Sunday, September 5, 2010

Dyestuff Selection - manufacturers' suggestion - an important phase in processing

Selecting the proper trichromatic combination of 3 dyes that have almost similar substantivity, exhaustion and fixation properties is very important for getting the best reproducible shade matching.

Nuchem Dyestuffs P Ltd., is making the following suggestions for its customers.


General guidelines:



LIGHT SHADES
MEDIUM SHADES
DARK SHADES
For Good Light fastness and levelness:
Cotfix Yellow CA
Cotfix Red CA
Cotfix Blue CA
Cotfix Amber CA

Cotfix Yellow FN2R
Cotfix Red FN2BL
Cotfix Blue FNR
Cotfix Blue FNG
For all round optimum fastness:
Cotfix Yellow RR
Cotfix Red RR
Cotfix Blue RR

Cotfix Yellow 5GL
Cotfix Yellow F3R
Cotfix Red F3B
Cotfix Blue BB
Cotfix Blue BRN

For Good Light fastness and levelness:
Cotfix Yellow FN2R
Cotfix Red FN2BL
Cotfix Blue FNR
Cotfix Blue FNG

For all round optimum fastness:
Cotfix Yellow RGB
Cotfix Red RGB
Cotfix Blue RGB
Cotfix Navy RGB
Cotfix Caramine RGB

Cotfix Yellow NL-2R
Cotfix Red NL-5B
Cotfix Blue NL-BR
Cotfix Navy NL-R


Dark Shades:
Cotfix Yellow RGB
Cotfix Red RGB
Cotfix Blue RGB
Cotfix Navy RGB
Cotfix Caramine RGB
Cotfix Ultra Yellow RGB
Cotfix Ultra Red RGB

Cotfix Yellow D
Cotfix Red D
Cotfix Navy DB
Cotfix Orange D
Cotfix Deep Red DB
Cotfix Dark Blue DB




This guideline is only a general thumb rule and one should not come to a conclusion that this is the ultimate criteria. The dyer, based on his final requirement or end use of the dyed material, has to select proper group of dyestuff.

CA, FN and NL series would meet the wide range of fastness requirements of the industry.

RGB and Ultra RGB series are most suitable for medium and dark shades, where one would expect no metamerism.

W series are exceptionally suitable for wide range of dark shades, where economy is of prime importance. With series generally one can dye uniforms like dark browns, Olives and Dull blues.

D series posses exceptionally all sound fastness parameters and are economical too for dyeing dark and very dark shades.

HF series produce exceptionally bright shades and possess very high tinctorial values, most suitable for dyeing and printing, exhaust and CPB applications.

This classification is further elaborated as below:
1.     Lemon Yellow
2.     Yellow, Golden Yellow
3.     Orange, Scarlet
4.     Red
5.     Wine, Maroon
6.     Violet
7.     Blue, Royal
8.     Turquoise, Bright Green
9.     Navy Blue, Black
10.  Beige, Light Blue, Grey
11.  Brown
12.  Dark Green, Olive
 
Lemon Yellow
Cotfix Yellow 5GL
Cotfix Yellow ME4GL
Cotfix Yellow F4G


Yellow, Golden Yellow
Cotfix Golden Yellow F3R
Cotfix Red F3B
Cotfix Blue BB
Cotfix Yellow GR
Cotfix Orange 2R
Cotfix Orange 3R
Cotfix Orange ME2RL 

Orange, Scarlet
Cotfix Orange 3R
Cotfix Orange ME2RL
Cotfix  Oange 2R
Cotfix Yellow F4GL
Cotfix Yellow GR
Cotfix G.Yellow RNL 150%
Cotfix Red F3B
Cotfix Navy Blue BFN

 Red
Cotfix Yellow GR
Cotfix G.Yellow RNL
Cotfix Orange 3R
Cotfix Orange 2R
Cotfix Orange D
Cotfix Deep Red DB
Cotfix Red D
Cotfix Scarlet HF-3G
Cotfix Orange HF-2GL
Cotfix Blue BB

Wine, Maroon
Cotfix Yellow GR
Cotfix Yellow RNL-150%
Cotfix Deep Red DB
Cotfix Caramine RGB
Cotfix Ultra Red RGB
Cotfix Navy Blue RGB
Cotfix Navy Blue BFN
Cotfix Blue R SPL.

 Violet
Cotfix Golden Yellow F3R
Cotfix Orange ME2RL
Cotfix Red ME6BL
Cotfix Red ME4BL
Cotfix Violet 5R
Cotfix Navy Blue R SPL
Cotfix Navy Blue BFN
Cotfix Blue BRN

Blue, Royal
Cotfix Blue BRN
Cotfix Navy Blue BFN
Cotfix Golden Yellow R 150
Cotfix T/Q Blue H2GP, G
Cotfix Blue R spl
Cotfix Blue BB

Turquoise, Bright Green
Cotfix Yellow F4G
Cotfix Golden Yellow F3R
Cotfix Yellow ME4GL
Cotfix Blue R SPL
Cotfix T/Q Blue H2GP
Cotfix Blue BB

Navy, Black
Cotfix Golden Yellow R 150
Cotfix Red ME6BL
Cotfix Red RGB
Cotfix Red ME4BL
Cotfix Navy Blue R spl
Cotfix Navy Blue BFN
Cotfix Black ECO
Cotfix Black WNN
Cotfix Supra Black G
Cotfix Black B 133%

Beige, Light Blue, Grey
Cotfix Blue BRN
Cotfix Yellow RR
Cotfix Red RR
Cotfix Blue RR
Cotfix Yellow CA
Cotfix Red CA
Cotfix Blue CA
Cotfix Red HF-G

Brown
Cotfix Golden Yellow WR
Cotfix Red WB
Cotfix Navy Blue WB
Cotfix Orange W3R
Cotfix Dark Blue WR
Cotfix Yellow RGB
Cotfix Red RGB
Cotfix Blue RGB
Cotfix Navy RGB
Cotfix Caramine RGB
Cotfix Ultra Yellow RGB
Cotfix Ultra Red RGB
Cotfix Yellow D
Cotfix Red D
Cotfix Navy DB
Cotfix Orange D
Cotfix Deep Red DB
Cotfix Dark Blue DB

 Dark Green, Olive
Cotfix yellow RGB
Cotfix Red RGB
Cotfix Blue RGB
Cotfix Navy RGB
Cotfix Yellow D 
Cotfix Red D
Cotfix Navy DB
Cotfix Orange D
Cotfix Deep Red DB
Cotfix Dark Blue DB



Thursday, September 2, 2010

Discharge Printing/Dyeing - Dischargeable dyes - How to select dyestuffs for dischrge print?


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

    * Hypo Chlorites are also used for specific articles

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.


 

Thursday, August 5, 2010

Cotfix Bifuntional Dyestuffs - for better exhaustion - most suitable dyes for knits.

Cotfix Bi-functional Dyes


The poor exhaustion and fixation properties of Vinylsulphone dyes that lead to lot of dyestuff wastage have given birth to the bi-functional dyes with medium exhaustion and better fixation properties.


Bifunctional dyes have filled a big vacuum of various hues of bright shades, which were not possible with vinyl sulphone type. The dyes were conventional Dichlorotriazine type, with the end condensation of ß-sulphato ethyl sulphone to have different type of reactive group in a single molecule. Being a dual reactive, the primary mode of fixation is from vinyl sulphone group and the dyeing temperature is same as vinyl-sulphone, which enables good, inter compatibility in between the two classes.

Methods of dyeing:




These bifunctional dyes are most suitable for exhaust dyeing and Pad Batch and continuous. Can be freely mixed in combinations with Vinyl Sulphone dyes.

Cotfix High Exhaust (HE) dyes - most suitable for garment dyeing!

Cotfix HE Dyes



Cotfix HE dyes are basically bis monochlorotriazine reactive dyes with low reactivity and high substantivity. These dyes are characterized by high but slow exhaustion and high fixation values. Washing off of dyed goods is easier due to higher fixation.




Due to the high fixation (85% and more) pollution problems are also minimized since the drained liquor contains minimal of unfixed dyes.


Characteristics of Cotfix HE dyes:



• Better reproducibility and hence batch to batch variation is minimized.


• High tinctorial value due to excellent build up properties


• Eco friendly due to higher fixation values.


• Better fastness properties.


• Wide range of application since it is suitable for all types of cellulosic materials like yarn, fiber, piece dyeing and garments.

Cotfix HE dyes are most suitable for garment dyeing, because of their high exhaustion and fixation properties at higher temperature (80°C) that facilitate uniform and level dyeing of stitched garments on all its parts like collar, scuffs and stitched yarn. Moreover because these dyes posses outstanding fastness characters when compared to other class of reactive dyes.


These dyes are most suitable for exhaust dyeing and in particular in that machinery where you can easily achieve and maintain the 80°C on the fabric.

Cotfix Hot Brands - Printing Dyes

Our cyanuric chloride based, Cotfix 'H' brand dyes forms various chemical linkage with hydroxyl groups of cellulose. These dyes are low substantive and high fixation dyes most suitable for dyeing and printing of cotton, viscose, cuprammonium rayon and natural silk. The dyeing temperature is 80°C.


METHOD OF DYEING: By Exhaust Dyeing:
Take well pre-scoured fabric and ensure that the pH of the fabric is 7, if require adjust pH by adding Acetic Acid. Take soft water for dyeing, if the water is hard, add sequestering agent to achieve best result.
Set the dye bath at 50ºC and add pre-dissolve dye in two portion and run for 10 min.
Add 5 gms./lit. Common salt for deep shade (2.5 gms./lit. for pale shade) and run for 10 min. start raising temperature to 80ºC - 85ºC in 30 min.
During raising temperature, 20 gms./lit. Common salt (10 gms./lit. for pale shade) after first 10 min. and add 25 gms./lit. Common salt (8 - 10 gms./lit. for pale shade) after another 10 min. and continue dye for 15 min. after reaching the temperature to 80ºC - 85ºC.
Add Alkali slowly in 15 min. and continue dyeing for further 45 - 75 min.


SALT AND ALKALI REQUIREMENTS FOR REACTIVE HOT DYES
COTFIX – H BRAND DYES IN PRINTING
In conventional one-step printing with reactive dyes, urea is used to increase solubility of the dyestuffs and to improve dyestuff migration from the printing paste to the textile fiber.
Minimization or even substitution of urea is possible in the one-step method by controlled addition of moisture.
Another option is the two-step printing method, involving the following steps:
• Padding of the printing paste
• Intermediate drying
• Padding with alkaline solution of fixating agents (especially water-glass)
• Fixation by means of overheated steam
• Washing steps (to remove thickeners and improve fastness properties).
The process is carried out without urea.
A typical recipe for the printing paste is given below:
Thickening stock solution:
Fixation is carried out by means of overheated steam (90 °C to 125 °C).