Textile Auxiliary Chemicals

Surfactants and General Usage Areas

Textile auxiliary chemicals are substances such as wetting, defoaming, anti-breakage, which facilitate pre-treatment, dyeing, printing and finishing processes in textile finishing.

Surface Active Substances

Although some substances used in textile finishing do not have a direct effect on the finishing processes, they contribute positively to the efficiency of the process result. These substances are known as finishing aids or surfactants. Surfactants are substances that can dissolve or disperse in a liquid and lower the surface tension of the liquid in which they are dissolved or dispersed. If the water or aqueous solution used in aqueous textile processes contains surfactant, the surface tension of this water or aqueous solution decreases. Thus, it becomes easier to wet and process the textile material with this aqueous system.

A surfactant usually does not have the only action. In other words, they create effects such as cleaning, wetting, foaming, emulsifying and dispersing together. However, depending on the chemical structure of the surfactant, one of these properties is superior to the others. Based on their superior properties, that surfactant is named as wetting agent, washing agent (detergent), ion trap, defoamer, emulsifier, disperser, preservative. Surfactants are substances with very large hydrophobic groups (long hydrocarbon chains) with weak electrostatic strength and small hydrophilic groups with strong polar strength. It is possible to examine surfactants under four groups according to the chemical structure of the hydrophilic group.

1. Anionic surfactants:

In a surfactant, if the hydrophobic part is found in the (-) electrically charged group of the molecule, they are called anionic surfactant surfactant. Anionic surfactants have –COO-, -SO3-, -SO3- group attached to a hydrophobic end carbon (C) atom.

2. Cationic surfactants:

In a surfactant, if the hydrophobic part is found in the (+) electrically charged group of the molecule, they are called cation active substance. These are usually derivatives of ammonia.

3. Amphoteric surfactants:

If the hydrophobic part is present in both anion and cation, it is called amphoteric surfactant. Since they are dionic, they react cationic in acidic solutions and anionic in basic solutions.

4. Nonionic surfactants:

They are surfactants that do not dissociate into ions although they dissolve in water.

Surfactants used in textile finishing may belong to one of the above-mentioned classes. Their common feature is mostly surface tension reductions in liquid/liquid or liquid/solid interfaces. Whether a surfactant is anionic, cationic, or nonionic can be determined by chemical structure analysis.

Wetting Agents

Wetting agents are substances that reduce the surface tension between the fibrous material (substrate) and the bath by removing the air between the fibers. Wetting agents are auxiliary materials used at every stage of production. The speed of the process often depends on the wetting power of the wetting agent. This depends on the wettability and the ability of the textile to absorb water. Turkish red oil has been used as a wetting agent for years. These were called dyeing and pressing oils. Today, it is important not only that the fiber is wetted, but also that the wetting rate is compatible with the ever-increasing production rate. For this, the wetting agent should reduce the boundary surface tension between the bath and the fiber as soon as possible. There are many wetting agents used in textiles according to their chemical structures: anionic, cationic, nonionic, amphoteric. But the most important ones are anionic and nonionic types.

Washing Agent

With the washing auxiliary raw materials, ready-made washing, cleaning, rinsing aids for household and industry are obtained. The fact that soap is not resistant to hard water and acidic environments and that it gives alkaline reactions with hydrolytic separation has led to the development of washing agents. Washing agents are generally anionic and nonionic surfactants. Cationic and amphoteric surfactants are not used in washing processes because they have high affinity. The washing process is done to remove the dirt on the fabric and the chemicals left on it as a result of the finishing processes. It helps to remove unfixed dyestuff and other impurities from the fabric by washing, especially at the end of dyeing, in order to obtain true fastness and tone.

Sequestering Agents

They are substances that remove water hardness. It prevents the calcium and magnesium ions in the water from damaging the fiber and deteriorating the stability of the bath by forming a complex. Calcium and magnesium ions in hard water form water-insoluble complexes. This situation especially reduces the effectiveness of anionic surfactants, and the precipitation of water-insoluble complex compounds on the textile product causes problems in the subsequent coloring processes. In addition, even a very small amount of some heavy metals causes problems during the process. Iron stains formed during bleaching processes are the most important problem. As it is known, heavy metal ions accelerate the breakdown of hydrogen peroxide. Hydrogen peroxide, which is broken down by the effect of these metal ions, causes staining and damage on the fiber. In coloring processes, metal ions and dyestuff molecules may react and cause precipitation, discoloration, uneven dyeing and decrease in fastness properties. Metal ions are usually found in operating waters. Apart from that, some metal ions may dissolve from the machine surface. Such metals may be present on the textile material or some dyestuffs and chemicals used may contain the same metal ions. For this reason, it is not possible to prevent these problems by using only suitable operating water. In fact, sometimes over-treatment of water can result in the formation of substances that were not originally present in the water. In order to prevent all these problems, some chemicals that only react with metal ions are used without disturbing the actual process and process reaction. Such substances are known as ion scavengers.

Emulsifiers

Emulsions are systems formed by the homogeneous mixing of two immiscible liquids. Auxiliary substances used to form emulsions are called emulsifiers. In other words, they are substances that allow two immiscible liquids to form an emulsion homogeneously without phase separation. Emulsifiers are used in various processes in textiles. They are used as degreaser and washing agent. It is used as a cleaning agent especially in boiling process. It is used to dissolve dyestuffs. It is used in the preparation of emulsion pastes in the printing process. It is used to transfer the finishing materials to the textile product in water and oil repellent finishing. It ensures that the finishing material, which gives softness, is transferred to the product economically by the extrusion method.

Dispersing Agents

They are auxiliary substances that allow water-insoluble solids to disperse homogeneously in water. These substances are especially important for the homogeneous dispersion of water-insoluble disperse dyestuffs in the liquor. Dispergator types; Dispergators are examined in three groups: Anionic type water-soluble dispersers (polyelectrolytes), Anionic and nonionic type surfactants, Polymers. These compounds easily disperse the dyestuff in water. Thus, the dyestuff remains stable throughout the applied process.