Solvay Interox Gmbh

Solvay (societe Anonyme)

Solvay Interox (societe Anonyme)

Solvay Interox Sa

Graham R Horne

Alun P James

Manfred Mathes

Richard Roesler

Romano Pardini

Soraya Parvaneh

Pier-Luigi Deli

Lido Signorini

Robert Owen

Stefano Bigini

Uwe Droste

William R Sanderson

John P Sankey

Nicholas A Troughton

Juan-Teva Carlier

Richard R&ouml;sler

Tom Candy

Daniel R Baker

A process for preparing coated particulate alkali metal percarbonate in which coating is carried out by mixing percarbonate with a solid particulate coating and agent and optionally with an aqueous liquid, so that the amount of water present during mixing does not exceed 12% of the total weight of the mixture. Coated alkali metal percarbonate obtainable by this process and its use as active bleach in detergent compositions is also disclosed.

Process for preparing coated alkali metal percarbonate, coated alkali metal percarbonate obtainable by this process, its use in detergent compositions, and detergent compositions containing it

Coated sodium percarbonate particles are provided which contain a sodium percarbonate core, and a coating layer substantially free from sulate, borate and magnesium compounds, having at least 30 and at most 75% w/w of an alkali metal carbonate and at least 25 and at most 70% w/w of an alkali metal silicate. The alkali metal carbonate and silicate being uniformly dispersed in the coating layer. Also provided is a process for the preparation of the coated sodium percarbonate particles and their use in detergent compositions.

Coated sodium percarbonate particles, process for their preparation, their use in detergent compositions and detergent compositions containing them

Sodium percarbonate is traditionally made in a crystallization process from aqueous hydrogen peroxide and sodium carbonate with recycle of mother liquor in the presence of a substantial concentration of a salting out agent, conventionally sodium chloride. The invention provides a process intended to be conducted without addition of chloride salting-out agent in which the dissolution step is controlled to restrict the sodium carbonate concentration to below 95%, preferably 60 to 90% of its saturated concentration at a temperature preferably controlled to at most 35C. and the mole ratio of hydrogen peroxide:sodium carbonate in the reaction vessel is controlled to between 0.7 to 1.2:1, and preferably about 1:1. In some embodiments at least a fraction of the mother liquor introduced into the dissolution tank is obtained by extraction from the reaction vessel and in other embodiments a fraction of the sodium percarbonate is introduced in solution in the mother liquor and a fraction is introduced in particulate form directly into the reaction vessel. Large particle sodium percarbonate is provided which has a 7 day aged heat emission at 40C. of not more than 3 &mgr;W/g measured in a microcalorimeter over 16 hours that is lower than the heat emission from conventionally produced sodium percarbonate employing a chloride salting-out agent.

Sodium percarbonate and process for producing sodium percarbonate

A process for stabilising particulate alkali metal percarbonate involves coating it with an aqueous solution, preferably concentrated, of a non-reducing oligomeric saccharide, preferably sucrose and especially together with an inorganic salt co-coating agent. The preferred co-coating agents are alkali metal silicate, sulphate, carbonate and carbonate chloride. Coated percarbonate is provided having an excellent combination of solubility, and stability, even with low amounts of coating agent.

Process for stabilizing particulate alkali metal percarbonate

Sodium percarbonate exhibits a tendency to decompose in built compositions and particularly detergent compositions built with zeolites. The tendency can be ameliorated by selecting sodium percarbonate which intrinsically has a mean particle size of from 500 to 1000 microns and not more than 20% by weight of below 350 microns and has a moisture pick-up when measured in a test at 80% relative humidity and 32&deg; C. after 24 hours of not greater than 30 g/1000 g sample. A suitable sodium percarbonate can be made most conveniently by crystallisation from a bulk saturated solution of sodium percarbonate in a crystalliser/classifier that does not employ a conventional chloride salting-out agent.

Compositions containing sodium percarbonate

Sodium percarbonate is traditionally made in a crystallization process from aqueous hydrogen peroxide and sodium carbonate with recycle of mother liquor in the presence of a substantial concentration of a salting-out agent, conventionally sodium chloride. The invention provides a process intended to be conducted without addition of chloride salting-out agent in which the dissolution step (,) is controlled to restrict the sodium carbonate concentration to below 95%; preferably 60 to 90% of its saturated concentration at a temperature preferably controlled to at most 35&deg; C. and the mole ratio of hydrogen peroxide: sodium carbonate in the reaction vessel is controlled to between 0.7 to 1.2:1, and preferably about 1:1. In some embodiments at least a fraction of the mother liquor introduced into the dissolution tank (,) is obtained by extraction from the reaction vessel (,) and in other embodiments a fraction of the sodium percarbonate (,) is introduced in solution in the mother liquor (,) and a fraction is introduced in particulate form (,) directly into the reaction vessel (,). Large particle sodium percarbonate is provided which has a 7 day aged heat emission at 40&deg; C. of not more than 3 &mgr;W/g measured in a microcalorimeter over 16 hours that is lower than the heat emission from conventionally produced sodium percarbonate employing a chloride salting-out agent.

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Warrington, United Kingdom

Graham R Horne