Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With oxygen or halogen containing chemical bleach or oxidant...
Patent
1997-03-18
1999-07-27
Einsmann, Margaret
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
With oxygen or halogen containing chemical bleach or oxidant...
510375, 8111, 25218629, 25218632, 25218643, D06L 302, C01B 1510, C11D 339, C11D 318
Patent
active
059290153
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to particles having a core of a peroxy compound and a coating comprising a silicate, a water soluble magnesium salt, and an aliphatic organic compound as a chelating agent. 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 (tetraacetylglucoluril) or PAG (penta acetyl glucose).
In order to make environmental friendly detergents, it is desirable to use alkali metal carbonate peroxy hydrate, commonly 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 sulfates, carbonates, borates, silicates or organic substances. Such stabilizing methods are described in the patent literature, for example in GB 1446799, GB 1538893, GB 1575792, EP 459625, U.S. Pat. No. 3,975,280 and EP 573731.
U.S. Pat. No. 4,075,116 describes preparation of percarbonate from sodium carbonate, hydrogen peroxide and different additives.
CH patent 659082 describes mixing bleaching agents with water soluble acids.
The 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 silicate and a water soluble magnesium salt. The core and/or the coating contains an aliphatic organic compound or a salt thereof as a chelating agent.
It has been found that the combination of silicate and a magnesium compound enables formation of magnesium silicate which is a very powerful stabilizer for peroxy compounds. Since magnesium silicate is not readily soluble in water, it has until now been difficult to apply it as a coating on particles of peroxy compounds. The presence of a chelating agent improves the stability of the peroxy compound significantly. The highest stability is achieved if both the core and the coating contains a chelating agent. However, the stability is very good even if the chelating agent is present in the coating only or in the core only.
The stability of the peroxy compound is further improved if the coating also contains at least one alkali metal salt of carbonate, bicarbonate or sulfate, alone or in mixtures. The alkali metal may for example include sodium, potassium or lithium, or mixtures thereof. Sodium is particularly preferred. The amount of said alkali metal salt is preferably from 0 to about 20% by weight, most preferably from 0 to about 10% by weight.
The different components of the coating can be in the same or in separate layers applied in one or several steps. Preferably, a first layer, counted from the core, contains the silicate and optionally one or more alkali metal salts of carbonate, bicarbonate or sulfate, while a second layer contains the magnesium salt and optionally one or more alkali meta
REFERENCES:
patent: 3975280 (1976-08-01), Hachmann et al.
patent: 4075116 (1978-02-01), Mesaros
patent: 4231890 (1980-11-01), Yagi et al.
patent: 5340496 (1994-08-01), Sato et al.
Jigstam Monica
Lagnemo Hans
Einsmann Margaret
Eka Chemicals AB
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