Yellow, Pink, Orange, Red....so on and so forth. The world is full of colours and when it comes to the textile industry, importance of colours increases manifold. In the world of textile and apparel, colours are one of the factors that attract customers. This makes textile dyeing more of an art than a process. The world of textile dyeing is not oblivion to the changes in technology, consequent to this several new methods of dyeing are being developed. The new kinds of fabrics, detergents, environmental concerns are some of the issues that are kept in mind to develop new dyes in order to replace the conventional and more harmful dyes.
Another important factor is the fact that almost all the products are subjected to seasonal demand and variation. Industrial textile dyes must rise up to meet all these new and specific technical requirements.
One of the additions to the textile dyeing is foam dyeing process. As the name suggests, in foam dyeing, the main dyeing element is foam. In foam dyeing, foam is obtained from an aqueous solution and then spread on a fabric. Foaming agent and a carrier for dye stuff are also used in the process. After the fabric is covered with foam, it is put through high temperature so that the dye bonds well.
An aqueous solution is any solution in which water is the solvent i.e. it has the maximum quantity of water. Foam is a dispersion of a gas in a liquid. Here the liquid is generally water and the gas is generally air but it may also be an inert gas.
This process has an added advantage over other processes, as it involves treating a fabric with foam at low wet pick-ups. Wet pick-ups mean the amount of finish liquor applied to a fabric. Basically there are two types of foam: dispersion foam and condensation foam. Dispersion is a heterogeneous system which is made up of dispersed phase and dispersion medium. In colloidal dispersion one substance is dispersed as very fine particles in another substance called dispersion medium. A condensation reaction involves the loss of a small molecule such as water or hydrogen chloride from the reactants to form a connecting bond.
There are also two types of foam processing. In conventional continuous wet processing, the fabric web is immersed in a bath containing a dilute dispersion of the chemicals or dyes. The saturated fabric is then passed through squeeze rolls to extract excess liquor and finally travels into an oven where the fabric is dried. When necessary, the dried fabric passes into a higher temperature zone where the finish' is cured or fixed.
In continuous foam processing, the chemicals or dyes are formulated with a foaming agent in a more concentrated dispersion. The formulation is mechanically foamed, increasing its volume five to twenty fold. The resultant foam is applied as a coating to the fabric, the coated fabric is passed through squeeze rolls which collapse the foam and distribute the chemicals uniformly through the fabric. The fabric then enters the drying oven as before but the water to be evaporated is only 15 to 35%.