All Topics  
Acid dye

 

 
   Email Print
   Bookmark   Link
 

 

Acid dye
 
 
  Topics Acid dye Topic Home

Acid dye is a member of a class of dye
Dye

A dye can generally be described as a colored substance that has an Chemical affinity to the Wiktionary:substrate to which it is being applied....
 that is applied from an acidic solution. In the home or art studio, the acid used in the dyebath is often vinegar (acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
) or citric acid
Citric acid

Citric acid is a weak organic chemistry acid, and it is a natural preservative and is also used to add an acidic, or sour, taste to foods and soft drinks....
. The uptake rate of the dye is controlled with the use of sodium chloride.

In textiles, acid dyes are effective on protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
 fibers, i.e. animal hair
Hair

Hair is a protein filament that epidermal growth from hair follicle deep within the dermis. The fine, soft hair found on many nonhuman mammals is typically called fur; wool is the characteristically curly hair found on sheep and goats....
 fibers like wool
Wool

Wool is the fiber derived from the specialized skin cells, called follicles, of animals in the Caprinae family, principally domestic sheep, but the hair of certain species of other Mammalia such as cashmere goat, llamas, rabbits and keeshonds may also be called wool....
, alpaca
Alpaca

The Alpaca is a Domestication species of South American camelid. It resembles a small llama in superficial appearance.Alpacas are kept in herds that graze on the level heights of the Andes of Ecuador, southern Peru, northern Bolivia, and northern Chile at an altitude of to meters above sea-level, throughout the year....
 and mohair
Mohair

Mohair usually refers to a silk-like textile or yarn made from the hair of the Angora goat. The word "mohair" was adopted into English before 1570 from the Arabic language mukhayyar, a type of haircloth, literally 'choice', from khayyara, 'he chose'....
. They are also effective on silk
Silk

Silk is a natural protein fiber, some forms of which can be weaving into textiles. The best-known type of silk is obtained from Pupa#Cocoons made by the larvae of the mulberry silkworm Bombyx mori reared in captivity ....
. They are effective in dyeing the synthetic
Synthetic fiber

Synthetic fibers are the result of extensive research by scientists to improve upon naturally occurring animal and plant. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes into the air, forming a thread....
 fiber nylon
Nylon

Nylon is a generic designation for a family of synthetic polymers known generically as polyamides and first produced on February 28, 1935 by Wallace Carothers at DuPont....
 but of minimal interest in dyeing any other synthetic
Synthetic fiber

Synthetic fibers are the result of extensive research by scientists to improve upon naturally occurring animal and plant. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes into the air, forming a thread....
 fibers.

Acid dyes are generally divided into three classes which depend on fastness requirements, level dyeing properties and economy.






Discussion
Ask a question about 'Acid dye'
Start a new discussion about 'Acid dye'
Answer questions from other users
Full Discussion Forum



Encyclopedia


Acid dye is a member of a class of dye
Dye

A dye can generally be described as a colored substance that has an Chemical affinity to the Wiktionary:substrate to which it is being applied....
 that is applied from an acidic solution. In the home or art studio, the acid used in the dyebath is often vinegar (acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
) or citric acid
Citric acid

Citric acid is a weak organic chemistry acid, and it is a natural preservative and is also used to add an acidic, or sour, taste to foods and soft drinks....
. The uptake rate of the dye is controlled with the use of sodium chloride.

In textiles, acid dyes are effective on protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
 fibers, i.e. animal hair
Hair

Hair is a protein filament that epidermal growth from hair follicle deep within the dermis. The fine, soft hair found on many nonhuman mammals is typically called fur; wool is the characteristically curly hair found on sheep and goats....
 fibers like wool
Wool

Wool is the fiber derived from the specialized skin cells, called follicles, of animals in the Caprinae family, principally domestic sheep, but the hair of certain species of other Mammalia such as cashmere goat, llamas, rabbits and keeshonds may also be called wool....
, alpaca
Alpaca

The Alpaca is a Domestication species of South American camelid. It resembles a small llama in superficial appearance.Alpacas are kept in herds that graze on the level heights of the Andes of Ecuador, southern Peru, northern Bolivia, and northern Chile at an altitude of to meters above sea-level, throughout the year....
 and mohair
Mohair

Mohair usually refers to a silk-like textile or yarn made from the hair of the Angora goat. The word "mohair" was adopted into English before 1570 from the Arabic language mukhayyar, a type of haircloth, literally 'choice', from khayyara, 'he chose'....
. They are also effective on silk
Silk

Silk is a natural protein fiber, some forms of which can be weaving into textiles. The best-known type of silk is obtained from Pupa#Cocoons made by the larvae of the mulberry silkworm Bombyx mori reared in captivity ....
. They are effective in dyeing the synthetic
Synthetic fiber

Synthetic fibers are the result of extensive research by scientists to improve upon naturally occurring animal and plant. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes into the air, forming a thread....
 fiber nylon
Nylon

Nylon is a generic designation for a family of synthetic polymers known generically as polyamides and first produced on February 28, 1935 by Wallace Carothers at DuPont....
 but of minimal interest in dyeing any other synthetic
Synthetic fiber

Synthetic fibers are the result of extensive research by scientists to improve upon naturally occurring animal and plant. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes into the air, forming a thread....
 fibers.

Acid dyes are generally divided into three classes which depend on fastness requirements, level dyeing properties and economy. The classes overlap and generally depend on type of fiber
Fiber

Fiber or fibre is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of yarn. They are very important in the biology of both plants and animals, for holding tissue s together....
 to be coloured and also the process used.

Acid dyes are thought to fix to fibers by hydrogen bonding, Van der Waals forces and ionic bonding. They are normally sold as the Sodium salt therefore they are in solution anionic
Anionic

In chemistry, an anionic species is one that contains a full electric charge. These types of chemical compound can range in reactivity, but most are fairly reactive.Anionic is a chemical that is also used in things like washing detergent.......
. Animal protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
 fibers and synthetic
Synthetic fiber

Synthetic fibers are the result of extensive research by scientists to improve upon naturally occurring animal and plant. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes into the air, forming a thread....
 Nylon
Nylon

Nylon is a generic designation for a family of synthetic polymers known generically as polyamides and first produced on February 28, 1935 by Wallace Carothers at DuPont....
 fibers contain many cationic sites therefore there is an attraction of anionic
Anionic

In chemistry, an anionic species is one that contains a full electric charge. These types of chemical compound can range in reactivity, but most are fairly reactive.Anionic is a chemical that is also used in things like washing detergent.......
 dye molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
 to a cationic site on the fiber. The strength (fastness) of this bond is related to the desire/ chemistry of the dye to remain dissolved in water over fixation to the fiber.

History of acid dye


Structures

The chemistry of acid dyes is quite complex. Dyes are normally very large aromatic molecules consisting of many linked rings. Acid dyes usually have a sulfo or carboxy group on the molecule making them soluble in water. Water is the medium in which dyeing takes place. Most acid dyes are related in basic structure to the following:

Anthraquinone
Anthraquinone

Anthraquinone is an aromatic hydrocarbon organic compound. It is a derivative of anthracene. It has the appearance of yellow or light gray to gray-green solid crystalline powder....
 type:

Many acid dyes are synthesised from chemical intermediates which form anthraquinone-like structures as their final state. Many blue dyes have this structure as their basic shape. The structure predominates in the levelling class of acid dye.

Azo dyes:

The structure of azo dyes is based on azobenzene, Ph-N=N-Ph (see right showing cis/ trans isomers) Although Azo dyes are a separate class of dyesuff mainly used in the dyeing of cotton (cellulose) fibers many acid dyes have a similar structure, most are red in color.

Triphenylmethane
Triphenylmethane

Triphenylmethane, or triphenyl methane, is the hydrocarbon with the chemical formula 3CH. This colorless solid is soluble in nonpolar organic solvents, but not water....
 related:
Triphenylmethane
Acid dyes having structures related to triphenylmethane predominate in the milling class of dye. There are many yellow and green dyes commercially applied to fibers that are related to triphenylmethane.

Classes of acid dyes

Equalising/levelling acid dyes: Highest level dyeing
Dyeing

Dyeing is the process of imparting colours to a textile material in loose fibre, yarn, cloth or garment form by treatment with a dye....
 properties. Quite combinable in trichromatic shades. Relatively small molecule therefore high migration before fixation. Low wet fastness therefore normally not suited for apparel fabric.

Milling acid dyes: Medium to high wet fastness. Some milling dyes have poor light fastness in pale shades. Generally not combinable. Used as self shades only.

Metal complex acid dyes: More recent chemistry combined transition metals with dye precursors to produce metal complex acid dyes with the highest light fastness and wet fastness. These dyes are also very economical. They produce, however, duller shades.

Health and safety

Any dyes including acid dyes have the ability to induce senstisation in humans due to their complex molecular structure and the way in which they are metabolised in the body. This is extremely rare nowadays as we have a much greater understanding through experience and knowledge of dyestuffs themselves. Some acid dyes are used to colour food. We wear fabrics every day exposing our skin to dyes.

The greatest risk of disease or injury due to dyes is by ingestion or exposure to dye dust. These scenarios are normally confined to textile workers. Whereby the dye itself is normally non toxic, the molecules are metabolised (usually in the liver) where they may be broken back down to the original intermediates used in manufacture. Thus many intermediate chemicals used in dye manufacture have been identified as toxic and their use retricted. There is a growing trend among governments to ban the importation of dyes synthesised from restricted intermediates. For example: the dye CI Acid red 128 is banned in Europe as it was found to metabolise in the body back to ortho-toluidine, one of its chemical intermediates. Many intermediates used in dye manufacture such as o-toluidine, benzidine
Benzidine

Benzidine, the trivial name for 4,4'-diaminobiphenyl, is the organic compound with the chemical formula 2. This aromatic amine is a component of a test for cyanide and also in the organic synthesis of dyes....
 etc. were found to be carcinogenic. All the major chemical companies have now ceased to market these dyes. Some, however, are still produced but they are found to be totally safe when on the fiber in its final state. The use of these dyes is declining rapidly as cheap and safer alternatives are now easily available.

The incident concerning the dye Sudan 1 is an example of a suspected toxic dye finding its way into the food chain. Such incidents are extremely rare.