Introduction

This paper presents, demonstrates a complete methodological approach to find out the root causes, solutions of the problems related to pigment printing of textile. Many of the presented problems are common in textile pigment printing therefore; it could be a supportive report for practical printers. Currently, pigment printing accounts to 45-60% of the worldwide textile printing done. Its popularity is due to many reasons, for example


  •   Can be applied on every fiber

  •   Ease in application

  •   Simple machinery

  •   Large color gamut is available

  •   Acceptable fastness properties


Rotary printing machine is the most popular machine for the application of pigment printing; its market share is 55%. The present report therefore only emphasizes the problems which are associated with rotary printing machine. It is common question amongst textile printers, what pigment system should a printer employ? There is no specific answer to this question. The system should be determined by the printer, based on his plant resources, substrate, fastness requirements, end use inventory restraints and cost.


Print system components

There are three basic requirements for print paste system:

  •   Pigments

  •   Binder

  •   Thickener & Auxiliaries


Printing auxiliaries

Dispersing, Levelling & Defoaming Agent: This is used to provide depth and even level printing effect, being added to the printing paste.
Binders Acrylic, Self Thickening for Gold & Flock: These are used to bind the pigment onto the fabric.

Fixers in Pigment Printing: These are used to provide fastness to the print.

Thickeners: These are used to provide viscosity to the printing paste to facilitate required printing effect.
White Inks: These are used to provide printing effect onto the fabric.


SDC (Symptoms, Diagnosis and cure) Concept in textile pigment printing:

In order to overcome/minimize the pigment printing related problems it is essential to first understand the symptoms (problems), diagnose (ascertain the probable cause) & cure (adopting remedial measure). The SDC concept is not new in textile; various reports on it have been published. The reported studies focus on pretreatment, dyeing but, they did not discuss the practical problems of textile pigment printing. Therefore, this report specifically focuses on the problems related to pigment printing. Many of the SDC concepts have been successfully employed in pigment printing.

 

SDC Concept in Print Paste


Symptoms

Diagnosis

Cure

Pigment Agglomeration

1. Uncontrollable Amount of pigment

2. High Viscosity

Reduce the excessive amount of thickener and pigment

Poor definition/Appearance

1. Due to the use of duller pigment selection

2. Lower rheology of the paste

1. Use brightener pigments

2. Select appropriate thickener and its amount

Screen Chocking

1. High Viscosity of print paste

2. Poor Binder stability

3. pH Variation

1. Decrease the amount of thickener

2. Check the quality and strength of binder

3. check the pH of the paste, it should be in alkaline medium

Poor light fastness

1. Low light-fastness pigment

2. Fixer Quantity

1.Select appropriate pigment

2. Use optimize amount of fixer

Dryness of shade

1. Due to use of high amount of pigments

2. High paste viscosity

Reduce the excessive amount of pigments and thickener

Low Tinctorial Value

large particle size of pigment

Use small particle size of pigment

Poor color yield

1. lower viscosity

2. poor color stability


Increase appropriate amount of thickener and binder

Reduction in Viscosity

1. Hardness of water

2. High conductivity of fabric

1. Use soft water

2. Proper washing after pretreatment is required

3. Use stabilize thickener


Flushing

Low viscosity of the paste

1. Increase the amount of thickener

2. Use anti-flushing agents

Color penetration

1.Thin fabric (low weight Fabric)

2.High fabric absorbency

1. Use appropriate amount of thickener with respect to fabric thickness and porosity

2. Mild pretreatment is sufficient for pigment printing


Poor dry crock fastness

Insufficient amount of binder

1. Increase binder

2. Use appropriate amount of pigment

Yellowing of shade

1. Binder chemistry

2. Excessive drying of fabric

1. Use alternate binder

2. Reduce the temperature of dryers

Stiffening of fabric

Excessive amount of binder

1. Optimize the amount of binder

2. Use soft pigment

 

Poor wet crock fastness

Instability in binder film

Add Cross linker (Fixer)

Poor wash fastness

Instability in binder film

1.Increase the amount of binder

2. Add Cross linker (Fixer)

Rigidness in films

High amount of fixers

Optimize the amount of fixers

Immature Cross linking of binder during production run

1.Due to increment in temperature

2. Poor binder stability

3. Low pH of the paste

1. Increase the amount of Liquor ammonia

2. Use suitable binder

3. Increase the amount of urea

Binder film formation on the screen (in dark black and blue shade)

Instable pigment dispersion

Increase the amount of dispersing agent


It is due to the use of excessive or unmeasured amount of pigment, there is some amount of pigment in water. Otherwise over-rated dispersion is formed which cause pigment agglomeration ant it hinders the flow of dispersion or disturb rheology of the print paste. Color paste pH is another important parameter in pigment printing. pH is a number that indicates how alkaline or acid the paste is. Screen printers regard a color paste pH range of 8-9 for pigments as best. At this pH pigment print paste remains wet and possesses a good flow.


A slightly alkaline pH keeps the thickener more stable and prohibits binder film forming. Color paste with pH values below 8, have tendency for drying out quickly and clogging up screens. Also, this may be difficult to clean up. Ammonia water is used to raise the pH. Ammonia evaporates very quickly, but this is why ammonia is so popular with printers. The ammonia in the color paste evaporates away in the print dyer and does not leave residue in the printed color. Alkaline residue in the printed color causes problems with colorfastness. Ammonia is able to provide the needed pH adjustment, but does not help for fastness problems.


Binder gives stiffness to fabric due to the formation of 3D dimension film at the surface of the fabric. Clarian present a new concept of soft pigment in which reactive silicon softener are included in print paste which give soft handle to fabric without disturbing wet crock fastness of the pigment prints.


SDC Concept in Printing Process and Rotary Machine


Registration out

1.Improper screen setting/blanket & screen speed synchronization

Set the screen arrangement, it should be3 synchronized with each other i.e. 90o

2. Use PLC computer

PVA/Blanked Glue line marks

improper washing of blanket

Maintenance of showering for blanket

Screen setting


1. Manpower

2. Mistakes/Miscellaneous factors1

1. Proper Attention

2. Use PLC computer

Blanket marks


2. Ageing of blanket/rough use

Filling by thermoplast

Screen marks


Dents in screen

Change or repair screen

 

Screen touching

Coating loose and color spreading

Proper maintenance & online checking

Loosening of ending


Ending glue expired or insufficient

gluing

Magnet marks

Magnet pressure leaves impression on continuous using

Maintenance of magnet position

Suction pump problems


Electrical/contamination in pumps

Do Calibrate/cleaning the pumps

Synchronizing faults


PLC issue/fabric thickness

Process gently

Rods bending

High magnet pressure

Apply balanced and required magnet pressure

Fluff on screen


Fabric type(especially on flannel)

Proper using water gun and wipes

Dryness of color

1.Improper Magnet pressure

2.Improper Squeegee rod size

1. Increase the magnet pressure at appropriate level

2. Use heavy rod with respect to motif area and definition

Whites marks

Fabric selvedges loose PC

Proper tension/selvedges of fabric should be equalized

Conveyer marks

Improper washing of conveyer/varying speed of conveyer & blanket


Washing and synchronize speed with blanket


Fabric tearing

Extra tension in drying chambers

Maintain the tension through PLC computer

Fabric contaminated

During drying entry of fresh air

Close the dryer during drying

Yellowing of fabric

High temperature during drying

Optimize the temperature

Fluff problem

1. Improper working of air suction

2. Unsigned fabric

3. Insufficient washing of the fabric

1. Maintain the efficiency of air suction

2. Use singed and proper washed fabric

Mis-print

Improper setting of fabric or machine drives

Maintain the efficient setting of M/c drives

Raster effect (Half tone shade)

1.Low Mesh size

2. improper open are of screen


1. Identify the proper and fine mesh size screen

2. Gradual opening of the screen mesh is required with respect the design definition (Need CAD/CAM expertise)


References:

1.      Giesen, V., & Eisenlohr, R. (1994). Pigment printing. Review of Progress in Coloration and Related Topics, 24(1), 26-30.

2.      Majumdar, A., Das, A., Alagirusamy, R., & Kothari, V. K. (Eds.). (2012). Process control in textile manufacturing. Elsevier.

3.      Athalye, A., Shah, J., & Kulkarni, K. (2009). Continuous Dyeing-SDC Concept. Colourage, 56(5), 91-94.

4.      Shamey, R., & Hussein, T. (2005). Critical solutions in the dyeing of cotton textile materials. Textile progress, 37(1-2), 1-84.

5.      Tanveer H. Singeing Fundamentals

6.      Fibre2fashion.com

7.      Shenai, V. A. (1977). Technology of textile processing. Sevak Publications.

8.      Miles, C., & Leslie, W. C. (2010). Textile Printing: Revised Second Edition.


About the Author:

Muhammad Awais Imran and Muhammad Moosa Abdul Rehman are visiting faculty members of Department of Textile Science, Faculty of Engineering, Science & Technology, Indus University, Karachi, Pakistan.