Bleaching agent

Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With oxygen or halogen containing chemical bleach or oxidant...

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Details

8111, 25218627, 25218643, 25218625, C11D 339, C01B 1510

Patent

active

058469222

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to particles having a core of a peroxy compound with capability of releasing hydrogen peroxide or peroxy acids in aqueous solutions and a coating comprising a chelating agent selected from salts of hydroxy carboxylic acids. The invention also relates to preparation and use of the particles. Further, the invention relates to a composition containing such coated particles.
Powder detergent compositions often contain peroxy compounds as bleaching agents which release hydrogen peroxide or peroxy acids in aqueous solutions. However, many peroxy compounds are not storage stable. Their decomposition is supposed to be catalysed by metal cations moving comparatively freely through the water normally being present in detergents, but is also facilitated by the alkaline pH (normally from about 8 to about 12) and by other components commonly present in detergents, for example zeolites or bleaching activators such as TAED (tetraacetylethylene diamine), TAGU (tetraacetyl-glucoluril) or PAG (penta acetyl glucose).
In order to make environmental friendly detergents, it is desirable to use alkali metal carbonate peroxy hydrate, known as percarbonate, as a bleaching agent. However, the activity of percarbonate in a detergent decreases rapidly through decomposition if the detergent is stored at normal room temperature and humidity.
Many attempts to stabilize percarbonate have been done, for example by mixing or coating with stabilizing substances such as borates, silicates or organic substances. Such stabilizing methods are described in the patent literature, for example in GB 1575792, EP 459625, U.S. Pat. No. 3,975,280 and EP 573731.
It has also been disclosed to combine percarbonate with chelating agents such as alkali metal citrate (see EP 546815) or phosphonic acids (see WO 91/15423).
CH 659082 describes a detergent additive comprising a mixture of a peroxide, an inorganic carbonate and an acid or its salt. The additives facilitate the dissolution of the bleaching agent.
U.S. Pat. No. 4,075,116 discloses a method of preparing sodium percarbonate from sodium carbonate and hydrogen peroxide, which method includes adding a compound selected from sodium sulfate, potassium sulfate, sodium pyrophosphate, potassium pyrophosphate, sodium metasilicate, sodium disilicate, sodium citrate, sodium glucoheptonate, sodium perborate, anhydrous sodium carbonate, potassium carbonate and mixed sodium and potassium carbonate. However, the patent is not addressed towards stabilization of previously prepared sodium percarbonate or to the inhibition of the other constituents of detergent mixtures containing percarbonate.
The main object of the present invention is to provide particles comprising a peroxy compound, particularly alkali metal percarbonate, with improved storage stability, particularly in detergent compositions. It is another object of the invention to provide particles comprising a peroxy compound only containing environmental friendly constituents.
Through the present invention, these objects have been fulfilled by providing particles having a core of a peroxy compound with capability of releasing hydrogen peroxide or peroxy acids in aqueous solutions, particularly in alkaline solutions. The particles have a coating containing a chelating agent selected from alkali metal salts or alkaline earth metal salts of a hydroxy carboxylic acid satisfying the formula:
It has surprisingly been found that hydroxy carboxylic acids according to the above formula gives superior storage stability compared to conventional chelating agents such as phosphonic acids, citrate or EDTA (ethylene diamine tetra acetic acid), at the same time as they are easily biodegradable and therefore environmental friendly. It is preferred that chelating agents not being so easily degradable, such as phosphonic acids, phosphonates and EDTA, are not included in the particles. Further, is has been found that the chelating agent is much more effective when it is applied as a coating then if it is mixed in the core. However, the most effecti

REFERENCES:
patent: 3975280 (1976-08-01), Hachmann et al.
patent: 3977988 (1976-08-01), Tokiwa et al.
patent: 4075116 (1978-02-01), Mesaros
patent: 4117087 (1978-09-01), Dillenburg et al.
patent: 5264143 (1993-11-01), Boutique
patent: 5340496 (1994-08-01), Sato et al.
RoMPPS Chemie-Lexikon, Upplaga 8, Band 2, 1981, p. 1503, "Gluconsaure".
Kirk-Othmer Encyclopedia of Chemical Technology, Third Edition, vol. 5, p. 344.

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