batch-to-batch shade variation

 

Question:

I am getting batch-to-batch shade variation (color variation) for the same reactive shade, in Soft Flow

dyeing machine. I am using the same manufacturer’s dyes and chemicals and almost same quality of

fabric. What are the reasons and how to avoid it?

Answer: 

Batch to batch shade variation is a general phenomena noticed almost everywhere in dye houses.

There are so many factors that affect a particular dyeing operation. Please make the following checks;

I hope you can eliminate 90 to 100% of the above problem.

Phase-1: Preparatory Stage.

Check the batch weight exactly for all batches. Find the exact GSM of the greige fabric and note down

on your job card.

After Scouring, Bleaching and neutralization, before dyeing, take a sample, dry it, condition it and

check the GSM.

Note down the difference in percentage as Scouring and bleaching loss on the job card. Compare this

loss% between each batch. It should not deviate more than 2 to 3%.

If deviation is there then the following may be the reasons:

Material to Liquor Ratio difference during scouring/bleaching.

Process timing difference

Temperature may be kept high or low.

Low or better quality of greige material, ie. Higher staple length good quality fiber loses less

weight rather than the poor quality short staple length fiber.

Alkali and Scouring auxiliaries’ concentration or quality may have changed.

Quality of water would have changed. Check for hardness, TDS and pH of water used in each

batch.

Check the whiteness index of the RFD fabric and note on the Job card.

Check the absorbency of RFD fabric and note on the job card. Let the test results be noted in

terms of seconds.

Check the remaining Core alkali in the fabric and the fabric pH.

Check for residual Peroxide on the fabric before dyeing.

Phase-2: Dyeing Stage.

Check the quality of input materials.

Dyestuff concentration to be checked drum to drum.

Cheque the quality of sequestering agents.

Check the quality of water – pH, hardness and turbidity.

Check personally while weighing the dyes and chemicals.

Check personally while dissolving the dyestuff, filtering the dyestuff solution and adding in to

the dye bath in to the machine.

Cheque the quality of Salt. Find out in advance how much hardness is increased in the dye

bath due to salt addition.

Counter the hardness due to salt with proper dosage of a good quality-sequestering agent.

Check the quality of Soda Ash. Check for purity percentage.

Allow the same number of minutes or hours to run dyeing with salt alone – e.g. if the first batch – salt

addition is done for exactly 30 minutes and after complete addition of salt, if the machine was allowed

to run for 30 minutes, before injecting the soda solution, please follow the same procedure. It has its

own effect in exhaustion percentage.

Similarly inject the soda in to the machine for the same length of time the first batch was done. If

injection time for the first batch was 30 minutes, do it for all subsequent batches for 30 minutes.

Allow running the batch for the same length of time in soda before raising temperature. If it is 20

minutes. Follow the same procedure for all batches.

Steam Raising time – if 60°C is reached in 20 minutes for the first batch – do it for 20 minutes for all

batches.

Run at Specified temperature for the same timings for all batches.

Cheque the pH of the dye bath every 30 minutes from the starting of dyeing and note it the job card.

After the final addition of Soda ash the pH should be 11 to 11.2. A well-calibrated good quality pH

meter will aid you in this job.

Record the final pH of dye bath after every 30 minutes. 

Maintain the water level same throughout the dyeing operation and make sure that your are

monitoring the level batch to batch.

Phase-3: Finishing:

Not only the preparation and dyeing operations are important, final finishing operation also is very

important to avoid batch-to-batch variation.

After draining the dye bath, do one cold wash and hot wash. Cold wash timings and hot wash timings

and temperature are also important. Note this in the job card. Do not take this finishing part as

unimportant. In fact here also there is every possibility to get shade variation.

a. If temperature and timing of each batch are not same the washing off will also not be the same.

Please maintain it.

Neutralize with Acetic acid. The quality of Acetic acid should be checked every time you get fresh lots.

Neutralize with the same quantity of accurately weighed Acetic acid volume. The final pH always

determines the tone of the shade. So quality of Acetic acid, quantity of acetic acid and the treatment

time are all-important and they should be identical between batches.

Soaping: 

Use good Quality Anionic Soap such as Lissopol D of ICI.

Before adding the soap in to the bath, fill the machine with adequate volume of water, run blank for 5

minutes, take out some water and check for TDS. Let the TDS be not more than 100ppm of original

water i.e before entering in to the machine.

If higher TDS observed is say 1000 ppm higher than original water, then it is understood that there is

still the high residual salt present in the fabric.

The higher residual salt content in the water would act as exhausting agent for the unfixed dyestuffs

and would not allow to come out from fabric, during soaping and impair the quality of soaping and

finally the washing fastness.

More over the properly not removed salt would result in a harsh feel of the finished fabric.

Higher dosages may sometimes cause white patches.

Maintain the timing, temperature; water level and dosage of soap, same for all soaping processes.

Check the Final pH of the fabric; let it be slightly acidic.

But in acidic pH condition the fabric should not be allowed to kept wet for long durations of say one

day or two days, because there is every possibility of formation of fungus over the processed material

that not only changes tone but also impairs the strength of fibers.

Final cationic fixing operation: Due to the presence of free formaldehyde in different dosages between

manufacturers, the final shade’s tone changes to bluer or yellowier side. Select the best product and

adhere to it. Do not change this product frequently for small cost benefits.

Final Cationic Softener Treatment: During this phase also there is every possibility of change in tone,

depth and light fastness of the final product. Purchase the best product and maintain the same for all

your production processes.

Finally the drying temperature. Same temperature and duration of exposure of the fabric is a must.

Over dried fabric and under dried fabric will show a lot of shade variation.

Machinery Problems for Shade variation:

Rope length should be maintained almost the same in all the loops.

Ensure that in each batch the fabric rope passes through the nozzle of the machine the same number

of times during the actual dyeing process.

A change in rope speed - depending on the batch size may be necessary to do this.

Use the same standard program procedures for each batch.

Clean the filter for each batch.

If nozzle diameter can be adjusted in your machine, keep the same diameter for getting the

reproducibility.

Conclusion: ‘Change is one that always remains changeless’ is true in all walks of life. Higher the

precautions lower the change.

at is APEO and what does APEO free mean? What are the bad effects due to the presence of APEO in

finished goods or effluent?

Alkylphenol ethoxylates(APEO) are nonylphenol compounds(NPEO). APEO are non-ionic surfactants

with an emulsifying and dispersing action, Which makes them suitable for very large variety of

applications.

At the processing stage, approx.50% of APEO are used as emulsifiers for emulsion polymers based on

styrol butadiene, Styrol acrylate, Pure acrylate or PVC systems.

Alkyl Phenol ethoxylates and especially Nonyl Phenol ethoxylates are considered to be very toxic for

aquatic life. In Europe these emulsifiers/surfactants are no loner allowed/wanted.

Description

Many surfactants give rise to environmental concerns due to their poor biodegradability, their toxicity

(including that of their metabolites) and their potential to act as endocrine disrupters.

Concerns currently focus on alkylphenol ethoxylates (APEO) and in particular on nonylphenol

ethoxylates (NPE), which are often contained in the formulations of detergents and many other

auxiliaries (e.g. dispersing agents, emulsifiers, spinning lubricants).

Alkylphenol ethoxylates are themselves believed to be endocrine disruptors and to cause feminization

of male fish. More importantly, however, they produce metabolites which are believed to be many

times more potent as endocrine disruptors than the parent compounds. The most potent of these are

octyl- and nonylphenol. Nonylphenol is listed as a priority hazardous substance under OSPAR and the

EC Water Framework Directive, which means that any discharge needs to be phased out.

Identification of alternatives to APEO 

With reference to the identified raw materials containing APEO contacts were established to the

producers in order to find out if they were able to supply the same raw materials without APEO. The

manufacturers have often developed APEO-free raw materials and these raw materials would be

possible substitutes in the actual products without or with few adjustments in the product formulation.

Technical testing of alternatives 

The technical testing of alternatives (APEO-free) raw materials or alternative surfactants is carried out

at the Beck & Jørgensen laboratory or at the laboratory at EnPro.

The selection of new binder systems is dependent on the technical properties that can be achieved in

the actual formulation. In the present project the aim is to replace four types of binders. In all four

cases the options were reduced to two after the testing. It is essential to point out that substitution of

the binder, which is the “backbone�? in the product, may require a number of adjustments or even

reformulation. The dispersion aids and the binder system must be compatible in order to avoid

flocculation. Replacement of the anti foaming agents may also be necessary to get the proper

functionality. This means that substitution of other raw materials can be necessary even if they do not

contain APEO.

As one binder is used throughout one product group it is not always possible to select the technically

best alternative, since the consequence might be that a number of new binders/raw materials have to

be introduced in the same product group.

The project demonstrated that it was (or would be) possible to substitute APEO and raw materials

containing APEO. The substitution may be a long process, as many raw materials with different

function have to work together. The aim was to remove APEO from the products and retain as much of

the original formulation as possible, since development of new formulations is a more comprehensive

time and resource consuming process.

The experience is that it is often impossible to get complete information about raw materials

containing surfactants in advance.

Health and environmental assessment of alternatives 

The health and environmental assessment was performed as a screening followed by a detailed

assessment of groups of substances selected on the basis of the results of the technical testing:

Sodium laurylsulfate 

Alkylether sulfate, sodium salt 

Ethoxylated linear fatty acid alcohol (alcohol ethoxylates) 

For comparison, the health and environmental aspects of APEO were presented. 

Question: After finishing all processes, a fabric was tested and found to contain some APEO traces and

the level of the APEO content present was not within the acceptable limits. Is there any proven method

to remove the APEO content?

There are two simple treatments one can try.

Do hot soaping using a real APEO free surfactant, followed by 2 hot and cold washes.

Treat at 70°C with Formic acid 2gms/liter for 30 minutes, followed by 2 hot and cold washes.

One of the above processes will surely remove the traces of APEO content.

ton and viscose blends are very difficult to dye in to a solid shade. What is the best thing one can do to

get a solid shade?

Answer:

Viscose has a very high affinity towards reactive dyes when compared to cotton cellulose. If one tries

to dye a solid shade out of this blend, he would certainly end up in dyeing a contrast shade, due to

differential dye pick up.

A simple pad-dry-cure pretreatment with a cationic dye fixing agent, with say 4~5 gpl, would make the

cotton cationized. This cationized cotton/viscose blend, when dyed with a reactive dyestuff would

result in a good solid shade.

Please take a small batch trial before doing any bulk processing.

 

No Soap Dyeing

 

Question:

Is soaping necessary after Reactive dyeing of cellulosic materials?

Answer:

Omitting the use of detergents in after washing of cotton dyed with reactive dyes:

Description

Both international literature and practical experience in textile mills show that detergents do not

improve removal of hydrolysed reactive dyestuffs from the fabric.

On the contrary, high temperatures do have an affect on rinsing effectiveness. Tests carried out with

rinsing at 90 - 95 °C have shown that rinsing is more effective and faster at high temperatures. About

30 % more unfixed hydrolysed reactive dyestuff is rinsed out after 10 minutes of rinsing at 95 °C than

at 75 °C.

Many dye houses already carry out hot rinsing and omit the use of detergents in rinsing after reactive

dyeing. The product quality is not negatively affected. On the contrary, most often the fastness of the

goods are better after the hot rinsing than after the traditional rinsing with detergents, complexing

agents and neutralisation in the first rinse.

Energy should be recovered when using large volumes of hot process water. Energy reclamation can

be done either by heat exchange between the hot outgoing process water and the cold incoming clean

water or by reclamation of the hot water and re-use of both energy and water.

Main achieved environmental benefits

The main benefit is the reduction in consumption of detergents and pollution load discharged to the

waste water. Obviously, the potential for reduction will vary according to the existing dyeing procedure

at the company.

The experience of two dye houses (one mainly dyeing knitted fabrics and the other dyeing garments)

shows that the average potential load reduction can be in the order of 1 kg detergent, 1 kg complexing

agent and 1 kg acetic acid per 100 kg of textile.

Additional advantages are the savings achievable in the amount of chemicals consumed to destroy

reactive dyes by free radical treatment processes. In the Fenton reaction for example since the OH*

radicals react very fast not only with the dyestuffs but also with many detergents, a large amount of

expensive H2O2 can be saved by omitting the use of detergents.

Operational data

The high degree of fixation and the excellent wash-off properties typical of some new low-salt,

polyfunctional reactive dyes are important factors that help obtain sufficient wash fastness with hot

rinsing without the need for detergents.

It has been reported that difficulties might arise with accidental stops of the machinery. In such

conditions the high temperature of the rinsing water could cause irreversible cleavage of the bond

between the reactive groups of the dye and the hydroxyl groups of cotton or viscose.

Applicability

A Danish textile mill has during the last 5 years totally omitted the use of detergents in the rinsing

process after reactive dyeing. The company treats knitted and woven goods made of cotton or

cotton/PES and dyes them in all colours and shades. The application of this technique may involve a

change in the type of dyes employed. The referenced company works with bifunctional reactive dyes

as Cibachron C or Bezaktiv S. Soft water is used.

Level dyeing in a jet with reactive dyes

 

Question:

What are some important points for achieving level dyeing in jet dyeing with reactive dyes?

Answer:

In jet dyeing, proper control of the exhaustion rate is achieved by,

-Incremental dosing of salt, simply 1/10, 2/10, 7/10, each in 10 min. intervals.

-In cheese dyeing machines or short -time dyeing cycle in jets, salt is added at once at the start of

dyeing before dyestuff. In this case, isothermal dyeing program is adopted, because a higher dyeing

temperature during primary exhaustion promotes the migration of dye.

-A proper leveling or migrating time should be elapsed after salt-dye addition. 30-45 min. interval is

required for proper leveling.

- pH of the dye bath should be around 6.5 in order to prevent fixation.

-Dosing of alkali should be controlled very precisely, especially in first 20 min. pH should not exceed 9.

So addition of soda ash as- 1/100, 1/10, 2/10. Rest at 10 min. intervals is recommended. If pH rises

very quickly, during first period, it is rather hard to improve un-leveling, especially in Blue R, Turkis G,

beige, gray and khaki shades, un-leveling is unavoidable

-Alkali should not be dosed over long period of time, because dye hydrolyzed and hence washing

fastness decreases

-Final approached pH should be around 11, if not, sodium hydroxide or liquid alkali can be supplied in

the last 10 min. intervial of soda dosing period.

-Always add soda and alkali in fresh water.

Creases on collar and Cuffs

 

Question:

In heavy-knit structures and flat-back rib structures like collars (especially mercerised collars), crease

marks can be noticed even after the addition of lubricants. This causes the formation of dark lines on

collars. How can this be prevented?

Answer:

Firstly, it should be ensured that the merceriser has not caused the creases. It is better to examine the

fabric for creases before dyeing. If merceriser creases are present, it would be prudent to re-mercerise

if the creases are mild, or divert to full bleach or pale shades that may not show up the creases.

Despite the lubricants, the fabric, being heavy, could form firm creases due to its own wet weight, and,

cause creasing during dyeing. The chances of creasing are also possible when passing through the

nozzle with inadequate diameter or if there is an imbalance in the liquor/fabric rope speeds.

The possible solutions are as follows:

Increasing material-liquor ratio in the soft flow should help in achieving better buoyancy to keep the

wet fabric separated and also under the dye liquor, thus reducing the propensity to form creases

As collars are usually flat-back and rib structures, the 'fabric bulk' is not a necessary feature as

compared to the body fabric. Therefore, they could be dyed on beams or pad batch/pad steam type of

dyeing systems, where the propensity to crease is low

Lubricants do help in smooth flow of the fabric through the system and, therefore, minimize abrasion

and fabric entanglement. Consequently, they help in reducing creases

Phenolic Yellowing

 

Question:

What is 'phenolic yellowing' and how is it influenced by acidic and alkaline conditions?

Answer:

Phenolic yellowing is caused due to the presence of phenolic compounds on the textile material,

reacting with the oxides of nitrogen in an alkaline medium. The phenomenon of phenolic yellowing is

associated with the storage of finished textile material, packed in polyethylene/aromatic polymer

material or cardboard cartons.

Aromatic amines (PPD-Para Phenylene Di-Amine) and phenolic compounds (BHT-Butylated Hydroxyl

Toluene) are increasingly used as anti-oxidants and stabilizers in organic polymer packaging materials,

lubricants and foam. These and the phenolic derivative from the lignin in cardboard form the yellowing

precursors.

Oxides of nitrogen are generated in warehouses/households from direct heating systems or from

automobile emissions in the urban environment. Neither the oxides of nitrogen nor the phenolic

compounds by themselves cause yellowing, but when united, form the yellowing products. The BHT or

the phenolic derivatives of lignin from the packing materials migrate to the surface and get transferred

to the textile material, which in turn, when exposed to the oxides of nitrogen in the ambient

atmosphere, cause yellowing.

Such situations are much more common in cold countries where the warehouses or households require

atmospheric heating and hence, resort to direct heating. Indirect heating systems would mitigate this

problem. Automotive emissions and propane burning-both sources of oxides of nitrogen-are most

prevalent in all urban ambience.

The alkaline condition that is required for the reaction between the phenol and oxides of nitrogen is

inherent in cotton textiles. This is because, the fabric is processed predominantly in an alkaline

medium and unless it is fully neutralized with specialty acids, it would tend to get alkaline while in

storage, and become more prone to yellowing. This is particularly true in case of whites.

Phenolic yellowing can be mitigated by the following methods: 

Avoidance of phenolic antioxidants and stabilizers in the packaging materials or in the synthetic

polymer fibres used in the blends

Rendering the finished textiles at a slightly acidic pH (neutralization with specialty acids)

Avoiding exposure to oxides of nitrogen pollution 

Water Marks found in 100% Cotton:

 

Question:

Suggestion for removing the water mark before processing:

Answer:

Suggestion for removing the water mark before processing:

In grey unprocessed stage if cotton fabric is exposed to water spotting when it is in pile form and if it is

not noticed before taking for processing, a big head ache will land up with the processing people.

Fabric taken for desize, mercerise, bleach and dye would show irregular shaped patches in the

processed fabric.

This is may be due to either fungus formation on the wet areas or partial removal of size due to

bacterial action under moist conditions. Whatever it may be, these patches would appear prominent

only after dyeing or bleaching (OBA treated).

Mostly these patches your would come across during rainy season or while processing a fabric that

was stored for very long time. If you are lucky enough to take processing in batch mode, you can very

well eliminate the patches fro the next batch on wards.

Instead of going for peroxide bleach or mercerisation after desizing, you take the fabric directly for

hypo bleaching. No extra alkali should be present during this process, except a wetting agent and

sodium hypochlorite. After this process, you can take any route according to your necessity. Now you

would not find any water mark in the processed fabric.

Always prevention is better than cure. So when storing the fabric is a ware house, always keep it

closed with a polythene sheet to avoid these type of mystic problems, that you can notice only after

damaging sufficient quantity of fabric.

Suggestion for removing the water mark before processing:

(1) If the fabric is in mercerised stage, try a hypo bleach, followed by peroxide bleaching. 

(2) If the fabric is in dyed stage, you have to convert the dyed shade either in to a jet black (sulphur

black) or some very dark shade and go for fresh lot.

 

How to remove mildew from fabric?

 

Question:

How to remove mildew from fabrics?: 

Answer:

Appearance of mildew or fungus on moist natural fabrics or yarn is a common defect that may be

noticed before processing if the mildew degradation of fabric is prominent. In the beginning stage the

mildew appears as pale yellow spots and slowly this yellow spots mature in to page green, then blue or

violet and finally in to dark black spots.

Mildew can be effectively removed by dilute hypochlorite treatment on the affected area.

If the fabric is a dyed one, spot the fabric on the unaffected area with dilute hypochlorite solution.

Check for change or destruction of shade. If it does not happen, you can treat the fabric on any batch

processing machine with dilute 1 to 2 gram per liter of Sodium Hypochlorite.

On the other hand, if the fabric is a greige or white, you can go for a hypochlorite bleach followed by a

peroxide bleach.

To avoid mildew formation during storage of wet fabric ( while in processing), at no stage keep it wet

under mild acid conditions. The acidic pH and wet condition, favor the bacterial action. Keep all wet

fabric under perfect neutral or slightly alkaline pH and avoid bacterial action.

For further reading on this topic:

http://fungus.org.uk/nwfg/rot.htm

Right procedure for Reactive Turq Blue Dyeing

 

Question:

What is the right procedure for dyeing cotton fabric/yarn in to a Turquoise Blue Shade? I faced with too

much of bleeding even after cationic fixing !

Answer:

Process Recipe conditions Remarks

Pretreatment:

Demineralization:

Lufibrol MSD -0.5 g/l

Kierlon JET B con - 0.5 g/l

For 20 minutes

@ 50°C

Hot Wash For 10 minutes

@ 50°C

Scouring &

Bleaching

Caustic Soda = 0.7% or 1.0

g/p (for softflow)

Soda Ash = 3.0 g/l (only for

yarn in HT/HP)

Stabilizer = 0.5 g/l  

Soap (Anionic) = 0.5 g/l

Hydrogen Peroxide = 2.0 g/l

For 45 minutes

@ 85°C

Do not use soda ash

for fabric bleaching.

Core neutalization is

a problem if we use

more alkali. The

optimum qty is only

0.7%.

Do not use Caustic

soda for yarn

bleaching - the yarn

package will shrink

too much and

penetration will be

affected.

Hot Wash For 10 minutes

@ 50°C

Residual Peroxide

Removal:

Peroxide Killer(enzyme) = 0.25

g/l

Acetic Acid = 1.5 g/l

For 10 minutes

@ 50°CCheck pH = 6

Cold Wash

Dye Bath Setup: Resist Salt = 1 g/l

Sod.Hexametaphosphate = 1

g/l

Soda Ash = 2 g/l

For 10 minutes

at 50°C

Sharpening treatment

Dyestuff Addition Add predissolved & filtered

dyestuff in 2 portions

Raise

Temperature to

85°C and run

10 minutes

1st Salt addition Add 1/10 of total Glaubers Salt Run 10 minutes

@ 85°C

2nd Salt Addition Add 2/10 of total Glaubers Salt Run 10 minutes

@ 85°C

3rd Salt Addition Add 7/10 of total Glaubers Salt Run 20 minutes

@ 85°C

Note: (if the dyestuff

combination contain V.S or Bi-

functional dyes  reduce

temperature to 60°C)

1st Soda Addition Add 9 gms/liter of Soda Ash Run for 10

minutes

2nd Soda Addition Add 9 gms/liter of Soda Ash Run for 10

minutes

Note: (if the dyestuff

combination contain V.S or Bi-

functional dyes   continue

dyeing at 60°C for 30 minutes)

Raise

temperature to

85°C and run

for 30 to 45

minutes.

Do tonal corrections if

necessary at this stage.

Drain - overflow cold

wash

Neutralization Acetic Acid = 1 g/l at cold for 10

minutes

Hot Wash at 75°C for 2

cycles

1st Soaping Lissopol D paste or Dekol SN

or Sandopur RSK liquid = 2 g/l

at 95°C for 20

minutesDrain

2nd Soaping Lissopol D paste or Dekol SN

or Sandopur RSK liquid = 1 g/l

at 95°C for 20

minutesDrain

Hot Wash at 50°C for 10

minutes

Cold Wash overflow

Final pH setup Acetic Acid = 1 g/l at cold for 10

minutesdrain and unload.

ow Temperature dyeing of T.Blue dyes.

 

Question:

Is there any method to dye Turquoise Blue shades to dye at 60°C or less?

Answer:

Yes you may dye Reactive Turquoise Blue G and H2GP combinations with VS or Bifunctional dyes at a

lower temperature using the preconditioning method of dyeing.

In fact this method of dyeing yields unprectable higher depth and fastness proeperties. You will surly

get at least 20% extra yield in dyeing depth.

Please see the table below for procedure and recipe: (Let us consider that the total combination % is

more tha 4% o.w.f.)

Fabric (Knit/woven) or yarn preparation: (Unmercerised)

Process Recipe conditions Remarks

Pretreatment:

Demineralization:

Lufibrol MSD -0.5 g/l

Kierlon JET B con - 0.5 g/l

For 20 minutes @ 50°C

Hot Wash For 10 minutes @ 50°C

Scouring & Bleaching Soda Ash = 3.0 g/l

Stabilizer = 0.5 g/l  

Soap (Anionic) = 0.5 g/l

For 45 minutes @ 85°C

Hydrogen Peroxide = 2.0 g/l

Hot Wash For 10 minutes @ 50°C

Residual Peroxide

Removal:

Peroxide Killer(enzyme) =

0.25 g/l

Acetic Acid = 1.5 g/l

For 10 minutes @ 50°C

Check pH = 6

Cold Wash

Dye Bath Setup:

First 1/2 Salt Addition

Resist Salt = 1 g/l

Sod.Hexametaphosphate = 1

g/l

Glauber's Salt = 40

grams/liter

For 10 minutes room

temperature.

Second 1/2 Salt add. Glauber's Salt = 40

grams/liter

For 10 minutes room

temperature.

First 1/2 Soda add. Soda Ash = 5 grams/liter For 10 minutes room

temperature.

Second 1/2 soda add Soda Ash = 5 grams/liter For 10 minutes room

temperature.

First 1/4 caustic add Caustic Soda = 1.5 grams/liter For 10 minutes room

temperature.

 

 

Second 1/4 caustic

add

Caustic Soda = 1.5 grams/liter For 10 minutes room

temperature.

1st 1/2 dyestuff Add 1/2 of total dissolved dye Run for 10 minutes at

room temperature

For dissolving use

1:15 LR @ 70°C

2nd 1/2 dyestuff Add 1/2 of balance dissolved

dyestuff.

Run for 10 minutes at

room tempetature.

Temperaure setting Raise temperature to

40°C if the combination

contain any VS or

Bifunctional dye else

raise the temperature to

60°C . Run for 10

minutes

Third 1/4 caustic add Caustic Soda = 1.5 grams/liter Run 10 minutes at the

above temp.

Fourth 1/4 caustic

add

Caustic Soda = 1.5 grams/liter Run 10 minutes at the

above temp.

1st dyeing Time Temperature 40°C If your combination

contain VS or

Bifunctional dyestuffs,

then continue dyeing for

30 minutes.

This is for allowing

VS and Bifuntional

dyes to get fixed to

the fiber.

2nd dyeing time Temperature 60°C Continue dyeing for 60

to 90 minutes at this

temperaue.

Drain - overflow cold

wash

Neutralization Acetic Acid = 1 g/l at cold for 10 minutes

Hot Wash at 75°C for 2 cycles

1st Soaping Lissopol D paste or Dekol SN

or Sandopur RSK liquid = 2 g/l

at 95°C for 20 minutesDrain

2nd Soaping Lissopol D paste or Dekol SN

or Sandopur RSK liquid = 1 g/l

at 95°C for 20 minutesDrain

Hot Wash at 50°C for 10 minutes

Cold Wash overflow

Final pH setup Acetic Acid = 1 g/l at cold for 10 minutes drain and unload.

Disperse Blue SR dyeing

 

Question:

Please suggest a dying method to avoid speckyness/leveling problems in conc. dyes. Such as Blue

SE2RI/Blue SR/N. Blue EXP

Answer:

POLYESTER DYEING WITHBlue SE2RL/Blue SR/N.Blue EXP

Almost all Blues and especially Navy Blue’s, are very sensitive to pH change. These dyestuffs require a

minimum pH of 4.5 to 5, throughout the dyeing process; otherwise patchy and specky dyeing would

invariable be the end result.

The following dyeing recipe and procedure will do away with the above problems.

Recipe:

Blue dyestuff = x %

Invadine TOP = 1 gpl (anionic dispersing & leveling agent – BASF)

Formic Acid = 0.25 gpl

Ammonium Sulphate = 1.0 gpl

Procedure:

Start dyeing by first adding all the chemicals and auxiliary at 50°C and run 1 cycle (10 minutes)

Add dissolved dyestuff solution and run 10 minutes at 50°C

Raise temperature to 115°C @ 2°C/minute

From 115°C to 135°C (for blacks 140°C) raise temperature @ 0.5°C/minute

Run at 135°C for 30 to 45 minutes (for black at 140°C for 45 to 60 minutes).

Cool down to 80°C and then drain

No washing – Fill water and add

Cylclonon ECO (BASF) = 2 gpl

Acetic Acid = 2 gpl

Start at 50°C and raise temperature to 80°C @ 3°C/minute

Run at 80°C for 15 minutes

Drain

Cold wash

Unload the batch

The above procedure may be used for all disperse dyeing to avoid problems that may occur time to

time.

Summer prcoessing problems & solutions

 

 

Drying up of water sources such as ponds, lakes and even dams are taking place during this season

due to the high temperature rises we experience year after year.

The drying makes the water sources to acquire high TDS levels and increased levels of hardness. Even

river water during this season used to have higher levels of TDS and hardness.

This hardness and TDS impart so many dyeing and bleaching problems.

The white precipitate of hardness that occur on the fabric or yarn during alkaline treatments such as

scouring, bleaching and dyeing produces various quality oriented problems such as dusting, un level

dyeing, low colour yield, less brightness, lower whiteness levels, poor rubbing fastness and nil

reproducibility of batches.

So be cautious during this season and try to use good quality of water by increasing your water-

softening-plant capacity or by judicial inclusion of a good sequestering agent in the alkaline treatment

baths.

Some Useful Tips :

1.A good pretreatment always results in good results. A thorough scouring, bleaching and

neutralization of fabric and a good absorbency are essential criterions for a good pretreatment. The

RFD (Ready For Dyeing) stage fabric/yarn should be uniformly white, absorbent and free from residual

alkali, chlorine, Hydrogen peroxide.

2. The dyeing starting may be done at a pH between 5.5 and 6.5.

3. No mixture of classes of dyes should be done viz., Cold brands & Hot brands or Vinyl-sulphones (V.S)

and Bifunctional (ME) or High Exhaust (HE) and Bifunctional (ME) and so on.

3. Avoid using Calcium hypochlorite for bleaching. Better use Sodium hypochlorite. Use appropriate

anti-chlor treatments to remove the residual chlorine from the fabric. Check for residual chlorine using

special indicator solutions available in the market or with an acidified Potassium Iodide solution.

Thorough washing is essential to remove the remaining anti-chlor chemical from the fabric.

4. While dyeing pale and critical shades, after peroxide bleaching, proper peroxide killer should be

used to remove all the residual peroxide from the fabric. All blues and turquoise blues are very

sensitive and prone to get oxidized leaving behind colorless chromospheres.

5. All dark shades should be soaped thoroughly using a neutral soaping agent.

6. After dyeing run a cold wash followed by neutralization and two or three warm washes to remove

the salt from the fabric. If soaping is attempted without removing the salt, a partial stripping will take

place resulting in poor dept

7. No cationic fixing treatment is necessary if good soaping and proper washings are carried out in

good quality water.

8. The tonal changes during compacting in the case of knits, take place mainly due to the destruction

of chromospheres of the dye molecule by the fixing agents used. So avoid using cationic urea

formaldehyde or melamine formaldehyde fixing agents. A simple softening treatment with a good

silicone softener yields good softness and crocking fastness.

9. Make proper selection of dyestuff mixture, according to the shade, depth, machine availability,

environmental shortfalls etc and lastly by economy.

Precautions in dyestuff dissolution:

There are so many simple but important hints that would be floating among the experienced dyeing

managers. Those pivotal points can be shared among the audience here to benefit your colleagues.

The dissolving and careful dispensing of dyestuff is a crucial step, which determine the colour yield,

repeatability and lab to bulk reproducibility.

For a tri-chromatic combination, the individual dyestuff in the combination should be weighed and put

into separate three containers. Each dye should be dissolved separately using 1:15 M: L ratio i.e., for 1

kg of dye 15 liters of water should be used. First the dye should be thoroughly pasted into a uniform

colloidal mass with a little cold water. Then dilute with hot water (80°C ) while continuously stirring.

Filter through fine bolting cloth and the mix the three dye solutions.

Do not add urea directly to the solid dye powder. If a large quantity of dyestuff is dissolved, add 1/10th

by weight of urea, to improve dissolution.

Turq Blue H2GP and Turq Blue G should be dissolved only with warm water ( temperature should not

be more than 60°C; otherwise very hot water would produce lumps and oil like products separation

may occur). This oily mass would create turq blue dark speck marks here and there.

Turquoise Blue G and Turquoise Blue H2GP combinations:

Do not use non-ionic detergents, wetting agents, dispersing agent in the pretreatment of fabric.

Similarly do not use non-ionic products during dyeing.

Use of sequestering agents do not have any detrimental effect on the dyeing of metal complex

dyestuffs like Turquoise Blue G, Turquoise Blue H2GP or Blue R spl. A neutral to alkaline pH stable

sequestering agents are preferable.

Do not use common salt or vacuum salt. Use only Glauber’s salt.

Do not use Caustic Soda for fixation.

Use of TSP (Tri Sodium Phosphate) in place of Soda Ash gives better color yield and fastness.

Better color yield and fixation is obtained only at 85°C. While dyeing combinations with vinyl-sulphone,

dye at 60°C for ½ to ¾ hour and then raise the temp to 85°C and dye for another ½ hour to fix the

turquoise blue.

While dyeing pale shades using these dyes, take care to eliminate the residual peroxide, which will

result in uneven dyeing.

Ensure thorough soaping before doing any cationic fixing treatment.

Do not unload the batch from the machine if proper cationic fixing is not done. Sometimes the unfixed

residual dyes that migrate with water may form drip marks on the fabric.

Refer: Turquise Blue Dyeing Procedure:

Sampling/Shading/Addition of Dyes during dyeing:

1. Do not compare any sample taken just after the addition of salt against the standard shade. This will

mislead you.

2. Take sample, 30 minutes after the addition of soda for light & medium shades and 45 minutes for

dark and very dark shades.

3. Wash Cold- ½ minute

4. Wash Hot – 60°C- ½ minute

5. Neutralize – cold- ½ minute with 1 g/l acetic acid.

6. Neutral soap – boil – ½ minute

7. Neutral soap – boil – ½ minute

8. For dark and very dark shades, do 6 soaps of ½ minute duration.

9. Cold wash.

10. Check shade.

11. If shade is not matching, and if you want to make 10 or 20 or 30% addition in total, drain the

running bath up to ½ volume, refill with fresh water, then add the required dye (pre-dissolved, filtered)

in two portions, continue dyeing for another ½ hour. Do not make any addition of salt or soda into the

bath.

After Treatments:

After dyeing is over, drain the bath.

Do one cold wash – no running bath.

Do one hot wash -- 60°C – 10 minutes.

Do neutralization with 1 to 2 g/l of Acetic Acid.

Do one cold wash.

Neutral soap 0.5 to 1.0 g/l at 80 to 90°C for 15 minutes.

Hot wash at 80°C – 10 minutes.

Cold wash – 10 minutes.

Softening treatment with some non-ionic softener.

Fabric Faults Created During Dyeing - With Respect to Soft Flow Dying:

Cockling: using a larger diameter nozzle, increasing the liquor ratio and reducing the fabric speed can

generally eliminate Cockling or Dimpling of the fabric. However in the case of heat sensitive or

thermoplastic fabrics, care should be taken to arrive at a “compromise speed�?. As running the

material at too low a speed during cooling, will also cause cockling.

Crack, Rope and Running marks: Running marks are frequently related to material’s construction, and

are caused by poor opening of the fabric rope. They can be avoided by either presetting or pre-

relaxation of the fabric before dyeing.

Running and crack marks can also be a result of incorrect process procedures.

A high fabric speed, combined with slower rates of rinse and cooling will often correct the problem.

Reducing the machine load and running at a slightly higher nozzle pressure, or using the next largest

available nozzle size, may also help.

Cloudy Dyeing: Inadequate pretreatment is the reason. Check your pretreatment cycle.

Too much foam in the dye-bath: Use de-foamers.

Pale areas: Inadequate pretreatment.

Deviation of shade: Dye sensitivity to hydrolysis, reduction, electrolyte concentration – to check all

these parameters. Select dyes carefully. Pay attention to stability of dye to the electrolytes (salt), dye

sensitivity to metal ions in the dye-bath (use suitable sequestering agents).

Precipitation in the Dye-bath: Pay attention to chemicals in the dye-bath

 

ere are possible occasions arise for the correction of the dyed shade. According the substrate(fabric/yarn)quality and the dyestuff used for dyeing, the following methods may be considered useful:

A) Cellulose:

1) Direct dyes are best removed by an alkaline reduction strip. Somedyestuffs may require a non-ionic boil off.

2) Vat dyes are very difficult to remove, usually a strong reduction stripwith caustic and hydros and strong organic stripping agent (leveling/dispersing agents).are required. Mostly the treatment has to be done at 80°C or more.

3) Sulfur dyes can be removed partially in depth by treating the fabric with sodium sulfide at 80°C or with caustic and hydros. You can make a judicialcombination of 2 treatments to strip off maximum color by treating thefabric with sodium hypochlorite 3 to 5 g/l followed by a reduction stripwith caustic and hydros.

4) Naphthols: Either oxidizing agents (hypo) or reducing agent wouldwork as stripping agents. But case to case this would defer. Lab trial is essential before finalizing anything on bulk treatment.

5) Reactive: Either hypochlorite or hydros or caustic hydros would work. Before doing bulk stripping one has to test the suitability. Most2 treatments are required. Hypo treatment followed by caustic hydros orCaustic hydros treatment followed by hypo treatment would work.

B) Polyamide (nylon) stripping:

A reduction stripping in alkaline medium with a non-ionic dispresing agentyields better result.

Light shades may be stripped by a mild boil off in the presence ofa non-ionic dispersing agent.

Deep shades and pre-metalized dyes may be stripped by an oxidizingbleach with sodium chlorite in acid medium.

C) Polyester:

Disperse dyes may be stripped by boiling off with a suitable carrierand dispersing agent.

Azo type disperse dyes may be stripped off by reduction method (causticand hydros).

couring : The scouring of polyester fabric mainly depends on the type of sizing agents used on the

yarn. Flat polyesterfilament fabrics are commonly scoured to remove sizes and lubricants, after

spotting

(if necessary) to assist the removal of loom stains. The preferable condition for scouring of polyester in

alkaline reagents (caustic soda, soda-ash, ammonium hydroxide) is about 2 g/1 with a treatment time

of 30-60 min at a temperature of 75-80~ Alternatively, scouring can be carried out with anion active

detergents in

an amount 1-2 g/1 at 80-95~ for 20-30 min.

Special precaution is necessary when polyester is scoured with strong alkali at higher temperatures

and care has to be taken not to hydrolyse the fibre.

Acid aftertreatment : The material to be dyed should exhibit a weakly acid (pH 6 to 6.5) or at

least a neutral reaction.

Drying : Only if the piece goods are set before dyeing. PES/VVo blends are not dried before

presettting if this is to take place on the crabbing machine.

Presetting : This is usually carried out before dyeing but after pretreatment so that no impurities

are fixed in the material. VVhether presetting is necessary depends on the quality of the material.

The conditions to be selected for presetting (temperature and time) should be determined

according to the available machines and the recommen-dations of the fibre producer. PES/VVo

blends can be preset on the crabbing machine or a stenter.

Singeing, shearing : After dyeing, the goods are sheared and singed (except PES/Wo),

depending on their quality.

Polyester Dyeing

Polyester Dyeing:

Exhaust dyeingDyeing 100% polyesterWhen dyeing with disperse dyes the levelness of the dyeing is determined by thedispersion stability, rate of dyeing and migration. An increase in migration demandslonger dyeing times. The rate of dyeing and therefore the heating rate must be controlledin such a way that the dyeing is level from the beginning by means of controlledadsorption.Pretreatment of the goodsThe material usually contains small amounts of water-soluble or emulsifiable preparationswhich can be readily washed off. With tops, loose fibres and smooth or textured yarnsrinsing for IO 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.

At the start of the dyeing process rinse the grey goods for 5 min at 20-30°C, then drainand add 1-2 ml/l Sandopan LFW Liquid to the fresh bath. On reaching 60°C add the otherchemicals and continue dyeing according to the programme shown below:

Dyeing under HT conditions (130°C)

Form of the goods- loose fibres and tops- yarn- piece goods (jet, overflow and beam dyeing machine)

Dye selection : Foron RD or S, SE and E dyes depending on the fastness require-ments

for the subsequent operations or for the final article.

Funtion AdditionProduct and amount

pH control essential

dispersantadvisable; Exception: sometimeswith very deep shades (black)

Levelling agentif required (substrate/form,machine, shade)

Carrier or dyeing accelerantif required (Substrate/form,machine, shade)

Anticreasing agentsrecommended on jet and overflowmachines

Remarks on dyebath additions- Dyeing on partially flooded HT dyeing machinesFoam formation during dyeing in these machines causes considerable problems so low foaming chemicals must be used.

Standard HT dyeing programme for 100% PES- set dyebath at 60°C- add dyebath additions and run for 10 min- add dye and run for 10 min- heat to 130°C at 1.5°C/min- fix for x min at the dyeing temperature as shown in table below- cool, drain, rinse, aftertreat.

Fixation times under HT conditions

The fixation times generally depend on the fixation temperature, depth and quality of the material. The Foron RD dyes exhaust on tone onto the fibre during the heating up phase and the dyebaths exhaust rapidly and completely on reaching the final temperature of 125-135°C.As a result the fixation times can be shortened compared to the Foron S, SE and E dyes.

Guide values for average dyeing PES qualities with Foron RD dyes:

DepthFixation time @125 deg C

Fixation time @130 deg C

Fixation time @135 deg C

Pale 0-10 minutes 0-5 minutes 0 minutes

Medium 5-15 minutes 5-10 minutes 5 minutes

Dark 10-20 minutes 10-15 minutes 10 minutes

V.Dark 20-30 minutes 20 minutes 10-15 minutes

The Foron S, SE and E dyes usually require 20-40 min longer than the Foron RD dyes atthe same temperature.

Cooling and draining the dyebath- Loose fibres, tops, yarn : After dyeing the bath should not be cooled below 90°C due tocrystallization of the oligomers, but drained hot- Piece goods on jet and overflow machines : After dyeing cool slowly (1-3°C/min) to80°C, then drain and rinse.

Polyester Dyeing:

Definition of microfibres

In a broad sense, especially in Europe, the term microfibre means fine fibres of less than 1 denier.

However, in Japan, where fibre technology is more advanced, fine fibres of 0.04 - 0.4 denier class are

generally used in this filament area(1). Most microfibre is made of polyester; however, other polymers

are used, including nylon, polyacrylonitrile, polypropylene, cellulose, acetate, and rayon. Mixtures of

polymers such as polyester-nylon and polyester-polypropylene are also used.

As shown in Figure 1, comparatively, microfibres are ten times finer than silk, up to thirty times finer

than cotton, forty times finer than wool, and one hundred times finer than a human hair. Generally,

fibre producer use such term as: >7.0 dtex for coarse fibres; 7.0 to 2.4 dtex for medium fine and

normal fibres; 2.4 to 1.0 dtex for fine fibres; 1.0 to 0.3 dtex for microfibre; and < 0.3 dtex for super,

ultrafine microfibres.

Microfibres less than half size of the finest silk are now available commercially and furthermore

microfibres as small as 0.001 dpf are produced by Toray of Japan .

Processing of microfibres

In spun yarn applications, microdenier fibres can be used to enhance the quality and process

performance of the yarn, and the functional and aesthetic properties of the fabrics made from these

yarns . Because of the delicate nature of the fibres, processing difficulties are likely to occur due to

fibre damage and nep formation at carding. Also the increase in number of fibres in the cross-section

results in higher frictional forces, which can cause problems during drafting.

Dyeing properties

It is well-known that as the diameter of the individual fibrils becomes smaller, or as the denier

decreases, the total surface area of the fibre increases exponentially. This results in a paler

appearance for microfibres than for higher denier fibres when both fibre types are dye with same

amount of dye. A greater amount of dye is needed for microfibres to reach the same depth of shade as

higher denier fibres.

The increased total surface area of the microfibre also affects the fastness performance after heat

setting. Unfixed dye on the surface of the fibre at the end of the dyeing process reduces the wet

fastness. Even though the unfixed dye can be completely removed from the fibre surface, a through

reduction clearing treatment problems may occur with subsequent finishing treatment. The larger

amount of dye needed for microfibres results in greater migration to the fibre surface by

thermomigration than occurs with conventional polyester, leading to lower wash fastness.

The following precautions should therefore be taken when dyeing microfibres:

• Dyeing machines should be set at a higher fabric speed (250 m/min at least).

• Ensure that the fabric rope is plaited down evenly.

• Add rope crease inhibitor to prevent creasing.

• Prevent the fabric from sticking during the dyeing process.

• Reduce the standard temperature (approximately 60 - 70°C).

• Optimum dyestuff selection (identical affinity).

It was reported that the small radius of microfibres causes many problems with the dyeing process and

colour fastness of dyed fabrics. The effect of a stagnant solution layer surrounding the fibre on the

dyeing rate is greater when dyeing microfibres. Therefore, an even flow rate of dye liquor through the

fibre assemblies is apt to cause uneven dyeing. It was noticed that the visual shade depth of textiles

decreases with decreasing fibre radius. Studies on the relation between the amount of dye on the fibre

and the visual colour depth and the end-use fastness properties of the microfibres have been

published. It was shown that microfibres dyed with disperse dye attain sorption equilibrium in a short

time, even blow 100°C, which has enabled the researchers to determine the sorption isotherms and

the kinetic data of dyeing very accurately.

Dye consumption for dyeing fibres of different fineness is shown in Table 2. The percentage dye

consumption figures in this table were calculated using the fothergill rule. A level of 1.0% disperse dye

on a 4 dtex per filament polyester fibre was used as a control and the subsequent dye percentages

were calculated to give an equal visual depth of shade on the fibre filaments.

Properties of microfibres and microfibre fabrics

Aesthetically, microfibre has a very soft and luxurious hand, with a silken or suede touch, as well as

excellent drapeability. From a performance point of view, microfibre is easy to care for, strong,

durable, wrinkle resistant, shrink resistant, water repellent, and wind resistant.

Microfibre fabrics are generally lightweight, resilient or resist wrinkling, have a luxurious drape and

body, retain shape, and resist pilling. Also, they are relatively strong and durable in relation to other

fabrics of similar weight.

Because microfibres are so fine, many fibres can be packed together very tightly. Thus, the fineness of

the microfibres produces so dense a fabric structure that the garment are wind and waterproof but

also air and water vapour permeable at the same time.

Polyester Dyeing- problems & Solutions:

Some reasons for unlevel dyeing:

Highly pH sensitive disperse dyes – almost all navy’s and blacks

Too much loading

Liquor Circulation problems

Improper heat setting/no heat setting

Too less quantity of Leveling /dispersing agent

Inadequate quantity of Acetic/Formic acid (please check acid concentration- acetic acid is

being manufactured from different sources.) pH plays a major role in disperse dyeing levelness

– take care.

Other Defects noticed in polyester dyeing:

Moire Effect on PC or PV – woven/knitted:

A watered, clouded, or frosted wavy appearance produced upon either woven or knitted textile fabrics

is said to be moiré effect.

The moiré effect is caused mainly due to the differential shrinkage of polyester and cotton or viscose

at high temperature and high pressure dyeing. This problem can be avoided by taking proper

precautions before and after dyeing.

1. A perfect head setting on pins at a temperature of 200 to 2100C for 30 to 45 seconds with an

over feed of 6 to 8% may be done.

2. In case of PV blends, caustizisation with 10 to 120TW of caustic soda at room temperature 

may minimize moiré effect.

3. Moire effect after dyeing may be corrected either by caustizisation or treating the fabric with 3

to 5 gpl of carrier at 1300C for 30 minutes in a jet or soft-flow machine.

4. This can also be corrected by subjecting the fabric to high temperature at 2000C with an over

feed  of 6 to 7% and redye in HT + HP machine using 10% of disperse dye recipe for 30

minutes.

Poor Sublimation Fastness:

Some of the disperse dyes tend to crystallize while cooling down the exhausted bath from

1350C to 800C. 1000C is the most critical temperature at which some of the red disperse dyes

( C.I.No. 53, 60, 131, 132 and 159) give problem of crystallization when they are dyed at

higher depths and especially if the dyeing is carried out in hard water. The hardness of water

should be nil for disperse dyeing.

Some of the disperse dyes are very sensitive to metal ions and shade changes considerably

bluer to duller side. Spinning assistants, spinning oils, alkaline residues and other factors cause

crystallization of disperse dyes to produce dye specks. This problem may be solved by proper

pretreatment.

The chromophore of the azo based disperse dyes is reduced and become soluble when an

alkaline reducing agent (caustic & hydros) at 60C thus promoting poor sublimation and rubbing

fastness

Na2SO4 + 2 H2O -------à 2H + 2NaHSO3

(alkaline condition)

-N=N-  + 4H --------à -NH2-NH2- (soluble disperse dye)

Azo dye

Use of non-ionic auxiliaries in the dye bath may also tend to aggregate some of the disperse

dyes causing poor sublimation and rubbing fastness.

In a 1:1 water and N’N-Dimethylformamide (CH3CONHCH3) [50 ML WATER, 50 ML

DIMETHYLFORMAMIDE] solution the dyed  POLY/COT SAMPLE is immersed for sometime; if the

color bleeds then poor sublimation fastness is confirmed. This can again be ascertained by

subjecting the sample specimen stitched along with multi fiber test fabric; moistened and then

ironed with a hot iron at 1800C for 30 seconds. If the multifiber fabric has got stained, it is

again confirmed that the dyed sample has poor rubbing and sublimation fastness.

These problems can be overcome by using the following recipe:

Disperse dye = x %

Acetic acid = 1.0 gpl

Sodium Acetate = 0.5 gpl

Anionic dispersing agent = 1.0 gpl

Or

Disperse dye = x %

Formic acid = 0.35 to 0.5 gpl

Ammonium Sulphate = 1.0 gpl

Anionic dispersing agent = 1.0 gpl

Dye Specks:

Dyeing auxiliaries like carrier, leveling agents (non-ionic) are liable to nullify the effect and impair the

solubilizing effect of dispersing agents thus promoting aggregation and agglomeration of disperse dyes

causing specks.

Also use of non-ionic silicones during final finishing tend to aggregate disperse dye and reactive dyes;

reduces the sublimation /rubbing fastness of the dyed fabric.

Non-ionic products in the form of wetting, leveling and finishing agents may be curtailed to avoid these

problems.

Pilling:

Factors responsible for pilling:

Fiber Characteristics such as morphological, chemical and fine structure of the fiber, fiber

length, fineness, strength etc.

Yarn Characteristics – viz., blend, count, twist, hairiness

Fabric Characteristics – such as weave, ends and picks etc.

Frictional and abrasive force – such as linear or rotational rubbing forces encountered during

wear or processing.

Remedies:

Surface treatment: The protruding fibres from the yarn or fabric can be removed

mechanically/chemically or by burning out or cropping, surface carbonizing, singeing, heat

setting etc reduces pilling.

Steaming & cropping: the loose projecting fibres are removed mechanically by sharp blades

from the surface of the fabric to a certain extent and that helps in reducing pilling.

Surface carbonizing: In this technique, the protruding fibres are burnt or dissolved with suitable

chemicals – the nature and the amount of chemicals used depends on the constituents of the

blended fabrics. The fabric is thus not only free from pilling but also gives surface feel.

Problems with oligomer in dyeing polyester yarns and fabrics.

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.

Problems caused by oligomer deposits

1. Spinning characteristics impaired

2. Reduced liquor flow through package of yarn because spindle perforations become blocked,

and deposits on pump cause improper pump pressure.

3. Presence can cause nucleation and growth of dye crystals or agglomeration of dye particles

and hence dye spots, unlevelness, and poor fastness.

4. Deposits on machine guides at winding or twisting cause high tensions and increased friction

on the yarn, leading to poor package build and end breaks.

5. White powdery deposits cause dulling of the yarn/fabric especially in dark shades, black, navy

etc.

6. Variation in rate of temperature rise due to deposits on heat exchanger

7. More frequent cleaning of dyeing and winding machines needed, hence increased down- time

and lower efficiency.

In some markets we have recently seen evidence of rather higher concentrations of oligomer,

particularly in yarn processing where the deposition of crystalline oligomers as a white powder on the

fibre surface and on the mechanism of winding machinery causes

problems.

Oligomers

Cyclic trimers migrate from PET fibre during dyeing and steam setting and, to a lesser extent, during

dry heat setting. The amount of oligomer migrating to the fibre surface increases with increase in

temperature, and with prolonged dyeing time, therefore the liberation of oligomers during dyeing can

be minimised by lowering the dyeing temperature from 130° to 120° C and by using the shortest

possible dyeing time.

1. Preparation.

Often polyester yarn and fabric may be dyed with no preparation at all. However, when problems with

oligomer deposits are being experienced we have found that a scouring treatment before dyeing can

remove some oligomers from the outset.

Customers routinely preparing woven polyester fabric on an open width washing range,mainly to

remove size, have noted also a marked reduction in oligomers present after scouring.

2. Dyeing.

Discharging the dyebath at high temperature, if this is possible, can also reduce oligomer

deposition.

A combination of non-ionic and anionic dispersing agents which helps to remove more

oligomers during the reduction clear process.

Application of an oligomer-binding agent to polyester yarn in the last rinse on the dyeing

machine can reduce the build-up of white powder deposits on the winding machine mechanism

with polyester containing high concentrations of oligomer