Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
2001-01-17
2003-07-08
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, C008S137000, C134S025200
Reexamination Certificate
active
06589932
ABSTRACT:
TECHNICAL FIELD
The present invention relates to multi-phase detergent tablets.
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 is 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.
EP-B-0,055,100 describes a lavatory block formed by combining a slow dissolving shaped body with a tablet. The lavatory block is designed to be placed in the cistern of a lavatory and dissolves over a period of days, preferably weeks. As a means of slowing the rate of dissolution of the lavatory block, the document teaches admixing one or more solubility control agents. Examples of such solubility control agents are paradichlorobenzene, waxes, long chain fatty acids and alcohols and esters thereof and fatty alkylamides. Detergent tablets for use in laundry or automatic dishwashing must substantially dissolve within one cycle of the washing or dishwashing machine, i.e. within 15 to 120 minutes.
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) a first phase in the form of a shaped body having at least one mould therein; and
b) a second phase in the form of a particulate solid compressed within said mould.
In preferred embodiments, the first phase is a compressed shaped body prepared at an applied compression pressure of at least about 40 kg/cm
2
, preferably at least about 250 kg/cm
2
, more preferably at least about 350 kg/cm
2
(3.43 kN/cm
2
), even more preferably from about 400 to about 2000, and especially from about 600 to about 1200 kg/cm
2
(compression pressure herein is the applied force divided by the cross-sectional area of the tablet in a plane transverse to the applied force—in effect, the transverse cross-sectional area of the die of the rotary press). It is also preferred that the particulate solid of the second phase (which terminology is intended to include the possibility of multiple ‘second’ phases, sometimes referred to herein as ‘optional subsequent phases’) be compressed into said mould at an applied compression pressure less than that applied to the first phase and preferably at a compression pressure of less than about 350 kg/cm
2
, preferably in the range from about 40 kg/cm
2
to about 300 kg/cm
2
and more preferably from about 70 to about 270 kg/cm
2
, such tablets being preferred herein from the viewpoint of providing optimum tablet integrity and strength (measured for example by the Child Bite Strength [CBS] test) and product dissolution characteristics. The tablets of the invention preferably have a CBS of at least about 6 kg, preferably greater than about 8 kg, more preferably greater than about 10 kg, especially greater than about 12 kg, and more especially greater than about 14 kg, CBS being measured per the US Consumer Product Safety Commission Test Specification. Also, the compression pressures applied to the first and second phases will generally be in a ratio of at least about 1.2:1, preferably at least about 2:1, more preferably at least about 4:1.
Thus, according to a further aspect of the invention, there is provided a multi-phase detergent tablet for use in a washing machine, the tablet comprising:
a) a first phase in the form of a compressed shaped body having at least one mould therein, the shaped body being prepared at a compression pressure of at least about 350 kg/cm
2
; and
b) a second phase in the form of a particulate solid compressed within said mould, the second phase being compressed at a pressure of less than about 350 kg/cm
2
.
In other preferred embodiments, the second phase is in the form of a compressed or shaped body adhesively contained, for example by physical or chemical adhesion, within the at least one mould of the first body. It is also preferred that the first and second phases are in a relatively high weight ratio to one another, for example at least about 6:1, preferably at least about 10:1; also that the tablet composition contain one or more detergent actives (for example enzymes, bleaches, bleach activators, bleach catalysts, surfactants, chelating agents etc) which is predominantly concentrated in the second phase, for example, at least about 50%, preferably at least about 60%, especially about 80% by weight of the active (based on the total weight of the active in tablet) is in the second phase of the tablet. Again, such compositions are optimum for tablet strength, dissolution, cleaning, and pH regulation characteristics providing, for example, tablet compositions capable of dissolving in the wash liquor so as to deliver at least 50%, preferably at least 60%, and more preferably at least 80% by weight of the detergent active to the wash liquor within 10, 5, 4 or even 3 minutes of the start of the wash process.
Thus, according to another aspect of the invention, there is provided a multi-phase detergent tablet for use in a washing machine, the tablet comprising:
a) a first phase in the form of a shaped body having at least one mould therein, and
b) a second phase in the form of a particulate solid compressed within said mould, and wherein the tablet comprises at least one detergent active and is formulated such that at least 50%, preferably at least 60%, more preferably at least 80% by weight
Bennie Brenda Frances
Binder Christopher James
Ricci Patrizio
Cook C. Brank
Douyon Lorna M.
Miller Steven W.
The Procter & Gamble & Company
Zerby Kim W.
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