an acceptable colour fastness to dry and wet rubbing is desired: such a treatment is known as "reduction clearing".
· Dyeing time is increased by about 30 minutes and the dyeing machine productivity is consequently reduced.
· Additional water, chemicals and energy usage is required and consequent effluent streams are generated.
· The "fixed" disperse dyestuffs are not chemically bound to the polyester fibre, thus they slowly tend to migrate to the fibres surface generating additional colour staining to rubbing during the garment wearing: this is because the aqueous reduction clearing liquor is not able to wet out deeply the hydrophobic fibre and acts on the superficial dyestuffs. As a consequence the shade brightness of the fabric is still unsatisfactory.
· Moreover, some blended fibres are also affected by disperse dyestuffs staining, such as mainly elastan (polyurethane-based elastic fibre) and viscose. The superficially deposited dyestuffs give rise to the same colour fastness and shade brightness problems.
Once the problem has been identified, the proper solution can be worked out.
The perchloroethylene (PER) solvent has a good affinity for the disperse dyestuffs because they are both "hydrophobic" chemicals and, even though PER is not able to really dissolve them completely, it can remove that part of them that is not fixed in textile substrates.
When the textile material is polyester, which is also a hydrophobic chemical having a good affinity for both PER and the disperse dyestuffs, a sort of ternary system is realised in which every component is chemically and physically compatible to each other: (1)Polyester fibre, (2) Disperse dyestuffs and (3) PER solvent.
· Disperse dyestuffs physically link to polyester fibre;
· PER deeply wets out polyester and quickly diffuses into it;
· PER reaches the unfixed dyestuffs molecules more or less superficially allocated in the fibre and removes them in form of fine dispersion and with the aid of an energetic mechanical action;
· A thorough clean solvent rinsing flow removes from the textile the contaminated PER. A Nova solvent scouring machine needs a few special features to become a Nova color solvent scouring machine:
· A higher bath/fabric ratio, which means a higher clean solvent rinsing flow, which involves a more powerful solvent distillation equipment;
· More counter-flow scouring sections, which mean more solvent spraying pipes, more suction tubes, more pumps, more filters;
· An auxiliary solvent reservoir to temporary collect the dyestuffs contaminated solvent when a quick change from dyed to grey fabrics processing is required, which means bigger solvent storage tanks;
· An effective and automatic cleaning system for the scouring unit inside walls and ceiling when passing from dyed to grey fabrics processing.

Nova Ecowarp Color (section view)