piyush -pigment printing process 03

8/6/2019 Piyush -Pigment Printing Process 03

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PIGMENTPRINTING

PROCESS


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In pigment printing, insoluble

pigments, which have no affinity

for the fibre, are fixed on to thetextile with binding agents in the

pattern required.


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` The economic importance of pigments in

printing is substantial since around 1960 these

have become the largest colorant group for textile

prints. More than 50% of all textile prints are printed by

this method, mainly because it is the cheapest and

simplest printing method.


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Electron beam irradiation

method

Conventional thermal printingmethod


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` Accelerated electrons delivered by electron beamaccelerator were used to fix pigment colours,incorporated in curable formulation containing dilutingmonomer and an oligomer, to cotton and polyester

fabrics.` The fabrics were printed with these formulations and

exposed to various doses of electron beam irradiationgenerated from the 1.5 MeV (25 kW) electron beamaccelerator machine.

` The roughness and colour fastness to rubbing,washing, and perspiration of the printed fabrics byelectron beam irradiation, were compared to the samefabrics printed by conventional pigment printingpastes.


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Application of pigment emulsion was done at differentspecified conditions following a pad-dry-cure technique.

For the above purpose, the cotton fabrics is treated with a

solution containing pigment emulsion, binder, acetic acid andspecified catalysts ,was performed separately in two bowlpadding mangle

The impregnated and padded fabrics were dried and finallycured at a temperature of 1400C for 5 minutes Soaping for

fabric samples was performed employing 2 g/l non-ionicdetergent at 600C for 10 minutes .

Finally, the fabric samples were cold washed and dried.


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` Depending on the nature of the fibre on whichprinting is done, suitable dyes or pigments are

selected.` Pigment color can be used for printing on all types

of fibers.

` In case of dyes, reactive, vat & azoic colours areused for cotton, disperse dyes for polyester andacid / basic dyes for wool / silk fiber materials.


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` To make a viscous paste of dyes in water, a

thickener is used.

` The choice of the thickener will depend upon the

class of dye to be printed and style of printing Eg.` Emulsion Thickener, Sodium alginate, Starch,

CMC, etc.


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It helps in obtaining a smooth paste of the dyes

without any lumps.

Example-TRO (Turkey Red Oil), Ethylene oxide

condensates.


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` Formation of foam during print paste preparation

and application is quite common, but should be

avoided.

` Foam may produce speck dyeing.` Antifoaming agents help in reducing foam

generation

Eg. Antifoam NS and Antifoam PJ (non-silicon type)

Antifoam R100 and Antifoam R200 (silicon type)


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` Depending upon the type of dyes used in printing,acid or alkali is used the paste.

` An acid liberating salt is commonly used.

Example,

Ammonium chloride, and Diammonium hydrogenphosphate are a few acid liberating salts used.

` For reactive printing on cotton, sodium carbonate,sodium bicarbonate etc. are used.


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` Oxidizing agents are used in printing with

solubilised vat colors and also in discharge and

resist printing.

` Discharging agents such as Sodium sulphoxylateformaldehyde (Rongalite) are used in the

discharge printing.


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` The function of hygroscopic agents is to take up

sufficient amount of water (moisture) during

steaming to give mobility to the dyes to move intothe fibre.

Eg. Urea and Glycerine.


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` Dispersing agents are necessary in the print paste

to prevent aggregation of the dyestuff in the highly

concentrated pastes.

Example

Diethylene glycol


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` Preservatives are used to prevent the action of

bacteria and fungus to make it dilute.

Eg. Salicylic acid.


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` Binders are used in pigment printing as a thin film

forming polymer.

Eg. Melamine formaldehyde resin.


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External cross linking agent like melamineformaldehyde resin may be added to the paste toimprove wet fastness.

Elasticity and improved adhesion of the film tothe substrate is achieved by cross-linking.

The cross linking reaction must produce covalent

bonds which are insensitive to hydrolysing agents.The reaction should be activated only during fixationand not while the binder and the printing pastes arein storage.


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Pigment - X Parts

Binder - 12 parts

Fixer / Cross linking agent - 1part

DAP / Catalyst LCP - 0.5 1Part

Urea - 2-5 PartsMTO emulsion paste - Remaining

_________

100 Parts


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The ratio of the amount of pigment paste to binder necessary to produce good fastness properties isinfluenced by the fact that even the smallest amount ofpigment(perhaps 1 g pigment paste per kg paste) requiresa layer of binding film at least 5 m thick. Additional

pigment needs about 1.52 times its own mass of bindingsubstance.

For prints on hydrophobic materials (includingpolyester/cotton blends), another 0.51% of external crosslinking agent is added to the paste, depending on thecolour depth and the desired wash fastness.


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` Pigment paste (3040% pigment content) x g

requires

` Binder (approx. 40% solid content) 80 g + 3x/2 g


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Pigments are insolublecoloring matter than can beaffixed on to the fiber with thehelp of some binders.

Pigment printing isconsidered to be one of thesimplest direct style printing,

which can be applied on all

class of fibers irrespective oftheir affinity factor.


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Pigment printing is the most economical printing processand allows maximum output .

Properly produced pigment prints, using selectedproducts, have an unsurpassed fastness to light and goodgeneral fastness properties.

Pigment printing can be applied to all substrates which

are of interest to the printer including glass fibres, PVCand imitation leather. It is extremely well suited for colourresist effects, for example, under azoic and reactive dyes


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piyush -pigment printing process 03

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