Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With oxygen or halogen containing chemical bleach or oxidant...
Patent
1995-10-02
1997-08-19
Albrecht, Dennis
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
With oxygen or halogen containing chemical bleach or oxidant...
25218626, 25218627, 423275, 423281, 4233282, 4234152, 510441, 510442, 427215, C11D 339, C11D 3395, C11D 1706
Patent
active
056588739
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
This invention relates to coated sodium percarbonate particles, of which the coating contains a peroxygen-containing boron compound which imparts high storage stability to the sodium percarbonate. The present invention also relates to a process for the production of the coated sodium percarbonate particles by application of one or more coating components, more particularly in the form of an aqueous solution containing them, to the sodium percarbonate to be coated and to detergent, cleaning and bleaching compositions containing coated sodium percarbonate particles according to the invention.
Sodium percarbonate (2 Na.sub.2 CO.sub.3 .multidot.3H.sub.2 O.sub.2) is used as an active oxygen component in detergents, bleaches and cleaning preparations. In view of the inadequate storage stability of sodium percarbonate in a humid environment and in the presence of various components of detergents and cleaning preparations, sodium percarbonate has to be stabilized against the loss of active oxygen (O.sub.a). A key principle for stabilization is to surround the sodium percarbonate particles with a coating of stabilizing components. Thus, it is known that sodium percarbonate can be coated with paraffin or polyethylene glycol. Unfortunately, adequate long-term stability is not achieved in this way, in addition to which solubility in water is undesirably reduced. Even the application of a coating of alkali metal silicate to the sodium percarbonate particles, as proposed in DE-OS 26 52 776, does not lead to adequate stabilization and, in addition, introduces an unwanted content of insoluble constituents. In the processes known from DE-OS 24 17 572 and DE-OS 26 22 610, sodium sulfate and sodium carbonate or sodium sulfate, sodium carbonate and sodium silicate are used as coating components. In these processes, a solution of the coating components is sprayed onto sodium percarbonate particles in a fluidized bed dryer. Adequate stabilization requires a large quantity of coating material which in turn leads to a correspondingly large reduction in the active oxygen content.
Although it is known from DE-PS 28 00 916 that a coating material containing at least one boron compound from the group consisting of metaboric acid, orthoboric acid and tetraboric acid can be used for stabilizing sodium percarbonate, the stabilizing effect obtained in this way is described as inadequate in DE-OS 33 21 082, as demonstrated in the Comparison Examples. Instead, sodium percarbonate with a shell containing sodium borate is described as advantageous. However, as the inventors of the present application discovered when copying the Examples of DE-OS 33 21 082, the borate and, optionally, other coating components--to achieve adequate stability--had to be present in the coating in such a quantity that the available active oxygen content of the sodium percarbonate thus stabilized was always below 14% by weight. A further development of stabilization using borates is described in EP-A 0 487 256, although the coating process disclosed therein involves at least two stages and is therefore technically complicated.
Finally, DE-AS 24 58 326 describes a process for stabilizing sodium percarbonate, the storage stability of the pure product being increased, even in admixture with cleaning preparations. In this process, the sodium percarbonate is coated with a hydrophobic liquid organic compound to which sodium perborate powder is added. The disadvantage of this process lies in the need to use a hydrophobic liquid organic compound which has to be diluted with a lower alcohol in the interests of better handling. In addition, the quantities in which the coating chemicals are used, namely 5 to 20% by weight of sodium perborate and 5 to 10% by weight of hydrophobic organic compound, based on sodium percarbonate, are very high.
Coated sodium percarbonate particles consisting of a sodium percarbonate core and a coating of sodium perborate with the general formula NaBO.sub.2 .multidot.H.sub.2 O.sub.2 .multidot.n H.sub.2 O, where n is <3, are known f
REFERENCES:
patent: 1978953 (1934-10-01), McKeown
patent: 3327684 (1967-06-01), Pistor
patent: 4156039 (1979-05-01), Klebe
Ullmann's Encyclopedia of Industrial Chemistry, Vol. A4 (1985), 5 Edition, pp. 363-280.
Bertsch-Frank Birgit
Bewersdorf Martin
Klasen Claas-Juergen
Lieser Thomas
Mueller Klaus
Albrecht Dennis
Degussa - Aktiengesellschaft
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