Dyeing

1. Water ,Hardness,Surfectents , Detergent

2. Total Textile Process at a Glance

3. The course comprised – 1. Applied chemistry: Water & water treatment, surfactants 2. Dyeing: Dyeing theory & mechanism, Mordant dyes, Pigments, Mineral colors 3. Printing: Special types of thickener, Screen printing technology 4. Finishing: Softener, Special types of finishing

4. Don’t be a serious student Be a smart & innovative student

5. Water and Water Treatment Water can be classified as - 1. Rain water. 2. Surface water stock in ocean, rivers or lakes. 3. Subsoil water, which has percolated a small distance into the ground. 4. Deep well waters which have usually percolated through several layer.

6. General characteristics of water Water shows maximum density at 4ºC, 1 gm/cc. its specific gravity is also 1. Freezing temperature 0ºC and boiling temperature is 100ºC.

7. Properties of textile supply water Minimum Standard Color Smell pH value Water hardness Acidity/Alkalinity Dissolved solids Filterable solids Suspended solids Turbidity Dissolved oxygen Carbon dioxide Iron (Fe) Copper (Cu) Manganese (Mn) Acceptable limits Colorless Odorless Neutral (pH 7- 8) < 25 ppm of Ca CO3 < 100 mg/l as Ca CO3 < 150 mg/l < 50 mg/l < 1 mg/l < 5 mg/l Not permit < 50 mg/l < 0.1 mg/l <0.005 mg/l < 0.02 mg/l

8. Lead or heavy metals < 0.01 mg/l Alluminium (Al) < 0.25 mg/l Silica < 3.0 mg/l Sulphate < 250 mg/l Sulphide < 1 mg/l Chloride < 250 mg/l Chlorine < 0.1 mg/l Nitrite (NO2 ) < 5 mg/l Nitrate (NO3 ) < 50 mg/l Ammonia < 0.5 mg/l Oil, grease, fat, soap < 1 mg/l Total solids < 500 mg/l

9. Water Hardness Generally soaps create foam in water, but in present of some materials the foam creation is reduced and need more soap for producing foam, and this condition of water is called water hardness.

10. Reasons of water hardness 1. Temporary hardness: Ca(HCO3)2, Mg(HCO3)2, Fe(HCO3)2 2. Permanent hardness: CaCl2, CaSO4, Ca(NO3)2, MgCl2, MgSO4, Mg(NO3)2

12. Hardness Scales  German degree  French degree  American degree  British degree

13. Definition of Different Hardness 1. 1º H (German) Hardness: 10 mg CaO in 1 litre of water 2. 1º H (French) Hardness: 10 mg CaCO3 in 1 litre of water 3. 1º H (English) Hardness: 10 mg CaCO3 in 0.7 litre of water 4. 1º H (American) Hardness: 1 mg CaCO3 in 1 litre of water

14. Other scales for expressing water hardness -  Parts per million (ppm): The number of parts of substances per million parts of water is known ppm. It is also called American hardness. It can be expressed by another way like mg/l or gm/m3. Grains per U.S. gallon (gpg): The number of grains of substances per 1 U.S. gallon of water (1 U.S. gallon of water weighs 8.33 pound) is known gpg. Parts per hundred thousand (pp/100,000): The number of parts of substances per 100,000 parts of water is known pp/100,000. Grains per imperial gallon (gpg imp): The number of grains of substances per 1 British imperial gallon of water (1 imperial gallon of water weighs 10.0 pound) is known gpg imp.   

15. Relation of different scales - 1 ppm = 1.0 mg/l = 0.1 pp/100,000 = 0.0583 gpg (U.S.) = 0.07 gpg imp.

16. Conversion factor of different water hardness scale Scale Hardness USA D GB F 1º USA 1.0 0.056 0.07 0.1 1º D 17.9 1.0 1.25 1.79 1º GB 14.3 0.8 1.0 1.43 1º F 10.0 0.56 0.7 1.0

17. Classification of water according to hardness Hardness rating Soft ppm of CaCO3 0 to <75 (grains/US gallon) of CaCO3 0 to <5.2 Medium 75 to < 150 5.2 to <10.5 Hard 150 to < 300 10.5 to <21 Very hard 300 and above 21 and greater

18. Problems causes by hard water in wet processing and their correction Consequences of using hard water –  Precipitation of soaps;  Redeposition of dirt and insoluble soaps on the fabric being washed – this can cause yellowing and lead to unlevel dyeing and poor handle;  Precipitation of some dyes as calcium or magnesium salts;  Scale formation on equipments and in boilers and pipelines;  Reduction of the activity of the enzymes used in desizing;  Decrease solubility of sizing agents;  Coagulation of some types of print pastes;  Incompatibility with chemicals in finishing recipes

19. (A) Problems in boiler  Ca(HCO3)2 → CaCO3 + CO2 + H2O  Mg(HCO3)2 → MgCO3 + CO2 + H2O  MgCO3 + H2O → Mg(OH)2 +CO2

20. Heat loss for pipe scaling Scale thickness (mm) % heat loss (approx.) 1.00 10 3 17 5 22 10 30 20 43

21. Boiler feed water quality: Parameter Appearance Residual hardness Oxygen Temporary CO2 Permanent CO2 Iron Copper pH (at 25º C) Boiler feed water temp. Acceptable limit Clear, without residue <5 ppm <0.02 mg/l 0 mg/l <25 mg/l <0.05 mg/l <0.01 mg/l 8.0 - 9.0 >90º C

22. B) Problems in processing  Wastage of soap(reaction with soap) 2 C17H35COONa + CaSO4 → Na2SO4 ↓ → (C17H35COO)2Ca +  Reaction with dyestuffs - reaction with dyes and lead dye wastage - sometimes it produces a duller shade

23. How does the water hardness affect the textile processing? Desizing Deactivate enzymes and makes it insolubilize some size materials like starch and PVA Combine with soap, precipitate metal- organic acids. Produce yellowing of off- white shades, reduce cleaning efficiency, and water absorption Decompose bleach baths Scouring Bleaching Mercerizing Form insoluble metal oxides, reduce absorbency and luster

24. Dyeing Combine with dyes changing their shades, insoubilize dyes, cause tippy dyeing, reduce dye diffusion and hence results in poor washing and rubbing fastness. Break emulsions, change thickener efficiency and viscosity, and those problems indicated for dyeing Printing Finishing Interfere with catalysts, cause resins and other additives to become nonreactive, break emulsions and deactivate soaps

25. Estimation of water hardness  Using direct reading digital meter or strip  In laboratory it is usually determined by titration with a standardized solution (e.g. Na-EDTA) –for mechanism see my book

26. Estimation of total (permanent & temporary) hardness of supply water(by di-sodium salt of EDTA)  Basic principle: - Titration of sample water against standards (0.01M) EDTA solution  Preparation of 0.01M or 0.02N EDTA solution: Molecular weight of disodium salt of EDTA (CH2COOH)2 N2(CH2)2(CH2COONa)2.2H2O = (12+1*2+12+16*2+1)×2 + 14*2+(12+2)*2+ (12+1*2+12+16*2+23)×2 + 2*18 = 118+ 28+28+162+36 = 372

27. Therefore, In 1M solution of 1000ml contain 372 gm Na2-EDTA In 0.01M solution of 1000ml contain 3.72 gm Na2-EDTA In 0.01M solution of 100ml contain 0.372 gm Na2-EDTA  Preparation of ammonia buffer solution: - 145ml of liquor ammonia (NH4OH) of specific gravity 0.88+15gm NH4Cl + distilled water to make 250ml solution to give a pH of 10.

28.  Procedure: - Add 1ml of buffer solution (NH4OH+NH4Cl) to 100ml of the original water sample. Add 3-4 drops of Eriochrome Black T indicator (0.2g dye in 15ml of triethanol amine + 5ml of ethanol)/ 1tablet (making powder) total hardness indicator. - Titrate against 0.01M prepared EDTA solutions in burette until the color charges from wine red (or violet) to pure blue (or turquoise) with no reddish tone; then calculate the total hardness in terms of ppm of CaCO3.

29. Table: Experimental data

30. Calculation: Total hardness = Volume of 0.01M EDTA solution in ml --------------------------------------× 1000 ppm of CaCO3. Volume of sample water in ml

31. Determination of temporary hardness of supply water  Basic principle: - This can be estimated by titration of sample water against standard solution of hydrochloric acid ( 0.05N HCl).

32.  Preparation of 0.05N HCl: Molecular weight of HCL = 1 + 35.5 = 36.5 & Equivalent weight of HCl = 36.5 Therefore, 1000 ml of 1N HCl contain 36.5 gm HCl 1000 ml of 0.05N HCL contain (36.5 x 0.05) or 1.825 gm HCl So, 100 ml of 0.05N HCl contain 0.1825 gm HCl Let, the concentration of diluted HCl is 35%, then 35 gm HCl present in 100 ml of diluted HCl & 0.1825 gm HCl present in {(100 x 0.1825)/35} or 0.528 ml diluted HCl

33.  Procedure: - Add 1cc or 2 – 3 drop [from the solution of (0.1 gm solid methyl orange + 100cc distilled water)] methyl orange indicator to 100ml of fresh distilled water & titrate against 0.05N HCl. Let the titration reading be ‘a’ ml. - Now titrate 100 ml of the sample water against 0.05N HCl using the same indicator (methyl- orange). Let the titration reading ‘b’ ml.

34.  Observation: - Reading should be taken when the color of indicator change orange to red.  Table I: Experimental data for reading ‘a’  Table II: Experimental data for reading ‘b’

35.  Calculation: Temporary hardness = 50(b-a) × 0.05 × 1000 --------------- ppm (in terms of CaCO3) 100

36. Determination of permanent hardness of supply water(by di- sodium salt of EDTA)  Preparation of 0.01M or 0.02N EDTA solution: Molecular weight of disodium salt of EDTA (CH2COOH)2 (N2CH2)2(CH2COONa)2.2H2O = (12+1*2+12+16*2+1)×2 + 14*2+(12+2)*2+ (12+1*2+12+16*2+23)×2 + 2*18 = 118+ 28+28+162+36 = 372 Therefore, In 1M solution of 1000ml contain 372 gm Na2-EDTA In 0.01M solution of 1000ml contain 3.72 gm Na2-EDTA In 0.01M solution of 100ml contain 0.372 gm Na2-EDTA

37.  Preparation of ammonia buffer solution: - 145ml of liquor ammonia (NH4OH) of specific gravity 0.88+15gm NH4Cl + distilled water to make 250ml solution to give a pH of 10.

38.  Procedure: - Take 100ml of sample water in a conical flask; boil it (around 30 minutes) to about 50 ml; cool and filter to remove bicarbonate residual (temporary hardness) and to expel carbon dioxide. Dilute it to by distilled water to make 100 ml. Add 2ml of ammonia buffer solution followed by one tablet of hardness indicator. - Titrate against 0.01M prepared EDTA solutions from burette until the color charges from wine red (or violet) to pure blue (or turquoise) with no reddish tone; then calculate the hardness in terms of ppm of CaCO3.

39.  Table: Experimental data  Calculation: Total hardness = Volume of 0.01M EDTA solution in ml ---------------------- × 1000 ppm of CaCO3. Volume of sample water in ml

40. Methods for water softening  Lime-soda process  Base exchange process  Demineralisation process  Sequestering agent

41. 1. Lime-Soda process  In this process hydrated lime and sodium carbonate is used to remove the hardness. - For temporary hardness – Ca(HCO3)2 + Ca(OH)2 → 2 CaCO3 + 2 H2O Mg(HCO3)2 + Ca(OH)2 → MgCO3 + CaCO3 + 2 H2O MgCO3 + Ca(OH)2 → Mg(OH)2 + CaCO3 - For permanent hardness – CaSO4 + Na2CO3 → CaCO3 + Na2SO4 MgCl2 + Ca(OH)2 → CaCl2 + Mg(OH)2 CaCl2 form is removed by – CaCl2 + Na2CO3 → 2 NaCl + CaCO3

42. Permutit process (Base/ Ion exchange method) Permutit’ means exchange; in this process, hard water is treated with base exchange complex or Zeolites to remove the hardness of water. Zeolites are naturally occurring insoluble mineral of the sodium aluminosilicate type complex (e.g. NaAlSiO4. 3H2O ≈ Na-Permutit). This type of ion exchanger may produce artificially.

43. Basic Principle  For temporary hardness – 2Na-Permutit + Ca(HCO3)2 → Ca-Permutit + 2NaHCO3  For permanent hardness – 2Na-Permutit + CaSO4 → Ca-Permutit + Na2SO4 2Na-Permutit + MgSO4 → Mg-Permutit + Na2SO4 2Na-Permutit + MgCl2 → Mg-Permutit + 2NaCl ↓ ↓ ↓ ↓

44.  Regeneration of Zeolites For regeneration of sodium salt of the zeolite involves passing a concentrated solution (generally 10%) of NaCl through the exhausted zeolites. Ca-Permutit + 2NaCl → 2Na-Permutit + CaCl2

45. Demineralization method The newer synthetic polymer ion exchangers are much more versatile than the zeolites and are widely used for water softening and demineralization. They are often called ion exchange resins. This reagent can remove all mineral salts to complete demineralisation of hard water. It has two types of ion exchanger – Cation exchanger and Anion exchanger.

46.  Cation exchanger has replaceable H+ or Na+ ion. Cation exchange resins are organic in nature (made up by polymerization of polyhydric phenols with formaldehyde. It is also manufactured by sulphonation of coal). These reagents replace the ions of hard water by hydrogen, leaving the water an equivalent amount of acids.  For temporary hardness – H2R + Ca(HCO3)2 → CaR + 2H2CO3 H2CO3 → CO2 + H2O  For temporary hardness – H2R + CaCl2 → CaR + 2HCl H2R + CaSO4 → CaR + H2SO4  General reaction – 2(Polymer – SO3¯H+) (s) + Ca²+ (aq) (Polymer – SO3¯)2Ca²+ (s) + 2H+ (aq) A) Cation exchange: ↔

47.  Anion exchanger has replaceable OH¯ ion. In this unit acid is absorbed by the anionic exchanger which displaces the anionic groups like Cl¯, SO4¯ ¯, from acids.  General reaction – 2(Polymer – NR3+OH¯) (s) + 2Cl¯ (aq) 2(Polymer – NR3+Cl¯) (s) + 2HO¯ (aq)  Water can be totally demineralised by firstly exchanging all cations using s strongly acid form of a cation exchanger. Thus a solution of salts M+X¯ becomes a solution of acid H+X¯, the M+ ions being retained by the resin. Subsequently a strongly basic form of an anion exchanger absorbs the X¯ ions and liberates OH¯ ions into water. These then neutralize the H+ ions from the first step. The reslt is retention of all anions and cations and the neutralization of H+ and OH¯ to form pure demineralization water.  2H+ (aq) + 2OH¯ (aq) 2H2O ↔ B) Anion exchange: ↔

48. Regeneration of reagents: 1.Cation exchanger – (Polymer – SO3¯)2Ca²+ (s) + 2HCl 2(Polymer – SO3¯H+) (s) + Ca2Cl 2. Anionic exchanger – 2(Polymer – NR3+Cl¯) (s) + 2NaOH 2(Polymer – NR3+OH¯) (s) + 2NaCl ↔ ↔

49. Sequestering agents  Addition of a sequestering agent to the water avoids many problems from relatively low concentrations of undesirable metal ions.  Example – EDTA (ethylenediamine tetra-acitic acid), related aminocarboxylic acids, polyphosphates such as sodium tetrametaphosphate Na4P4O12, Calgon - Sodium hexametaphosphate Na6P6O18.

50. Surface Active Agents  The term surfactant is a blend of surface active agent. Surfactants are usually organic compounds that are amphiphilic, meaning they contain both hydrophobic groups (their "tails") and hydrophilic groups (their "heads").  when added to a liquid, reduces its surface tension, thereby increasing its spreading and wetting properties.  In the dyeing of textiles, surface-active agents help the dye penetrate the fabric evenly.