P. A. C. RAMASAMY RAJA POLYTECHNIC COLLEGE (COMMIUNICATION ENGLISH PRACTICAL) PROJECT CLASSIFICATION OF TEXTILE INDUSTRY (SPINNING & WEAVING) rocessing and treatment of raw cotton; spinning, throwing, texturising, creping, extruding, mercerising, impregnating, processing and treatment of fibres, filaments, threads, tyre cords, or yarns of all descriptions including animal or vegetable fibres, artificial silk, cotton, flax, pure silk, filament, synthetic fibres or wool, or any of them combined with one another or with any other animal, natural or synthetic fibre; weaving, including hand weaving braids, fabrics, materials and/or webbing tapes of all kinds and descriptions; dyeing, bleaching, coating, calendering, cleaning and/or finishing of all types of fabrics, filament yarns, wool tops, yarns and articles of all descriptions up to and including the completed product; printing including hand printing, screen and/or roller printing and stamping of fabrics and/or articles of all kinds and descriptions; mending and/or repairing (including invisible mending) of fabrics and/or articles of all kinds and descriptions; manufacturing of artificial silk, filament yarns, man made fibres and/or synthetic fibres; knitting and the manufacture of hosiery, half hose, children’s hose, underwear, outerwear, jersey piecegoods, fabrics and like goods or materials; storing, sorting, scouring, carbonising, mixing, blending and combing of wool and top-making; storing, blending, carding or garnetting of wool, hair, or other fibres, felting, needling, milling, tentering and/or drying; and every operation, process, duty and function or calling carried on or performed in or in connection with or incidental to any of the foregoing INDUSTRIAL PROCESS DESCRIPTION This section describes the major industrial processes in the textile industry, including the materials and equipment used and the processes employed.
The section is designed for those interested in gaining a general understanding of the industry, and for those interested in the interrelationship between the industrial process and the topics described in subsequent sections of this profile — pollutant outputs, pollution prevention opportunities, and Federal regulations. This section does not attempt to replicate published engineering information that is available for this industry. Refer to Section IX for a list of reference documents that are available. Note also that Section V, Pollution Prevention Opportunities, provides additional information on trade-offs associated with the industrial processes discussed in this section.
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This section describes commonly used production processes, associated raw materials, the byproducts produced or released, and the materials either recycled or transferred off-site. This discussion identifies where in each process wastes may be produced. This section concludes with a description of the potential fate (via air, water, and soil pathways) of process-specific waste products. III. A. INDUSTRIAL PROCESSES IN THE TEXTILE INDUSTRY Much of the following section is based upon “Best Management Practices for Pollution Prevention in the Textile Industry,” published by the U. S. EPA Office of Research and Development. Additional references are cited in the text.
The textile industry is comprised of a diverse, fragmentof establishments that produce and/or process textile-related products (fiber, yarn, fabric) for further processing into apparel, home furnishings, and industrial goods. Textile establishments receive and prepare fibers; transform fibers into yarn, thread, or webbing; convert the yarn into fabric or related products; and dye and finish these materials at various stages of production. The process of converting raw fibers into finished apparel and nonapparel textile products is complex; thus, most textile mills specialize. Little overlap occurs between knitting and weaving, or among production of manmade, cotton, and wool fabrics.
The primary focus of this section is on weaving and knitting operations, with a brief mention of processes used to make carpets. In its broadest sense, the textile industry includes the production of yarn, fabric, and finished goods. This section focuses on the following four production stages, with a brief discussion of the fabrication of non-appareled group ogoods : 1) yarn formation 2) fabric formation 3) wet processing 4) fabrication These stages are highlighted in the process flow chart shown in Figure 2 and are discussed in more detail in the following sections. A. 1. YARN FORMATION Textile fibers are converted into yarn by grouping and twisting operations used to bind them together.
Although most textile fibers are processed using spinning operations, the processes leading to spinning vary depending on whether the fibers are natural or manmade. Figure 3 shows the different steps used to form yarn. Note that some of these steps may be optional depending on the type of yarn and spinning equipment used. Natural fibers, known as staple when harvested, include animal and plant fibers, such as cotton and wool. These fibers must go through a series of preparation steps before they can be spun into yarn, including opening, blending, carding, combing, anddrafting. Natural Fibers Yarn formation can be performed once textile fibers are uniform and have cohesive surfaces.
To achieve this, natural fibers are first cleaned to remove impurities and are then subjected to a series of brushing and drawing steps designed to soften and align the fibers. The following describes the main steps used for processing wool and cotton. Although equipment used for cotton is designed somewhat differently from that used for wool, the machinery operates in essentially the same fashion. C Opening/Blending. Opening of bales sometimes occurs in conjunctionwith the blending of fibers. Suppliers deliver natural fibers to the spinning mill in compressed bales. The fibers must be sorted based on grade, cleaned to remove particles of dirt, twigs, and leaves, and blended with fibers from different bales to improve the consistency of the fiber mix. Sorting and cleaning is performed in machines known as openers.
The opener consists of a rotating cylinder equipped with spiked teeth or a set of toothed bars. These teeth pull the unbaled fibers apart, fluffing them while loosening impurities. Because the feed for the opener comes from multiple bales, the opener blends the fibers as it cleans and opens them. Carding. Tufts of fiber are conveyed by air stream to a carding machine, which transports the fibers over a belt equipped with wire needles. Aseries of rotating brushes rests on top of the belt. The different rotation speeds of the belt and the brushes cause the fibers to tease out and align into thin, parallel sheets. Many shorter fibers, which would weaken the yarn, are separated out and removed.
A further objective of carding is to better align the fibers to prepare them for pinning. The sheet of carded fibers is removed through a funnel into a loose ropelike strand called a sliver. Opening, blending, and carding are sometimes performed in integrated carders that accept raw fiber and output carded sliver. Combing. Combing is similar to carding except that the brushes and needles are finer and more closely spaced. Several card slivers are fed to the combing machine and removed as a finer, cleaner, and more aligned comb sliver. In the wool system, combed sliver is used to make worsted yarn, whereas carded sliver is used for woolen yarn.
In the cotton system, the term combed cotton applies to the yarn made from combed sliver. Worsted wool and combed chas not been combed because of the higher degree of fiber lignment and further removal of short fibers. Drawing. Several slivers are combined into a continuous, ropelike strandand fed to a machine known as a drawing frame (Wingate, 1979). Thedrawing frame contains several sets of rollers that rotate at successively faster speeds. As the slivers pass through, they are further drawn out and lengthened, to the point where they may be five to six times as long as they were originally. During drawing, slivers from different types of fibers (e. g. cotton and polyester) may be combined to form blends. Once a sliver has been drawn, it is termed a roving. Drafting. Drafting is a process that uses a frame to stretch the yarn further. This process imparts a slight twist as it removes the yarn and winds it onto a rotating spindle. The yarn, now termed a roving in ring spinning operations, is made up of a loose assemblage of fibers drawn into a single strand and is about eight times the length and one-eighth the diameter of the sliver, or approximately as wide as a pencil (Wingate, 1979). Following drafting, the rovings may be blended with other fibers before being processed into woven, knitted, or nonwoven textiles. Spinning.
The fibers are now spun together into either spun yarns or filament yarns. Filament yarns are made from continuous fine strands of manmade fiber (e. g. not staple length fibers). Spun yarns are composed of overlapping staple length fibers that are bound together by twist. Methods used to produce spun yarns, rather than filament yarns, are discussed in this section. The rovings produced in the drafting step are mounted onto the spinning frame, where they are set for spinning. The yarn is first fed through another set of drawing or delivery rollers, which lengthen and stretch it still further. It is then fed onto a high-speed spindle by a yarn guide that travels up and down the spindle.
The difference in speed of travel between the guide and the spindle determines the amount of twist imparted to the yarn. The yarn is collected on a bobbin. In ring spinning, the sliver is fed from delivery rollers through a traveler, or wire loop, located on a ring. The rotation of the spindle around the ring adds twist to the yarn. This is illustrated in Figure . Anotherotton yarns are finer (smaller) than yarn thatTextile Industry Industrial Process Description method, shown in Figure 4(2), is open-end spinning, which accounts for ore than 50 percent of spinning equipment used (ATMI, 1997b). In this method, sliver passes through rollers into a rotating funnel-shaped rotor.
The sliver hits the inside of the rotor and ebounds to the left side of therotor, causing the sliver to twist. Open-end spinning does not use rotating spindles since the yarn is twisted during passage through the rotorYarn spinning is basically an extension of the preparation steps described above for natural fibers. Additional twisting of the yarn may occur, or multiple yarns may be twisted together to form plied yarns. Plying takes place on a machine similar to a spinning frame. Two or more yarns pass through a pair of rollers and onto a rotating spindle. The yarn guide positions the yarn onto the spindle and assists in applying twist. Plied yarnsyarns may plied again to form thicker cords, ropes, and cables. .A. 2.
Fabric Formation The major methods for fabric manufacture are weaving and knitting. Figure 5 shows fabric formation processes for flat fabrics, such as sheets and apparel. Weaving, or interlacing yarns, is the most common process used to create fabrics. Weaving mills classified as broadwoven mills consume the largest portion of textile fiber and produce the raw textile material from which most textile products are made. Narrow wovens, nonwovens, and rope are also produced primarily for use in industrial applications. Narrow wovens include fabrics less than 12 inches in width, and nonwovens include fabrics bonded by mechanical, chemical, or other means.
Knitting is the second most frequently used method of fabric construction. The popularityof knitting has increased in use due to the increased versatility of techniques, the adaptability of manmade fibers, and the growth in consumer demand for wrinkle-resistant, stretchable, snug-fitting fabrics. Manufacturers of knit fabrics also consume a sizable amount of textile fibers. Knit fabrics are generally classified as either weft knit (circular-knit goods) or warp knit (flatknit goods). Tufting is a process used to make most carpets. WEAVING Weaving is performed on modern looms, which contain similar parts and perform similar operations to simple hand-operated looms.
Fabrics are formed from weaving by interlacing one set of yarns with another set oriented crosswise. Figure 6 shows an example of satin weave patterns. Satin, plain, and twill weaves are the most commonly used weave patterns. In the weaving operation, the length-wise yarns that form the basic structure of the fabric are called the warp and the crosswise yarns are called the filling, also referred to as the weft. While the filling yarns undergo little strain in the weaving process, warp yarns undergo much strain during weaving and must be processed to prepare them to withstand the strain (Corbman, 19Before weaving, warp yarns are first wound on large spools, or cones, which are placed on a rack called a creel.
The warp yarns are then unwound and passed through a size solution (sizing/slashing) before being wound onto a warp beam in a process known as beaming. The size solution forms a coating that protects the yarn against snagging or abrasion during weaving. Slashing, or applying size to the warp yarn, uses pad/dry techniques in a large range called a slasher. The slasher is made up of the following: a yarn creel with very precise tension controls; a yarn guidance system; and a sizing delivery system, which usually involves tank storage and piping to the size vessels. The yarn sheet is dipped one or more times in size solution and dried on hot cans or in an oven. A devise called a “lease” is then used to separate yarns from a solid sheet back into individual ends for weaving (EPA, 1996).
Starch, the most common primary size omponent, accounts for roughly twothirds of all size chemicals u. sed in the U. S. (130 million pounds per year). Starch is used primarily on natural fibers and in a blend with synthetic sizes for coating natural and synthetic yarns. Polyvinyl alcohol (PVA), the leading synthetic size, accounts for much of the remaining size consumed in the U. S. (70 million pounds per year). PVA is increasing in use since it can be recycled, unlike starch. PVA is used with polyester/cotton yarns and pure cotton yarns either in a pure form or in blends with natural and other synthetic sizes. Other synthetic sizes contain acrylic and acrylic copolymer components.
Semi synthetic sizes, such as car boxy methyl cellulose (CMC) and modified starches, are also used. Oils, waxes, and other additives are75) often used in conjunction with sizing agents to increase the softness and pliability of the yarns. About 10 to 15 percent of the weight of goods is added as size to cotton warp yarns, compared to about 3 to 5 percent for filament synthetics. Once size is applied, the wound beam is mounted in a loom. Shuttle looms are rapidly being replaced by shuttleless looms, which have the ability to weave at higher speeds and with less noise. Shuttleless looms are discussed in the next section. The operation of a traditional shuttle loom is discussed in this section to illustrate the weaving process.
The major components of the loom are the warp beam, heddles, harnesses, shuttle, reed, and takeup roll (see Figure 7). In the loom, yarn processing includes shedding, picking, battening, and taking up operations. These steps are discussed below. Shedding. Shedding is the raising of the warp yarns to form a shed through which the filling yarn, carried by the shuttle, can be inserted. The shed is the vertical space between the raised and unraised warp yarns. On the modern loom, simple and intricate shedding operations are performed automatically by the heddle frame, also known as a harness. This is a rectangular frame to which a series of wires, called heddles, are attached.
The yarns are passed through the eye holes of the heddles, which hang vertically from the harnesses. The weave pattern etermines which harness controls which warp yarns, and the number of harnesses used depends on the complexity of theC Taking up and letting off. With each weaving operation, the newly constructed fabric must be wound on a cloth beam. This process is called taking up. At the same time, the warp yarns must be let off or released from the warp beams (Corbman, 1975). weave (Corbman, 1975). Picking. As the harnesses raise the heddles, which raise the warp yarns, the shed is created. The filling yarn in inserted through the shed by a small carrier device called a shuttle.
The shuttle is normally pointed at each end to allow passage through the shed. In a traditional shuttle loom, the filling yarn is wound onto a quill, which in turn is mounted in the shuttle. The filling yarn emerges through a hole in the shuttle as it moves across the loom. A single crossing of the shuttle from one side of the loom to the other is known as a pick. As the shuttle moves back and forth across the shed, it weaves an edge, or selvage, on each side of the fabric to prevent the fabric from raveling. Battening. As the shuttle moves across the loom laying down the fill yarn, it also passes through openings in another frame called a reed (which resembles a comb).
With each picking operation, the reed presses or battens each filling yarn against the portion of the fabric that has already been formed. Conventional shuttle looms can operate at speeds of about 150 to 160 picks per minute SHUTTLELESS LOOMS Because the shuttle can cause yarns to splinter and catch, several types of shuttleless looms have been developed. These operate at higher speeds and reduced noise levels. By the end of 1989, shuttleless looms represented 54 percent of all looms installed, up from 15 percent in 1980. Shuttleless looms use different techniques to transport cut pieces of fill yarn across the shed, as opposed to the continuous yarn used in shuttle looms.
Some of the common shuttleless looms include water-jet looms, air-jet looms, rapier looms, and projectile looms. Water-jet looms transport the fill yarn in a high-speed jet of water and can achieve speeds of 400 to 600 picks per minute. Water jets can handle a wide variety of fiber and yarn types and are widely used for apparel fabrics. Air-jet looms use a blast of air to move the fill yarn and can operate at speeds of 800 to 1000 picks per minute. Rapier looms use two thin wire rods to carry the fill yarn and can operate at a speed of 510 picks per minute. Rapiers are used mostly for spun yarns to make cotton and woolen/worsted fabrics. In a double rapier loom, two rodsmove from each side and meet in the middle.
The fill yarn is carried from the rod on the fill side and handed off to the rod on the finish side of the loom. Projectile looms use a projectile to carry the fill yarn across the weave. Shuttleless looms have been replacing the traditional fly-shuttle loom in recent years. Air looms, although limited in the types of filling yarns they can handle, are increasing in commercial use. The operation of an air jet loom is shown in Figure 8. As shown in the figure, yarn is drawn from the yarnpackage (1) by the measuring wheel and drive roller arrangement (2). Between the yarn package and the measuring wheel is a tube through which an air current flows in opposite direction to the yarn. This maintains a straight even feed of yarn.
The yarn then forms a loop (3) which shortens as the pick penetrates further into the shed. The main jet (4) is the major projecting force for the yarn, although supplementary jets (5) are activated prevent the pick from buckling. to Knitting Knitted fabrics may be constructed by using hooked needles to interlock one or more sets of yarns through a set of loops. The loops may be either loosely or closely constructed, depending on the purpose of the fabric. Knitted fabrics can be used for hosiery, underwear, sweaters, slacks, suits, coats, rugs, and other home furnishings. Knitting is performed using either weft or warp processes, depicted in Figure 9.
In weft (or filling) knitting, one yarn ishorizontally in the fabric, and connections between loops are horizontal. In warp knitting, a warp beam is set into the knitting machine. Yarns are interlocked to form the fabric, and the yarns run vertically while the connections are on the diagonal. Several different types of machinery are used in both weft and warp knitting carried back and forth and under needles to form a fabric. WEFT KNITTING. Weft knitting uses one continuous yarn to form courses, or rows of loops, across a fabric. There are three fundamental stitches inweft knitting: plain-knit, purl, and rib. On a machine, the individual yarn is fed to one or more needles at a time. Weft knitting machines can produce both flat and circular fabric.
Circular machines produce mainly yardage but may also produce sweater bodies, pantyhose, and socks. Flatbed machines knit full garments and operate at much slower speeds. The simplest, most common filling knit fabric is single jersey. Double knits are made on machines with two sets of needles. All hosiery is produced as a filling knit process. WARP KNITTING. Warp knitting represents the fastest method of producing fabric from yarns. Warp knitting differs from weft knitting in that each needle loops its own thread. The needles produce parallel rows of loops simultaneously that are interlocked in a zigzag pyarns are fed from warp beams to a row of needles xtending across the width of the machine (Figure 9b). Two common types of warp knitting machines are the Tricot and Raschel machines. Raschel machines are useful because they can process all yarn types in all forms (filament, staple, combed, carded, etc. ). Warp knitting can also be used to make pile fabrics often used for upholstery. TUFTING Tufting is a process used to create carpets, blankets, and upholstery. Tufting is done by inserting additional yarns into a ground fabric of desired weight and yarn content to create a pile fabric. The substrate fabric can range from a thin backing to heavy burlap-type material and may be woven, knitted, or web.
In modern tufting machines, a set of hollow needles carries the yarn from a series of spools held in a creel and inserts the yarn through the substrate cloth. As each needle penetrates the cloth, a hook on the underside forms a loop by catching and holding the yarn. The needle is withdrawn and moves forward, much like a sewing machine needle. Patterns may be formed by varying the height of the tuft loops. To make cut-loop pile, a knife is attached to the hook and the loops are cut as the needles are retracted. Well over 90 percent of broadloom carpeting is made by tufting, and modern machines can stitch at rates of over 800 stitches per minute, producing smatter. Fabric is produced in sheet or flat form using one or more sets of warp yarns. The Yarns run 650 square yards of broadloom per hour.