Textile dyeing Process | Textile dyeing methods | Dyeing process
In this article, garment merchandiser will discuss Textile dyeing Process | Textile dyeing methods | Dyeing process. Dyeing is governed by three factors, the dye, the fiber and also the dye liquor. All the three lead an independent assistance which influences the technique of dyeing. A dye must be water soluble so as to dye textile materials. it’s going to be soluble naturally of its chemical interference.
The dyeing process can thus be considered as happening in three phases
1. Attachment of the dye molecule to the surface of the fiber
2. Penetration into the intermolecular spaces yet as diffusion through the fiber &
3. Orientation (and fixation) along the long chain molecules.
The solution of the dye from which it’s applied is named the „dye bath‟. A dye may have direct „affinity‟ for a fiber (or vice versa) i.e., it’s held by the fiber either physically (absorption) or chemically (combination) as soon because the fiber is immersed within the dye bath.
Accumulation of the dye within the fiber may be a gradual process, the speed of such build up being spoken because
the ‘rate of dyeing’.
1. This rate of dyeing is governed by the condition of the dye bath, namely concentration of dye, temperature, and presence of electrolytes; it’s proportional to any or all three factors.
2. The speed of dyeing is additionally influenced by the „Material to liquor‟ which is expressed by a fraction, e.g. 1:20, which suggests one part (by weight) of the textile material dyed in twenty times its weight of dye bath.
3. The speed of dyeing decreases with increasing ratio of products to liquor.Dyeing is distributed to supply a specific „Shade‟ by which is supposed a specific color, difference in shade being because of different ‟Hue‟. A blue shade may, as an example, have a greenish or a reddish hue. The amount of dye needed for the assembly of a specific depth of shade is expressed as a percentage of the load of the fabric. a tenth dyeing represents a shade produced by the coloring of 100 lbs. of fabric with one lb. of (commercial) dye under well-defined dyeing conditions. it’s necessary to define these conditions due to their influence on the „exhaustion‟ of the dye bath. Exhaustion determines that quantity of dye which is concerned the fiber or in directly, that quantity which remains within the dye bath after „equilibrium‟ between dye and fiber is reached, i.e., at that time where no further dyeing takes place.
“The process of applying color to fiber stock, yarn or fabric is named dyeing.” There may or might not be thorough penetration of the colorant into the fibers or yarns.
Dyes are often used on vegetable, animal or simulated fibers given that they need affinity to them. Textile dyes include acid dyes, used mainly for dyeing wool, silk and nylon and direct or substantive dyes, which have a powerful affinity for cellulose fibers. Mordant dyes require the addition of chemical substances, like salts to offer them an affinity for the fabric being dyed. they’re applied to cellulose fibers, wool or silk after such materials are treated with metal salts. Sulfur dyes, accustomed dye cellulose, are inexpensive, but produce colors lacking brilliance. Azoic dyes are insoluble pigments formed within the fiber by padding, first with a soluble coupling compound and so with a diazotized base. Vat dyes, insoluble in water, are converted into soluble colorless compounds by means of alkaline sodium hydrosulfite. These colorless compounds are absorbed by the cellulose,which are subsequently oxidized to an insoluble pigment. Such dyes are colorfast. Disperse dyes are suspensions offinely divided insoluble, organic pigments accustomed dye such hydrophobic fibers as polyesters, nylon and cellulose acetates.
Reactive dyes combine directly with the fiber, leading to excellent color fastness. The primary ranges of reactive dyes
for cellulose fibers were introduced within the mid-1950. Today, a good variety is on the market.
Methods of Dyeing
1) Beam Dyeing:
In this method the warp is dyed before weaving. it’s wound onto a perforated beam and also the dye is forced through the perforations thereby saturating the yarn with color.
2) Burl or speck Dyeing:
This is done totally on woolens or worsted, colored specks and blemishes are covered by the employment of special colored links which are available in many colors and shades. it’s a hand operation.
3) Jig Dyeing:
This is exhausted a jig, kier, vat, beck or vessel in an open formation of the products. the material goes from one roller to a different through a deep dye bath until the required shade is achieved.
4) Cross Dyeing:
This is a really popular method within which varied color effects are obtained within the one dye bath for a cloth which contains fibers with varying affinities for the dye used. for instance, a blue dyestuff might give nylon 6 a blueness shade, nylon 6, 6 a lightweight blue shade, and haven’t any affinity for polyester area unscathed or white.
5) Solution Dyeing:
This is also called dope dyeing or spun dyeing; the pigment color is bonded-in within the solution and is picked up because the filaments are being formed within the liquor. Cellulosic and non-cellulosic fibers are dyed just right by this method. the colours are bright, clear, clean and fast.
6) Bale Dyeing:
This is an occasional cost method to dye cloth. the fabric is distributed without scouring or singeing, through a chilly water bath where the sized warp has affinity for the dye. Imitation chambray and comparable fabrics are often dyed this manner.
7) Batik Dyeing:
This is one in every of the oldest forms known to man. It originated in Java. Portions of the material are coated with wax in order that only un-waxed areas will tackle the dye matter. The operation is also repeated several times and several other colors may used for the bizarre effects. Motifs show a mlange, mottled or streaked effect, imitated in machine printing.
8) Chain Dyeing:
This is used when yarns and cloth are low in enduringness. Several cuts or pieces of material are tacked end-to-end and run through in a very continuous chain within the dye color. This method affords high production.
9) Piece Dyeing:
The dyeing of materials within the cut, bolt or piece form is named piece dyeing. It follows the weaving of the products and provides one color for the fabric, like blue serge, a green organdy.
10) Random Dyeing:
Coloring only certain designated portions of the yarn. There are 3 ways of doing this kind of coloring:Skeins is also tightly dyed in two or more places and dyed at one side of the dye with one color and at the opposite side with another one. Color is also printed onto the skeins which are detached on the blanket fabric of the machine.
Cones or packages of yarn on hollow spindles is also arranged to create channels through which the yarn, by means of air-operated punch, and also the dyestuff are drawn through these holes by suction. The yarn within the immediate area of the punch absorbs the dye and also the random effects are thereby attained.
11) Raw Stock Dyeing:
Dyeing of fiber stock precedes spinning of the yarn. Dyeing follows the degreasing of wool fibers and drying of the stock.
12) Yarn dyed:
Yarn which has been dyed before the weaving of the goods; follows spinning of the yarn. it should be exhausted either partial immersion or total immersion of the yarn.
Process of Dyeing
The dyeing of a textile fiber is dispensed during a solution, generally aqueous, called the dye liquor or dye bath. For true dyeing to own taken place, coloration of cloth and absorption are important determinants.
The coloration must be relatively permanent: that’s not readily removed by rinsing in water or by normal washingprocedures. Moreover, the dyeing must not fade rapidly on exposure to light.
The process of attachment of the dye molecule to the fibre is one in all absorption: that’s the dye molecules consider the fibre surface. There are four varieties of forces by which dye molecules are sure to the fiber:
1) Ionic forces
2) Hydrogen bonding
3) Vander Wals’ forces and
4) Covalent chemical linkages
Dyeing of Wool:
In the dyeing of wool which could be a complex protein containing about 20 different amino acids, the oil of vitriol added to the dye bath forms ionic linkages with the amino groups of the protein. within the process of dyeing,the sulfate anion (negative ion) is replaced by a dye anion. within the dyeing of wool, silk and artificial fibers, hydrogen bonds are probably founded between the azo, amino, alkyl amino and other groups and also the amino Co-NH-groups. Covalent chemical links are caused within the dye-bath by reaction between a fiber-reactive dye molecule, one containing a chemically reactive center and a hydro-oxy group of a cotton fiber, within the presence of alkali.
The Chemistry of the Dyeing Process
Exhaustion in any dyeing process, regardless of the chemical class of dye being employed, heat must be supplied tothe dye bath; energy is employed in transferring dye molecules from the answer to the fiber similarly as in swelling the fiber to render it more receptive. The technical term for this process is exhaustion. Levelness: a crucial Quality Evenness of dyeing, called levelness is a crucial quality within the dyeing of all sorts of natural and artificial fibers. it should be attained by the control of dyeing conditions viz.
1. By agitation to make sure proper contact between dye liquor and substance being dyed and by use of restraining agents to manage rate of dyeing or strike. Solvent Dyeing Serious consideration has recently been given to the methods of dyeing within which water because the medium is replaced by solvents like the chlorinated hydrocarbons employed in cleansing. The technological advantages in solvent dyeing are:
- Rapid wetting of textiles
- Less swelling
- Increased speed of dyeing per given amount of fabric
- Savings in energy, as less heat is required to heat or evaporate per-chloro-ethylene. Thus it eliminates the
- effluent (pollution) problems related to the traditional methods of dyeing and finishing.
Machines & Equipment:
Machinery and Equipment : Modern dyeing machines are made up of stainless steels. Steels containing up to 4% molybdenum are favored to face up to the acid conditions that are common.
A dyeing machine consists essentially of a vessel to contain the dye liquor, supplied with equipment forheating, cooling and circulating the liquor into and round the goods to be dyed or moving the products through the dye liquor. the type of machine employed depends on the character of the products to be dyed. Labor and energy costs are high in relevancy total dyeing costs: the dyers aim is to shorten dyeing times to save lots of steam and wattage and to avoid spoilage of products.
The conical-pan loose-stock machine could be a widely used machine. Fibers are held in an inner truncated conical vessel while the recent dye liquor is mechanically pumped through. The fiber mass tends to become compressed within the upper narrow half the cone, assisting efficient circulation. Leveling problems are decreased as uniformity is also achieved by blending the dyed fibers before spinning.
The Hussong machine is that the traditional apparatus. it’s a protracted, square-ended tank as a dye bath into which a framework of poles carrying hanks is lowered. The dye liquor is circulated by an impeller and moves through a perforated false bottom that also houses the open steam line for heating. In modern machines, circulation is improved at the points of contact between hank and pole. This results in better leveling and elimination of irregularities caused by uneven cooling. In package-dyeing machines dye color is also pumped in rather two directions: 1.through the perforated central spindle and outward through the package or
2. By the reverse path into the outer layers of the package and out of the spindle. In either case levelness is vital.
Some package-dyeing machines are capable of working besieged at temperatures up to 130C.
The winch is that the oldest piece of dyeing machine and takes its name from the slated roller that moves an endless rope of fabric or endless belt of fabric at full width through the dye liquor. Pressurized-winch machines are developed within the U.S.
In a completely new concept, the Gaston County jet machine circulates fabric in rope form through a pipe by means of a high-pressure jet of dye color. The jet machine is increasingly important in high-temperature dyeing of synthetic fibres, especially polyester fabrics. Another machine is that the jig. it’s a V-shaped trough holding the dye color and guide rollers to hold the fabric at full width between two external, powered rollers, the fabric is wound onto each roller alternately, that is, the fabric is first moved forward, then backward through the dye color until dyeing is complete. Modern machines, automatically controlled and programmed, may be built to figure besieged.
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