This article introduces you to textile printing and explains the print paste ingredients used in textile printing.
In the process of printing, color designs are developed on fabrics by printing with dyes and pigments in paste form with specially designed machines. Printing is used to apply colors only in localized areas according to the design pattern. Printed fabrics usually have clear-cut edges in the printed portions on the face of the fabric. Printing allows flexibility in creating a variety of designs and enhance the aesthetic value of fabric.
Let us now examine the differences between dyeing and printing
The only mono-color application can be done
Dyes are applied in liquid form
Salt is required
Temperature is used for better penetration
Water plays an important role
Percentage of shade is calculated on the weight of the material
Time is allowed for better penetration
The half bleached fabric is used for dyeing
The fabric is handled either in open width or in rope form
The fabric may be in wet/dry condition during dyeing
Uniform color application on both the faces of the fabric
Machinery requirement is comparatively simple (tanks, winches, jiggers, soft flow, padding Mangal)
Cost of dying per meter is lower
The process of dyeing consumes more time
Dyeing consumes more water
Mono or multicolor applications are possible.
Dyes are applied with paste.
Salt is not required
Temperature is not used.
Thickening agents play an important role.
Percentage of shade is calculated on the weight of the paste.
Time is not required since the color is applied only on the surface of the fabric only
The full bleached fabric is used for printing
The fabric is handled only in open width form.
The fabric is to be in dry condition only during printing.
Due to single face printing, the printed face will be darker and other phases will be paler.
Machine requirement is complex by way of design, screen preparation, printing machines and after process machinery
Cost of printing per meter is higher
The process of printing consumes short time
Printing consumes less water
For printing, the following are the general requirements of fabrics
The fabric should be stitched with proper phase on top and uniform width
Shearing and cropping treatment is given to remove loose threads
Desizing is necessary for proper penetration of the print paste
Singeing removes Hairy fibers, to enable uniform adhesion of printing paste and sharpness
Scouring gives better dye absorption
Mercerization is given for cotton fabric and heat setting for synthetic fabrics
Full bleaching is suitable for whiter background
The fabric should be thoroughly dried
It should be free from creases and should be free from weft bowing
Ingredients of print paste
Thickness and auxiliaries used in textile printing
- Dyestuff or Pigments
- Thickness and Auxiliaries used in textile printing
- Wetting agents
- Dispersing agents
- Anti-foaming agents
- Fixation accelerator
- Hydroscopic agents
- Oxidizing agents
- Reducing agents
Dyestuff or Pigment
Dyestuff or pigment is used as coloring matter depending on the nature of the fiber. Lumps are broken using a wetting agent and smooth paste is obtained. Dyestuff or pigment is selected on the basis of cost, fastness properties, and requirement of shade.
Thickness and Auxiliaries
Thickness and auxiliaries used in textile printing prevent the spreading of the color on the cloth by capillary action. The choice of thickener depends upon the class of dye to be printed and styles of printing.
Example CMC, Indalca, Traceganth, British gum, sodium alginate, emulsion thickener etc.
Wetting agents are used to obtain a smooth paste of the dyestuff without formation of any lumps. Lumps if allowed to remain to get deposited on the cloth during printing and produce dark spots. For insoluble dyestuffs like vats and naphthols, wetting agents are used to facilitate wetting of the dyestuff. For direct, acid, basic and reactive dyes which are water-soluble, a wetting agent is normally not required.
Dispersing agents are used to prevent precipitation of dye particles as the concentration of the dyestuff in the printing paste is high.
Example – di-ethylene glycol, Thio-di-glycol, sodium benzyl sulphanilate.
Anti-Forming Agents are used to reducing frothing in the printing paste. Dyestuffs have a tendency to froth during color preparation and printing because of the presence of wetting agents and continuous agitation by the printing roller and brush finisher.
Due to Frothing
The paste overflows on the floor or on to other color boxes. The print also becomes spiky and lighter in shade.
Fixation accelerators are used to improve dyestuff fixation in printing as well as to shorten fixation time.
They are also effective in preventing fixation unevenness that may be caused by fluctuation of conditions for dyestuff fixation, such as temperature time and humidity etc.
Examples – P-phenyl phenol is applied for polyester
Thiourea is applied for polyamide
Resorcinol is applied for polyamide, cotton and acrylic fibers.
Hydroscopic agents are used to taking up a sufficient amount of water during steaming. This gives mobility to the dye molecules to enable them to transfer it to the fiber.
Examples – Urea, Glycerine, Di-ethylene, Glycol
Oxidizing agents are required for printing certain classes of dyes and also in discharge and resist printing. Most commonly used oxidizing agents are chlorates, chromates, and dichromates, nitrates and nitrites of sodium, potassium Ferrocyanide.
Reducing agents are required for discharge and resist printing as discharge chemicals,
Sodium Sulphoxylate Formaldehyde, Zinc Sulphoxylate Formaldehyde, Potassium Sulphite, Ferrous Sulphate, Stannous Chloride, Thio Urea etc.
Essential properties of thickeners for printing
To meet all the requirements for printing more than two selected thickness in combinations are used. For better workability, the following are considered while choosing the thickener.
Quick-Drying – it should have desired viscosity, flow, ability to weight and good adhesion to the substrate. It should not affect the shade of the dyes used. The storage stability of thickener should be good. It should have low foaming property. It should be compatible and inert to dyes and other ingredients of the printing paste. It should have good elasticity during squeeze action. It should have good film strength and non-crocking after drying. It should have thermal stability at a higher temperature. It should be easily washed out. Should be available at a reasonable price and should be biodegradable and eco-friendly.
Advantages of Synthetic Thickness
- Synthetic thickness is derived from suitable vinyl compounds.
- They provide finer designs with fine screen cage and roller engravings.
- It is cheaper and ecologically beneficial.
- Enhance dye fixation and helps to achieve greater depth of color.
- Require no special storage requirements
- Using synthetic thickeners when used without solvent produces a very high quality of pigment prints.
- They are free from hardening, browning during high-temperature fixation.
For industrial textile printing, three different printing techniques are the most widely used: flat screen printing, rotary screen printing, and digital textile printing. The textile market is a major industry, and the printing of textiles has been changing over the years. In this evolving segment of the market, Splashjet has developed innovative digital textile printing ink.