Once the grey fabric has been received in the grey rooms at the mills that process them, the bales are then opened and scrutinized. It is then checked and verified whether the grey fabric meets the specified standards. It is the weave defects. They are identified. Grey Fabric inspection involves three steps
Perching examines the visuals and is performed using an inspection table, an opaque glass with lighting above and behind it. Grey Fabric imperfections such as dense spots, flaws, knots in yarn, stains, and other marks are identified.
Burling, This is the process of removing yarn knots or other material imperfections.
Repairing is, obviously, the actual fixation of imperfections. Knotting must be done carefully and thoroughly so that the hole or repair is not apparent.
The most recent breakthrough is through laser beams. The imperfections such as stains, holes, hick spots, loose ends, and protruding threads from warp and weft are identified. The device operates on an online system that reduces the chance of human errors.
Sewing After the products have been examined, checked, and classified in the grey Grey fabric area, by the quality standards and stamped, they’re sewn together, from end to end, with sewing machines specially designed to do this. Sewing should be done to keep the Grey fabric’s creases away from stitching.
A proper stitching thread is crucial to avoid stitch marks in color padding. When using heavy Grey fabrics for mercerizing or continuous operations, the seam is recommended to be longer (15 millimeters) and more robust. Sometimes, bonding or gluing cloth to secure the pieces together by melting polymer films with the help of high temperatures is employed in sewn seams to decrease the number of rags. The goods of identical size, weight, thickness, and the same treatment are batched together, and each lot is identified with a number.
The primary goals of the treatment of textiles for preparation are
- Eliminate from the fibers any impurities, natural or synthetic, and those included during production, which could hinder the dyeing or finishing process.
- Enhance the ability of fibers to take in water solutions of chemicals and dyes.
- Give the Grey fabrics the proper brightness or whiteness as per the requirements, particularly when dazzling or certain pastel shades are required.
Grey Fabrics made from cotton Grey Fabrics
Cotton fibers, on average, comprise 90-96 percent cellulose once they are bone dry. The approximate quantities of other substances in the thread include 1.1 1.9% – 1.9 percent proteins, 0.7-1.2% pectin, 0.4-1.0 percentage of waxes, 0.7-1.6 percent ash, and 0.5-1.0 percent other impurities.
Alongside the natural impurities, many fine particles of broken seeds and other fragments from the cotton plant remain attached in the yarns. In converting fibers into strings, additional contaminants accumulate when knitting or weaving. The spinning oils are used for knitting and sizing. These materials are placed on the warp to ensure that they will not break easily when weaving. The Grey fabric woven from the loom could contain up to 20% foreign materials and added natural materials, the majority of which have to be removed in preparing the Grey fabric before dying.
The process of making Grey fabrics composed of polyester or cotton blends of cotton may involve some or all of the following procedures such as desizing, singing, and bleaching. Other processes include Scouring, bleaching, and mercerizing. Specific techniques are frequently blended with ever-growing demands to save on chemicals, energy, and water—one example of combining application oxidative desizing’ in which desizing and Scouring co-occur.
The Grey fabrics are generally sung before eliminating impurities through the wet process. This process causes the protruding, and fuzzy fiber ends to be destroyed by burning the ends off. Singing is performed on Grey fabrics that need an uncluttered and smooth surface like broad batiste and broadcloth, and Grey fabrics printed. It typically occurs in both directions of the material.
- Singing enhances the surface appearance of Grey fabrics. It also reduces the amount of soiling on materials.
- Singing helps reduce fog caused by light reflections caused due to protruding fibers on the Grey fabric’s surface and enhances the appearance of dyed Grey fabrics.
- The squeezing of a material that contains thermoplastic fibers like polyester can reduce its potential to pill.
In a singer, a material is heated and passed through at very high speeds (e.g., 300 yards per min.) to avoid burning, after which the singed Grey fabric has been run through water (or placed directly into the bath for desizing) to eliminate sparks that could cause it to catch fire.
Uneven singeing can result in uneven dyeing. This is why the singer must pass the Grey fabric mutedly, open, and with some tension. The gas burners must be maintained and controlled correctly; otherwise, streaky dyeing could be observed. Additionally, the same amount of dyeing should be applied to the Grey fabric’s face and back to prevent back shading.
Before weaving cotton warp yarns, they’re coated with sizing substances to add strength and resistance to scratching. The most popular sizing materials employed are starches and different types of partially hydrolyzed alcohol.
Different Desizing Types
In this process, dilute choleric hydro acid or sulphuric acid, or an amalgam of both, are utilized to hydrolyze the starch in the Grey fabric. The Grey fabric is soaked in 0.25 percent (10 grams/l) of acid, then passed through a mangle padding and kept for 6 hours. The temperature is raised to 50C.
The starch present in the Grey fabric has been dissolving and can be easily eliminated by washing. Since acid may attack the cellulose fiber, care should be taken to prevent the destruction of cotton.
The Grey fabric needs to be washed using hot water after desizing.
Benefit: Time required is less compared to steeping rot
Negative: There isn’t any way to control the procedure.
In this way, starch is transformed into a form of oxidation. It’s a quick desizing that can be completed in two to four minutes. It is performed at a temperature of 95C. The most commonly employed oxidative desizing agents are potassium persulphate or hydrogen persulfate sodium bromide.
The time needed for desizing is shorter, and the process can be continued. The biggest drawback to this method is its cost and somewhat complicated process. There is a chance of pentachlorophenol levels within the Grey fabric designed that could cause harm.
The most widely utilized and effective method to remove starch from Grey fabrics is enzymes. The benefit of this method is that there is no chance of damaging the Grey fabric. It adds softness and enhances the Grey fabric’s ability to wet.
These are the complex proteins found in animal and vegetable cells. The enzymes are sensitive to their surroundings. They have a self-life span of just a few months and must be stored less than 21C. If utilized at pH or temperatures higher than the ones recommended, they can be destroyed.
The most commonly used enzymes for desizing are
- Pancreatic enzymes (animal source), e.g., Novoformosol,
- Malt enzymes (vegetable origin), e.g., Diastofor,
- Bacterial enzymes (bacterial origin), e.g., Repidase
Most desizing enzymes operate at their optimal temperature between 38 and 68C. However, they are enzymes that function efficiently at boiling temperatures and the higher. Within the range recommended by an enzyme, an appropriate temperature exists at which the enzyme has the most increased activity. The impregnating bath that is typically within the scope of pH 4.5 to 7.5 must be set so that the enzyme performs at a high-efficiency level.
Grey Fabric is impregnated using a de-sizing bath stored for 8-12 hours. Impregnating bath is a mixture of enzyme Wetting agent, Nacl, and Wetting. Grey Fabric is thoroughly cleaned with hot water.
New Development in Enzyme desizing:
Application of enzymes at high temperatures 100-96°C Grey Fabric was padded with the enzyme bath and then passed through Wet steam at 96′ to 100’C. De-sizing was completed in less than one minute. The primary benefit of de-sizing using enzymes is no chance of damaging fibers. However, it can be costly.
This cleansing process, sometimes called alkali boil-off, removes the majority of the impurities in cotton. This includes sizing residues oil, wax, protein, and other foreign materials like dust, sand, and other leafy matter. Scouring effectiveness is mainly dependent on the maturation, fineness, and source of cotton fibers.
Kier boiling is commonly used to perform scouring. A kier is a circular vessel that can hold 1 to five-ton of Grey fabrics. It is equipped with a gauge for pressure and a safety valve. To boil kier, use the mixture of 5-10g/l caustic soda solution and sodium silicate 1 and 1% soap as the wetting agent. Boiling is conducted at 101C temperature for 6-8 hours while under pressure.
The liquid is completely removed and washed with cold water following the boiling process. This is the most effective method to clean cotton Grey fabric as the impurities that are the worst are removed, and PCP’s traces are eliminated. But, it’s a highly time-consuming process that isn’t favored nowadays.
Scouring could be accomplished using J-Boxes used for progressive desizing and Scouring for continuous equipment. The washed and desired Grey fabric is then padded using a powerful alkali solution (5-10 grams per lit NaOH or a mixture of NaOH and sodium carbonate) along with emulsifying as well as wetting agents. After securing the saturated Grey fabric, it is put into J-Box, which stays between 40 and 60 minutes in a plaited form, at around 100 deg. The cloth before entering J-Box is quickly preheated with steam inside a Uniform heating tube. The inside surface of the J-Box is exceptionally smooth to eliminate any friction within the cloth being moved.
Bleaching refers to removing natural coloring elements that cannot be removed from the fiber through thorough cleaning. Bleaching is also needed for Grey fabrics intended to be dyed in pastel shades, exceptionally light violets, and blues and for materials dyed using colors with maximum brightness. The principal goal of bleaching is to reach the desired amount of whiteness with the least harm to the fibers and with the least amount of time.
Presently, hydrogen- peroxide is the most frequently utilized bleaching agent. The sodium chloride (Na C1O2) and sodium hypochlorite bleaching powder, peracetic acid, and sulfur-di-oxide (SO2) gas in lesser amounts. sodium hydrosulfite (Na2 S2 O3), Ozone (O3)
Bleaching with Sodium hypochlorite
The Grey fabric or yarn following the scouring process is thoroughly cleaned before bleaching. It is then compressed or extracted hydro to get rid of excess water since it could dilute the bleach liquor, or “checking.”
In the typical batch treatment of cotton Grey fabric using sodium hypochlorite and kiers, it is made in the following manner:
Sodium hypochlorite, 1-3 gm/lit of chlorine available
The bath’s Ph is 11 and the temperature 11.5
The temperature of the room (30 to 40 degrees Celsius)
Time 45 mins to 2 hours
Since bleaching takes place in an alkaline medium (pH 10,11), the alkali found in the material is neutralized by the dilute mineral acid. This is known as ” souring.”
- An economical and efficient process for processing
- Unaffected by the shortcomings of bleaching powder
- Excessive chlorine may cause pollution
- All impurities in the protein should be obliterated before bleaching or the Grey fabric becomes yellow.
- Chlorine residues must be removed.
To eliminate the remaining chlorine from the cloth, it needs to be washed using sodium thiosulphate (chlorine dissolver) and hydrogen peroxide (weak solution). The chlorine will be rinsed off. This is known as ” antichlor.”
The Advantages of Bleaching With Hydrogen Peroxide
- Hydrogen peroxide is a universal chemical extensively used to bleach cotton Grey fabrics. It can be used for bleaching silk, wool, polyester, and other manufactured fibers with a broad range of conditions for use.
- It fixes Grey fabrics with less manipulation and, consequently, less work.
- The weight loss of Grey fabric during bleaching is lower than in hypochlorite bleaching.
- Peroxide bleached Grey fabrics are much more absorbent than bleached hypochlorite Grey fabrics.
- There is no chance of yellowing the Grey fabric.
- Bleaching using hydrogen peroxide can be accomplished using continuous or batch processes and room or high temperatures.
- Furthermore, hydrogen peroxide is cheap; it does not emit harmful chemicals or odors and doesn’t cause equipment corrosion.
Continuous Blanching Process
In this method, desizing bleaching and Scouring are put with bleaching and desizing. They are attractive alternatives because they save time or energy, work, and so on. is possible. But, combing operations do not always suffice to prepare specific cotton Grey fabrics for finishing and dyeing.
- In this process, the Grey fabric is then covered with the enzyme bath is then inserted into a moist steam chamber between 96Cbetween 96C and 100C, during which desizing occurs in less than one minute.
- The Grey fabric that is desizing has been coated with a solution comprising 46 percent NaOH with 1-3 g/l wetting agent and 1-3 g/l of Emulsifier over 3 to 5 minutes.
- The impregnation-treated Grey fabric is removed and put into a J-box, heated to 98C, and then left in the box for two hours, at which time the alkali reacts with impurities.
- The Grey fabric is then washed and impregnated with one percent hydrogen peroxide at pH 10.5-using1 percent sodium silicate to stabilize the Grey fabric and act as a wetting agent.
- The impregnation process is heated to 90-95C then put in J-box.
- Then, it is thoroughly rinsed.
Because the bleaching process occurs in alkaline conditions, the alkali in the substance needs to be neutralized by minerals in dilute form. The treatment using dilute hydrochloric acid or sulfuric acid is called souring.
The Grey fabric is treated with dilute hydrochloric acid or sulfuric acid in a room for 30 to 60 minutes. The materials are afterward thoroughly washed using water and dried.
The process of treating cotton Grey fabrics or yarns by an icy concentrated solution of sodium hydroxide solutions for less than one minute is referred to as mercerization. The cotton fibers expand, loosen, and their bean-shaped cross-section transforms into a round shape.
As cellulose expands within NaOH solution, many hydrogen bonds are ruptured, and the molecular structure can be disintegrated. Cellulose I is made by sodium hydroxide in levels that ranges from 12 to 19 (by weight). Soda cellulose II forms in concentrations ranging from 20 to 45 percent by weight. Cellulose I is a chain parallel configuration, while cellulose II has an anti-parallel.
Mercerized cotton is used primarily because of its improved dye quality and luster. The necessity for these characteristics is apparent when trying to achieve deep hues using vibrant reactive dyes. Additionally, the acquired brilliance can provide a shiny backdrop for the shades, further increasing their brightness.
Mercerization enhances some of the properties listed below.
- The strength would be increased by 15-25%
- Luster is further boosted;
- Higher attraction to dyes for water as well as various chemical finishings.
Grey Fabric is padded using around 20- 25% NaOH solution containing a wetting agent and placed over several cans for about one minute. Then, during this time, NaOH will enter the fibers and then react with the fibers. This is when the tension is applied lengthwise.
The Grey fabric is placed on the Tenter frame (tension is applied now in both weft and warp directions) and then pulled until it reaches the desired size. On the tenter frame, the Grey fabric is cleansed using spraying the water until the sodium hydroxide in the material is reduced to one or two.
The Grey fabric is taken off the frame of the tenter, and then the material is passed through several washers, each of which has a dilute solution of sulfuric acid or acetic acid. Takes out the remaining alkali.
The brightening agents that emit light, also known as “optical brightening” agents, enhance the apparent brightness or whiteness of the material and are employed in detergents, textiles, paints, papers, and so on.
The emission of radiation-generated light. These compounds are used to whiten. Can absorb ultraviolet light and emit more negligible radiation, i.e., visible light. A portion of the U.V. energy is converted into heat. The sun’s light contains U.V. radiations ranging from 300-380 nanometers (near U.V.) absorbed into optical brighteners used to whiten.
Optic whitening agents are applied to Grey fabrics during the process of Scouring, bleaching, or finishing. The brighteners florescent are required to remain solid in the bath for bleaching. They will also stay stable on the fiber in the heat setting temperature for polyester. Brighteners from florescent may be added to cotton Grey fabrics before resin treatments or added to the bath to formulate resin. When blended materials are used, it is a mix of two whiteners. It is appropriate for both of the fibers that are used.
Applications of Optical Brighteners
Optical brighteners depend on the type of fiber utilized and are consequently classified into direct, disperse, and cationic kinds. Natural brightening agents are used primarily to brighten linen, cotton, viscose, and nylon material. Acid florescent brightening substances serve mainly to illuminate wool and silk Grey fabric. The brightening agents disperse florescent are used chiefly for polyester, acetate, and acrylic materials.
Cleaning Of World
Raw wool comprises the following impurities: wool grease, soil particles of cellulose, dust, and saint (dried perspiration ), mostly potassium salts that are soluble.
I scoured with a detergent solution with a pH of 11 at a lower than 60’C temperature using anionic/non-ionic detergent and a tiny amount in weak base (0.4 percent Na 2Co 3) sodium carbonate or ammonia. This is enough to prepare the wool to spin. But wool must be scrubbed once more before dying.
Cellulose material like seeds, leaves, grass, along vegetable fibers is eliminated. The Grey fabric (sometimes free threads) is cleaned using a di. Solution. of Solution. Of 2. So 4, and then dried and then cured. Cellulose material decomposes to create an excellent black powder quickly sifted out.
The two types of bleaching methods are typically employed, namely. (i) an oxidation process employing hydrogen peroxide, as well as (ii) reduce technique using sodium bisulfate, sodium sulfate, and sodium hydrosulfite. Sometimes, the wool is bleached using peroxide and then bleached with sulfur dioxide.
A method of bleaching peroxide under acidic conditions is being developed, and the bath is composed of four volumes of hydrogen 2O 2containing 0.25 percent formic acid. It is adjusted to the pH range of 3 to 3.5 at room temperature. The scoured substance is coated by the peroxide solution onto mangles with padding and then left to rest for a night before being washed.
CLEANING of the SILK
Degumming of Silk
In its original state, Silk fiber has a thick layer of a glue-like substance or gum known as sericin that provides it with a rough and stiff feel and obscures the white and rich luster of the actual fiber. Silk-gum accounts for around 25 percent of the mass of silk in its raw form. Wild silks, such as Tasar silk, Eri silk, and Muga silk, also have gum. If the gum isn’t removed, silk doesn’t display its distinctive smoothness, luster, and luster as well as its softness. It also tends to color unevenly.
The process of removing the silk’s gum is referred to in the trade as “degumming” (also known as “boiling-off” as it is an essential pre-processing step. After the gum is eliminated, silk loses up to 30 percent of its mass.
Degumming using Synthetic Detergents
Synthetic detergents are becoming more popular in the place of soap. Their primary benefit is that they permit continued processing of individual items, and the duration of treatment is reduced, i.e., 40 minutes.
In this process, the product is treated using 2.5 up to five g/l of detergent (Sandopan SRS Liq. of Sandoz) at a pH of 11.2 up to 11.5 during 30-60 minutes at boiling, then rinsed thoroughly by using hot water, and later using cold water.
The downside of this method is that softness cannot always be achieved.
Degumming using Enzymes
This procedure is more extensive than synthetic detergents and requires a specific pre-treatment before the enzyme treatment, which requires the gum to expand.
The material is then treated using.
0.5 mg/l soda ash; 0.5 g/l Glauber’s salt three g/l of penetrating agents such as Imerol XN Liq. (Sandoz) in boiling water for approximately 1 hour.
Then, it is processed with 1-5 g/l of protein enzyme, one g/l soda ash two g/l Glauber’s Salt at 45 degrees Celsius for around one hour.
It is further processed in a 3rd bath comprising 0.5 mg/l soda ash 2.25 g/l sodium silicate two g/l of Imerol XN Liq. (Sandoz) 0.5 grams per liter of Glauber’s salt in a boiling bath for one hour.
It’s a process that involves three steps. Incorrect degumming could lead to mechanical damages that cause scratches on the surface. As consequently, the ends are dyed lighter shades.
Heat – Synthetic Grey Fabrics’ Setting
The thermosetting process of heat setting is a treatment applied to thermoplastic fibers, such as nylon or polyester to provide dimensional stability. Temperatures for setting in the heat are higher than the temperature at which glass is transitioned (Tog) for the Grey fabric. Heat is applied using steam, hot containers, or steam. The treated cloth gains the ability to maintain its dimensional stability. i.e., it is a recollection of the shape it took when heated.
It will withstand shrinkage and creasing and can hold wrinkles present within the Grey fabric during heat-setting treatment. Polyester Grey fabric is laid out on a tenter framework set to the desired width and then placed into the hot air oven with a temperature constant between 200 to 215oC between 30 and 90 minutes in the specific heat-setting process.
The heat setting process affects the dyeing capacity of the fiber. It usually reduces dyeability, so when it is done before dyeing, it is vitally crucial for the application of heat setting evenly. Uneven temperatures within the oven could change the Grey fabric’s color from selvage-to-selvage or selvage-to-center and will be apparent later as uneven dyeing.
Section Of Process Sequence
The choice of the correct process sequence is crucial in the efficiency of the subsequent processes like finishing, dyeing, etc. The most significant problems arise caused by a poor and incorrect selection of the process sequence. The Grey fabric’s preparation depends on the type of fiber and fiber blend composition, yarns, Grey fabric quality parameters, dimensions, requirements for colorfastness properties, and the endues.
Grey Fabrics made of cotton are subject to a modified procedure that includes singing, and desizing is often skipped when desizing cannot be missed for woven materials. Synthetic fibers are manufactured under controlled conditions since they contain minor impurities. Their cleaning is pretty simple. However, when they’re mixed with natural fibers, problems become more severe. The preparation of Grey fabrics also is contingent on the desired result. For instance, ” full white bleach” is utilized for white goods, half beach to prevent over-dyeing, or any large blotch and completely covered designs are printed. Full bleach is used when pastel shades are intended to dye. Cotton Grey fabrics dyed in deep shades will likely require mercerization to increase their dye capacity.
Grey Fabrics preparation is an expensive sequence of energy-consuming processes. The economics of the process has resulted in a significant change to the current arrangements of processing. The conventional pre-treatment process is cut down by single-stage bleaching, in which kiers remain in use. They are used to manage preparation costs by maximizing the sequence of the process, the conditions, and the design for shorter cycles. Additionally, various new kinds of equipment and more advanced techniques have been developed to satisfy effective but cost-effective and speedy cloth production. All of these elements require modification of processes for the most effective outcomes. The technologists can decide when any one of the steps is to be eliminated without damaging its quality. Products.