Chemicals used in textile wet processing & their function assignment work


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Chemicals Used Textile Wet Processing (Desizing To Finishing) & Their importance.

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Chemicals used in textile wet processing & their function assignment work

  1. 1. Page | 1 Personal Details of Student Family Name Md. Shahiduzzaman Given Name (s) Shuvo ID 111-23-2350 Email Shahid23-2350 Assignment Details Assignment Title Importance of Different Chemicals Used In Textile Wet Processing Course Code TE-403 Course Title Textile Wet Processing-III with Lab Submitted To Asst.Professor Sumon Mazumder Submission Date 16.04.2014 Declaration: 1. This work is substantially my own. 2. The assessment has not been submitted previously for assessment in this or any other unit, or another institution 3. I have retained a duplicate copy of the assignment. Md. Shahiduzzaman Shuvo Daffodil International University Faculty of Science & Information Technology Textile Engineering Department
  2. 2. Page | 2 Introduction: We know that dyes, chemicals (or auxiliaries) are the main factor for producing color in yarn, fabric or garments. Different chemicals are used during textile wet processing. In different stages (Pretreatment, dyeing, printing, finishing) of dyeing processing, various chemicals are used. Every chemical have their own characteristics. [1] used-in-wet-processing-list-of-chemical-auxiliaries/-6.10 Pm- 15, April, 2014 Processing of textile materials involves the use of diverse types of compounds to perform various functions. These compounds are variously known as textile auxiliaries, textile chemicals, textile process chemicals etc. [2] Chemistry of organic textile chemicals by Dr.V.A Shenai
  3. 3. Page | 3 Pre-Treatment Stage Chemicals used in Desizing process & their function: Desizing is the first wet processing in textile finishing technology employed to removing the sizing materials from the warp yarn as well as woven fabric. In desizing impregnation of the fabric with desizing agent allowing to degrade & solubilize the size material & finally to wash out the degraded product. Chemicals used in Desizing process & their function: (1) Enzyme: We know that Enzymatic Desizing is the classical desizing process of degrading starch size on cotton fabrics using enzymes. Amylases are the enzymes that hydrolyze & reduce the molecular weight amylase & amylopectin molecules in starch, rendering it water soluble enough to be washed off the fabric. It also replaces harsh chemicals & biodegradable. Enzyme types: pancreatic, Malt extract, bacterial, bactasol (amylase). (2) Wetting agent: Reduce surface tension. (3) Glauber salt (π‘π‘Ž2 𝑆𝑂4.10𝐻2 𝑂): Neutralizes the electronegativity of fiber. Others:
  4. 4. Page | 4 Mg𝐢𝑙2(π‘ˆπ‘ π‘’π‘‘ 𝑖𝑛 πΈπ‘›π‘§π‘¦π‘šπ‘Žπ‘‘π‘–π‘ 𝐷𝑒𝑠𝑖𝑧𝑖𝑛𝑔), Ammonium or Pottassium or Sodium persulphate (used in Oxidative Desizing process), dilute 𝐻2 𝑆𝑂4 or HCl (used in Acid Steeping). [3] Sheet (Desizing-Wet Processing-1) Prepared By Sumon Mazumder, Asst. Professor, DIU. 𝐻2 𝑂2 (Used as oxidants during oxidative desizing), NaOH (used in Lye Desizing process & dissolves starch). Some desizing agents are: Ecolase LT, Finocon-FBOL. [4] Pdf books about desizing-Abdul Azeem KI (potassium Iodide) is used for the estimation of the absence of size materials in the woven fabric. [5] Sheet (Desizing-Wet Processing-1) Prepared By Sumon Mazumder, Asst. Professor, DIU.
  5. 5. Page | 5 Chemicals used in scouring process & their function: I want to say something about scouring before discussing the topics. Scouring is the process of removing the impurities such as oil, wax, fats, dust & dirt from the textile material to make it hydrophilic. After the Scouring process it becomes possible to get clean material. To facilitate the objectives some major chemicals plays an important role in scouring process: Chemicals Functions Detergents Emulsify oils, fat & waxes remove oil borne-stains, suspend materials after the have been removed. Caustic (NaOH/Alkali) Neutralize acidic matters, saponified glycerides (waxes & oils) & solubilize silicates. Also acts as a swelling agent. Sodium silicates (Na2 𝑆𝑖𝑂3) Penetrate & break down lignin into motes Surfactants/Wetting agent/Surface active agents Reduce surface tension & minimize internal tension Sequestering agents/ Chelating agents Deactivate metal ions, reduce water hardness Builders Cause detergent to become increasingly effect Solvents Remove un-saponifiable oil, wax etc. Soda ash (π‘π‘Ž2 𝐢𝑂3) To maintain pH (8.0-8.5) during scouring process [6] Sheet (Scouring-Wet Processing-1) Prepared By Sumon Mazumder, Asst. Professor, DIU Other chemicals used:
  6. 6. Page | 6 1. Also for absorbency test in scouring direct red or Congo red solution is used (Drop test/Wicking test). 2. After Scouring mtl/fabric is treated with 𝐢𝐻3 𝐢𝑂𝑂𝐻 (𝐴𝑐𝑒𝑑𝑖𝑐 π‘Žπ‘π‘–π‘‘), HCl (Hydrochloric acid) or dilute 𝐻2 𝑆𝑂4 (Sulphuric acid) for removing alkali or neutralization of alkali. [7] -15 April 3. Mild oxidizing agents: Used in Kier Boiler machine in order to prevent the reduction of dye. [8] Chemistry of Organic textile chemicals-Dr. V.A. Shenai-Page-22 Chemicals used in Bleaching process & their function: Bleaching is the destruction of natural coloring matters to produce a white material & must be accomplished with a minimum damage to the cotton being bleached. Bleaching is not cleaning process in the sense of scouring as this process does not remove dusts, dirt’s. In bleaching process some chemicals or bleaching agents are used: 1. Bleaching agents: A bleaching agent is a substance that can whiten or decolorize other substances. The purpose of bleaching agents is to bleach the natural substances in cotton fibers & cellulosic fibers that make the fabric yellowish. Bleaching agents essentially destroy chromophores (thereby removing the color), via the oxidation or reduction of these absorbing groups. Bleaching agents also bleach textile colors. [9] bleaching-agents.html-6.23 Pm-14 April
  7. 7. Page | 7 Suitable bleaching agents: A. Oxidizing bleaching agent: Oxidizing bleaching agent are mostly used for permanent bleaching of natural cellulosic fibers. [10] Textile chemistry-1-Md.Mujibur Rahman (Page-149) I. Calcium hypochlorite, Ca(𝑂𝐢𝑙)2 II. Sodium hypochlorite, NaOCl III. Potassium dichromate, 𝐾2 πΆπ‘Ÿ2 𝑂7 IV. Sodium chlorite, NaCl𝑂2 V. Bleaching powder, Ca(OCl)Cl VI. Potassium permanganate, KMn𝑂4 VII. Ozone, 𝑂3 VIII. Hydrogen peroxide, 𝐻2 𝑂2 – Universal bleaching agent. In peroxide bleaching, Hydrogen Peroxide is used as bleaching agent. It is also used in Anti-chlore treatment. [11] Sheet (Bleaching-Wet Processing-1) Prepared By Sumon Mazumder, Asst. Professor, DIU. Any types of fiber can be bleached with Hydrogen Peroxide. Extensively used for bleaching cotton fiber. [12] Textile Chemistry-1-Md.Mujibur Rahman (Page-149) B. Reducing bleaching agent: I. Zinc Dust, ZnO II. Stannous chloride, Sn𝐢𝑙2 III. Ferrus sulphate, FeS𝑂4 IV. Sulphur dioxide, S𝑂2
  8. 8. Page | 8 V. Sodium hydrosulphite, NaHS𝑂3 Hydrozen suphide, 𝐻2 𝑆 [13] Sheet (Bleaching-Wet Processing-1) Prepared by Sumon Mazumder, Asst. Professor, DIU. 2. Peroxide stabilizer: To control the decomposition of H2O2.Keeps active 𝐻2 𝑂2. Provide buffering action to control the pH and to complex with trace metals which catalyze the degradation of the fibers. Example: Sodium silicate (Most commonly used and most effective H2O2 bleach stabilizers), Tri sodium phosphate, Tetra sodium phosphate, Zelatene. [14]Textile Chemistry-1-Md.Mujibur Rahman (Page-149) 3. Caustic (NaOH): Cleaning agent (EDTA-Ethylene Di-Amine Tetra Acetic Acid is also used as powerful chelating agents in𝐻2 𝑂2 π‘π‘™π‘’π‘Žπ‘β„Žπ‘–π‘›π‘” π‘π‘Ÿπ‘œπ‘π‘’π‘ π‘ ). 4. Soda ash (π‘π‘Ž2 𝐢𝑂3): To maintain proper pH. 5. Sequestering agents/ Chelating agents: Reduce water hardness 6. Wetting agents: Reduce surface tension. To provide wetting and detergency 7. Anticreasing agent: Preventing crease marks Others: Peroxide killers/Peroxide killer enzymes: Removes residual hydrogen peroxide from fabric & prevents poor batch-to-batch shade reproducibility as well as uneven dyeing. Also reduce processing time & water consumption. [15] 14 April-2014
  9. 9. Page | 9 Latest Special Chemicals Used In Pre-treatment Range: I. Cracking agent: Cracking agent generally used for pretreatment for textiles which is specially recommended for washing or desizing of synthetic fibers. It is also used for softening process water in the textile industry, removing encrustations from tanks & equipment’s, preventing soil redisposition in heavily contaminated wash liquors. Now a days Cracking agent is used in the case of Cellulosic fibers & their blends. In Pad Batch Cold Peroxide Bleach, Pad Batch Cold Oxidative Cracking, Viscose-Combo-Batch process. Cracking agent is a multifunctional agent which optimizes the pretreatment washing processes after alkaline pretreatment processes such as mercerizing, alkaline cracking & peroxide bleaching. Benefits of using cracking agent: 1) Enhances the effect of simultaneously applied detergents & dispersants. 2) Prevents precipitation particularly in the sub stoichiometric range & agglomeration. Also retards precipitation of metal hydroxides, carbonates & silicates on goods & machinery in pretreatment & washing baths. 3) Generates no foam, is highly stable to alkali, oxidation & hydrolysis. 4) Removes oily & greasy impurities as well as size & soil particles as well as size & soil particles, even in grossly contaminated wash baths.
  10. 10. Page | 10 5) Enables quick & uniform wetting in dry-on-wet processes (particularly in case of grey fabrics). 6) Advantageous in storekeeping. Simplifying of recipe & handling. Prevents deposits on goods & machinery parts. Keeps soil in suspension in bleaching liquors. 7) Some cracking agent used for their reducing effect characteristics. Removes residual peroxide from the goods & prevents partial destruction of direct & reactive dyes. Some cracking agent carries Multifunctional Product properties for which reduces the risk of error. 8) Can be added at the end of the washing range without danger of corrosion in machines such as Stenters. 9) Ideal for automatic pH controlled dosing. II. Bleach processor: Bleach processor is applied in silicate-free Cold Pad Batch & Pas Steam Peroxide bleaching processes on cellulosic fibers & their blends. Bleach processor particularly suitable for the Pas Steam Mega Bleach process which ensures longer steaming times (up to 30 minutes) without making necessary the use of silicates. At the same time the fiber is protected against chemical attack. Benefits of using Bleach Processor: 1) Controls the decomposition of 𝐻2 𝑂2 to produce bleaching active oxygen & to suppress the harmful catalytic reactions. Best use is made of the bleaching agent which results in high degree of whiteness (high protection of the fiber). 2) Prevents deposits on goods & machine parts. Promotes soil suspension in bleaching systems & improves the rinsing process after bleaching. 3) No danger of Ca-silicate deposits & incrustations.
  11. 11. Page | 11 4) Does not generate foam & has a high stability in strongly alkaline liquors. 5) Ensures well balanced formulation which enables the application in hard or soft water, without further additions. III. Surfactant (INVADINE LUN): Wetting & de-aerating in wet processing textile treatments such as scouring/washing, desizing, alkaline boil-out & bleaching. Benefits of using Surfactant (INVADINE LUN): 1) High stability to chemicals, very good solubility which ensures high versatility, simplifying recipes & reducing storekeeping. 2) Very good rewetting properties of treated material. For which the goods are optimally prepared for subsequent continuous or semi-continuous wet processing. 3) No troublesome foaming. Can be uses in a wide range of machinery, even with high turbulence. 4) Ensures a quick & regular pick-up of the chemical bath to obtain high & reproducible effects. IV. Penetration accelerant: οƒΌ Removing air from all liquors used in textile wet processing. οƒΌ Removing air from fiber assemblies & densely packed or tighty woven materials. οƒΌ Preventing foam formation or destroying existing foam even in machines with vigorous liquor circulation. οƒΌ Particularly recommended for circulating-liquor & jet machine dyeing even in short liquor ratio processes. οƒΌ Jet penetration accelerant is specially used for prevention of foaming or destruction of foam already present even in machines
  12. 12. Page | 12 with vigorous liquor circulation. Specially recommended for Jet short liquors & High Temperature dyeing. οƒΌ No stoppages & no damages to goods (chafe marks, creases). 1) Promotes fiber & surface levelness in dyeing. [16] Special Document’s From Salima Sultana Shimo (Lecturer, D.I.U) Mercerization In order to impart lusture, increased strength, increased absorbency & improved dye uptake to cotton fabrics (or yarns), they are mercerised either in grey state or after bleaching which is carried out by treating with a strong solution of caustic soda (NaOH-about 24%, 45ΒΊ-54ΒΊ Tw) & washing off the caustic soda after 1-3 minute. Penetrating & wetting agents: Generally these agents facilitates the penetration of the caustic soda solution efficiently & quickly so that uniform mercerising effect is produced. They are also called mercerising wetting agent. Sulphuric acid (𝑯 𝟐 𝑺𝑢 πŸ’): Are used for removing extra amount of Caustic Soda from fabric. [17]
  13. 13. Page | 13 Dyeing Stage Chemicals used in dyeing process: Dyeing: Dyeing is a coloration process, by which coloring substance (dyes or pigments) is transferred from dye bath into fiber either by physically or chemically, as a result the textile material is colored by dyeing process. [18] Class note: Wet Processing-3(Sumon Mazumder- Asst. Professor, DIU, and 05-02-2014 Common name of different dye & their application: Name of dyestuff Fiber Solubility Direct Cotton, Viscose Water soluble Reactive Wool, Silk, Nylon Water soluble Disperse Nylon, Polyester, Acrylic, Triacetate, Diacetate Water insoluble Vat Cotton, Viscose, Silk, Wool Water insoluble Basic Jute, Acrylic Water insoluble Acid Wool, Silk, Nylon Water soluble Azoic Water insoluble Natural Natural protein fibers (wool,silk,cotton),leather Sulphur Cotton, Viscose Water insoluble Pigment Cotton, Manmade fiber [19] Basic knowledge of wet processing technology-1 By Anowar Hossain
  14. 14. Page | 14 Direct dyes chemicals: Direct dyes are anionic dyes having substantivity for all types of cellulosic fibers which have strong affinity forwards the fiber & don’t need any assistance. Easily soluble in water, Moderate light & wash fatness. Most of the direct dye is Sodium salt of sulphonic acid or Sodium salt of carboxylic acid. Some commercial name of Direct dyes: Chloruntine fast (Ciba), Sirius, Sirius light (Bayer), Pont amine (DuPont) [20] Basic knowledge of wet processing technology-1 By Anowar Hossain. Chemicals uses & their importance: Major chemicals: (1) Soda ash (π‘π‘Ž2 𝐢𝑂3): Removes hardness of water, increase effectiveness of salt, enhances lusture of fiber, and prevents acid in dye bath. (2) Wetting agent (NaCl): Reduce surface tension, helps solution to enter into the fiber easily. (3) Salt: Works as electrolyte. Generally used to increase affinity of the fiber. It also neutralizes the electronegativity of fiber. It also increases exhaustion rate also control the levelling power (Class-B-Salt controllable dye & Class-C dye). Generally π‘π‘Ž2 𝑆𝑂4 is used for medium shade & π‘π‘Ž2 𝑆𝑂4.10𝐻2 𝑂 (Glauber salt) is used for light shade. Other chemicals:
  15. 15. Page | 15 (1) Cu-salt (CuS𝑂4) & Ethanoic acid (𝐢𝐻3 𝐢𝑂𝑂𝐻): They are used as aftertratment chemicals increase light fastness. (2) Formaldehyde (HCHO): Increase wash fastness. (3) Na𝑂2 & HCl mixture: is used as diazotizing & coupling agents in after treatment. (4) Cationic dye fixing agent: Ensures good wet fastness (5) NaOCl solution & Sodium hydrosulphite (Reducing agent- NaHS𝑂3): Helps to stripping. [21] Dyeing technology By Md. Abdul Kader Bapary (Chapter-Direct Dye) Reactive dyes chemicals Reactive dyes are water soluble anionic dyes which are comparatively cheap & fixation of reactive dyes occurs in alkaline condition. These dyes have very good light fastness (with rating 6) & wash fastness (with rating 4-5). Reactive dyes give brighter shades & have moderate rubbing fastness & have good perspiration fastness (with rating 4- 5).Dyeing method is easy, less time 7 temp. Are required. Chemicals uses & their importance: I. Salt (NaCl or π‘π‘Ž2 𝑆𝑂4): Acts like electrolyte which increase exhaustion rate. Electrolyte neutralizes the electro negativity of fiber. Also decreases the hydrolysis of the dye. Electrolyte increase the absorption. II. Alkali (Dye fixing agent): Alkali is used to create optimum pH in the dye bath. It is used as a fixing agent which increases the fixation rate. No dyeing will be take place without it.
  16. 16. Page | 16 Strong alkali (NaHC𝑂3) used for (pH 9-11) lower reactive dye, Medium alkali (π‘π‘Ž2 𝐢𝑂3) used for (pH 11-12) medium reactivity & Weak alkali (NaOH) used for (pH 12-12.5) strong reactive dye. [22] Sheet (Reactive Dye & its application-Wet Processing-3) Prepared by Sumon Mazumder, Asst. Professor, and DIU. III. Sequestering agent: Minimizes water hardness IV. Anticreasing agent: Prevents creasing of fabric V. Levelling agent: To achieve uniform dyeing by controlling the rate of dyeing. [23] Basic knowledge of Wet Processing technology By Md. Anowar Hossain. VI. Defoaming agent/ Anti-foaming agent: Defoamer is a chemical additive that reduces and hinders the formation of foam in process liquids. The terms anti-foam agent and defoamer are often used interchangeably. Commonly used agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already formed. [24] Pm-15 April Other chemicals: Sodium hypochlorite (NaOCl) & Sodium hydrosulphite (π‘π‘Ž2 𝑆2 𝑂4)/ Hydrose: Sodium hydrosulfite is a very effective bleaching agent which is used for full Hydrose stripping of reactive dye with Sodium hypochlorite at room temperature. Glacial acetic acid & Formic acid: Used for partial stripping. [25] Basic knowledge of Wet Processing technology By Md. Anowar Hossain. Vat dyes chemicals
  17. 17. Page | 17 The word vat means vessel. The dye takes their generic names from vatting. Vat dyes are water insoluble which can’t use directly & requires vatting. Washing fastness is very good but rubbing fastness is bad. Various shade is found but dyeing process is difficult & costly. Some commercial name of vat dyes: 1. Indanthrene- Bayer, Hoechst 2. Sandothrene- Sandoz 3. Alizanthrene- ICi 4. Tinon- Geigy Chemicals uses & their importance: Reducing agent (π‘π‘Ž2 𝑆𝑂4): With reducing agent insoluble vat dyes are reduced to produce acidic leucoform. NaOH is used as a solubilizing agent. This process is called vatting. [26] Basic knowledge of Wet Processing technology By Md. Anowar Hossain. i. Wetting agent: Reduce surface tension of water during the vatting stage. ii. Exhausting agent: Exhausting agent like Glauber Salt/ Common salt (NaCl-added in dye bath) is needed during dyeing with 𝐼 π‘˜, 𝐼 𝑀 class dyes. iii. Retarding agent/ levelling agent: Retarding agent like Lignin Sulphonate is needed during dyeing with 𝐼 𝑁 dyes. When degree of unevenness is low then ordinary retarding agent is used. [27] Chemistry of Organic textile chemicals By Dr. V.A. Shenai Other chemicals: NaOH & Sodium hydrosulphite (π‘π‘Ž2 𝑆2 𝑂4)/ Hydrose: This chemicals are used for even dyeing presence of certain levelling agent.
  18. 18. Page | 18 NaN𝑂2 & 𝐻2 𝑆𝑂4: Uses in dye development bath. [28] Basic knowledge of Wet Processing technology By Md. Anowar Hossain. Polyvinyl pyrolidone: Most efficient vat dye stripping agents when used along caustic soda & sodium hydrosulphite. [29] Chemistry of Organic textile chemicals By Dr. V.A. Shenai. Disperse dyes chemicals Disperse dyes are nonionic water insoluble dyes suitable for dyeing hydrophobic fibers. Generally man made cellulose esters & synthetic fibers specially acetate & polyester fibers & sometimes nylon & acrylic fibers. Wash fastness of these dyes is moderate to good & have fair to good light fastness. [30] Sheet (Disperse Dye-Wet Processing-3) Prepared by Sumon Mazumder, Asst. Professor, and DIU. Some commercial name of disperse dyes: 1. Terasil-Cibageigy-Switzerland 2. Foron-Sandoz-Switzerland 3. Pelanil-BASF-Germany 4. Resolin-Bayer-Germany Samaron-Hoechst-Germany [31] Sheet (Disperse Dye-Wet Processing-3) Prepared by Sumon Mazumder, Asst. Professor, and DIU. Chemicals uses & their importance: i. Dispersing agent: To ensure uniform & trouble free dyeing the dye should be present in dye bath in a uniform & very fine form (because Disperse dyes are water insoluble & form aqueous dispersion in water) & should give a stable dispersion. For this
  19. 19. Page | 19 special chemical is used in dye bath named dispersing agent. It enables the dye to stable in hard water, high temp. Effective under dyeing conditions. Example: Alkali sulphates, alkyl aryl sulphonates etc. ii. Carriers/ Swelling agent: For this more dye can be transferred easily from the dye bath to fiber (polymer system). It increases the dyeing rate. It swells the polyester fiber & most suitable for obtaining dark shades. Hydrocarbons, phenols, amino acids, amides, alcohols, esters, ketones are some example of carriers. [32] Sheet (Disperse Dye-Wet Processing-3) Prepared by Sumon M zumder, Asst. Professor, and DIU. Other chemicals: Migration inhibitors: Are used in padding liquors to prevent two-sided effect (defect) in fabric. Levelling agent: Used to produce level dyeing. Emulsified carriers: Used to eliminate the toxic effects of the residual carrier. [33] Chemistry of Organic textile chemicals By Dr. V.A. Shenai Sulphur dyes chemicals Sulphur dyes are highly colored water insoluble dyes which contain Sulphur linkage within their molecules. No direct affinity towards cellulosic fibers. This dyes have good & excellent light & wash fastness respectively. Some trade name of disperse dyes: 1. Calcogene- American cynanid- USA 2. Thional-ICI-UK 3. Sulphosol-James Robinsone-UK
  20. 20. Page | 20 Major chemicals: i. Reducing agent (π‘π‘Ž2 𝑆/ π‘π‘Žπ»π‘†/ Thioglycolic acid): Water insoluble Sulphur dye can be make water soluble by treating with reducing agent. These also makes them substantive towards cellulosic fibers. Reducing agent breaks the Sulphur linkage & helps the material (fiber/surface) surface to penetrate easily. ii. Soda ash (π‘π‘Ž2 𝐢𝑂3): Maintaining optimum pH in dye bath. It also helps to remove Sulphur black tendering faults after dyeing. iii. Salt: Uses as electrolyte. Increases exhaustion rate. iv. T.R oil: Used in dye paste with π‘π‘Ž2 𝐢𝑂3. Later it is used with reducing agent dye paste. Others: Oxidizing agents: Are used to convert the reduced water soluble form of the dyes to the original water insoluble form by oxidation. Plays an important role to develop the correct shades & getting brighter shades. 𝐾2 πΆπ‘Ÿ2 𝑂7, Na-Perborate, Na-per carbonate & Na-peroxide are some examples of oxidizing agents. π‘π‘Ž2 𝑆: Dilute solution or strong solution of π‘π‘Ž2 𝑆(0.1%) helps to prevent the bronziness or dullness of shades. Boiling soap solution & saponified palm oil: Also helps to minimizing the bronziness defect. 𝐾2 πΆπ‘Ÿ2 𝑂7/𝐢𝐻3 𝐢𝑂𝑂𝐻 : Dyed materials are treated with these chemicals to remove Sulphur black tendering defect. 𝐢𝐻3 𝐢𝑂𝑂𝐻 Also converts the harmful 𝐻2 𝑆𝑂4 into harmless acetic acid. Bleaching powder (NaOCl), KMn𝑂4: Stripping agents. CuS𝑂4: Used in aftertratment (dye rubber material case).
  21. 21. Page | 21 [34] Sheet (Sulphur Dye-Wet Processing-3) Prepared by Sumon Mazumder, Asst. Professor, and DIU. Basic dyes chemicals Basic dye is water insoluble but soluble in alcohol & methylated spirit. Brilliant shade can be found. Basic reacts with strong alkali. It also reduced with reducing agent & produce colorless dye base but when deoxidized by acetic acid again colored component easily. Direct affinity to jute fiber & acrylic fiber is also reacts with it. No affinity to cotton fiber (so special treatment called Mordanting is done). Wash fastness is moderate to poor. [35] Basic knowledge of Wet Processing technology By Md. Anowar Hossain. Some trade name of Basic dye: 1. Methylene blue 2. Methyl violet 3. Bismarck brown 4. Magenta [36] Sheet (Basic Dye-Wet Processing-2) Prepared by Salima Sultana Shimo, Lecturer and DIU. Major chemicals: 1. Acetic acid (𝐢𝐻3 𝐢𝑂𝑂𝐻): Works as solubilizing agent for Basic dye (water insoluble). 40% (owf) Acetic acid are taken to form paste. Acetic acid is also used as after treatment agent. If dyed materials are treated with 2%𝐢𝐻3 𝐢𝑂𝑂𝐻, the dye stability increases.
  22. 22. Page | 22 2. Salt: Increase exhaustion rate. Salt is also used to add extra energy to push the dye in the fiber that increase the absorption rate. 3. Tannic acid: Most important chemicals for basic dye. Used as mordanting agent when basic dyes are dyed with cellulosic cotton fiber (since basic dyes have no affinity for cellulosic fiber). Mordant is a special chemical which have affinity both for dye stuff & fiber. So both dye & cellulose fiber are treated with tannic acid to form mordanted cellulose. 4. Tartar emetic acid: Works as fixing agent while dyeing with cellulosic fiber. 5. Alkali: For proper exhaustion sometimes alkali is used in dye bath as dyeing assistant (when used acid). 6. Soap solution: Sometimes soap solution is used in dye bath instead of acetic acid (some cases). 7. Cationic retarding agents are used for producing even dyeing results during the dyeing of acrylic fibers with basic dyes. [37] Chemistry of Organic Textile Chemicals-Dr.V.A. Shenai Others: Tartar emetic acid (𝐢4 𝐻6 𝑂6): It is used in after treatment for stabling dye in solution. Tannic acid(𝐢14 𝐻10 𝑂7): Dyed material is also treated with tannic acid for increasing dye stability but lusture bit decreases. Alcoholic solution: Stripping agent. Alum: It is used in after treatment. Due to improvement of lusture dyed sample is treated with 2% alum. [38] Dyeing Technology by Abdul Kader Bapary
  23. 23. Page | 23 Azoic dyes chemicals Cellulose specially cotton, flax, rayon, jute, hemp, & silk, nylon, polyester, acetate fibers are dyed & printed with azoic dye. Azoic colors have excellent light fastness (with rating 6-7) & also have very good wash fastness (with rating 4-5). Major chemicals: Napthol (Ξ²-napthol): Generally used for naptholation (very important stage) treatment. Alkali (NaOH): Alkali is used to convert napthol to soluble Na- naptholate. Alkali makes napthol substantive to cotton fiber. Sodium nitrite (NaN𝑂2), HCl: Both are used for diazotization process (for making Benzene diazonium chloride). Common salt: Used as an electrolyte to increase substantivity of napthol to fiber. Formaldehydes (HCHO): Na-naptholate shows the tendency to be converted to free napthol by oxidation process. Formaldehyde prevents that tendency. [39] Sheet (Azoic Dye-Wet Processing-3) Prepared by Sumon Mazumder, Asst. Professor, and DIU. Others:
  24. 24. Page | 24 Brine solution (NaCl): Brine solution is used to remove excess napthol. Soap/Detergent: After treatment agent. Soda ash (π‘π‘Ž2 𝐢𝑂3): After treatment agent. T.R.oil, methylated spirit: Used in hot dissolution method & cold dissolution method respectively. T.R.oil used as a stable dispersing agent. Caustic, Na-Hydrosulphite: Stripping agent. [40] Dyeing Technology by Abdul Kader Bapary Acid dyes chemicals Acid dyes have great affinity towards protein fiber & it is water soluble. Chemicals used: Glauber salt: increases affinity. T.R.oil: Used as stable dispersing agent. Prevents the precipitation of the complex dye bath. Retarding agents: They are necessary to produce even dyeing result during dyeing of polyamide fiber materials with acid dyes. 𝐻2 𝑆𝑂4, 𝐢𝐻3 𝐢𝑂𝑂𝐻, (𝑁𝐻4)2 𝑆𝑂4: Used as strong acid dyes on woolen material, weak acid dye on wool & neutral acid dyes on wool respectively. Acid helps the material to absorb dye easily. Acetic acid, Formaldehyde, Hydrosulphite: Used during redyeing of acid dyed mtl. [41] Dyeing Technology by Abdul Kader Bapary
  25. 25. Page | 25 Some special dyeing auxiliaries: 1) Afterclearing agent: Soaping reactive dyeing & prints on cellulosic fibers & their blends. Importance: ο‚· Promotes solubility of hydrolyzed reactive dyes. Improved wet fastness properties. Increased effectiveness of the washing- off process. ο‚· No impairment of light fastness. No effect on the shades of dyeing & prints. Softening effect on soaping baths. Maximum fastness properties are achieved. ο‚· No additional foaming when used in Jets. ο‚· No staining of white grounds on prints. 2) Fixatives: After treating dyeing’s produced with reactive & direct dyes on cellulosic fibers by exhaustion & padding. After treating prints produced with reactive dyes on cellulosic fibers.
  26. 26. Page | 26 ο‚· Prevents dye migration during dyeing. ο‚· Excellent water severe, perspiration & hot pressing fastness to washing. ο‚· No impairment of fastness properties after heat treatments. ο‚· Ensures high exhaustion. ο‚· High affinity, low pH dependence. [42] Special Document’s Provided by Salima Sultana Shimo (Lecturer D.I.U) Printing Stage Printing is a coloration process by which coloring substance (dyes or pigments) are applied on the surface of textile material in localized (selection/mark) area according to particular design with following different styles & methods. [43] Class note: Wet Processing-3(Sumon Mazumder- Asst. Professor, DIU, and 05-02-2014 Essentials ingredients of printing paste: 1) Dye stuff: Most important elements. Without dye stuff printing will not happen 2) Wetting agents: To obtain smooth paste, to dissolve the dyestuff in the paste, to wet the fabric as well as dyestuff wetting agents are used. 3) Solvent, solution aids (hydrotropic substances), dispersing agents & humectants: To make proper printing paste, for preventing precipitation, for getting bright design. For completely dissolving the solubilized dyes (especially on vat dye for getting full color value) solution aids are necessary. 4) Thickeners: Thickeners are used to give required viscosity to the printing paste, to hold the ingredients of the paste on the fabrics, to prevent premature reaction between the chemicals
  27. 27. Page | 27 contained in the print paste, to hold or adhere the dye particles in the desired place on the fabric. Example: Starch, modified starches (oxidized & hydrolyzed), dextrins (British gums), gums (gum Arabic, gum Tragacanth, gum Guar), CMC, HEC, sodium alginate. 5) Defoaming agent & antifoaming agents: Prevents frothing during the continuous agitation of printing paste. Also prevents faults during roller printing (sprayed into the printing paste) due to use of wetting agents in the printing paste. It works like a barrier for creating foam. 6) Oxidizing & reducing agent: Oxidizing agents prevents premature development of color, reduction of color during steaming. Also mild oxidizing agents are used to protect ground dye from partial destruction (producing lighter ground). Reducing agents are used to destroy color from the ground of fabric. 7) Catalyst & oxygen carriers: Prevents oxidization at elevated temperature of steaming & prevents also fiber damage during steaming. Example: Potassium Ferro cyanide, copper suphide, vanadium chloride. Catalyst like diammonium hydrogen phosphate plays an important & vital role in pigment printing. 8) Acids & alkalis: Both are used to maintain proper pH. Acetic condition is needed for fixing the colors & binders strongly at high temperature (pigment printing, solubilized vat dyes). 9) Carriers & swelling agent: When disperse dyes are printed on polyester fiber materials, the use of a swelling agent (carrier) in the printing paste produces better color value of the final prints. 10) Hygroscopic substances (NaCl): Easily absorbs water from surrounding atmosphere.
  28. 28. Page | 28 11) Discharging & resisting agents: Especially used in discharge style of printing. 12) Complexing agents: Certain Complexing agents are incorporated in the discharge printing paste containing the reducing agent & printed on vat dyed fabric. 13) Urea: Controls moisture. 14) Binding & fixing agents: Used in pigment printing. [44] Textile Finishing Chemicals Bleached, dyed & printed fabrics are subjected to certain processes known as finishing processes in order to later their appearance, feel & sale value before sending them to market for sale. Chemicals used in finishing process: i. Anticreasing agents: To prevent creasing of fabric or garments. Anticreasing agents is one types of cross-linking agent. ii. Antipilling agent: It is used to prevent pills formation during wearing of cloth. [45] Basic knowledge of Wet Processing By Md. Anowar Hossain iii. Softening agents: The harsh feel (rough handle) of a fabric can be modified by the application of softening agents. These are of three types- anionic, cationic & nonionic softening agents (fatty alcohol sulphates, fatty acid amide salts & polyethylene glycol monoesters). [46] Chemistry of organic Textile Chemicals by Dr.V.A. Shenai iv. Antistatic agents: Reduce static electricity which may accumulate on fibers. [47]
  29. 29. Page | 29 textile-finishing_1796.html-08 April-9.34 PM v. Stain/Soil resistance & Soil-Release finishing agents: A soil/stain-resistant finish, as the name suggests, improves the ability of the material to resist soiling and staining by preventing the stain from spreading on the surface. Soil-release is β€œa finish for textiles that makes it easier to remove stain and soil in laundering. Soil-release finishes were originally developed to enhance the soil-release properties of hydrophobic and oleophilic fibers such as polyester and cotton/polyester blends with durable press finish. Fluorocarbon finishes that are used as water- and stain- resistant finishes are also effective as soil-release finishes. [48] g_functionalfinishes_maintenance.htm-08 April-9.22 Pm vi. Water-repellent & water proofing finishing agents: Waterproof Finishes -Allows no water to penetrate, but tend to be uncomfortable because they trap moisture next to the body. Recently, fabrics have been developed that are waterproof, yet are also breathable. Water-repellent finishes resist wetting. vii. Flame retarding agents: prevent highly flammable textiles from bursting into flame. viii. Mothproofing finishing: Protect protein-containing fibers, such as wool, from being attacked by moths, carpet beetles and other insects. ix. Enzyme finishing agents: Applied to cellulosic textiles that produces permanent effects by the use of enzymes. Bio-finishing removes protruding fibers and slubs from fabrics, significantly reduces pilling, softens fabric hand and provides a smooth fabric appearance.
  30. 30. Page | 30 x. Absorbent finishing agents: Increase fibers moisture holding power. [49] textile-finishing_1796.html-9.46 Pm-08 April xi. Antimildew agents: Prevents textile material from bacterial infection. xii. Weight giving agents: Increases textile materials weight. [50] Dyeing Technology by Abdul Kader Bapary. xiii. Resin finishing: Resin finishing is the process of bringing out a special property of crease recovery to cotton. Resins are cross linking agents. Advantages: Reduces shrinkage of fabric during laundering, improves crease resistance & recovery property, improves weight & dimensional stability, smooth resilience, handle & draping quality. It also improves light & wash fastness of many dye-stuff. Increase the strength of rayon fiber both in wet & dry condition. [51] finishing-11522628-7.06 Pm-15 April,20 xiv. Special Finishing Chemicals: a) Lubricant (Dyeing Axillaries): In the wet finishing of textiles of any fiber prone to creasing, wrinkling, crow’s feet & chafe marking. This special types of lubricating agent is particularly useful for processing under difficult conditions, such as in short liquors or on heavily loaded winches & jets, & for processing heavy, crease-prone goods & materials. Importance: No formation of permanent creases during wet finishing. Ropes open & displace more easily, so improving levelness. Textiles run better & more dependably in machines, no chafe marks or streaks. No stiffness of viscose in wet process.
  31. 31. Page | 31 Higher utilization of jets, winches, paddle & drum-type dyeing machines. No foam problems in Jet dyeing machines. Excellent fastness properties. No impairment of liquor stability, hence no dye agglomeration & no quality problems with stains & specks. [52] Special documents provided by Salima Sultana Shimo (Lecturer, D.I.U) Conclusion: Wet processing engineering is one of the major streams in textile engineering refers to textile chemical processing engineering and applied science. For successful wet processing operation different dyes, chemicals or chemical auxiliaries (finishing agent, printing agent) plays an important role. Without these chemicals dyeing operation will not be satisfactory (like without alkali no dyeing will be taken place, without salt proper fixation or sometimes better can’t be achieved, without sequestering agent-EDTA, NTA is mostly used dye bath water hardness can’t be removed, without levelling agent level dyeing is impossible, without wetting agent proper wetting of fabric or smooth printing paste impossible, without proper using of finishing chemicals
  32. 32. Page | 32 satisfactory finishing operation will be uncompleted). Like NaOH (strong alkali- also called caustic soda) which is must needed for mercerizing chemical finishing operation, also needed in different dyeing operation (during Reactive dyeing with less reactive dye, for removing residual amount of detergent & wetting agent after the operation, also acts as a swelling agent during scouring operation, during naptholation for making napthol more substantive to cellulosic fiber) are mostly used (sometimes soda ash, sodium bicarbonate are also uses). Importance of salt can be described in words (for proper fixation, neutralizing ion, for improving fastness-metallic salts). Generally Glauber salt (π‘π‘Ž2 𝑆𝑂4.10𝐻2 𝑂 is mostly used sometimes common salt is also used. Levelling agents (which mostly used in dyeing acid dyes on wool or nylon or vat dyes on cotton, also uses for different stages of dyeing process) ensures level dyeing. Without dispersing agents & carriers disperse dye can’t be used for dyeing synthetic hydrophobic fiber or printing polyester with disperse dyes. Without using oxidizing (𝐻2 𝑂2 𝑖𝑠 π‘šπ‘œπ‘ π‘‘π‘™π‘¦ 𝑒𝑠𝑒𝑑 𝑖𝑛 π‘π‘™π‘’π‘Žπ‘β„Žπ‘–π‘›π‘” π‘π‘Ÿπ‘œπ‘π‘’π‘ π‘ , π‘œπ‘₯π‘–π‘‘π‘Žπ‘‘π‘–π‘œπ‘› 𝑠𝑑𝑒𝑝 π‘œπ‘“ π‘†π‘’π‘™π‘β„Žπ‘’π‘Ÿ 𝑑𝑦𝑒) & reducing agent (like reduction of Sulphur dyes-Sodium Sulphide most widely used reducing agent, Hydrose is also used) proper fixation of dyes & proper solubility & proper stripping can’t be done. Water-repelling agents, water-proofing agents, crease resisting, flame retardants, antistatic finishing agents, dye fixing agents, softening agents, stiffening agents, resin finishing agents binders & fixers (in the case of pigment printing) are mostly used finishing chemicals. Thickeners (CMC, HEC mostly used-ensures proper viscosity of printing paste), defoaming agents (prevents foaming), catalyst & oxygen carriers (prevents fiber damage & fixes colors), solvents & solution
  33. 33. Page | 33 aids (prevents dye aggregation) are essential for successful printing operation. So we should use the chemicals according to their scope of use.
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