Canvas dyed water proofing
Process Sequence for Dyed Water Proof finish:
Scouring/Bleaching/Dyeing --- in Jumbo Jiggers
Drying of Dyed fabric --- Cylinder Drying Machine
Padding of water proof mixture --- 3 bowl padding mangle - 2 dips and 2 nips
Drying of Padded fabric --- Cylinder Drying Machine
After Treatment of Proofed fabric --- in Jumbo Jiggers
Drying of Proofed fabric --- in Cylinder Drying Machine
This is the general sequence of operations that is being carried out in Canvas Processing Units.Scouring, Bleaching and Dyeing of Canvas Fabric:
Scouring and Bleaching:
It is obvious that a water proofing by it name itself is making the fabric leak proof when some water quantity is store over the fabric surface. So the process is filling the total fabric surface with some flexible coating and make it leak proof.
A simple wetting out treatment with an anionic wetting agent followed by a peroxide bleach for a short duration is the over all scouring and bleaching operation put together. This would be carried out in open jiggers for a maximum period of 45 to 60 minutes.
A thorough washing off of alkali and wetting agents is the next process. A hot wash - 2 ends and a cold wash 2 ends, will do.
Neutralization of pH alkalinity is the next step. An usual practice is use of 1 to 1.5% w/w of Acetic acid at room temperature is employed.
Vat dyeing is the best choice as for as a quality manufacturing of weather proof canvas is concerned. Vat dyeing takes place for around 60 minutes. (oxidation and neutralization - all would take further 1 hour time).
If pigment dyeing is preferred by you, then you can choose a padding operation rather than exhaust sequence. If compatibility is checked against the proofing mixture, you can very well do bother pigment padding and proofing in single step. However a thorough scouring and bleaching operation are essential for uniform application of pigment.
The conventional and safe method of water proofing is a two stage process. (1) Application of water proofing emulsion over the fabric using a 2 dips / 2 nips padding mangle - followed by cylinder drying at 110 to 130°C. (2) Fixing treatment of the proof content on the jigger, usually with a concentrated solution of Aluminium or Zirconium Acetate or Formate. After the fixing treatment a thorough rinse on running cold water is essential to remove all the Aluminium salts.
A final drying to completely remove the moisture content of the fabric on a Cylinder Drying Machine essential.
Before packing, allowing the fabric to cool is also essential.
A properly water proofed fabric can easily pass a Cone Test of 24 hours.