natural and mordant dyes

textile coloration

1. Hawassa university iot department of textile and garment engineering Textile coloration seminar Natural and mordant dyes 2019 To Mr. Jemal.E BY PEER-I MEMBERS

2. introduction The production and coloration of fabric has recorded history. The natural as well as synthetic colorants were used in the history of coloration. In case of natural mineral paints were the first to be used. These colorants bleed out of the material dyed with them. In addition to these sources natural dyes were extracted from plants and animals with water and sometimes in the process called fermentation. In the process the fabric were dyed by soaking in aqueous extract and drying it.

3. Continued… These dyes had only a limited range of dull Colors and the dyeing’s invariably had poor fastness to washing and sunlight. Moreover most natural dyes also lacked substantively for fibres such as wool and cotton. The poor substantively and fastness properties of natural dyes often improved if the fabric was first treated with a solution containing a salt of, for example, iron, copper or tin. These metal salts were called mordant(s) When the pre- mordanted fabric was soaked in a bath of a suitable natural dye, the dye penetrated into the fibres and reacted with the metal ions present. This reaction decreased the water solubility of the dye so the color was less likely to bleed out on washing

4. Continued… A few natural dyes gave better quality dyeings of cotton or wool, but involved long and difficult processes. Some examples of natural dyes: Indigo, extracted from leaves of the plant and from Mediterranean sea snails are water insoluble pigments called vat dyes . The dyeing process involves three stages

5. Natural dyes and their sources Definition: Natural dyes are those dyes derived from plants, animals and mineral Plant based natural dyes Indigo: derived from indigofera tincitoria which is water insoluble and needs reduction . Application : blue jeans dyeing

6. Continued… Woad: Leaves contain same chemical as indigo but in lower amounts Grown for blue dyestuff Application: Celtic war paint and tattoos

7. Continued… Madder: root of madder plant found in and Europe and Asia Also called “Turkey Red ” Chemically — Alizarin and Pupurin.

8. Continued… Animal based natural dyes Dyes from Snails these dyes are those obtained from snails. the amount of dye obtained per a snail is too small that is 9000 snails can only give us 1 gram of the dye. also called ‘Royal Blue’ and used to dye wool and silk. chemically it is 6,6’-dibromoindigo

9. CONTINUED… Sepia: Blue-black “ink” isolated from cuttle fish or squid Used in ink drawings and watercolors Somewhat light sensitive Dyes from Bugs Kermes — the most ancient dye in Europe 70,000 female oak beetles produce 1 pound dye Cochineal — Mexico and Central America Mexican cactus beetle.

10. classification

11. Continued…

12. Three Classes of Natural Dyes Substantive dyes Easiest to apply to fibers No need to use other substances to enhance dyeing Vat dyes Involve chemical change of dye through “fermentation” or “chemical reduction” to make it soluble Adjective dyes (Mordant dyes) Require another chemical to develop color and “fix” it to the fiber

13. Mordanting of textiles for natural dyeing Mordants: are those fixative substances used to fix dyestuffs on the textile materials. Mordanting: is the process of Appling those substances(mordant) on the dye(specially plant based natural dyes) to make them more substantive to textile materials. M

14. Extraction of natural dyes Both traditional and modern( innovative ) systems can be used. Traditional method: The traditional method used to extract the dyestuffs where the plant material is added directly to the dye bath. Then the material soaked into the bath where natural dyes are added takes the color and particles will be separated from the material later on.

15. Continued… The disadvantages of traditional method are: The plant material has to be separated from the textile It is not applicable to modern textile fabrication machines Hard plant material such as madder roots or barks difficult to extract   Due to the limitations above engineers began to looks for another better system which can solve the problems and add more values to the process. As a result of this innovative extraction systems came to be applied.

16. Innovative extraction systems The innovative systems are those employing technological devices in the process of extracting natural dyes from their sources. It involves: Supercritical fluid (CO 2 ) extraction Subcritical water extraction Soxhlet extraction Note: these systems can be classified as Alcoholic and Aqueous extraction. Alcoholic : uses methanol Aqueous : uses water

17. 1-Supercritical fluid (CO 2 ) extraction The procedure: natural product is powdered and charged into the extractor Carbon dioxide is fed to the extractor through a high‐pressure pump (100‐350 bar ).. The extract charged carbon dioxide is sent to a separator (60‐120 bar) via a pressure reduction value and at reduced temperature and pressure conditions the extract precipitates out in the separator

18. 2-Subcritical water extraction The procedure : The water was purged with nitrogen to remove dissolved oxygen prior to the extraction Deoxygenated water was used in an HPLC (high performance liquid chromatography) pump programmed for a constant flow of 1–3 ml/min‐1. A 10.4 ml extraction cell equipped with 0.5 m frit at the inlet and outlet was connected to a 1 m cooling loop (in ice water) outside of the oven. A pressure control valve was placed between the cooling loop and the collection vial.

19. 3-soxhlet extraction Soxhlet extraction was carried out for colorant identification The procedure: dried plant parts were put into thistle of soxhlet extractor and methanol was used as solvent places a specialized piece of glassware in‐between a flask and a condenser. The refluxing solvent repeatedly washes the solid extracting the desired compound into the flask.

20. Continued… Methods of mordanting: There are three ways of mordanting Pre‐mordanting , where the mordant is applied first, followed by dyeing. Post‐mordanting , where the dyeing is done first and then mordanting is carried out. Simultaneous mordanting , where mordant and dye are mixed together and applied . Mechanism: The fabric is impregnated with the mordant, then during the dyeing process the dye reacts with the mordant, forming a chemical bond and attaching it firmly to the fabric.

21. Continued… Some mordants Alum ( potassium aluminum sulfate ): alum does not affect color. it is usually used with cream of tartar, which helps evenness and brightens slightly. three 3:1 of alum: cream of tartar is a good start. if heavy wool is used 4 of alum can be used safely. too much alum makes wool sticky Iron (ferrous sulfate ) or copperas: It will sadden or darken colors, bringing out green shades . Wool is dyed before mordanting when dark shades are needed. Too much iron hardens wool

22. Continued… Tin (stannous chloride) blooms or brightens colors, especially reds, oranges and yellows. Almost always used with cream of tartar —Simmering for an hour and rinse in soapy water before dyeing Too much tin makes wool brittle Blue vitriol (copper sulfate) saddens colors and brings out greens one ounce will mordant a pound of wool.

23. Continued… Bonds formed in the process: Two types of bonds are involved covalent bond with usually hydroxyl oxygen and the metal atom. a coordinate bond with the metal with the double bonded other oxygen also referred as “ chelation. Process control: Varying the amount of mordant with the dye is a way to exert some control over the change in hue color

24. TREATMENT OF FABRIC BEFORE DYEING Treatment procedure: Another options: 1 . Enzymes like amylase, trypsin, cellulose and 2. Polyethylene glycol (PEG). Note: Both these types are used as depth improver for dye fixation .  

25. TYPICAL DYEING PROCESS FOR COTTON Requirements: ‐ Natural Dye Mordants : ‐Alum, Ferrous sulphate, Stannous chloride Soft water(hardness less than 50‐ppm .) Dye pot: It should be in Stainless steel or glass or porcelain. Temperature indicator / thermometer Heating medium

26. Continued… Preparing the RFD (Ready for Dyeing) You can apply your own process. It is advisable that the material should be at least semi (Half) bleached . Pre Mordanting :‐ ( If Required) Add required quantity of required mordant (2‐4%) in lukewarm water, stir well and filter it. Raise the temperature of solution to 80oC. Immerse the textile RFD material in the solution and stirrer the same so that material should be in movement for 20 –25 min. Drain the liquor and slightly squeeze the mordanted material and don’t wash. After mordanted textile material, and proceed for next Mordanting or dyeing as per recipe.

27. Continued… Dyeing Add the required quantity of dye in lukewarm water, stir well and filter it(if simultaneous Mordanting is required add the required quantity of mordant and dye in the same dye bath before immersing the material in it) and Raise the temperature of solution to 80oC. Immerse the above mordent textile materials in the dye bath for 30 –35 min . Post Mordanting :-( If Required ) Drain the liquor and slightly squeeze the dyed material and don’t wash. Add required quantity of required mordant in lukewarm water, stir well, filter it and add to dye bath. And Raise the temperature of solution to 80oC. Immerse the dyed textile material in the solution and stirrer the same so that material should be in movement for 20 –25 min. In case of using Ferrous sulphate as post mordant the mordanting should be conducted at ambient temperature.  

28. Continued… Post Treatment: ‐ Drain the liquor and slightly squeeze the dyed material. Wash the dyed material with plain water. Wash the dyed material with 0.5 gplnon ionic detergent at 60oC. Again drain the liquor and slightly squeeze and wash the dyed material with plain water until the detergent rinse out. Treat the material with your own method of fixing agent and softener as you required.

29. Silk dyeing procedure This fiber follows the same procedure as cotton do with some modification in dyeing sage. Dyeing Add the required quantity of dye in lukewarm water , stir well and filter it(if simultaneous Mordanting is required add the required quantity of mordant and dye in the same dye bath before immersing the material in it) Raise the temperature of solution to 80oC and maintain the pH of the bath from 3.0 to 3.5 by acetic acid (if required). Immerse the above mordent textile materials in the dye bath for 30 –35 min . During the entire course of dyeing the material should be in movement

30. Natural Vs. synthetic dyes Natural dyes Synthetic dyes Biodegradable then easier to remove from the material Stable in any Redox reaction and the difficult to remove from textile material Have no health hazardous Have health hazardous Colors obtained from natural sources tend to be earthy and subtle Synthetic dyes often produce garish, stark or muddy colors. Poor fastness properties Good fastness properties Natural dye materials are scarce and expensive are readily available at low cost Have renewable sources. Haven’t such souces Lower color yield Better color yield

31. Continued… Advantage Disadvantage They are obtained from renewable sources. lower substantivty, Poor fastness Natural dyes cause no disposal problems, as they are biodegradable mordant is required to fix the dye in the fabric. no or mild reactions are involved in their preparation However they have poor wash fastness ratings, they do not stain the adjacent fabrics Color yield is lower than that of synthetic dyes .It is possible to obtain a full range of colors using various mordants difficult to standardize a recipe for the use of natural dyes, as the natural dyeing process

32. Application of natural dyes: Used to color textiles, food substances and leather. Indigo dyes are used to make hair dyes as well as mediated hair oil. Most commonly used in cosmetics industry due to side effect, UV radiation protection, and anti-aging properties. Also used as PH indicators. Are used for food coloration

33. INTRODUCTION TO MORDANT DYES Dyestuffs that require use of a mordant. There are very few synthetic dyestuffs currently in use that require a separate mordant, except for some dyes for wool, where mordant dyes are still quite popular. Since chromium is almost exclusively used as the mordant on wool, chrome dye has become essentially synonymous with mordant dye . These dyes have some mordant attracting groups which have some influence on the metal ions. In the process of bond formation the metal ions take the place of oxygen in –OH, -COOH in azo dyes. These are special acid dyes in which certain metal atom can be introduced during dyeing. These are water soluble dyes and affinity for silk , wool and polyamides.

34. Properties of Mordant Dyes These dyes are economical dyes and are generally used to produce dark shades such as dark green dark blues and blacks. These dyes have good leveling and color fastness properties. The interaction between fiber and dye is established through very strong ionic bonds , which are formed between the anionic groups of the colorant and ammonium cations on the fibers Chromium or the metal ion acts as bridge between the dye and fiber, which gives rise to a very strong linkage, resulting into excellent fastness properties.

35. Mechanism of Dyeing Since these are a special class of acid dyes ,which are soluble in water and applied to the fiber from an acidic bath. When a solution of an acid mordant dye is mixed with a solution of potassium dichromate in the presence of sulfuric acid, chromium ion from dichromate forms a complex with the dyes, this complex is insoluble in water, and hence precipitates on the fiber

36. Application of Mordant Dyes Is the way how metal-dye complex is formed. We can use mordant dyes dyeing process as an alternative process of natural dyeing due to process similarity. In natural dyeing the dyes are treated with the fixative substances so called mordants and made substantive to make it easier to dye. In mordant dyeing the material is treated with metal mordants to make metal-dye complex which is insoluble on fiber

37. Methods of mordants application We can use one of the three: Chrome – Mordant method After chrome method Meta chrome method Chrome-mordant method: T he fiber is first treated with potassium dichromate in the neutral bath or in the presence of either sulfuric or formic or oxalic acid . it is taken out , squeezed and entered in the dye bath containing acid mordant dye. The dye form an insoluble complex with chrome present on the fiber

38. Continued… After chrome method: the substrate is first treated with the dye , the dye is exhausted by the addition of an acid after complete exhaustion the material is taken out squeezed and then run in a solution containing potassium dichromate and an acid. Metal dye complex is formed on the fiber , which is insoluble.

39. Continued… Meta Chrome Process: Step-I the material is treated with in a bath containing acid mordant dye , potassium dichromate and ammonium sulphate. The dye along with potassium dichromate and ammonium sulphate got absorbed by the fiber and evenly distributed Step-II when the dye bath is heated , ammonium sulphate is converts into ammonia and H2SO4, which makes the bath strongly acidic and potassium dichromate in the presence of strong acid now react with the dye molecule forming an insoluble complex on the fiber .

40.   wool dyeing cycle with chrome dyes Common recipe : Process description: Scoured wool is treated in the bath that contains the above recipe at 40 C 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 that temperature for 60-90 min. Then for complete exhaustion to occur the acetic acid is added in case of heavy shade formation is compulsory(lasts for 30 min.) Amount Materials 2-5 % Meta-chrome mordant 5-10 % Glauber’s salt 250-500 gm./l Surface active agent o.5-1 % Acetic acid (40 %)

41. Graphical description of the dyeing cycle Here: A= Gluber salt+Acetic acid+Leveling agent B= Dye C= Potassium Dichromate D=Acid

42. Properties of mordant dyes: They don’t have affinity to the textile materials They are capable of combining with metallic oxides an from insoluble color lakes. They can be natural or synthetic Are applied mostly on wool, nylon and acrylic fibers. Have good washing as well as light fastness. Most of them are soluble in water. Have metal ions ,mostly chromium that get bonded with neighboring groups like -OH , -COOH, AZO.  

43. Advantage and disadvantage Advantages Disadvantages Dyeing takes place in one stage Range of shade is limited Higher production In case of unleveled dyeing it is difficult to correct. Easier shade matching   Less time needed in the process  

44. Conclusion: Textile coloration can be done with the application of natural(dyes from plants, animals and minerals) or synthetics that can be prepared. In the process of dyeing with natural dyes colors can bleed out of the material easily due to this involvement of certain fixative substance called mordant is needed. The reaction that the dye makes with the fiber in the presence of mordant is fast to water and sun light. Another category of dye used in the process is mordant acid dye which needs involvement of mordant as natural dyes do. These dyes have ions that allow them to form bond with neighboring groups. The dye bath is acidic which leads them to be called mordant acid dyes.

45. References: Basic principle of textile coloration, natural and mordant dyes Natural dyes /NPTEL Textile Engineering Mordant dyes/textile learner Natural and mordant dyes /textile school Literatures of the same title for another campus students(BDU- ioTex )

46. Peer-I members R.NO Name ID 1 Melkamu Kenito TECH/0750/09 2 Meron Tebikew TECH/ 0132/09 3 Azeb Mekonin TECH/1359//09 4 Abdulkerim Nesru TECH/ 1698 /09 5 Selamawit Asalfew TECH/0987 /09 By:

47. This is all we have! THANK YOU!