Textile Printing introduction and style, methods

Technology of Textile Printing Syllabus Unit I 1. Principles of printing, 2. Printing paste ingredients viz. various thickeners and other chemicals, 3. Methods of printing such as block, screen, roller printing. Unit II 4. Preparation of screen for manual, flat bed and rotary screen printing machines, 5. Engraving of design on roller, 6. Styles of printing viz. Direct, Discharge and Resist on natural fibres. 1

Unit III 7. Styles of printing viz. Direct, Discharge and Resist on synthetic and their blends, 8. Machines used for printing, drying, steaming, and curing. Unit IV 9. Novelty printing process 10. Transfer printing of synthetics and cotton, 11. Flock printing 12. Garment printing 13. Pigment printing i . Various type of pigments, binders, catalysts and emulsion thickeners, ii. Replacement of kerosene, 14. Faults in printing and their prevention. 2

Unit V Ink jet Printing (Covered in Novel printing) 15. Application of printing CAD software, design preparation, colour reduction, colour separation, screen preparation. Books -Technology of Textile Printing- R S Prayag -Technology of Printing- Dr V A Shenai -Principals of Cotton Printing- D G Kale -An Introduction to Textile Printing- W Clark -Textile Printing- L W C Miles --xx-- 3

UNIT I 1. Introduction Homogenous application of colour is known as dyeing, where as local application of colour on only required space is known as printing. The dyeing requires solution, whereas printing requires paste. Moreover, complete fabric immersed in dye solution during dyeing, whereas only required fabric print with printing paste. These are some basic differences between dyeing and printing. A paste is used in printing against the dye solution. 1. Printing paste ingredients viz. various thickeners and other chemicals :- In printing, main ingredient is dyestuff, second is thickener. The main object is to print or produce coloured designs in one or more than one colours with sharp boundaries on textile materials without any of the dyes spreading beyond the boundaries of the design. 15-4-2021 4

2. Printing paste ingredients are as follows:- i . Dyestuff or Pigment ii. Thickener iii. Solvents iv. Hygroscopic Agents v. Wetting Agents vi. Oxidizing Agents vii. Reducing Agent viii. Carriers ix. Catalyst x. Defoaming Agent xi. Mild Oxidizing Agents xii. Acids and Bases xiii. Oxygen Carriers xiv. Swelling Agents xv. Miscellaneous Agents During printing, it should be keep in mind that all these constituents are not used simultaneously in any printing paste. Depending on the fabric quality, dyestuff & styles of printing, suitable components are selected in making the printing paste. The choice of a component from a group depends on its compatibility with the other ingredients of the printing past. Thus, starch is used as a thickener for printing direct dyes on cotton fabrics, but it is not suitable for printing reactive dyes on cellulosic fabrics, since a part of reactive dye also react with starch during steaming in additi - 5

to the reaction of the bulk of the dye with cotton and when the thickening agent is subsequently washed, a part of the dye (that reacted with starch) is removed; resulting in wastage of this dye. Due to this, lighter prints are produced. i. Dyestuff :- A suitable dyestuff is used as a colouring matter depending on the nature of the fibres i.e. direct dye for cotton, reactive dye for cotton and wool, an acid dye for wool, silk and nylon, a disperse dye for polyester, basic dye acrylic and so on. In case of colour discharge printing, the dyestuff should be different category because one dyestuff to be discharge while other not. There are two types of dyes- water soluble and water insoluble dyes. Water soluble dyes are strips-out when treat in hot water, specially in presence of soap; water insoluble dyes will not bleed into the washing solution. 6

Different classes of dyes possess different fastness properties to various extents, even dyes belonging to the same class have widely varying fastness properties. A single dye, which dyes all the known major textile fibres is not made yet. Vat dyes, Solubilised vat dyes, Reactive dyes, Azoic dyes, Direct dyes, Acid dyes, Metal complex dyes, Basic dyes, Disperse dyes, and Oxidation colours (Aniline black, Mineral Khakhi etc. ) are well known dyestuff and colouring matters. Pigments are coloured or colourless substances which are inert and insoluble in aqueous and resinous media and having no preferential affinity to the fabric or the material on which they are applied. Unlike to dyes, they have not chromophore and auxochrome groups. They are applied with the help of binders. Their fastness to light are high. Acramin colours , Acron colours , Imperon colours , Tinolite colours , Metal powders used to imitate gold and silver effects are some 7

examples of pigments. Titanium dioxide and zinc oxide are used as white pigments and carbon black as black pigment. ii. Thickeners :- After dyestuff, thickeners are the main components which are used in printing paste and due to these, it is known as paste . These are high molecular weight compound, gives viscous paste in water. These improves stickness and plasticity to the printing paste so that it can be applied to a fabric surface without spreading and be capable of maintaining the design outlines even under high pressure. The main functions of thickeners is to hold or adhere the dye particles in the desired place on the fabric until the transfer of the dye into the fabric and its complete fixation. The viscocity of the printing paste should be sufficiently high to prevent rapid diffusion of the colour through the fabric which would results in poor print diffusion or mark. 16-4-21 8

A Printing paste thickener should have the following essential qualities :- A. Stability to keeping viscosity should be good. Aqueous dispersion or paste of high molecular weight thickeners may undergo fractional crystallization. On standing, upsetting the flow property and concentration of the dye in the printing paste may leading to the interference with the regular distribution of the dye. B. It has certain viscosity, flow property, ability to wet and adhere to internal surface of etching of engraved roller. C. It must be compatible with the other ingredients. D. The film should dry properly on the fabric to prevent spreading of the colour by capillary action. E. Proper extraction of water from system during steaming should be ensured to provide free space for the dye 9

molecules to move towards the fabric and free water to carry it. F. These should not have any affinity towards the dye and fabric, G. These should have control over the free water pick-up and not carry the dye beyond the boundaries of the impression, H. The removal of exhaust thickener film should be easily, and, I. These should be cheep and available at suitable price. Rheological behavior of gum :- As the roll of thickeners is very important and quality of print is widely depends upon the thickener, so it is necessary to separate study about it. The water soluble gums may be divided into four groups depending on their viscosity response to an applied force in an aqueous media. These are- a) Newtonian flow b) Dilatent flow c) Thixotropic flow, and,d ) Pseudo-plastic flow 10

Viscosity may be defined in two ways- It is the ratio of shearing stress to the rate of shearing . or it is the measure of the resistance of a liquid to flow Shearing stress Viscosity = --------------------- Shear Rate Force Shearing stress = --------------------- Area Sheared Velocity Shear Rate = --------------------- distance covered a) Newtonian Flow :-In this case the viscosity is not dependent upon the time or shear rate. It is, however, dependent upon 11

the solution concentration and temperature. Solutions of high polymers are very rarely Newtonian. Shear rate is directly proportional to applied shearing stress. b) Dilatent flow :- It involves an increase viscocity with increasing shear rate. Starch exhibits dilatent flow. This flow is rarely encountered except in dispersion having about 50% solids. c) Thixotropic flow :- This flow involves a decrease in viscosity as a function of time. Thixotropic systems re-established their structure upon standing undisturbed. This flow never exists alone, it is a superimposition of the viscosity-time relationship upon either Newtonian, dilatent or pseudo-plastic flow. Solutions of CMC, hydroxymetyl cellulose etc. can be thixotropic or pseudo-plastic. d) Pseudo plastic flow :-Most polymer solutions of moderate concentrations exhibits this type of flow. In this case, viscosity 12

decreases with increasing the shear rate. Hydroxyethyle cellulose, CMC, alginate etc. demonstrate pseudo- plasticiy . Clssification of Printing Thickeners Natural Modified Natural Synthetic Cereals Plants Roots Sea Starch Cellulose Gum Acrylic Vinyl Starch Extracts & Seeds Weeds Derivatives Derivatives Derivatives Derivatives Derivatives -Maize -Gum - Guar -Sodium British CMC - Meyprogum - Polyacrylic PVA -Rice tragacanth Gum Alginate Gum Hydroxy - Indalca Acid -Wheat -Gum -Locust Ethylene - Polyacrylic Arabic bean Cellulose Amide gum The main function of a thickener is to imparts stickeness and plasticity to the printing paste, so that it may be applied 13

on the fibrous surface without bleaching and be capable of maintaining the design outlines even at the application of a high pressure. A printing paste differ from a dye solution in this way that it has a retaining capacity. Owing to this property, it is possible to obtain a pattern on the fabric. 22.04.2021 iii. Solvents :-For preparing a printing paste, it is necessary to dissolve the dyestuff in small amount of water. Therefore, solvents are used to prevent agglomeration or prevention of the dyestuff in paste. These are used as additives to printing paste to produce better penetration. Different solvents are used for different dyestuff. 14

Soledon developer GE is used for printing vat dyes and azo dyes. Tetralene , Decalene , ethylene glycol, diethylene glycol and thiodiethylene glycol are well known solvents used for acid, solublised vat dyes and leuco vat dyes. Solution salt B, solution salt SB, etc. are used for making paste of powder brand vat dyes and for preventing the sudden oxidation of leuco vat in the paste. Solvents increases the solubility of vat and solublised vat dyes and increase their colour yield. Tetracarmit is used for dissolving rapid fast colours . Thio-diethylene glycol is an excellent solvent for basic, direct, acid and disperse dyes. It is used to assist the solution of these dyes and promote the production level and deeper printed patterns. It has hygroscopic and solvent action for vat dyes in leuco and solulised vat forms and also for basic dyes as their tannic acid lackes . Urea is a well-known solvent as well as hygroscopic agent. 15

It assists in getting more complete fixation of the dyes so that a deeper shade is produced. It also facilitates the subsequent washing-out of the thickener film from the fabric. iv . Hygroscopic agents :- Hygroscopic agents absorb sufficient amount of steam during steaming and enables the molecules to diffuse into the fibre. It is essential to use optimum quantity of the hygroscopic agents. When lower quantity is used, all the dye present in the thickener film may not dissolve in the insufficient amount of water absorbed by the thickener film, resulting in poor colour yield. When we used larger amount of hygroscopic agents, more water is supplied to the thickener film, which may results in the spreading of the dye solution beyond the boundaries of the design. Urea, glycerine , cresylic acid, acetin (acetyl glycerine ) are some examples. Acetin is used for fixing acid and basic colours . 16

v. Wetting agent :- These are used to obtain a smooth paste of the dyestuff without formation of any lumps which if allowed to remain, get deposited on the cloth during printing producing dark spots. Turky Red oil, monopol Brilliant Oil are the examples of wetting agent. Surface tension of water is force which resists the wetting of a hydrophobic surface with water. Water is found to have a surface tension about 73 dynes/cm. The compounds which dissolve in water and reduce its surface tension are known as wetting agent or surface active agent or surfactants. It is possible to bring down this value from 73 dynes/ cm to 28 dynes /cm by dissolving soap in water. Since, surface tension of a liquid is a force that resists wetting of a surface with the liquid, it follows that if this force is reduced considerably, it should be possible to wet the surface easily. 23-04-2021 17

vi. Reducing agents :-These are used to prevent oxidation of dyes. These are mainly used in case of discharge printing on azoic ground. Sodium hydrosulphite is a well-known dischar-ging agent in case of vat dyeing, but it may not used at high temperature such as in printing. Its stable form sodium sulphoxylate formeldehyde (NaHSO 2 CH 2 O.2H 2 O) is used as reducing agent for azoic ground as well as for direct, acid and reactive dyed grounds discharging. Safilin is its zinc salt; zinc sulphoxylate formeldehyde , which is used in discharge printing of polyester fabrics dyed with disperse dyes. Sodium bi- sulphite is another reducing agent, used for discharging naphtholated grounds. It is used in conjunction with zinc dust in discharge printing of silk dyed acid dyes. SnCl 2 , SnCl 4 (Tin salts) are also used as reducing agents, perticularly in coloured discharge. The salt is used as a resist agent, while printing with diazo salt :- 18

Na 2 S 2 O 4 + 2HCHO+H 2 O→ NaHSO 2 .CH 2 O + NaHSO 3 .CH 2 O formeldehyde Sodium sulphoxylate sodium bisulphite formeldehyde formeldehyde The commercial name of sodium sulfoxyate formeldehyde is Rongalyte C and of zinc sulfoxyate formeldehyde is safolyte . Formosul , hydrosulphite NF etc. are some another reducing agents. vii. Oxidising agents :-These are used for developing the final colour during steaming or in developing bath in the case of solublised vat dyes, aniline black etc. Sodium dichromate is used as an oxidising agent in discharge printing of Indigo. It is also used in combination with mineral acid for oxidation of vat dyes. Sodium bromate is also used for this purpose and it produces bright prints. Chlorates, nitrates, nitrites and potassium ferrocyanide are commonly used as oxidising agents. 19

The oxidising agent should be such that it is not active in the printing paste, otherwise premature development of the colour may takes place and its subsequent fixation in the fabric may not be possible. viii. Carriers :- These are mainly used for fixing disperse dyes on polyester or polyester-wool blends at temperature below than 105°C. Some of their trade-names are Tumescol OP, Tumescol D and Dilatin B. Benzyl alcohol is used as a carrier in the printing of acrylic fabrics with cationic dyes and phenols and resorcinols used in the printing of nylon fabrics. The compact structure of synthetic fibres especially polyester fibres makes it difficult for the dyes to penetrate inside the fibre structure under the conditions of dyeing at boil and steaming at 100°C to 102°C in a rapid ager. Certain hydrocarbons, substituted hydrocarbons, phenols etc. acceler ated the rate of dyeing of polyester fibres with disperse dyes 20

from an aqueous medium at about 100°C. one of their functions is to swell the fibres, so that the dyestuff molecules can diffuse in them easily. The carriers should be easily removal from the fabric, as the residual carrier may lower the light fastness of the dyeing and print may be toxic in nature. ix. Catalyst :- Some catalysts are used in printing when oxidation is involved in the subsequent steaming. There is a danger of the oxidising agent attacking the fibre substance at the elevated temperature of steaming in addition to the fulfilling the purpose for which it is used. In order to reduce this risk of fibres substance being oxidised , a catalyst is used so that the development of the colour by oxidation is active. These are used to accelerate the development of colour by oxidising agents and reduce the risk of their attack onto the fibres. Potassium ferrocyanide (K 4 FeCN 6 ), copper sulphide ( CuS ), 21

ammonium vanadate etc. are used as catalyst in the printing of aniline black and solublised vat dyes. x. Defoaming agents and defoamers :- Many colours produces froth (foam) during printing. Due to this, lighter shade produces. In roller printing, the wetting agents in the paste with continuous agitation produces considerable foam in the colour box. This produces faulty prints. To avoid this fault, defoamers are used in the paste. Perminal KB of ICI is a defoamer , anionic in nature containing an emulsion of sulphonated sperm oil (An oil found in head of a fish) and pine oil mixture. xi. Mild oxidising agents :- These are used to prevent reduction of dyes during steaming as otherwise the dye may get partially destroyed due to reducing fumes. Resist salt L, 22

Albatex BD and ludigol (sodium meta nitro benzene sulphonate ) are commonly used as mild oxidising agents. Sodium chlorate is particularly used to prevent the brightness of polyester prints against any reduction of disperse dye during steaming at high temperature. 24.04.2021 xii. Acid liberating and alkali liberating agent :- Whenever acidic conditions have to be created during steaming, an acid liberating agent to be used in printing paste. This acid is needed for the development of certain classes of dyes, like solublised vat dyes and to activate a potential oxidising agent like sodium chlorate for aniline black, and solublised vat dyes during the steaming stage. It is also needed in curing stage for fixing the pigments and binders in case of pigment printing. The free acids should not be added to the printing paste, otherwise premature development of the colour may takes place in the printing paste it self. Two types of compounds are normally used for this purpose :- 23

Esters of organic acids, and Ammonium salts of mineral or organic acids In both the cases, the compounds do not react acidic initially and during the steaming conditions; acidity is generated by splitting of the ester into the acid and alcoholic vaporises and by association of the ammonium salts into the corresponding acid and ammonia. Ammonium sulphocyanide ; NH 4 CNS, Ammonium chloride, NH 4 Cl , diammonium hydrogen phosphate, (NH 4 ) 2 HPO 4 ), ammonium glyconate (H 4 NOO(CHOH) 4 OH, ammonium sulphate , Ammonium nitrate etc. are used in printing paste as the acid liberating agent. Alkalies - Mild alkalies , include sodium carbonate, potassium carbonate, sodium bicarbonate, sodium silicate, di -sodium hydrogen phosphate, tri-sodium phosphate, sodium acetate, 24

triethanolamine , ammonium hydroxide are mild alkalies . These are used to make solution slightly alkali and also used to neutralise the acidic conditions. xiii. Swelling agent :-Some carriers are works as swelling agents also. Their main function is to swell the fibres so that the dyestuff molecules can diffused in them easily. Ammonium carbonate is well known swelling agent. xiv. Miscellaneous chemicals :- Except the above chemicals, some chemicals are also used in printing. Generally these are the chemicals, specially used for special purpose. In the case of vat dyes of good dischargability , certain complaxing agents are incorporated in the printing paste containing a reducing agent and printing on vat dyed fabric, which is then steamed. Cellulose ethers and esters are used as auxiliaries to thicken the paste and protect the dye. 25

3. Methods of printing :-Methods of printing denote the means of application or appliances used for producing the coloured effect. It includes the machineries or equipments by which printing effect carried out. Generally, followings are the methods of printing :- Block printing Stencil printing Roller printing Screen printing Transfer printing Inkjet printing Xerography 26

i ) Block Printing :- It is oldest and simplest method of printing. In this method, wooden blocks are used to print the design on to the fabric. Designs are print onto the fairly hard, close grained wood such as sycamore with the help of chalk or colour . Then these designs are engraved with the help of fine sharp equipments. During printing, blocks are charged with printing paste which is properly sprayed on a woollen or cotton fabric. The cotton fabric or woollen fabric has sprayed on swimming tub containing liquid of proper viscosity. After charging the blocks, these are carefully applied on to the fabric, which is to be print. The fabric should be properly tent. The corner setting is the most artistic work in this method. Maximum 10-12 colours may be used in this method. It is simplest and easily applicable, blocks has fullness and purity of colour , number of size of repeat and prints are great and decorative. 27

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Using two blocks, we may also obtain 3 colour effect, if some parts are common. 29-04-21 Some demerits are here. This method is slow, fine cutting or lines are difficult, joining of repeat is difficult and requires experience, finally, it is laborious method. Stencil printing :- This is also a printing method. A stencil is prepared by cutting-out a design from a flat sheet of plastic , iron or other metal. When design is completed, sheet is kept on to the fabric and colour is applied with the help of brush on the sheet. Through hollow spaces, design is applied onto the fabric. It is a simple method, does not requires elaborate or expensive equipment and has low production cost. The stencil cutting is not more expensive and any type or colour can be used. 29

Stencil Printing 30

A complete closed shape like can not be produced by this method. For producing such type figures, a ‘tie’ or joint mark is used, which break the continuity of the shape. It is also laborious. It can not suitable for large scale production. iii) Roller printing :-Both the above methods are manual, no any special equipment or machine is used for producing the design. Roller printing is advanced among the above methods. In this method, design is engraved by chemical treatment onto the hollow steel or iron rollers. These rollers are then used for print the fabric. The fabric to be print fed to the machine and as the driving motor is switched-on, it moves forward around the central cylinder, which also starts rotating. At the same time, the engraved rollers and the colours furnishing rollers starts rotating at suitable speeds to keep together with the fabric. 31

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The colour furnishing roller picks-up the colour paste from the colour box in which it rotates and transfers the colour to the engraved rollers and fill up its to hollows or the required pattorn . The engraved rollers has no colour on other part of its surface. As the engraved roller comes in contact with the dry fabric and is pressed against, the colour is transferred and the particular part of the design is impressed on the cloth. The doctor blade scrapes of the excess amount of colour paste and the lint doctor removes tiny fibres from the fabric. After print, fabric send to curing or steaming. 30-04-21 -----xxx----- 33

UNIT II 4. Preparation of screen for manual, flat bed and rotary screen printing machines i . Screen Printing :- It is upgraded form of stencil and roller printing. The following 3 types screen printing are used in textile :- Hand screen printing b) Flat bed Screen printing c) Rotary screen printing 1) Hand Screen Printing :- In hand screen printing, nylon bolting cloth, which have EPI and PPI more than 120-130 are used. Screens are used in hand screen printing and flat bed screen printing, where as Nickel screens are used in rotary screen printing. Hand screens, which are prepared by photographic methods are used in this printing. 34

b. Preparation of screen for hand screen printing and flat bed printing :- In this printing, nylon bolting cloth is mounted tightly on to the iron or wooden frame. Then photo-sensitive chemical is applied on the screen. For this purpose, following recipe is used- 600 gm. Polyvinyl alcohol (15% solution) 120 ml Ammonium dichromate solution (33%) 240 ml cold water At first, 90 gm. Solid PVA dissolve in warm water to making total volume 600 cc. make a gelatinous solution by continues stirring. When a clear transparent solution prepared, stop it to warm and stirring. In a dark room, 39.6 gm. Ammonium dichromate is added into water and make total volume 120 cc. When it is completely dissolve, add this solution into PVA solution and add required 35

amount of water to form a viscous paste. With the help of squeegee, this paste is evenly spread on to the screen (nylon bolting cloth) and dry it completely in dark room. On a designing table, put the design trace paper on which design is printed in black colour . Light should not be passes through the design, otherwise the paste will be fixed on to the place. Then expose it for 2-3 minutes by milky light of tube-light or bulb. Due to exposing, the place, from where light is passes, will be permanently filled and fixed by the photosensitive paste and other will be remain empty. So on washing, the paste from designed place will be removed. The same method is used for preparing the flat-bed screen. This screen will be fixed and after fixing, used for printing. For printing, screen is put on the fabric, which is spread on the 36

printing table. Colour paste is pour one side of the screen and minimum two strokes are applied with the help of squeegee. Then dry and send the fabric for after treatment either curing or steaming. For printing by flat bad screen printing machine, screens are fit into the machine. The machine is semi automatic or intermittent type. With the help of cams and livers, fabric moves one repeat unit, screens comes down, colour supplys on the screens, two strokes takes with the help of squeegees and screens moves one repeat unit forward. This sequence continue till all the fabric printed. Then the fabric send to steaming or curing unit. 37

Hand Screen Printing 38

2) Automatic Flat Bed Screen Printing :- Basically, the operations of all the flat bed screen printing machines are same. It is developed from ordinary screen printing process. In case of screen printing, we can take higher production. By the use of this machine, generally 8-10 colours can be printed successfully in a design. This machine can be divided into following parts :- A) Feeding Section :- This section has the purpose to feed the fabric properly. At starting end, there is batch stand, where batches are mounted. There are two guide rollers and one tension bar. The fabric has passes through these rollers and bar. After the guide rollers, the fabric passes under the pressure roller. The purpose of pressure roller is to press the fabric with the endless blanket, so it would adhere properly and have no wrinkles. Properly feeding of the fabric is necessary for good printing. 39

Flat Bed Screens 40

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B) Flat bed section :- Endless Blanket or Conveyor Belt :- The machine consists of an endless blanket, which is also known as conveyor belt. Gum is applied on it by the gumming arrangement. The cloth is passed over the blanket adhere by pressing the roller at the time of entry and after printing, it is separates and passes through the printed cloth dryers. The purpose of blanket is to provide a proper and even surface to the fabric which is has to print. Screen :- This machine consists of flat screen made-up of nylon bolting cloth, fixed on the iron or steel frame. It contains two screws on each side of frame which helps in fitting of screen inside the frame. The screens are prepared by the photographic method. The size of screen depends upon the width of the machine and design. 42

Screen goes down as the conveyer belt stop, then print the fabric, lifted up and fabric moves by one repeat and this cycle is continued till the whole fabric is printed. The difference between two screen frame are exactly equals to one repeat. iii) Squeegee :- Blade type squeegee is used which is made up of rubber. It is fitted on the iron frame which based on sliding rail backward motion. For the motion, the squeegee may one or more stroke over the screen. The screen lifts up and design forwarded to one repeat unit. iv) Automatic Colour Feeding Arrangement :- Perpared colour paste is filled to colour tank. The colour is supplied to the screen through the flexible pipe from the colour tank. It is then distributed through-out the screen width with the help of squeegee. It is automatically done by motor. Sensors are 43

used to measure the colour level and feed the colour automatically and stop the supply when level has achieved. This work is carried out by manually . v) Screen Lifting Arrangement :- A motion from main motor goes to the shaft by a chain or belt. The motion is then transferrd to semicircular gear, then through a lever, it transferred to a cam. Through lever and bars, all screens are lifted together and after moving the fabric by one repeat unit, again goes down and print the fabric. vi) Blanket Washing and Drying Arrangement :- After printing, conveyor belt sweded by printing paste and gum, so it is necessary to wash the belt. For this purpose, it is washed and dried before again gumming and feeding. Washing and gum ming and feeding. Washing and gumming arrangement is provided in the bottom side of the machine. 44

For washing, water is sprayed over the blanket by a pipe containing tiny holes in its long side. Then it cleaned by brushing and dried by heating arrangement. After drying, blanket is passes to kiss-roll arrangement, where gum is applied on it. In this arrangement, a roller is half dipped in gum trough and transfers its gum to another roll, which apply the gum to the endless blanket. This gum help to fix the fabric on the blanket so that fabric does not vibrate or move during printing and avoid miss fitting. C) Fabric Drying Arrangement :- After printing, the fabric is passed through the drying unit, fabric is dried at very high temperature. Then it is passes for steaming and washing unit. Procedure :-The cloth is feeded along with the conveyor belt through hot rollers. When it strikes to the belt, it moves forward and prints with different designs and colour with the help of number of screens. After printing, the fabric is passed 45

through drying chamber and then steaming chamber. In this way, continuous printing is achieved. 17-5-21 The main feature of this machine is that pallu of saree can be print. After print the pallu , the related screens are lifts up and ground is print. Advantages of F.B.S.P.M. :- Economical for short run, Extra design like pallu and cross border can be printed, Any repeat is possible to print with the range of 40 cm. to 360 cm. Printing of knitted goods and fine fabrics is also possible due to no tension, Heavy blotch and integrated designs are possible in this machine, 46

vi. 10-12 colours may be used, vii) Less dye consumption in this machine than roller printing machine, viii) It is typically important for printing handkerchief, scarf, table cover etc. ix) Good sharpness and maximum penetration is possible. Disadvantages of F.B.S.P.M. :- It is suitable for only short run, so production is low, Joint marks may be occurs, Limited colours are used 3) Rotary Screen Printing Machine :- This machine is widely used in printing industry. It has combined advantages of roller printing machine and flat bed screen 47

printing machine. So it gives high production with more colours . 48

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50 The squeegee lies inside the circular screen. It may be rod type or flexible blade type. The machine is usually built for 6, 9, 12, 15 or 18 colours for printing a maximum width of 160, 180, 240, or 360 cm. In all, upto 24 screens can be printed and it is possible to obtain a speed between 10-100 mt . per minutes without any defect. During a working shift of about 8 hrs. it is possible to obtain a production of about 15000 mt . to 20000 mts . printed fabric. It is suitable of printing of any type of fabric of any constructional (plain, satin, twill etc.) with knitted fabrics. Principle :- The basic principle of this machine is that in this machine, an engraved nickel screen is used. Nickel has been found to be the most suitable metal, because of its high tensile strength, flexibility and good resistance to most of the chemicals used in printing paste. Nickel screens are costly, so

most of the rotary screen printers have own nickel shell manufacturing unit. The designs are engraved opposite, i.e. for print ‘p’, engrave ‘q’ on the screen. A rotary screen printing machine has following main parts:- A) Feeding Section :- This section has the purpose to feed the fabric properly. At starting end, there is batch stand, where batches are mounted. There are two guide rollers and one tension bar. The fabric has passes through these rollers and bar. After the guide rollers, the fabric passes under the pressure roller. The purpose of pressure roller is to press the fabric with the endless blanket, so it would adhere properly and have no wrinkles. Properly feeding of the fabric is necessary for good printing. In some machines, an accumulator is also attached with the machine, which helps for continuous running the machine. 51

B) Printing Section :- Endless Blanket or Conveyor Belt :- The machine consists of an endless blanket, which is also known as conveyor belt. Gum is applied on it by the gumming arrangement situated below the endless blanket. The cloth is passed over the blanket adhere by pressing the roller at the time of entry and after printing, it is separates and passes through the printed cloth dryers. The purpose of blanket is to provide a proper and even surface to the fabric which is has to print. ii) Circular Screen :- This machine consists the nickel screens which are manufactured by lacquer in stream or galvanise stream. The perforated circular screens are the heart and soul of this machine, which are without a repeat unit. The main difference between FBSPM and RSPM is that the 52

previous has flat bed screen, whereas later has circular screen. iii) Squeegee :- Blade type or manetic squeegee is used. These both squeegees are used in rotary screen printing. Blade type squeegee is made up of rubber. It is fitted on the steel or iron frame which stand in core section of the screen. Due to sharpness of blade, it gives fine design, but tearing of lacquer is high due to pressure. So, in printing of sarees , manetic squeegee is used. In the machine, below the screen, an iron strip or angle is situated. In the screen a magnetic rod is put. Due to generation of megnetic field, a suitable pressure creates, which equally spreads the colour paste. iv) Automatic Colour Feeding Arrangement :- Perpared colour paste is filled to colour tank. The colour is supplied to the screen through the flexible pipe from the colour tank. It is 53

then distributed through-out the screen width with the help of squeegee. It is automatically done by motor. Sensors are used to measure the colour level and feed the colour automatically and stop the supply when level has achieved. v) Blanket Washing and Drying Arrangement :- After printing, conveyor belt sweded by printing paste and gum, so it is necessary to wash the belt. For this purpose, it is washed and dried before again gumming and feeding. Washing and gumming and feeding. Washing and gumming arrangement is provided in the bottom side of the machine. For washing, water is sprayed over the blanket by a pipe containing tiny holes in its long side. Then it cleaned by brushing and dried by heating arrangement. After drying, blanket is passes to kiss-roll arrangement, where gum is applied on it. In this arrangement, a roller is half dipped in 54

gum trough and transfers its gum to another roll, which apply the gum to the endless blanket. This gum help to fix the fabric on the blanket so that fabric does not vibrate or move during printing and avoid miss fitting. C) Fabric Drying Arrangement :- After printing, the fabric is passed through the drying unit, fabric is dried at very high temperature. Then it is passes for steaming and washing unit. Procedure :-The cloth is feeded along with the conveyor belt through hot rollers. When it strikes to the belt, it moves forward and prints with different designs and colour with the help of number of screens. After printing, the fabric is passed through drying chamber and then steaming chamber. In this way, continuous printing is achieved. 55

Advantages of Rotary Screen Printing Machine :- Higher production, Continuous printing, Automatic colour feeding arrangement, Design changing is very fast, and Screens are more durable, Disadvantages of Rotary Screen Printing Machine :- Plant cost is more, Only suitable for large production, Cross border or pallu designs can not be printed, Screen production is costly. 56

c. Preparation of screen for rotary screen printing :-Rotary screen printing machine consist screen made up of nickel. These are of two types :- Lacquer stream II) Galvanised stream I) Lacquer stream :-In this stream, at first, clean or degrease the perforated screen by chromic acid (prepared by mixing potassium dichromate and sulfuric acid in 1:2), then coat it with photo sensitive chemicals. After drying the lacquer at low temperature, expose the screen to light for 10 to 20 min. and re-touching is done, where it is required. Then exposed screen is washed in water tank and drying at room temperature. Then hardening process is carried out. Finally, rings at both sides are sticks by gluing. It is technical work. In this, screen design repeat is set according to arrow marks on 57

screen & end rings. Then enter the rings in side the screen ends and stick tightly. 1-5-21 After fitting the rings, squeegee is fit inside the hollow screen and start the machine. There are two types of squeegee; magnetic rod type and blade type. Both types are used, but in general, for light weight fabrics, rod type squeegee is used and for heavy fabrics, blade type squeegee used. Due to sharpness of blade type squeegee, it gives fine design, but tearing of lacquer due to high pressure is the main problem, so generally it is not used in sarees . II) Galvanised stream :-A galvanised screen is prepared as follows:- - A matrix (mould) of a steel cylinder is first prepared, - It is then coated with a greasy chemical which will withstand 58

the action of electroplating. - Then electroplated with nickel with perforation of required size and mesh. -The electroplated shall of thickness of 0.08 mm to 0.2 mm is then removed by impressing the steel matrix in a solution where by the shall is loosened from the surface of the matrix. Then fitting the rings and use it as previous screen. 5. Engraving of design on roller : - One repeat of the design is first transferred to a small roller of soft steel with a polished surface. The dimensions of the die should be such that the circumference of the printing roller is an exact multiple of that of the die, so that an exact number of whole repeats can be transferred on the printing roller. Copper sulphate is used to engraving the design on iron roller. 59

CuSO 4 +Fe →Cu +FeSO 4 A design is drawn on paper with sodium sulphide solution. The paper is then wraped around the moistened surface of the coppered die. A thick canvas piece is wound around it tightly and tied with string and allowed to stand for 1-2 hrs. The design is transferred on to the die in the lines of copper sulphide . It is then engraved with hand in intaglio (seal) under the surface. When the die is fully engraved, it is hardened by dipping in bone ash and a little charcoal. It is then heated to cherry red, plunged into cold water for tempering to required hardness. The die is now placed in a clamping machine in close contact with another small roller of mild steel (mill). The die and the mill are kept revolving under constantly increasing pressure. Now the design in intaglio on the die is transferred 60

in mill. The mill is then hardened as in the case of the hardening of the die. The mill is kept in contact with the printing roller and rotated till the desired depth of engraving is achieved. In order to produce a multi colour design, separate dies are prepared for each colour . The roller is then placed in an etching bath which may contain either dilute nitric acid or ferric chloride which etches on the exposed area only, while the varnish protects the roller surface at the other areas only. 6. Styles of printing viz. Direct, Discharge and Resist on natural fibres :-Styles refers to the manner in which a particular action is performed. For example, the style of walking, style of writing, or style of working refers to the manner in which a person walks, write or work. 61

In the printing, direct, discharge and resist styles of printing are used. i . Direct style :- This style is also referred to as steam style, because in most of the cases, the printed fabric is steamed to fix the colour . In this style, the final design or appearance obtains directly. Most classes of dyestuffs are printed on the fabric by the direct style. Mordant colours , vegetable colours pigments and certain mineral colours are also applied to the fabric by this style. The dyes are printed directly at therequired places of the multi coloured design on the fabric, leaving the other portions white. Some examples of this style is as follows:- 6-5-21 62

a) Printing of cotton fabric with naphthol padding method :- By this method, multi coloured prints can be obtained by using different diazo salts on a single naphthol . The naphthol in the unprinted portion has to be removed completely after printing. Therefore, naphthols having least affinity for cotton have to be used, otherwise it becomes difficult to remove the naphthol completely from the ground after printing to obtain a perfectly white back ground. Naphthol AS, AS-D, AS-OL, AS-TR, AS-RL, and AS-LB are quit suitable for this method. The method is suitable for printing blotch (the designs, which has fullness) designs, because since the printed area is large, less naphthol has to be removed. 63

64

The fabric is first padded with naphtholated solution using more alkali for dissolving than required, because when the dried fabric is exposed to air, the caustic soda present in the cloth gets converted into soda ash due to action of CO 2 in the air. The naphtholated cloth is then dried over heated cylinders or in a hot flue oven. If cloth is dried too slowly or at a very low temperature, it leads to inferior brightness of the final print. The fabric is then printed with a paste containing – 15 pts. - Fast Red TR Base 1oo pts. - Water 15 pts. - Conc. HCl Acid 6 pts. - NaNO 2 8 pts. - Acetic Acid (50%) 600 pts. - Starch (10%) Tragacanth (6%) Total 1000 pts. 65

Acetic acid is used to improve the brightness of the shade. Same as, all the other dyes like direct, reactive, vat, sulphur , etc. can be directly printed on the cotton fabric. Methods and ingredients are changed accordingly. b) Acid dye printing on wool :- Wool is scoured, bleached and then chlorinated before printing. Chlorination makes it anti-shrink and assists wetting and adsorption of dyes. Gum arabic , crystal gum and British gum in mixture with gum tragacanth are used as thickeners. Metal complex dyes and chrome dyes gives prints of high fastness properties, but they do not produce bright shades. Sodium chlorate is used in printing black shades. Wetting agents and acids are used in the paste and chromium salt is added as mordant, when printing chrome dyes. 66

30 parts - Acid dyes 50 pts. - Glycine A 40 pts. - Glycerine 210 pts. - water 600 pts. - British gum and gum tragacanth paste 90 pts. - Acetic acid Total 1000 pts. After printing and drying, the cloth is steamed at 100°C in moist steam for 1 hr. (but not under pressure), then washed and dried. 7-5-21 c) Printing of silk :- Acid and metal complex dyes are more widely used than any other class of dyes for printing silk. It is 67

mainly printed by hand block printing or hand screen printing method. The metal complex dye 1:2 type of dye Luganil FB have very good solubility in water, excellent all-round fastness properties and high tinctorial power. Ammonium sulphate , ammonium oxalate and ammonium taaratret are used as acid liberating agents for fixation of the dye. Acetic acid or glycolic acid is also used for the same purpose. Gum arabic is used traditionally as a thickener, but now locust bean gum or derivatives of guar gum like meyprogum is used along or in mixture with British gum. Recipe:- 50 pts. Acid or metal complex dye 40 pts. Solvent ( Glyezin A) 200 pts. Hot water (first boil then cooled) 600 pts. Gum Arabic (1:1) or crystal gum (1:3) 68

Printing of silk with Acid Dye 69

20 pts. Ammonium oxilate (acid liberating agent) 20 pts. Glacial acetic Acid (acid liberating agent) 20 pts. Water 1000 pts. Total Procedure :- Print the fabric as per mix the above chemicals. Then dry and steamed at 100°C- 102°C in a star ager for 1-2 hrs. Then rinsed well in cold water and dried. In the case of metal complex dyes, no further treatments is necessary. ii. Discharge Style of Printing :- Discharge means to remove or reduce the colour from the fabric. In this style, the first need is a dyed fabric which is to be discharged. A classical discharge print is obtained, when a fully dyed fabric is printed with an agent, which will chemically destroyed the ground shade and produce a white discharged fabric. If a dye is used on discharged place, which is stable to the discharging agent, 70

then it is known as colour discharge printing. It is obtained simultaneously destroying the ground colour and fixing the stable dye onto the fabric. The discharging agents may from oxidising substances such as potassium chlorate or potassium dichromate for discharging indigo to the more useful reducing agents such as sodium bisulphite , tin chloride, sodium hydrosulphite , and its stabilised compounds such as Rongalite C, and Safolin . Sodium bisulphite is used in discharging naphtholated ground, combined with zinc dust and also used for discharging acid dye from the silk. A great advantage of this printing is that it allows of white and coloured patterns being produced on dyed ground. It enables production of coloured blotches with sharp outlines, generally 71

difficult to obtain by the direct style. The demerit of this style is that only those colours which can be discharged have to be used since all colours are not dischargable . White discharge print on azoic dyed ground cotton fabric :- At first, cotton fabric is naphtholated by naphthol , then diazotised . The naphthol colour should be dischargable by the discharging agent to be used. The fabric is printed with :- 200 pts. Rongalite C (Discharging agent) 200 pts. ZnO (1:1) (For getting pure white) 80 pts. Solution Salt B (For getting pure white) 60 pts. Potassium Carbonate (For getting pure white) 410 pts. Starch tragacanth 1000 pts. Total 72

After printing, the fabric is dried and steamed for 5 minutes in a steamer at 100°-102°C and then treated in a boiling solution of 2 g/l soda ash (Na 2 CO 3 ) for 5 minutes, then soaped and washed . b) Coloured discharge with vat dye :- coloured discharge can be obtained with ease on azoic ground except in the case of naphthol AS-G and AS-TR combination. 30 pts. Anthraquinon Vat dyes 100 pts. Glycerine 660 pts. Starch tragacanth paste 120 pts. Potassium carbonate 100 pts. Rongalite C 1000 pts. Total Procedure :- print the fabric, then dried and steamed for 5 min. 73

Coloured discharge with vat dye 74

in a steamer at 100°-102°C and then rinsed. The vat dye is oxidised by treating the fabric with sodium perborate and acetic acid of 50%, 40g/l and 6-12 ml/l respectively. Then soaped, rinsed and dried. 8-5-21 c) White discharge and colour discharge effect on silk :- Silk dyed with dyes that can be destroyed with discharging agent. Zinc dust and sodium bisulphite , Rongalite C, Tin chloride and thiourea dioxide are used as discharging agents. Titanium dioxide and zinc oxide are used as white pigments to improve the white effect. White discharge print using zinc dust and sodium bisulphite :- 300 pts. Zinc dust 50 pts. Water 150 pts. Sodium bisulphite 75

500 pts. Crystal gum paste or gum arabic (1:1) 1000 pts. Total White discharge print with Rongalite C 50 pts. Urea 40 pts. Thiodiethylene glycol 150 pts. Rongalite C 75 pts. TiO 2 or ZnO 600 pts. Thickener 85 pts. Water 1000 pts. Total Procedure- print, Drying immediately, steaming for 1 hr., then rinsing, soaping, rinsing and drying 76

White discharge and colour discharge effect on silk 77

Colour discharge print using Zinc dust and Sodium bisulphite 40 pts. Non dischargable acid dye 30 pts. Diethylene glycol or glyodate B 20 pts. Urea 120 pts. Zinc Dust 60 pts. Sodium bisulphite 600 pts. British Gum 130 pts. Water 1000 pts. Total Procedure- print, Drying immediately, steaming for 1 hr., then rinsing, soaping, rinsing and drying. iii. Resist Style of Printing :- This style related to the production of white and coloured pattern on variously coloured ground. Difference is that the discharging agent is applied to the cloth after 78

It has been dyed. Where as in the resist style, the resisting agent is applied to the cloth before it undergoes any dyeing. Famous tie and dye process and Bandhani printing are the examples of resist style. In discharge style, sharp outlines obtained, chemical action required, it is costly, the ground should be dyed and percentage of rejection in this printing is higher. In resist style, outlines are dull, it may be mechanical or chemical action, it is cheaper, ground may be dyed or dull in shade and rejection percentage is less. i ) White resist on cotton using azoic ground :- fabric is padded with naphthol solution and dried. The padded fabric is then printed with :- 79

White resist on cotton using azoic ground 80

100 pts. Tartaric acid 400 pts. Stanuous chloride 500 pts. Starch tragacanth 1000 pts. Total Print the fabric, then dry and diazotize it. Then washed soaped in boiled water, then washing and drying the fabric. 13.05.21 ii) Coloured resist on cotton :- A combination of vat and azoic shades on an azoic background can be produced by adding Rongalite C to the resist paste. The fabric is padded with naphthol solution and dried. It is then printed with :- 150 pts. Vat dye paste 30 pts. TRO 81

Coloured resist on cotton 82

450 pts. Starch tragacanth 75 pts. Potassium carbonate 100 pts. Rongalite C 30 pts. Urea 115 pts. Water 50 pts. Potassium Sulphate (90° Tw ) 1000 pts. Total Urea is added to eliminate reducing vapours evolved from Rongalite C which would otherwise affect the ground shade. Print the fabric, then dry it. Then steam and diazotize for develop the naphthol . Then rinsing, soaping, again rinsing and drying is carried out. iii) Wax Resist on silk :- The silk fabric is stretched over a Batic 83

frame and waxed by means of a Batic pen or brush. The temperature of the wax being maintained between 50-60° C using paraffin wax to bees wax in 1:3 ratio. After the wax has hardened the fabric is dyed with dyes dyeable below 50° C. Dyeing is carried out from the lightest to darkest shade so that the darkest tones are built up gradually. For obtaining crackled effect, the cloth is crushed and immersed in the dye bath. -----xxx----- 84

Unit III 7.Styles of printing viz. Direct, Discharge and Resist on synthetic and their blends Polyester, nylon, acetates and acrylic fibres are synthetic fibres and their printing is different from the natural fibres. Some styles with different fibres and their blends are given here. A. Printing of Polyester :-For printing the polyester, the dyes which are marketed in the liquid form are more suitable than other because they contains less dispersing agent and are finally dispersed so that they can be readily mixed with the print paste without pre dispersing. It is not possible to obtain full colour value if the dyes contain large amount of dispersing agent. Therefore, dyestuffs containing very small amount of dispersing agent are used. Some trade names are Foron P 85

(Sandoz), Terasil X dyes (Ciba Geigy ) etc. i ) Direct style of printing :- The fabric is printed with a paste containing 100 pts. Disperse dye in liquid form 175 pts. Water 700 pts. Meyprogum thickening (5%) or Locust bean gum 5 pts. Sodium Chlorate 20 pts. Citric acid (For adjust pH between 5.5-6) 1000 pts. Total After printing, the fabric is dried carefully and the dye is fixed by one of the following three methods :- a) Thermo-fixation :- Fabric is subjected to hot air at 210°C for 1 min. The fixation is carried-out in a backing oven or on stenter . 86

b) Super-heated Steaming :- In this process, live steam at atmospheric pressure is raised from 100°C to 180°C by bringing it in contact with radiators which are heated at 200°C by oil heating or electrical heating system. c) High pressure steaming :- The steaming is carried-out under pressure in a kier at 0.5 kg/cm 2 pressure after driving out all the air and condensate from the kier. It gives good colour yield, bright prints and smooth feel. 15-05-21 ii) Discharge style of printing on polyester :- It is very difficult to discharge a fully dyed polyester fabric, because in the course of the dyeing, the disperse dye dissolves in the fibre and becomes so firm that very high energy is required to destroy it. If the dyeing is carried-out by HPHT method, it is impossible to discharge it. But if the ground shade is obtained by dyeing, the fibre with the use of carriers at atmospheric pressure, it is 87

easy to discharge, but it is preferred to apply a discharge paste on an unfixed ground than on a dyed ground, i.e. print by the over printed resist or discharge cum resist method. The cloth is first padded with a dispersion of the dye and dried at a low temperature so that the colour does not get fixed at this stage. It is then printed with a discharge paste followed by drying and steaming under pressure or steaming with superheated steam, when the ground colour is fully developed and the dye at the printed portions gets easily destroyed. For obtaining a coloured discharge, a non- discharg able disperse dye is used. a) White discharge on a fully dyed ground :- A classical white discharge on polyester cloth dyed with disperse dye by the carrier method is obtained by printing the fabric using the 88

following method :- 200 pts. Safoline (Zinc Sulphoxilate formeldehyde ) 400 pts. Meyprogum paste 5% 100 pts. Carrier ( p -phenyl phenol) 50 pts. Zinc Oxide 250 pts. Water pts. Total After printing and drying, steaming under 0.5kg/cm 2 for 30 min. or steamed in a high temp. steamer at 180°C for 8 min. then reduction cleared , soaping and drying. b) Coloured discharge on polyester with SnCl 2 :- For obtaining coloured discharged, the above paste (as given in above heading a ) is used, but omitting TiO 2 and optical brightener and incorporating in it a non- dischargable disper - 89

se dye (50 pts.) The above methods are applicable to not only polyester cloth, but also to polyester / cellulosic blends. The blends can be carbonised after printing. Reasons to use Safolin instead of Rongalite C It is much less hygroscopic than Rongalite C and hence does not cause bleeding and haloing ( white out-line surrounding the design due to more absorption of moisture during steaming). It is effective in mild acidic conditions in which disperse dyes are applied whereas Rongalite C is sensitive to acids and is effective only under alkaline conditions. Disperse dyes are sensitive to alkaline conditions at high temperature, therefore Rongalite C is unsuitable. 90

iii. It has comparatively better stability than Rongalite C, which has poor stability, iv. It has high reducing power and can discharge a good number of disperse dyes. 20-5-21 iii) Resist style of printing on polyester (Alkali Resist Process):- Polyester fabric is padded in a dispersion containing 50 pts. Dispersol PC dye, 5 pts. Citric Acid 100 pts. Sodium alginate paste ( Manutex RS 5%) per lit. & dryed at 100°C. It is then printed with 600 pts. Meypro gum paste 5% 100 pts. Glycerine 102 pts. Soda ash or 8 pts. Caustic Soda Total 1000 pts. 91

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Mechanism of printing :- When polyester fabric is padded with a dispersion of Dispersol PC dye, the dye is not fixed at this time. After drying is over, fabric printed with a paste containing soda ash or caustic soda, the dye in the printed portions gets saponified and is makes ineffective due to the presence of alkali with the result that the printed portions remain white when the dye in the remaining portion of the fabric is fully developed or fixed by high temperature steaming or by thermo soling. A coloured resist is produced by incorporating an alkali-resistant disperse dye in the print paste. 199 93

The fabric is then dried at 110°C and steamed with super heated steam at 180°C for 1 min. Then reduction cleared, soaped with a detergent, rinsed and dried. B. Printing of polyester-cellulosic blends :- During printing of blends, it should be keep in mind that which component is small and which one is large? If the polyester-cotton blend contains less than 15% cellulose portion, then disperse dyes alone can be used especially for light to medium shade and the dye fixed by the usual method viz. thermo fixing, steaming or steaming under pressure. Single stage method and two phase method are uses to print blends. Single Phase Method :- a) Printing with pigments :- The most essential ingredient in the pigment print paste is the binder. Polyurathane , acrylonitrile 94

butadiene and styrene butadiene are used. The curing of the fabric after printing is done by radiation heat. Recipe – 100 pts. Pigment dispersion 200 pts. Binder 695 pts. Emulsion thickener 5 pts. Acid liberating salt 1000 pts. Total After printing and drying, the fabric is cured at 160°C to 170°C for 5 minutes and washed. b) BASF Method :- A stock thickening is first prepared as under- 95

Recipe- 400 pts. Sodium alginate paste 10 pts. Resist salt L 5 pts. Citric acid 10 pts. Calgon T (Thickening agent) 200 pts. Starch ether paste 10% 10 pts. Urea bulked (Hygroscopic agent) 1000 pts. Total The fabric is then printed with a paste containing 100 pts. Cellestrene dye ( Colouring Matter) 700 pts. Stock thickening 100 pts. Glyezin CD (Dye fixing Agent) Print-dry- thermo-fixing at 210°C for 1 minute, rinsing, soaped with detergent, rinsing, and dried. 96

ii) Two Phase Method :- In two phase method, combination of two classes of dyes is mainly used i.e. disperse-reactive or disperse-vat combination. In the first stage, the disperse dye is fixed and in the second stage, reactive or vat dye is fixed. The disperse dye is fixed by thermosol or steaming process under pressure and the reactive dye is fixed by silicate padding method. Vat dye is fixed by flash- ageing after padding the printed material with alkaline hydrosulphite . Disperse-Reactive combination :- The fabric is printed with a paste containing 50 pts. Disperse dye 50 pts. Reactive dye (Vinyl Sulphone type) 700 pts. Emulsion thickening or modified locust bean gum 10 pts. Resist salt L 97

2 pts. Wetting agent 2 pts. Acetic acid made up to total 1000 pts. 21-5-21 After printing, the fabric is thermo-fixed at 210°C for 1 minute. The fabric is then padded with sodium silicate (106°Tw) and batched for 12 hrs. to fix the reactive dye. Then rinsed first with cold water to remove the hydrolysed reactive dye as much as possible, then rinsed with hot water (75°C) to remove more of the hydrolysed dye and alkali from the printed fabric. Finally, soaped, rinsed and dried. b) Disperse vat combination :- The fabric is printed with a paste containing 100 pts. Disperse dye (liquid form) 50 pts. Vat Dye (paste form) 98

30 pts. Glycine A 10 pts. Ludigol 110 pts. water 700 pts. Lucust bean gum 1000 pts. Total After drying, the fabric is thermo fixed at 210°C for 1 min. on a stenter , whereby the disperse dye is fixed. It is then padded in a solution containing 100 pts. Caustic soda (50%) 60 pts. Soda ash 60 pts. Sodium hydrosulphite 60 pts. Sodium chloride 1000 pts. Total 99

after padding, fabric aged at 125°C for 45 seconds, rinsed in cold water and oxidised with hydrogen peroxide 35% (40 ml/l) and acetic acid 50% (40 ml/l) at 60°C. Then rinsed with hot water, soaped at 80°C for 20 min. with NIN, rinsed, and dried. c) Discharge printing on Polyester/ Wool Blends :- For this discharge, the polyester component is dyed below 105°C using the carrier method. The wool component is dyed with acid or metal complex dyes. Safolin is used as discharging agent for producing white discharge effect. Recipe for white discharge :- 80 pts. Safolin 100 pts. TiO 2 5 pts. Tartaric acid 50 pts. Polyglycolic acid 600 pts. Thickening paste 5 pts. Optical whitening agent 100

Coloured discharge is produced by printing the blend with a paste containing the same ingredients as above, but stannous chloride is used as discharging agent. TiO 2 and Optical whitening agent are not used, but non dischargeable disperse dye and non dischargeable acid dye (50 parts each) are used. The fabric after drying is steamed under pressure for 30 minutes in a star ager, rinsed, soaped with a detergent, rinsed and dried. 22-5-21 d) Discharge printing on polyester /Acrylic blends :- At first, the ground is dyed. The polyester component is dyed with disperse dye using a carrier and the acrylic component is dyed with modified basic dye. Then print the fabric with:- 80 pts. Stannous Chloride (for white discarge ) 100 “ TiO 2 101

10 pts. Tartaric acid 40 “ Sodium Acetate 50 “ Polyglycolic acid 5 “ Optical Whitener 600 “ Thickener 1000 “ Total Coloured discharge is produced by printing the blend with a paste containing the same ingredients as above, but TiO 2 and optical whitening agent are not used. A non dischargeable disperse dye and non dischargeable modified basic dye (50 pts. each) are used. The prints are fixed in the same manner as the polyester wool blend followed by washing and soaping. 102

e) Printing of acetate rayon :- Recipe :- 200 pts. Disperse dye (Paste) 100 “ Zinc thiocyanate (for better penetration) 50 “ Triacetin (Wetting Agent) 350 “ Crystal gum paste 300 “ Water 1000 “ Total Print- drying- steaming in an Festoon steamer or star ager for 1 hr. at atmospheric pressure- rinsed in cold water and soaped at 40°C with 2 g/l detergent. Rinsed and dried. f) White Discharge print on Cellulose Acetate and Triacetate :- The fabric is dyed with a dischargeable disperse dye and then printed with the following paste :- 103

500 pts. Thickener paste 50 “ Glycerine (Solvent) 120 “ Water 250 “ Safolin (Discharging agent) 50 “ Sandotherm ACS 30 “ Citric acid (1:1) (for acidic pH) 1000 “ Total After printing, the fabric is dried and steamed at 100°C to 102°C for 20 minutes, for triacetate , it is steamed for 20 minutes under pressure (0.5 kg/sq. cm.). Rinsed thoroughly, soaped with a detergent at 40°C for 10 minutes. Then rinsed, and dried. Coloured discharge :-The Dyed ground is printed with the 104

following paste :- 570 pts. Thickening paste 100 “ Water 30 “ Glycerine (Hygroscopic Agent) 50 “ Sandotherm ACS 20 “ Wetting Agent 30 “ Disperse Dye (Dye for design portion) 200 “ Tin Salt (Discharging Agent) 1000 “ Total After printing, fabric is steamed for 20 minutes, rinsed, soaped with a detergent at 40°C for 20 minutes, then rinsed and dried. 27-05-21 105

g) Printing of nylon Acid dyes and metal complex dyes are widely used for printing nylon fabrics. Acid dyes gives brilliant prints, metal complex dyes do not produce brilliant prints, but they give very high fastness properties. Disperse dyes give poor fastness to washing. Recipe: 50 pts. Acid dyes or Metal complex dye 50 “ Urea (For increase colour yield) 50 “ Thiodiethylene glycol (Solvent) 50 “ Cold Water 195 “ Boiling water 600 “ Crystal gum paste (2:3) or gum Indalca paste 5 “ Ammonium tartarate (Acid liberating agent) 1000 “ Total 106

Print-Drying-Steaming at 100°-105°C for about 40 minutes, rinsed with cold water and then hot water containing little amount of ammonia solution to prevent staining. Then dried. h) Printing of acrylic 50 pts. Cationic (Basic) Dye 335 “ Hot Water (For Paste) 50 “ Glycine A (Solvent) 50 “ Benzyl Alcohol (Swelling agent) 550 “ Crystal gum (2:3) 5 “ Tartaric acid (Mild acid for acidic condition) 10 “ Thiourea (For remove reducing fumes) 1000 “ Total Print- Drying -steaming in a star ager for 30 minutes-at 103°C-washed with cold water-soaped in NIN at 60°C rinsed and dry. 107

Printing of Acrylic/Cellulosic Blends 50 pts. Disperse dye (For Acrylic printing) 50 “ Reactive dyes (For Cellulose printing) 5 “ Wetting Agent 275 “ Water 500 ” Sodium alginate (6%) 100 “ Urea (Hygroscopic Agent) 20 “ Sodium bicarbonate (added just before the printing) 1000 “ Total Print- Drying- Steaming for 30 min. under pressure (0.5 kg/sq. cm.) – washing-soaping with a detergent at 60°C for 5 minutes first with hot water then with cold water and dried. 108

j) Printing of Acrylic / Wool Blend 100 pts. Basic Dye 30 ” Thiodiethylene glycol (Solvent) 200 “ Water 10 “ glacial acetic acid (for acidic pH) 10 “ Sodium Chlorate (counteract the reducing influences on the dye ) 650 “ Thickening Sodium Alginate (6%) 1000 “ Total Print- drying- Steaming at 103°C for about 30 minutes, in a star ager-rinsed in cold water-in hot water-soaping with detergent at 60°C for 5 minutes, rinsed first with hot water and cold water and dry. 3-6-2021 109

8. Machines used for printing, drying, steaming, and curing. Drying Machines :- After printing, the fabric is dried to remove the moisture applied from the print paste. For obtaining good printed mark and prevent the printed goods from marking-off during handling between printing and subsequent processing operations, drying process is essential. The rate of drying may be important particularly if the fabric being printed has a low moisture regain. In printing industry, sun drying is used at cottage industry level. Hot air blowers, radio frequency dryer or stenter are used for drying in textile industry. i ) Hot Air Drying Machine :- In this machine, as the fabric is transported in long loops over rollers in the drying chamber, it is not free from tension and creases. This machine is based on 110

old hanging room, consists of cloth bearing poles moving along on a pair of conveyor chains. Fabric dry with the help of hot air current. 111

ii) Stenter :- Hot air stenter not only dry the fabric, but also controls the width of the cloth. Single layer stenter is the most widely used particularly for cotton, silk and linen. Multi layer stenter is used for wool drying on account of the greater amount heat necessary for drying the thicker material. The machine varies in length from 20 to 40 mts . and dries the cloth at the rate of 140 mt . per min. iii) Radio Frequency Drying :- The process is applied in two ways:- a) surface heating of conducting materials and b) uniform heating of insulating materials i.e. dielectric heating. In dielectric heating, the wet cloth is placed between two electrodes connected to a high frequency circuit. The high frequency current generates dielectric losses through out the entire mass of the material and produces heat instantly which results in uniform drying. 112

B. Ageing :- 113 After printing and drying, the dyestuff and chemicals, present in the dry thickener film deposited on the cloth surface and the dye is not yet transferred to the cloth. This is done by either ageing or steaming. Ageing consists of exposing printing goods to action of steam at atmospheric pressure to assist in the diffusion and fixation of the dyes. This can be done by the following ways :- By hanging the goods in large rooms, By passing them through an ageing chamber continuously, & By a short steaming in a continuous steam ager. The ageing room may be 25-60 feet in length and the printed cloth may be hung in long loops from a series of wooden bars. The heat is supplied from steam pipes arranged at the base of the walls. Goods may be keep In the ager for 1-6 days. 04-06-2021

Mather and Platt Rapid Ager :- For large production, ageing has 114

to be done in a short time. The said ager consists of an iron chamber, inside which top and bottom guide rollers are provided. A wooden hood at the top arranged to carry off the fumes produced during ageing. A steam pipe runs into this hood. The cloth to be aged enters and leaves the ager through the same hole, which is provided with two steam-heated pipes fixed parallel to the weft yarn of the fabric being aged. These prevent the formation of water drops from steam and falling on the cloth. The cloth is supplied with low pressure steam through a perforated pipe placed beneath the lower series of guide rollers. The condensed water formed runs down the sides of the chamber and Siphoned out. The temperature of Ager kept at 65°C to 95 and time of ageing about 3 min. at the speed 60 yds . per min. 115

C Steaming :- This consists of submitting printed fabrics to the action of steam for varying periods at various pressure. High pressure steamer is made in various sizes, upto 9 ft. diameter and 12 ft. in length. Pressure keep about 30 psi and is provided with a cavity roof in which steam of a higher pressure is admitted. A perforated steam pipe is fixed at the bottom of the cottage which is provided with the necessary steam valves like safety valves, pressure gauges and condensed water valves. The wagon loaded with loops of printed fabric is run into the pre-heated steamer, the door closed and tightened with bolts. Steam is turned on and allowed to exhaust for some time to prevent any air pockets from forming. The exhaust is closed and the pressure allowed to develop. Steaming is carried out for 1 to 1-1.5 hrs. then the steam is turned off, the exhaust opened, the door opened and 116

the carriage removed. The pressure in this steamer is kept up to 30 psi. Star Ager :- It is commonly used Ager or Steamer, in which the printed cloth is loaded on to star frames, which are placed inside the pressure steamer. The pressure is raised to the desired level and maintained therefore the required time (1 hour) like the cottage steamer. This also works in a batchwise fashion. Due to frequent need for the pressure to be released as one batch is finished and then built up again for another batch, steam consumption is very high. D. Curing :- Curing is a process subjecting to the fabric to dry heat in a suitable chamber for a short period. It is usually carried out at 140 °C- 150° C for a period of about 5 min. During this process, the binder or resin present in the fabric is 117

set or polymerised forming a film durable to laundering or dry cleaning and resistant to degradation and chemical attack depending on the type of binder used. The most- commonly used reactive monomers are acrylamide and N- Methylol acrylamide . The curing operation is carried out in a hot-flue oven or a chemical heated by electric heaters or infra red heaters. Guide rolls are provided in the chamber to carry the fabric forward in open width. A stenter heated to the required temperature can also be used. In case of pigment printing, the fabric is cured at 140°C. for 5 min. 5-6-21 118

Unit IV 9. Novelty (New) printing process :- Novelty printing process are the processes, which are investigated during few years ago. The Ink Jet printing and xerography are such type processes. A. Ink Jet Printing :- Ink jet printing is a non-impact printing method, projecting drops of ink onto the surfaces to be printed. Ink jet printing is classified as per next page. Continuous Stream (CS) :- In this system, ink is forced at a high pressure through a small jet (nozzle). The emerging stream of ink is broken into small droplets. These droplets can be selectively charged and deflected while passing through high voltage plates. In the Raster Scan Method, the charged droplets are deflected onto the substrate in a predetermined 119

manner and the uncharged droplets collected in a feed tank and recycled. This is referred to as Raster Scan Method. In the second method (Binary Jet System), both uncharged droplets from the image and the charged droplets are deflected to feed tank. Ink Jet Printing ↓ Coarse Resolution (Up to 40 dpi) Fine Resolution (Up to 300 dpi) ↓ Continuous Stream(CS) Drop on Demand (DOD) ↓ ↓ Raster Scan Binary Jet Piezoelectric Bubble jet Method System Transducer Type 120

High purity Procion P dyes are used in ink jet printing. These are of monochloro -s- triazinyl group, which reacts under hot alkaline conditions with cellulose to produce a covalent dye-fibre bond producing prints of excellent fastness. As per fig. a dye formulation is pumped at a constant pressure through a nozzle of 14.4 µm diameter. The continuous stream is broken up into droplets by modulation at 625 kHz, i.e. 6,25000 droplets of colorant are formed per second. As the droplet train then enters an electrical field between two 1500 Voltage plates, charged droplets are deflected, picked up and fed back into the colour container for recycle. Uncharged droplets pass through the deflection plates and reach the substrate in the desired pattern in an area covering only 0.1 mm x 0.1 mm or one pixel and thus producing smooth continuous tones. 121

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B. Xerographic Printing :- Textile colour xerography is a feasible route to waterless & complex printing of fabrics with pigments and binders. This system is computerized, fast style and colour changeover are possible. The metal that is electrically grounded is coated with a layer of photoconductor (PC). The basic steps of this printing are as follows :- Charging :- Charging the surface of the PC which will hold a charge in the dark. The charging is usually accomplished by passing a corona over the PC surface. 10-6-21 Exposing :-The second step involves producing a latent electrostatic image by exposing the PC to light. Since the light causes the PC to become conductive, charge is drained from the surface in regions that are exposed. This step is usually accomplished reflecting light from an original or passing light through a transparency onto the PC surface. 123

iii) Developing :- The third step is developing the latent image by placing toner (pigment plus binder) in regions where electrostatic charge is located. Development involves the use of a developer system composed of carrier and toner. The carrier beads are normally much larger in size than the toner particles. The triboelectric characteristics of the toner and carrier are such that when they are thoroughly mixed, they become oppositely charged and attract each other . The carrier is oppositely charged from the PC surface. When carrier, which holds tonner on its surface is brought into contact with the PC, the toner is attracted to the charged regions of the PC. Transfer of toner to these regions on the PC develops the image. iv) Transferring of the developed image :- The fourth step is the transferring of the developed image to the substrate being 124

printed. The substrate is brought into contact with the PC. The back of the substrate is strongly charged, usually by using a corona, so that the toner transfers to the surface of the substrate. v. Fixing :- The fifth step is fixing the toner to the substrate. The temperature of the toner is raised causing the resin binder to flow. Pressure is often used as well as a heat source. vi. Cleaning :- Following fixation, the surface of the PC is cleaned and the process is repeated. 10-06-21 The major technical barriers associated with the use of xerography to print textiles are :- i . Lack of tonners designed to give desired textile properties, ii. Low tonner transfer efficiency to fabric, and III. Unavailability of machinery specifically designed for textile printing. 125

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10. Transfer Printing of Synthetics and cotton :- It is an indirect method of printing in which a suitable dye is transferred from paper to a thermoplastic fabric under controlled conditions of temperature, time and pressure. It is also called vapour phase printing and dry heat printing. The advantages of this printing are as follows:- a) The desired pattern is printed on good quality paper with the ink made from disperse dyes which are volatile means sublimation fastness of dye must be poor. This is a vital step in the transfer printing process. b) In the second stage, the pre-printed release paper is placed on the fabric and heat and pressure is applied to the back of the paper, whereby the dye on the paper sublime and diffused into the fabric, which is in a plastic condition at 180-220°C 127

within 20-30 seconds. After the dye is transferred, the paper is removed from the fabric, which does not need any further treatment. Three Type machines are used for transfer printing :- A. Flat bed press transfer printing, B. Continuous calender or drum transfer printing machine C. Vacuum transfer printing machine A) Flat bed press transfer printing :- In this machine, the fabric or garment is placed on the press bed and the pre-printed released paper is placed on it. It is then hot pressed between 180-220°C for 20-30 sec. Thus the pattern on the printed paper is transferred on to the fabric or garment, which is then removed from the machine. 128

B. Continuous calender or drum transfer printing machine :- In this machine, the fabric and the pre printed release paper pass in close contact with each other round a large cylinder or drum (0.5 to 2 mt . in diameter). They are held in contact by 129

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means of an endless blanket under tension. The temperature of cylinder is electrically maintained up to 220°C and the fabric in firm contact with the paper is passed or transferred over it for 15-20 seconds. Thus the pattern on the paper is transferred on to the fabric. The operation is continuous. This machine produces about 15 mts . per minute. 11-06-21 C. Vacuum transfer printing machine :- In the vacuum transfer printing machine, transfer of pattern is effected under vacuum in the vacuum chamber of the machine. The principal of this machine is that a matter under reduced pressure boils or sublimes at a temperature lower than atmospheric pressure is applied to transfer printing and transfer is effected by subliming the dyestuff at a lower temperature i.e. between 130°C to 180°C under reduced pressure. The paper and the fabric are held against a 131

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perforated drum by internal vacuum. Heating is done from outside by Infrared radiation and since no pressure blanket is used, there is no flattening of the fabric. This printing permits the use of a wider number of disperse dyes, the penetration of the dyestuff is very good and the colour fastness of the printed material is improved. Transfer printing produces some novel effects. For this, an absorbent paper or fabric can be dyed with the disperse dye by dipping in the dye liquor, dried and cut into various shapes. These pieces can be placed between two layers of polyester fabric and hot pressed. The dye will be transferred on to the fabric and the pattern will be reproduced on it. Using this technique, a variety of design may be produced. 133

11. Flock Printing :- Flock means a mass of short fibres or fibre dust. In flock printing, the fibre dust or mass of fibres ( very short fibers, length about 0.1-0.3mm) are fixed onto the cloth by means of an adhesive to form a printed pattern. It produces a pile or velvety effect on the fabric, similar to the pile obtained by the loom. In the flock printing, the fabric is first printed with an adhesive paste containing a synthetic polymer which is self reacting, i.e. containing reactive monomers, which crosslink to form a three dimensional network within the polymer film. Besides antifoaming agent, like silicon, a plasticiser , a thickener, a catalyst like DAP, melamine formaldehyde to lower the curing temperature and glycerin to prevent the adhesive from drying prematurely are used. The polymers commonly used as binders contains the monomers acrylamide and N-methanol 134

acrylamide . When the whole fabric is to be flocked, the process is known as flocking, in which the adhesive is applied by a doctor blade to the fabric. The fabric is then dried by stenter or R F dryer and cured at 150° C. A. Electrostatic Method :- In this method, tiny particles of flock are charged with high voltage (Tension) electricity while the surface of the fabric is earthed, thus forming two electrodes having a high electrical potential difference between them. The flock before feeding it through hopper is treated with ammonium chloride solution to render it more conductive and also to minimise the adhesion of one fibre to another. The flock so treated is then fed from the hopper and spread uniformly over the positively charged surface of the printed portion of the cloth by means of a revolving brush. The electrical force orients the fibres in a perpendicular direction 135

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to the fabric surface and fixed them into the adhesive in that state with the result that a thick pile is produced. After printing and drying, the fabric is cured in a hot chamber at 150° C for 5 minutes. 17-06-21 ii) Beater Bar Method :- In this method, the coated fabric is held tight on a conveyor belt, the flock is fed to the cloth by means of hoppers. The cloth is rapidly beaten by beater bars and vibrated to make the fibre stand on ends and become firmly fixed in the adhesive. The beater bars below the cloth rotate rapidly and rub against the backing material, thereby generating static charge which makes the fibre stand on ends . The unfixed flocks are removed by means of vacuum suction. In this method, flock density is low, so a thick pile is not produced. After printing, drying and curing at 150° C for 5 minutes is carried out. 137

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12. Garment Printing :- Cloths ready to wear are known as garments. Some fancy effects are provide to garments for improving their attractiveness and beauty. These as followed:- A. Foam or raised printing :- The raised effect in the printed portion of the garment can be imparted by using raise binder (blowing agents like Bis-carbonamide ) along with usual pigment printing binder, which liberate nitrogen during curing. The liberated gas raised the polymeric film by one-eight to one forth inch (1/8”-1/4”) at the printed portions. The print acquires the embroidery look. If we add normal pigment colours in the printing paste, a coloured raised effect produces. The flouroscent pigment should not be directly mixed with foam binder rather it should first be pasted with the usual binder and the paste may be mixed with raised binder to get uniform print. Curing temp. should be 150-160 ° 139

C for 15- 30 minutes. B. Leathery or plastic printing :- This effect on garments can be introduced by using binders based on polyurethane. This will give shiny and leathery effect with some stretchability thus giving fancy look to garments. C. Khadi Printing :- This is widely used for printing on dark shades. A recipe for printing on dyed ground is as under:- TiO 2 - 60 grams Binder SLN - 50 grams Urea - 02 grams (NH 4 ) 2 SO 4 -02 grams Glycerine -02 grams Emulsion Thickener - 02 grams, Total 200 grams 140

Procedure :-Dyed fabric→ Dry →Print→ Cure (140°C for 7- 5 minutes. D. Metallic print (Gold, Silver, and copper print) :- Gold prints are obtained by using bronze powder, silver print are obtained by aluminium powder and copper prints are obtained by using copper powder. The particle size of the metallic powder are very important as they have to pass through the screen of appropriate mesh. These prints are produced on dark grounds. The concentration of the metallic powder required usually varies from 15-25%, depending upon the hiding power of powder. The metallic powder are mixed with thickened boiled linseed oil or varnish and then printed. In printing, aqueous binder system is used. The printing sequence is as usual- Print →Dry→ Cure (150°C for 3- 4 minutes. Ammonia and sulphur affects the bronze or copper 141

print, so their contaminations should be avoided. 18-6-21 E. Luminiscence printing :- These prints are obtained by incorporating luminiscence colours in the printing paste. The especiality of these colours is that they glow when light falls on them in the dark. F. Reflective printing :- It involve the incorporation of tiny mirror particles in the adhesive. Thus when light falls on it, particularly in night, it gets reflected and thus giving a sort of glitterring effect. G. Fluoroscent Printing :- Fluoroscent derives from their ability to absorbe ultra-violet and visible light and re-emit it at visible wavelengths. This has the effect that the brighter colour bring reflected from the surface than would be expressed from normal light incident upon it. They are only of value, when 142

they are observed under a strong source of day light. ZnS , CdS , and ZnS crystals can store uv and visible light and re-emit in the visible region when the source is removed. It is used in the acrylic systems or in vinyl acrylic top coats as novelty coatings for various commercial products. H. Pearl Printing :- Silver and gold pearl powders can also be used for the printing on garments. They produce better shine than metallic printing. The application procedure is same as that of metallic powders using aqueous binder system. I. Glitter Printing :- It is obtained by using glitter powder, particle size of which is higher than metallic or pearl powder. They are used with suitable binder system. 13. Pigment Printing :-Pigments are coloured or colourless substances inert and insoluble in aqueous and resinous 143

media and having no preferential affinity to the substrate on which they are applied. Pigment, binders, thickeners catalyst and cross linking agents are the main ingredients of printing paste. Pigments with highest possible concentration and having minimum tendency to crust formation are used. They are marketed under trade names like Acramin colours , Acron colours , imperon colours etc. Binders are film forming material having high molecular weight. It forms a film on the surface of the fabric on drying and curing. Most of the commercial binders used are copolymers. Actually, there is no chemical bonding between the binders and the fibres, but only a physical bond exists in between the two. Acramin SLN, Primal TR-42, FC-44 are some trade names. Thickeners :- Conventional thickeners sticking to the fabric or 144

entrapped in the binder film remain water soluble even after fixation has been effected. They also form a hard film loading to stiff handle. An emulsion thickener meets all the necessary requirements of a suitable thickener. An emulsion is a dispersion of one liquid into another in which it is immiscible. An emulsion is a dispersion of one liquid into another liquid, in which it is immiscible. An emulsion contains a third substance viz. water-oil (W/O) and oil-in water (O/W) type. Systems containing less than 25% water usually form W/O type emulsions, whereas those containing more than 31% water usually form O/W type emulsions. Both are used in printing. 19.6.21 Catalyst :- These are used to accelerate cross-linking of the binders and to facilitate the reaction between the binder and the substrate. They are acid liberating salts which liberate acid 145

during curing. Diammonium phosphate is most commonly used as a catalyst. Ammonium sulphate and ammonium nitrate are also used as catalyst. Due to use of these chemicals, curing can be carried out at 150°C for 2 min. Cross-linking agents :- These are used when the binder is not self–reacting, even in such cases, a small amount of cross-linking agent is added. Dimethylol urea, dimethylol ethylene urea are some examples. Fixer CCL is used in acramin printing paste as a cross-linking agent. Pigment printing on cotton fabric Recipe for Binder Emulsion 200 pts. Acramin SLN Binder 5 “ Emulsfier W 50 “ Urea 146

30 Pts. Diammonium Phosphate 50 “ Water 665 “ Kerosene mixed under high speed stirring 1000 “ Total Printing Recipe : 50 pts. Acramin pigment (dispersion) 940 “ Binder emulsion 10 “ Fixer CCL 1000 “ Total Procedure :- Printing- Drying at 90-100°C till free from kerosene and then cured at 140°C at 5 min.- Rinsing- Soaping with lissapol D 1g/l and soda ash 2 g/l. at boil for 30 min. –Rinsing- Drying. 147

Various type of pigments, binders, catalysts and emulsion thickeners :- Different types of printing material are used in the industry. Some of them are as follow :- Pigments- Pigment dyestuffs such as azo pigments and phthalocyanines , Inorganic pigments such as oxides of iron, chromium, titenium , zinc and blues of the types of the prussion blue and, ultramerin blue, Toners and Lakes such as those obtained basic dye. Alizarins, luminous or fluorescent pigments. B. Binders :- Mainly binders are copolymres . They are formed from suitable monomers like methyl methacrylate , and butadine . N- methylolacryamide , which are self cross-linking 148

are also used. C. Catalysts :- They are used to accelerate cross linking of binder. ATIRA have developed a catalyst LCP which is claimed to effect curing at 110°C in 2 minutes only. D. Thickeners :- A thickener which has no effect on the handle of the fabric and which can be removed during drying and curing after printing and has the required viscosity is used as thickener. An emulsion thickener meet these requirements, so these are widely used. The emulsion thickeners have good viscosity and give better colour yield and brightness than any other water soluble thickeners and have no effect on the handle and fastness properties of the print, because both the liquids which form the emulsion viz. water and kerosene get removed by evaporation during drying and curing. 24-6-21 149

ii. Replacement of kerosene :- In a typical pigment printing paste, 75% is kerosene, 10% is binder, 5% each is gum and water, 2% urea and 1% each of DAP and emulsifier. Kerosene water emulsion acts as a thickener in pigment printing. Its use is prohibited in most of the developed countries. Moreover, the rate of petroleum products are going to sky day by day. So it is necessary to replace the kerosene by suitable alternate. The use of emulsified kerosene as a thickener in the textile industry is not only a major source of environmental pollution, it also leads to the shortage of kerosene for domestic use. In search for its substitute, extensive studies have been carried out. For this purpose, a series of methaceylic acid based co-polymers and ter -polymers were synthesized, out of which 3 of them have been found suitable for pigment printing of cotton. 150

Special Features These thickeners can be used for 60-80% replacement of kerosene without affecting the printing performance in terms of brilliancy of shade, colour value, fastener properties and feel of the fabric. This process is environment friendly. Aqueous based fully synthetic thickener system has developed for pigment printing. These has a molecular weight more than 1 lakh . These are supplied in various formulations and have high thickening property after the free acidic group is neutralized with ammonia, producing thickenings of low solid content with high viscosity. Disadvantages of fully aqueous-based thickeners :- They are liable to be influenced by electrolytes, which may breakdown the polymer molecules. So lesser quantity of the 151

catalyst may be used. ii. It is difficult to getting sharp prints on automatic flat bed, rotary screen and roller printing, where multiple colours are printed wet-on-wet, because aqueous thickenings the prints may become fed blurry (faint). iii. They impart a harsh handle to the prints, sicce they form an integral part of the final print. --------------- 152

14.Faults in printing and their prevention :-There are different methods of printing and each method has its own merits and demerits. Some faults occurs during printing processes, which are to be remove. Prominent faults are given here and their remedies is also here. Flushing or wicking- This fault occurs when colour spreads. This fault is due to the low viscosity. To avoid this fault, maintain the proper viscosity of the paste. Bleeding – In this fault, colour of the paste bleeds from the design. This fault is also due to the low viscosity. To avoid this fault, maintain the proper viscosity of the paste. Misfitting – In this fault, designs are not at their proper places. It is due to improper alignment of the screens. It is also known as out of registration, it leave unexpected areas in the design. This fault is removed by proper fitting of the screens. 153

IV Stick-in – This fault is occurs when a paper, yarn/ lump/ or part of leave stick in screen opening. This fault is removed by filtering the colour paste and clean the screen. V. Scrimping – Fabric shrink due to this fault during printing process. The pattern is then printed above the crease, which is a big fault. To avoid this fault, use the roller which remove shrink or folding of the fabric. VI Banding :- This defect created by the movement of the print head on the substrate. Scan print head, or the use of a print head that moves back and forth of the substrate in a straight line keeping the ink droplets at precise locations above the line. To avoid this fault, properly align the head. VII Unwanted marks or Spotting :- When screen has holes in it, these marks occurs. The holes should be cover to avoid the fault. 154

VIII Motteled :- This fault occurs, when colour is applied unevenly on to the fabric. The remedy of the fault is proper setting of the squeegee. Crack or Miss alignment in transfer printed fabric :-This is due to incomplete transfer of the design from paper to the fabric. The remedy of the fault is proper alignment of the speeds of the paper roll and fabric roll so that both gets suitable temperature at a time. Stop marks :- When printing machine stop, such marks obtain. To avoid the marks, waste fabric used at the end of the lot. Colour out :- This fault occurs due to less colour in the reservoir. The remedy of the fault is proper maintaining the colour in the reservoir. 25-6-21 155

UNIT V 15. Application of printing CAD software, design preparation, colour reduction, colour separation, screen preparation. In International Textile Machinary Association 1991 fair, there has been dramatic increase in the associated technology of visual display units, graphics control and high volume data storage system. With the right investments the printers now scan designs into a CAD system where a number of colour combinations can be changed, designs manipulated put into repeat colour ways created and colour separations produced. The digital information generated can subsequently be used to produce screens directly by the laser engraving technology or by the conventional means using computer produced transparencies. 156

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Textile Printing introduction and style, methods

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Textile Printing introduction and style, methods

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