How to dye and procedure of dyeing for textile

Pretreatment Processes of dyeing

2013-06-06T00:32:00.001+06:00

Dyeing Pretreatment :

Pretreatment processes of dyeing consist of cleaning operations to rid the fabric of all soil and additives that have accumulated during the weaving or knitting process. These processes are usually the first treatments a fabric undergoes after leaving the loom or knitting machine, and are required before any dyeing, printing, or finishing can be accomplished. In the strict definition of finishing, pretreatment processes do not quality as textile finishes because they are performed prior to dyeing or printing

Grey goods contain warp starches or other sizing (to add stiffness and strength to warp yarns during weaving), as well as oils, waxes, and other lubricants, plus floor dirt or other soils picked up during processing. Complete removal of all these impurities is necessary before any dyeing; printing, or finishing can be done. The processes for cleaning are varied depending on the fiber, the impurities present, and the fabric construction. In cotton, cotton-blend, silk, and manufactured-fiber fabrics, the processes are generally known as the boil-off. In woolens and worsteds, it is called a scour or scouring. Boil-off or scouring is similar to ordinary laundering. Fabrics are treated with soaps or detergents, rinsed, and then dried. If warp starches are present, the fabric is treated with an additional process known as desizing. Enzyme solutions are used to dissolve the starch.

Woolen and worsted fabrics may undergo an additional pretreatment process known as carbonizing. This process removes leaf particles and bits of grass and other cellulosic impurities that become embedded in the wool white sheep are grazing. The treatment consists of steeping the wool fabric in sulfuric acid, which destroys the cellulose but leaves the wool unharmed.

Another dyeing pretreatment process is an operation called singeing, which involves burning off projecting fibers or filament splinters from the surface of a fabric. Improper singeing or elimination of this operation results in unclear print patterns, mottled fabric surface, or premature pilling of fabrics. . Singeing is accomplished by passing gray goods rapidly over gas flames, usually two burners to a side, at a speed of 100 to 250 yards per minute. Improper singeing or elimination of this operation results in unclear print patterns, mottled fabric surface, or premature pilling of fabrics.

Dyeing pretreatment processes may also include bleaching. Fabrics to be dyed in light to medium shades, as well as most prints, are first bleached. Bleaches are required to obtain pure whites because natural fibers are rarely pure white in their natural state; they are usually slightly yellowish or grayish. Bleaches are chemical agents that react with the color compounds in the fiber and render them colorless. Our eyes see the fabric as pure white.

The effectiveness of optical brighteners after dyeing is dependent on an ultraviolet source of light. Natural sunlight is such a source. Fluorescent lighting is also, but to a small degree. Ultraviolet lamps (also called black-light lamps) are another source. Incandescent lighting (regular household bulbs) contains no ultraviolet, so optical brighteners have no effect on fabrics used under this lighting.

The Dyeing Process

2013-06-06T00:24:00.001+06:00

The science of dyeing is highly complex, and the mechanisms of dyeing are not completely understood. This discussion about dyeing is necessarily superficial and does not provide an in-depth exploration of the subject. The medium most often used to dissolve or disperse dyes for application to textiles is water. The dye solution, called the dye liquor, is agitated or circulated to increase the migration of the dye to the fiber surface. The attraction or affinity of the dye for a particular fiber is influenced by several factors. Different dye types are attracted chemically or physically to specific fibers.

Fibers often undergo swelling in aqueous dyeing processes, increasing dye absorption. For hydrophobic fibers that do not swell in water, organic solvents can be used as swelling agents or “carriers” for the dye. Mordants can be added to increase the acceptance of dyes. Dyebath additives such as these are classed as dye auxiliaries. Surface features such as the scales on wool or waxes or finishes on fibers can inhibit attraction of the dye to the fiber. Careful preparation of fabrics for dyeing minimizes this effect by removing waxes and sizes. Further, application of aesthetic and functional finishes usually follows the dyeing process, so that the dyeing finishes do not compete for dye sites on the fiber.

Once dyes are attracted to the fiber, they should diffuse through it rather than remaining adsorbed on the surface. Dyes are absorbed into the fiber predominantly in the amorphous areas, and making these areas larger or more accessible enhances the dyeing process. Mercerization of cotton, which moves the polymer chains farther apart, allows more dye in. Higher temperatures, around the glass transition phase of thermoplastic fibers, cause some of the crystalline areas to move and separate more, increasing dye accessibility. Nylon fibers have a low glass transition temperature and can often pick up dyes from other fibers.

Exhaustion is the amount of transfer of dye from the dye bath to the fiber, either by adsorption or absorption of dyes. It is possible for all the dye to be removed from the dyeing bath and for the dye bath to be clear at the end of the dyeing process. Some dye classes exhaust better than others. It is not always prudent or even necessary, to dye to complete exhaustion of the bath.

A concern in dyeing is how evenly distributed the dye is in the fiber, a characteristic known as levelness. Low leveling will result in a streaked appearance of the fabric.

Dyes may be only adsorbed on the fiber surface, or dyes that have been absorbed by fibers may migrate back to the surface when the textile is dried, resulting in uneven dyeing. Leveling agents and retarders are dye-bath auxiliaries than can promote even dye absorption.

Once the dye has entered the amorphous regions of fiber, it must be retained within the fiber not only during the dyeing but also when fabrics are laundered or dry cleaned during use. Several factors make for dye retention. The nature of the dyeing chemical bonds and physical attraction between fiber and dye is a crucial element. Dyes may be physically bound to fibers by forces such as hydrogen bonding or ionic forces. Ionic forces are the attraction between positively and negatively charged ions, one on the dye, and the other on the fiber. The chemical structure of dye and fiber may allow the formation of covalent chemical bonds between fiber and dye. Dyes that are absorbed into swollen fibers can be physically trapped when the fibers are cooled and dried. Dyes that are soluble in water, which may also swell some fibers, can be removed when the textile is wetted during dyeing.

Dyeing methods of Direct dyes

2013-05-20T20:31:00.000+06:00

Direct dye is populae and conventional dye. There are some popular dyeing method of direct dyeing with suitable dyeing machine those are describeb bellow:

I. Batch method: With batch dyeing, the dyeing method to be selected in each case depends on the type of dyeing equipment (loading system, winch vat, jig, paddle or jet), the nature of the material to be dyed, as well as the solubility and the affinity of the dye. Before the actual dyeing process, the material is pre-treated with a wetting agent. The dye is mixed into a paste with some warm water, and is then diluted with more water, boiled up, filtered, and then added to the dyebath.

Whilst the bath, with the fabric, heats up to the optimum temperature (usually 80–90°C), the electrolyte is added, gradually if necessary. Dyeing takes 30–60 minutes. After the dyebath has been run off, the dyed material is briefly rinsed with cold water and, in general, subjected to after-treatment. The dyeing process is divided into 3 phases: a) uptake (adsorption) through substantivity; b) penetration of the dye into the fibre (diffusion); c) bonding to the fibre (immobilisation) through van der Waals interactions. Assurance of level take-up through progessive addition of salt, temperature control, sufficiently long dyeing time, and use of levelling agents.

II. High-temperature dyeing method: With suitable dyes, one can work in a closed system at temperatures over 100°C (up to approx. 130°). Due to the rapid diffusion rate, particularly level dyeings are achieved with short dyeing times, even with fabric with difficult dye penetration. After the high-temperature phase, the dyebath is cooled down to 80–90°C, with dye pick-up continuing, and the result is the same depth of colour as in the normal dyeing method at 80–90°C.

III. Continuous and semi-continuous method: With these so-called pad methods, the dyeing material, mostly in the form of woven fabric, is first of all steeped in a concentrated dye solution, passed full-width through a trough filled with the dye solution, and subsequently the excess liquor is removed between the rubber rollers. With high fabric speed, temperatures as low as possible (30–40°C for light shades, 60–80°C for medium to dark shades), and with the minimum amount of pad liquor, the situation can be avoided where the dye already picks up substantively in the padding process. Distinction may be made between the following methods:

1. Pad-jig method: Pad, salt bath develop on jig or winch vat.

2. Pad-roll method: Pad, heat up in an IR zone, roll up and rotate in a dwell chamber for a considerable time under fixation temperature/moisture conditions.

3. Pad-salt method: Pad, pass through salt solution at boil in continuous piece-dyeing machine (light shades only; for darker shades an intermediate steam process is necessary).

4. Pad-steam method: Pad, continuous steam, optional final salt bath.

5. HT-steam method: Pad, HT-steam.

After-treatment: The wetfastness properties of direct dyeings are not adequate for the demands of everyday use, particularly in medium and deep shades.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Direct dyes

2013-05-20T20:15:00.000+06:00

Direct dyes are very conventional dyes. It is not used any more for industrial dyeing. Direct dye is one kind of anionic dye and having substantively for all types of cellulosic fibre like cotton, jute, hemp. They have strong affinity to the fibre which can be applied directly on the fibre surface and do not need any assistance.

Direct dye Also known as direct, substantive, benzidine or salt dyes. Group classification for dye which exhaust substantively on cellulosic fibres, cotton, viscose, cupro and high wet modulus fibres, especially in the presence of salt. Chemically they are polyazo or sulphonated disazo dye.It contains sulphonic acid group that’s why is has good solubility in water. The dye molecule contains a complex bond metal atom that’s why they have high light fastness properties. The color fastness is poor but it is easy to improve by dyeing after treatment with metal salts (Õ Aftercoppering dyes).

Benefit of Direct dye:
Direct dyes represent the main class of dyes for cellulosic fibres in terms of usage:
- Specially selected direct dyes are available for streaky dyeing viscose qualities.
- They are simple to apply.
- Economical or cost effective than any other dyes.
- It has generally good leveling properties
- A wide range of color variation and shade.
- Special types contain better wet fastness. It is possible to couple with readily soluble diazo compound by after treatment.
-Direct dyeing on cellulosic fibres exhibit considerable differences in colour fastness to light which ranges between 1 and 7–8.

Different direct dyes can therefore be used for articles which are only required to have low light fastness as well as goods with high light fastness. In general, direct dyes have poor wet fastness properties and dyeing must be after treated to improve their serviceability.

Properties of direct dye:
- Direct dye has sodium salt of sulphonic acid or carboxylic acid group. So it easily dissolve in water.
- Cheap comparative
- It has strong affinity to cellulose fibre. It is possible to dye protein fibre.
- Easily disperse in water and diffusible in to fibre.
- Wash fastness is not good. The range vary from 2 to 3
- It is possible to use in neutral and alkaline medium
- The dye is common in the practical point of view.
- The tin tropical power of this dye is very good.

Some trade and brand name of direct dyes
Benzo, Benzoform       - F.Bayer (Germany)
Coprantine                  - Ciba-geigy (Switzerland)
Solphenyl    - Ciba-geigy (Switzerland)
Chlorazol Durazol    - Impartial Chemical Industry (ICI)
Solar                          - Sandoz A.G (Switzerland)

There are some related posts to get deep knowledge of direct dye:

# Classification of Direct dye
# How to dye with direct dyes
# Dyeing aftertreatment of direct dye
# Chemistry of dyeing related to direct dye
# Dyeing auxiliaries required for direct dye

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

State the problems occurred in dyeing due to water hardness

2013-05-08T00:46:00.000+06:00

Problem occurring in dyeing due to hardness:

Potential dangers of textile items:
a) Potential dangers:

1) Reduced depth of shade: Dyeing shade is a vital point of industrial coloration process. Shade of a color is depend upon the choromophore or auxochoromophore groups of dyes. The material reserved in hard water can change the choromophore complex ions. In that case it is not possible to get desire shade percentage.

2) Dulling of shade: This is a big problem in dyeing. Water hardness change the activities of dyes chemical that’s why dyeing machine could not properly dull the shade.

3) Unleveled dyeing: It is one of the common and major problem in dye house. It means the variation of color shade in same amount of fabric or other textile material which are dyed in same dyeing bath and batch. Water hardness is one of the main issue of uneven dyeing.

4) Poor shade reproducibility: Shade reproducibility is not a usual operation on dyeing industry. It used to fix the shade according to buyer requirement if it is not up to slandered. It means refit the dyed fabric according to the required shade due to achieve the proper shade. Usually uneven dyed fabric need to shade reproduce. To reduce the shade stripping is required but increase the shade, usually need to re-treatment with dyes and chemicals.

5) Damaged fiber: Degree of hydrogen (PH) is important issue in dye liquor. Hard water contains organic salt that’s why it can change the acidity or alkality of dye and auxiliary solution. On the other hand every fibre have a tolerant limit of acid alkali. As the hard water change the PH of dye solution so the solution could be harmed the fibre. I we rework with dyed material due to dull or unleveled shade, it could easily damage the textile fibre due to more chemical expose.

b) Problem in boiler:
-Scale formation: Hard water makes scales inside the wall and tubes of boiler. It create a layer of organic salt and it is difficult remove the scale inside the boiler.

-Heat loss: It also the cause of heat loss inside boiler.

c) Wastage of soap: Hard water contains the organic salt and oxides ions. Those ions react with soap and reduce the working capability soap and need more soap to maintain the exact ratio during scouring and bleaching.

d) Problem in machine: It makes corrosion of boiler and looses its life time.

e) Problem in processing:
Desizing, Scouring, Dyeing, Printing, Finishing

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Bleaching

2013-05-05T01:26:00.002+06:00

Bleaching used for:

Destruction of color impurities for
1. producing base white for subsequent dyeing
2. Producing permanent white

But it may not always be necessary:
1. For synthetic fiber
2. For deep shade
3. In some cases it may require partial bleach.

Parameter for H2O2 Bleaching:
1. Concentration of H2O2
2. Concentration of alkali
3. pH
4. Temperature
5. Time
6. Nature & quality of goods
7. Water hardness & other impurities
8. Types & concentration of auxiliaries
9. Available machine & stabilizer system employed
10. Desired bleaching effect

Status nascendi: In which point where active oxygen will get.

pH < 10 practically no HOO-
pH 10-11 Low to moderate HOO-
pH > 11 Moderate to high HOO-

Major bleaching agent:

Oxidative bleaches:
1. Hydrogen peroxide H2O2
2. Persulfate (NH4)2 S2O8, K2S2O8, Na2S2O8
3. Peracetic acid CH3CO.O.OH
4. Sodium hypochloride, NaOCl
5. Sodium hypochloride, available in bleaching powder with approximate formula 3Ca(OCL)Cl.Ca(OH)2.5H2O
6. Sodium chloride NaClO2

Reactive bleaches:
1. Sulfur dioxide SO2
2. Sodium hyposulfite NaS2O4

Advantages of H2O2 or why called universal bleaching agent

1. Most widely used for the natural cellulosic fibers( cotton, flax, Linen, jute etc) as well as the protein fibers (wool, Silk etc) regenerated cellulose fiber &natural fiber blends.

2. Extremely versatile bleaching agent, applicable over a very wide range of bleaching temperature , time & with wide range machineries.
3. Environmentally friendly
4. Decomposition products are oxygen & water
5. Compatible with most dyes & optical brightening agent (OBA)
6. Excellent storage stability
7. Produces a stable white fiber with good absorbency
8. Allow saving by combining stages such as desizing &scouring of over 50% in labour, water & energy cost.
9. Small amounts of impurities can acts as stabilizer.
10. Give versatile processing (batch\ continuous, hot\cold, rapid\ long dwell).

pH < 10 – no HOO-
pH - 10-11 -- Low to moderate HOO-
pH >11 -- Moderate to high HOO-

HOO- is very important , without it bleaching is not possible,
Commercially we get H2O2 in %
35% (W/W) weight/weight
50% {W/W}
70% (W/W) – conc. Available active oxygen

Hypochloride bleaching agent:
Calcium hypochlorite or sodium hypochlorite are used a hypochlorite bleaching agent. Calcium hypochlorite\rite has cheap source of bleaching powder. It is cheap but unstable. NaOCl is stable & soluble.
Mechanism:

Ca(OCl)2 + H2O ---- Ca (OH)2 + HOCl
Hypochlorous acid
NaOCl + H2O ------- NaOH + HOCl
HOCl ----- H+ + OCL-
Hypochlorous ion
OCl - + OH -- Cellulose ----------- White cotton

pH is need about 10-11

Most disadvantages:

(AOX) – Absorbable Organic Halogen
If AOX is more pollution is more.

Scouring:
Calcium hypochlorite forms CaCO3 with CO2 & water. To remove this acid is used. Which is known as scouring.

Mechanism:
Ca(OCl)2 + H2O +CO2 --- CaCO3 + HOCl
CaCO3 + 2HCl ---- CaCl2 + H2O + CO2
CaCO3 + H2SO4 --- CaSO4 + CO2 + H2O

As CaCl2 is more soluble in water then CaSO4. HCl is preferable.

Antichlor treatment :
Antichlor, process is required
To destroying active chlorine bleach liquor
To remove chloramines from textile

R – NH2 + NaOCl ---- R – NHCl + NaOH
Chloramines

Disadvantage of chloramines:
Corrosive & un hygienic yellowing of fiber
To remove the chloramines & Cl2 fabric is treated with reduce in agent for polyamide & peroxide for cellulosic fibers. This process of removal known as Antichlor treatment.

NaOCl + H2O2 -------- NaCl + H2O + O2
R – NHCl + H2O2 --- R – NH2 + HCl + O2

Test for bleaching:

1. Whiteness Index (WI) : AATCC – 110
2. Physical or chemical damage :

Fluidity test

1. Whiteness is get by reflectance value 72-80 acceptable for cotton

The reflectance values of well bleached samples are:
Cotton – polyester/cotton 80 – 90 %
Wool 50 – 60 %
Linen 60 – 80 %

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Fibre dyeing machine

2013-05-02T21:54:00.000+06:00

Machine for Continuous loose cotton fibre dyeing:

Feature:
-When large amount of loose cotton fibre is to be dyed in standared dyeing shade, continuous dyeing may be carried out.
-The output of the machine can be can be as high as 2000lb per hour
-Vat and sulpher dyes are dyed on cotton fibre in theis dyeing machine.
-The cleaning of the performed drum and the conveyors takes about a weeks time.

Working principle:
-In the machine the dye liquor is kept stationary while the cotton is moved in the liquor

-Cotton fibre are feed in the form of laps, 2 inch thick and 36 inch wide, which are uniformly packed. The lap is passed through a squeeze roller are feed into the machine by conveyor belt.

-The method of circulation of dye liquor through the conveyor and the cotton lap is shown as figure. A perforated cast iron cylinder(A) with closed end plates is made to rotate at the conveyor speed. Its axis is provided by a stationary hollow pipe(B). which is connected to a suction pipe(C). Two conveyors E1 and E2. Both being continuous are made to move contact with each other between two sets of squeezing rollers F1 and F2 with suitable guide rollers G1 and G2. Owing to the cut off (D), the pump only sucks through the lower half of the cylinder.

-There are five units, wetting, dyeing, cold wash, hot wash, drying with this type of cylinder and every unit has a definite liquor.

-Every unit has may has a guide roller, two sets squeezing rollers. Five such unit may be connected in series, with one common conveyer as the lower conveyer and five individual upper conveyor.

-Different options are carried out in this those five units and finally the lap is fed to crightom opener, where the lap is disintegrated into loose fibre.

Silk Fibre Dyeing

2012-12-04T02:21:00.000+06:00

Dyeing of silk fiber

Like wool, silk is a protein fibre and can therefore be dyed using the same methods as for wool dyeing (Õ Dyeing of wool). As silk is considerably more resistant to alkali than wool, dyeing processes which are carried out under weakly alkaline conditions are also used. In this regard, it must also be borne in mind that under alkaline conditions, high temperatures and conditions of high mechanical stress at the same time, individual fibres (fibrils) can split away from the silk filaments giving the material a fluffy and rough appearance. Compared to wool, silk also has a distinctly lower affinity because of its weaker acid binding capacity. Additional factors influencing the affinity of silk are its origin, extent of degumming, the yarn quality (tram silk, organize) and whether the silk has been weighted or not. In general, it can be said that under the same dyeing machine conditions, level dyeing are less problematic to produce on silk than on wool. The dyeing temperature should not exceed a maximum of 80°C since temperatures at the boil have a negative influence on the luster and handle of silk.

Silk is dyed in all its commercial forms but is best dyed in the form of hanks (yarn) and piece goods. In principle, all the well-known types of dyeing machine can be used if they have been suitably modified to take into account the sensitivity of silk to tension and mechanical stress.

The most important types of dyeing machine for silk fibre dyeing include:

Hank dyeing machines: no hank deformation (with double stick systems), no filament splitting, level dyeings obtainable provided the rate of liquor circulation is adequate;

Spray type dyeing machines for hank yarn: good liquor circulation and therefore hardly any leveling problems, hank deformation and filament splitting is possible; particularly suitable for high-twist and folded yarns;

Package dyeing machines for cross-wound packages: short liquor ratio, no levelling problems with adequate liquor circulation, no filament splitting, uniform winding of packages important because of the risk of channeling;

Star frame dyeing machine: suitable for all types of woven silk fabrics, no chafe marks, low productivity, high energy and water consumption (liquor ratio 100–300:1);

Winch dyeing machine: good levelness is possible, high productivity, average liquor ratio, high risk of chafe marks,

Jigger dyeing machine: high productivity possible, extremely short Dyeing of polyester/polyester copolymer liquor ratio, risk of moiré formation, good leveling resp. slow-exhausting dyes are an advantage here;

Jet-dyeing machines: good levelness, high productivity, short to medium liquor ratio, especially suitable for jersey and crêpe fabrics (due to the virtual absence of fabric tension), possibility of chafe marks;

Beam dyeing machines: good to excellent levelness, short liquor ratio 10–20 : 1, no chafe marks, especially suitable for heavy and smooth silk qualities, risk of moiré formation.

Tab.: Fields of application, advantages and disadvantages and fastness properties of various dye classes suitable for dyeing silk.

Practically all classes of dye can be used for colouring silk (see Table). There is hardly any other textile fibre for which this is possible. Nowadays, silk fibre is mainly dyed with direct, acid, metal-complex or reactive dyes.

Metal-complex and acid dyes for silk: from the dye classes listed in the Table the 1: 2 metal-complex and acid dyes are the most important in practice. Apart from a few exceptions in the acid dye range, they can all be applied from a weakly acidic bath (Fig. 1) and exhibit good levelling properties. By careful selection, all fashion shades, including those specific to silk, can be dyed although, from time to time, the colour fastness has to take second place. Thus, for the brilliant shades, red, blue, turquoise and green, often only moderate light fastness ratings and, in deep shades, only moderate wet fastness ratings are achieved (e.g. colour fastness to water severe, alkaline perspiration and washing at 40°C).

Fig. 1: Method and dyeing recipes for dyeing silk with metal complex and acid dyes (Ciba-Geigy). - - pale shades; dark shades

Reactive dyes for silk: These are being used to an increasing extent (Fig. 2). They are characterised by their brilliance, high degree of fixation, high light fastness and outstanding wet fastness properties. In general, they are not very substantive although differences exist between the individual types. Consequently, the aim should be to use the shortest possible liquor ratios for these dyes. Dyeing is carried out first of all in a neutral bath with the addition of sodium sulphate at tempera tures of 60–70°C, with the exception of black dyeing which are dyed at 90°C. Only in the last 15–20 min. at the end temperature is an addition of sodium carbonate made to adjust the pH of the dyebath to 8–8.5 for dye fixation. After rinsing, the dyeing must still be soaped in order to remove the unfixed dye which is not covalently bound to the substrate (source: Flensberg and Hammers).

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Polyester and natural fibre dyeing | Blebds Dye

2012-12-04T02:14:00.000+06:00

Dyeing of polyester fibres

-->

Polyester fibres are hydrophobic, have a very low swelling capacity and, with the exception of copolymer fibres, have no reactive groups and no affinity for water-soluble dyes. Dye accessibility must be achieved by the addition of carriers or the use of high temperatures (Õ High-temperature dyeing). The heat-setting of polyester before dyeing has a considerable influence on dye affinity, especially in exhaust dyeing with carriers. Oligomers also have an effect on the dyeing results. Exhaust processes are of importance for disperse dyes and naphthol-based diazo combinations. In continuous dyeing processes, pigments are used for pastel shades whilst vat and vat leuco ester dyes are likewise only used for pale shades. In general, disperse dyes are applied by the heat-set thermofixation process. For dyeing polyester loose fibre and card sliver, HT circulating liquor dyeing machines with the material press-packed into cages are used; card sliver can also be dyed by continuous methods. Smooth yarns in the form of cross wound packages and textured yarns in the form of cross-wound muffs loaded on to spindles are likewise dyed in HT circulating liquor dyeing machines. For woven and knitted fabrics, HT winches or HT jet and HT beam dyeing machines are available. Thermosol plants are used for the continuous dyeing of woven fabrics. Polyester copolymer fibres (modified polyester) contain anionic groups and can therefore be dyed with cationic dyes as well. Optimal batchwise polyester dyeing processes are characterised by coordinated temperature control and liquor circulation. In this connection, it should be noted that an increased rate of liquor circulation leads to improved levelness. As a result, the critical rate of dyeing increases in proprtion to the rate of liquor circulation. However, an increased rate of liquor circulation through the textile material only leads to optimum levelness up to a certain limit. Moreover, with increased liquor throughput, increasingly unlevel results are observed. The conditions for this minimum unlevelness are to a large extent independent of the rate of heating.

Dyeing of acrylic polyester blends Single-bath and two-bath exhaust processes are used with disperse dyes for the polyester and cationic dyes for the acrylic fibres.

Dyeing of cotton or regenerated cellulose and polyester blends

These mixtures occupy a very large share of the market, and the blend ratio is nearly always 67% polyester and 33% cotton; with regenerated cellulose, the ratio is often 70 : 30 in many cases.

Disperse dyes are almost exclusively used for the polyester component and reactive, vat, vat leuco ester or sulphur dyes for the cellulosic component. Direct dyes are used only occasionally. In most cases, a tone-in-tone dyeing of both types of fibre is required, for which special ranges of pre-mixed dyes are available from different manufacturers. The formulation of these mixed dyes has been fine-tuned so that both fibre components can be dyed to the same shade by exhaust as well as continuous dyeing methods.

I. Exhaust method: for the dyeing of yarns this process is only of secondary importance. Dyeing is carried out on cross-wound yarn packages or warp beams by the single-bath single-stage or single-bath two-stage process. Direct dyes can be used for cotton in the single-bath single-stage process provided they have sufficient resistance to carriers. With the single-bath two stage process, the cellulosic component is dyed first in the case of reactive dyes whereas the polyester component is dyed first in the case of vat dyes. In two-bath processes, the polyester is likewise dyed first followed by the cellulose with appropriate dyes for each fibre.

Where the cellulosic fibres are too heavily stained with the disperse dyes, an intermediate reduction clear with dithionite must be given (as well as for processes involving the use of carriers in order to remove carrier residues). The exhaust method is also used for light weight woven fabrics as well as knitgoods. Dyeing equipment as for 100% polyester fabrics.

II. Continuous method: this process is used for all other qualities and offers numerous possibilities. Intermediate drying is critical as a certain amount of dye migration can take place at this stage. Most of the disperse dye on the cellulose is transferred by diffusion on to the polyester component during thermofixation.

Polyester natural silk blend Dye

The polyester component is dyed first with disperse dyes in a single-bath two-stage or two-bath process, followed by an intermediate reduction clear if necessary. Finally, the silk is dyed with acid dyes.

Polyester or polyester copolymer (cationic dyeable) Dyeing

This mixture is only seldom encountered. Disperse dyes are used for the polyester and cationic dyes for the modified polyester fibres in a single-bath two-stage or a two-bath process. For continuous dyeings, the modified polyester fibres are pre-dyed with cationic dyes on the pad-steam range, then disperse and vat dyes are applied on the padder followed by thermofixation and development on the pad-steam range. In the knitgoods sector, two-colour effects are produced as well as solid shades. Acid-modified polyester with a high rate of dyeing: carrier-free dyeing at the boil with suitable disperse and cationic dyes.

Dyeing of wool and polyester blends

The blend ratio is mainly 55% polyester and 45% wool. For the highest quality it is recommended to dye each fibre separately.

Optimum fibre protection is not possible. As there is nothing to be gained by two-bath dyeing, it has been substituted by single-bath processes. A major disadvantage in dyeing this fibre blend is the fact that disperse dyes result in a more or less pronounced staining of the wool component and this staining has no colour fastness to speak of. A strict selection of those dyes which exhibit the least possible staining on wool is therefore necessary. Dyeing is carried out by the exhaust process at 105–107°C if possible, and with reduced amounts of carrier. Disperse dyes are used for the polyester and 1 : 2 metal-complex dyes for the wool. Pre-mixed dyes are also available from a few manufacturers.

Dyeing of polyvinylchloride (PVC)

fibres Polyvinylchlorid fibres are mainly dyed with disperse dyes. Cationic or metal-complex dyes are also frequently used. Pigments are seldom and naphthol dyes only occasionally used. The dyes must be carefully selected and, depending on the type of fibre, are dyed with or without the addition of a swelling agent (carrier) or dyeing is carried out under HT conditions, whereby polyvinylchloride filament yarns have a considerably lower dye affinity than polyvinylchloride staple fibres.

Dyeing of regenerated cellulose fibres

(Viscose, cupro fibres, high wet modulus /polynosic fibres). In principle, all dyes used for dyeing cotton are suitable for dyeing regenerated cellulose fibres (Õ Dyeing of cotton). The most important dyes are substantive and reactive dyes, with preference being given to hot dyeing types. The affinities of fibres produced by various manufacturers differ and can even vary from batch to batch from the same manufacturer. Textiles made from these materials are sensitive to pressure, friction and tension and this must be taken into account during the dyeing process. A well-known fault is the streaky appearance of woven or knitted fabrics due to slight variations in fibre manufacture. This streakiness can be avoided to some extent by selection of suitable dyes. The pronounced swelling properties of these fibres must be taken into account from the dyeing kinetics point of view (exothermic swelling) so that a fibre specific processing sequence is necessary.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge.

-->

Dyeing of jute, flex, modacrylic, polyamide fibres and their blends

2012-12-04T02:08:00.000+06:00

Dyeing of hemp fibre

This is of no significance as the products manufactured from hemp fibre are almost exclusively used for technical textile purposes (fire-engine hoses and belts, etc.).

Dyeing of hat trimmings of straw, panama and Sisal for hemp

1. For dyeing straw: acid and 1: 1 metal-complex dyes

2. For dyeing panama: disperse and cationic dyes

3. For dyeing sisal: direct, acid, and 1: 1 and 1: 2 metal complex dyes.

Iridescent effects by piece-dyeing

A prerequisite is that the warp and the weft have different affinities – usually acetate/triacetate or triacetate mixtures. Single-bath dyeing can be carried out with direct and disperse dyes, usually giving contrasting shades.

Jute fibre Dyeing

The jute fibre dyeing is similar like cotton fibre dyeing. The high proportion of non-cellulosic material gives jute an affinity for cationic dyes (mordant unnecessary) and acid dyes. Unlike cotton, jute is sensitive to alkalis. The light fastness of jute dyeings is poorer than on cotton.

Dyeing of leather(goods) Because of the wool like chemical nature of leather, appropriately modified dyeing methods are used depending on the type of tanning process. The usual treatment with aqueous dye solutions given to new articles (by brushing on or dipping) has only a limited application for second-hand goods (garment dyeing). For expediency, dyeing is carried out using tried and tested commercially available

Dyeing of linen (flax) fibre

In principle, dyeing is carried out using all the dye classes that are suitable for cotton (Õ Dyeing of cotton). Dye penetration is generally more difficult, especially in the case of vat dyes. The best penetration and levelness is achieved with reactive dyes.

Loose material (loose stock, loose fibre) Dyeing,
Advantages: Any unlevelness in dyeing is evened out during the subsequent spinning process, large quantities can be produced to one shade by blending several batches and a low liquor ratio is possible in dyeing.

Disadvantages: satisfactory processing in spinning isusually only achieved through the application of spinning oils and dressings. The spinning of coloured yarns demands total separation of different shades in spinning and laborious cleaning is necessary when changing colours. Unavoidable co-processing of short fibres and dyeable impurities. Continuous dyeing can be carried out by a pad steam process (e.g. the Smith Piston Pad Dyeing Machine).

Dyeing of modacrylic (acid dyeable) and wool fibre blends

This modacrylic and woo fibre blend can only be dyed in solid shades with dyeing difficulty because of the considerably higher affinity of the acid dyes for the wool fibre component. The best possible solid shade dyeings are achieved with the Chem Acryl process and other process variants (manufacturer: Chemstrand Corp., Decatur, Alabama/USA).

An addition of the following dyeing auxiliaries is necessary: cationic and non-ionic dyeing assistants which retard the exhaustion of selected acid dyes and bring about a satisfactory balance between the dye on both fibre components in the sulphuric acid bath.

Modacrylic fibre dye

Dyeing of ombré or shadow effects, shadow dyeing on one and the same hank, e.g. by hand using square or U-section rods. Firstly, the palest colour is dyed from a full vat dye then, after dropping a little of the dyebath, a dye addition is made and a somewhat darker shade is dyed – this procedure is repeated with the increase in depth of shade becoming less and less as ever smaller additions of dye are made. In this way, light to dark shadow effects of the same colour, i.e. so-called tonal gradations, are obtained. Ombré variations are produced by using different dyes. Excellent ombré dyeing are obtained on thoroughly pretreated dry goods by employing a material-specific dye selection (hot and cold dyeing types and no pre-mixed dyes if possible) as well as the absence of wetting agent (undesired upward migration of dye) with, if necessary, controlled additions of salt and temperature regulation. The most efficient results are obtained on the hank dyeing machine where good dye penetration is achieved by raising and lowering the entire yarn carrier assembly. With increasing depth of shade, the hanks are lowered to a lesser and lesser extent into the dye liquor which is correspondingly increased in strength with additions of dye. By dropping the liquor level approx. 5 cm for each individual shade a reduced depth of immersion is achieved.

After reaching half the original bath volume, the yarn carrier assembly is lowered to a reduced depth. For piece goods, dyeing on the star frame is very practical (star dyeing machine) by continually raising and lowering the frame with the aid of a beam assembly (a cable running over a boom-arm); this method has proved particularly suitable for sensitive qualities (e.g. pure silk).

Polyamide fibre dye

Various dye classes of dye are suitable for dyeing polyamide fibres, and dye selection is based on the form of the material, the fastness requirements and the dyeing properties.

I. Disperse dyes: these dyes have good affinity and levelling properties. Affinity differences in the fibre are easily levelled out. The wet fastness properties of medium to deep dyeings are unsatisfactory.

II. Acid dyes: the most widely used class of dyes for dyeing polyamide fibres. They offer a wide colour gamut and good fastness properties, especially following an aftertreatment with products to improve the wet fastness. For combination dyeings it is essential to use dyes with similar rates of exhaustion. The selected dyes must not exhibit any blocking action. In order to cover up affinity differences in the material, anionic leveling agents, which possess an affinity for the fibre, are used in the dyebath.

III. Metal-complex dyes: these dyes have good light and wet fastness properties. Their use is limited (except for black) since differences in the polyamide material cannot be levelled out in most cases. Fastness properties can be improved with a tannin/tartar emetic (potassium antimony(III) tartrate) aftertreatment. IV. Metal-containing disperse dyes: the fastnesses properties are the same as those of the metal-complex dyes. Material-dependent affinity differences are largely covered in dark shades. Improved fastness properties are possible with a tannin/(tartar emetic) (potassium antimony(III) tartrate) aftertreatment.

V. Reactive disperse dyes: dyeable as disperse dyes; chemical bonding with the fibre takes place following an alkaline aftertreatment thereby giving good wet fastness properties.

VI. Direct dyes: the selection is limited: used chiefly for reasons of shade and price.

VII. Naphthol dyes: of no importance.

VIII. Chrome dyes: of interest only for black shades (applied by the so-called Metachrome process in which dye and mordant are applied simultaneously from a single bath).

IX. Reactive dyes: the light fastness of these dyes varies appreciably on polyamide. Wet fastness properties are good. Any affinity differences that may arise are not covered in all cases. Combination dyeings are only possible to a limited extent. The build-up is also limited.

X. Logwood black: This dye is of interest for reasons of shade and fastness but, the method of dyeing is very involved.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Glass fibre or filament dyeing

2012-12-03T01:20:00.000+06:00

Glass fibre is the most important invention in the modern textile age. Glass fibre is special types of fibre that used for special purpose. This type of sophisticated fibres are used for communication, data transfer, or decorative purpose. Glass fibres able to transfer light, ray and radiation inside its subtle hole. Dyeing of glass fibre filaments, fabrics or fabric is not so easy. In this case, it must be taken into consideration that, under normal circumstances, there is no affinity between glass fibre and dye and that no penetration of the dye into the glass fibre is possible, only surface dyeing or coloration is possible. The following overview includes patented processes of glass fibre dyeing or coloration which must be regarded as being legally protected:

I. Fused mass coloration or dyeing: using coloured metal oxides yielding weak dyes only as the colour intensity inevitably decreases with the cross section of the filament.

II. Dyeing of activated surfaces of glass fibre: predominantly older processes of relatively little practical importance and usually yielding weak coloration, deficient in crocking fastness and, almost without exception, having a tendency to damage the fibres surface.

III. Direct dyeing methods of glass fibre: without pre-treatment, using conventional dyeing techniques and, in this case, yielding surface coloration or dyeing which is barely acceptable. Methods involving the deposition of water-insoluble dyes are exceptions to this but usually only weak coloration can be achieved, e.g., when using sulphur or vat dyes.

IV. Pre-mordanting dyeing methods: a) metal-salt process gives strong colours in some cases but almost always with insufficient crocking fastness, b) cation active process gives very strong colorations which, with the right choice of dye, can have good fastness properties against water and light but only moderate crocking fastness.

V. Bonding-agent dyeing methods: coating with dyeable or dyed films: a) pigment dyeing methods are the most elegant and simplest to use. Pale to medium shades are possible with maximum light, water and crocking fastness (with the right choice of dye) while the properties of the dark colours (marine and black) are frequently much worse. The principle consists of fixing the pigment using synthetic resins. b) Other bonding-agent dyeing methods are to some extent still very inconvenient and unsatisfactory (especially with regard to crocking fastness). Exception: Õ Corona discharge process with good overall fastness but crocking fastness and grease resistance are not completely satisfactory. No dark full shades obtainable.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Dyeing of cotton, acetate, regenerated cellulose, polyamide fibre and their blands

2012-12-02T21:56:00.001+06:00

Dyeing of coir
Method as for jute – dyeing is usually carried out using direct or acid dyes under mildly acidic conditions (cationic dyes have inadequate light fastness). Coir is also dyed before spinning using oilsoluble dyes in the spinning oil.

Cotton fibre dyeing
The affinity of cotton for dye varies according to its history. The adsorption capabilities of cotton are increased by caustic solutions or mercerization.
There is a huge selection of dyestuffs available for cotton: substantive dyes, vat dyes, sulphur dyes, leuco-ester vat dyes, reactive dyes, naphthol dyes and phthalocyanine dyes. Of less importance are pigment dyes and chrome dyes. Cationic, aniline black and mineral khaki dyes do not have any significant application.
There is a clear trend towards dye groups with high fastness properties. A continual problem for the finisher is the proportion of immature or dead fibres (dead cotton) which give rise to the appearance of bright spots in coloured fabrics. These faults are significantly reduced by treating the fibre with caustic solution or by mercerization.

Dyeing of cotton and acetate or cotton and triacetate fibre blends,
I. Acetate or triacetate white, cotton coloured: dyeing is usually carried out with selected substantive dyes which reserve the acetate and triacetate. The dyeing temperature must not exceed a maximum of 80°C with acetate since staining of the fibre occurs at the boil.
Acetate which has been scoured at too high a temperature and which is partially saponified will no longer be reserved. Even for acetate and triacetate which have been delustered in spinning a good reserve is more difficult to obtain.
II. Cotton white, acetate or triacetate coloured: this is a considerably less favourable combination as disperse dyes stain the cotton to a greater or lesser extent. An afterclear treatment is necessary with sodium dithionite, sodium hypochlorite or potassium permanganate.
III. Cotton/acetate or triacetate dyed tone-in-tone: usually carried out by single-bath dyeing with substantive and disperse dyes. Two-bath method : a) the acetate or triacetate is dyed with diazotizable disperse dyes; b) then using a fresh bath for the acetate or triacetate, the cotton is filled in with substantive dyes. All the above variants are carried out by exhaust dyeing; pad dyeing is only used in exceptional cases.

Ccotton and regenerated cellulose fibre blend dyeing
Cotton/regenerated cellulose blends are dyed using the same classes of dyes as for cotton. The achievement of tone-in-tone uniformity between cotton and regenerated fibres is problematic due to the greater dye affinity of the latter (greatest with cupro fibres and weakest with high-wet-modulus fibres). The dyeing method, especially for substantive dyes, must be appropriately adapted with regard to salt additions and temperature, i.e. dyeing must be carried out with less salt or no salt at all and at lower temperatures. If necessary, dyeing is started at the boil with a portion of the dye, and the rest is added to the bath after cooling down.
Padding methods are more suitable than exhaust methods for vat, leuco-vat ester and naphthol dyes. Causticizing before dyeing improves the affinity of the cotton. However, despite all these measures, tone-in-tone dyeing is not achievable with dark shades.

Cotton and regenerated cellulose with polyamide blends
Tone-in tone dyeings with a single class of dyes are only achieved with great difficulty. In most cases, one or other of the fibre components will have to be filled in with specifically appropriate dyes.

Exhaust methods: selected substantive and vat dyes (for which the semi-pigmentation process is particularly suitable) are capable of producing tone-in-tone dyeing in pale shades by using appropriate dyeing methods. A single-bath method with substantive and metal-containing disperse dyes can be used here. For dark shades, the polyamide must be dyed first with metal-containing disperse dyes followed by the cellulose in the same bath with substantive dyes. A single bath two-stage method may also be used with selected reactive dyes. In this case, either the cellulose is dyed first under alkaline conditions followed, after acidifying the bath, by the polyamide or, the polyamide is dyed first at pH 5 and followed, after neutralization, by the cellulose. Two-bath two-stage method: metal-containing disperse or 1 : 2 metal complex and reactive or vat dyes. Pad dyeing: pigments may be used for pastel shades. Where high fastness is required, each fibre component must be dyed separately by the methods customarily used for it. For the polyamide component, metal-containing disperse dyes are by far the most important, and vat, sulphur or reactive dyes for the cellulosic components. Selected acid dyes may be applied together with vat dyes by a single-stage method, e.g.: both classes of dye are padded together, followed by acid steaming, drying, thermofixation, padding with caustic/sodium dithionite, then steaming, oxidizing and washing. Phthalocyanine dyes may be employed for turquoise shades.

Dyeing of flammé effects
This process is mainly carried out on hank yarns. This is effectively done by tying off the hanks individually at the sites where they are to be dyed in one particular colour first. Dyeing is then carried out in the customary way with the liquor just reaching the ties. The hanks are withdrawn and thoroughly rinsed by immediately spraying them with cold water in an upward direction. The ties are undone (after an intermediate drying step if necessary), rehung and tied again for the next dyeing with another dye, as already described, and rinsed down again etc. until the whole hank is dyed in the various colours desired. Two, three, four or more different colours may be involved and these may be interspersed with non-dyed areas or the colours may be adjacent to each other or even overlapping.

Instead of obtaining flame effects on non-dyed yarn, hanks can be pre-dyed in a certain shade and then dyed in certain places as described above. Instead of using the technique described above, dyeing is also carried out using a pulley lifting system without tying off the hanks. Õ Dyeing of ombré or shaded effects.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Acetate, acrylic fibre and their blend dyeing

2012-12-02T21:48:00.000+06:00

Dyeing of acetate fibres

(Dyeing of triacetate fibres). Disperse dyes are predominantly used both for acetate and triacetate fibres and are mainly used in exhaustion processes. As is the case for polyesters, triacetate must be dyed either with the addition of carriers or under HT conditions. In the case of acetate, selected cationic and naphthol-based dyestuffs can also be considered. There are only limited possibilities for using the padding process as the thermosol dyeing process cannot be used for acetate fibres and can only be used for triacetate fibres when lighter shades are being applied.

Acetate, wool, cotton fibre union dye:
I. Acetate white, union coloured: single-bath dyeing with suitable neutral-dyeing acid, direct or union (mixed fibre) dyes. Two-bath method, this is possible by pre-dyeing the cellulosic fibres with direct dyes at approx. 70°C, rinsing and filling in the wool with acid dyes from an acidic bath.
II. Acetate coloured, union white: it is questionable whether a satisfactory union reserve is possible as even the most suitable acetate dyes cause staining of the wool.
III. Acetate and union in two colours: single-bath method using a combination of dyes according to I. +
II. (if necessary II. + union dyes) in a neutral sodium sulphate bath (Glauber’s salt). Two-bath method by pre-dyeing the acetate, filling in the union and rinsing.
IV. Acetate, union in three colours: single-bath method using dyes which reserve the other fibres completely by dyeing according to dyeing methods I.–II. In a neutral bath. Two-bath method as single-bath with filling in of the vegetable fibre.
V. All fibres dyed the same colour: dye with a combination of direct-dyeing union dyes and acetate dyes.

Dyeing of acrylic fibres
These fibres can exhibit very different dye affinities. Acrylic staple fibres are more easily dyed and in greater depths than filaments. The dyeing of acrylic fibres has proved difficult to the extent that whilst polyacrylonitrile fibres only begin to exhibit adequate affinity at relatively high temperatures of 70–85°C (depending on origin), the rate of dyeing is virtually doubled with an increase in temperature of around 3–4°C. Moreover, only a very low degree of migration takes place at the usual dyeing temperatures, i.e. as a rule, uneven dyeings cannot be levelled out adequately.
I. Cationic dyes: suitable for pale to dark shades; pale to medium depth shades are usually dyed using cationic or anionic retarders at the boil. The HT process is only suitable for acrylic filaments and fibres of low affinity. Continuous methods are used for loose stock, tow and combed sliver as well as, to some extent, acrylic/ cellulosic blends (fixation medium = saturated steam). The thermosol process is of practically no significance (levelling problems, unsatisfactory reproducibility and effect on handle).
II. Disperse dyes: the material is introduced into the dye bath at 70°C, brought to the boil quickly and dyed at the boil for 1 h. The thermosol and pad-steam processes are of secondary importance.

Acrylic and wool fibre blend dye
Dyeing methods: single-bath single-stage, single-bath two-stage or a two-bath process. Cationic dyes are used to dye the acrylic component and acid, 1 : 2 metal-complex and reactive dyes are used to dye the wool component.
When dyeing acrylic fibres and wool, the cationic dyes stain the wool component first. As the boil is approached during dyeing, they transfer slowly from the wool on to the acrylic fibre and if the proportion of wool is at least 30%, retarders are not necessary. The transfer of cationic dyes from the wool is dependent on the quantity of dye, dyeing time, dyeing temperature and the pH. In the case of deep shades, a dyeing time of 45–60 min. at the boil is necessary to achieve a good wool reserve. With falling pH, the wool reserve increases. A good wool reserve is a prerequisite for the achievement of optimum wet and light fastness properties.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Dyeing machines

2012-12-02T00:56:00.001+06:00

Dyeing machine is Device in which the textile material which is to be dyed (as distinct from Dyeing machine, circulating) is agitated in more-or-less stationary liquor – for example: padder, rope-winch vat, jigger, continuous dyeing machine, paddle dyeing machine, star frame and, among others, modern processors such as the pad-jigger, pad-roll, pad-steam, pad-wet and pad-winch processes. The dyeing machines which are in use today for batch dyeing consist of the following basic elements:

– The vat as the stationary zone,

– The pump for circulating the liquor,

– The mechanical elements for controlling the liquor(pipes and valves),

– The heat exchanger (heating unit),

– The mechanical elements for transporting the material and circulating the liquor, such as guide bars, reversing winches, transporter winches, material carriers and immersion wetting-out apparatus.

Fig. 1: Types of flow between fabric and liquor

Dye movement in the solution is brought about by convection whilst liquor movement is brought about by agitation or circulation pumps. High temperatures and liquor exchange accelerate this process so that the overall dyeing speed is not adversely affected by diffusion.

Diffusion is the dynamic dispersion of dye particles caused by the system’s tendency towards a state of equal concentration of particles throughout the liquor irrespective of the liquor movement. Optimum flow at the interface and through the textile material to produce the highest possible degree of levelness depends on the liquor-exchange system of the dyeing machine in question.

High flow rates accelerate the dye absorption, the various machine designs produce different types of Different machines or apparatus are used according to the material being dyed. There are dyeing machines in which the liquor is stationary and the material is moving and dyeing machines in which the liquor is moving and the material is stationary (Fig. 2).

Dyeing is carried out according to the makeup of the material to be dyed:

Dyeing is carried out according to the makeup of the material to be dyed:

I. Dope-dyed synthetic fibres: In synthetic fibre production the dye pigment (insoluble but finely divided dyestuff) is added to the spinning solution so that a coloured fibre is produced when extruded through the spinneret.

II. Loose stock dyeing: Loose stocks can be dyed by batch (non-continuous or continuous methods). In the case of batch dyeing, the fibre material is packed in a perforated vessel through which the dye liquor is forced. Coloration is not always evenly distributed but this is immaterial as the loose fibres are subsequently dispersed in the spinning mill and evenly mixed so that the colour ultimately appears to be uniform. In the case of continuous dyeing, dye solution is continuously applied to the stock on a padder and the dye fixed in a steam ager. The material is then washed and dried. Stock of different colours can be used for colour blending.

III. Sliver dyeing (slubbing dyeing): top or combed sliver consists of a continuous sliver from which the short fibres have been combed out on a combing machine. This sliver can be, for example, dyed in ball form.

There are several areas where slubbing dyed material can be used in coloured wool yarn production.

a) Sold shade yarn: the essential advantage of dyeing combed sliver is the high fastness achieved. However, it is only economically viable where large batches are involved.

b) Melange yarn: in a melange yarn specified percentages of combed slivers are dyed in different colours. These different-coloured slivers are then mixed together at the drawing stage and spun.

c) Vigoureux yarns: In this case, printing paste is applied at different intervals by means of a printing roller and fixed. When the combed sliver is drafted during the spinning cycle, the coloured and non-coloured areas intermix so as to create the characteristic melange yarn. In the vigoureux printing process, the individual fibres are striped zebra fashion. The patterning in the finished product resulting from this process is so small that the eye can only perceive a mixed colour. For example, from a mixture of black and white stripes the resulting colour is grey. In melange products, on the other hand, the eye is still able to identify the individual black and white fibres.

IV. Yarn dyeing: The following different machines are used for dyeing yarns:

a) Hank dyeing machines: the yarn is wound into hanks, the individual hanks laid on a roller conveyor and the hanks passed through the dyebath on the rollers.

b) Spray-dyeing: in this case, hanks are laid over a perforated tube out of which the dye liquor flows. The hanks are placed at regular intervals so that dyeing is uniform. The amount of dye liquor required for this machine is significantly less than for a).

c) Pack cage: the hanks are placed in a cage and dyed in a similar way to the loose stock dyeing process.

d) Assembling columns of cross-wound packages and subjecting these to a stream of dye liquor in an autoclave.

V. Piece dyeing: there is a whole series of machines which can be used for dyeing fabrics. Modern dyeing machines operate via mechanical systems using program controllers or microprocessors, the whole dyeing process being controlled by a program.

a) Winch vat: these machines are suitable for qualities which are not subject to running cracks. The cloth is passed through the dye liquor at boiling point as a continuous rope with a rotating winch providing the traction. Temperatures can be as high as 100°C (Fig. 3).

Fig. 4: “Krantz” overflow machine for fabrics in rope form.

1 = dwell chamber; 2 = liquor-exchange pipe; 4 = circulation pump; 5 = liquor extraction; 6 = heat exchanger; 7 = liquor injection; 8 = wetting-out device; 9 = wetted-out fabric; 10 = return winch.

b) Jet dyeing machine or Overflow machine: the overflow machine has been especially designed for dyeing fabric which is sensitive to tensile stress. These fabrics can be dyed using this apparatus with the minimum possible tensile loading. In this type of machine (Fig. 4), both the fabric and the liquor are in motion. The construction can be either vertical or horizontal. In jet dyeing machines, the liquor is caused to move by jets from nozzles, thus causing the fabric to move at the same time. In most cases, the fabric is also driven by means of a winch.

Dyeing machines, circulating liquor type:

These are differentiated into package systems, Hussong type systems and spindle-and-separator systems. The principles differ according to working methods: stationary liquor - moving material (dye machines: padder, winch vat, jigger, roller box and hank-dyeing machine); stationary material - moving liquor (less significance, particularly common for loose stock and bulk dyeing in, for example, garment dyeing and hat dyeing; garment dyeing machines and paddle-dyeing machines). Examples of these are:

a) Cheese dyeing machine: the packages are on perforated plastic tubes which are stacked on perforated spindles and then put into a sealed vessel (Fig. 5). In this vessel the dye liquor can be forced through the packages under pressure. Dyeing temperatures > 100°C are possible.

Fig. 5: Cross-wound package yarn dyeing machine.

b) HT Beam dyeing machine: In this case, dyeing is carried out at temperatures above 100°C. The fabric is wound on to a perforated cylinder and inserted into a sealed vessel (Fig. 6). The dye liquor can be pumped in an inward or outward direction through the rolled fabric.

Fig. 6: Operational cross-section of a dyeing machine for open-width piece dyeing.

1 = coupled dye beams with outward circulation; 2 = stock reservoirs with separate pump; 3 = main pump; 4 = heat exchanger.

Dyeing methods for dyeing machine

These have been the subject of continual development over the years especially because of the need to rationalize or for reasons related to color levelness and dye compatibility or because of new problems appearing with new substrates. Thus, there is a whole series of possibilities for variation such as short-liquor dyeing, foam applications, thermosol processes, jet dyeing (jet-dye machines), overflow dyeing, (overflow dyeing machines), HT dyeing processes, pad-steam dyeing processes and continuous wet-steam processes among others. In order to optimize the dyeing process, the dyeing procedure is controlled according to a program and process control systems are used o control the operations. This means that a set of measurement instruments of maximum reliability continually records certain parameters and issues appropriate commands to the valves etc. Actuators, for example, are used for speed/time control and other operational control aspects for individual forms of apparatus, machine or automatic process management and control systems. Development in the area of textile dyeing and dyestuffs and in relation to technical applications is very dynamic.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Dye class identification on fibres,

2012-12-01T03:23:00.001+06:00

Iidentification of Dye class on fibres

Dye class identification is very important test to select a relevant dye for particular fibre or fabric. All kinds dyes are not suitable for all textile fibres. For example Reactive dyes are confidently identified for natural cellulose fibres, because it is possible to associate the reactive dyes structure with the cellulose fibre structure. If the fibre material is unknown, Fibre identification should be carried out first.

Dye class identification for various fibres

The most well-known dye class identification systems on fibres are:

I. Krefeld method:

a) For cellulose fibres (cotton, silk, jute etc): dissolve fibre sample in suitable solvent, sulphur test (for sulphur-based dyes), blind vat (oxidation and cationic dyes), stripping and staining reactions (for mordant, acid, direct and diazo dyes), dimethyl formamide test (for reactive dyes), glacial acetic acid test (for vat, naphthol and phthalocyanine dyes).

b) For animal fibres (wool): paraffin test, blind vat and reoxidation (for vat and naphthol dyes), detection of metals (metal complex and chrome dyes), cold glacial acetic acid (cationic dyes), suitable solvent (reactive, acid and direct dyes).

c) For synthetic fibres: a caprolactam melt is prepared or stripping by means of glacial acetic acid carried out. The melt and the solution are mixed with ether and processed further. Dye classes which can be identified are disperse, metal complex, chrome, acid, cationic and naphthol dyes.

II. Reutlinger method:

a) For cellulosic fibres: water, wash, paraffin, pyridine, glacial acetic acid, hydrogen sulphide, chlorine, benzene tests and blind vat.

b) For animal fibres: water, wash, paraffin, glacial ace tic acid, ammonia, pyridine, benzene tests and blind vat.

c) For synthetic fibres: Acetate, Polyamide and Acrylic dyes.

III. In accordance with the AATCC guidelines for cellulosic, animal and synthetic fibres.

Dye classification:

A distinction is made between the following methods of classification:

I. Scientific classification of dyes based on their chemical structure, e.g. anthraquinone, azo dyes, etc.

II. Technical classification of dyes based on their dyeing properties, e.g. direct, acid, wool dyes, etc.

III. Commercial classification of dyes based on various aspects according to the manufacturer, e.g. according to fastness properties such as Sirius Light, Indanthren, etc. or according to the method of dyeing under collective names, e.g. Remazol = reactive dyes (Dystar), Palanil = disperse dyes (BASF), etc.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Dye application; dyeing control methods in continuous dyeing

2012-12-01T02:37:00.000+06:00

Application of dyes in continuous dyeing process:

Dyeing is very important part of readymade garments manufacturing. The proper application of fashion in textile is totally depends on the types of dyeing. The proper shade matching is depend on the proper application of dyes. In continuous dyeing the quantity of dye applied to the textile fabric can be measured indirectly from the amount of moisture (liquor) applied dyeing machine by the padder (e.g. by means of microwaves). It would be even better, however, to measure the quantity of dye applied to the running fabric by taking reflection measurements on the wet fabric shortly after it leaves the dyeing machine padder nip since in this case it would be possible to make any necessary corrections from direct readings and the short control loop. Other control possibilities opened up by reflection measurements on the wet fabric include:

1. Concentration distribution of dyes and dyes chemical auxiliaries applied from the pad liquor (side. centre, side).

2. Localized dye pick-up of dyeing liquor by tile fabric (in relation to its dry weight before padding).

3, Localized residual moisture content of tile fabric entering tile liquor and tile exchange coefficient between water and product.

It is to be understood in this case that tile directly measurable dye pick-up parameter desired does not have to be replaced by a group of dye measurement parameters which can, ill principle, be handled but which require very involved measurements (the exchange coefficient is likewise not amenable to direct measurement. However, since it is only used as a correction parameter it can be applied as a value capable of interpolation from a series of trials).

Before a decision is made to invest in an elaborate measuring system of this kind for a particular process stage, it is of course necessary to establish first of all whether or not sufficient control would be achieved by measuring the dyed result at the end of the dyeing process and only then make any necessary corrections to the two factors exercising the greatest influence on the process. i.e. the dye liquor itself and the dye liquor pick-up. Color measurement on fabrics at the point of delivery from a continuous dyeing plant with a drier is state-of-the-art technology. Measuring sensors are already available which can take reflection measurements across the full width of dyed fabrics (by means of a single traversing measuring head or 3–5 dixed measuring heads) and display from the standard. The main problem here lies in the time response of the control system rather than in the measuring sensors. Measurements of dyeing are carried out approx. 30–100 m after the point of dye application. There is consequently a long time lag, i.e. under these conditions, many metres of fabric have to pass through the dyeing plant or dyeing machine after a correction has been made to the dye pick-up before the point of change in the fabric reaches the measuring head.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Dye affinity

2012-12-01T02:34:00.001+06:00

Dye affinity is an important dyeing factor for all dyes and dyeing process. Most of the properties of a dye depend on the dye affinity and dye reactivity. In simple terms, dye affinity (also neutral affinity) is the dye absorbing capacity (of textile fibres, yarn, fabrics). It varies between wide limits depending on the state of dyebath equilibrium between the fibre and the dye in solution. A number of factors play an important role in this process, e.g. dyeing liquor ratio, dye physical and chemical characteristics (it could be organic or inorganic), additions to the dyebath (such as dye acid, organic or inorganic salts and dyeing auxiliaries), dyeing time (time from start to end of dyeing), dyeing temperature (temperature vary according to dyes and dyeing property), and the degree of purity (purity of all dyes, chemicals, acids, salts and auxiliaries), extent of drawing and degree of crystallinity (rate of crystalline region and amorphous region) of the fibre being dyed, as well as the number of dye bonding groups available in the fibre (it means the reactivity of dyes). For dye affinity- controlled dyeing processes, a temperature is selected at which diffusion proceeds at a relatively fast rate inside the dye bath . If it is assumed, as a model, that a dyebath exhaustion equilibrium is established momentarily at any one time, then the kinetics of exhaustion are given by the change in chemical equilibrium. For synthetic polyamide fibres and natureal wool fibre, the chemical equilibrium between the dye in the textile fibre (concentration CF) and the dye in the liquor (CL) can be approached by a superimposed Langmuir and Nernst distribution with the pH-dependent distribution coefficients kL and kN, and the saturation value SL. The pH dependencies are both dye and fibre-specific.

Dye affinity of wool, treatments to improve,

a) Pretreat for 1 h at the boil in a 5% inorganic potassium thiocyanate solution, rinse, dye in the presence of 20% sodium sulphate and 5% acetic acid 30%;

b) Bring the yarn to the boil in a solution of 2,5–4% solution of sodium thiosulphate or neutral sodium sulphite or sodium tetraborate, boil for 1 h, hydroextract and dry;

c) Treat the natural wool fibre for 20–30 min. in a liquor containing 1–1,5% active chlorine under weakly acidic conditions, treat in a fresh bath with 1–2 g/l sodium dithionite as an antichlor and bleach.

Dye ager is a horizontal continuous-dyeing machine for all conventional textile fabrics (including difficult qualities such as cotton velvet and lining fabrics) with all classes of dye, by the pad-steam process and the wet-in-wet process of vat dyeing voluminous fabrics in which dye is applied on a preceding padder and the reducing agent padded on directly before the ager entry using a special applicator unit. A high degree of reproducibility is achieved by the ager.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Dye acid

2012-12-01T02:26:00.000+06:00

Most of the dyes are complex structure organic or inorganic chemical compound. Consistence of acid inside the dye is not so important for all dyes. But some of the dyes are show different attitude when associate with the organic or inorganic acid solution inside dyebath of dyeing machine. These are chemical organic acid consisting of the hydrophobic dye residue and the hydrophilic auxochrome groups of dyes. The latter are mainly organic sulphonic acid (–SO3H) and/or carboxyl (–COOH) or hydroxyl groups (–OH) which, with their acid character and negative charge, make the dye residue function as a dye acid and become a dye ion inside the dye solution. Free dye acids exist, for example, in the acid dye range, either in the commercial form itself or they are formed by the addition of acid in an acidic dyebath:

chemical construction of dye acid

he dye acid formed during the vatting of vat dyes are known as Vat acids. Due to their ionic behavior in aqueous solution, formation of the dye acid and their alkali salts ( Dye salts) occurs in contrast to Õ Colour bases, i.e. the main group contained in cationic dyes ( Dye ions).

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Dyeability of dyestuff

2012-11-29T23:10:00.000+06:00

Dyes dyeability

Dyeability As a prerequisite for the use of textile fibres. One of their most important properties is dyeabilily. Consequently, the range of application of some synthetic fibres has been, and still is limited either because they have poor dyeability or the problem of dyeing these fibres has not yet been satisfactorily solved. For example, when 21/2 acetate fibres were first introduced. they were not successful for a long time because they could not be dyed with the known dye classes at that time, Indeed, it was only after the discovery of disperse dyes that acetate fibres gained wide acceptance. The same problem applies to polypropylene fibres although in this case, appropriate modifications have provided a partial solution. Comparable examples are the attempts to develop polyester fibres with a higher dye uptake as well as the efforts to produce a polyamide fibre with diff erential dyeing characteristics (— Differential dyeing) which has had a favourable influence on their range of application. Some textile fibres may be dyed with several technologically different dye classes capable of achieving relatively good color fastness: others. however, can be dyed with one particular dye class only (and. even then. not without difficulty in some cases).

In practice the dyeability of a textile fibre is determined by the rate of dyeing and the degree of saturation which can be achieved. For example the different dyeing properties of mercerized cotton compared to non- mercerized cotton can be characterized by results from the time of half dyeing (i.e. the reciprocal of the rate of dyeing) and the saturation concentration of the substantive dye.

Dyeability is dependent on the following factors:
a) Chemical composition of the fibre: fibres of native and regenerated cellulose differ from each othei for example in their physic 0-mechanical structure but. despite this. they can be dyed with the same classes of dye. The same situation applies to protein fibres (a gram equivalent of wool is 1200 g and that of silk is 4200 g for reactions as bases) as well as for polyam ide and polyester fibres.

b) The coloristic dye class resp: the entire dyeing syst em including additions to the dyebath: certain dye classes are only suitable for one particular type of fibre. i.e. either the dye is not capable of dyeing certain fibres or can only dye them very slightly resp stain the fibre this can however, be caused by tin- suitable dyeing conditions. e.g. by using an inappropriate dyebath pH.

c) The geometrical form of the fibre: the fibre dimens ions as well as the morphological and histological structure of the fibre (the cuticle in cotton. the scale layer of wool and the skiii effect in viscose fibres) and the fine, or supra molecular structure of the fibre, whereby each change in fine structure results in a change in dye uptake: e.g. mercerized or non- mercerized cotton different regenerated cellulose fibres, drawn or heat-set synthetic fibres.

Those changes which, for example. involve changes in the ratios of crystalline. oriented and amorphous yeg ions due to the ageing of cotton or changes in the pore size, can be attributed to changes in the accessibility of the fibre to certain reagents. The relationship between fibre accessibility A% and the degree of crystallinity K% can be derived as follows:

A=(lOO-K)+aK

a is a constant which is related to the crystalline part of the fibre. It can have values from 0—1. An ideal subs tance with hundred percent accessibility would be represented by a = 1. The first part of the formula repres ents the amorphous part of the fibre p. and the second part represents the accessible surface of the crystallites (if a = 0. this surface would be inaccessible):

A=p+ctK
In the case of hiah tenacity viscose fibres K can vary, for example between the limits of 33—49%. a = 0.09—0.67. The accessibility A represents an appropria te numerical criterion of dyeability. It is an absolute parameter which represents a previously given property of the fibre and in general gives expression to the req uirement for its dyeability in achieving dark shades or black within an acceptable dyeing time provided the dye has adequately high build up properties. The fact that in isothermal dyeing dyeability decreases with the time of dyeing and that a fibre has a greater affinity for the dye at the beginning of the dyeing process than at the end is well known to every dyer. It is also possible to assess dyeability from the standpoint of the momentary quantity and rate of dye uptake by the fibre at a given time. The relative dyeability is always a kinetic parameter which is related to a specific dyeing system. If it is assumed that at time t. a dye concentration c1 exists in the fibre then tile reciprocal of this parameter Ct’ is the dilution of tile dye in tile fibre at tune t. At the start of dyeing the dilution reaches a value which inc reases beyond all limits (apart from the dye adsorption on the fibre surface at time t = 0: the dilution has a value of c1).

Tile dilution of solutions behave in an analogous manlier; before a substance dissolves in a solvent, tile dilution is infinite (since tile reciprocal value. i.e. the concentration, is equal to 0): with increasing concentrat ion tile dilution decreases (not. however, to 0 but to a certain value which corresponds to the dilution of the substance ill a saturated solution). Tile rate of dyeing at any time of dyeing t is proportional to this dye dilution:
Dc=K
dt= Ct

Tile dyeability of the fibre at time t is the dye dilution related to a unit of time. It is infinite at tile beginning (if the dye adsorption at time t = 0 is disregarded) and decreases with the time of dyeing (usually very quickly) and is equal to 0 at equilibrium. According to experience, the fibre is now no longer cap able of absorbing any dye from the dyebath (only all interchange of dye particles between the fibre and the dyebath takes place as a result of the dynamic equilibrium which exists in reversible processes).

Dye absorption index (fibre affinity index SF), fibre characteristic which gives information on the max dyestuff affinity of an acrylic fibre for cationic dye stuffs.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Introduction to dyeing machine

2012-11-29T01:12:00.000+06:00

MACHINE USED FOR DYEING
At the past the people used the fabric without dyeing, after the few age they was dyed fabric with the help of big pot. No dyeing machine was invented. People dyed the fabric with vary short range most probably at home for their domestic use. The dyeing was not so even because of the poor chemical and dyes ratio. The dyeing fastness was so poor and the dyed fabric was harmful for the health of human because the finishing process and the chemical neutralization process were not perfect. Day by day people increased and needs of cloth was also increased and also increase their decorative thinking. People try to invent the better way of dyeing and they invented the semi continuous dyeing machine. It was ensure the safety of dyeing. Day by day dyeing machine was developed. Various types of dyeing machines are used for both continuous and batch processes. Every dye system has different characteristics in terms of versatility, cost, tension of fabric, use of carriers, weight limitations, etc.

TYPES OF DYEING MACHINE:
*Fibre dyeing machine: The machine is used for dyeing loose Fiber form (Lose stock form)
*Yarn dyeing machine: The machine is used for dyeing loose or the cone of yarn. There are four types of yarn dyeing machine. Those are:
-Package (Cone, Cop, cheese) dyeing machine

      -Arm dyeing machine
      -Hank and Beam dyeing machine
     -warp dyeing machine

*Fabric dyeing machine: Those machines are used for fabric dyeing. Machine types and process are different for woven and knit fabric. There are different types fabric dying machine.
        -Jet dyeing machine
        -Jigger machine
        -Beam dyeing machine
        -winch dyeing machine

*Garment Dyeing machine: This machine is used to dye the complete garments. In that case the grey fabric are cut in to the cutting section and then those garments are produce in sewing section by proper sewing operation and those garments are send to garments dyeing section. There are two types of garments dyeing machine;
     -Rotary garment dyeing machine
     -Padule dyeing machine

BASIC REQUIRMENT OF DYEING MACHINE
. Dyeing machine shall provide sufficient movement for the dyeing and dyes chemical liquor to penetrate uniformly into every parts of the goods (fibre, yarn, fabric or cloth garments)
. The dyeing liquor movement inside the dyeing machine shouldn't be so vigorous that it damages the finer textile materials
. Dyeing Machine must be constructed of a material which will withstand prolonged boiling with acid or alkaline solutions from the dye bath.
. Heating arrangement inside the dyeing machine should be such that uniform temperature could be maintained.
. There should be some means of adding the concentrated dyestuff solution in such a way that it becomes well diluted before it comes into contact with the goods

. All moving parts and electric motors of the machine should be protected against the corrosive action of steam and acidic atmospheric conditions.

MACHINE REQUIRED FOR WOVEN FABRIC PROCESSING AND DYEING
Stage: Pretreatment
Process of dyeing; Singeing & Desizing Machine
Machine Brand: OSTHOFF, KOTOTO, CIBITEX,CILICO.

Process of dyeing; Scouring & Bleaching Range
Machine Brand: GOLLER, BRUGMAN, KUSTER, KOYOTO, BININGER

Process of dyeing; Mercerizing Machine
Machine Brand: GOLLER, BRUGMAN, KUSTER, KOYOTO, BININGER, ARIOLI, CILICO, MORRISON.

Process of dyeing; Washing Range
Machine Brand: BRUGMAN, ARIOLI, BININGER,KUSTER

STAGE :COLORATION

Process of dyeing; Dyeing Machine
Machine Brand: MONFROST, BRUKNER, BININGER, ARIOLI, KUSTER, MORRISON,SCLAVOS,

Process of dyeing; Printing Machine
Machine Brand: STROKE, J-ZIMMER

STAGE: FINISHING

Process; Stenter machine
Machine Brand: ARIOLI, BRUKNER, MORRISON

Process; Sanforising machine
Brand MORRISON, BRUKNER,

Process; Calender
Machine Brand: Machine RAMICH GAURANI

Process; Raisimg
Machine Brand: LEFER, MARIO CROSTA

Process; Peach machine & brushing
Machine Brand: LEFER, MARIO CROSTA

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

DYEING

2012-11-27T23:15:00.001+06:00

INTRODUCTION TO DYEING

Day by day dyeing technology is changing for providing more coloration facility, more dyeing machine productivity, more upgraded dyed product, better safety, lower wet processing time, higher quality of textiles, more consistency of dyes in the textile fabric & finally for human comfort. In textile wet processing and synthetic dyeing there are various types of machinery are used from dyeing pretreatment to finishing which vary with dye brand to brand according to their dyeing technology.

Over the years for textile fabric processing we saw a lot of development through which we can provide a wide range of textile product with different coloration appearance & which are used for different purpose. With the aid of textile machine now most delicate fabrics with different finish is provided which could not think at past. Usually there are three types of fabric.

i. woven fabric
ii. knitted fabric
iii. non-woven fabric

All of the above fabric categories have different derivatives. Among them Woven fabric has a great versatility. That can be used in home textile as well as fashion. New technology machinery provides versatility not only by varying the structure of woven fabric manufacturing but also varying in processing such as in coloration & by different finishes.

This web site contains some information on woven fabric processing machinery with their technical data as well as their component & advantages provides through their machine. It also contains some necessary picture & diagram which helps to be familiar with the dyeing machine. This project also contains dyeing brand information, dyes manufacturing country & silent feature.

FLOWCHART OF WOVEN FABRIC DYEING

                                    GRAY FABRIC INSPECTIO
                                                      ↓
                                     STITCHING & BRUSHING
                                                      ↓
                                               SINGEING
                                                      ↓
                                                DSIZING
                                                      ↓
                                               SCOURING
                                                      ↓
                                  BLEACHING MERCERISING
                                                      ↓
                  DYEING   ←                                   →     PRINTING
↓                                                               ↓
                                                FINISHING

BRIEF DESCRIPTION OF EACH STEP OF DYEING
SINGEING
Singeing is the first step of dyeing. Singeing is important for a fabric to provide a smooth finish. Woven fabric goods usually contain protruding fibers from textile yarns. Singing process is used to remove those protruding fibres from the surface of the fabric. The fabric is passed in to a flame and these protruding fibers are burned out. Some time copper plate is used remove the fibre. For printing, singing is most essential to improve the surface smoothness by eliminating the pilling and fibres.

DESIZING
Desizing is an important dyeing preparation step. During weaving sizing material is used to increase the strength of warp yarn. The sizing material is hydrophobic in nature. That’s why it must be removed before dyeing. Desizing is the process to remove the size material from the fibre. There are many chemical to remove the size material. Enzymes are the most popular material to used in sizing process.

SCOURING
Scouring is one of the most important processes of textile fabric dyeing. All of the natural fibre contains natural oil and wax. Before dyeing, those oil and wax must be clean for smooth and proper dyeing. The Scouring is a cleaning procedure that used to eliminate those oil, wax from fibers, yarns, or fabric by soaping. For scouring process alkaline solutions are typically used; however, Solvent solution may be used in some case. The parameter of scouring procedures like temperature, chemicals, and time vary with the type of fabric and fibre types. Impurities are including natural materials, dirt lubricants and other. Residual tints antistatic agents, water-soluble sizes, used for yarn verification.

BLEACHING
Bleaching is a complex process. The most common bleaching agents include sodium chlorite, hydrogen peroxide, sulfur dioxide gas and sodium hypochlorite. All the natural fibre contains a natural color which is harmful for dyeing shade matching. For example the cotton has natural yellowish shade. So it is important to remove the natural color from the fibre. Bleaching is a used to eliminate the natural color from the fibre and prepare the fabric for further process. According to the types of fibre the bleaching chemical is selected. Hydrogen peroxide is most popularly used bleaching agent for cotton and cotton blends.
MERCERIZING
Mercerization is used to increase appearance, luster and dye ability of textile fibre. Mercerizing is a semi-continuous or continuous chemical process used for cotton and cotton/polyester goods.Room temperature must be maintain during this process, causes the twisted ribbon-like cotton or cotton polyester blend fabric to swell into a round shape and to contract in length. This causes the fiber to become more lustrous than the increase in strength original fiber, by as much as 20 percent, and increase its affinity for dyes during dyeing

DYEING
Dyeing is proper way to coloration of textile material (fibre, yarn, woven fabric, knitted fabric, non-woven fabric). Suitable dyestuff, dyeing machine and dyes chemical is required for achiving proper dyeing shade. There are four types of dyeing,

1. Fiber Dyeing
2. Yarn Dyeing
3. Fabric Dyeing

4. Garment Dyeing

PRINTING
Printing is the process to make colors on the textile materials with the presence of thickener to give sharp design. The thickener will be removed after the printing process to make softer handle.
Classification of Textile Printing
1. Direct Printing: Printing on material directly with the ink on the designed goods.
2. Reverse Printing: Printing on the goods by printing ink on background.

Textile Printing Process

1. Fabric Preparation
2. Silk Screen/Rotary Screen/Roller Preparation
3. Print paste Preparation
4. Print ink preparation
5. Printing on fabric
6. Drying
7. Fixing
8. Washing and Soaping
9. Final Drying

FINISHING

Finishing is the last steps of dyeing. Actually dyeing finishing is required for quality assurence of dyed fabric. There are different types of finishing those actually depends on buyer requirment.
There are two types of finishing:
i. Chemical finishing
ii. Mechanical finishing.

Chemical finish: Here finishing effect is brought out by means of chemical. Some examples are:
i. Optical finishing
ii. Resin finishing
iii. Antimicrobial finishing

Mechanical Finishing: Here finishing effect is brought out by means of mechanical application. Some examples are:
i. Calendaring
ii. Heat setting

iii. Brushing
iv. Compacting.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Dyeing modified polyesters with disperse dyes

2012-07-23T23:49:00.000+06:00

Dyeing modified polyesters

A variety of modified polyester fibres are available that can be dyed with disperse dyes, and other types of dyes, at temperatures not exceeding 100 °C. The so- called non-carrier types can be dyed with disperse dyes at the boil, although very deep shades may require a small amount of carrier. The basic polymer is PET but contains a comonomer with a more flexible molecular chain such as suberic acid (1,8-octanedioic acid). The polymer has a more open molecular structure, a lower Tg and dye penetration is therefore easier. The new polytrimethylene terephthalate fibre (Corterra) also has a lower Tg than PET and can be dyed with disperse dyes in a bath at the boil under normal pressure.

Polyester modified to have anionic sites contains comonomers such as 5- sulpho-isophthalic acid. It is readily dyed with disperse dyes, and with cationic dyes. These types of modified polymer are also more easily hydrolysed. Therefore, during processing, the pH of solutions must not be excessive and the maximum pressure dyeing temperature should not be above 120 °C. Additions of Glauber’s salt to the dyebath protect basic dyeable polyester fibres from hydrolysis. Modified polyester fibres are also more sensitive to heat setting before dyeing, the maximum setting temperature being around 180 °C. Cationic dyes require some acetic acid in the dyebath and dyeing at pH of 4–5 at 100–120 °C is typical. The brightly coloured dyeings with cationic dyes have good fastness to washing and light. Combinations of regular and basic dyeable polyester can be dyed with mixtures of cationic and disperse dyes to produce two colour effects. The carpet industry is a major outlet for this type of fibre. The new polyester fibre poly(trimethylene terephthalate) produced from terephthalic acid and 1,3-propanediol, rather than the usual 1,2-ethanediol, is also initially intended for use in carpets.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

Disperse dyes for a polyester fabric

2012-07-23T23:39:00.000+06:00

Disperse dyes for a compound shade on polyester can have quite incompatible dyeing properties. The SDC classification of disperse dyes is based on migration ability during exhaust dyeing, colour build-up, sensitivity to changes in temperature and the rate of dyeing. This type of dye is often classified on the basis of dyeing rate and sublimation fastness, particularly for polyester dyeing.

Classification of disperse dyes for polyester

These two properties are a function of molecular weight and the number of polar groups in the dye molecule. Table shows the most common classification. It applies to the dyeing of acetate, of polyester with or without carrier, and of polyester/cotton, but is somewhat arbitrary.

Most dyeing and fastness properties change gradually with increase in molecular size. Small dye molecules with low polarity are levelling, rapid dyeing dyes with poor heat resistance. These are called low energy disperse dyes. More polar, higher molecular weight dyes have low dyeing rates, poor migration during dyeing but good heat and sublimation fastness. These constitute the high energy disperse dyes. The development of disperse dyes of improved sublimation fastness required dye molecules with relatively polar and hydrophilic substituents to reduce their vapour pressure at high temperatures. This promotes somewhat higher solubility in water but the increase in molecular size reduces the dyeing rate at a given temperature. The high energy disperse dyes are those requiring a higher Thermosol temperature. The light fastness does not depend on the molecular size. Dyes in a mixture are usually selected from the same energy class. Build-up of the colour on shade requires that the dyes all have about the same dyeing rate. Testing of dye recipes is essential because many disperse dyes, even dyes of the same dyeing group, are incompatible in mixtures. This is true even though they may have the same dyeing rates and build-up properties when tested separately. The dye manufacturers provide considerable information assisting the dyer to select appropriate dyes for a given application.

Wish you good luck-------------------------------------------
You Should read more related post to gain more knowldge. -->

The Thermosol process of polyester fyeing with disperse dyes

2012-07-23T23:18:00.000+06:00

The Thermosol process with disperse dye is a continuous dyeing process introduced by Du Pont in 1949. A dispersion of the disperse dyes is padded onto the polyester fabric. The material is then dried using a hot flue air dryer or by infrared radiation, the latter usually giving much less migration of the dye. The use of a migration inhibitor in the pad bath is usually recommended. Even then, dye migration during drying of materials of 100% polyester is difficult to eliminate and such materials tend to dye more deeply on the yarn surface. Final drying of the padded material takes place using heated cylinders. Section 10.5 discusses padding and migration in continuous dyeing.

The dry fabric is then heated in air, or by contact with a hot metal surface, to a temperature in the range of 190–220 °C for 1–2 min. In hot air, at least 50% of the time is for heating the polyester to the maximum temperature. The specific conditions depend on the type of equipment, the dyes and the fabric. As the fabric approaches the maximum temperature, the disperse dyes begin to sublime and the polyester fibres absorb their vapours. (Sublimation is the transformation of a solid directly into a gas without forming the liquid phase. A common example is the evaporation of ice on a cold day.

At about 200 °C, sublimation of the solid dye, transfer of its vapour into the fibres, and penetration into the fibres by diffusion are all quite rapid. Commercial disperse dyes for the Thermosol process are usually classified according to their ease of transfer by sublimation. This is related to the their fastness to heat in hot pressing and pleating. It is imperative that as much of the vaporised dye as possible be absorbed by the polyester fibres. If the rate of sublimation is too low, dye particles will remain in the fibre matrix and the colour yield will be low. When the rate of sublimation is too high, the dye vapour builds up faster than it can be absorbed by the polyester and escapes from the proximity of the fibres, usually depositing on the machine walls. The temperature and time of heating must therefore be carefully controlled to provide the appropriate rate of sublimation and the optimum colour yield.

Despite the simple dyeing mechanism, there are a number of technical problems that can result in inferior dyeings. The fabric must initially contain a uniform distribution of dye particles if the final dyeing is to be level. Therefore, uniform dispersion and padding are crucial. Migration must be minimised, particularly if it leads to more dye on one face of the fabric than the other. During the sublimation stage, it is essential to provide conditions that allow a balance between the rate of dye vaporisation and absorption of the vapour by the fibres. The Thermosol process is widely used for narrow fabrics of 100% PET such as ribbons and belts. The vapour dyeing technique also applies to transfer printing.

The Thermosol method is popular for dyeing the polyester component in cotton/polyester fabrics. In this case, the absorbent cotton fibres in the fabric hold almost all the initial dye dispersion padded onto the material. This helps to reduce dye migration during drying. During subsequent heating, the dye vaporizes and transfers from the cotton into the polyester fibres. Since two types of fibres are being continuously dyed, each with a separate fixation step, the dyeing ranges for cotton/polyester materials tend to be very complex. Both the dyes for the polyester and for the cotton are initially padded onto the fabric. The polyester is dyed in the Thermosol unit. After additional padding of the cooled fabric with a solution of the other required chemicals for dyeing the cotton, it passes through a steamer. This promotes diffusion and fixation of dyes on the cotton. The second pad contains NaOH and salt solution for dyeing with reactive dyes NaOH and Na2S2O4 for vat dyes, NaS or NaSH for sulphur dyes and simply salt solution for direct dyes. A thorough washing of the dyed fabric completes the process. This includes rinsing, an oxidation step in the case of vat and sulphur dyes, soaping to remove surface colour and final rinsing.

Polyester microfibres dyeing with disperse dyes

2012-07-23T23:07:00.000+06:00

Microfibres of PET for production of fabrics with a lush handle are a fairly recent development. Microfibres have a fineness of less than 1.0 dtex per filament, an arbitrarily chosen value. Normal PET filaments are in the range 2–5 dtex. The introduction of microfibres has created a number of dyeing problems with disperse dyes. Firstly, microfibres require more disperse dye than regular denier fibres to achieve the same depth of shade. The concentration of dye (% owf) required to achieve a given depth of shade is usually assumed to be inversely proportional to the square root of the filament fineness:

Add captionPolyester microfibres dyeing with disperse dyes

In this equation, CM and CR are the required concentrations of dye in the polyester microfibre and regular denier fibre respectively, rM and rR the respective filament radii, and dtexM and dtexR the respective filament fineness. This approximate relationship predicts that a 0.5 dtex microfibre will require (2.5/0.5)1/2 or about 2.2 times as much dye in the fibre to give the same depth of shade as a 2.5 dtex filament. It only applies, however, when the regular and microfibres being considered are identical in all other properties. In fact, it is the dyeing rate that should be proportional to the available filament specific surface area (m2 g–1) and therefore inversely proportional to the filament radius and to the square root of the filament decitex. The value of the diffusion coefficient of the dye in the fibre does not change when the filaments are finer.

Secondly, because of the more rapid uptake of dye by microfibres, level dyeing requires greater control. The greater specific surface area of microfibres also means that dye desorption during washing is more rapid and the washing fastness is less than for fabrics made of conventional filaments. Dyed microfibre fabrics also have lower fastness to light at equal apparent depth. In addition, the closeness of microfibre packing in yarns makes wetting and yarn penetration difficult. Nevertheless, the lush handle and special surface effects that are possible for fabrics made of microfibres have ensured their success.