Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
1998-03-09
2001-12-11
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Solid, shaped macroscopic article or structure
C510S294000, C510S298000, C510S356000, C510S360000, C510S361000, C510S511000
Reexamination Certificate
active
06329335
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to tabletted detergents. More particularly, the invention relates to a process for the production of detergent tablets, in which advantageous product properties, such as hardness, fracture resistance and good solubility, are combined with process advantages, such as minimal outlay on machinery, low tabletting forces and low temperatures.
Detergent tablets have been widely described in the prior-art literature and are becoming increasingly popular among consumers because they are easy to dose. Tabletted detergents have a number of advantages over powder-form detergents: they are easier to dose and handle and, by virtue of their compact structure, have advantages in regard to storage and transportation. Accordingly, detergent tablets are also comprehensively described in the patent literature.
2. Discussion of Related Art
Thus, EP-A-0 522 766 (Unilever) describes tablets of a compacted particulate detergent composition, the particles being at least partly coated with a material which acts both as a binder and as a disintegrating agent when the tablets are dissolved in water. The document in question also refers to the general difficulties involved in producing tablets combining adequate stability with good dissolvability. The particle size in the mixture to be tabletted should be above 200 &mgr;m and the upper and lower limits to the individual particle sizes should not be more than 700 &mgr;m apart from one another.
Other documents concerned with the production of detergent tablets include EP-A-0 716 144 (Unilever), which describes tablets with an outer shell of water-soluble material, and EP-A-0 711 827 (Unilever) which mentions a citrate having defined solubility as an ingredient.
The use of binders, more particularly polyethylene glycol, is disclosed in EP-A-0 711 828 (Unilever) which describes detergent tablets produced by tabletting a particulate detergent composition at temperatures between 28° C. and the melting point of the binder, tabletting always being carried out below the melting temperature. It is apparent from the Examples of this document that the tablets produced in accordance with its teaching have higher fracture resistances when tabletting is carried out at elevated temperature.
All the documents cited above use high tabletting pressures above 15 N/cm
2
in the tabletting process to obtain sufficiently stable tablets. The tabletting processes are optionally carried out at elevated temperature because stability is said to be further increased by a form of “sintering”.
The problem addressed by the present invention was to provide a simplified process for the production of tablets which would out-perform known tablets in regard to fracture resistance, stability in storage and dissolving behavior.
DESCRIPTION OF THE INVENTION
Accordingly, the present invention relates to a process for the production of detergent tablets containing surfactants, builders and optionally other detergent ingredients by tabletting a particulate detergent composition,
a) 5 to 20% by weight of an overdried amorphous silicate,
b) 0.5 to 10% by weight of polyethylene glycol and
c) 1 to 15% by weight of water or aqueous solutions,
based on the weight of the tablet formed, being used for the production of the tablets.
To produce the detergent tablets, a powder-form or granular free-flowing compound is tabletted in suitable molds in the process according to the invention. The tabletting process may be carried at any temperature and under any pressure. Whereas, normally, only high tabletting pressures and/or temperatures lead to sufficiently stable tablets, detergent tablets which out-perform conventional tablets in regard to stability, even when produced under tabletting pressures below 15 N/cm
2
, can be obtained by the process according to the invention. There is also no need for tabletting to be carried out at elevated temperature in the process according to the invention although tabletting at a relatively high temperature can be useful and does not lead to any loss of the advantages of the process according to the invention. Normally, an increase in temperature for the same tabletting pressure provides the tablets with a higher fracture resistance. The combination of a reduced tabletting pressure and elevated temperature leads to tablets which have a high dissolving rate despite their high fracture resistance. However, the process according to the invention is preferably carried out with tabletting pressures below 15 N/cm
2
and at temperatures below 30° C. which leads to moldings that out-perform conventional detergent tablets in regard to stability and dissolving behavior. The low tabletting temperatures have an advantageous effect in particular when the tablets contain temperature-labile ingredients which would tend to decompose at elevated temperatures.
The particulate detergent composition to be tabletted essentially contains 5 to 20% by weight of an overdried amorphous silicate, 0.5 to 10% by weight of polyethylene glycol and 1 to 15% by weight of water or aqueous solutions of other active ingredients and auxiliaries. By virtue of this special composition, detergent tablets combining high stability with excellent dissolving behavior are obtained even at low tabletting pressures and without the use of high temperatures. The particulate detergent composition to be tabletted may be prepared in known manner and, in principle, may have any bulk density. Thus, parts of the composition or even the complete composition may be prepared by spray drying or roll compacting. However, the particulate detergent composition is prepared with particular advantage by granulation and compacting of the ingredients or individual compounds in mixer/granulators. Granulation may be carried out both in high-intensity mixers and in low-speed mixers. Examples of high-speed mixers are the Lödige® CB Recycler (trademark of Lödige Maschinenbau GmbH, Paderborn), the Fukae® FS-G mixers (trademark of Fukae Powtech, Kogyo CO., Japan), the Eirich® Type R mixer (trademark of Maschinenfabrik Gustav Eirich, Hardheim) or the Drais® K-TTP 80 (trademark of Drais-Werke GmbH, Mannheim). Examples of low-speed mixer/granulators are the Drais® K-T 160 and the Lödige® KM 300. The latter, which is often referred to as a “Lödige plowshare mixer”, is particularly suitable for carrying out this stage of the process.
In one particularly preferred embodiment of the production of the compound to be tabletted, the overdried amorphous silicate is initially introduced into the mixer used for the mixing/granulation stage, other optional builders and auxiliaries are added and, after the mixer has been switched on, water or aqueous solutions are added, after which the surfactants or surfactant compounds are introduced. The other detergent ingredients, such as bleaching agents, enzymes, soil repellents and the like are then added in the so-called working-up stage. The polyethylene glycol used as component b) may be added together with the surfactant compounds in the first step or with the other ingredients in the working-up step. It is preferably added in the working-up step. The polyethylene glycol may be added in any of the usual commercial forms of which the melting points vary according to the molecular weight distribution. Polyethylene glycol having an average molecular weight of 1,500 dalton (PEG 1500) melts at 45° C. for example whereas polyethylene glycols with molecular weights of 4,000 dalton (PEG 4000) and 6,000 dalton (PEG 6000) melt at around 55° C. and 62° C., respectively. PEG 4000 is preferably used, being added in quantities of 0.5 to 10% by weight and preferably in quantities of 1 to 4% by weight, based on tablet weight. In addition, organic polymers which, in combination with the polyethylene glycol, contribute to the strength of the tablets obtained may be added during the tabletting process. Examples of such organic polymers are polyvinyl pyrrolidone, polyacrylates and copolymers of maleic acid and acrylic acid.
The bulk density of th
Feist Michael
Kruse Hans-Friedrich
Douyon Lorna M.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Murphy Glenn E. J.
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