Presentation On Resist Printing

Subject: Textile FinishingPresented To: Mr. Safdar

Definition of Resist Printing

Resist Printing involves a two step process in which a design pattern is printed on a White or Dyed Fabric with a Chemical or Wax. That will prevent the dyes from penetrating the fabric. When it is dyed, the color is absorbed only where there is no resisting agent is applied. After dyeing the resist is removed.

Explanation

• Resist or Reverse printing is related to Discharge printing where end results are often distinguishable. The Resist style however offers an advantage of dyes if great chemical stability where Discharge could not. It can be resisted to give prints of high fastness standard results. Results can be obtained on both White or colored pattern on pattern ground. Every class of colorant is capable being resisted. Many techniques are complex and time consuming. Before printing fabric should be treated with the starch and calendared to give flat surface upon which the resist print would form a perfect cover

Preparing Ground Color Pad-Bath• Sodium alginate, guar gum, CMC, synthetic thickener etc (Mignon NS:

Senka Corporation--maleic acid copolymer) are used as anti-migration agents. It is widely accepted that sodium alginate with low viscosity is used since it has great anti-migration effect, however, ammonium salts of tartaric acid, citric acid etc are appropriate as pH buffer for the stabilization of dyestuff inasmuch as organic acid, such as maleic acid, tartaric acid etc, can easily lead to gelation.In order to reduce the bleeding at pattern outlines, which can be a disadvantage of the pre-pad method, it is more effective to add organic acid. In addition, it is possible to prevent halation which is caused by alkali during steaming as long as the solid content of thickener in the pad bath increases as little as possible so as not to affect the hand of dried cloth. For a pad bath, it is effective to add a degassing penetrating agent (with less foaming) or auxiliary (Senka Emulsyn) that softens the dried film if necessary.

• In addition, resist printing paste can be printed before the ground color is printed with the Wet on Wet or Wet on Dry method: the after-cover printing method, or resist printing paste can be printed with the Wet on Wet or Wet on Dry method after the ground color is printed: the pre-cover printing method. Table 5 shows the advantages and disadvantages of each method: For mass production with a large ground color design, discharge printing on ground dyeing or the ground-color pre-pad method are often considered, and the pre-pad method is outstanding because its great white dischargeability allows us to choose dyestuff in wide variety. Since with the pad method, any potential defect of the cloth becomes distinguishable, it is recommended to use a high performance padder (Roller Jet padder etc) in order to carry out even padding with ground color. In addition, if the hand of dried pad cloth is rough, it will be difficult to place cloth on the printing table, therefore, it will be necessary to choose an anti-migration paste which is often used in pad-bath, and sometimes using suitable dyestuffs or adding an auxiliary may be helpful.

• In the cover printing method which is suitable for small lots, especially the after-cover printing method, since the bleeding of pattern outlines can easily occur, paste compound (a compounded mineral thickening agent) with physical resist-printing effect is recommended. In the pre-cover printing method, the paste layer prevents bleeding, but the whiteness of discharge printing will decrease. Base color printing: rotary screen and gravure roll printing machines are appropriate for cover printing since the paste layer can be made comparatively thin by the devices. In order to have fair color development, since with HPS (high-pressure steaming process), bleeding can easily occur, and the dry heat method will lead to a problem with discharge effect, the hand of cloth and color development, commonly HTS (high-temperature steaming process) is carried out.

Pad-bath preparation

• Disperse dyestuff for ground color X g

• Water Y g

• Anti-migrating Thickener 20-30 g

• pH buffer 5 g

• Penetrating Agent 0-5 g

• Senka Emulsyn 300 0-30 g

Preparing Cover-Printing Paste

• Considering leveling ground color and paste compound that is appropriate for HTS (de-paste property, color development), combining sodium alginate with modified starch, mid-etherificated CMC is recommended. Moreover, mixing O/W emulsion is appropriate to have stable levelness of print and color development.

Examples of Cover-Printing Paste

• Disperse dyestuff for ground color X g• Hot Water 200 g • Stock Paste 500 g• pH buffer (Orangic acid) 2 g • Reduction Inhibitor: Resist Liquid 10 g• Printing Improver (Senkanol CN) 10 g• High Color Depth Auxiliary for HTS:GTP-31 Senka

20 g• Balancing Y g

Stock Paste

• Sodium Alginate with low Viscosity(7%) 300g

• Modified Starch 200 g

• Primogum F-30 20 g

• Water Xg

Difference b/w Discharge & Resist Printing

• Difference is not only appearance but there processes are also different.

• In Discharge Printing, discharging agent is applied on the fabric and dye in printed areas is destroyed during processing.

• In Resist Printing, resisting agent is applied on the undyed fabric and effectively prevents the fixation or development of the ground color. It is applied by an appropriate dyeing technique such as Dyeing, Padding or Color Padding.

Functions of Resist Printing

• Resisting Agent Functions either Mechanically or Chemically or sometimes in both ways.

Mechanical Agents

• It includes Waxes, Fats, Resin Thickeners, and Pigments such as china clay of zinc and titanium and sulphates of lead and barium.

• Such mechanical agents forms a physical barrier b/w the fabric and colorant.

Chemical Agents

• It includes a wide range of color compounds including acids, alkalies, various salts, oxidizing and reducing agents.

• They prevent fixation or development of the ground colour by chemically reacting with the dye or with the reagent necessary for its fixation or formation.

• Using indigo for a ground illustrates a combined mechanical and chemical resist effect.

• After printing the fabric would be thoroughly dried to consolidate the resist barrier.

Pad Application

• Nip Padding is preferred to Immersion Padding.

• Pad application of dye reduces the time of contact and therefore the bleeding of soluble resisting agents.

• Some thickening of Pad liquor may be necessary to increase the volume of liquor carried onto the fabric.

Resist Under Aniline Black

• This particular colorant is formed on cellulosic material by the oxidation of aniline.

• Recipe:• Aniline Hydrochloride 80g

• Aniline 5 g

• Targacanth Thickener 50 g

• Water 250 ml

Resist Printing under Reactive Dyes

• A wide range of colors, brighteners and good fastness properties are available.

• Reactive dyes are now popular for both direct printing and for plain dyeing. Most of the reactive dyes can only be fixed on the cellulosic fibers in which the alkali is present.

• Recipe:• Citric Acid 50 g• Thickener 600g• Water 1000g

White Resist

Two phase fixation process can be carried out for white resist.

• Print the white material with acid, resist paste and dry.

• Pad with neutral dry liquor and dry.

• Nip pad material with fixation liquor, fix, wash off and dry.

Vat Resist under Vat Dyed Grounds

• This is not a widely used style but used for the fastness properties associated with vat dyes are necessary.

• Material is first printed with normal in Vat Print Paste of Sodium Thiosulphate.

Resisting Printing on Wool

• Various methods for resist printing on wool has been integrated. Bell has explained some of these.

• Chemical resist product Sandosperse R is a reactive agent similar to reactive dye is colorless.

• Bell and Levis described the reaction in which the resist agent with Amino group in the wool, blocking the reactive sites.

• It is complimented by anionic repulsion. Pale shades are resisted to white varying greater depth of shades.

• Sulphonic acid is used as non-anionic dye resist agent for wool was patented by Sandoz in 1955. it is used at a concentration of 150-200 g/kg with similar quantities in urea and print paste, which also incorporated thickener, non-ionic wetting agent and anti-foams. This dyeing is carried out with selected reactive dyes from various reagents.

Wax Resist

• Wax resist applying on imperable substance such as hot gum or wax onto the fabric, which will resist the color when the cloth is dipped into a dye bath. The resist substance is later removed to reveal the original color of the cloth.

Resist printing and discharge printing with disperse dyestuff

• The active carbon resist printing method had been mainly used for hand printing of high grade products until the 1960's. The active carbon resist printing method is the most appropriate for white resist printing since the method does not require the specific selection of disperse dyestuff for ground dyeing, however, in the case of colored resist printing, obtaining vivid shades is difficult with the method due to the loss of dye fixation which is caused by the adsorption of the effect color dyestuff into the active carbon. Active carbon resist-printing agents available on the market are composed of a fine-grain active carbon which is a pre-treated, thickening agent with high solidity, a reinforcing agent for paste film (minerals: titanium dioxide, talc etc) and water repellent. To have the best result in physical resist printing, it is recommended carrying out hand printing with Wet on Dry method with which it is possible to produce a thick resist printing paste layer and print a printed ground paste after drying.

• On the other hand, for the chemical resist printing method, the following agents will be appropriate:

• Heavy metals: • chelate resist printing-disperse dyestuff is chelated by

heavy metals to prevent dye fixation.• Reducing agent: • carry out reduction strip of disperse dyestuff by using

stannous chloride or sulfinate type Decrolin.• Alkali agent:• causes hydrolysis of disperse dyestuff by carrying out

the heat treatment of metallic alkali.

• The reduction method with stannous chloride is used widely, since the use of dyestuffs is very flexible and they have high dye-fixing efficiency, however, problems, such as machine corrosion caused by the acid gas during the process, skin irritation, waste water treatment and damage to the undercloth may occur. The alkali resist printing method has already been practiced and can substitute for the stannous chloride resist/discharge printing. It was introduced as an economical method, being kind to the environment, at the same time as Dispersal PC Dyestuff was put out in 1976 by ICI.

Characteristics of each resist printing agent and discharge printing agent

• On printed page

Alkali Resists Printing and Discharge Printing

• It is recommended to use sodium carbonate, potash, caustic soda, caustic potash, sodium bicarbonate, sodium silicate, trisodium phosphate or Remazol Salt FD etc as metallic alkali, however, it is important to choose the right kind, considering the resist printing effect, the sharpness of outline, the influence on effect color dyestuff etc. In general, sodium carbonate alone (solubility in water: 21.6g/100cc, 20) will work just enough, or potash (solubility in water:112g/100cc, 20) can be mixed. Since it is hard to obtain good whiteness, using a solubilizing agent is recommended in order to improve the effect of resist printing.

Characteristics of each type of thickener

• Printed on page

Mineral thickener: ECN-33 (Senka)

• Synthetic thickener: Primogum F-30 (Senka) CMC: GFN-120 (Senka)

• Sodium alginate : Primogum C-1 (Senka)• Sodium alginate/CMC/CMS: Primogum F-

100 (Senka)• CMS: M-print CE (Kyoto Seinori CO.,

LTD.)

Glycerin and polyethylene glycol are recommended as appropriate solubilizing agents, i.e. PEG 300. Comparing the effect of glycerin and PEG 300, PEG 300 has better resist printing effect, and glycerin can be mixed 1: 1 since it has a great effect on the bleeding of pattern outlines. To have greater resist printing effect (whiteness, sharpness, the dye efficiency of effect color dyestuff),

• GTG-01 (made by Senka Corporation) is recommended as an appropriate solubilizing agent. When an alkali resistant thickener is chosen, it is important to consider its resist printing effect, printability, paste removal property. As the most appropriate amount of the above type solubilizing agent used is about 10-15% within resist printing paste, it is important to choose a paste agent which has small fluidity and viscosity changes and also does not lower the sharpness of pattern outlines. Since thickeners are different from each other in their characteristics, it is necessary to use one alone or in an appropriate mix after a total evaluation on them.

Primogum F-30

• This is a printing emulsion which has been developed as being kind to the environment and can be used as an O/W emulsion paste since it easily becomes emulsified and thickened with water even under slow stirring. Since Primogum F-30 is composed of oil which does not include a high boiling-point hydrocarbon (mineral turpen), it does not lead to environmental pollution.A common half emulsion (a printing type O/W emulsion which is produced by fast stirring with mineral turpen, emulsifying agent, water and thickener) is used, in order to improve printing efficiency, penetrative property, leveling property and dyeing efficiency. The mineral turpen within this emulsion will be volatilized in the drying process after printing, therefore, it will disappear almost completely in the print paste. Thus, it does not promote the fixation of dyestuff.

• Primogum F-30 can improve printing operation (transferability of print paste, separation of screen mesh, paste splashing etc), and at the same time, the elements within its components cannot be volatilized, even in drying, but will remain in the print paste. Therefore, the dried film will stay soft, and there will be less cracking. Moreover, the elements will foster the diffusion of the dyestuff in fixing (steaming) while obtaining highly concentrated color development. Thus, even when the quality of feed steam is poor, stable color development can be maintained.If sodium alginate is used alone as a color paste on a fine mesh screen, poor printing with a brush-touch effect will occur, and the printed amount will decrease. Primogum F-30 can increase the permeability of a fine mesh screen, therefore, the printed amount does not decrease as much. By increasing screen permeability, print paste will not be stuck in the screen mesh, and related problems will be avoided. Moreover, increasing the printed amount will raise the efficiency of the dyestuff, and thus, Primogum F-30 will produce favorable conditions for the fixation of the dye. In addition, during the washing process, Primo gum F-30 is helpful in removing unfixed dye, paste agent etc.

Effect of Primogum F-30

• It is easy to prepare stock paste with an O/W emulsion.

• Trouble at each stage will decrease.• Efficiency of dye fixing will be

improved.• Paste removal property will increase.

Finishing process

• There is the discharge printing method on dyed cloth (dyestuff is fixed) and the resist printing method in which a paste with alkali is over-printed after pad-drying the ground color (dyestuff is not fixed). Both methods are based on an idea of printing on dry cloth.

• Characteristics on Printed page

After Discharge Resist Printing

After Cover Printing