Discharge Printing
Pre-Conditions for Fabrics to Be Printed
There are 3 basic conditions a fabric must possess to be considered for today’s Unit Print or T-Shirt Print market. These are:
1. Uniformity in Print Bottom.
2. Dis-chargeable to Sulfite Based Discharging agents.
3. Dyed Bottom Compatibility with Print Vehicle.
The first point includes such considerations as uniform washing and scouring, the use of "print friendly" add-on (softeners, wetting agents, resins, etc.), and uniform absorbency.
The second point describes the pre-dying step and the fact that dye selection for shade matching must include the behavior of the dyed fabric after finishing. The print vehicle at use in the majority of the Digital Thermal Printers contains solvents and emulsifiers which will have an affinity of the dyes on the fabric. The Dyeing process for reactive dyes includes a washing step to remove the excess dye. However, subsequent finishing with acid products can cause certain reactive dyes to release some of the fixed dye and this would then "Bloom" into the print due to the heat of curing and fixing of the print. The Reactive dyes are not affected by the acid treatment and would not be subject to breakdown in this manner.
The other dye classes for cotton such as direct, sulfur, vats and pigment are more prone to exhibit a tendency to bloom than the reactive dyes. In the case of Polyester or Polyester/Cotton blended fabrics the polyester dye must be dyed without carrier and given a good reductive scour or some disperse dye remains on the cotton and all disperse dyes are soluble to some extent in the solvent of the print vehicle.
The phenomenon of dye transport in the fiber is a reversible physical/chemical reaction. This means that even with a good dying procedure, dye will return to the surface of the fiber and be accessible to the print vehicle after any heat processing (drying, etc.). The fact that the dying process is not a guarantee of a print-friendly mandates the selection of dyes based on solubility in the print vehicle. Some of this information is known but testing of existing shades should be done. The dyeing for testing should always be made on the Polyester/Cotton fabric in the absence of the cotton dye but the fabric should be subjected to the Cotton dye procedure.
The third point is dis-chargeability of the Cotton dye. The most popular and used dyes for the cotton fabrics are the reactive dyes. Not all reactive dyes are dis-chargeable completely and there must be a selection of dyes used to match shades that are to be marketed as dis-chargeable. As a group, the fiber reactive dyes offer the widest selection for this criterion.
COTFIX DYES: DISCHARGE and RESIST
The terminology used to describe these two processes is sometimes confusing to the Textile Industry. The first order of business, then, has to be a definition and description of these two processes.
R E S I S T
Resist is the term used to describe the Prevention of the Dyeing Process brought about by the application to the fabric of a Mechanical, Physical or Chemical Substance to prevent Dye Access to the Fabric. This done in such a manner that a Pattern is realized in the Dyed Goods.
D I S C H A R G E
Discharge is the term used to describe the displacement of a dyed shade by a Chemical Process in such a manner that a pattern is imparted to the dyed fabric.
· The fabric is Dyed First.
· The Discharge Agent is applied to the fabric normally by Printing.
· The fabric is processed to get the discharge.
· Then the fabric is washed to remove the Byproducts of Discharge.
· If color is added to the Discharge Agent, this is the Illuminating or Discharge Color.
· If No color is added to the Discharge Agent, the result is a White Discharge.
The most common Discharge Agents are chemicals based on Sufoxylate Formaldehyde Chemistry.
DISCHARGE AGENTS
The most common Discharge Agents are chemicals based on
· Sufoxylate Formaldehyde Chemistry.
· Sodium Sulfoxylate Formaldehyde * Vat Discharge
· Zinc Sulfoxylate Formaldehyde * Pigment & Acid
· Sodium Hydro Sulfite
· Potassium Sulfoxylate Formaldehyde
· Thiourea Dioxide Compounds
Cleavage products that must be removed by washing to get to the final shade are left on the fabric. These may be amides that are easily saponified and removed by washing. They may or may not be colored themselves.
COTFIX DYES FOR DISCHARGE PRINT: GROUND SHADE PRODUCTION
The following COTFIX Dyes are dis-chargeable by either the alkaline or the acid Sulfoxylate Formaldehyde Procedures.
The maximum concentration of dye used to make a shade match affects the discharge obtainable. The maximum recommended amounts of each Cotfix Dye are included.
This list should be used for all dyeing that requires that the shade be dischargeable.
The most trouble free dyes for this procedure are marked by Good & Fair.
Cotfix Dye | Discharge | Max.Conc | REMARKS |
Br. Yellow 4GL | Yes | 50 gpl | Good |
Br.Yellow GL | Yes | 50 gpl | Fair |
Golden Yellow RNL | Yes | 50 gpl | Good |
Br.Orange 3R | Yes | 50 gpl | Good |
Br.Red F3B | Yes | 30 gpl | Fair |
Br.Red 5B | Yes | 50 gpl | Good |
Br.Violet 5R | Yes | 30 gpl | Fair |
Blue BB | Yes | 30 gpl | Fair |
T.Blue G, H2GP, H5G | Yes | 15 gpl | Fair |
Navy RGB | Yes | 60 gpl | Good |
Black B | Yes | 80 gpl | Good |
Black RGB | Yes | 80 gpl | Good |
All Turquoise Dyes are very difficult to discharge and should not be recommended for this procedure. The exception is in cases where Turquoise is needed for Green shades. Shade discharge is dependent on the dyestuff used and NOT the Technique used to make the dyeing.
Cotfix Dyes:
Selection for Dischargeable Shade Production
Black
Cotfix Black B
Cotfix Black NF
Cotfix Deep Black RGB
Cotfix Navy R-GB
Cotfix Golden Yellow RNL
Cotfix Brill. Red F3B
Navy
Cotfix Black B
Cotfix Navy Blue R-GB
Cotfix Brill. Red F3B
Cotfix Orange 3R
Dark Green
Cotfix Orange 3R
Cotfix Navy RGB
Cotfix Brill. Blue BB
Blue
Cotfix Brill. Blue BB
Cotfix Navy RGB
Royal
Cotfix Brill. Blue BB
Cotfix Brill. Red F3B
Cotfix Brill. Violet 5R
Turquoise
Cotfix Turquoise G-A Maximum 1%: 10 g/l
Cotfix Brill. Blue BB
Cotfix Navy RGB
Bright Green
Cotfix Brill. Yellow 4GL
Cotfix Brill. Blue BB
Teal
Cotfix Brill. Yellow 4GL
Cotfix Brill. Blue BB
Cotfix Navy RGB
Bright Red
Cotfix Brill. Red F3B
Cotfix Golden Yellow RNL
Red
Cotfix Brill. Red F3B
Wine
Cotfix Brill. Violet 5R
Cotfix Brill. Blue BB
Cotfix Brill. Red F3B
Maroon
Cotfix Brill. Violet 5R
Cotfix Brill. Orange 3R
Cotfix Brill. Red F3B
Violet
Cotfix Brill. Violet 5R
Cotfix Brill. Red F3B
Cotfix Brill. Blue BB New
Scarlet
Cotfix Brill. Red F3B
Cotfix Brill. Yellow GL
Orange
Cotfix Brill. Orange 3R
Golden Yellow
Cotfix Golden Yellow RNL
Lemon Yellow
Cotfix Brill. Yellow 4GL
Note that the bright royal shades and the shades requiring the use of a turquoise dye are difficult to match with the available dyes.
The use, even very sparingly, of both the Cotfix Turquoise G and the Cotfix Brilliant Blue R Special is not recommended if a consistently dis-chargeable bottom is desired. It is customary for these shades to be matched either for discharge but slightly dull or for optimum brightness but not dis-chargeable.
Any shade can be matched using the list of dischargeable dyes and a reasonable result will be obtained. The listing by shade groups insures the most reliable results from a performance view point.
This listing and grouping is far from a complete dictionary for dyeing and discharge but is our experience. The use of dischargeable direct dyes would be similar in shade grouping but the resultant problems with the dye diffusion into the solvent in the print vehicle would be greatly increased.
No comments:
Post a Comment