Washing tablets marked with indicia on their surfaces

Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure

Reexamination Certificate

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C510S447000, C101S035000

Reexamination Certificate

active

06677296

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to washing tablets marked with indicia on their surfaces and to processes for marking indicia on the surfaces of washing tablets. In addition, this invention relates to the marked tablets in combination with a packaging system.
BACKGROUND OF THE INVENTION
Washing compositions in tablet form (hereinafter referred to as “washing tablets”) are made from compacted particulate material. They are used for several applications, including laundry washing, machine dish-washing, toilet hygiene and bathing. Although this invention is primarily directed at laundry and machine dish-wash tablets, it is also applies to other types of washing tablets as will be apparent to the person skilled in the art.
It is very well known to present indicia the surfaces of soap bars by means of an applied label bearing the indicia. However, it is not appropriate to label compacted particulate washing tablets in this way because the label will become detached in the wash cycle and could clog the filter of the machine.
There are a number of options for manufacturing washing compositions, particularly those employed in laundry and machine dish-washing. Such compositions have for many years been manufactured in particulate form, commonly referred to as powders. More recently, washing compositions have also been manufactured as liquids. Tablets, to which this invention relates, are yet another possibility.
Washing tablets have, potentially at least, several advantages over powder and liquid products. They do not require the user to measure out a volume of powder or liquid. Instead, one or more tablets provide an appropriate quantity of the composition for the particular application to which the composition is directed. For example, one or more tablets will provide an appropriate quantity of composition for washing a single load in a laundry or dish-washing machine, or an appropriate quantity of washing composition in a vessel for bathing. Tablets are therefore easier for the consumer to handle and dispense, and being more compact, facilitate more economical storage.
Washing tablets are generally made by compressing or compacting a quantity of the washing composition in particulate form. Materials which specifically aid tablet formation can be added to the washing composition prior to compaction, however such materials are typically added in small amounts and usually account for less than 10%, preferably less than 5% by weight of the tabletted washing composition.
It is desirable that washing tablets should have adequate strength when dry, yet have the appropriate dispersion and dissolution characteristics for the particular function they are to perform. In the case of laundry tablets it is desirable that the tablets disperse and dissolve relatively quickly in the wash water. Generally speaking, washing tablets of the present invention disperse and dissolve significantly quicker that other types of tablets. For example, most pharmaceutical tablets are specifically designed to be delivered orally but not to break up and dissolve in the mouth, i.e. they are designed to dispense and dissolve in the stomach and intestine. For this reason, pharmaceutical tablets have very different physical characteristics from those of washing tablets.
The colour of washing tablets is generally determined by the colour of the particulate ingredients being compacted. For example, coloured specks may be added to a white powder to produce a speckled tablet, or a blue powder may be compacted to produce a blue tablet. In order to obtain a two-coloured “layered” tablet, two separate particulate compositions need to be used. The colour may be the only difference in composition between two layers in a washing tablet. In such a case, “layering” is used for aesthetic reasons and/or to indicate to the consumer that the product performs two particular actions, i.e. it has a “double-action”. Clearly, in such cases, it would be advantageous if the tablet could be compacted from a single particulate composition and colour applied to the formed tablet to give the appearance of layering. This would remove the need to have more than one particulate washing composition as starting material.
Manufacturers of washing tablets typically produce several variants of tablets, providing information regarding the particular variant on the tablet packaging. For example, in the case of laundry tablets, details of the brand name and brand type (e.g. non-biological, colour-care etc.) are usually found on the tablet packaging. This means that each tablet variant has to have its own primary packaging appropriately labelled. If tablets were marked with indicia indicating such details as brand name and type, then the need to put this information on the tablet packaging would be negated. Indeed, the same packaging could be used for all the variants. Furthermore, transparent packaging would allow the markings on the tablet to be observed through the packaging. This would offer considerable supply chain advantages, in particular in terms of time and cost savings.
It is known to use ink jet printing to print a picture, patterns and/or characters on a solid bath salt, as disclosed in JP-A-61 092696. However, bath salts do not present the same kind of technical problem for surface marking, as do washing tablets.
To date, the skilled person has not succeeded marking washing tablets on their surfaces, and in particular laundry and machine-dish wash tablets, for a series of reasons. These include the following:
i) Washing tablets are prepared by compaction of relatively large coarse particles. The compaction pressures are relatively low and the material being compacted is primarily washing composition, i.e. no or relatively small amounts of ingredients specifically to aid tablet formation are present. As a result, washing tablets tend to have very rough undulating surfaces which have a tendency to rub off easily. This is one reason why washing tablets are usually packaged individually or in pairs. Furthermore, the “undulations”, which to a certain extent are an artefact of the coarseness of the particulate starting material, are large relative to the size of the indicia one might wish to apply.
ii) Washing tablets are often made up of a multitude of components. For example, a laundry tablet may typically comprise surfactants, builders, sequestrants, soil-release agents, bleaches, fluorescers, enzymes, perfumes etc. Such a tablet would be prepared by mixing a number of particulate ingredients together to produce the right formulation and then compacting the resulting particulate mixture. This results in a laundry tablet which differs dramatically in its chemical composition across its surface.
iii) Many washing tablets contain particular chemical components, such as bleaches and dye transfer inhibitors, which could interact with a colourant used to mark the tablet.
iv) Many washing tablets have an alkaline pH, for example in excess of 9 or even 10. Many colourants are pH sensitive.
v) Washing tablets are highly absorbent. This means that most solvents hitting their surface will be absorbed very quickly, which in the case of a colourant, could lead to a chromatography effect and loss of definition. This would be highly undesirable.
vi) There is a need to ensure that any marking applied to the tablets does not compromise the performance of the washing tablet. For example, in the case of a laundry tablet, if a colourant is used to mark indicia on the tablet, this must not soil the clothes.
Surprisingly, in spite of the surface roughness, the surface's tendency to rub off, the high absorbency and the variation in chemical composition that can occur across the surface, we have found it is possible to mark washing tablets with indicia on their surface and that the visibility and definition of the indicia produced are high and remain high for a significant length of time.
Clearly any marking process must not compromise the integrity of the tablets and be amenable to incorporation into a high-speed, automated, continuous production li

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