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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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THANK YOU