Deutsche Gold- Und Silber-scheideanstalt Vormals Roessler

Degussa Aktiengesellschaft

Gerd Knippschild

Hans Klebe

Hubert Schuster

There is produced a stabile per salt which contains simultaneously sodium percarbonate and sodium perborate by introducing a solution supersaturated with both sodium percarbonate and sodium perborate to nuclei which consist of sodium percarbonate and/or sodium perborate.

Process for the production of a stable per salt

There are prepared sodium percarbonate particles comprising a sodium percarbonate nucleus encased in a layer of a mixture of dehydrated sodium perborate and sodium silicate prepared by spraying the sodium percarbonate with a supersaturated solution of sodium perborate and a sodium silicate solution and drying to at least partially remove the added water.

Process for the production of stabilized sodium percarbonate

Sodium percarbonate is stabilized with highly dispersed silica. The sodium percarbonate containing 1 to 10 weight % of water is mixed with the silica and subsequently dried. The highly dispersed silica has an average particle size of 2-100 microns, preferably 7-20 microns. The product is sodium percarbonate particles encased by a sodium silicate jacket.

Process for the stabilization of sodium percarbonate

There are prepared sodium percarbonate particles comprising a sodium percarbonate nucleus encased in a layer of dehydrated sodium perborate or a mixture of dehydrated sodium perborate and sodium silicate with or without additional water binding materials chemically inert to sodium percarbonate and dehydrated sodium perborate.

Sodium percarbonate particles (A)

There are prepared sodium percarbonate particles consisting essentially of a sodium percarbonate nucleus encased in a layer of sodium silicate and sodium percarbonate and/or sodium tripolyphosphate.

Sodium percarbonate particles (B)

A compact, abrasion resistant sodium percarbonate is produced by reacting sodium carbonate with hydrogen peroxide. There is employed a solution saturated in sodium percarbonate and also containing (1) sufficient sodium carbonate that there is present sodium carbonate decahydrate as a solid phase, (2) sodium chloride in an amount of 100 to 200 grams per liter, (3) an active oxygen stabilizer and (4) sodium hexametaphosphate in an amount of 0.1 to 1.9 grams per liter. There is added hydrogen peroxide in an amount about equivalent to the dissolved sodium carbonate which results in a supersaturated solution of sodium percarbonate. The supersaturation is broken down by precipitation of sodium percarbonate during the addition of the hydrogen peroxide and up to 60 minutes thereafter. The entire process is carried out at a substantially constant temperature within the range of 10.degree. to 20.degree. C. The precipitated sodium percarbonate is separated and dried and the mother liquor can be returned to the first step of the process.

Process for the production of compact, coarse sodium percarbonate

A compact, abrasion resistant sodium percarbonate is produced continuously by reacting sodium carbonate and hydrogen peroxide in the presence of sodium percarbonate inocculant seeds, sodium chloride, an active oxygen stabilizer and sodium hexametaphosphate at 10-20.degree. C, the process comprises feeding into the preliminary inocculant and aqueous hydrogen peroxide solution containing an active oxygen stabilizer and simultaneously either (1) a filtered solution saturated in sodium carbonate and containing 40-100 grams per liter of sodium percarbonate, 0.1-1.0 gram of sodium hexametaphosphate per liter, 100-200 grams of sodium chloride per liter and an active oxygen stabilizer or (2) a mother liquor containing 40-100 grams of sodium percarbonate per liter, 0.1-1.0 gram of sodium hexametaphosphate per liter, 100-200 grams of sodium chloride per liter and an active oxygen stabilizer, with the proviso that when the mother liquor is employed there is also fed into the preliminary inocculant such an amount of calcined soda that no sodium carbonate decahydrate forms as a solid phase in the preliminary inocculant, the amount of hydrogen peroxide employed being approximately equivalent to the amount of dissolved sodium carbonate for reaction, the temperature is maintained constant during the entire process of precipitating sodium percarbonate, the supersaturation initially formed upon addition of the hydrogen peroxide being reduced by the precipitation of the sodium percarbonate, the precipitated sodium per carbonate is separated and dried.

Continuous process for the production of a compact, coarse sodium

Abrasion resistant and coarser sodium perborate tetrahydrate is prepared by reacting an aqueous sodium metaborate solution with aqueous hydrogen peroxide while avoiding free active oxygen and free alkali in the reaction medium. A strongly supersaturated perborate tetrahydrate solution having 200 to 700 grams/liter of perborate tetrahydrate is introduced into a previously prepared suspension of mother liquor and innoculant crystals which contains 100 to 500 grams/liter of suspension of seed crystals at such a rate that not more than 30 grams of perborate tetrahydrate grow as crystals per minute per square meter apparent innoculant surface area at 20 to 40.degree. C. and a rate of crystallization growth of not more than 100% whereupon the temperature is reduced to 15.degree. C. within 15 to 30 minutes, in a given case in a subsequent step. In another aspect of the invention the perborate is added at a point not earlier than the crystallizer.

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Wehr, Germany

Gerd Knippschild