DYEING AND PRINTING OVERVIEW

DYEING AND PRINTING

Dyeing          Coloration of textile Material in a single solid color

Printing        Coloration of textile material with multi colors to have some specified design with repeat

DIFFERENCE BETWEEN DYEING AND PRINTING

DYEING•

UNIFORM COLOURATION ALONG LENGTH AND WIDTH OF FABRIC• USUALLY SINGLE COLOUR IS POSSIBLE. •NO DIFFERENCE IN COLOUR BETWEEN FRONT AND BACK SIDE OF FABRIC• AQUEOUS DYEING MEDIUM OF LOW VISCOSITY •DYEING IN BATCHWISE, CONTINUOUS OR SEMI-CONTINUOUS METHOD.• FABRIC DYEING IN OPEN WIDTH OR ROPE FORM.• DYEING IN FIBRE,YARN,FABRIC,GARMENTS

            Dye-stuff ( they are the colouring materials )

• Water
• Auxiliaries ( they are the helping materials that increase the dyeing properties )

STAGES OF THE DYEING PROCESS

                       Preparation of Fabric

Preparation of the dyeing sol.

Actual dyeing ( padding , drying & fixation )

Soaping & washing

Drying

STEPS

1. Migration
2. Adsorption
3. Absorption
4. Diffusion
5. Fixation

DYE STUFF CLASSIFICATION

Dyes can be classified on four parameters but basic are two:

1. Base on Solubility
2. Base on Application or Uses
3. Base on Chemical Constituent
• Base on ionic structure

Application process

The dyeing of a textile fibre is carried out in a solution, generally aqueous, known as the dye liquor or dyebath. For true dyeing (as opposed to mere staining) to have taken place, the coloration must be relatively permanent; that is, not readily removed by rinsing in water or by normal washing procedures. Moreover, the dyeing must not fade rapidly on exposure to light. The process of attachment of the dye molecule to the fibre is one of absorption; that is, the dye molecules concentrate on the fibre surface.

TYPES OF FORCES ACTING

There are four kinds of forces by which dye molecules are bound to fibre:

1. ionic forces,
2. hydrogen bonding,
3. van der Waals' forces, and
4. covalent chemical linkages.

DYEING METHODS

• Exhaust Dyeing
• Semi-continuous method
• Continuous metod

DYEING MACHINES FOR BATCH METHOD

Fiber dyeing

• Loose stock dyeing m/c

Yarn dyeing

• Spindle package dyeing m/c
• Hank dyeing m/c

Fabric dyeing

• Beam dyeing m/c
• Jigger dyeing m/c
• Winch dyeing m/c
• Jet dyeing m/c
• Soft dyeing m/c

Garment dyeing

• Peg dyeing m/c
• Rotary drum dyeing m/c

DYEING MACHINES FOR SEMI-CONTINUOUS METHOD

• Fabric dyeing
• Pad –batch pad thermo sol

DYEING MACHINE FOR CONTINUOUS METHOD

Fiber dyeing

• Continuous fiber dyeing m/c

Yarn dyeing m/c

• Slasher dyeing m/c
• Rope dyeing m/c

Fabric dyeing m/c

• Pad-thermo sol dyeing m/c

TEXTILE PRINTING

Printing is different from dyeing in that way as it is designed to produce multicolored pattern on textile material by using printing paste rather than

METHODS OF PRINTING

The four main methods of textile printing are

1. block,
2. roller,
3. screen, and
4. heat transfer printing.

In each of these methods, the application of the colour, usually as a thickened paste, is followed by fixation, usually by steaming or heating, and then removal of excess colour by washing. Printing styles are classified as direct, discharge, or resist. In direct printing, coloured pastes are printed directly on the cloth. For discharge printing, the cloth is first dyed with a background colour, which is destroyed by reagents, or reducing agents, carried in a print paste. This action may leave the discharged design white on a coloured background, although print pastes may also contain colouring matters not destroyed by the discharging agent, producing a coloured design. In the resist process, the cloth is first printed with a substance called a resist, protecting these printed areas from accepting colour. When the cloth is dyed or pigment padded only those parts not printed with the resist are dyed. A special application of this technique, imparting plissé effects, is the printing of the fabric with a resist, followed by treatment with caustic soda.

PRINTING PASTE

The printing paste is an emulsion of dye, thickener and hydrocarbon solvent and surface active agents. The uniform consistency of the printing paste is referred to as its viscosity ( the ease with which the paste flows ). The viscosity of the printing paste is very important as it influences the clarity & appearance of the printing pattern.

STAGES IN PRINTING PROCESS

1. Preparation of the design
2. Preparation of the printing paste
3. Actual printing ( making an impression of the paste on the fabric )
4. Drying of the printing paste
5. Fixation as after treatments
6. Soaping & washing
7. Drying

GENERAL THEORY OF PRINTING

The interaction on steaming b/w the dye , fibre, water, thickener, and hydrocarbon solvent. More specifically, it explains how with in the printing paste:

• Force of repulsion is developed b/w the dye molecules and constituents of the printing paste; and
• Force of attraction is developed b/w the dye molecules and the textile material.

THEORY OF PRINTING

• The printing paste which is applied to the textile material consists of dye, water thickeners & hydrocarbons solvent. After the printing paste is applied, the textile material is usually steamed.
• Steam enable the dye molecules to migrate from the surface of the fibres and enter the fibres polymer system. Steaming swells the fibres and ensures the better penetration of the dye and improve color fastness properties of the textile material.

METHODS & MACHINES FOR PRINTING

1) Block Printing

Wooden blocks, carved with a design standing out in relief, are made from solid pieces of wood or by bonding closely grained woods with cheaper ones. When designs include large areas, these are recessed and the space

2) Roller Printing

DIFFERENT STYLES OF PRINTING

Direct style: In direct style, dyes are printed directly on the required place of the fabric with the multicolored design.

Discharge style: Fabric is first dyed and then printed with a paste containing a discharging agent thus white or colored effect can be produced on colored ground.

Resist style: First a resisting agent is printed on white fabric and then fabric is dyed.

Special style:1) Transfer printing style,2) Burnout printing style

TEXTILE FINISHING PROCESS

Types of Processes and Objectives:

The term finishing includes all the mechanical and chemical processes employed commercially to improve the acceptability of the product, except those procedures directly concerned with colouring. The objective of the various finishing processes is to make fabric from the loom or knitting frame more acceptable to the consumer. Finishing processes include preparatory treatments used before additional treatment, such as bleaching prior to dyeing; treatments, such as glazing, to enhance appearance; sizing, affecting touch; and treatments adding properties to enhance performance, such as preshrinking. Newly formed cloth is generally dirty, harsh, and unattractive, requiring considerable skill for conversion into a desirable product. Before treatment, the unfinished fabrics are referred to as gray goods, or sometimes, in the case of silks, as greige goods.

Finishing is process in which fabric is treated with some mechanical or chemical process before or after dyeing or printing to give the fabric a fancy / novelty touch to make it more durable, flexible soft and good in appearance and handle.

Chemical finishes

1. Crease resistance/ wrinkle free / resin finish
2. Soft finish
3. Water professing
4. Water repellent/ oil repellent/ soil repellent
5. Weighting finish
6. Anti-bacterial finish
7. Flame proofing
8. Stiffening finish
9. Anti static finish
10. Sanforizing finish

MECHANICLE FINISHES

1. Heat setting finish ( stentor – pin type or clip type )
2. Raising finish ( teasel raising m/c & card wire m/c )
3. Peaching / sueding/ emerizing finish ( emerizing m/c )
4. Sanforizing finish ( rigmal m/c & confined passage )
5. Calendaring finish
• Universal calendar
• Friction calendar
• Embossing calendar
• Schriener calendar

UNDESIRED PROPERTIES

1.      Pilling

2.      Creases ( bad effect but sometimes required as creep )

3.      Stiffness

4.      Water repellency

5.      Shrinkage

6.      Shade variation

7.      Wrinkle

8.      Unclear vision

9.      Weight loss

VALUE ADDED EFFECTS

1. Lustre
2. Soft handle
3. Fire proofing
4. Water proofing
5. Fragrance
6. Crease resistance
7. Dimension stability
8. Weighting
9. Embossing
10. Anti-bacterial