Bleach activator

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Bleach activator is a compound that allows washing temperatures lower than necessary to achieve full activity of bleach in washing liquids. The bleaching agent, usually peroxide, is usually active only from 60 Ã, Â ° C. With a bleach activator, this activity can be achieved at lower temperatures. Bleach activators react with hydrogen peroxide in an aqueous solution to form peroxy acid, they are a component of most laundry detergents. Peroxy acid is bleach which is more active than hydrogen peroxide at lower temperature (& lt; 60 Â ° C) but too unstable to be stored in its active form and hence it must be generated in situ.

The most commonly used whitening bleaches are tetraacetylethylenediamine (TAED) and sodium nonanoyloxybenzenesulfonate (NOBS). NOBS is the main activator used in the US and Japan, TAED is the main driver used in Europe.

Video Bleach activator

Structure and Properties

The bleach activator usually consists of two parts: the acid peroxy precursor and the leaving group; and modified by altering these sections. The acid peroxy precursor affects the bleaching properties of peroxy acid: determining activity, selectivity, hydrophobic/hydrophilic balance and oxidation potential. The leaving group affected the solubility, the rate of refluxysis and the stability of the activator storage.

Maps Bleach activator

Activation Mechanism

Bleaching activation is also known as perhidrolisis. Labor is an inorganic salt used as a carrier of hydrogen peroxide (for example including sodium percarbonate and sodium perborate). Birth and bleach activators are included together in a powder washer detergent containing bleach. In the washing, the two compounds dissolve in water. When dissolved in water, labor releases hydrogen peroxide ( for example from sodium percarbonate):

2Na ₂ CO ₃ ? 3H ₂ O ₂ -> 2Na ₂ CO ₃ 3H ₂ O ₂

In a basic detergent solution, hydrogen peroxide loses the proton and is converted into anhydroxyl anion:

H ₂ O ₂ ? H HO ₂ ^-

Anion perhidroxyl then invades the activator, forming a peroxic acid: RC (O) X -> X ^- RC (O) O ₂ sub> H

The overall reaction of TAED ( 1 ) with 2 equivalents of hydrogen peroxide produces diacetylethylenediamine ( 2 ) and 2 equivalents of peracetic acid ( 3 ):

Only an perhidroksil anion, and not a hydrogen peroxide molecule, reacts with a bleach activator. In aqueous solutions, hydroxide ions also exist, but because of the larger nucleophilicity of the perhidroksyl anion, it reacts in a special way. Once formed, peroxy acid may act as bleach.

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Economy

The consumption of bleach activators in 2002 was about 105,000 tons. However, consumption is stagnant or decreases due to cost pressures on detergents and advances in liquid detergent formulations (which do not contain bleach and bleach). The relatively high cost of conventional bleaching systems limits its spread in emerging markets, where cold water is used for washing and shooting by widespread sunlight or the use of sodium hypochlorite (as in the US) solution.

There is still considerable potential in Europe for more active bleach activators due to the potential energy savings that can be achieved by washing at lower temperatures, but their higher activity should not be accompanied by greater damage to textile dyes and fibers. In addition to bleaching stains in laundry, the disinfectant and deodorizing effects of bleach/activator combinations also play an important role. Therefore, they are also used in dishwashing detergents and artificial tooth cleansers.

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Example

The typical bleach activator is essentially a compound of N - and O -acils that form peroxyacids at perhidrolisis (meaning hydrolysis by hydrogen peroxide from bleach, persal). For example, TAED produces in peroxyacetic peroxide acids bleach-whitening fluid or from peroxidodanoic acid DOBA. In all cases, the activator chemically reacts according to the level of contamination in the laundry and is thus "consumed".

The literature describes various compounds of active acyl, such as tetraacetyl glycoluryl and other alkylated saturated heterocyclic heterocyclic, such as hydantoin, hydrotriazine, dicetopiperazine, etc., as well as acylated and lactam acylated.. The disadvantage of these compounds as compared to TAED standard compounds is their poorer ecological and economic performance.

In addition to NOBS acylated phenol derivatives, LOBS and DOBA (negatively charged in aqueous media), furthermore the bleach-active acyl O-acyl is described, for example tetraacetylxylose or pentaacetylcoseose. DOBA, commonly used in Japan, is characterized by good biodegradability and a greater effect on a number of microorganisms than TAED. Both work together synergistically. Furthermore, nitriles, such as cyanopyridine and cyanamides, cyanomorpholine and certain cyanomethyl trialkyl/arylammonium salts known as bleach activators (the latter, called nitrile quats, present in dilute solutions as cations).

${\ displaystyle \ left [{\ ce {R ^ {2} - {\ overset {\ displaystyle R ^ {1} \ atop |} {\ underset {| \ atop \ displaystyle R ^ {3}} {N}}} - CH2-CN}} \ right] {\ ce {X -}}}$

Nitrile quat is active in bleaching even at temperatures of about 20 ° C and acts through intermediate intermediate peroxoimino acids of peroxo compounds. It decomposes into an appropriate quaternary amide, which reacts with the aid of hydrogen peroxide to an appropriate and readily decomposed betaine. The disadvantage of nitrile quats is the poor biodegradability of the original substance and the often-spoken hygroscopicity, which, however, can be reduced by appropriate counterions.

Other new bleaching systems have been developed, especially for washing at lower temperatures and room temperature and for use in liquid detergent formulations:

• New and more active peroxyacids, such as phthalimidoperoxyhexanoic acid (PAP)

• Peracid reinforcement that forms a highly reactive switch with peracid (such as cyclic sulphucine as a reactive oxal precursor) or sugar-based ketone which forms a bleach activated dioxy with hydrogen peroxide
• The bleach catalyst, which forms as stable transition metal complexes (from metals such as manganese, iron, cobalt, etc.) with bleaching-active oxygen species even at temperatures below 30 Ã, Â ° C. They exceed the activity of standard compounds TAED almost 100 times. Such a complex offers a very large economy (lower detergent volume, fewer packaging, lower transport costs) and environmental benefits (low washing temperature, low waste water pollution). Of particular interest is the second-generation bleaching catalyst, which has already formed a species of bleaching-active with atmospheric oxygen, that is, they can mimic the natural mono- or dioxygenase-active sites. However, in 1994, the launch of the first generation manganese complex ("Persil Power Flop") by Unilever in England failed with disaster. Consequently, consumer confidence in whitening catalysts has been severely shaken. The only use of a combination of bleaching catalyst/persalt to date (2017) is used in dishwashing detergents.

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References

Source of the article : Wikipedia