Polyester Printing

Printing of Polyester by Direct Style

Principle

           

Polyester fabric can be printed with disperse dye as per the dyeing procedure.

ð  Printing of Polyester is differs from dyeing as below:-

·         Various disperse dyes can be used in combination with each other.

·         No blocking effect occurs.

·         Colour build up is better.

·         Fastness to water, sea water, perspiration and chlorine is essential.

Ingredients

(1)   Dyes:-

·         Disperse dyes are the most suitable for printing of polyester fibre materials.

·         Selected dyes with good steaming and thermofixation fastness are suitable.

(2)   Thickeners:-

·         Thickeners having high solid content are best suitable for this printing.

·         Natural gums, starch ethers and modified locust bean gums (gum indalca) are the best commonly used thickeners.

·         Alginate thickener is less suitable since it imparts the brightness of the print with disperse dyes especially in the thermofixation.

·         Prints with Carboxy methyl cellulose are normally level and sharp and have good yield.

·         Starch ethers have not satisfactory wash off properties.

·         British gum produces dull prints.

·         Emulsion thickeners increase levelness and penetration of the dye in the fibre.

(3)   Dispersing agent:-

·         Disperse dyes are insoluble in water, and should be kept in dispersion form.

·         Therefore, paste should contain dispersing agent, like Setamol WS

(4)   Wetting agent or Solvent:-

·         For pasting of disperse dye, due to its insolubility in water, the dye should be wetted by wetting agent, eg. TRO and dyes are solubilising in dispersion form using solvent like ethylene glycol.

(5)   Acid:-

·         Since most of the disperse dyes are sensitive to alkali, medium of paste is kept acidic using organic acid. A small amount of citric acid or tartaric acid is added to bring down the pH about 6.0

(6)   Oxidising agent:-

·         Sodium chlorate is used to protect the brightness of the dye against any possible reduction of the dye under the prolonged steaming conditions.

(7)    Acid Liberating agent:-

·         The print paste should remain acidic during steaming, so Ammonium sulphate is used as an acid liberating agent. Carrier is also used to improve colour yield.

Procedure

·         The printing paste is prepared as follows:-

      50  parts    Disperse dye

                      10 – 20 parts     Dispersing agent (setamol WS)

                      10 – 20 parts     TRO

                      10 – 20 parts     Citric acid or (1 – 2 parts Tartaric acid)

                            160 parts    Water

                              10  parts    Ethylene Glycol

                            710  parts    Thickener

                                5 parts    Ammonium sulphate

                                5  parts    Sodium Chlorate

                          1000  parts

·         After printing, fabric is dried and fixation is done by three different methods.

(1)   Steaming:- Printed fabric is steamed for 30 minutes at 128ºC (30 psi pressure). This system produces full colour yield and bright prints. This is a batch wise process and needs more labour.

(2)   High temperature steaming (curing):- Printed fabric is cured at 180ºC for 1 – 2 minutes. This is a continuous process and gives full colour yield and bright prints.

(3)   Thermofixation:- Printed fabric is thermofixed at 210ºC for 30 seconds. This is a continuous process of fixation, and carried out on stenter or a backing machine. In this method, the dyes are selected on the bases of their sublimation fastness properties. 

·         After fixation, fabric is rinsed with cold water and hot water, reduction cleared (at 40 – 50ºC for 15minutes) in following bath:-

20 parts           Sodium hydrosulphite

30 parts           Sodium hydroxide

10 parts           Polyvinyl pyrrolidone (stripping assistant)

                                            1000 parts

           

·         Finally, the cloth is rinsed, soaped at the boil, washed and dried.