Acid dye are highly soluble in water compare with basic dye. It is give good effect on protein fibers such as wool, silk acrylic and nylon.
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What are Acid Dyes?
Acid dyes are windly use for colouration of protein fibers. such as wool, silk, acrylic and nylon. and these proteins fibers contain sulphonic acid groups.
Dye solubility increase in water with the help of sulphonic acid groups. and it’s gives dye molecules Negative charge and fibre are given the positive charge and this both charge make more interacts with the dye.
This process is indicated ionic interaction and this process is possible with some especial forces such as Vander Waals and hydrogen bonding because both force is formed between the fibre and dyes.
If we want to compare between the acid dye and basic dye then the first difference is solubility, and other difference is light fastness properties. I mean to say that, Acid dye are highly soluble in water compare with basic dye. and acid dye have good light fastness Properties compare with basic dyes.
Properties of acid dye
- Acid dyes are highly soluble in water compare with basic dyes.
- Acid dyes is properly work on proteins fibres such as wool, silk, nylon.
- Acid dye have no affinity for cellulosic materials. Hence, acid dye is not suitable for cellulosic materials.
- Acid dyes is more suitable and profitable for proteins fibres such as silk dyeing, wool dyeing, nylon dyeing and acrylic dyeing.
- Acid dyes are properly ionic in nature.
- Acid dyes is more react on to the proteins fibres with the help of Van der Waals and hydrogen bonds because it’s formed between fibre and dyes.
- Light fastness is good in case of acid dye but in case of basic dye light fastness is poor.
- In case of acid dyes, uses strong acidic to netural pH bath.
- Acid dyes is more effective for proteins fibres.
- Acid dye is not able to dyeing of cellulose materials.
Classification of acid dyes
• levelling dyes
• milling dyes
• super milling dyes
List Of Acid Dyes
• BEMACID CA (half milling agent)
• BEMACID CM (milling agent)
• Acid Red GTR
• Nentlen Nevy Blue RL
• Nentlen Black C
• Alizarine cyanine green G
• Acid yellow 4R
• Acid blue 25
• Acid blue 40
• Acid orange 7
• Acid orange 5
• Acid blue 117
• Very good wet fastness and masking properties and light fastness is also good.
Role of pH in acid dyeing
• pH depend upon quality of dyes.
• fixation, absorption and exhaustion all are depend upon pH.
• pH boost absorption or fixation.
• In case of dyeing of wool, pH play very important role during dyeing, the role of pH is also depends upon the quality of dyes if quality is not proper then fixation is not properly, I mean, fixation of materials is not good, it may show uneven dyeing occurs on to the materials.
• Don’t used low pH and high pH because it increases chances of damage for materials. So maintain pH depend upon materials.
Role of Glauber’s salt in acid dyeing
• Role of Glauber’s salt is very important in dyeing of wool.
• don’t used more glauber’s salt in solutions it effects on rubbing fastness.
• it is also called levelling agent.
Effect of temperature on Wool Materials,
• If dyeing process is carried out at boiling temperature then no chances of damaged for wool materials they are always protected wool materials.
• But if dyeing process is carried out at high temperatures then the chances of dye stuff diffuse faster in to the materials and gives good penatration and it give better shade.
• it also give good fastness properties but if dyeing time will increase with high temperature then the chances of damaged for wool materials.
1. Dyeing Of wool with acid dye
Acid dye is more useful and it give even dyeing performance for proteins fibres such as, Wool dyeing, silk dyeing and acrylic dyeing. and you know, Acid dye is also called ainonic dyes. acid dyes has no more affinity for cellulosic materials so acid dyes is not used for cellulosic materials. Because poor shade, poor fastness properties will occur after dyeing. But acid dyes is regularly or industrial used for proteins fibres such as wool, silk, acrylic etc. In this case good light fastness properties will occur after dyeing.
First off all put the all recipe in dyeing bath. then after 5 mint put the sample or materials in dyeing bath and after 5 mint raised the temp at 100°C and continue Dyeing is done for 30-60 mint at 100°C.after dyeing cool – drain- cold wash-soaping with no ionic soap solutions at 60°C for 20 mint. Again wash with hot water and dry the sample. This is complete process of dyeing of wool with acid dye.
2. Dyeing of nylon/wool blend with acid dye
• dye or metal complex – x %
• Glablur salt – 10 %
• Formic acid (85%) – 4 %
• levelling agent ( pale shade) – 7 %
In this dyeing process, first of all set the dye bath with the help of dyeing recipe and then after 5 mint interduce the goods in dye bath and temperature should be at 60°C. and then after 5 mint raise the temperature 80°C then dyeing is done for 40 to 45mint and then again raise the temperature at 100°C for 1hours (60mint). and then cool – drain – wash – Soap – wash – dry.
3. Dyeing of silk with acid dye
• Acid dye – x %
• Acetic acid – 2 – 4 %
• Glablur salt – 5 – 10 %
• pH – 4 – 5
• A – First prepared , Acetic acid + Glablur salt.
• B – then dye solution should be add in dyeing bath for dyeing.
In this dyeing process, first set the dye bath at 40 to 45 °C for dyeing then interduce the mixture of acetic acid + Glablur salt in dyeing bath then interduce dye solution in dyeing bath and temperature of dye bath should be 40 to 45°C then dyeing is carried out for 45 mint and then raise the temperature at 100°C for 30 – 90 mint after complete dyeing then cool – darin – wash – and dry.
Mono azo acid dye
Example; – Methyl orange : it is prepared by coupling sulphanilic acid with dimethyl aniline. it is prepared by following reaction as shown in reaction.
In this reaction, sulphanilic acid react with dimethyl aniline and diazotisation with the prencess of con HCl/ NaNo2 and then acidic pH then coupling after coupling then it is directly given methyl orange.
Application of Acid Dye
Acid dyes are water-soluble synthetic dyes that are commonly used to dye protein fibers such as silk, wool, and nylon.
They are called acid dyes because they are typically applied in an acidic dye bath, which helps to enhance their colorfastness and the affinity for protein fibers.
Acid dyes are widely used in the textile industry and
Acid dye have several applications, including
- Textile dyeing: Acid dyes are extensively used for dyeing silk, wool, and nylon fabrics. They provide vibrant and intense colors and have good lightfastness and washfastness properties. Acid dyes are particularly suitable for dyeing protein fibers because they form strong ionic bonds with the fibers’ amino acid groups.
- Leather dyeing: Acid dyes are also used for dyeing leather, especially for suede and nubuck finishes. The dyes penetrate the surface of the leather and bond with the protein fibers, resulting in a uniform and colorfast dyeing.
- Paper dyeing: Acid dyes are employed in the paper industry to color specialty papers, such as decorative papers, tissue papers, and art papers. The dyes are often applied in a pulp or dye bath during the papermaking process.
- Inkjet printing: Acid dyes are utilized in inkjet printing systems for printing on protein fiber-based materials, such as silk and wool. The dyes are dissolved in a carrier fluid and deposited onto the fabric using an inkjet printer. Acid dyes are preferred for inkjet printing due to their water solubility and ability to produce vivid and colorfast prints.
- Biological staining: Acid dyes find applications in biological and histological staining techniques. They are used to color biological specimens, such as cells and tissues, for microscopic examination. Acid dyes can selectively stain different cellular components and aid in identifying specific structures or substances within the specimens.
It’s important to note that acid dyes are not suitable for dyeing plant-based fibers like cotton or linen.
These fibers require different types of dyes, such as reactive dyes or direct dyes, which have a different chemical composition and reactivity with cellulose fibers.