Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Utility Patent
1999-06-04
2001-01-02
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S298000, C510S360000, C510S361000, C510S441000, C510S446000, C510S470000, C510S473000, C510S474000, C510S477000, C510S507000, C510S509000, C510S511000
Utility Patent
active
06169062
ABSTRACT:
The present invention relates to coated detergent tablets, especially those adapted for use in washing machines, and to processes for making the coated detergent tablets.
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 require a relatively complex manufacturing process. In particular, it is often desirable to provide the tablet with a coating and this adds to the difficulties of manufacture.
While tablets without a coating are entirely effective in use, they usually lack the necessary surface hardness to withstand the abrasion that is a part of normal manufacture, packaging and handling. The result is that uncoated tablets suffer from abrasion during these processes, resulting in chipped tablets and loss of active material.
Finally, coating of tablets is often desired for aesthetic reasons, to improve the outer appearance of the tablet or to achieve some particular aesthetic effect.
Numerous methods of tablet coating have been proposed, and many of these have been suggested for detergent tablets. However, all of these methods have certain disadvantages, as will be explained below.
GB-A-0 989 683, published on Apr. 22, 1965, discloses a process for preparing a particulate detergent from surfactants and inorganic salts; spraying on water-soluble silicate; and pressing the detergent particles into a solid form-retaining tablet. Finally a readily water-soluble organic film-forming polymer (for example, polyvinyl alcohol) provides a coating to make the detergent tablet resistant to abrasion and accidental breakage.
EP-A-0 002 293, published on Jun. 13, 1979, discloses a tablet coating comprising hydrated salt such as acetate, metaborate, orthophosphate, tartrate, and sulphate.
EP-A-0 716 144, published on Jun. 12, 1996, also discloses laundry detergent tablets with water-soluble coatings which may be organic polymers including acrylic/maleic co-polymer, polyethylene glycol, PVPVA, and sugar.
WO9518215, published on Jul. 6, 1995, provides water-insoluble coatings for solid cast tablets. The tablets are provided with hydrophobic coatings including wax, fatty acid, fatty acid amides, and polyethylene glycol.
A disadvantage of the prior art disclosures is that a coating which is thick enough and strong enough to withstand abrasion, also tends to be slow to break up or dissolve in use.
The present invention provides a means by which tablets with a core which is formed by compressing a particulate material, the particulate material comprising surfactant and detergent builder, can be provided with a hard, thin, coating so that they can be stored, shipped and handled, but the coating is broken when the tablet is in the washing machine exposing the soft core which breaks up easily and rapidly, releasing the active ingredients into the wash solution.
The objective of the present invention is to provide a tablet which completely disintegrates and disperses, in particular in alkaline or surfactant-rich solutions such as the wash liquor.
SUMMARY OF THE INVENTION
The object of the present invention is achieved by providing a tablet which further comprises a disintegrant, at least some of the disintegrant being in the coating. It is preferred that the tablet further comprises an effervescent, for example a soluble acid source and an alkali metal carbonate.
In a further aspect of the invention there is provided a process for making a tablet comprising the steps of:
(a) forming a core by compressing a particulate material, the particulate material comprising surfactant and detergent builder;
(b) applying a coating material to the core, the coating material being in the form of a melt;
(c) allowing the molten coating material to solidify;
wherein the coating material comprises a disintegrant. Preferably the coating materials have a melting point in the range of from 40° C. to 200° C.
In an alternative to this embodiment of the invention there is provided a process for making a tablet comprising the steps of:
(a) forming a core by compressing a particulate material, the particulate material comprising surfactant and detergent builder;
(b) applying a coating material to the core, the coating material being dissolved in a solvent;
(c) allowing the solvent to evaporate;
wherein the coating material comprises a disintegrant.
DETAILED DESCRIPTION OF THE INVENTION
Tablets to be coated in the present invention can be prepared simply by mixing the solid ingredients together and compressing the mixture in a conventional tablet press as used, for example, in the pharmaceutical industry. Any liquid ingredients, for example the surfactant or suds suppressor, can be incorporated in a conventional manner into the solid particulate ingredients. Preferably the principal ingredients, are used in particulate form.
In particular for laundry tablets, the ingredients such as builder and surfactant can be spray-dried in a conventional manner and then compacted at a suitable pressure. The detergent tablets can be made in any size or shape and can, if desired, be surface treated before coating, according to the present invention. In the core of the tablet is included a surfactant and a builder which normally provides a substantial part of the cleaning power of the tablet. The term “builder” is intended to mean all materials which tend to remove calcium ion from solution, either by ion exchange, complexation, sequestration or precipitation.
The particulate material used for making the tablet of this invention can be made by any particulation or granulation process. An example of such a process is spray drying (in a co-current or counter current spray drying tower) which typically gives low bulk densities 600 g/l or lower. Particulate materials of higher density can be prepared by granulation and densification in a high shear batch mixer/granulator or by a continuous granulation and densification process (e.g. using Lodige® CB and/or Lodige® KM mixers). Other suitable processes include fluid bed processes, compaction processes (e.g. roll compaction), extrusion, as well as any particulate material made by any chemical process like flocculation, crystallisation sentering, etc. Individual particles can also be any other particle, granule, sphere or grain.
The particulate materials may be mixed together by any conventional means. Batch is suitable in, for example, a concrete mixer, Nauta mixer, ribbon mixer or any other. Alternatively the mixing process may be carried out continuously by metering each component by weight on to a moving belt, and blending them in one or more drum(s) or mixer(s). A liquid spray-on to the mix of particulate materials (e.g. non-ionic surfactants) may be carried out. Other liquid ingredients may also be sprayed on to the mix of particulate materials either separately or premixed. For example perfume and slurries of optical brighteners may be sprayed. A finely divided flow aid (dusting agent such as zeolites, carbonates, silicas) can be added to the particulate materials after spraying the non-ionic, preferably towards the end of the process, to make the mix less sticky.
The tablets may be manufactured by using any compacting process, such as tabletting, briquetting, or extrusion, preferably tabletting. Suitable equipment includes a standard single stroke or a rotary press (such as Courtoy®, Korch®, Manesty®, or Bonals®. The tablets prepared according to this invention preferably have a diameter of between 40 mm and 50 mm, and a weight between 25 and 60 g. The compaction pressure used for preparing these tablets need not exceed 5000 kN/m
2
, preferably not exceed 3000 kN/m
2
, and most preferably not exceed 1000 kN/m
2
.
According to the present invention, the tablets are then coated with a coating so that the tablet does not absorb moisture, or absorbs moisture at only a very slow rate. The coating is also strong so that moderate mechanical shocks to
Salager Serge
Van Dijk Paul Irma Albertus
Van Poucke Jeroen
Douyon Lorna M.
Dressman Marianne
Miller Steven W.
The Procter & Gamble & Company
William Zerby Kim
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