Dyestuff Industry (Part - 2) | Chemical Technology - Chemical Engineering PDF Download

Gamma Acid 

Gamma acid belongs to the class of hydroxyl naphthalene mono sulphonic acid is a key intermediate used as diazo and coupling component for the manufacture of commercial dyes belonging to the class of direct, acid, acid-modrant and reactive dyes 

Manufacturing Process:

G-salt is subjected to Bucherer reaction with liquor ammonia in presence of sodium bisulphite in aqueous solution under pressure in an autoclave to obtain the amido G-salt. Which then subjected to alkali fusion with excesses of caustic soda flakes then neutralized with 40% sulphuric acid to isolate the Gamma acid. 

Chemical Reactions 

Tobias Acid 

Tobias acid is an important dye intermediate belonging to the class of amino naphthalene mono sulphonic acid. It’s used in the manufacture of a number of reactive, direct, acid and acidmordant dyes. 

Manufacturing Process:

Oxy-Tobias acid undergoes amidation by Bucherer reaction in the presence of ammonia, ammonium sulphite and ammonium sulphate, After amidation to bias acid formed in dissolved state as its ammonium salt, then subjected to acidification with sulphuric acid for isolate the Tobias acid. 

Chemical Reactions 

Metanillic Acid (6-Chloro metanillic acid) 

6-Chloro metanillic acid is a key diazo-component used as an intermediate in the manufacture of a variety of direct and acid dyes which are used to dye cotton and wool. 

Manufacturing Process: 

Ortho nitro chlorobenzene (ONCB) is sulphonated with oleum to afford ONCB parasulphonic acid (ONCB PSA) , then reduced with iron and concentrated hydrocholoric acid at 95-100Oc in 5 to 6 h. The filtrate is acidified to afford the 6-Chloro metanillic acid which is centrifuged and dried 

Chemical Reactions

β-NAPHTHOL

β-Naphthol is an important dye intermediate used as a coupling component for manufacture of widely used azo dyes. 

Manufacturing Process:

Naphthalene is sulphonated with concentrated sulphuric acid gives naphthalene -1-sulphonic acid. The diluted mass is neutralized with aqueous solution of sodium sulphite containing sodium sulphate 

Chemical Reaction

Anthraquinone -1- Sulphonic Acid Sodium Salt 

9, 10-Anthraquinone and all its derivatives are important building block for a variety of dyestuffs, in particular for disperse, solvent and acid dyes.

Manufacturing Process: 

Phthalate anhydride is treated with benzene in excess of the AlCl3 as a catalyst gives orthobenzoyl benzoic acid (BOB) in form of Al complex. BOB future subjected to cyclization and sulphonation using in the presence of HgO as a catalyst to obtain anthraquinone-1-sulphonic acid.

Chemical Reactions 

Anthraquinone -1- Sulphonic Acid Amminium Salt

Manufacturing Process:

Mercury is heated into 20% oleum at 80^oC for 3 h then anthraquinone (AQ) is heated at 130^oC for 3 h to complete sulphonation of AQ after filtration the filtrate neutrilize with ammonia and after cooling 30oC precipitate out anthraquinone -1- sulphonic acid ammonium salt

Chemical Reactions . 

Resorcinol 

Resorcinol is a key dyestuff intermediate widely used as a coupling component for a variety of azo dyes belonging to various classes such as direct, acid, reactive and disperse dyes. It is also an important monomer for the production of polymers especially polyesters. Derivatives of resorcinol have also found use as sun screen agents and UV stabilizers. 

Manufacturing Process: 

Benzene is sulphonated using liquid sulphur trioxide in presence of sulphuric acid and sodium sulphate. The benzene disulphonic acid (BDSA) is converted to its disodium salt using soda ash, which then treated sulphuric acid then resorcinol is extracted with butyl acetate.

Chemical Reaction 

Dark Blue Bo:

Dark blue (BO) is a vat dye containing two or more keto groups which has great affinity for cellulosic fibre.

Violanthrone

Manufacturing Process

Naphthalene and sodium acetate with molten mixture of NaOH and KOH are added in 1.25h at 185^oC then crude benzanthrone heated over 4 h at 235^oC. The dye which separates out is filtered off through filter press and wash well with hot water.