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| Cleaning & Hygiene-Bleaching |
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In domestic laundry, industrial laundry and dishwashing processes a bleach is normally added to aid the removal of 'bleachable' stains, such as those associated with polyphenolic molecules derived from tea, coffee, red wine, fruit juices etc. This bleaching step involves the chemical destruction of the chromophore in the stain, and also helps to remove the stain molecule from the surface by increasing the solubility of the oxidised stain molecule. |
Unlike traditional bleaches which can cause damage to both dyes and fibres, and which need to be added seperately due to poor compatibility with other formulations ingredients, the use of persalt based bleach systems enable a wide range of complete formulations to be produced. The use of persalts in formulated detergent powders, in dishwash powders and tablets, and in bleach additive products present the formulator with a number of options for incorporation of an effective bleach system for washing under all conditions.
Bleaching of oxidisable stains by persalt products is enhanced by increasing temperature, the concentration of hydrogen peroxide, the length of time taken for the wash and the pH. Persalts dissolve in water to provide an alkaline solution of hydrogen peroxide, with a natural pH of 10 - 10.5, maximising the level of the perhydroxyl anion, the active species available for bleaching, and are ideal for providing a bleaching effect on a wide range of bleachable stains.
The bleach performance can be enhanced at low temperatures by the inclusion of peroxygen bleach activators into formulations. The most widely used is the activator Tetra Acetyl Ethylene Diamine (TAED), which reacts with the hydrogen peroxide present in solution to produce peracetic acid and the peracetate anion in situ.
The use of persalt products with TAED gives a rapid generation of peracetic acid over a wide temperature range, which improves the bleaching of stains at cold to medium wash temperatures (30 - 500C). A sufficient molar ratio of Persalt : TAED is required for efficient generation of peracetic acid, and to maintain bleach performance for both medium and high temperature washing.
In addition to enhancing the stain removal the presence of peracetic acid provides an enhanced biocidal activity which can reduce the level of bacteria remaining on clothes and surfaces.
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