The use of hydrogen peroxide allows not only a high degree of brightness, but also preserves the mechanical properties of the fibers. Similar to pulp bleaching, this process takes place in an alkaline environment. The bleaching liquors have to be stabilized to prevent decomposition reactions due to the presence of trace metals such as copper, iron and manganese, which can often be found in fibers or in water.
Cotton is the main fiber bleached today. Practically all cotton produces nowadays is bleached. About 80-90% of all cotton fabrics are bleached with hydrogen peroxide. Typically, bleaching with 0.3-0.6wt% solutions of hydrogen peroxide at a pH of 10.5-11.5 is carried out for 1-3 hours at a temperature of 90-95°C. In the past, sodium hypochlorite was commonly used for cotton bleaching. Hypochlorite bleach was, however, abandoned because of high fiber damage and technical difficulties.
Color-safe laundry bleaches containing hydrogen peroxide have been accepted by consumers as alternatives to bleaches containing hypochlorite. One of its advantages over chlorine-based bleaches is that it does not affect modern dyes. Evonik’s hydrogen peroxide grades were proven to yield an excellent bleaching performance in hard surface cleaners, laundry prespot products, carpet cleaners and other color-safe bleaching products.
For textile and color safe bleaching Evonik recommends using HYPROX® hydrogen peroxide products. For specific requirements we can recommend further grades on request.
Industrial laundries process laundry from hotels, hospitals, medical care, restaurants and food processing in continuous washing machines. Those washing processes consist of a series of different compartments where the laundry is treated. The process comprises of pre-washing, washing, rinsing, post-treatment and dewatering.
For the chemothermal disinfection of laundry PERACLEAN® products are used in the washing step as a disinfectant and bleaching agent. The favourable ratio of peracetic acid to H2O2 has a positive effect on the stability of the peracetic acid in the washing liquor, and in some cases makes it possible to reduce the quantity of disinfectant added while retaining the same good bleaching effect.