Compositions – Oxidative bleachant – oxidant containing – or generative – Composition containing a stabilizer or a product in the form...
Patent
1994-05-20
1996-04-09
Lovering, Richard D.
Compositions
Oxidative bleachant, oxidant containing, or generative
Composition containing a stabilizer or a product in the form...
252 99, 25217413, 252358, 42721336, 427220, 427240, 4234152, 42840224, C01B 1510, B01J 1304, B05D 700
Patent
active
055058752
DESCRIPTION:
BRIEF SUMMARY
The invention describes a new recommendation for optimizing the melt-coating of water-soluble capsule substances on finely divided sodium percarbonate to increase its storage stability under practical use conditions.
Sodium percarbonate, an addition compound in which 1.5 moles of H.sub.2 O.sub.2 is included in the crystal lattice for each mole of Na.sub.2 CO.sub.3, is an important candidate to replace sodium perborate tetrahydrate, which is currently in wide use as an oxidizing agent, such as a bleaching agent in washing and cleaning agents. The decisive weakness of sodium percarbonate it its instability in storage, as in moist atmosphere and/or in mixtures with active components such as commonly occur in washing and cleaning agents.
For a long time, and until very recently, attempts were made to counter this weakness by using various principles, particularly addition of stabilizing components to the percarbonate and/or encapsulation of the percarbonate particles with suitable protective substances. Although some partial successes have been achieved here, there has not yet been a proposal which deals, as an integral part, with the manifold problems and aspects that have to be considered in this respect. Without claiming completeness, problems here include: The causes of the undesired decomposition of sodium percarbonate in storage and in practical use are complex. Moisture, thermal effects, and interaction with other components of the mixture, even as solids, lead to degradation of the peroxide. Water is a decomposition product, and it in turn catalyzes further decomposition of the peroxide. Suggestions based on the state of the technology, for encapsulating the percarbonate crystals with a water-repelling or water-impermeable capsule material obviously do not adequately consider many potentially harmful factors. When the encapsulants are coated as aqueous preparations, catalytic amounts of water are included in the encapsulated particle, even if water is removed immediately by simultaneously drying the coated powder. Removal of those catalytic amounts of water in the drying process is impeded or prevented by the water-tight film of encapsulant which is produced. Thus the germ of an undesired decomposition process is built into every sodium percarbonate particle in an uncontrollable manner.
It is well known that attempts have been made to apply suitable encapsulating substances as melts and/or in solution in organic solvents. That only appears to diminish the set of problems discussed. For example, German Laid-Open Patent 22 03 885 recommends applying fatty acids, fatty acid glycerol esters, fatty acid alkalonamides and/or long-chain aliphatic alcohols to finely divided sodium percarbonate as water-insoluble encapsulants. For instance, hot molten coating material is sprayed over the particles which move in a fluidized bed heated above the melting point of the coating material. Then the fluidized bed of coated percarbonate is cooled by a cold gas. In another example embodiment, hot molten coating material is added to a hot layer of particles and shaken mechanically, as in a Lodige-Morton mixer, and then allowed to cool. Even if the solid encapsulating agent is used in conjunction with organic solvents, substantial thermal stress on the sodium percarbonate is unavoidable. For example, a non-aqueous solution of the coating material is sprayed over the particles moving in a fluidized bed, with hot air blown in continuously to evaporate the solvent. European Patent 030 759 shows comparable recommendations.
Sodium percarbonate is held in a fluidized layer with hot air (ca. 90.degree. to 100.degree. C.) and then coated with a melt of the coating material, and cooled. Coating materials used here include long-chain hydrocarbons, as well as fatty acids and fatty alcohols. Both this process and the teaching of the previously mentioned German Laid-Open Patent assume a selected type of process in which the thermal stress on the solid sodium percarbonate particles during the melt coating of the encapsulant involves ther
REFERENCES:
patent: 3161602 (1964-12-01), Herbig et al.
patent: 4090973 (1978-05-01), Maguire, Jr. et al.
patent: 4126717 (1978-11-01), Mazzola
patent: 4131562 (1978-12-01), Lutz et al.
patent: 4327151 (1982-04-01), Mazzola
patent: 4657784 (1987-04-01), Olson
patent: 4919841 (1990-04-01), Kamel et al.
patent: 5002695 (1991-03-01), Schulz et al.
Beaujean Hans-Josef
Bode Jens
Carduck Franz-Josef
Degussa - Aktiengesellschaft
Lovering Richard D.
LandOfFree
Storage-stable encapsulated sodium percarbonate and process for does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Storage-stable encapsulated sodium percarbonate and process for , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Storage-stable encapsulated sodium percarbonate and process for will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-136678