Pigment Dyeing - Definition of Pigment Dyeing

PIGMENT DYEDEFINITION: Pigment is a substrate in a particulate form which is insoluble in water but which can be dispersed in this medium to modify its color and light scattering proper

PIGMENT DYEING

Name : MAZADUL HASAN SHESHIR

ID: 2010000400008

Batch: 13th Batch (Session 2009-2013) Department: Wet Processing Technology Email: mazadulhasan@yahoo.com

Blog: www Textilelab.blogspot.com

Southeast University

Department of Textile Engineering

PREPARED BY © right

PIGMENT DYE

DEFINITION: Pigment is a substrate in a particulate form which is insoluble in water but

which can be dispersed in this medium to modify its color and light scattering properties They are organic or inorganic coloring materials They have no affinity to textile materials They are fixed on the textile material with the help of binding agent in form a thin invisible coating

In pigment auxochrome groups are absent

Pigment dyeing is not really "dyeing" in it's truest form because the pigments stick on the

fabric with the help of binders Pigments are insoluble in water They exist in the form of finely ground molecules, milled for garment dyeing purposes into a paste When anionic dispersing agents are added, a slightly negative charge is present, thus the foundation for pigment dyeing is born

When a positively charged cationic pre-treat is added to the fiber a magnetic bond is formed The process is complete when a cationic binder is added to "lock" the pigment into place.In pigment dyeing no actual chemical reaction takes place between the dye and the fabric

ClASSIFICATION OF PIGMENT:

PIGMENT DYEING PROCESS:

TRADE NAMES:

Wintramin Winsol chem- Industries India

Helizerine BASF Germany

Neopralac Francolor France

Acramin Bayer AG West Germany

PROPERTIES OF PIGMENT:

1 Insoluble in water.

2 Organic or inorganic compounds.

3 No auxochrome group.

4 No direct affinity towards textile materials.

5 Binder is required for fixation.

6 Applicable to all kinds of fibers or textile materials.

7 No after treatment is required after coloration process.

8 Rubbing fastness is poor.

9 Water, wash and light fastness is very good.

10.A wide range of bright shades can be produced for some physical

properties-Particle size : 0.2-0.4 µ

Specific gravity : 1.14-1.37 for most of the pigments

Boiling points : Decompose at 190º- 345ºc

Melting points : Softeners ranges from the points 110º-175ºc

CHEMICAL PROPERTIES:

1 Most of the pigments are azoic compounds Besides that it may be inorganic oxide, inorganic salt phthalocyanine metal compounds etc.

2 Insoluble in water and other solvents like white spirit, per

chloroethylene, trichloroethylene, CCl4 etc.

3 Pigments are toxic Some are oral toxic, some are dermal toxic, some causes eye irritation etc.

REQUIRED PROPERTIES OF PIGMENTS:

1 Should have good covering power.

2 Should be chemically inert.

3 Should have freely mixing quality.

4 Should have good resistance to acid, alkali, bleaching agent etc.

5 Should have good fastness properties.

6 Should be applicable to all fibers and textile materials.

7 Should have well resistant to solvents.

DIFFERENCE BETWEEN DYES AND PIGMENTS:

1 Water solubility is 70% 1 100% water insoluble

2 Dyes have direct affinity to

textile material 2 They have no direct affinity to textile materials

3 Auxochrome groups are

6 No binding agent is required 6 Binding agent is required

7 Dye diffusions in the fabric 7 Pigment diffusions on the fabric

EXAMPLE OF VARIOUS PIGMENTS:

ORGANIC PIGMENT:

1 Dyes converted into pigment:

a) Dyes made insoluble by precipitation on substrate:

Peacok Blue Lake : CI pigment blue 24 ; Bronze red pigment : CI pigment 90b) Vat dyes converted into pigment: Thio indigo red violet : Violet 36

Indanthrone blue : Blue 60Perinone orange : orange 43

2 Quinacridone:

Cinquasia blue B, Cinquasia red Y, Cinquasia violet R

3 Azo pigments:

a) Metal free water insoluble azo- compounds (Group- I):

CI pigment red: Red 3; Fire red: Red 4;

Red tonner: Red 6;

Per matone orange : Orange 5b) Metal containing water soluble azo compounds: Low solubility (Group- 2a):

Lithol red: Pigment red 49Lake red: CI pigment red 56

4 High solubility (Group- 2b):

Precipitation of pigment from orange 11: CI acid orange 7

INORGANIC PIGMENT:

I White pigment:

A Barytes ( Barium sulphate),

B Gypsum ( CaSO4 2H2O),

i) α- FeOOH of Fe2O3 H2O

ii) FeSO4 H2O (Red, Brown, Black)

iii) FeO, Fe2O3 and FeOOH (Mixed crystal)

INORGANIC PIGMENT:

REQUIREMENT OF WHITE PIGMENT:

1 Primary requirement is that it should not absorb any radiation in the visible part of electromagnetic spectrum (400-700nm)

2 Second requirement is that it should be in the form of particles fairly uniform in the size with the diameter of the order of 100 nm

3 Third requirement is that it should have as high refractive index between 1.5- 2.3 throughout the visible spectrum as possible

Example of White Pigment:

They includeBarytes(BaSO4), Gypsum(CaSo4.2H2O),Whitening(CaCO3), China clay, talc,& Silica

No Organic pigments Inorganic pigments

1

These are natural pigments like the

Cadmiums, Cobalts, Earth Colors, etc These are pigments created in the laboratory and include the Pthalocyanines,

Quinacidrones, Dioxazenes, Napthols, etc.2

The main source of organic pigments

are plants and plant products The inorganic pigments are manufactured from topical cosmetic and also from dirt

3

Carbon chains or carbon rings are

always present in the molecules of

the Organic Pigments

In the molecules of the Inorganic Pigments, the cat-ions of metal are found in an array form with the non-metallic anions This arrangement doesn't allow these pigments

to dissolve in the solvent and plastic

4 have a high refractive index have much lower values

5 most inorganic pigments are opaque organic pigments are transparent

Difference

COlORED PIGMENTS:

At past- Yellow lead chromates and iron blue They are not used for lead poisoning

Colored pigments are used when organic pigments are unsuitable or can’t match

ULTRAMIN:

1) Synthetic form of blue mineral “Lapis Lazuli” (Latin name) incorporated from China and India

2) Higher light fastness (Grade : 7-8)

3) Attractive blue color with excellent resistance to alkalies and all organic solvents.4) Easily dispersible

5) Non toxic

6) Poor resistance to acid

NOTE: 4-5 days at 8000c.

Requires absence of iron impurities

2 Higher heat stability than organic pigments (400c).

3 Better solvent fastness and high migration fastness

Binders with a particle size range of 0.05 to 2 microns are usually available These contain about 6% by weight of reactive groups for cross linking of the binder to textile Cross linking increases the rubbing, washing & dry cleaning fastness properties but it affects the handle of fabric.

TYPES OF BINDER:

According to origin:

1 Natural: Glue, Gelatine etc

2 Synthetic: Acramin binder.

According to chemical groups:

3 IG binder: Emulsion copolymer of vinyl acetate & butyl acrylate with modified urea formaldehyde.

4 AG binder: Emulsion copolymer of olifinic unsaturated monomers in

PIGMENT DYEING PROCESS:

Dying Recipe:

Pigment → 2 gm/ lit Binder → 20 gm/ lit Levelling agent → 1gm/ lit Temp (Padding) → Room to 60c

PH → 4-5 Drying → 100c Curing → 140-180c for 2-3 min for cotton 160-180c for 2-3 min for synthetic

M:L → 1:20 to 1:30

PIGMENT DYEING PROCESS:

1 At first binder is weighted and diluted with cold water.

2 Then pigments and other ingredients are added to it.

3 The dyeing liquor is well filtered and stirred Fabric is rolled on feed roller and passed over guide roller below immersion roller and in between padders.

4 Then the dye liquor is taken in immersion tray.

5 The fabric passes through the dye bath, takes up pigment solution and then squeezed by padders roller which regulates pick up percentage.

6 After dyeing the fabric is dried at 90c- 100c and then curing is done at cotton 160c and polyester 180c for 2-3 minutes.

Procedure:

Process sequence:

1.Cationisation of the fabric or giving electric charge to the fabric by a powerful

cationic pretreatment.

Pigment dyeing is an electrical process whereby the goods to be dyed are given an

electrical charge opposite that of the pigment When the pigment is added to the bath, the opposite electrical charges attract each other, much like the north and the south

poles of two magnets Because of the electrical nature of the process

A typical recipe for cationizing Step

• Cationic Imparting Agent

• Wetter

• Acetic Acid for pH control

The cationic agent is applied with a wetting agent and acetic acid onto the fabric in the batch or commercial dyeing machine After a period of time, the fabric is rinsed

The pigment dyeing process is generally a three step process such as:

2.Pigment exhaustion on the fabric

The pigments are first mixed with water and a dispersing agent that imparts an anionic charge

to the pigments This solution is added gradually to the dyeing machine The temperature of the bath is slowly increased and the machine is held at the dyeing temperature for up to 20

minutes The fabric is held at an elevated temperature to increase the adsorption of the

The pigment dyeing process is generally a three step process such as:

Dyeing Curve:

Application Principle : Pigment dyeing

Application Principle : Pigment dyeing

Application Principle : Pigment dyeing

The pigment dyeing process :

PIGMENT DYEING FAULTS:

1 Listing effects: It occurs along the width of fabric due to uneven pressure of

padder rollers which cause shade variation.

2 Tailing effect: It occurs along the length of fabric due to changing concentration of pigment liquor This also causes shade variation.

ADVANTAGE OF PIGMENT DYEING:

1 A wide range of color can be produced by pigments.

2 Pigments can be applied to any kind of fiber It is the only coloration process of glass fiber.

3 Pigments are cheap and available.

4 No washing or rinsing is required after printing.

5 Pigment dyeing process is speedy and fast.

6 The curing and drying process is simple and easy.

7 Water consumption is less.

DISADVANTAGES OF PIGMENT COLORATION:

1 Pigments are water insoluble.

2 Bad rubbing fastness.

3 Fabric handle and aesthetic feeling is bad.

4 Unhygienic polymers are used sometimes.

5 Less resistant to chemical finishing and cleanings.

6 Binder qualities contaminates dyeing qualities.

REQUIRED PROPERTIES OF BINDER:

The binder must have certain qualities For

example-1 It should not get coagulated due to shear forces.

2 The binder film must be clear / transparent.

3 The binder film must be of even thickness, smooth, neighther too hard

nor too soft.

4 It should be elastic in nature and should have good adhesion to the

substrate without being tacky.

5 It should have good resistance to chemical and mechanical stresses.

6 It should easily removable from equipments.

Limitations of Pigment Dyeing

1 Color fading could be a problem if not desired, and can only be kept intact

with further chemical treatments.

2 The abrasion resistance and hand could be unsatisfactory depending upon

the pigment, binder and softener used.

3 Dark and deep shades are better produced with other dyestuffs rather

than pigments.

Limitations of Pigment Dyeing

1 Its applicable to a wide range of textiles and wide gamut of colors

available Some brilliant fluorescent pigments are available for special applications and fashion items

2 The process of pigment dyeing can also be relatively cheap.

3 The process chemicals are less toxic , environmentally friendly and

least polluting.

4 The color fades with the repeated use , just like denims.

Advantages of pigment dyeing

The primary difference between these colorants is their solubility Pigments used in printing inks are colorants that are insoluble in water and most solvents For instance, copper

phthalocyanine blue is the primary blue colorant used in packaging and is quite insoluble in water and organic solvents As the name indicates, it is a blue pigment that includes copper The rest of its structure is a highly complex aromatic structure of benzene rings that include nitrogen atoms

Unlike pigments, the number of dye colorants is seemingly infinite Dyes are organic

colorants that are soluble, and they are commonly used in the textile industry and in office products, such as ink jet printers In packaging applications, dyes do not have the product resistance of pigments Dyes provide brilliant color and are used in products that do not require long-term resistance Most have inferior solvent bleed and oxidation resistance

Many dyes are chemically acids or bases and usually are found in the form of salts For

example, sodium salts of sulfonic or carboxylic acid groups are used to solubilize certain dyes Dyes used in printing paper can be made insoluble chemically by reacting with

components in the paper For instance, presence of calcium ion or tetra-alkyl ammonium ion will make the dye insoluble and “cement” it to the substrate

The basic difference between dyes and pigments is their solubility Whereas pigments are insoluble and must be used as dispersions in inks and coatings, dyes are soluble colorants

What is the difference between pigments and dyes?

 applicable on nearly all fibres and fibre blends by basically the same method

Wide range of uses

 direct, discharge, resist printing, coating and dyeing

 printing alongside other classes of dye

 printing of special effects (e.g matt white, matt coloured, lacquer, gold and silver, pearlescent, relief printing; black for outlines)

Economical procedure

 simple handling / application

 fixation conditions easy to meet

 no washing-off of the prints in direct printing

 time-/ energy-saving process as a whole

 low investment

Environmentally acceptable

 little waste water / waste air pollution with white-spirit-free /

 low-content white-spirit printing systems

High performance

 high fastness level (upon selection)

 high colour yield with high brilliancy (upon selection)

1 Complete offer of pigment preparations

2 "High conc" products

3 Highly precise particle size and distribution

4 Migration of pigment preparation is only to handle well in an optimised recipe

5 Careful selection of auxiliaries

6 Selected range shows very good dyeing on PES/PEC/Cotton

7 Highest fastness results with Imperon HF

8 Very good results after brush wash test with selected pigments

9 in an optimised recipe (Imitates household washing)

Criteria of pigment dye selection