Bleach activator

Bleach activators, also known as bleach activators , allow a lower washing temperature than would otherwise be necessary to achieve the full activity of bleaches in the wash liquor. Bleaching agents, usually peroxides , are often only sufficiently active from a temperature of 60 ° C. With bleach activators, the effect can already occur at 40 ° C.

Mode of action

Bleach activators are solids and react very quickly with liquid bleaching agents ( hydrogen peroxide or peroxycarboxylic acids ), which consist of solid peroxides such as. B. percarbonates , arise in the aqueous phase. Therefore, as granules, bleach activators are used practically only in solid detergent preparations in which storage stability is ensured by the spatial separation of the solid components. Anhydrous preparations or the stabilization of an anionic activator with cationic surfactants and incorporation into non-ionic micelles could not gain commercial acceptance.

An important activator is tetraacetylethylenediamine ( TAED ). TAED enters into a chemical reaction, e.g. B. with the bleach sodium perborate . The bleaching agent peroxyacetic acid (= peracetic acid) is formed. Peracetic acid is itself a bleaching agent, but because of its too low storage stability z. B. is not added directly in heavy duty detergents .

TAED works better against hydrophilic stains (tea, coffee, red wine) and is mainly used in Europe at washing temperatures between 40 and 60 ° C, while in the USA, nonanoyloxybenzenesulfonate ( NOBS ) is being used at washing temperatures between 20 and 40 ° C Has. In Japan, where washing is done with cold tap water even in winter, the NOBS-analogue LOBS (dodecanoyloxybenzene sulfonate ) and the carboxylic acid homologue DOBA (decanoyloxybenzoic acid) are used.

The peracids peroxynonanoic acid or peroxy (do) decanoic acid (produced from long-chain carboxylic acid esters with hydrogen peroxide) have a higher affinity for hydrophobic stains (ketchup, curry, soy sauce), which is another reason for their greater use in the USA and Japan.

Economical meaning

The consumption of bleach activators in 2002 was approximately 105,000 tons. However, consumption is stagnating or declining due to the cost pressure in detergents and the penetration of liquid detergent preparations (which, however, contain no bleaches and bleach activators). The relatively high cost of conventional bleaching systems also makes it difficult to spread them in emerging countries, where washing is done with cold water and photobleaching from sunlight or - as in the USA - the use of sodium hypochlorite solution is widespread.

Because of the considerable energy savings when washing at lower temperatures (under the buzzword: "boiling laundry at room temperature") there is still considerable potential in Europe for more active bleach activators, the higher activity of which, however, must not be accompanied by greater damage to textile dyes and fibers. In addition to bleaching stains in laundry, the disinfecting and deodorizing effects of bleach / activator combinations also play an important role - hence their use in dishwashing detergents and denture cleaners.

Examples

Typical bleach activators are substantially N - and O -Acylverbindungen that on perhydrolysis, d. H. the hydrolysis by hydrogen peroxide from the bleach (persalts) to form peroxy acids. The bleaching active peroxyacetic acid is created from TAED in the washing liquor, from DOBA peroxydodecanoic acid. In all cases, the activator is chemically converted in the amount corresponding to the degree of soiling of the laundry and thus “used up”.

A large number of active N-acyl compounds are described in the literature, such as. B. Tetraacetylglycoluril and other acylated saturated nitrogen-containing heterocycles such as hydantoins, hydrotriazines, diketopiperazines, etc., and acylated imides and lactams, which are uncharged in the aqueous medium. A disadvantage compared to the standard connection TAED is its usually poorer economic and ecological balance.

In addition to the (anionic) acylated phenol derivatives NOBS, LOBS and DOBA, which are negatively charged in an aqueous medium, further bleach-active O-acyl compounds are described, such as. B. Tetraacetylxylose or Pentaacetylglucose . The DOBA commonly used in Japan is characterized by good biodegradability and a stronger effect on a number of microorganisms compared to TAED. Both act synergistically.

Furthermore, nitriles, such as cyanopyridine and cyanamides, such as cyanomorpholine and, in particular, the cyanomethyl-trialkyl / arylammonium salts which are cationic in aqueous solution, the so-called nitrile quats , are known as bleach activators.

Nitrile quats are bleaching active even at temperatures around 20 ° C and act via peroxoimino acids formed as intermediates with peroxo compounds. These disintegrate into the corresponding quaternary amides, which in turn react with hydrogen peroxide to form the corresponding, readily biodegradable betaines. Disadvantages of nitrile quats are the poor biodegradability of the original substances and their often pronounced hygroscopicity, which, however, can be reduced by suitable counterions.

New classes of compounds have been developed as further bleaching systems, in particular for washing temperatures at room temperature and below and for use in liquid detergent preparations:

• New more active peroxy acids, such as. B. Phthalimidoperoxyhexanoic acid ( PAP )

• Peracid boosters that form highly reactive intermediates with peracids, such as B. cyclic sulfonimines as precursors of reactive oxaziridines or sugar-based ketones that form bleach-active dioxiranes with hydrogen peroxide

• Bleach catalysts which, as stable transition metal complexes of metals such as manganese, iron, cobalt, etc., form bleach-active oxygen species with persalts at temperatures below 30 ° C and their activity is almost 100 times higher than the TAED standard. Such complexes offer enormous economic (lower volume of detergent, less packaging, lower transport costs) and ecological (low washing temperature, low wastewater pollution) advantages. Of particular interest are second-generation bleach catalysts that already form bleach-active species with atmospheric oxygen. H. can biomimetically mimic the active centers of natural mono- or dioxygenases. Because of the disastrously failed market launch (“Persil Power flop”) of a first-generation manganese complex by Unilever in Great Britain, consumer confidence in bleach catalysts has been shaken for a long time. The only use of bleach catalyst / persalt combinations to date is in dishwashing detergents.

Individual evidence

1. ↑ ^{a b} Clariant Surfactant Division: The Clean and Clever Way of Bleaching, PERACTIVE® ( Memento from July 17, 2013 in the Internet Archive ) (PDF; 885 kB), August 1999.
2. ↑ M. Tsumadori, J. Oleo. Sci., 50 (5), 367-372 (2001) and M. Tsumadori: Recent trends of surfactants in the fabric & home care field , in CD Proceedings 6th World Surfactants Congress CESIO, Berlin, Germany, June 21-23, 2004 (paper # 196).
3. ↑ G. Reinhardt, To Bleach or Not to Bleach - New Oxygen-Based Bleach Technology , in 5th World Conference on Detergents: Reinventing the Industry: Opportunities and Challenges, edit.A. Cahn, AOCS Publishing, 2003, ISBN 978-1- 893997-40-0 .
4. ↑ M. Sajitz, J. Grohmann: Hygiene Effects of Bleach Systems in Laundry Detergents  ( page no longer available , search in web archives ) (PDF; 401 kB), SOFW Journal 10-2012.
5. ↑ G. Reinhardt et al., New reactive bleach activators - a tightrope walk between bleaching efficiency and dye / fiber damage , Tenside, Surf. Det., 34 (6), 404-409 (1997)
6. ↑ Patent EP0790244 : Ammonium nitriles and their use as bleach activators. Published on August 20, 1997 , applicant: Hoechst AG, inventor: M. Löffler. ‌
7. ^ Lars Cuypers, Martina Hirschen, Gerd Reinhardt: Bleaching Product Development in View of Ecological Aspects . In: Tenside Surfactants Detergents . tape 42 , no. 6 , December 2005, p. 342-346 , doi : 10.3139 / 113.100277 .
8. ↑ Patent EP0349940 : Phthalimidoperoxihexanoic acid , process for its production and its use. Published on May 13, 1998 , applicant: Clariant GmbH, inventor: Hanspeter Gethöffer, Gerd Reinhardt. ‌
9. ↑ Patent EP0923636 : Color-safe bleach boosters, compositions and laundry methods employing same. Published on January 20 , Applicant: The Procter & Gamble Co., Inventor: GS Miracle et al ..
10. ↑ Patent EP1209221 : Use of cyclic sugar ketones as a catalyst for peroxygen compounds. Published on May 29, 2002 , Applicant: Clariant GmbH, Inventor: G. Reinhardt, N. Reichardt. ‌
11. ↑ Patent EP1225215 : Use of transition metal complexes with oxime ligands as bleach catalysts. Published on July 24, 2002 , Applicant: Clariant GmbH, inventors G. Reinhardt et al ..
12. ↑ Patent US5244594 : Bleach activation multinuclear manganese-based coordination complexes. Published on September 14, 1993 , Applicant: Lever Brothers Co., Inventor: TLF Favre et al ..
13. ↑ M. Verrall, Unilever consigns manganese catalyst to the back-burner , Nature, 373, (1995), 181 and Chemistry in action !, 45, The soap wars: detergent giants fight dirty ( Memento of December 12, 2013 in the Internet Archive ), last revision on November 17, 1996.