Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With oxygen or halogen containing chemical bleach or oxidant...
Patent
1996-01-16
1998-08-11
Einsmann, Margaret
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
With oxygen or halogen containing chemical bleach or oxidant...
510302, 510315, 510442, 510444, 510318, 25218627, 25218632, 4234152, C11D 304, C11D 1706
Patent
active
057927383
DESCRIPTION:
BRIEF SUMMARY
This invention relates to granular laundry detergent compositions having a content of silicate-based builder and alkali metal percarbonate as an oxygen-releasing compound.
Detergent compositions containing alkali metal percarbonate are known in the art. Percarbonate is an attractive perhydrate bleaching agent for use in detergent compositions because it dissolves readily in water, is weight efficient and, after giving up its available oxygen, provides a useful source of carbonate ions for detergency purposes and does not provide undesirable by-products.
The inclusion of percarbonate salts in laundry detergent compositions has been restricted hitherto by their relative instability in storage. In particular, percarbonate salts decompose rapidly when stored in a moist and/or warm atmosphere.
It has been attempted to obtain acceptable storage characteristics by coating crystalline percarbonate. A variety of coating agents have been proposed including silicate and mixtures of inorganic sulphate and carbonate salts. An example of such a coating is disclosed in GB-A-1,466,799, which discloses percarbonate particles coated with a mixed salt comprising sodium carbonate and one or more other sodium salts. The storage stability was tested of these percarbonate particles in a detergent composition comprising phosphate builders.
Considerable interest exists in the development of more "environmentally friendly" detergent compositions and processes, for instance for washing laundry in the home. "Environmentally friendly" detergent compositions are often characterised in that they minimise the levels of components which may cause environmentally undesirable effects. Thus phosphate builders are considered undesirable.
Preferred builders are based on silicate, including aluminosilicate ion exchange materials known as zeolites, and contain no phosphate. However the storage stability of percarbonate is a greater problem in silicate-built (especially zeolite-built) detergent powders than in phosphate-built detergent powders, possibly due to the fact that such compositions tend to have a large mobile water content.
It has been attempted to solve this problem in EP-A-0451,893. This discloses zeolite-built detergent powders containing sodium percarbonate with a controlled particle size distribution; fine percarbonate particles are excluded and coarser particles having high mean particle diameter are used. Reactivity is inversely proportional to size and so the coarser particles are of lower reactivity than finer particles. Hence the percarbonate particles are more storage stable in the presence of moisture.
However coarser particles used have lower solubility and/or are slower to dissolve in wash liquor and hence give a lower performance than finer particles, which dissolve quickly but have a lower storage stability.
Solubility problems have been encountered with coatings for percarbonate particles other than coatings such as those described in GB 1,466,799. Coatings based on silicates and organic materials can render the coated particles insufficiently soluble. Silicates in particular leads to, further problems in hard water, where they can form salts of low solubility.
Thus the prior art presents a problem of obtaining detergent compositions containing silicate as builder and storage stable yet fast dissolving percarbonate.
According to the invention there is provided a granular, silicate-built, phosphate-free laundry detergent composition comprising alkali metal percarbonate in the form of particles of mean particle diameter below 450 .mu.m wherein no more than 20% of the particles have a diameter above 710 .mu.m, said particles having a coating comprising water soluble material selected from water soluble inorganic salts, which can adopt a higher hydrated state, water soluble salts of carboxylic acids and mixtures thereof.
The invention is based in part on the discovery that it is possible to produce a granular laundry detergent composition containing fine percarbonate particles having a coating of water soluble organic or in
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Baillely Gerard Marcel
Dovey Anthony
Sorrie Graham Alexander
York David William
Bolam Brian M.
Einsmann Margaret
Robinson Ian S.
The Procter & Gamble & Company
Zerby Kim William
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