Polyester dyeing in HTHP dyeing machines

Important factors: polyester dyeing in HTHP dyeing machines.
1.Water quality

Traces of soluble copper and iron salts can affect the shade of some disperse dyes quite markedly due to the formation of coordination complexes.The presence of calcium and magnesium cations can interfere with the anionic dye dispersing agents/leveling agents and wetting agents present in the dyebath. To overcome these problems a small amount of chelating agents might be added to the dyebath. 

2.pH of the dyebath

Ideally the pH of the dyebath should be buffered by use of a quality pH regulator, in the range of 4.5-5.5 to minimize the possibility of dye hydrolysis.

3.Use of Surfactants in dyeing

There are a multitude of purposes for which anionic surface active agents are used in dyebaths, such as wetting, penetrating and deareation etc. anionic surface active are also used to stabilize the diluted dispersions of the dye.This is necessary particularly when dyeing paler shades where dyebath concentration of surfactant introduced with the dye itself is small.

The non ionic surfactants are generally used to control the rate of exchange of dyebath to the fiber.

4.Temperature
For most cost effective dyeing of polyester depends on factors such as starting temperature ,rate of heating ,dyeing temperature and duration of dyeing which should result into well exhausted bath ,satisfactory color uniformity and batch to batch shade consistency.
A general rule of thumb , the starting temperature of dyeing is 70-80 degrees , the rate of rise of temperature is 1.5-2 deg.Celsius /min and the dyeing temperature is between 115-135 deg.Celsius.
5.Time

For an ideal dyeing time selection , one must take into account the exhaustion of dye bath , uniformity of the dye , satisfactory color penetration , for good color fastness and reproducibility of the dyeing results. Generally 15-60 minutes of dyeing time is followed and it is not necessary to prolong the dyeing long beyond the time of maximum exhaustion.

6.Dyes

The dyes with similar dyeing characteristics must be selected for particular formulation, it is important to identify the actual dyeing rate of each component will be dependent on the concentration present in the formulation.Care should be taken that the dyeing conditions allow the slowest dyeing component to reach the effective equilibrium.

7.Oligomers

Typically polyester fibres contain between 1.5 and 3.5% by mass of low molecular esters, the principal oligomer being cyclic tris(ethylene terephthalate) with smaller quantities of a dimer, pentamer as well as traces of other compounds.

when oligomers are released from the polyester fibre, after some time
at 130° C, if an efficient dispersing agent not present in the bath to prevent crystallization of the oligomers, and to prevent small particles of oligomers coming together to form larger agglomerates, oligomers will deposit on the yarn and the machine.

Dispersing will maintain the oligomers in a fine dispersion so that when the machine is drained more oligomer goes down the drain. Discharging the dyebath at high temperature if this is possible can also reduce oligomer deposition because any of the material soluble during dyeing at a high temperature can precipitate during cooling.
8.Reduction Clearing
Reduction-clearing treatment is necessary to remove any dye remaining on the fibre surfaces, If not removed, this surface contamination can undermine the brightness of shade as well as the wash, sublimation and crock fastness results.Commonly, the dyed polyester is cleared of surface-deposited dye as well as auxiliaries (e.g. carriers, surfactants) by means of treatment with detergent or reductive or oxidative treatments, in order to secure optimum fastness of the dyeing and also to improve the brightness of shade.
The usual treatment carried out, especially in heavy depth, is reduction- clearing, where the dyed fibre is treated in a strong reducing bath, usually made up of sodium dithionite and caustic soda. A treatment for 20 minutes at approximately 70-80 deg Cel, is often sufficient to clear
the fibre surface, but the ease of removal varies from chromophore to chromophore and dye to dye. This treatment acts to destroy loose azo disperse dye through chemical reduction of the azo link . Anthraquinone disperse dyes are not fully destroyed by such a treatment but a degree of removal of surface dye is achieved through temporary solubilisation of the disperse dye to the alkali-leuco form.

9.Stripping 
Stripping of disperse dyed material can be accomplished by treating goods
a. In a blank bath containing non ionic leveling agent at 130 deg.cel.
b.For chemical destruction of dye use 1-2 gpl NaOH and a reducing agent
or mild acidic treatment with zinc sulfoxlate-formaldehyde or sodium chlorite can reduce the shade to almost a off white back ground.

A New Study on Stripping for Polyester Fabrics

10.Prolonged treatment of polyester in alkaline solutions

Prolonged treatment of polyester goods in alkaline solutions will cause weight loss due to hydrolysis of polyester at the fiber surfaces, since the fiber surface has been eroded considerably  after a long alkaline treatment it is very difficult to rework the goods to give them originally anticipated appearance.

Watch Video on HTHP package dyeing machine

 

Useful Auxiliaries and Ingredients Used in Textile 

Q&A Session for Overview of Dye Classes and Methods of Coloration Webinar.

Problems with oligomer in dyeing polyester yarns and fabrics. 

Dyeing with Disperse Dyes

Search for more information on the subject

 

pH and pH buffers

pH

In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. definition: pH is the negative logarithm of the hydrogen ion concentration.  pH is a measure of the concentration of hydrogens ions ( H⁺ ions or protons) in a solution.

pH scale

The pH scale was defined by Sören Sörensen, Danish biochemist, in 1909The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic and a pH more than 7 is alkaline.

Measuring pH

Measuring pH is essential not only in finding the chemical characteristics of a substance but also as the first step toward managing chemical reactions.

Measuring pH involve either the use of pH measuring electrodes or indicators whose colors are dependent on pH. A pH meter measures the difference in potential between a reference electrode insensitive to changes in pH and an electrode sensitive to such changes.

pH indicators based on color changes are normally used in the form of pH papers. The paper is wetted with the solution being measured and the resulting color is compared with color standards to determine the pH.

In the textile industry, measuring pH is important in product testing, pretreatments,dyeing and finishing processes. 

pH buffers

A pH buffer is a substance that resists a change in pH when small amounts of an acid or a base are added to it. The pH of a buffer changes very little when small amounts of  an acid or a base is added to the buffered solution. A buffer consists of approximately equal amounts of conjugate weak acid/base pair in equilibrium with each other . Strong acids and their conjugate bases do not produce a buffer since in  strong acid ionization is complete and there is no equilibrium.

Why pH changes during a Textile dyeing process

1. Water quality
2. Reaction products
3. Additives during the process
4. Time
5. Temperature
6. Contaminants in the substrates.

Some pH  buffers systems useful in textile pretreatment , dyeing and finishing.

HCl and sodium citrate                                     pH 1-5

Citric Acid and sodium Citrate                          pH 2.5-5.6

Acetic Acid and Sodium Acetate                       pH 3.7-5.6

K₂HPO₄ and KH₂PO₄                                      pH 5.8-8.0

Na₂HPO₄ and NaH₂PO₄                                  pH 6-7.5

Borax and NaOH                                              pH 9.2-11

pH in textile coloration

Most of the dyeing processes requires a controlled pH , such as slightly alkaline in direct dyes , strong alkaline in reactive , vat and azoics , acidic in disperse and basic dyes strongly acidic in acid dyes etc.

The control of pH in textile processing is ensured by fundamentally three different techniques , such as

1. The maintenance of a relatively high degree of acidity or alkalinity .
2. The control of pH within fairly narrow tolerances mainly in near neutral regions.
3. The gradual shift  of pH as dyeing proceeds.

Many processes of textile processing are pH dependent.

1. Scouring of cotton in highly alkaline conditions
2. Bleaching  of different substrates where pH has to be maintained for proper bleaching action.
3. Solubilising the dyestuffs.
4. Exhaustion and fixation
5. Oxidation
6. Stripping
7. Finishing 

further reading
pH of textiles by water extraction method

Dyeing Cationic Dyeable Polyester (CDP) with Cationic Dyes By Michael Hilton

This article is contributed by Michael Hilton

Cationic Dyeable Polyester is a special Polyester fiber which has undergone a change during polymerization. They were built of molecules of 5 - sulphophthalic acid, to generate anionic sites that the fibers of normal PET not have. Having anionic groups it can also be dyed with cationic dyes with results of high brilliance. However, these fibers can be dyed with disperse dyes. Compared to ionic dyes, disperse dyes have smaller molecular extinction coefficients and lower build-up property, so these dyes cannot give bright and deep colors. This type of fibers were born also to lower the Tg (glass transition temperature) of the polymer, 10 ° C lower than normal Polyester fibers, so to obtain a more segmental mobility and open polymer structure. Resulting in increased rate of diffusion of the dye in the fiber at a lower temperature. Tg Range (70 – 85°C). This modified polymer is also more easily hydrolised and more sensitive to heat setting before dyeing at a maximum temperature of 180°C.

Example 

scouring and dyeing exhausted process in Overflow – Jet Machine (Liquor ratio - 1:10 – 1:20) :

Scouring:

Continuous washing cold for 10 min 

drain well (for water soluble oils)

Fill with water 30 ° - 35°C

0,5 g/l Antifoam (preferably non-silicone) alone

1 g/l Detergent non – ionic

0,5 g/l Caustic Soda 36° Bè

Raise to 80°C quickly and hold for 20 – 25 min

Drain well 

washing cold for 10 min 

and after starting in dyeing

Dyeing with Cationic dyes

Follow the Graph below :

The dyebath is set at 60°C - introduce order

0,5 g/l Antifoam (alone)

6 g/l Sodium sulphate (only dyeing at 120°C) (1)

1 g/l Dispersant non-ionic

X g/l Acetic Acid pH = 4,5

X % Levelling – Carrier anionic (only dyeing at 98°C)

X% Cationic dyes (dissolved at 60°C with 1 g / l of acetic acid) - (introduce preferably dosed curve progressive Sen +)

Then raise to 70°C - after to 85°C at 0,5°C / min (while the fiber is softening) and hold for 10 min, after raise to 120° (or 98°C) at 0,6°C / min – hold for 30 – 60 min (depends on the depth of the color) 

then cool to 70°C at 0,5°C / min and check the color.

Please note that sodium sulphate (Na +), being very stable at high temperatures, is the protector of te anionic sites sensitive to the acid at 120 °C.

After dyeing, the dyed samples were rinsed and washed with 2 g/l of non-ionic detergent at 60 – 70°C.

Light fastness: moderate to good

Washfastness: good to excellent

Rubbingfastness: good

Excellent resistance to sublimation on wet

No fouling of lycra mixed

Polyester Microfibers:- Dyeing and Wet Processing

Microfiber

A synthetic fiber that is extremely soft, lightweight, breathable, durable and ultrafine. In fact, microfibers are two times finer than silk and one hundred times finer than a human hair. Microfiber is currently manufactured from acrylic, nylon, polyester and rayon.Ultra-microfibers on the market are even finer – some having thickness of just 1/200th the thickness of human hair!

Microfibres refer to staple fibres, or individual filaments within yarns, which have fineness less than 1 decitex ( 1 grams per 10,000 meters) and For any fiber to be classified as microfibre yarn, the weight per 10,000 metres of yarn (dtex) is divided by the number of filaments (f), the result must be below 1.
All about microfibers

Microfibers: Functional Beauty

Properties of Polyester Microfibers

1. Lightweight and flexible
2. 
   
   Good stability and shape retention
3. 
   
   Anti-wrinkle property
4. 
   
   Have a wicking ability that permits perspiration
5. 
   
   Comfortable to wear as they are more spongy
6. 
   
   Doesn't water stain - superior water repellency is available
7. 
   
   Woven or knitted into a very high quality fabric construction
8. 
   
   Formerly commenced as a polyester microfiber, today you can find nylon, rayon and acrylic microfibers too.
9. 
   
   Strong and durable, water repellent and wind resistant -so tightly woven, that the fabric can't be penetrated by wind, rain or cold
10. 
    
    Lightweight, resilient or resist wrinkling, have a comfortable array, preserve shape and resist pilling
11. 
    
    The positively charged microfibers draw dust; the tiny fibers are capable to enter the microscopic surface voids most materials
12. 
    
    Washable, dries quickly and also washable in at the water temperatures up to 200 degrees and their characteristics will remain intact.
13. 
    
    Electrostatic effect - Hair, lint and other dust particles are attracted and grabbed by the microfibers without lifting dust.
14. 
    
    The density of the material allowable it to grip six to eight times its weight in water hence high absorbing power capacity
15. 
    
    The attraction capability of the microfibers is so sound, even absorbs bacteria and germs - hence can be use as germ or bacteria free purpose
16. 
    
    The fabric consists of millions of small tiny conduits that carry oil and grease too.
17. 
    
    Benefits of microfibers
18. 
    
    Comfortable - very soft, texture like silk, lightweight
19. 
    
    Due to its fineness and superior fiber surface area making deep, rich and bright colors achievable
20. 
    
    Less "sweaty" in warm weather than usual synthetics
21. 
    
    Quickly cleanable - clean just with water
22. 
    
    Highly intense and shrink-resistant
23. 
    
    Presents insulation and breathability
24. 
    
    Change without help - to establish lovely drape
25. 
    
    Very fine - finer than the most precise silk
26. 
    
    More reusable for cleaning alternative - compared to other mops more efficient and long life

Dyeing of polyester Microfibers
Due to their fineness, the total surface area of microfibre yarn or fabric is far greater than ordinary fibres. Threfore

1.Due to its special structure ,micro fibers has much larger quantity of size ,oil agents and wax on warp yarns.

2.Since microfibres have very small interstitces, with consequent difficulties of size accessibility and duffusibility, desizing becomes quite difficult and costly.

3.Microfibres have greater absorption area resulting in a dyeing rate four times higher than that of normal, which can cause unlevelness in dyeing.

4.They also require more dyestuff than standard fibres to obtain the same depth of shade.
5.Larger external surface means an increase in number of threads exposed to light which, on destruction of dye, is expressed as lower light fastness rating.
6. Wash fastness and color fastness to rubbing is also poor.
7.Staple microfibres offer difficulty in carding.

The problems in wet processing of microfibers can be overcome by

1.Better knowledge about the size applied and optimum parameters during desizing operation.

To achieve satisfactory dyeing effects ,desizing and refining process must be done before dyeing and after desizing and refining , there should be no impurities left such as electrolyte, antistatic finishing agent , spin finishes and blot.

2.Pre-setting

Suitable pre setting conditions ( time ,temperature and tension) helps not only in stable dimensional stability ,softness but also better dyeing results.

3.Alkali weight reduction

Alkali weight reduction s to treat the fabric with concentrated alkali at high temperature.fber molecule hydrolyse under this condition and lose some weight with change in properties, thus space occurs between crossing points and rubbing resistance relative to slippage among yarns becomes small.Alkali weight reduction makes fabric soft, liveliness, limber and improved absorption.

2.Careful selection of the dyes.

Proper dye selection which are
1.Compatible
2.Having same exhaustion rates
3.Having high wash fastness properties.
4.Good migration and levelling properties
 eliminates problems regarding build-up and fastness properties.
Disperse dyes for polyester microfibers

3.Optimizing the dyebath conditions and dyeing cycle.


Optimised dyeing cycles can be worked out by controlling the temperature to account for the high rate of dyeing and to eliminate the risk of uneven dyeing.Chemicals and dyes to be added at, at least 10-20 deg.C lower temperature than normal polyester fiber dyeing. The additions of dyes must be progressive or devided at least into 4 parts. The heating rate must be slow from 40 deg C to 100 deg C. 10-20 min more holding time required at 130 deg C as compared to normal PES.


4.Proper selection of  Dyeing machinery.

The dyeing machine must have the required automation to fufil the requirements of microfiber dyeing such as microprocessor controlled dosing , proper and accurate heating rate control etc.


5.Proper selection of dyebath additives
such as
Levelling agents :- A strong levelling agent which shall start working at lower temperatures.
Dispersing agents :- Higher quantities of dispersing agents are needed because amount of dyes required are more to produce the desired depth.
Chelating agents:-
Anticreasing agents,Dyebath softners/Lubricants :- Because microfiber textiles are prone to creasing , therefore use off dyebath lubricants is must.

6.Proper aftertreatment of dyed goods.
Soaping :- In order to obtain satisfactory color effect , fabric should be soaped after dyeing .Soaping is the key process to achieve satisfactory dyeing results on polyester especially polyester / nylon microdenier fabric.


Reduction clear :-Good reduction clear process is needed to achieve satisfactory washing , rubbing and light fastness properties.
Washing :-Is required for neutralising and removing alkali after reduction clear treatment.
Softening, anti soil and antistatic treatment :-Because microdenier fiber easily stains and produces static charges, a hydrophilic ,antistatic and antisoil treatment besides softening is highly recommended to ensure fabric softness and comfortability.

Recommended Dyeing Cycle for polyester Microfibers

Dianix PLUS( Dystar) or Longsheng  is a new range of five compatible, level-dyeing dyes for reliable dyeing of medium and heavy shades, especially on microfiber and weight-reduced polyester, whether applied under mild alkaline conditions to control trimer, or under conventional acid conditions.
Dianix E-PLUS" for Pale Shades on Polyester Fabrics
Fashion application of polyester

Application of polyester Microfibres

Microfibers are most commonly found in polyester and nylon. Some rayon and acrylic micros are in production and available to consumers. Micros can be used alone or blended with conventional denier man-made fibers as well as with natural fibers such as cotton, wool, and silk.

In textiles

Microfibers are used in a variety of fabrics, but most commonly in dress and blouse weight garments. Suit jackets and bottom weights are becoming available. Look for micros in lingerie, rainwear, outdoor fleece and wind-resistant sportswear, as well as tents, sleeping bags, track and jogging suits. The strength of microfibers make them particularly adaptable to sueded or sandwashed finishes because of their extensive fiber surface area and the use of strong fibers like polyester and nylon. As a result, many microfibers simulate the appearance of sandwashed silk.

Other Main products for which microfiber are ideally suited:

• Microfiber Glass Cloth

• Duster/Multi-purpose Microfiber Cleaning Cloth

• Microfiber Scrubber

• Microfiber Kitchen Cloth

• Microfiber Optical & CD Cloth

• Microfiber Mops

• Microfiber Cleaning Sponge

• Microfiber Cleaning Cloths – Terry Cloths, Suede Cloths, Waffle-Weave Cloths

Microfiber Makes the Grade
http://www.tex.in/education/nextiles/fib/mic/mic.html
http://ygmfranchise.blogspot.com/2007/07/cleaning-tips-microfiber.html
http://www.microfibergreen.com/is-microfiber-green-product.html
http://www.norwexnow.com/microfiber%20science.html

 

Sublimation Fastness Of Disperse Dyes

Sublimation is the process of phase change from solid to gas , without going into liquid phase.

Fastness to sublimation is probably the most important requirement of dyed polyester, apart from fastness to light. The migration behavior and wet fastness of disperse dyes on polyester are closely involved with their response to heat treatments.

Adequate fastness to heat is essential so that the dyed material will withstand the conditions encountered in

1. Heat setting,
2. Durable pleating
3. Ironing or pressing of the goods during the making-up of garments.
4. Finishing processes where high temperature is involved.
5. Thermal fixation of prints.

The poor sublimation fastness results into following problems

1.Change in original shade
2.Staining on adjacent fibers in contrast dyed fabrics.
3.Poor color yield and fixation rate in thermal fixation of prints.
4.Staining of dyed polyester sewing threads after stitching and embroidery in contrast stitched and embroidered articles.
5.Cross staining during storage.

How to avoid the problem due to poor sublimation fastness

Since the problem of poor sublimation is concerned to polarity of substation groups in dye molecule , therefore following steps are suggested to avoid the problem,

1.Pre heat setting most of the fabrics before dyeing.
2.Carefully selecting the dyes so that all component yarns have satisfactory fastness in multicolored/contrast color designs ,where fabric is post heat set.
3.Selecting high sublimation dyes for dark shades , and medium /low sublimation dyes for pale shades.
4.The sublimation fastness influenced by the dyeing conditions and dyeing cycle followed, therefore the dyeing cycles must be optimized for best sublimation fastness.

How to test the sublimation fastness of disperse dyes

The sublimation fastness of disperse dyes is usually tested for staining and shade change , tested at 180 oC /210 oC for 30 seconds and rating is done on 1-5 grey scales.

Standard Test Method for Sublimation fastness testing.
AATCC Test Method 117-2004
ISO 105-P01.

Polyester Dyeing

Polyester

Polyester is a term often defined as “long-chain polymers chemically composed of at least 85% by weight of an ester and a dihydric alcohol and a terephthalic acid”. In other words, it means the linking of several esters within the fibers. Reaction of alcohol with carboxylic acid results in the formation of esters.

Polyester also refers to the various polymers in which the backbones are formed by the “esterification condensation of polyfunctional alcohols and acids”.

Polyester can also be classified as saturated and unsaturated polyesters.

Saturated polyesters refer to that family of polyesters in which the polyester backbones are saturated. They are thus not as reactive as unsaturated polyesters. They consist of low molecular weight liquids used as plasticizers and as reactants in forming urethane polymers, and linear, high molecular weight thermoplastics such as polyethylene terephthalate (Dacron and Mylar). Usual reactants for the saturated polyesters are a glycol and an acid or anhydride.


Unsaturated polyesters refer to that family of polyesters in which the backbone consists of alkyl thermosetting resins characterized by vinyl unsaturation. They are mostly used in reinforced plastics. These are the most widely used and economical family of resins.
Characteristics of polyester
1.Polyester fabrics and fibers are extremely strong.
2.Polyester is very durable: resistant to most chemicals, stretching and shrinking, wrinkle resistant, mildew and abrasion resistant.

3.Polyester is hydrophobic in nature and quick drying. It can be used for insulation by manufacturing hollow fibers.
4.Polyester retains its shape and hence is good for making outdoor clothing for harsh climates.
5.It is easily washed and dried.
Uses of Polyester
The most popular and one of the earliest uses of polyester was to make polyester suits – all the rage in the 70s. Polyester clothes were very popular. Due to its strength and tenacity polyester was also used to make ropes in industries. PET bottles are today one of the most popular uses of polyester


Dyeing
The dyeing of polyester is usually carried out in following forms,

loose fibres and tops
yarn and fabric
piece goods (jet, overflow and beam dyeing machine)
The dyeing of hydrophobic fibers such as polyester with disperse dyes may be considered as a process of dye transfer from a liquid phase to a solid organic solvent.
Stages in polyester dyeing

There are three main stages in a polyester dyeing cycle
Dissolution :- of the dye in water in the form of fine dispersion.
Distribution or adsorption :- adsorption of the dissolved dye onto the fiber surface.
Diffusion:-penetration of the dye molecules deep inside the inner cores of the fiber.
The important parameters in a polyester dyeing cycle

1.pretreatment process.
 The material usually contains small amounts of water-soluble or emulsifiable preparations which can be readily washed off. With tops, loose fibers and smooth or textured yarns rinsing for 10 min with cold water is often sufficient. Depending on the degree of contamination of the substrate one-bath scouring and dyeing of grey , unset piece goods of textured yarns is possible.
If the material is highly stained with the spinning oils or other contaminants then it is advisable to give a soaping treatment with stain removing detergent at 75 0 C for about 15-20 min. Or it may be directly added to the dyebath along with the dyes and chemicals.

2.dye solubility ,dye dissolution, and dye selection.
3.material to liquor ratio.
4.dyeing temperature.
5.dyeing duration.
6.leveling and retarding agents.
7.dispersing agents.
8.removal of excess dyes from the fibers.
9.oligomers and their removal.
10.reduction clearing.
11.soaping treatment.
12.use of dyeing career.
13.correction of faulty dyeing.
14.stripping of the dyes.

Dyeing of polyester with disperse dyes

Dyeing of polyester 1( Dyeing of polyester fabric by exhaust dyeing)

Dyeing of polyester 2 (Dyeing of Polyester Fabric)

Dyeing of polyester 3(Dyeing of polyester fabric)

Dyeing of polyester 4(Polyester Printing)

Dyeing of polyester 5(Pretreatment of polyester Fabric)
Oligomers and polyester dyeing

What is Oligomer?

Oligomer is a smaller chain length of polyester made up of two or more molecules of basic ethylene terephthlate i.e. dimer or trimer, produced as a side reaction during the manufacture of polyester. The Oligoster because of its smaller chain length is in the form of a fine powder which is entrapped is basic polymer and migrates to the surface during high temperature polyster dyeing. Higher the depth more is the displacement of Oligomer to the fibre surface. Approximately 0.1 % 1.0 % of Oligomer is produced as a side reaction in the manufacture of basic polyester.

Problems caused by Oligomer deposits leading to unlevel dyeings.

• Filtration effect (inside - out variation) due to build up of Oligomers in package
• Improper pump pressure due to deposits on pump.
• Choking of spindle holes
• Varitation in rate of rise of temperature due to deposits on heating elements.
• Duller shades
• Dusting during coning
• Higher energy costs

Dyeing polyester with Foron dyes

Click Here for Problems and their remedies in Processing of Polyester

Click here for color variations in processing of spun polyester filament  

Neutral to acidic conditions advantageous in polyester deep-dyeing click here

Textile dyeing in supercritical carbon dioxide Click here

What is Trilobal polyester?

See Fiber Cross sections

Recent advances in fiber technology have resulted in a new type of polyester. In the past, due to its dull appearance, polyester lost out to other fibers, especially rayon. However, with the development of Trilobal polyester, rayon thread may become a thread of the past.

In manufacturing Trilobal polyester, the Trilobal cross section of the fibers creates excellent light reflection, resulting in high sheen. If the desired effect is durability, softness, and brightness, Trilobal poly is perfect for the job.

Following are characteristics of Trilobal poly.

1. Brightness. High sheen for attractive quilting and embroidery designs.
2. Strength. Stronger than rayon, which means fewer thread breaks. Polyester can be used at higher machine speeds than weaker threads, including rayon.

3. Colorfastness. Withstands chlorine. Durable to cleaning and laundering. More resistant to UV exposure than rayon.

4. Controlled elongation (stretch). Outperforms rayon and other polyester threads (such as spun poly).

5. Excellent wet strength. Does not weaken in washings.

6. Abrasion resistant. Higher abrasion resistance than rayon means it does not wear out as fast.

7. More stitch volume. Has a slight 3D effect with less need for underlay or cord. Perfect for satin stitches.

8. More resistant to chemical damage than rayon. Ideal for industrial work-wear garments.

9. More forgiving of poor adjustments or mechanical conditions of the machine.

10. Virtually lint free.

Modification of polyester Click Here

Texturised Yarns Click Here

Disperse Dyes

Chemical Nature

These are nonionic in nature.Disperse dyes are characterized by the absence of solubilizing groups and low molecular weight. From a chemical point of view more than 50 % of disperse dyes are simple azo compounds, about 25 % are anthraquinones and the rest are methine, nitro and naphthoquinone dyes.

General properties
Disperse dyes are supplied as powder and liquid products. Powder dyes contain 40 - 60 % of dispersing agents, while in liquid formulations the content of these substances is in the range of 10 - 30 %. Formaldehyde condensation products and ligninsulphonates are widely used for this purpose.
Classes of Disperse dyes
1.Low Energy(E type):-These dyes have low molecular weight ,low polarity , high dyeing rate and low sublimation fastness.
2.Medium Energy(SE type):- These dyes have moderate molecular weight, moderate polarity,moderate dyeing rate and moderate sublimation fastness.
3.High Energy(S type):- These dyes have high molecular weight ,high polarity , low dyeing rate and high sublimation.
Applicability
Disperse dyes are used mainly for polyester, but also for cellulose (acetate and triacetate), polyamide and acrylic fibres.
Dyeing Mechanism

The dye-fibre affinity is the result of different types of interactions:

· hydrogen bonds

· dipole-dipole interactions

· Van der Waals forces.

Disperse dyes have hydrogen atoms in their molecule, which are capable of forming hydrogen bonds with oxygen and nitrogen atoms on the fiber.

Dipole-dipole interactions result from the asymmetrical structure of the dye molecules, which makes possible electrostatic interactions between dipoles on the dye molecules and polarized bonds on the fiber.

Van der Waals forces take effect when the molecules of the fibre and colourant are aligned and close to each other. These forces are very important in polyester fibres because they can take effect between the aromatic groups of the fibre and those of the colourant.

Chemicals and auxiliaries required in disperse dyeing

pH buffers

Levelling and retarding agents see leveling agents

Dispersing agents

carreers

Reducing agents for reduction clearing

Important Dyeing Parameters

1.Pretreatment process.

2.Dye solubility ,dye dissolution, and dye selection.

3.Material to liquor ratio.

4.pH and Dyeing temperature.

5.Dyeing duration.

6.Leveling and retarding agents.

7.Dispersing agents.

8.Removal of excess dyes from the fibers.

9.Oligomers  and their removal.

10.Reduction clearing.

11.Soaping treatment.

12.Use of dyeing career.

FACTORS I N SELECTING DYES FOR POLYESTER
1.Economy
2.Fastness levels required.

3.Level Dyeing or Barre control.
4.Stability at high temperature.
5.Dispersion Stability (in package dyeing)

Fastness Properties(on polyester)
Light fastness:-Fastness to light is generally quite good.
Washing Fastness:-Fastness to washing is highly dependent on the fiber. In particular, in polyamides and acrylics they are used mostly for pastel shades because in dark shades they have limited build-up properties and poor wash fastness.
Sublimation Fastness
Depend upon the class of disperse dyes.
Crocking fastness

Good
Fastness to dryclean
Good
Fastness to Chemicals wash
The dyes may fade and loose color value if subjected to Chlorine bleaches in acidic medium.
An introduction to disperse dyes
All about Manufacturing of Disperse Dyes
Dyeing of Polyester -1
Dyeing of polyester -2
Dyeing of Polyester -3
Dyeing of Polyester -4
Dyeing of Polyester -5
Dyeing Procedure of disperse dyes