Levelling agents

in every dye house ,levelness of the dyeing is a major criteria , since unlevelled    goods are usually not saleable ,causing loss to the manufacturer.

Leveling
Migration of applied dyes in a uniform manner throughout the dyed goods is called leveling and it may be a property of the dye or it may require some chemical assistance (of leveling agents which are dye bath additives
 to promote level dyeing)
Levelling agents are invariably surfactants ;they may be anionic ,cationic,non ionic or amphoteric in nature .some times combinations of these are also used ,There are two fundamental mechanisms that can contribute to a level dyeing:

1.Control of rate of exhaustion of the dye so that it is taken evenly and slowly.

2.Migration of the dye after initial uneven sorption on the fiber.

In complex formation the principle of leveling is usually the same ,irrespective of whether non ionic or ionic agents are used , although the mode of complexing is different.

The attractive forces between leveling agent and dye creates a counter balancing mechanism against dye fiber attractive forces,restraining the uptake of dye by the fiber.

As the temperature of the dyebath increases , the complex gradually breaks down ,progressively releasing dye for more gradual sorption by the fiber.

further reading :-Role of leveling agents in textile wet processing
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How to Test pH of Textile material

Testing of pH by water extraction method

Purpose of the test

The pH of the processed textiles must be neutral and within the prescribed limits for a particular end use. The textiles with higher pH value may exhibit yellowing tendencies ,create change of shade upon storage and during shipment, result into poor dye pick up , patchy dyeing and poor colorfastness. very high and very low pH results into degradation of textiles during storage and use , may result into poor softness and harsh feel. pH of apparel fabrics which are in direct contact with the skin or used for baby wear, must be controlled not to make the skin itchy. 

The pH control is very important for in process quality as well as quality of the finished material.

Test method

Boil 250 ml distilled water or deionized water for 10 minutes and put 10+/- 0.1 gm of test specimen in it boil for another 10 minutes. Allow it cool down to room temperature , remove the specimen and squeeze back the excess water in the beaker. 

Test the pH by using a calibrated pH meter within an accuracy of +/-0.1 on pH scale.

The pH of water extract must be tested after prior to dyeing if you are getting uneven dyeing and to be tested after completion of dyeing and soaping to avoid any problems in finishing such as softening and dye fixing etc.  

This information is generalized for day to day in house process control, for detailed information please follow AATCC 81-2006

and ISO-3071. 
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Sequestering Agents

Sequestering Agents

Sequestering agents combine with calcium and magnesium ions and other heavy metal ions in hard water. They form molecules in which the ions are held so securely (sequestered) that they can no longer react.
The sequestering agents prevent salts from recontaminating parts.
The sequestering agents may also tie up the active chemicals in a detergent that may decrease the cleaning efficiency and life of a wash bath.
Common sequestering agents include orthophosphate, orthosilicate, and phosphates.Sequestering agents are produced as powder or in liquid form.
Phosphates are a wastewater problem since they contribute to eutrophication, the enrichmentof water with nutrients that increase plant growth in water ways and sewer systems.
The first sequestering agent in textile processing was EDTA ,
now a days many other types of sequestering agents are widely used in textile processing. The three main stages in which sequestering agents are used are
1.Pretreatment
2.Bleaching
3.Dyeing
Selecting a sequestering agent -I
Selecting a sequestering agent-II
Comparative study of some Sequestering chemicals

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