Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
2001-09-04
2004-08-03
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
Reexamination Certificate
active
06770616
ABSTRACT:
TECHNICAL FIELD
The present invention relates to multi-phase detergent tablets. In particular, it relates to multi-phase detergent tablets having improved robustness and product integrity together with excellent dissolution characteristics. The invention also relates to methods of manufacturing multi-phase detergent tablets and to detergent auxiliary compositions useful therein.
BACKGROUND
Detergent compositions in tablet form are known in the art. It is understood that detergent compositions in tablet form hold several advantages over detergent compositions in particulate form, such as ease of dosing, handling, transportation and storage.
Detergent tablets are most commonly prepared by pre-mixing components of a detergent composition and forming the pre-mixed detergent components into a tablet using any suitable equipment, preferably a tablet press. Tablets are typically formed by compression of the components of the detergent composition so that the tablets produced are sufficiently robust to be able to withstand handling and transportation without sustaining damage. In addition to being robust, tablets must also dissolve sufficiently fast so that the detergent components are released into the wash water as soon as possible at the beginning of the wash cycle.
However, a dichotomy exists in that as compression force is increased, the rate of dissolution of the tablets becomes slower. The present invention therefore seeks to find a balance between tablet robustness and tablet dissolution.
Solutions to this problem, as seen in the prior art, have included compressing the tablets with low compression pressure. However tablets made in this way, although having a fast relative dissolution rate, tend to crumble, becoming damaged and unacceptable to the consumer. Other solutions have included preparing tablets using a high relative compression pressure, in order to achieve the required level of robustness, and comprising a dissolution aid, such as an effervescent agent.
Multi-phase detergent tablets described in the prior art are prepared by compressing a first composition in a tablet press to form a substantially planar first layer. A further detergent composition is then delivered to the tablet press on top of the first layer. This second composition is then compressed to form another substantially planar second layer. Thus the first layer is generally subjected to more than one compression as it is also compressed during the compression of the second composition. Typically the first and second compression forces are in the same order of magnitude. The Applicant has found that where this is the case, because the compression force must be sufficient to bind the first and second compositions together, the force used in both the first and second compression steps must be in the range of from about 4,000 to about 20,000 kg (assuming a tablet cross-section of about 10 cm
2
). A consequence of this is a slower rate of tablet dissolution. Other multi-phase tablets exhibiting differential dissolution are prepared such that the second layer is compressed at a lower force than the first layer. However, although the dissolution rate of the second layer is improved, the second layer is soft in comparison to the first layer and is therefore vulnerable to damage caused by handling and transportation. Moreover, the two layers are found to have poor adhesion characteristics and can break up under the relatively mild stress conditions found in storage or transportation.
The present invention therefore provides multi-phase detergent tablets for use in automatic dishwashing, laundry, etc and which have improved integrity and robustness together with excellent dissolution characteristics. The invention also provides methods of manufacturing multi-phase detergent tablets and detergent auxiliary compositions useful therein.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a multi-phase detergent tablet for use in a washing machine, the tablet comprising a first phase in adhesive contact with one or more second phases, and wherein at least the first phase is in the form of a compressed particulate solid incorporating a cogranulated detergency additive composition comprising polymeric polycarboxylate and inorganic carrier.
The compositions of the invention thus comprise multiple phases in adhesive contact with one another, at least a first phase of which is in the form of a compressed particulate solid incorporating cogranules of a detergency additive composition. In preferred embodiments, at least one and preferably each second phase is also in the form of a compressed particulate solid and, if desired, can also incorporate cogranules of the same or different detergency additive composition. Surprisingly, inclusion of the detergency additive composition in the first phase improves inter-phase adhesion at a given tablet compaction force (even where the second phase is free of cogranulated additive composition) and allows a significant reduction in compaction force on both first and second phases whilst delivering improved tablet solubility and bite strength.
A preferred cogranulated detergency additive composition for incorporation herein comprises i) from about 0.1% to about 60%, preferably from about 1% to about 25%, more preferably from about 5% to about 20% by weight thereof of polymeric polycarboxylate, ii) from about 40% to about 99.9%, preferably from about 70% to about 99%, more preferably from 80% to about 95% by weight thereof of inorganic carrier, and optionally iii) from 0% to about 50%, preferably from about 0.5% to about 20% by weight thereof of one or more organic auxiliaries, preferably selected from chelating agents, surfactants, polymeric disintegrants, solubility aids and mixtures thereof.
Polymeric polycarboxylates suitable for inclusion in the detergency additive composition include i) homo- and copolymers of one or more carboxylic monomers selected from acrylic acid, methacrylic acid, alpha-chloroacrylic acid, alpha-hydroxyacrylic acid, maleic acid, itaconic acid, and mixtures thereof, and ii) copolymers of one or more of the above carboxylic monomers with one or more nonionic monomers selected from acrylamide, acrylonitrile, vinyl esters such as vinyl acetate, methylvinyl ketone, acrolein, styrene and alpha-methyl styrene, alkyl vinyl ethers, esters and amides of carboxylic monomers such as (C
1
-C
4
)-alkyl (meth)acrylates, and water-soluble salts and mixtures thereof. Of the above, preferred are homo- and copolymers of acrylic and methacrylic acid
The polymeric polycarboxylates herein can be in acid, neutralised or partially neutralised form with sodium, potassium, ammonium or other counterions. Molecular weights of the polymeric polycarboxylates can vary widely e.g. weight averages ranging from about 500 to about 5,000,000, but normally weight average molecular weights will fall in the range from about 1000 to about 100,000. Preferably, the polymeric polycarboxylates will be in liquid or liquifiable form, for example as a solution, dispersion, slurry or emulsion in a liquid or liquifiable medium such as water or a water/organic solvent mixture. Generally, liquid or liquifiable polymeric polycarboxyate mixtures suitable for use herein have a polymer solids content of at least about 10%, preferably from about 20% to about 70%, more preferably from about 40% to about 60% by weight thereof.
The inorganic carrier herein generally comprises one or more inorganic salts and in preferred embodiments is selected from alkali metal silicate, alkali metal carbonate, alkali metal bicarbonate, alkali metal sesquicarbonate, alkali metal sulfate, alkali metal tripolyphosphate, and mixtures thereof. Of these, highly preferred is an inorganic carrier which comprises a mixture of alkali metal carbonate and alkali metal sulfate, preferably in a weight ratio of from about 3:1 to about 1:3, more preferably from about 2:1 to about 1:1, and especially from about 1.8:1 to about 1.5:1. The inorganic carrier normally takes the form of a powder or mixture of powders
Kinloch James Iain
McGowan Steven Baldwin
McGregor Alasdair Duncan
Douyon Lorna M.
The Procter & Gamble & Company
Waugh Kevin L.
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