Activated bleach systems

Pig. 7. Storage stabHity of proteases in European powder detergent with activated bleach system. ( ) Traditional protease (--) protein-engineered... 

The incorporation of an activated bleach system into an HDL is still one of the biggest challenges in formulation technology, as the three basic components of a bleach system (hydrogen peroxide, activator or catalyst, and alkalinity) will normally decompose as soon as they come into contact with each other. 

First, it provides sanitization. This is important if the wash is undertaken at temperatures for which thermal disinfection is not possible or with residence times for which it is incomplete. Other formulation actives can also contribute to the overall biocidal activity of the composition and potentiate the kill achieved by the activated bleach system. 

Certain activated peroxide systems are specifically designed for bleaching wool and these will be mentioned later. 

DTPA tends to be a weaker chelator than EDTA. However it is very stable and has been found to be especially useful in peroxide bleach systems. DTPA works in a pH range similar to that of EDTA for most ions, but tends to have a slightly higher active range in controlling ferrous ions250. 

Lara, P. V., and Park, E. Y. 2004. Potential application of waste activated bleaching earth on the production of fatty acid alkyl esters using Candida cylindracea lipase in organic solvent system. Enzyme and Microb. Technol., 34, 270-277. 

There are other ways to decrease the silver ion activity in the bleaching system to allow the oxidation of silver to proceed. The silver ions can be complexed. An expression relating silver complexation to potential can be written. If the silver forms a complex with n ligand molecules, it has form of Eq. (90) ... 

Whereas vacuum has a beneficial effect in the removal of oxygen its effect in removing water from the system is more open to question. Activated bleaching earths contain about 8-12% of free moisture which is driven off at 120-130 C under atmospheric pressure, and about 6-7% of structural water which is only removed at 450-650 °C. The oil after vacuum drying contains less than 0.1% moisture and therefore if 1% of earth is used for bleaching, the system... 

This chapter will cover low-temperature bleach activators, catalysts utilizing peroxide or atmospheric oxygen for the oxidation reaction, and oxygen transfer agents that act as performance boosters for common bleach systems. Optimum conditions of use to maximize performance and avoid negative secondary reactions are described. Special attention is given to the various finishing processes, application forms, and delivery concepts that enable sensitive bleach components to be incorporated in household products, improve stain removal performance, and deliver an attractive appearance for consumers. 

Although over the past 30 years a large number of quite different bleach systems have been described in the literature, and some have been extensively test-marketed, only a few products have gained commercial attention. With an estimated annual consumption of 75 kt, TAED is the most widely used bleach activator for laundry applications. In combination with perborate or percarbonate, it is the major component of nearly all European HDPDs. Within the past decade, new markets for TAED have opened up in Eastern Europe, North Africa, the Middle East, and parts of South America. 

WO 99/00481 (1999) A. Meyer et al., Procter Gamble Bleach activators, persalts Nonaqueous hquid detergent comprising organic acid to reduce solubihty of bleach system... 

Divalent and trivalent transition metal cations (Fe, Cu, Al, Zn, Ni, Cr, etc.) also have several harmful effects, such as flocculation or catalytic destabilization of the bleaching systems that furnish active oxygen, and must, therefore, be eliminated as well. To this end, organic sequestering agents that are more specific to the metallic cations to be removed are used. This subject is, however, on the fringes of the agreed definition of a builder. 

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