We are Textile Engineer, we only apply dyes and pigment on textile substrate but we need to know how dyes and pigment manufacturing. I have details about all dyes manufacturing.

1. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
We are Textile Engineer, we only apply dyes and pigment on textile substrate but we need to
know how dyes and pigment manufacturing. I have details about all dyes manufacturing.
Flow chart of Manufacturing of dyes & production of colorants
Raw materials
Sublimation
Freezing
Distillation
Precipitation
Decantation
Crystallization
Filtration
Centrifugation
Evaporation
Size Reduction and Size Separation
Drying
Solvent Extraction

2. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
Acid dyes are water-solubleanionic dyes that are applied to fibers such as silk, wool, nylon and
modified acrylic fibers using neutral to acid dye baths. Attachment to the fiber is attributed, at
least partly, to salt formation between anionic groups in the dyes and cationic groups in the fiber.
Acid dyes are not substantive to cellulosic fibers. Most synthetic food colors fall in this category.
Basic dyes are water-soluble cationic dyes that are mainly applied to acrylic fibers, but find
some use for wool and silk. Usually acetic acid is added to the dye bath to help the uptake of the
dye onto the fiber. Basic dyes are also used in the coloration of paper.
Direct or substantive dyeing is normally carried out in a neutral or slightly alkaline dyebath, at
or near boiling point, with the addition of either sodium chloride (NaCl) or sodium sulfate
(Na2SO4) or sodium carbonate (Na2CO3). Direct dyes are used on cotton, paper, leather, wool,
silk and nylon. They are also used as pH indicators and as biological stains.
Mordant dyes require a mordant, which improves the fastness of the dye against water, light and
perspiration. The choice of mordant is very important as different mordants can change the final
color significantly. Most natural dyes are mordant dyes and there is therefore a large literature
base describing dyeing techniques. The most important mordant dyes are the synthetic mordant
dyes, or chrome dyes, used for wool; these comprise some 30% of dyes used for wool, and are
especially useful for black and navy shades. The mordant, potassium dichromate, is applied as an
after-treatment. It is important to note that many mordants, particularly those in the heavy metal
category, can be hazardous to health and extreme care must be taken in using them.
Vat dyes are essentially insoluble in water and incapable of dyeing fibres directly. However,
reduction in alkaline liquor produces the water soluble alkalimetalsalt of the dye, which, in this
leuco form, has an affinity for the textile fibre. Subsequent oxidation reforms the original
insoluble dye. The color of denim is due to indigo, the original vat dye.
Reactive dyes utilize a chromophore attached to a substituent that is capable of directly reacting
with the fibre substrate. The covalent bonds that attach reactive dye to natural fibers make them
among the most permanent of dyes. "Cold" reactive dyes, such as Procion MX, Cibacron F, and
Drimarene K, are very easy to use because the dye can be applied at room temperature. Reactive
dyes are by far the best choice for dyeing cotton and other cellulose fibers at home or in the art
studio.
Disperse dyes were originally developed for the dyeing of cellulose acetate, and are water
insoluble. The dyes are finely ground in the presence of a dispersing agent and sold as a paste, or
spray-dried and sold as a powder. Their main use is to dye polyester but they can also be used to
dye nylon, cellulose triacetate, and acrylic fibres. In some cases, a dyeing temperature of 130 °C
is required, and a pressurised dyebath is used. The very fine particle size gives a large surface
area that aids dissolution to allow uptake by the fibre. The dyeing rate can be significantly
influenced by the choice of dispersing agent used during the grinding.
Azoic dyeing is a technique in which an insoluble azo dye is produced directly onto or within the
fibre. This is achieved by treating a fibre with both diazoic and coupling components. With
suitable adjustment of dyebath conditions the two components react to produce the required

3. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
insoluble azo dye. This technique of dyeing is unique, in that the final color is controlled by the
choice of the diazoic and coupling components. This method of dyeing cotton is declining in
importance due to the toxic nature of the chemicals used.
Sulfur dyes are two part "developed" dyes used to dye cotton with dark colors. The initial bath
imparts a yellow or pale chartreuse color, This is aftertreated with a sulfur compound in place to
produce the dark black we are familiar with in socks for instance. Sulfur Black 1 is the largest
selling dye by volume.
Food dyes
One other class that describes the role of dyes, rather than their mode of use, is the food dye.
Because food dyes are classed as food additives, they are manufactured to a higher standard than
some industrial dyes. Food dyes can be direct, mordant and vat dyes, and their use is strictly
controlled by legislation. Many are azo dyes, although anthraquinone and triphenylmethane
compounds are used for colors such as green and blue. Some naturally-occurring dyes are also
used.
Other important dyes
A number of other classes have also been established, including:
 Oxidation bases, for mainly hair and fur
 Laser dyes: see, for example, rhodamine 6G and coumarin dyes.
 Leather dyes, for leather
 Fluorescent brighteners, for textile fibres and paper
 Solvent dyes, for wood staining and producing colored lacquers, solvent inks, coloring
oils, waxes.
 Carbene dyes, a recently developed method for coloring multiple substrates
 Contrast dyes, injected for magnetic resonance imaging, are essentially the same as
clothing dye except they are coupled to an agent that has strong paramagnetic properties.
 Mayhem's dye, used in water cooling for looks, often rebranded RIT dye
Chemical classification of dyes
By the nature of their chromophore, dyes are divided into:
 Category:Acridine dyes, derivates of acridine
 Category:Anthraquinone dyes, derivates of anthraquinone
 Arylmethane dyes
o Category:Diarylmethane dyes, based on diphenyl methane
o Category:Triarylmethane dyes, derivates of triphenylmethane
 Category:Azo dyes, based on -N=N- azo structure
 Diazonium dyes, based on diazonium salts
 Nitro dyes, based on a -NO2nitro functional group
 Nitroso dyes, based on a -N=O nitroso functional group

4. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
 Phthalocyanine dyes, derivatives of phthalocyanine
 Quinone-imine dyes, derivatives of quinone
o Category:Azin dyes
 Category:Eurhodin dyes
 Category:Safranin dyes, derivates of safranin
o Indamins
o Category:Indophenol dyes, derivates of indophenol
o Category:Oxazin dyes, derivates of oxazin
o Oxazone dyes, derivates of oxazone
o Category:Thiazine dyes, derivatives of thiazine
 Category:Thiazole dyes, derivatives of thiazole
 Xanthene dyes, derived from xanthene
o Fluorene dyes, derivatives of fluorene
 Pyronin dyes
o Category:Fluorone dyes, based on fluorone
 Category:Rhodamine dyes, derivatives of rhodamine
Raw Materials for indigo
The raw materials used in the natural production of indigo are leaves from a variety of plant
species including indigo, woad, and polygonum. Only the leaves are used since they contain the
greatest concentration of dye molecules. In the synthetic process, a number of chemicals are
employed as described below.
The Manufacturing Process
Natural extraction
 1) Plant extraction of indigo requires several steps because the dye itself does not actually
exist in nature. The chemical found in plant leaves is really indican, a precursor to indigo.
The ancient process to extract indican from plant leaves and convert it to indigo has
remained unchanged for thousands of years. In this process, a series of tanks are arranged
in a step wise fashion. The upper-most tank is a fermentation vessel into which the
freshly cut plants are placed. An enzyme known as indimulsin is added to hydrolyze, or
break down, the indican into indoxyl and glucose. During this process carbon dioxide is
given off and the broth in the tank turns a murky yellow.
 2) After about 14 hours, the resulting liquid is drained into a second tank. Here, the
indoxyl-rich mixture is stirred with paddles to mix it with air. This allows the air to
oxidize the indoxyl to indigotin, which settles to the bottom of the tank. The upper layer
of liquid is siphoned away and the settled pigment is transferred to a third tank where it is
heated to stop the fermentation process. The resultant mixture is filtered to remove
impurities and dried to form a thick paste.

5. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
Historically, the Japanese have used another method which involves extracting indigo
from the polygonum plant. In this process the plant is mixed with wheat husk powder,
limestone powder, lye ash, and sake. The mixture is allowed to ferment for about one
week to form the dye pigment which is called sukumo.
Synthetic production
 3)A variety of synthetic chemical processes have been used to produce indigo. All these
processes involve combining a series of chemical reactants under controlled conditions.
The reactants undergo a series of reactions which result in the formation of the indigo
molecule. A number of other chemical byproducts are also produced in this reaction.
 4)These synthesis reactions are conducted in large stainless steel or glass reaction vessels.
These vessels are equipped with jackets to allow steam or cold water to flow around the
batch as the reactions progress. Because of the complexity of these chemical processes,
the dye is usually made in batch quantities. There are, however, a few methods invented
by the Germans for continuous process manufacturing.
Types of reactions
 5) The first commercial method of producing indigo was based on Heumann's work. In
this method, N-phenylglycine is treated with alkali to produce indoxyl, which can be
converted to indigotin by contact with air. However, the amount of dye yielded by this
process is very low. Another, more efficient, synthesis route utilizes anthranilic acid. This
process was popular with major manufacturers, such as BASF and Hoechst, for over 30
years. A variation of this method (which has become widely used) involves the reaction
of aniline, formaldehyde, and hydrogen cyanide to form phenylglycinonitrile. This
material is then hydrolyzed to yield phenylglycine which is then converted to indigotin.
Currently, a method which uses sodamide with alkali to convert phenylglycine to
indoxyl. Sodamide reacts with excess water, thus lowering the overall reaction
temperature from almost 570°F (300°C) to 392°F (200°C). This results in a much more
efficient reaction process.
Finishing operations
 6) After the chemical reaction process is complete, the finished dye must be washed to
remove impurities and then dried. The dried powder can be packed in drums or
reconstituted with water to form a 20% solution and filled in pails.
The chemical symbol for indican, the compound found in the leaves of the indigo plant
that is used to make indigo dye.

6. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
Quality Control
During indigo manufacture, the reaction process is continuously monitored to ensure the
chemicals are combined in the proper ratios. Key elements that must be controlled include the
pH (or acid/base quality of the batch), the temperature (which controls the speed of the reaction),
and the reaction time (which determines the degree of completion). If any of these variables
deviate from specifications, the resulting reaction product can be affected. Typically, poor
quality control results in lower yield of the dye, which increases costs for the manufacturer.
To ensure that manufacturers can consistently purchase the same shade of dye, indigo is assigned
a Color Index number that defines its shade. It is designated as "CI Natural Blue CI 75780."
Byproducts/Waste
Indigo production produces a variety of waste products which must be handled carefully. In
addition to the reactants described above, there are other reaction side products that are produced
along with the indigo. Some of these materials are considered to be hazardous and must be
disposed of in accordance with local and federal chemical waste disposal guidelines. These waste
chemicals can enter the environment in at least three different ways. The first is during the actual
manufacture of the molecule. The second is when the dye is applied to the yarn, and the third is
when the dye is eluted into the wash water during the initial stonewashing or wet processing of
the fabric. This last route typically occurs during the production of denim fabric.
The Future
Much of the need for indigo is being met with other types of blue dyes and today most of the
indigo used by the world is made out-side the United States. Researchers are concentrating on
new methods of indigo manufacture that are more environmentally friendly. One promising
future method involves using biocatalysts in the dye reaction process. Indigo dye may be one of
the first high-volume chemicals made through a biological route. Genencor International, of
Rochester New York, is evaluating a process to produce indigo using biotechnology. According
to Charles T. Goodhue, Genencor's Program Director/Biocatalysis Research and Development,
indigo produced by this method is chemically the same as the regular synthetic dye and behaves
identically in dyeing tests. However, at this time the technology is expensive and production
costs could be prohibitive. Genencor is seeking a major market partner to work with them in the
development of this new technology.
Manufacturers who use indigo in dying operations are also seeking to improve their use of the
dye. For example, Burlington's Denim Division introduced a technology in 1994 they call "Stone
Free," which allows indigo dye in the fabric to break down 50% faster in the stonewash cycle.
Compared to traditional methods of stonewashing fabric dyed with indigo, their new process
uses few, if any, pumice stones which help give the fabric its faded look. Therefore, pumice
stone handling and storage costs are reduced, along with time required to separate pumice from
garments after stonewashing. It also uses much less bleach. Therefore, this new process not only
reduces garment damage, but also reduces waste produced by the stones