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Chemical Processing Printing

Styles of printing; Printing thickeners including synthetic thickeners; Printing auxiliaries; Printing of cotton with reactive dyes, wool, silk, nylon with acid and metal complex dyes, Printing of polyester with disperse dyes; Pigment printing; Resist and discharge printing of cotton, silk and polyester; Transfer printing of polyester; Inkjet printing.

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Chemical Processing Printing

  1. 1. CHEMICAL PROCESSING PRINTING for more visit :- https://textilerun.blogspot.com
  2. 2. Objectives • The main objective in printing is the production of attractive designs with well defined boundaries made by the artistic arrangement of a motif or motifs in one or more colours • Dyes and pigments are applied locally or discontinuously to produce the various designs • Localized dyeing • The forces which operate between dye and fibre are the same in dyeing and printing for more visit :- https://textilerun.blogspot.com
  3. 3. Ingredients The essential ingredients of printing paste are selected from the following: 1. Dyestuffs, pigments or dyestuff formers 2. Wetting agents 3. Solvents, solution aids, dispersing agents and humectants 4. Thickeners 5. Defoaming agents 6. Oxidizing agents and reducing agents 7. Catalysts and oxygen carriers 8. Acid and alkalies 9. Carriers and swelling agents 10. Miscellaneous agents for more visit :- https://textilerun.blogspot.com
  4. 4. Styles of Printing A coloured design on a white or differently coloured background can be produced on fabrics by using different styles of printing like direct style, discharge style and resist style Printing Style Direct Discharge Resist White Coloured White Coloured formorevisit:- https://textilerun.blogspot.com
  5. 5. Discharge style • Azoic Dyeing • Print fabric with gum and Rongalite C (H liberation) Steam for more visit :- https://textilerun.blogspot.com
  6. 6. Resist Printing •Dyes that could not be discharged can be resisted •Print Citric acid with thickener ̶ Dry •Pad with with reactive dye liquor •Steam •Soap Citric acid for more visit :- https://textilerun.blogspot.com
  7. 7. After Printing Operations • Drying • Fixation Steaming Curing • Washing-off for more visit :- https://textilerun.blogspot.com
  8. 8. Pigment Printing Pigment printing Printing with dyes No affinity to fibre. Affinity to fibre. Insoluble in water. Water soluble or can be made water soluble Need binder for fixation onto fibre Held on fibre by dye-fibre interactive forces. No washing require Washing require for more visit :- https://textilerun.blogspot.com
  9. 9. Print Paste • Dye--- 5 parts • Wetting agent- 1 part • Glycerine- 5 parts • Thickener paste– 69parts • Water- 20 parts for more visit :- https://textilerun.blogspot.com
  10. 10. for more visit :- https://textilerun.blogspot.com
  11. 11. DYEING and PRINTING •Printing is controlled form of localised dyeing •Same mechanisms of dye fixation apply in both dyeing and printing •In principle dyes used to produce dyed fabric could be used to print that fabric •However care is needed in selection of dyes •In printing dye solubility is more critical for more visit :- https://textilerun.blogspot.com
  12. 12. •The amount of water in the print paste is severely limited •And at the fixation stage, the dye must be re- dissolved in a small volume of condensed steam •The dye must diffuse through the thickener film before adsorption on, and diffusion into, the fibre •Slow diffusing dyes will need longer fixation (steaming, ?) times •Low mol. Wt. dyes are preferable (if fastness is not compromised) for more visit :- https://textilerun.blogspot.com
  13. 13. General procedure for printing Preparation of Printing paste Printing Drying Fixation (Steaming/dry heat etc.) After-treatments formorevisit:- https://textilerun.blogspot.com
  14. 14. General Nomenclature • Thickener paste---Only thickener prepared as per solid content required to build final viscosity • Stock paste--- Except dye/pigment all ingredients • Print Paste– Final paste for printing including dye/pigment for more visit :- https://textilerun.blogspot.com
  15. 15. DIRECT PRINT COLORATION of cellulosic fabrics- 1.Direct dyes • Printing paste generally contains dye, wetting agent, solvent, hygroscopic agent and weak alkali • Thickener – preferably starch or british gum (Dextrin) • Typical recipe for Print Paste (1Kg paste) Direct dye – 5-20gm Water – 385-310gm Glycerine– 50gm Trisodium phosphate- 10-20gm Thickener- 500gm • After printing fabric is dried and steamed for about 1hr in cottage steamer (batch process) or 5-10mins in continuous steamer followed by light soaping and the washing • The washing fastness of the prints may be improved by after treatment with cationic dye fixing agent formorevisit:- https://textilerun.blogspot.com
  16. 16. DIRECT PRINT COLORATION REACTIVE DYES Printing by the all-in method Stock Paste Print Paste Dye—X gm Water-- Stock paste— Maintain viscosity---? for more visit :- https://textilerun.blogspot.com
  17. 17. A typical print paste is prepared by sprinkling the required amount of reactive dye into a stock paste or Adding the pre-dissolved dye in a small volume of hot water • Alginates are the only suitable natural thickeners • Synthetic thickeners with anionic charges Poly (acrylic acid) are also good. Washing-off is difficult • Emulsion thickening can also be used
  18. 18. ALKALI •Alkali is needed to ionise accessible cellulose hydroxyl groups and fix the dye •Depend on reactivity/stability of dye •Sodium bicarbonate has been the preferred alkali •It is cheap and gives sufficient print paste stability with most reactive dyes •For high stability dyes, sodium carbonate can be used •For dyes of high reactivity the concentration of bicarbonate may be reduced for more visit :- https://textilerun.blogspot.com
  19. 19. FIXATION • It is important to ensure that the fixation (maximum) and hydrolysis (Negligible) proceed to completion • The choice of dyes is therefore determined by the fixation equipment available • The stability of the dye–fibre bond under hot alkaline conditions is important • Print paste stability and dye reactivity are related • The actual level of fixation is also important for more visit :- https://textilerun.blogspot.com
  20. 20. • The fixation of most reactive dyes is effected by saturated steam at 100–103 °C within 10 min. • The most highly reactive dyes may require only 1 min • Faster fixation is obtained in superheated steam at temperatures of 130 -160 °C, 30 to 60 s • higher fixation levels can be achieved by having two reactive centres into each dye molecule FIXATION for more visit :- https://textilerun.blogspot.com
  21. 21. ROLE OF UREA • Solubilizing aid for reactive dye • When cold printed fabric is entered into saturated/superheated steam, water condenses on to the fibres • But loss of this water follows • Urea holds some of the water very strongly • The eutectic mixture of urea and water provides the solvent required for the dye–fibre reaction to occur • In the absence of urea colour yields are low, unless fixation can take place during drying for more visit :- https://textilerun.blogspot.com
  22. 22. FIXATION IN HOT AIR •Because reactive dyes are typically of small molecular size and low affinity, fixation can be achieved even in hot, dry air. •Urea at concentrations of 150–200 g/kg of paste is essential •Times of 1–3 min are required at temperatures of 180–160 °C. for more visit :- https://textilerun.blogspot.com
  23. 23. PRINTING BY TWO-STAGE METHODS The composition of a typical stock paste Recipe for wet fixationprocesses Print Paste Dye—X gm Water-- Stock paste— Maintain viscosity---?
  24. 24. • The alkaline solution can be applied on a vertical two-bowl padder at high speed or, if lower speeds are used, on a horizontal two-bowl or nip pad. • The steam temperature is preferably at least 130 °C, for a steaming time of 30–50 s. • Washing equipment is usually coupled with the steamer for immediate removal of unfixed dye. PRINTING BY TWO-STAGE METHODS Nip padding for more visit :- https://textilerun.blogspot.com
  25. 25. “ALKALI SHOCK” • Alkali-shock method to fix the reactive dyes in which printed fabric goes through into hot alkali solution (100–103°C) to initiate fixation. • For dyes of high reactivity, steaming is not required • A passage in open width for 10–20 s through the alkaline liquor at followed by immediate washing. • Elevation of the boiling point – bath temperature can go upto 105oC (which chemical should be added?) • bleached fabric → printing → alkali-shock → rinsing → soaping → rinsing → drying. for more visit :- https://textilerun.blogspot.com
  26. 26. • Longer fixation times, lower (room) temperature • Sodium silicate liquors are used by padding • Wet pick up is 70–80% • Fixation takes place slowly ( 6–12 h ) during batching for more visit :- https://textilerun.blogspot.com
  27. 27. •Washing is a critical step (more than that for dyeing) •A perfectly fine printed fabric can be spoiled at washing stage •Selection of dyes is important •High substantivity dyes – problem in removal during washing for more visit :- https://textilerun.blogspot.com
  28. 28. •The first step is a thorough rinsing with cold water •Alkali, electrolyte and most of the thickener and surface dye (hydrolysed) should be removed in the first stage •High-temperature washing (~boil) is then done remove hydrolysed dye from inside the fibres •Finally a cold rinse is given for more visit :- https://textilerun.blogspot.com
  29. 29. Direct Print Coloration of Polyester– Disperse Dyes• Disperse dyes are most suitable • Thickener is important. It should adhere to fabric and produce elastic film. • Natural gums, starch ethers and Indalca gum is commonly used. Combination of thickeners can also be used 1. For high pressure steaming Disperse dye- 50-100gm Water- 50-104gm Thickener paste – 894-790gm Ammonium sulphate- 5gm Sodium chlorate/ R-salt– 1gm • After printing and drying, the fabric may be steamed for 30 min at 25psi pressure (125- 1300C). • Alternatively hot air fixation may be carried out at 180-2000C for 1min. • The fabric is then rinsed with hot water and reduction cleared using 2gpl NaOH and 2gpl hydros 2. For thermal Fixation Disperse dye- 50-100gm Water- 50-100gm Carrier – 0-20gm Thickener paste- 900-780gm
  30. 30. DISCHARGE & RESIST STYLES for more visit :- https://textilerun.blogspot.com
  31. 31. DISCHARGE AND RESIST STYLES • Involve two stages as compared to direct printing, which is a single stage process • In discharge style, dyeing of the fabric is followed by printing • In Resist, it is the other way round (Printing followed by dyeing) for more visit :- https://textilerun.blogspot.com
  32. 32. DISCHRAGE PRINTS for more visit :- https://textilerun.blogspot.com
  33. 33. Discharge Style of Printing• In the direct printing style, the final effect is obtained in one operation • In the discharge style, the fabric must first be dyed with dyes that can be destroyed by selected discharging agents (white discharge) • A coloured discharge effect is produced by adding a discharge-resistant (‘illuminating’) dye to the discharge print paste formorevisit:- https://textilerun.blogspot.com
  34. 34. Advantages of Discharge style • Printed materials with large areas of ground color can be produced • Delicate colors and intricate patterns can be reproduced on grounds of any depth • Intricate white patterns lose their crispness if left as unprinted areas in a direct, blotch print • Difficult to fit a colored motif into a blotch print by direct style • Aesthetically superior results give the product a higher value for more visit :- https://textilerun.blogspot.com
  35. 35. SELECTION OF DYES: DISCHARGEABILITY • Dyes which are suitable for the dischargeable ground usually contain azo groups that can be split by reduction. • Even so, there are great differences in dischargeability between individual dyes. DISCHARGEABILITY SCALE - 1 TO 5 4-5 Suitable for white discharge 3-4 Suitable for colored discharge 1 - Non dischargeable, suitable as illuminant color SUBSTITUENT ATR1 AND R2 AREIMPORTANT for more visit :- https://textilerun.blogspot.com
  36. 36. CI DISPERSE ORANGE 5 HAS GOOD DISCHARGEABILITY CI BASIC BLUE 41, GOOD DISCHARGEABILITY MORE DIFFICULTTO DISCHARGE DYE WITH DISCHARGEABILITY STILL MORE DIFFICULTTO DISCHARGE R1 and R2 EWG– good discharge EDG– Stable dye, poor discharge OH groups ---H-bonding with azo, difficult to discharge for more visit :- https://textilerun.blogspot.com
  37. 37. DISCHARGING AGENTS MOSTLY- REDUCING AGENTS---??? • Sodium sulphoxylate formaldehyde (CI Reducing Agent 2, Rongalite C) since 1905 • Water-soluble zinc sulphoxylate formaldehyde (CI Reducing Agent 6) • Water-insoluble calcium sulphoxylate formaldehyde (CI Reducing Agent 12) for more visit :- https://textilerun.blogspot.com
  38. 38. Choice of Reducing agent • Depend on Fabric to be printed • Dyes used • Soluble sulphoxylates– Rongalite C- Works better with cellulose • Haloing effect on synthetic fibres caused by capillary movement of solution along yarns. Hence insoluble sulphoxylates (mainly Ca based) and thiourea dioxide (CH4N2O2S) are used • Tin (II) chloride--- can be used but is milder than Rongalite C. • Amount of reducing agent depend upon - Dyes to be discharged - Depth of ground - Fabric for more visit :- https://textilerun.blogspot.com
  39. 39. REACTION SODIUM SULPHOXYLATE FORMALDEHYDE NaHSO2CH2O.2H2O NaHSO2 + 2H2O NaHSO2 + CH2O +2H2O NaHSO4 + 4H Ar-N=N-Ar’ +2 SnO2 + 4HCl Ar-N=N-Ar’ + 4[H] ArNH2 + Ar’NH2 TIN CHLORIDE + 2SnCl2 +4H2O ArNH2 + Ar’NH2 for more visit :- https://textilerun.blogspot.com
  40. 40. THICKENERS • Should be stable to reducing agents • Low-viscosity thickeners and a high solids content • Nonionic locust bean gum ethers, sodium carrageenates, starch ethers etc. for more visit :- https://textilerun.blogspot.com
  41. 41. Enhancing “whiteness” of discharged ground • White discharges are usually improved by addition of TiO2 or ZnO. • Optical brightening agents can be used for more visit :- https://textilerun.blogspot.com
  42. 42. White Discharge style using direct dyes • Sodium sulphoxylate formaldehyde (Rongalite C) is the most widely used reducing agent in discharge printing • Recipe • Rongalite C- 50-150gm • Water – 230gm • Starch paste- 535-455gm • Titanium dioxide/zinc oxide- 100gm • Glycerine/urea- 60gm • Dye--- Print---Dry--- Steaming (100-1020C) for 5-10mins • Light Soaping • Dyefixing if required for more visit :- https://textilerun.blogspot.com
  43. 43. Coloured discharge on direct dyed cotton using vat dyes •Vat discharge on direct ground is an ideal system in which the reducing agent (Rongalite C) performs bothe the functions i.e. discharging the direct dye and reducing the vat dye for fixation •The ground direct dye should have excellent dischageability so that at the printed portions it is completely destroyed and the proper hue of the vat dye is formed at the printed area. for more visit :- https://textilerun.blogspot.com
  44. 44. APPLICATION PROCEDURES VATDISCHARGES ON CELLULOSIC FIBRES • The coloured ground is applied using selected reactive dyes • After printing, the prints are steamed for 5–8 min at 102–104°C in an air-free steamer • Washing and aftertreatment are carried out immediately • For vat color discharges, the first two boxes of the washer are used for oxidation of vat dye • Oxidation is done at 40–50°C with hydrogen peroxide • Hot soaping is followed PADDING SOLUTION (REACTIVE DYES) for more visit :- https://textilerun.blogspot.com
  45. 45. Recipe Chemical Parts Rongalite C 100-200 NaOH (50%) 50-200 Water 200-20 Thickener 645-575 OBA 5 for more visit :- https://textilerun.blogspot.com
  46. 46. OPEN WIDTH WASHING for more visit :- https://textilerun.blogspot.com
  47. 47. PAD STEAM MACHINE for more visit :- https://textilerun.blogspot.com
  48. 48. RESIST PRINTING for more visit :- https://textilerun.blogspot.com
  49. 49. RESIST PRINTING STYLE  Dyes of great chemical stability, which could not be discharged, can be resisted to give prints of high fastness standards.  The resisting agents function either mechanically or chemically or, sometimes, in both ways.  The mechanical resisting agents include waxes, fats, resins, thickeners and pigments, such as china clay, the oxides of zinc and titanium, and sulphates of lead and barium.  They form a physical barrier between the fabric and the colorant. for more visit :- https://textilerun.blogspot.com
  50. 50.  Chemical-resisting agents include a wide variety of chemical compounds, such as acids, alkalis, various salts, and oxidizing and reducing agents.  They prevent fixation or development of the ground colour by chemically reacting with the dye or with the reagents necessary for its fixation or formation.  Not only must a resisting agent be able to prevent the fixation of the ground colour, but it must also be capable of surviving the actual dyeing process.  Hence, materials that are not too readily soluble in water are preferred  For dyeing, Nip padding is usually preferred to immersion (slop) padding. RESIST PRINTING STYLE for more visit :- https://textilerun.blogspot.com
  51. 51.  Some thickening of the pad liquor may be necessary to increase the volume of liquor carried on to the fabric.  The temperature of the dye solution must also be kept low  it is often necessary to dry the fabric immediately after application of the dye, to prevents partial dissolution of paste contents and their diffusion towards non printed areas. NIP PADDING MANGLE REQUIREMENTS for more visit :- https://textilerun.blogspot.com
  52. 52. USE OF A HORIZONTAL PADDER  The horizontal padding mangle may be used to apply the dye solution to the printed fabric  Here also, the contact time between the fabric and the dye solution can be minimized for more visit :- https://textilerun.blogspot.com
  53. 53. RESISTS UNDER REACTIVE DYES  Since reactive dyes are fixed under alkaline conditions, nonvolatile organic acids can be used as chemical resists  Examples - tartaric or citric acid and acid salts like monosodium phosphate  Thickeners used should be acid-resistant  Hydroxyethylated and methylhydroxyethylated cellulose ethers, locust bean gum, etc. are suitable  One of the problems is – these prints are colorless  Hence fugitive color such as CI Acid blue 1 or FBAs can be added for more visit :- https://textilerun.blogspot.com
  54. 54. RESIST PASTE RECIPE  After the print has been dried, it is followed by nip padding or padding with a reactive dye solution  If contact time between the liquor and the fabric is more, acid concentration should be increased to 80 g/kg  Long immersion times should be avoided  After padding, dry, steam (2-10 min ) and wash (boil) CITRICACID for more visit :- https://textilerun.blogspot.com
  55. 55. PADDING SOLUTION COMPOSITION RESIST SALT for more visit :- https://textilerun.blogspot.com
  56. 56. COLOURED RESISTS UNDER REACTIVE DYES WITH PIGMENTS 1. Preprint with pigment paste containing acid 2.Pad with reactive dye, after intermediate drying, or overprint without drying 3. Steam for 2–10 min according to the reactivity of the dye used 4. Wash-off 5. Dry. for more visit :- https://textilerun.blogspot.com
  57. 57. RESIST PASTE FORMULATION for more visit :- https://textilerun.blogspot.com
  58. 58. PIGMENT PRINTING • The cheapest and simplest printing method • More than 50% of all textile prints are printed by this method • Insoluble pigments, which have no affinity for the fibre are used • They are fixed on to the textile substrate binding agents (binders) • Washing is not needed after printing formorevisit:- https://textilerun.blogspot.com
  59. 59. COMPONENTS OF PIGMENT PRINTINGSYSTEMS• Pigment dispersions • Binders and crosslinking agents • Thickeners and auxiliary agents giving the required rheology • Catalysts Pigm ent Printi ng Recip e Pigme nts Bind er Fix er Catal yst Emulsi on thicke ner formorevisit:- https://textilerun.blogspot.com
  60. 60. PIGMENT DISPERSIONS • These are generally synthetic organic materials • Inorganic ones – • Carbon black, • Titanium dioxide (white), • Copper and aluminium alloys (for metallic bronze) • Iron oxide (for browns) formorevisit:- https://textilerun.blogspot.com
  61. 61. IMPORTANT PIGMENT CLASSES • Azo pigments (yellows, oranges, reds) • Naphthalene, perylenetetracarboxylic acid, anthraquinone, dioxazine and quinacridone (very fast and brilliant oranges, reds and violets) • Halogenated copper phthalocyanine derivatives (blues and greens). formorevisit:- https://textilerun.blogspot.com
  62. 62. • Pigments are ground in a grinding mill in the presence of suitable surfactants till they acquire an optimum particle size of 0.03–0.5 μm. • If the pigment is not fine enough, the prints are dull and grey • If they are too fine - loss of covering power and colour intensity (less than the wavelength of visible light) • The dispersion medium is water for water based pigments (20-45%) PIGMENTS formorevisit:- https://textilerun.blogspot.com
  63. 63. BINDER SYSTEMS • Binder is a polymeric film-forming substance • It prod uces dimension ally a thre e- linked net work to hold pigment particles on the textile • The li nks are formed during‘curing’ or ‘fixing’ process • Curing involves dry heat and a change in pH
  64. 64. • It results in eitherself- crosslinking or reaction with suitable crosslinking agents • The degree of crosslinking should be limited • Otherwise the polymeric network may becoming too rigidly bonded (losing extensibility/flexibility) BINDER SYSTEMS for more visit :- https://textilerun.blogspot.com
  65. 65. IMPORTANT CRITERIA FOR A DURABLE 3-D BINDER FILM • Transparency • Elasticity • Cohesion and adhesion to the substrate • Resistance to hydrolysis • As little thermoplasticity as possible • Absence of swelling in the presence of dry- cleaning solvents for more visit :- https://textilerun.blogspot.com
  66. 66. CHEMISTRY OF BINDERS • Generally addition copolymers • Formed by emulsion copolymerisation, leading to a product with 40–45% binder dispersed in water • The size of dispersed polymer particles is 120-300 nm • Low flammability (no solvent) formorevisit:- https://textilerun.blogspot.com
  67. 67. WHAT HAPPENS TO BINDER AFTER PRINTING? • During drying, a film is formed from the dispersed binder in two stages: • Flocculation (or coagulation) and coalescence. formorevisit:- https://textilerun.blogspot.com
  68. 68. MECHANISM - BINDER • During the first stage of film formation, water and surfactants are removed from the binder by absorption and evaporation • The dispersed solids coagulate to form a gel-like layer of very tightly packed ‘balls’, which have only poor solidity and adhesive properties • These coagulated particles can be brought back to their original form by rubbing them with water formorevisit:- https://textilerun.blogspot.com
  69. 69. • Second stage- Gel particles flow together to form a continuous film • The lowest temperature at which a film can be formed is usually around 5°C for pigment printing • Poly(butyl acrylate), for instance, can form a film at 0°C • Polar polyacrylonitrile (PAN) is a very poor film- former even at high temperatures MECHANISM - BINDER for more visit :- https://textilerun.blogspot.com
  70. 70. COPOLYMER AS BINDER • A useful film would need to be produced by copolymerization • The ratio of butyl acrylate : acrylonitrile in the range 3:1–5:1 will give a film with room temp softness • Too hard a film does not have desired flexibility • Too soft a film has poor fastness to dry cleaning (swells) for more visit :- https://textilerun.blogspot.com
  71. 71. CROSSLINKING • Cross linking provides elasticity and improved adhesion of the film to the substrate • The crosslinking reaction produces covalent bonds which are resistant to hydrolysing agents (washing liquors, body sweat, industrial atmospheres) • The reaction should be activated only during fixation formorevisit:- https://textilerun.blogspot.com
  72. 72. CROSS LINKING REACTION • Use of N-methylol groups is done to effect crosslinking under hot dry conditions (in acid media) • Reaction of methylol groups with each other or with hydroxyl groups which are also present in cellulose or in the binder copolymer, takes place • Water is a byproduct of the reaction • Hence, hot dry air (130-150oC) is suitable • Steam has adverse impact on cross linking formorevisit:- https://textilerun.blogspot.com
  73. 73. CONSTITUTION OF BINDER • The binder molecule is prepared such that it contains about 2% N-methylol groups evenly distributed along the chains • This is done by copolymerizing monomers such as Methylol acrylamide, Methylol methacrylamide ( or derivatives) with the main monomers (such as acrylic acid esters, acrylonitrile or butadiene) • Higher % of methylol groups would make the chains too rigid, resulting in poor formorevisit:- https://textilerun.blogspot.com
  74. 74. METHYLOL ACRYLAMIDE formorevisit:- https://textilerun.blogspot.com
  75. 75. EXTERNAL CROSSLINKING AGENTS • External poly-N-methylol compounds can be added to enhance crosslinking • Especially useful for hydrophobic materials • Water-soluble derivatives of tetra- to hexa-methylol melamines are preferred (melamine formaldehyde resin) • Act mainly as adhesive agents between the textile and binder • Also contribute to the crosslinking at the surface of the binder film formorevisit:- https://textilerun.blogspot.com
  76. 76. THICKENING SYSTEMS • The colloidal polysaccharide thickening agents are not suitable for pigment printing • (Examples starch, cellulose ether, alginates or locust bean gum) • Their flow properties are unsuitable and they form brittle films • The prints produced with such thickeners are dull with poor fastness and a harsh handle
  77. 77. PROPERTIES OF PRINT PASTES• Pseudoplastic (shear- thinning) pastes are suitable for pigment printing • Such pastes do not penetrate deep down into the textile fabric • Paste on surface provide better color value, a sharp mark and brilliance of color • Also handle is better as the fibres and yarns are not bonded by binder and cross linking
  78. 78. EMULSION THICKENERS• The most suitable are the emulsion thickeners • White spirit/water emulsions (o/w type) are of the greatest practical interest • Composition -  70-79% hydrocarbons in the disperse phase  0.5-1% of nonionic emulsifiers with HLB in the region 12-15  29-20% of water in the continuous phase.
  79. 79. PROS AND CONS • All the components, except the emulsifying agents, evaporate completely, leaving no residues • There is no hardening of the handle of the textile due to thickener • Drying of the printed textile is quicker as the evaporation enthalpy for white spirit is about 25% of that for water • This improves the printing speed and hence the production • Mineral oil products are too valuable to be used just as print paste thickening agents
  80. 80. • The emission of organic substances into the atmosphere is not desirable • Recovery of the white spirit from the exhaust gases by cooling apparatus and batteries of charcoal filters is too complicated and too expensive • 0.4% by volume of white spirit in air is flammable • In India, Kerosene oil is used, which is flammable too • Hence print pastes based on white spirit/kerosene are being phased out PROS AND CONS
  81. 81. SYNTHETIC-POLYMER THICKENING AGENTS • Synthetic thickeners are polyanionic compounds derived from acrylic acid and maleic anhydride • Have rheology similar to that of emulsion thickeners and extremely low solids content • Have very high swelling power (maximum at pH 9-10) • Ionization increases solvation in water • Ionization creates charged groups which cause repulsion and hence the material expands in dimensions • This brings about a hundredfold expansion in size
  82. 82. • These are sensitive to presence of salts, hard water, acidic pH etc • On drying, it leaves a residue (0.5-1%) • The dry thickener film is hard and inflexible • Has adverse effect on handle of printed material • It can be compensated by use of softeners • Neutralizing agent is ammonia, removed during drying • The carboxylic groups provide the required acidity for binder reaction. No additional acid liberating agent required • Emulsion thickener based pastes need about 0.5% potential acid, such as diammonium phosphate (DAP), for required acidity SYNTHETIC-POLYMER THICKENIN G AGENTS
  83. 83. COPOLYMERISING 1 MOL ACRYLIC ACID AND 0.01MOL DIVINYLBENZENE TO FORM A THICKENINGAGENT
  84. 84. PIGMENT PRINTING PASTES • The amount of binder needed in a print paste is related to the amount of pigment • Even the minimum amount of pigment requires a binder film at least 5μ thick • A minimum of about 7% binder (of about 40% solid content) in the paste is needed • Additional pigment needs about 1.5–2 times its own mass of binding substance (25% pigment emulsion and 40% binder emulsion– Pigment : binder, 1:2.5 TO 1:3) • For hydrophobic materials (including polyester/cotton blends), another 0.5–1% of external crosslinking is added
  85. 85. RECIPE REDUCTION THICKENER (EMULSION BASED) 1. Emulsion thickener Water- 10parts Binder- 10 parts Kerosene oil- 79 parts Emulsifier – 1 part Total – 100parts 2. Print Paste Pigm ent -- X parts Urea -- 5 parts Di ammonium phosphate (DAP) – 1 part Binder -- As required ( Added only for dark shades) Cross-linker – In case of synthetic fibres 1 part Emulsion Print– Dry (800C, 3-4 mins)—Cure (1500C for 3-5 mins)
  86. 86. Synthetic THICKENER (WATERBASED) 1. Aqueous synthetic thickener paste Water- 90-95 parts thickener- 9-4 parts Ammonia- 1 part Total – 100parts 2. Print Paste Pigment -- X parts Binder -- As required ( Added only for dark shades) Softener – 1part Crosslinker– In case of synthetic fibres 1 part Antifoamer– If required 0.5 parts Thickener paste -- Tomake 100 parts
  87. 87. POSSIBILITIES AND LIMITATIONS Advantages • The most economical printing process and allows maximum output of goods • Elimination of washing-off, quick sampling and high printing speeds • Have very good fastness to light and good general fastness properties • Can be applied to all substrates (including glass fibres, PVC and imitation leather) • Well suited for colour resist effects • Presents the fewest problems for the printer • Ecologically, is more acceptable than any other system (if not using white spirit/kerosene)
  88. 88. Limitations • The fastness levels of medium- or dark- coloured prints on materials made from polyester, acrylic and wool are not adequate • The handle of the printed goods is often unduly hard because of the large amounts of external crosslinking agents • Pigments are sensitive to crushing during roller printing • In overprinting, the second paste has little effect: the paste first printed determines the colour • No pigment print is completely fast to dry
  89. 89. Transfer printing
  90. 90. Types of transfer printing • Sublimation transfer • Melt transfer • Wet transfer • Film release
  • melsefirew

    Aug. 10, 2021
  • ProsenjitGhosh25

    Feb. 12, 2021
  • fristariyanti

    Mar. 5, 2020

Styles of printing; Printing thickeners including synthetic thickeners; Printing auxiliaries; Printing of cotton with reactive dyes, wool, silk, nylon with acid and metal complex dyes, Printing of polyester with disperse dyes; Pigment printing; Resist and discharge printing of cotton, silk and polyester; Transfer printing of polyester; Inkjet printing.

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