Direct Dyes

The direct dyes that are soluble in water and ionizable to form colored anions can directly dye the cellulose fibers or protein fibers without the action of the mordant.

This kind of dyes was developed after the find of the Congo red in 1884. The Congo red is formed by the couple of the united amine and 1-naphthylamine-4-sulfonic acid. To the 19th century, a variety of amino acid naphthol began the industrial production, and their varieties were greatly enriched. Green and black direct dyes had emerged.

The direct dyes have a higher affinity to the cellulose fibers, and the dyeing of the cellulose fibers should be carried out in a neutral or weakly alkaline medium. While the protein fibers are generally dyed in a neutral or weakly acidic medium.

The direct dyes are mostly sodium salts of aromatic compounds. They are soluble in water and their solubility increases with temperature. The direct dyes can dissociate into anions in water. The leather surface can be easily colored but it is generally difficult for the direct dyes to penetrate into the leather interior due to their big molecular weight and poor permeability. So we usually add a little ammonia before the dyeing to promote the penetration and slow down the combination with leather.

The direct dyes are sensitive to acid, and the addition of acid can make the direct dyes deposit. After dyeing, if we treat them with the fixing agent, organic acid, etc., we can improve the fastness.

The direct dyes are popular for their simple production method, complete chromatography, low cost and easy application, but their soaping fastness and light fastness are relatively poor. The direct dyes have been previously widely used for the dyeing of the cellulose fibers, protein fibers, synthetic fibers and their blended fabric. The main intermediates of many varieties of direct dyes are benzidine and its derivatives, which have been proposed as carcinogenic substances in the early 1970s and taken out of production for use. So far the production of direct dyes in the world's major companies have also been stopped and applied.

As for the different application, the direct dyes will be divided into four categories: general direct dyes, direct fast dyes, direct copper dyes and direct diazo dyes. According to the chemical structure, their types include azo, stilbene, phthalocyanine and dioxazine, of which the azo-type is the most important. In general, the main structure type of the direct dyes is azo (including monoazo and polyazo), and benzidine and its derivatives are the diazo component of many varieties. For example, Congo Red (C.I. Direct Red 28) ,the first direct dye synthesized by the N. Bottiger in 1884, has been no longer used for dyeing due to its poor light fastness, but it can be used for biological materials, colored paper as well as indicating acid agent.

The direct Fast Dyes refer to the light fastness of direct dyes in level 4 or more, and their molecular structure is more complex than the average direct dyes, such as the direct light Brilliant Blue (C.I. Direct Blue 106). The molecules of direct copper dyes contain groups that are capable of forming complex with the copper salt, such as hydroxyl group, carboxyl group or alkoxy group. They are in the mutual ortho-ortho-position of azo group. After copper treatment, the dyes can form copper complex and obtain better light fastness, such as the direct copper blue 2R (C.I. Direct Blue 151).

The molecules of fast direct diazo dyes contain an amino group. After dyeing on the fiber, the amino group may then couple with the coupled component on the fiber by diazotizationin to deepen the depth of the dye color and increases the dye fastness. Since the colors of this type of dyes show larger changes, it is difficult to control the color changes, and now they have been basically no longer used, such as direct diazo black BH (C. I. Direct Blue 2).

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Structure Chemical Name CAS MF
DIRECT FAST BROWN M DIRECT FAST BROWN M 2429-82-5 C29H19N5Na2O7S
BRILLIANT YELLOW BRILLIANT YELLOW 3051-11-4 C26H18N4Na2O8S2
Direct Black 38 Direct Black 38 1937-37-7 C34H25N9Na2O7S2
CHLORAZOL VIOLET N CHLORAZOL VIOLET N 2586-60-9 C32H22N6Na2O8S2
DIRECT PURE YELLOW 5G DIRECT PURE YELLOW 5G 10130-29-7 C24H19N4NaO5S2
Direct Yellow 12 Direct Yellow 12 2870-32-8 C30H26N4Na2O8S2
DIRECT BLUE 15 DIRECT BLUE 15 2429-74-5 C34H24N6Na4O16S4
DIRECT SCARLET B DIRECT SCARLET B 3530-19-6 C30H22N4Na2O8S2
Direct Orange  39 Direct Orange 39 1325-54-8 C12N3H10SO3Na
Direct Brown  95 Direct Brown 95 16071-86-6 C31H18CuN6O9S.2Na
Direct Black  80 Direct Black 80 8003-69-8 C36H23N8O11S3.3Na
Benzenesulfonic acid, 2-methyl-5-nitro-, alk. cond. products, reaction products with formaldehyde  Benzenesulfonic acid, 2-methyl-5-nitro-, alk. cond. products, reaction products with formaldehyde 1325-38-8
CHLORAZOL BLUE RW CHLORAZOL BLUE RW 2586-57-4 C34H25N5Na2O10S2
C.I.Direct Brown 2 C.I.Direct Brown 2
Direct Red 75 tetrasodium salt Direct Red 75 tetrasodium salt 2829-43-8 C33H22N8Na4O15S4
Direct Blue 86 Direct Blue 86 1330-38-7 C32H14CuN8Na2O6S2
tetrasodium 3,3'-[(1,6-dihydro-6-oxo-1,3,5-triazine-2,4-diyl)bis[imino(5-methoxy-2-methyl-4,1-phenylene)azo]]bis(naphthalene-1,5-disulphonate)   tetrasodium 3,3'-[(1,6-dihydro-6-oxo-1,3,5-triazine-2,4-diyl)bis[imino(5-methoxy-2-methyl-4,1-phenylene)azo]]bis(naphthalene-1,5-disulphonate) 82944-42-1 C39H29N9Na4O15S4
Direct Yellow 142 Direct Yellow 142 71902-08-4
C.I.Direct Green 1 C.I.Direct Green 1
Direct Red  83:1 Direct Red 83:1 90880-77-6
DIAMINE GREEN B DIAMINE GREEN B 4335-09-5 C34H22N8Na2O10S2
disodium 2-[4-[[1-[[(2-methoxy-5-methyl-4-sulphonatophenyl)amino]carbonyl]-2-oxopropyl]azo]phenyl]-6-methylbenzothiazole-7-sulphonate disodium 2-[4-[[1-[[(2-methoxy-5-methyl-4-sulphonatophenyl)amino]carbonyl]-2-oxopropyl]azo]phenyl]-6-methylbenzothiazole-7-sulphonate 72705-26-1 C26H22N4Na2O9S3
Direct Violet R Direct Violet R
Direct Dark Brown NM Direct Dark Brown NM 220308-48-5 C30H20O8N6Na2S
Direct Dyes Direct Dyes
CHLORANTINE FAST RED 5B CHLORANTINE FAST RED 5B 2610-11-9 C29H19N5Na2O8S2
STILBENE YELLOW STILBENE YELLOW 1325-37-7 C16H10N2Na2O7S2
Direct Orange  46 Direct Orange 46 12222-37-6 Unspecified
disodium 4-amino-5-hydroxy-3-[[4'-[(4-hydroxyphenyl)azo][1,1'-biphenyl]-4-yl]azo]-6-(phenylazo)naphthalene-2,7-disulphonate  disodium 4-amino-5-hydroxy-3-[[4'-[(4-hydroxyphenyl)azo][1,1'-biphenyl]-4-yl]azo]-6-(phenylazo)naphthalene-2,7-disulphonate 3626-28-6 C34H23N7Na2O8S2
Direct Violet B Direct Violet B
DIRECT RED 80 DIRECT RED 80 2610-10-8 C45H26N10Na6O21S6
Direct Red 23 Direct Red 23 3441-14-3 C35H25N7Na2O10S2
DIRECT BLACK DIRECT BLACK
Direct Blue 151 Direct Blue 151 110735-25-6 C34H25N5O10S2.2Na
DIRECT BLACK 38 DIRECT BLACK 38 381937-37-7
DIRECT YELLOW 29 DIRECT YELLOW 29 6537-66-2 C42H24N6Na2O6S6
SIRIUS YELLOW GC SIRIUS YELLOW GC 8005-52-5 C27H20N6Na2O8S
SIRIUS SUPRA RED VIOLET B SIRIUS SUPRA RED VIOLET B 7198-99-4 C35H26N8Na4O17S4
disodium 3-[[4-[[4-amino-6(or 7)-sulphonatonaphthyl]azo]phenyl]azo]-6-[(2,4-diaminophenyl)azo]-4-hydroxynaphthalene-2-sulphonate disodium 3-[[4-[[4-amino-6(or 7)-sulphonatonaphthyl]azo]phenyl]azo]-6-[(2,4-diaminophenyl)azo]-4-hydroxynaphthalene-2-sulphonate 8003-62-1 C32H23N9Na2O7S2
B2R DIRECT BLUE B2R B2R DIRECT BLUE B2R
Direct Dark Green NB Direct Dark Green NB C36H22O13N9S2Na
Direct Orange S Direct Orange S 3626-36-6 C33H22N6Na2O9S2
Direct Brown 44 Direct Brown 44 6252-62-6 C30H24N12Na2O6S2
Direct Yellow 120 Direct Yellow 120 12222-63-8 C27H22N6Na2O9S2
Direct Red Brown RN Direct Red Brown RN C37H28O12N12S4Na4
Direct Brown 161 Direct Brown 161
DIRECT YELLOW 117 DIRECT YELLOW 117 12217-74-2 C30H21N6Na3O11S3
Direct Blue 71 Direct Blue 71 4399-55-7 C40H23N7Na4O13S4
C.I.Direct Black 168 C.I.Direct Black 168
Direct Blue 80 Direct Blue 80 12222-00-3 C32H14Cu2N4Na4O16S4
Direct Yellow 107 Direct Yellow 107 61815-04-1 C23H38N7O17P3S
Direct Brown 116 Direct Brown 116 61724-81-0
Direct Blue 297 Direct Blue 297
Direct Yellow  96 Direct Yellow 96 61725-08-4
Direct Scarlet 4BE Direct Scarlet 4BE
Direct Bordeaux BE Direct Bordeaux BE
C.I.Direct Black 173 C.I.Direct Black 173
Direct Grey D Direct Grey D 2945-96-2 C24H22N6NaO5S
tetrasodium 2-[[4-[[4-[[1-hydroxy-6-(phenylamino)-3-sulphonato-2-naphthyl]azo]-7-sulphonato-1-naphthyl]azo]-1-naphthyl]azo]benzene-1,4-disulphonate tetrasodium 2-[[4-[[4-[[1-hydroxy-6-(phenylamino)-3-sulphonato-2-naphthyl]azo]-7-sulphonato-1-naphthyl]azo]-1-naphthyl]azo]benzene-1,4-disulphonate 6428-58-6 C42H25N7Na4O13S4
Direct Red   9 Direct Red 9 61724-94-5
DIRECT BLUE 202 DIRECT BLUE 202 107043-92-5
Direct Fast Turquoise Blue Direct Fast Turquoise Blue
Direct Red Brown RN Direct Red Brown RN C38H28N12O12S4.4Na
DIRECT BLACK 22 DIRECT BLACK 22 6473-13-8 C44H32N13Na3O11S3
Direct Yellow 132 Direct Yellow 132 61968-26-1
Direct Blue 106 Direct Blue 106 6527-70-4 C30H18Cl2N4O8S2
Direct Red 227 Direct Red 227 12222-51-4 C60H46N16O22S6.6Na
Direct Red 243 Direct Red 243 86543-85-3 C38H32N10O17S4
Direct Yellow Brown MD Direct Yellow Brown MD
Direct Blue  78 Direct Blue 78 2503-73-3 C42H25N7Na4O13S4
Direct Green  26 Direct Green 26 6388-26-7 C50H33N12Na5O18S4
Direct Red 3B Direct Red 3B
C.I.Direct Yellow 49 C.I.Direct Yellow 49
C.I. Direct Blue 85 C.I. Direct Blue 85 61724-72-9
Direct Red 239 Direct Red 239
Direct Turquoise Blue Direct Turquoise Blue
Direct Yellow 106 Direct Yellow 106 12222-60-5 C48H18N8Na6O18S6
Direct Black 168 Direct Black 168 85631-88-5 C34H24N9Na3O11S3
Copper, [29H,31H-phthalocyaninato(2-)-N29,N30,N31,N32]-, aminosulfonyl sulfo derivs., sodium salts           Copper, [29H,31H-phthalocyaninato(2-)-N29,N30,N31,N32]-, aminosulfonyl sulfo derivs., sodium salts 90295-11-7
Direct Violet  12 Direct Violet 12 2429-75-6 C32H22N6Na2O8S2
DIRECT VIOLET 51 DIRECT VIOLET 51 5489-77-0 C32H27N5Na2O8S2
Direct Red 254 Direct Red 254
tetrasodium 4,4'-[carbonylbis[imino(5-methoxy-2-methyl-4,1-phenylene)azo]]bis[5-hydroxynaphthalene-2,7-disulphonate]  tetrasodium 4,4'-[carbonylbis[imino(5-methoxy-2-methyl-4,1-phenylene)azo]]bis[5-hydroxynaphthalene-2,7-disulphonate] 1937-34-4 C37H28N6Na4O17S4
C.I. Direct Yellow 44 (29000) C.I. Direct Yellow 44 (29000)
DIRECT GREEN 1 DIRECT GREEN 1
C.I.Direct Black 168 C.I.Direct Black 168
Direct Red 45 Direct Red 45 C24H15N3Na2O7S3
REMASTRAL BLUE FFRL REMASTRAL BLUE FFRL 1324-58-9 C34H19Cl2N4Na3O11S3
DIRECT DYES DIRECT DYES
Direct Yellow  24 Direct Yellow 24 6486-29-9 C17H16N2O3
Direct Green NB Direct Green NB
Direct Scarlet G Direct Scarlet G
Direct Yellow Brown 3G Direct Yellow Brown 3G
Direct Green DB Direct Green DB
Direct Violet 9 Direct Violet 9 6227-14-1 C30H23N5Na2O8S2
Direct Violet 66 Direct Violet 66 6798-03-4 C32H19Cu2N7Na2O14S4
Benzoic acid, 5-4-4-4-(4-amino-9,10-dihydro-9,10-dioxo-3-sulfo-1-anthracenyl)amino-2-sulfophenylamino-6-(phenylamino)-1,3,5-triazin-2-ylaminophenylazo-2-hydroxy-, trisodium salt Benzoic acid, 5-4-4-4-(4-amino-9,10-dihydro-9,10-dioxo-3-sulfo-1-anthracenyl)amino-2-sulfophenylamino-6-(phenylamino)-1,3,5-triazin-2-ylaminophenylazo-2-hydroxy-, trisodium salt 6471-09-6 C42H27N10O11S2.3Na
Direct Red  31 Direct Red 31 5001-72-9 C32H21N5Na2O8S2
tetrasodium [mu-[[7,7'-(carbonyldiimino)bis[4-hydroxy-3-[(2-hydroxy-5-sulphophenyl)azo]naphthalene-2-sulphonato]](8-)]]dicuprate(4-) tetrasodium [mu-[[7,7'-(carbonyldiimino)bis[4-hydroxy-3-[(2-hydroxy-5-sulphophenyl)azo]naphthalene-2-sulphonato]](8-)]]dicuprate(4-) 15418-16-3 C33H20N6O17S4.4Na
Direct Brown 223 Direct Brown 223 76930-14-8
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