IMPROVEING THE REPRODUCIBILITY IN DYEING

POINTS TO DISCUSS

• REPRODUCIBILITY • RIGHT FIRST TIME DYEING• BLIND DYEING CONCEPT• LAB TO LAB REPRODUCBILITY• LAB TO BULK REPRODUCBILITY• AND HOW IMORVE REPRODUCBILITY

Background

What is reproducibility?

To perform something in well manners and with accuracy again and again.

Reproducibility in dyeing??

The ability to produce the same shade with recipe ,at anytime, every time and all the times is termed as reproducibility.

IMPORTANCE OF REPRODUCIBILTY IN DYEING

• Approaching better and accurate results• Decreases the shade variation• Saves time and cost• Increases productivity• Achieve customer satisfaction

How Reproducibility Is Improved?

Right First Time Concept

and Blind dyeing Concept

Right First Time Dyeing

• RFT is the level of precision and accuracy of process.

• Means the work done at first instance must have desired results.

• No re-working or adjustments

Importance of RFT

RFT eliminates• Reprocessing • Striping• Re-dyeing• Re-shading

What reprocessing means here??

• More use of dyes and chemicals.• More use of water• Loss of time and possibly deadlines• Lesser production compared to production

capacity.• More energy consumption• More effluent discharge and pollution.

• Higher effluent treatment costs• Low competitiveness• Low image in the global market.

Blind Dyeing

• To achieve the RFT the most popular approach is “Blind Dyeing”.

Blind dyeing concept

It is the practice of carrying out an exhaust dyeing, removing the batch from the, and loading the next batch and only then examining the first batch for shade , levelness etc.

Principle of Blind Dyeing

• No-addition dyeing concept

• Control of factors affecting dyeing

Practices done to achieve Reproducibility

Process Cost Productivity Profit

Bind dyeing(RFT) 100 100 100

Small addition 110 80 48

Large addition 135 64 -45

Strip or redye 206 48 -375

The factors effecting the Dyeing Reproducibility

EFFECT OF SUBSTARTE

• Quality of fiber• Textile yarn• Woven fabrics• Quality of fabrics• Fabric preparation• Lot to lot variation

Effect of process conditions

• Temperature• pH• Pickup• Methods of conditioning• washing

Effect of machine & equipment

• Color measuring instruments• Color data processing• Basis of computer matching• Spectrophotometer

Effect of Dyestuff & Auxiliaries

• Dye recipe formulation• Dyestuff variables• Impact of Dyeing auxiliaries

Effect of Water & Steam

• Water impurities• Hardness in dye bath• Bicarbonate in dye bath

Three Key Areas

• A recipe should give the same shade every time it is repeated in the lab

• A recipe developed in the lab should give the same shade in the bulk dyeing as it gives in the lab dyeing.

• A recipe should give the same shade, all the time it is repeated in the bulk dyeing

FACTORS EFFECTING DYEING REPRODUCIBILITY

• Water supply• Type of substrate• Dye application method• Liquor ratio• pH of dye bath• Time/temperature profile• Method of accessing color• Weight basis for recipe calculation

TYPES REPRODUCIBILTY

• Lab-to-lab reproducibility• Lab-to-bulk reproducibility• Bulk-to-bulk reproducibility

Lab to lab reproducibility

• High quality lab recipe must be developed that can b reproduced in bulk and give subsequent bulk continuity.

Three problems raise their heads here:• Accuracy of lab dyeing• Compatible lab dyeing methods that can

reproduced in bulk• Choice of dyestuff

Aids to improve lab accuracy

• Use of automated machinery• Lab dyeing machines with sophisticated

controllers • Using multi-product injection (MPI) facilities• Formulation and standards must be held in

shade library.• Color matching instruments must used.

Lab Responsibility

The following task must be taken care by the textile laboratory.

• Receiving inspection of textile goods and dyes.• Control of water quality.• Lying down of quantity criteria.• Development of appropriate test methods.• Selection of reasonable dyeing and finishing

methods

Lab Responsibility

• Making of formulation for new articles and shades.

• Production control.• Correction of off-shade dyeing• Testing of color fastness and technologies

properties.• Determination of the cause of problems

Lab to Bulk Reproducibility

• When bulk results are correlated with that of lab results then lab to bulk reproducibility is achieved.

• Good Lab to lab reproducibility attributes to good lab to bulk reproducibility.

Factors concerned for Good Lab to Bulk Reproducibility

Dye Selection

Many factors are involved in dye selection. Dyes must be:• Compatible• Robust• Stable• Chromopheric content• Reactive content in case of reactive dyes

Dye Selection

• Moisture content• Absorption in solution• Particle size of dye• Meeting the specification

Substrate Control

• The various factors in substrate specification must be certified such as:

• Dyeability• Quality of fibre , yarn and fabric

Computer color matching

• This technology can be major aid in dye house both in cost and speeding up the production.

• For this database must be updated regularly.

Requirements for lab to bulk reproducibility

• A laboratory procedure that reproduce bulk results or can be correlated with them must be available.

• Process details must be standardized.• Accuracy of weighting and measuring must be

of higher order in both lab and bulk practice.

Practical Approaches to achieve lab to bulk reproducibility

• By optimizing lab conditions compatible with the bulk.

• By playing with recipe.

How to Optimize lab conditions?

• Following Lab conditions can be considered for reactive dyeing:

• Pad pressure• Padder speed• Drying temperature• Drying time• Steaming temperature• Steam time

Summary

• Lab procedure must be reproduced or correlated with bulk system.

• Dyeing process must be standardized.• Accuracy of weighting and measuring at lab and

bulk scale.• Dyestuff used should be compatible , robust

and stable when applied.• Data base loaded onto computer should be

updated.

• Lab dyeing equipments with sophisticated and multi product injection are availed.

• Standard operating procedure(SOP)• Proper control of machine parameters.