Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
2000-08-02
2002-11-05
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Solid, shaped macroscopic article or structure
C510S224000, C510S294000, C510S298000, C510S488000
Reexamination Certificate
active
06475978
ABSTRACT:
This invention relates to compositions in the form of tablets, containing a water-softening agent, methods of making a granular material for use in these tablets, and methods of making these tablets. These tablets may be embodied as detergent compositions for use in fabric washing, or as water-softening tablets, which could be used in fabric washing jointly with a composition containing detergent active, or could possibly be used in other applications, e.g. in machine dishwashing as an anti-limescale product.
Detergent compositions in tablet form have been described in a number of documents including, for example, GB 911204 (Unilever), WO 90/02165 (Henkel) and EP-A-711827 (Unilever) and are sold now commercially. Tablets have several advantages over powdered products: they do not require measuring and are thus easier to handle and dispense into the washload, and they are more compact, hence facilitating more economical storage.
Detergent tablets are generally made by compressing or compacting a detergent powder, which includes detergent active and detergency builder. EP-A-522766 explains that difficulty has been found in providing tablets which have adequate strength when dry, yet disperse and dissolve quickly when added to wash water. The problem has proved especially difficult with compositions containing insoluble aluminosilicate as detergency builder but also arises with compositions which contain sodium tripolyphosphate or other water-soluble builder.
EP-A-711827 teaches that speed of disintegration of tablets can be improved by including the highly water-soluble salt, sodium citrate. Tablet compositions exemplified in that document include sodium citrate dihydrate and also polyethylene glycol as an organic polymeric binder. This document briefly mentions that sodium acetate can be included in a composition as a lubricant to aid tableting. No information is given concerning the form in which sodium acetate might be incorporated as a lubricant. The amount of lubricant is not stated, but it would be appropriate to include only a small amount.
Detergent tablet compositions comprising acetates are also known from EP 264 701.
Detergent compositions comprising acetate are also known from DD 247 840, GB 2 318 575, EP 881 282 and U.S. Pat. No. 4,587,031. The inter-calcinating of potassium acetate molecules in clay particles is known from U.S. Pat. No. 5,672,555.
EP-A-838519 discloses that sodium acetate trihydrate and potassium acetate can function alone, or together, or in combination with sodium citrate dihydrate as effective tablet disintegrants in water-softening tablets. When mixtures of salts are used, crystals of each salt are incorporated into the overall mixture.
Surprisingly, we have now found that the amount of acetate in a tablet can be reduced whilst maintaining tablet solubility, by providing the acetate granulated with other ingredients in the same granule. These granules can be included in the tablet in approximately the same amount as known acetate granules or powder and have greater effect on the tablet solubility than might be expected from their content of acetate alone.
Broadly, the present invention provides a tablet of a compacted particulate composition wherein the tablet or a region thereof contains a water-softening agent and either sodium acetate or potassium acetate or both (the acetate), wherein the acetate is present in granules which contain at least one other ingredient.
The amount of water-softening agent will generally be at least 15% by weight of the composition of the tablet or region thereof. Depending on the function for which the tablets are intended the amount may range up to 90% by weight. In significant forms of this invention there is at least 15%, by weight of the composition, of a water-insoluble water softening agent.
Generally, the content of acetate in these granules is at least 0.1 mole per 100 gram of granules.
Thus, if the acetate is present as sodium acetate trihydrate, the weight percentage of sodium acetate trihydrate in the granules will be at least 13.6% of their weight. If, however, the acetate is present as anhydrous sodium acetate the amount of sodium acetate in the granules will thus be at least 8.2% of their weight. It is also possible that the sodium acetate is present in a partially hydrated form.
If the acetate is present as potassium acetate, the amount of potassium acetate in the granules will be at least 9.8% of their weight.
The acetate may be present as a mixture of any of these forms.
The lower limit of the acetate content of the granules may be 0.15, 0.25 or even 0.3 mole per 100 gram of granules.
It is unlikely that the content of acetate in the granules will exceed 1 mole per 100 gram of granules. Indeed, that content cannot be achieved with fully hydrated sodium acetate. The content may not exceed 0.65 mole per 100 gram of granules which would correspond to 53% by weight of anhydrous sodium acetate, 88% of sodium acetate trihydrate, or 66% by weight of potassium acetate.
A water-softening tablet of the invention is likely to contain at least 10% by weight of these acetate-containing granules, possibly at least 13% or 15%. It is unlikely that it will contain more than 35% of the granules, and may contain only up to 22% or 30% of the granules.
Accordingly, one aspect the present invention provides a tablet of a compacted particulate composition wherein the tablet or a region thereof comprises from 15 to 90% by weight of a water-softening agent, sodium and/or potassium acetate and optionally other ingredients, characterised in that the tablet or region contains at least 10% by weight of granules which contain both said acetate and at least one other ingredient, the content of said acetate in these granules being at least 0.1 mole per 100 gram of granules and the other ingredients being at least 5% by weight of the granules. Thus the acetate is no more than 95% by weight of the granules.
The total content of the acetate in the tablet or region may be only 0.01 Mol/100 g, or it may be 0.02 Mol/100 g, or 0.05 Mol/100 g. It is likely that there will be no more than 0.425 Mol/100 g of the acetate in the tablet or region, and the upper limit may be 0.3 Mol/100 g, or as low as 0.2 Mol/100 g, 0.15 Mol/100 g or even 0.1 Mol/100 g.
It is preferred that more than half of all the acetate in the tablet or region is contained in the granules, and as much as 75%, 90% or even all of the acetate may be in the granules (hereinafter referred to as “co-granules”).
It is also preferred that the acetate is sodium acetate.
By reducing the amount of acetate required in a tablet to achieve satisfactory dissolution times, the present invention allows the amounts of other ingredients in the tablets to be increased may enable improvements in performance of the tablets to be made.
It is further preferred that the other ingredients of the co-granule are present in an amount of at least 10, 15 or 20% by weight of the granules.
It is also preferred that when the acetate is sodium acetate, the amount of water (bound or unbound) present in the co-granules is such as to be in a molar ratio of 2.5:1 to 3.5:1 to the sodium acetate. A second aspect of the invention provides a method of making the acetate co-granules described above, including the steps of neutralising acetic acid with a solid basic compound and granulating the resulting mixture, wherein in that the amount of solids added to the acetic acid includes sufficient basic compound to neutralise the acetic acid, and further material which forms the co-granule with the acetate.
In one embodiment, at least some or all of the further material is the same as the basic compound, so that an excess of the basic compound, compared to the stoichiometric amount required for neutralisation, is added to the acetic acid.
This method may be used to make granules containing either sodium or potassium acetate or both. The nature of the acetate depends on the solid basic compound used.
If making sodium acetate, it is preferred that the acetic acid is used in solution rather than as its glacial form, in o
Appel Peter Willem
Janssen Roger Joseph
Douyon Lorna M.
Mitelman Rimma
Unilever Home & Personal Care USA a division of Conopco, Inc.
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