Dyeing

Water ,Hardness,Surfectents , Detergent

Total Textile Process at a Glance

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

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Water and Water Treatment

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

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.

Properties of textile supply water Minimum Standard Acceptable limits

Color Colorless

Smell Odorless

pH value Neutral (pH 7- 8)

Water hardness < 25 ppm of Ca CO3

Acidity/Alkalinity < 100 mg/l as Ca CO3

Dissolved solids < 150 mg/l

Filterable solids < 50 mg/l

Suspended solids < 1 mg/l

Turbidity < 5 mg/l

Dissolved oxygen Not permit

Carbon dioxide < 50 mg/l

Iron (Fe) < 0.1 mg/l

Copper (Cu) <0.005 mg/l

Manganese (Mn) < 0.02 mg/l

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

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.

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

Hardness Scales

German degree French degree American degree British degree

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

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.

Relation of different scales -

1 ppm = 1.0 mg/l = 0.1 pp/100,000 = 0.0583 gpg (U.S.) = 0.07 gpg imp.

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

Classification of water according to hardness

Hardness rating

ppm of CaCO3

(grains/US gallon) of CaCO3

Soft 0 to <75 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

Problems causes by hard water in wet processing and

their correctionConsequences 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

(A) Problems in boiler

Ca(HCO3)2 → CaCO3 + CO2 + H2O Mg(HCO3)2 → MgCO3 + CO2 + H2O MgCO3 + H2O → Mg(OH)2 +CO2

Heat loss for pipe scaling

Scale thickness (mm) % heat loss (approx.)

1.00 10

3 17

5 22

10 30

20 43

Boiler feed water quality:

Parameter Acceptable limitAppearance Clear, without residue

Residual hardness <5 ppm

Oxygen <0.02 mg/l

Temporary CO2 0 mg/l

Permanent CO2 <25 mg/l

Iron <0.05 mg/l

Copper <0.01 mg/l

pH (at 25º C) 8.0 - 9.0

Boiler feed water temp. >90º C

B) Problems in processing

Wastage of soap (reaction with soap)

2 C17H35COONa + CaSO4 → (C17H35COO)2Ca + ↓

Na2SO4

Reaction with dyestuffs- reaction with dyes and lead dye wastage- sometimes it produces a duller shade

How does the water hardness affect the textile processing?

Desizing Deactivate enzymes and makes it insolubilize some size materials like starch and PVA

Scouring Combine with soap, precipitate metal-organic acids. Produce yellowing of off-white shades, reduce cleaning efficiency, and water absorption

Bleaching Decompose bleach baths

Mercerizing Form insoluble metal oxides, reduce absorbency and luster

Dyeing Combine with dyes changing their shades, insoubilize dyes, cause tippy dyeing, reduce dye diffusion and hence results in poor washing and rubbing fastness.

Printing Break emulsions, change thickener efficiency and viscosity, and those problems indicated for dyeing

Finishing Interfere with catalysts, cause resins and other additives to become nonreactive, break emulsions and deactivate soaps

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

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

Therefore,In 1M solution of 1000ml contain 372 gm Na2-EDTAIn 0.01M solution of 1000ml contain 3.72 gm Na2-EDTAIn 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.

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.

Table: Experimental data

Calculation:

Total hardness =

Volume of 0.01M EDTA solution in ml--------------------------------------× 1000 ppm of CaCO3.Volume of sample water in ml

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).

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 HCl1000 ml of 0.05N HCL contain (36.5 x 0.05) or 1.825gm HClSo, 100 ml of 0.05N HCl contain 0.1825 gm HCl

Let, the concentration of diluted HCl is 35%, then35 gm HCl present in 100 ml of diluted HCl & 0.1825 gm HCl present in {(100 x 0.1825)/35} or0.528 ml diluted HCl

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.

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’

Calculation:

Temporary hardness = 50(b-a) × 0.05 × 1000--------------- ppm (in terms of CaCO3)100

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-EDTAIn 0.01M solution of 1000ml contain 3.72 gm Na2-EDTAIn 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.

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.

Table: Experimental data

Calculation:Total hardness =

Volume of 0.01M EDTA solution in ml---------------------- × 1000 ppm of CaCO3.Volume of sample water in ml

Methods for water softening

Lime-soda process Base exchange process Demineralisation process Sequestering agent

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 H2OMg(HCO3)2 + Ca(OH)2 → MgCO3 + CaCO3 + 2 H2OMgCO3 + Ca(OH)2 → Mg(OH)2 + CaCO3- For permanent hardness – CaSO4 + Na2CO3 → CaCO3 + Na2SO4MgCl2 + Ca(OH)2 → CaCl2 + Mg(OH)2CaCl2 form is removed by – CaCl2 + Na2CO3 → 2 NaCl + CaCO3

Permutit process (Base/ Ion exchange method)

Permutit’ means exchange; in thisprocess, 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 ionexchanger may produce artificially.

Basic Principle

For temporary hardness –2Na-Permutit + Ca(HCO3)2 → Ca-Permutit + ↓2NaHCO3

For permanent hardness –2Na-Permutit + CaSO4 → Ca-Permutit + ↓Na2SO42Na-Permutit + MgSO4 → Mg-Permutit + ↓Na2SO42Na-Permutit + MgCl2 → Mg-Permutit + ↓2NaCl

Regeneration of ZeolitesFor regeneration of sodium salt of the zeolite involves passing a concentrated solution(generally 10%) of NaCl through theexhausted zeolites.

Ca-Permutit + 2NaCl → 2Na-Permutit + CaCl2

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.

A) Cation exchange: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 + 2H2CO3H2CO3 → CO2 + H2O

For temporary hardness – H2R + CaCl2 → CaR + 2HClH2R + CaSO4 → CaR + H2SO4

General reaction – 2(Polymer – SO3¯H+) (s) + Ca²+ (aq) (Polymer – ↔SO3¯)2Ca²+ (s) + 2H+ (aq)

B) Anion exchange: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↔

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

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.

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.

Application of Surfactants Detergents Fabric softener Emulsifiers and

Emulsions Paints Adhesives Inks Anti-fogging Dispersants Wetting Ski wax, snowboard

wax

Defoamers Agrochemical

formulations Herbicides some Insecticides

Biocides Shampoo Hair conditioners (after

shampoo) Spermicide Firefighting Foaming agents

Detergent

A detergent (as a noun; "detersive" means "cleaning" or "having cleaning properties"; adjective "detergency" indicates presence or degree of cleaning property) is a material intended to assist cleaning.

Today, detergent surfactants are made from a variety of petrochemicals (derived from petroleum) and/or oleochemicals (derived from fats and oils).

Although the cleansing action of soaps and detergents is similar, the detergents do not react as readily with hard water ions of calcium and magnesium. Detergent molecular structures consist of a long hydrocarbon chain and a water soluble ionic group.

Classification of detergents

1. Ionic detergent- Anionic detergent - Cationic detergent- Amphoteric detergent2. Nonionic detergent

Anionic detergents:

The detergents whichconsist negative ionic group are called anionic detergents. The majority are alky sulfates and others are generally known as alkyl benzene sulfonates.

Cationic detergents

The cationic classes of detergents have a positive ionic charge and are called "cationic" detergents. In addition to being good cleansing agents, they also possess germicidal properties which makes them useful in hospitals. Most of these detergents are derivatives of ammonia. A cationic detergent is most likely to be found in a shampoo or clothes "rinse".

Nonionic detergents Nonionic surfactant

molecules are produced by first converting the hydrocarbon to an alcohol and then reacting the fatty alcohol with ethylene oxide. They are not ionize in water. They are very popular in textile uses.

Advantages and disadvantages of synthetic detergents

Effective cleaning in hard water They are not precipitate as insoluble

Ca/Mg salts (gummy substance) on material

They are not very good detergent as soap

Incompatibility, in case of opposite ionic nature

Environmental hazard