Compositions – Oxidative bleachant – oxidant containing – or generative – Composition containing a stabilizer or a product in the form...
Patent
1995-04-27
1998-02-24
Anthony, Joseph D.
Compositions
Oxidative bleachant, oxidant containing, or generative
Composition containing a stabilizer or a product in the form...
25218643, 4234152, 510309, C01B 15043
Patent
active
057208964
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/US93/04689 filed May 18, 1993.
TECHNICAL FIELD
The present invention relates to dry bleaching compositions for laundry. Dry laundry bleaching compositions are described which comprise percarbonate as the bleaching species, said compositions being stable upon manufacture and storage.
BACKGROUND OF THE INVENTION
The inorganic perhydrate bleach most widely used in the context of laundry bleaching is sodium perborate in the form of either the monohydrate or tetrahydrate. However, concerns about the impact of boron salts on the environment have led to an increasing interest in other perhydrate salts, of which sodium percarbonate is the most readily available.
Detergent compositions containing sodium percarbonate are known in the art. Percarbonate salts, particularly sodium percarbonate, are attractive perhydrates for use in detergent compositions because they dissolve readily in water, are weight efficient and, after giving up their available oxygen, provide a useful source of carbonate ions for detergency purposes.
However, the inclusion of percarbonate salts in detergent compositions has been restricted hitherto by the relative instability of the bleach both as is and in use. Sodium percarbonate loses its available oxygen at a significant rate in the presence of ions of heavy metals such as iron, copper and manganese and also in the presence of moisture, these effects being accelerated at temperatures in excess of about 30.degree. C.
Moisture and heavy metal ions are unavoidable components of conventional granular laundry treatment compositions. Also percarbonate decomposition due to moisture becomes more of an issue during storage as laundry treatment products are often stored in humid environments where the product picks up moisture. This has resulted in marginally acceptable percarbonate bleach stability under Northern European summer conditions, where the average maximum temperature over the hottest months is from 21.degree. C. to 25.degree. C., and unacceptable stability under temperatures higher than this. Such conditions are found in the Middle East and Southern Asia and also in Southern Europe where average maximum temperatures are in the 27.degree. C. to 33.degree. C. range for the hottest summer month.
Such temperature accelerated percarbonate decomposition also occurs during the manufacture of the finished product. Indeed, as individual ingredients are mixed together the temperature of the mixture increases, accelerating the decomposition of the percarbonate. Furthermore, the temperature increase is greater if the mixing occurs under adiabatic or semi-adiabatic conditions.
There has therefore been much activity by workers in the field to increase percarbonate stability so as to make it a viable component of detergent formulations. This activity has tended to concentrate on the protection of the percarbonate by coating the crystalline product or by inclusion of stabilizing agents during its manufacture, or both. Thus, while it has proved possible to incorporate percarbonate salts in conventional detergent compositions so as to have acceptable percarbonate stability over periods reflecting normal product shelf life, the percarbonate salts have proved complex and expensive to manufacture. This has restricted their broadscale utilization, as evidenced by the relatively small number of commercially available products containing percarbonate.
It is therefore an object of the present invention to provide a dry laundry bleaching composition incorporating an alkali metal percarbonate bleach, said bleach displaying improved stability both upon the manufacture and the storage of said dry laundry bleaching composition.
It is a further object of the present invention to provide a dry laundry bleaching composition incorporating an alkali metal percarbonate bleach displaying improved stability, in which the percarbonate bleach does not require complex protection techniques.
It has now been found that these objects could be met by formulating a composition comprising an alkal
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Paterson Jamie
Trani Marina
Anthony Joseph D.
Aylor Robert B.
The Procter & Gamble & Company
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