Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
2000-12-20
2003-05-06
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Solid, shaped macroscopic article or structure
C510S294000, C510S298000, C510S495000
Reexamination Certificate
active
06559115
ABSTRACT:
The present invention relates to detergent tablets, especially those adapted for use in washing.
Although cleaning compositions in tablet form have often been proposed, these have not (with the exception of soap bars for personal washing) gained any substantial success, despite the several advantages of products in a unit dispensing form. One of the reasons for this may be that detergent tablets usually dissolve slower than the constituent powders from which they are made, simply because the constituent powders are forced close together in the tablet, with comparatively little opportunity for water to permeate between them. This gives rise to the problem that slow dissolving tablets cause residues which may for example be visible through the door of the washing machine during the wash cycle, or which stick to the fabrics at the end of the wash cycle, or both.
EP-A-0 711 827, published on the 5
th
of May 1996, discloses laundry detergent tablets containing a highly water-soluble material which improves disintegration of the whole tablet and dissolution of its soluble ingredients.
However, particularly in certain front loading washing machines, problems of tablet residues appearing visibly at the window of the washing machine have still been encountered.
The object of the present invention is to provide tablets formed by compressing a particulate material, the particulate material comprising a surfactant, the tablet being suitable for storing, shipping and handling without breakage while dissolving easily and rapidly in wash solution, releasing the active ingredients into the wash solution and completely disintegrating and dispersing in alkaline or surfactant-rich solutions such as the wash liquor.
SUMMARY OF THE INVENTION
The object of the invention is achieved by providing a tablet of the above mentioned kind, whereby the particulate material further comprises a highly soluble compound, the highly soluble compound having a cohesive effect on the particulate material.
In a further aspect of the invention a method is provided of preparing an aqueous solution of a laundry detergent for use in a washing machine, wherein the aqueous solution of laundry detergent is formed by dissolving in water a tablet formed by compressing a particulate material, the tablet comprising a surfactant and a highly soluble compound, the highly soluble compound having a cohesive effect on the particulate material.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a highly soluble compound having a cohesive effect on the particulate material.
Highly Soluble Compounds
The invention relates to a highly soluble compound. Such a compound could be formed from a mixture or from a single compound. According to the invention, a highly soluble compound is defined as follow:
A solution is prepared as follows comprising de-ionised water as well as 20 grams per liter of a specific compound:
1—20 g of the specific compound is placed in a Sotax Beaker. This beaker is placed in a constant temperature bath set at 10° C. A stirrer with a marine propeller is placed in the beaker so that the bottom of the stirrer is at 5 mm above the bottom of the Sotax beaker. The mixer is set at a rotation speed of 200 turns per minute.
2—980 g of the de-ionised water is introduced into the Sotax beaker.
3—10 s after the water introduction, the conductivity of the solution is measured, using a conductivity meter.
4—Step 3 is repeated after 20, 30, 40, 50, 1 min, 2 min, 5 min and 10 min after step 2.
5—The measurement taken at 10 min is used as the plateau value or maximum value.
The specific compound is highly soluble according to the invention when the conductivity of the solution reaches 80% of its maximum value in less than 10 seconds, starting from the complete addition of the de-ionised water to the compound. Indeed, when monitoring the conductivity in such a manner, the conductivity reaches a plateau after a certain period of time, this plateau being considered as the maximum value. Such a compound is preferably in the form of a flowable material constituted of solid particles at temperatures comprised between 10 and 80° Celsius for ease of handling, but other forms may be used such as a paste or a liquid.
Example of highly soluble compounds include Sodium di isoalkylbenzene sulphonate or Sodium toluene sulphonate.
Cohesive Effect
For the purpose of this invention, the Cohesive Effect on the particulate material of a detergent matrix is characterised by the force required to break a tablet based on the examined detergent matrix pressed under controlled compression conditions. For a given compression force, a high tablet strength indicates that the granules stuck highly together when they were compressed, so that a strong cohesive effect is taking place. Means to assess tablet strength (also refer to diametrical fracture stress) are given in Pharmaceutical dosage forms: tablets volume 1 Ed. H. A. Lieberman et al, published in 1989.
The cohesive effect induced by the highly soluble compound is measured according to the invention by comparing the tablet strength of the original base powder without highly soluble compound with the tablet strength of a powder mix which comprises 97 parts of the original base powder and 3 parts of the highly soluble compound. The highly soluble compound is added to the matrix in a form in which it is substantially free of water (water content below 10% (pref. below 5%)). The temperature of the addition is between 10 and 80 C., more pref. between 10 and 40 C.
A highly soluble compound is defined as having a cohesive effect on the particulate material according to the invention when at a given compacting force 3000N, tablets with a weight of 50 g of detergent particulate material and a diameter of 55 mm have their tablet tensile strength increased by over 30% (preferably 60 and more preferably 100%) by means of the presence of 3% of the highly soluble compound having a cohesive effect in the base particulate material.
An example of a compond having a cohesive effect is Sodium di isoalkylbenzene sulphonate.
It was found that when integrating a highly soluble compound having a cohesive effect on the particulate material according to the invention to a tablet formed by compressing a particulate material comprising a surfactant, the dissolution of the tablet in an aqueous solution was significantly increased. In a preferred embodiment, at least 1% per weight of the tablet is formed from the highly soluble compound, more preferably at least 2%, even more preferably at least 3% and most preferably at least 5% per weight of the tablet being formed from the highly soluble compound having a cohesive effect on the particulate material. It should be noted that a composition comprising a highly soluble compound as well as a surfactant is disclosed in EP-A-0 524 075, this composition being a liquid composition.
According to the present invention it was found that the highly soluble compound having a cohesive effect on the particulate material allows to obtain a tablet having a higher tensile strength at constant compacting force or an equal tensile strength at lower compacting force when compared to traditional tablets. Typically, the tablet will have a tensile strength of more than 5 kPa, preferably of more than 10 kPa, more preferably, in particular for use in laundry applications, of more than 15 kPa, even more preferably of more than 30 kPa and most preferably of more than 50 kPa, in particular for use in dish washing or auto dish washing applications; and a tensile strength of less than 300 kPa, preferably of less than 200 kPa, more preferably of less than 100 kPa, even more preferably of less than 80 kPa and most preferably of less than 60 kPa. Indeed, in case of laundry application, the tablets should be less compressed than in case of auto dish washing applications for example, whereby the dissolution is more readily achieved, so that in a laundry application, the tensile strength is preferably of less than 30 kPa.
This allows to produce tablets which have a solidity and mechanical resistance co
Tcheou Eric
Vega Jose Luis
Wevers Jean
Douyon Lorna M.
Matthews Armina E.
Miller Steven W.
The Procter & Gamble & Company
William Zerby Kim
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