Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Heterogeneous arrangement
Reexamination Certificate
2000-08-25
2002-01-22
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Heterogeneous arrangement
C510S224000, C510S294000, C510S298000, C510S446000, C510S475000, C510S476000
Reexamination Certificate
active
06340664
ABSTRACT:
The present invention is situated within the field of compact tablets having detersive properties. Laundry detergent and cleaning product tablets of this kind include, for example, tablets for the washing of textiles, machine dishwashing detergent tablets or hard surface cleaning product tablets, bleach tablets for use in washing machines or dishwashers, water softener tablets, and scouring salt tablets. The invention relates in particular to laundry detergent and cleaning product tablets which are used for washing textiles in a domestic washing machine, and are referred to for short as detergent tablets.
Detergent tablets have been widely described in the prior art and are enjoying increasing popularity among users owing to the ease of dosing. Tableted detergents have a number of advantages over their powder-form counterparts: they are easier to dose and to handle, and have storage and transport advantages owing to their compact structure. Consequently, laundry detergent and cleaning product tablets have been described comprehensively in the patent literature as well. One problem which occurs again and again in connection with the use of detersive tablets is the inadequate disintegration and dissolution rate of the tablets under application conditions. Since tablets of sufficient stability, i.e., dimensional stability and fracture resistance, can be produced only by means of relatively high compressive pressures, there is severe compaction of the tablet constituents and, consequently, retarded disintegration of the tablet in the aqueous liquor, leading to excessively slow release of the active substances in the washing or cleaning operation. Another problem which occurs in particular with laundry detergent and cleaning product tablets is the friability of the tablets, or their often inadequate stability to abrasion and edge fracture. Thus, although it is possible to produce sufficiently fracture-stable, i.e., hard laundry detergent and cleaning product tablets, these tablets are often not up to the loads involved in packaging, transit and handling, i.e., falling stresses and frictional stresses, with the result that edge-fracture and abrasion phenomena may impair the appearance of the tablet or may even lead to complete destruction of the tablet structure.
To overcome the dichotomy between hardness, i.e., transport and handling stability, and the ready disintegration of the tablets, numerous approaches to solutions have been developed in the prior art. One approach, which is known in particular from the field of pharmacy and has expanded into the field of laundry detergent and cleaning product tablets, is the incorporation of certain disintegration aids, which facilitate the ingress of water or which, on ingress of water, swell, evolve gas, or exert a disintegrating effect in another form. Other proposed solutions from the patent literature describe the compression of premixes of defined particle sizes, the separation of certain ingredients from certain other ingredients, and the coating of individual ingredients, or of the whole tablet, with binders.
The coating of laundry detergent and cleaning product tablets is subject-matter of a number of patent applications.
For instance, European Patent Applications EP 846 754, EP 846 755 and EP 846 756 (Procter & Gamble) describe coated laundry detergent tablets comprising a “core” comprising compacted particulate laundry detergent and cleaning product, and a “coating”, the coating materials used comprising dicarboxylic acids, especially adipic acid, which if desired comprise further ingredients, examples being disintegration aids.
Coated laundry detergent tablets are also subject-matter of European Patent Application EP 716 144 (Unilever). According to the details in that document, the hardness of the tablets may be intensified by means of a “coating” without detracting from the disintegration and dissolution times. Coating agents specified are film-forming substances, especially copolymers of acrylic acid and maleic acid, or sugars.
The prior German patent application DE 199 20 118.8 (Henkel) describes laundry detergent or cleaning product tablets coated with certain polymers or polymer mixtures, said coating materials producing thin and yet stable coats which enhance the physical properties of the tablets.
Details on the application of the coating are sparse in all of the abovementioned documents. Likewise, the majority of documents fail to specify the thickness of the coat. A further feature common to all documents is that in each case the whole tablet is provided with the coating. A consequence of this is that the dissolution or disintegration of the tablets can only ensue once the application liquor has at least partly dissolved or eroded the coating. In other words, the majority of coating agents lead to retarded disintegration, which is a problem especially when the disintegration of the tablet is intended to be brought about by means of cocompressed disintegration aids which need to come into contact with water as quickly as possible in order to develop their activity.
It is an object of the present invention to provide coated laundry detergent and cleaning product tablets with which the advantageous properties of the higher hardnesses are achievable with smaller quantities of coating agents, without detracting from the short disintegration times. In particular, the aim was to improve further the resistance of the tablets to falling and frictional loads, as compared with the known tablets, despite the markedly reduced level of use of coating materials. In this context, improving the edge-fracture stability is particularly important, since edge-fracture phenomena are perceived by the user as being a significant defect. A further object of the present invention is to provide a process for producing such coated tablets which is easy to carry out and universally applicable.
It has now been found that the abrasion stability and edge-fracture resistance of laundry detergent or cleaning product tablets may be improved without the abovementioned disadvantages by applying to the tablets a partial coating which covers only the mechanically sensitive parts of the tablets.
The invention accordingly provides laundry detergent or cleaning product tablets comprising compacted particulate laundry detergent or cleaning product and comprising builder(s), surfactant(s) and, if desired, further laundry detergent or cleaning product constituents, wherein the tablets have a coating which covers only mechanically sensitive parts of the tablet.
The term “mechanically sensitive parts” refers to those regions of the tablet that are particularly susceptible to mechanical loads. Specifically, it relates to corners and edges of the tablets, although narrow connecting pieces which, for example, delimit cavities in the tablet are included among the mechanically sensitive parts of tablets. In the latter case, the edges in question are so close to one another that the area between the edges is also covered by the coating applied in accordance with the invention. Larger planar faces such as, for example, the two circular faces of cylindrical tablets are mechanically sensitive only at the marginal regions, i.e., again at the edges, but not on the face.
If the tablets have raised or depressed areas (for example, embossed letters or geometrical structures protruding from the faces, such as hemispheres, etc.), then their marginal regions are likewise mechanically sensitive. Only a spherical tablet has no mechanically sensitive parts and is therefore not subject-matter of the present invention. If, however, there is deviation from the ideal spherical form and, for example, a biconvex tablet is provided, then this tablet is again mechanically sensitive at the annular line delimiting the two spherical sections.
The partial coating of the laundry detergent or cleaning product tablets of the invention serves to protect the mechanically sensitive regions of the tablets against excessive loads and against the attendant negative phenomena such as edge fracture, for exa
Gassenmeier Thomas
Millhoff Juergen
Schambil Fred
Douyon Lorna M.
Henkel Kommanditgesellschaft auf Aktien (KGaA)
Jaeschke Wayne X.
Murphy Glenn E. J.
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