Peroxide-Solvent Assisted

In peroxide-solvent assisted scouring agent based process substantial weight loss, strength loss a lowering of wetting time occurs up to a concentration of 4% of scouring agent. Also a very small change in these parameters was observed at higher concentration levels. For a given temperature and scouring agent concentration a rapid increase in weight loss, a steep decrease tensile strength and wetting time are observed with respect to an increase in peroxide concentration upto2%.

Apparent linear relation exists between a) weight loss and tensile strength. B) Wetting time and weight and loss and c) strength and wetting time.

Whiteness index show a linear relationship with the concentration of hydrogen peroxide and other factors like scouring agent concentrations, time and temperature had a little effect. Under identical conditions, acrylic, sized fabrics showed superior results than scratch sized fabrics in terms of whiteness and wettability. The poor results in the case of starch sized samples can be attributed to higher add-on levels of size and incomplete removal of tallow from the fabric during desizing.

COMBINED DESIZING SCOURING-BLEACHING MERCERISATION PROCESS

Cotton fabrics after impregnation with a mixed solution containing sodium hydroxide hydrogen peroxide and trichloroethylene for 3 minute at different temperatures and fabrics are taken for curing at 120^oC, followed by neutralization and washing. In this case, the strength retention, whiteness index, dye ability are mainly controlled by concentration of sodium hydroxide, dipping time, temperature and curing duration. But no further literature is available in this regard.

COMBINED DESIZING SCOURING AND BLEACHING OF COTTON USING OZONE

In the present work, an attempt has been made to combine all the three grey preparatory processes, such as desizing, scouring and bleaching. Here, ozone is used to desize, dewax and decolour the grey cotton fabric. To improve the fabric properties two stage bleaching is suggested wherein the fabric is treated with ozone followed by hydrogen peroxide⁶.

APPARATUS

The equipment used for the bleaching with ozone has three components: the ozone generator, the applicator and the ozone destroyer. The ozone generator of 8g/h capacity was supplied by Ozone Tek Ltd, India. The input for the generator is oxygen from a pressurized cylinder. The generator supplies the required concentration of ozone-oxygen mixture to the applicator. The applicator is a glass cylindrical tube with a diffuser at the bottom.

PROCEDURE

Wet grey cotton fabrics having 24% moisture content (wet pickup) were placed in the application chamber and exposed to 100 g/m concentration of ozone oxygen gas mixture at pH 5 using acetic acid for a specified time (1-7 min) at room temperature (about 30 C) for the combined desizing, scouring and bleaching. The gas mixture flow was maintained at a constant rate of 0.5 liter/min for the all experiments.

Inference

The above study shows that grey preparation with ozone can be completed in one or two minute. This process has additional advantages such as savings in thermal energy, water and chemicals. The quality of the fabrics processed with ozone is comparable with that of the fabrics processed by conventional method of desizing scouring and hydrogen peroxide bleaching.

ENVIRONMENTALLY FRIENDLY PROCESSES

Alkaline scouring is a commercially well established and efficient process. The drawback of this process, however is the use of large amounts of caustic (up to 80 kg/ton fiber material) as well as large quantities of rinse water once the scouring process is completed while the rinse water could be reused, the scouring effluent with its high BOD, high COD, and alkalinity presents a major problem. Increasingly stringent effluent regulations have thus generated interest in procedures that are nontoxic and environmentally caring⁷.