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Scouring

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  • 1. SCOURING
  • 2. SCOURING Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing. Synthetic fibers contain producer spin finishes, coning oils and/or knitting oils. Mill grease used to lubricate processing equipment mill dirt, temporary fabric markings and the like may contaminate fabrics as they are being produced. The process of removing these impurities is called Scouring. Even though these impurities are not soluble in water, they can be removed by Extraction, dissolving the impurities in organic solvents, Emulsification, forming stable suspensions of the impurities in water and Saponification, Converting the contaminates into water soluble components.
  • 3. Scouring: Definition: The tern scouring applies to the removal of impurities such as oil, wax gum, soluble impurities and solid dirt commonly found in textile material. The process consists essentially of treatment with alkali, a good supply of water is essential. Scouring: Types of Scouring Treatments •Scouring By Chemicals Means •Bio scouring or scouring with Enzymes
  • 4. Objects: - The main object of this process is to iron the fabric. 1. To remove natural as well as added impurities of essentially hydrophobic character as completely as possible. 2. To increase absorbency of textile materials. 3. To leave the fabric in a highly hydrophilic condition without undergoing physical or chemical treatment or damage. Object: •Remove all natural impurities such as oil , wax , fat etc from the surface of the fabric . •Produce the fabric more hydrophilic. • Increasing the absorbency and clean the fabric by use alkaline. •To make the suitable situation for next bleaching, dyeing, printing, and finishing process. •Removing the natural coloring matter of the cotton fabric.
  • 5. Theory: Scouring is the process which is removes all the natural impurities like oil wax fat etc, from the surface of the fabric and produce the fabric more hydrophilic, Scouring done by using alkali such as NaoH & Na2Co3. Natural impurities of cellulosic fabric are normally removed by boiling off in a strong alkaline solution. The main object of scouring cotton fabrics is to remove natural as well as added impurities of essentially hydrophobic character as completely as possible and leave the fabric in a highly absorptive condition without undergoing chemical or physical damage significantly. 3C17 – COOH + 3NaOH= 3C17H35COONa +3H2O Or Oil + Caustic =Soap + Glycerine There are three types of scouring: •Saponification •Emulsification •Detergency Method: Saponification method is used for this experiment.
  • 6. Recipe: NaoH –5gm/l Na2CO3 –3gm/l Wetting agent – 2gm/l Sequestering agent – 1 gm/l Time –60min Temperature - 90°c M: l – 1:40 PH - 12-14 Parameter: •Temperature - 90°c •Time –60min •PH – 12-14
  • 7. SCOURING BLEACHING CURVE
  • 8. Chemical Use Caustic (NaOH) Neutralize acidic materials, saponify glycerides (Waxes and Oils), and solubilize silicate. Sodium Silicate Penetrate and break down lignins in motes. Surfactant Reduces surface tension and minimize interfacial tensions. Detergent Emulsify oils, fats, and waxes; remove oil – borne stains; suspend materials after they have been removed. Chelating (Sequestering) agent Deactivate metal ions. Builder (Salt) Cause detergents to become increasingly effective. Solvent Assist emulsification by dissolving oily materials. Chemical Used and Purpose:
  • 9. Scouring process depends on: - 1. The type of cotton. 2. The color of cotton. 3. The cleanliness of cotton. 4. The twist and count of the yarn. 5. The construction of the fabric. Scouring process depends on: -
  • 10.  Yarns and fabrics may be dirty, contain natural waxes or oils, or have been treated with size or lubricants used in spinning, weaving or knitting.  These can all interfere with dyeing, often leading to non-level results. Scouring is a large topic, and the process used depends on the fibre type and its condition.  “True” scouring of greige cellulosic fabrics is typically done, after desizing, at the boil or at higher temperature in pressure vessels, with as much as 10 grams sodium hydroxide per litre of water, plus surfactants, and the process may last for several hours.  Commercial scouring of wool may use solvents, similar to dry cleaning, as part of the process. White fabrics sold at retail have normally be scoured at the mill; “natural” fabrics usually have not (some “natural” fabrics have been scoured but not bleached). SCOURING
  • 11. SCOURING  Art dyeing literature often refers to what amounts to laundering as scouring. This is inadequate for greige fabrics, but often quite acceptable for “white goods”.  A long machine wash with the hottest water possible, about a gram of soda ash per litre of water (about a teaspoon per gallon) and some (preferably optical brightener free) detergent, followed by two rinses is usually acceptable.  Sodium hexametaphosphate may be helpful if the water is hard. Woven white cottons often contain starch that will not be removed by such a limited process.
  • 12. Theory of Scouring: Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing. Synthetic fibers contain producer spin finishes, coning oils and/or knitting oils. Mill grease used t o lubricate processing equipment mill dirt, temporary fabric markings and the like may contaminate fabrics as they are being produced. The process of removing these impurities is called Scouring. Even though these impurities are not soluble in water, they can be removed by Extraction, dissolving the impurities in organic solvents, Emulsification, forming stable suspensions of the impurities in water and Saponification, Converting the contaminates into water Theory of Scouring
  • 13. SN SCOURING AGENT CHEMICALS 1 Alkaline agents NaOH, KOH, Na2CO3, Liquid NH3 sod. metasilicate, sod. silicate, sod. phosphate, trisodium phosphate, tetrasodium phosphate, sodium tripolyphosphate and borax 2 Surfactants Anionic activator, non-ionic activator 3 Organic solvent Chlorine system: Carbonate trichloride, trichloroethylene, perchloro ethylene, methyl chloroform, trichloro methane, fluorine Hydrocarbon system: Benzene, industrial gasoline, white spirit, solvent naphtha SCOURING AGENT
  • 14. Impurities Mechanism of impurity removal Fats and waxes  Saponification: The saponifiable parts of waxes (fatty acid, glycerides, and esters) are converted in to soap.  Emulsification: The non-saponifiable parts of the waxes such as alcohols and hydrocarbons are emulsified by the soap formed.  High temperature: melts some of the waxy materials and converts some of it to a water soluble form.  In extreme cases the use of solvent is necessary. Pectin and related substances  Solubilisation: by the action of alkali, which also acts as a swelling agent to facilitate removal  Pectins are converted to water soluble salts of pectic or meta- pectic acid Proteins and amino acids  Hydrolysis: Proteins are hydrolysed with the formation of soluble sodium salts of amino acid. Hemicelluloses  Dissolution: Hemicelluloses with low DP are dissolved in NaOH. Inorganic substances, minerals and heavy metals  Partially dissolve in NaOH  By use of sequestering or chelating agents.  By producing more soluble salt e.g acid demineralisation IMPURITIES OF SUBSTRATE
  • 15. A typical adopted approach in past towards Enzymatic Scouring process of cotton fabrics
  • 16. An illustration of various steps identified to achieve fast and efficient Enzymatic Cotton Scouring process.
  • 17. Procedure of Scouring Process: Procedure of Scouring Process: The main processes occurring during scouring are: 1. Saponification of fats into water-soluble soap and water-miscible glycerin under alkaline conditions, 2. Hydrolysis of proteins into water-soluble degradation products, 3. Dissolution of hydrolysis to ammonia of simpler amino compounds, 4. Conversion of pectose and pectin into their soluble salts, 5. Dissolution of mineral matter, 6. Emulsification of unsaponifiable oils and waxes, and 7. Removal of dirt particles from the kier liquor by the detergent present therein
  • 18. Alkaline Enzyme Scouring of Cotton Textiles The invention relates to a process for treatment of cellulosic material, as for example, knitted or woven cotton fabric, comprising the steps of preparing an aqueous enzyme solution comprising pectinase, treating the cellulosic material with an effective amount of the aqueous enzyme solution under alkaline scouring conditions; e.g., pH of 9 or above and a temperature of 50° C. or above, in a low calcium or calcium-free environment, yielding a modification of the cellulosic material such that exhibits an enhanced respond to a subsequent chemical treatment. Traditionally, cotton scouring has required the use of harsh alkaline chemicals (caustic), extreme temperatures and large volumes of water. Expenses include not only the cost of the caustic and energy, but also the cost of treating waste water to remove residual caustic and by-products. Today, textile producers have a new, effective alternative to chemical scouring with the advent of the Cottonase™ enzyme. This novel enzyme not only cleans better than chemical scouring, but also greatly reduces the need for extensive waste water treatment and energy consumption. The Cottonase™ enzyme is a versatile, economically viable and environmentally friendly alternative to chemical scouring in cotton preparation. Alkaline Enzyme Scouring of Cotton Textiles
  • 19. 1. Simply wash your fabric, this includes PFD fabric, in the washing machine in hot water with Soda Ash. Do not add any fabric softeners to the wash. If you must dry your fabric do so without any fabric softener sheets 2. Using an large enamel or stainless steel pot, fill the pot at least half full and place one ounce of soda ash into the pot per pound of cotton or linen fabric/fiber. 3. Place fabric into water, swish it around using a stainless steel spoon. 4. Bring water to a boil!!! 5. Adjust heat to a low boil/hard simmer and allow to boil for two hours. stir the fabric every 15 minutes or so t make sure that the fabric is being adequately scoured 6. After two hours remove from heat source, allow fabric to cool down until the fabric is at room temperature. 7. Remove the fabric from the water and rinse. How to Scouring Textile Fabric:
  • 20. Scouring Treatments of Cotton, Silk, Wool and Synthetics Materials Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing. Synthetic fibers contain producer spin finishes, coning oils and/or knitting oils, Mill grease used to lubricate processing equipment, mill dirt, temporary fabric markings and the like may contaminate fabrics as they are being produced. The process of removing these impurities is called Scouring. Even though these impurities are not soluble in water, they can be removed by Extraction, dissolving the impurities in organic solvents, Emulsification, forming stable suspensions of the impurities in water and Saponification, Converting the contaminates into water soluble components. Scouring is usually carried out by means of continuous or discontinuous systems, with the same machines used for downstream treatments; temperature, processing time, pH, concentration of reagents, depend on the fibre,whiteness required and on the machine used.Incomplete scouring processes usually originate dyeing and printing defects due to different degrees of wettability and to inconsistent affinity for dyes of the material. Scouring Treatments of Cotton, Silk, Wool and Synthetics Materials
  • 21. Scouring of Cotton In the scouring process the cotton cellulose material is treated with a solution containing alkali ( soda ash and caustic soda), an anionic and/or nonionic detergent, a wetting agent, a complexing and sequestering for the removal of metal ions and polyacrylates or polyphosphonates as special surfactant free dispersing agents, at high temperature. The scouring operation was conventionally done in kier machines and hence the process was called kier boiling , but now a days the scouring is done mostly in the dyeing machines itself as a part of combined or single operation such as scouring and bleaching. Saponification of fats into water soluble soap and water miscible glycerin under alkaline conditions. Hydrolysis of proteins into water soluble degradation products.  Dissolution of amino compounds. Solubilising of pectose and pectins by converting into soluble salts . Dissolution and extraction of mineral matter.  Emulsification and solubilisation of natural oils and waxes. Removal and dispersion of dirt particles and kitty by the action of alkali and detergent. The material after scouring is more absorbent , free from natural impurities and coloring matter.This treatment can be carried out on filaments, yarns and fabrics. Scouring of Cotton
  • 22. Scouring of Silk The scouring of pure silk is a degumming process used to remove sericin (silk gum) from fibroin floss. Sericin is the gummy element which keeps together the fibroin floss and gives the silk a hard hand and dull appearance. It is carried out on yarn, on dyed yarn, piece-dyed fabric or on products ready for printing. The treatment, which causes a loss of weight ranging between 24 and 28%, gives the degummed silk a lustrous appearance and a soft hand; the treatment is carried out with soapy solutions or with buffer dissolving agents. It is also possible to use enzymes (protease), which hydrolyses sericin.
  • 23. Scouring of Wool On wool, the scouring process removes oils and contaminants accumulated during upstream processing steps and can be carried out on slivers, yarns and fabrics with solutions containing sodium carbonate with soap or ammonia, or anionic and non-ionic surfactants, which carry out a softer washing to avoid any damage to the fibres. Scouring of Synthetics The scouring process applied to synthetic fibres removes oils, lubricants and anti-static substances, dust, contaminants and can be carried out on yarns and fabrics (when warp yarns have been bonded, the treatment is called debonding). It is carried out by means of surfactants, detergents and emulsifying agents.
  • 24. Scouring of Polyester/Cotton Blends: Polyester and cotton are two different fibers obtained from natural source and made of synthetically consecutively. Because of varying physical (Length, diameter, strength, elasticity, torsional rigidity, frictional properties) and chemical properties (thermal properties, density, resistance to chemical agents) of these two fibers have led to treat this blend within proper conditions.Cotton has very good resistance to alkalis but the action of aqueous alkalis may lead an adverse impact on polyester. It should not be pressure kier boiled in the presence of alkalis, as these conditions favor an accelerated attack on the fiber.
  • 25. Typical Scouring Recipe Polyester/Cotton Blend Goods: Wetting agent………………………………….= 0.5-1.0 g/l Sequesterant …………………………………..= 1.0-2.0 g/l Detergent…………………………………………= 1.0-2.0 g/l Caustic soda 36°Be……………………………= 1.0-3.0 g/l Soda ash……………………………………………= 1.0-4.0 g/l Temperature……………………………………..= 90-100°C Time…………………………………………………..= 30-60 min pH………………………………………………………= 10.5+/-0.5 M:L……………………………………………………..= 1:10 Scouring Procedure: 1. Set the with substrate at room temperature with wetting agent, detergent, sequestering agents, and alkalis. 2. Raise the temperature to 95-100°C @1-3°/min 3. Run the bath for 30-60 min 4. Cool down the bath temperature to 60-70°C and drop 5. Rinse twice with hot (around 60°C) and cool water.
  • 26. Chemical Used and Purpose: NaOH– Main scouring agent Na2Co3 - To maintain PH. Sequestering agent – To remove impurities, deactive matel ion Wetting agent - To reduce the surface tension of the water and increase water absorbency
  • 27. Procedure: •At first we took scouring agent in a conical flux . Scouring agent is given below – NaoH - 0.91 gm/L Na2Co3- 0.54 gm/L Wetting agent – 0.37 gm/L Sequestering agent – 0.18 gm/L • Since we get total water 182.2cc , so we put total water 182.2cc in a conical flux and shake sometimes by a roller . •We transferred this mixer solution into a steel mug and put into beforedesizing fabric. •Then we heated it 60 min at temperature 90 C. • Then we washed the fabric properly and reduced water and than dry it by oven machine. •And then we took the fabric weight.
  • 28. Absorbency test : After scouring Absorbency of the fabric is increased significantly – a sample will take less time to be immersed into water than an unscoured sample . A predetermined sample (1 cm x 1 cm) is put gently on the surface of fresh water. If those the sample (1cm x 1 cm)Drive in to water within 5 second . Therefore this fabric quality is good. Drop test : This test is very popular and easy to execute within a short time . In this method ,a 0.1% direct red solution us used . A drop of the dye solution is taken by a pipette and put softly on to the sample surface . The nature of the absorption is observed carefully . Two thinks is considered The time for absorption the drop The shape of the absorbed area on the sample surface .
  • 29. Estimation of Scouring: 1. Determination of weight loss 2. Absorbency Test • Immersion Test • Drop Test • Spot Test 3. Column Test Estimation of Scouring: AATCC Test Method Number 79 Properly scoured fabric should wet out faster and be more water absorbent. AATCC Test Method No. 79 is used to measure fabric wetting. A drop of water is placed on the fabric and the time it takes for the drop to penetrate the fabric is recorded. The faster the wetting time, the more absorbent the fabric.
  • 30. Estimation of Scouring: Determination of Weight Loss: •Standard weight loss is 4 – 8% •If weight loss is less than 4%, it can be said that scouring was not well •If weight loss is above 8% then it can be said that fabric damage has occurred. Measurement of Weight Loss: 5 gm of dried samples is treated with 200 ml of 1% NaOH for 1 hour at 80ᴼ C after which sample is well rinsed and run out in hot water. It is then treated in 200 ml of 0.5% HCl at 80ᴼ C for 1 hour, after which sample is once again rinsed, boiled for 1/2 hour in distilled water, dried & weighted.
  • 31. Immersion Test:  Sample size is “1 cm x 1 cm”  If the fabric floats on the water, then it may be said that the fabric is unscoured  If the fabric is immersed within 5 seconds then it may be said that the fabric is scoured well. Drop Test:  Solution 0.1% Direct red  If dye drop is absorbed within 1 second, then the scouring is of standard level  If dye drop is absorbed within 0.5 – 0.8 second, then the scouring is of good level. A drop is allowed to fall on the fabric by a pipette from 1 or 2 inch above fabric and time in second is measured until the dye drop is fully absorbed. Estimation of Scouring:
  • 32. Spot Test:  Solution of 0.1% direct red  Pour uniform drop on fabric Size of droplet is observed Column Test/Wicking Test:  Solution of 0.1% direct red  Sample size “5 cm x 18 cm”  Observation time 5 minutes Estimation of Scouring:
  • 33. Observation: 1. The length of fabric is observed in solution. 2. If the absorption rise up as high as 30 mm then it may be said that the fabric has good scouring 3. If the absorption rise up as high as 50 mm then it may be said that the fabric has excellent scouring. Assessment of pretreatment by absorbency test: Verdict Spot Test Wicking Test Wicking rate 5 minutes 10 minutes 1 cm 2 cm 3 cm Good Pretreatment 1 – 5 Second 30 – 50 mm 50 – 90 mm 3 – 5 sec 10 – 30 sec 40 – 70 sec Poor Pretreatment More than 10 seconds Less than 30 mm Less than 50 mm More than 10 sec More than 30 sec More than 100 sec Observation:
  • 34. Solvent Scouring: Solvent scouring is the treatments of fabrics in organic solvent medium to remove impurities such as lubricating oils and spin finishes. Certain organic solvents will readily dissolve oils fats and waxes and these solvents can be used to purify textiles. Removal of impurities by dissolution is called Extraction. Suitable Solvents: It is found that waxes are removed by solvents like chloroform, benzene, carbon tetra chloride etc. But those are not used industries because of their high cost and toxicity. Now a days widely used trichloro ethylene, perchloro ethylene etc. Solvent Properties: Boiling Point: Temperature at which solvent is converted from liquid to a gas. Specific Heat: The amount of energy needed to raise one gram of solvent one degree centigrade (Calories/gram/0C). Latent Heat of Evaporation: The amount of energy needed to vaporize one gram of solvent (Calories/gram). Solvent Scouring:
  • 35. Solvent Scouring Process: There are commercial processes where textiles are cleaned with organic solvents. Fabrics processed this way are said to be "Dry Cleaned". Although not widely used as a fabric preparation step, it is an important way of removing certain difficult to remove impurities, where a small amount of residuals can cause downstream problems. Garment dry-cleaning is more prevalent. For fabrics that do not have to be desized, solvent scouring is an effective way of removing fiber producer finishes, coning and knitting oils. Knitted fabrics made from nylon, polyester, acetate and acrylics, are particularly amenable to this method of preparation. Wool grease is effectively removed by solvent scouring. Solvent Extractions are particularly useful in the laboratory for determining the amount of processing oils added to man-made fibers and the residual amounts of oils and waxes left by aqueous scouring. Properly controlled, fabrics can be produced with very little residual matter. Solvent Scouring Process:
  • 36. Above figure shows a schematic of a continuous, solvent scouring range. The entire range is enclosed so the vapors are contained and not allowed to escape into the atmosphere. Recovery units are installed on the range to insure that. none of the solvent is allowed to vent to the environment. Usually carbon adsorption towers are use for this. Also a solvent distillation unit is needed to reconstitute the pure solvent and separate the removed contaminants. The term solvent scouring is also used to describe processes where amounts of organic solvents are added to aqueous scouring formulations to assist in the removal of oils and waxes. This technique is widely used and a more in-depth discussion will be found else were. Organic solvents have a number of advantages that make them particularly useful for wax removal.
  • 37. How to Scouring Textile Fabric: 1. Simply wash your fabric, this includes PFD fabric, in the washing machine in hot water with Soda Ash. Do not add any fabric softeners to the wash. If you must dry your fabric do so without any fabric softener sheets 2. Using an large enamel or stainless steel pot, fill the pot at least half full and place one ounce of soda ash into the pot per pound of cotton or linen fabric/fiber. 3. Place fabric into water, swish it around using a stainless steel spoon. 4. Bring water to a boil!!! 5. Adjust heat to a low boil/hard simmer and allow to boil for two hours. stir the fabric every 15 minutes or so t make sure that the fabric is being adequately scoured 6. After two hours remove from heat source, allow fabric to cool down until the fabric is at room temperature. 7. Remove the fabric from the water and rinse. Advantages: 1. Water Saving 2. Temperature Saving 3. Time Saving 4. Smoother surface profile 5. Lesser Weight loss 6. Environmental benefits 7. Lower cost of Auxiliaries
  • 38. AQUEOUS SCOURING Aqueous scouring is the preferred way of scouring fabrics because water is non- flammable, non-toxic, plentiful and cheap. When preparing woven goods, the scouring step follows desizing and wet fabric proceed to the scouring range without drying in between. The components in the scouring bath must be selected with the fiber in mind. For example strong alkali can be used for scouring cotton, but wool and rayon are damaged by it. Wool can withstand acids whereas cotton, rayon and nylon cannot. A. Typical Formulation for Scouring Specific Fibers 1. Cotton The characteristic speckled look of cotton greige fabrics is caused by cotton motes that were not removed during the yarn making process. Mote removal is a major objective in scouring cotton. Another objective of scouring is to remove minerals, waxes and pectines and to improve absorbency. There are three components in a cotton scouring bath: caustic, to swell and dissolve the motes and to saponify oils and waxes, surfactant, to lower the bath's surface tension so it can wet-out the fabric faster and to emulsifies oils and waxes and chelating agent, to form water dispersible complexes with heavy metals.
  • 39. a. Batch Scouring Procedure 1. Run fabric in a bath containing : 2. Process fabric at 2120F in beck or jet for one hour. 3. Rinse thoroughly. b. Continuous Scouring Procedure 1. Saturate fabric with: 2. Steam fabric one hour at 212F in J-box or steamer. 3. Rinse thoroughly at 1600F
  • 40. Blends Scouring fabrics with a blend of fibers requires consideration of the sensitivities of each fiber to scouring chemicals and to process conditions. Sensitivities to consider when scouring blends are: Cotton: Resistant to strong alkali. Degraded by acid. Rayon: Sensitive to alkali. May be dissolved by hot alkali. Wool: Degraded by alkali. Acetate: Hydrolyzed by alkali. Polyester: Hydrolyses under extreme conditions of alkali and heat. Blends