Mordant Dyes Name : MAZADUL HASAN SHESHIR ID: 2010000400008 Batch: 13th Batch (Session 2009-2013) Department: Wet Processing Technology Email: mazadulhasan@yahoo.com Blog: www. Textilelab.blogspot.com Southeast University Department of Textile Engineering PREPARED BY ©right What is Mordant? A mordant is a chemical binding agent that adheres well to both the fibers and the dye. A mordant is a substance used to set dyes on fabrics by forming a coordination complex with the dye which then attaches to the fabric. A mordant is always a polyvalent metal ion. The resulting coordination complex of dye and ion is colloidal and can be either acidic alkaline. Mordants can be added before, during or after the dyeing process. Most recipes use mordanting before dyeing. The type of mordant used can change the color of both the dye-plus-mordant solution and influence the shade of the final product. Some mordants (FeSO4) darkent the color, some (SnCl2) brighten the color. They improve light and wash fastness properties. What is Mordant? Mordanting Mordants are used to improve the bond between the dye and the fabric, as well as extending the range of hues that can be obtained from the dyestuff. To make the mordant take better, an ‘assistant’ can be added, which may mean less mordant is needed. The main problem is that typical mordants are based on heavy metals which are extremely toxic, causing environmental problems and presenting health threats to workers if not properly trained. The main mordants are alum, tin, iron, chrome and copper: alum is non-toxic but is an irritant if inhaled, chrome is poisonous and can provoke an allergic reaction to anyone with sensitive skin, copper is poisonous and has little effect on vegetable fibres, tin is poisonous and an irritant and, despite being used in small quantities, iron is harmful if ingested. Mordants can be obtained from plants, such as oxalic acid which is found in rhubarb leaves, alum which comes from clubmoss, and tannin from oak galls and sumac leaves. As a general rule, the weight of the mordant and the weight of the yarn to be dyed are the same. It takes around 6-8 litres of water to mordant enough yarn for one t-shirt by hand. Vegetable fibres take longer to prepare than animal fibres, making the former’s preparation process more expensive. Vegetable fibres also usually need to be treated with tannic acid before and after scouring. Mordanting Mordants are used to set the color when using natural dyes. Different mordants will give different results. Alum (Aluminium Potassium Sulfate): This is the most widely used mordant. The compound is the hydrated aluminium potassium sulfate with the formula KAl(SO4)2.12H2O. Chrome (Potassium Dichromate, K2Cr2O7): Chrome brightens dye colors and is more commonly used with wool than with any other fiber. Extremely toxic material, therefore chrome should not be inhaled and gloves should be worn while working with chrome. Left over mordant water should be disposed of at a chemical waste disposal site and treated as hazardous waste. Common Dye Mordants Tara Powder (CaesalpiniaSpinosa): Tara powder is a natural tannin product. It is needed for darker colors on cotton, linen and hemp. Tartaric Acid: A must for cochineal. This mordant will expand the cochineal colors. Tin (Stannous Chloride): Tin will give extra bright colors to reds, oranges and yellows on protein fibers. Using too much will make wool and silk brittle. To avoid this you can add a pinche of tin at the end of the dying time with fiber that was pre-mordanted with alum. Tin is not commonly used with cellulose fibers. Copper (Copper Sulfate): This mordant is used to bring out the greens in dyes. It will also darken the dye colors. Common Dye Mordants Mordant Dyes: Dyes which have no affinity towards textile fibers are attached with the fiber with the help of mordants are known as mordant dyes. Most commonly used mordants are inorganic chromium, so sometimes these dyes are called chrome dyes. Chrome dye is an acid dye, which forms a chelate complex with chromium atoms. Restricted use due to eco-toxicity problems. These dyes have some mordant attracting groups which have some influence on the metal ions. A metal ion takes the place of hydrogen in the –OH or –COOH group in azo dyes. The mordants have affinity both for fiber and dye. So, dyes which have no affinity to fibers can be applied by using suitable modant, as dyes have mordant attracting groups. Fibers most readily dyed with mordant dyes are wool, modacrylic and nylon fibers, in wool dyeing only chromium salt are of importance so mordant dyes used for woold dyeing are usually called chrome dyes. Mordant Dyes: Properties of Mordant Dyes 1. Mordant dyes have no affinity for textile fibers. They are attached to the fibers with the help of mordants. These mordants have affinity both for the dye and fiber. 2. Mordant dyes are capable of combining with metallic oxides to form insoluble color lakes. 3. Mordant dyes may be natural or synthetic. Natural mordant dyes are obtained from madder, cochineal, logwood etc. Synthetic mordant dyes are marketed as pastes or powders. 4. Mordant dyes are mostly applied on natural protein fibers, nylon and modacrylic fibers. 5. The light, wash fastness of mordant dyes is very good with rating from 4 – 6. 6. Most mordant dyes are soluble in cold water. 7. The main feature of the mordant dye molecule is that there remains a metal ion (mainly chromium) as a central atom which is bonded to neighbouring –OH, -COOH or azo group. Properties of Mordant Dyes Vibrant colours from Natural dyes The three methods used for mordanting are: 1. Pre-mordanting (Chrome): The substance is treated with the mordant and then dyed. 2. Meta-mordanting (Metachrome): The mordant is added in the bath itself. 3. Post-mordanting (Afterchrome): The dyed material is treated with a mordant. The type of mordant used changes the shade obtained after dyeing and also affects the fastness property of the dye. The three methods used for mordanting are: [...]... chromate anion, CrO4 2- and usually have an intense yellow color Dichromate salts contain the dichromate anion Cr2O7 2- and usually have an intense orange color Brief Description of Methods of Application Post-mordanting (After-chrome Process): This is the oldest and the most common mordant dyeing process Here, the material is first dyed with an acid dye and then mordanting with chromium is carried out in...Brief Description of Methods of Application Pre-Mordanting (Chrome Mordant Process): This is a two bath process In this process the material is impregnated with an insoluble chromium hydrate ( Chromic Oxide Cr2O3.2H2O ) and then dyeing is done in a separate bath Chrome hydrate is a hydrated form of chromic oxide bound with more or less two molecules of water It is insoluble in water and compatible with... Advantages Disadvantages 1 2 3 4 Advantages Dyeing is carried in one stage Less time required High Production Easier shade matching Disadvantages 1 Range of shades is limited 2 In case of unlevel dyeing it is impossible to correct it Mordanting Cotton Mordanting Cotton Cotton is very time consuming to mordant First it needs scouring and then it needs a three step process, with consecutive mordant baths... Agent Scoured wool is treated in a bath containing the abouve chemicals at 40⁰C for 20 min After 20 min the dissolved dye is added and the liquor is brought to the boil over a period of 45 min and retained at this temperature for further 60 – 90 min In case of dyeing heavy shades it is advisable to complete exhaustion by adding 0.5 – 1% acetic acid (40%) 30 minutes before the dyeing is finished Ammonium... Brief Description of Methods of Application Meta-mordanting (Chromate Process): In meta-chrome process dyeing and mordanting are carried out simultaneously in the same bath Here the mordant is present in the form of chromate which does not form the lake with the dye and which is gradually converted into dichromate The pH of the bath is kept around 6 – 7 This method has the advantage of facilitating shading... for 20 minutes 1 – 1.5% dye (owf) is added in the solution with Calcium Acetate at 25⁰C for 30 min The fabric is hot rinsed (70⁰C) for 30 minutes Finally the fabric is washed with soap solution and water and then dried Structures of Mordant Dyes Structures of Mordant Dyes Structures of Mordant Dyes ... sure it is being adequeately scoured After two hours remove the saucepan from the heat source and allow the fabric to cool down until it can be safely removed from the water Finally rinse the fabric If necessary the process may be repeated Application of Dye and Mordant on Cotton Cloth Mordanting Cotton with Alum-Tannin-Alum: 100 gm of fabric is used in a 10 liter saucepan Total weights to mordant. .. well to remove any unfixed alum Alizarine Dye Alizarine Dye Among the few naturally occurring dyes madder is extensively used to produce bright red shades It is named as Turkey Red as it (madder red) was best dyed in Turkey Alizarin is an organic compound that is historically important as a prominent dye It is an anthraquinone originally derived from the root of the madder plant In 1869, it became the... separate bath or mordanting can be done in the same after exhaustion of the dye has been completed Meta-Chrome Dyeing Process There are a certain number of acid mordant dyes which can be dyed and mordanted simultaneously by using metachromemordants contain one part of sodium or potassium dichromate with two parts of ammonium sulphates Common recipe: Amount Material 2 – 5% Metachrome Mordants 5 – 10%... container with boiling water 3 Add tannic acid to pot and dissolve well 4 Add pre-wetted cotton 5 Simmer for one hour, leave for 24 hours 6 Wring well and dry 7 Leave the fabric to age for at least a week 8 Wash the fabric well 9 Bath 3 (Second Alum Bath): 10 Repeat alum mordanting as described for Bath 1 Mordanting Silk 1 De-gummed silk, that is “prepared for Dyeing” (PFD), should be used 2 Weigh the . –OH, -COOH or azo group. Properties of Mordant Dyes Vibrant colours from Natural dyes The three methods used for mordanting are: 1. Pre-mordanting (Chrome): The substance is treated with the mordant. then dyed. 2. Meta-mordanting (Metachrome): The mordant is added in the bath itself. 3. Post-mordanting (Afterchrome): The dyed material is treated with a mordant. The type of mordant used changes. Application Post-mordanting (After-chrome Process): This is the oldest and the most common mordant dyeing process. Here, the material is first dyed with an acid dye and then mordanting with chromium is