Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Patent
1996-04-19
1998-05-05
McGinty, Douglas J.
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
510375, 510376, 510441, 25218627, 25218638, C11D 708, C11D 718
Patent
active
057474389
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to particulate solid machine dishwashing detergent compositions containing a coated percarbonate bleach component, a bleach activator component, an acidification agent and a means for enabling delayed release of said acidification agent into the wash solution.
BACKGROUND OF THE INVENTION
Detergent compositions designed for use in automatic dishwasher machines are well known, and a consistent effort has been made by detergent manufacturers to improve the cleaning and/or rinsing efficiency of said compositions on dishes and glassware, as reflected by numerous patent publications.
The inorganic perhydrate bleach most widely used in machine dishwashing detergent compositions 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. Sodium percarbonate is an attractive perhydrate for use in detergent compositions because it dissolves readily in water, is weight efficient and, after giving up its available oxygen, provides a source of carbonate ions to the wash solution.
The inclusion of percarbonate salts in detergent compositions has been restricted hitherto by the relative instability of such salts in the detergent matrix environment. In particular, percarbonate salt components of such detergent compositions decompose rapidly when stored in moist and/or warm atmospheres. It is known that acceptable storage characteristics may however be obtained through the protection of the percarbonate by coating the crystalline product, or by the inclusion of stabilizing agents during its manufacture, or both. A variety of suitable coating agents have been proposed including silicates and mixtures of inorganic sulphate and carbonate salts.
Laundry washing and bleaching methods using compositions containing a hydrogen peroxide source and peroxyacid bleach precursor (bleach activator) and involving an initially alkaline (e.g.: pH 10-11) wash solution, and delayed release of acid into the wash solution to provide a final wash solution of lower pH are known in the art, having been disclosed for example, in EP-A-396,287 and EP-A-290,081. Hereinafter such washing methods are referred to generally as `controlled pH release washing methods`.
It is desirable in controlled pH release washing methods that release of the hydrogen peroxide into the wash solution occurs rapidly, enabling effective perhydrolysis of the peracid precursor whilst the pH of the wash solution is in the initial alkaline region.
Where the hydrogen peroxide source is an alkali metal percarbonate salt, the coating of the percarbonate bleach, which is necessary for its storage stability in the detergent product, will act such as to inhibit the required rapid release of hydrogen peroxide into the initial alkaline wash solution. Release of the hydrogen peroxide is particularly impaired where the initial wash solution temperature is close to room temperature, e.g.; as with `cold fill` dishwashing machines. The overall performance of the washing method is thus impaired.
The Applicants have however obtained unexpectedly good cleaning performance where a composition containing a percarbonate bleach coated with a mixed carbonate/sulphate salt, is used in a `controlled pH release` machine dishwashing method.
The percarbonate is formulated in combination with a bleach activator, an acidification agent and means of delayed release of said acidification agent.
The Applicants have also found that the problem of deposition of insoluble calcium carbonate salts as spots and films on the articles in the wash, which may arise when a carbonate ion source such as percarbonate is formulated in a machine dishwashing composition, is significantly reduced in washing methods including a lower pH (i.e. pH<9.5) final wash solution. Spotting and filming of tab
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Bolam Brian M.
Dusheck Caroline L.
McGinty Douglas J.
The Procter & Gamble & Company
Zerby Kim William
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