CA2306381A1 - Detergent tablets containing bleaching agents - Google Patents

Abstract

Detergent tablets combining high hardness with a short disintegration time can be produced if they contain percarbamide. To this end, the percarbamide is mixed with other components and the resulting mixture is tabletted to form detergents.

Description

Detergent Tablets Containing Bleaching Agents Field of the Invention This invention relates to detergent tablets containing bleaching agents. More particularly, the invention relates to laundry detergent tablets, dishwasher tablets, bleach tablets and water softener tablets containing bleaching agents.
Background of the Invention Detergent compositions in the form of tablets have long been known and are widely described in the prior art. However, tablets, despite a number of advantages, also have disadvantages which have an adverse effect both on their production and use and on their acceptance by consumers. The main advantages of tablets, such as elimination of the need to measure out the quantity of product required by the consumer, the higher density and hence the reduced packaging and storage costs and an aesthetic aspect which should not be underestimated, are offset by such disadvantages as the dichotomy between acceptable hardness and sufficiently rapid disintegration and dissolution of the tablets and numerous technological difficulties in production and packaging.
In particular, the dichotomy between a sufficiently hard tablet and a sufficiently fast disintegration time is a central problem. Since sufficiently stable, i.e. dimensionally stable and fracture-resistant, tablets can only be produced by applying relatively high tabletting pressures, the tablet ingredients are heavily compacted which delays disintegration of the tablet in the aqueous wash liquor and hence leads to excessively slow release of the active substances in the washing process. The delayed disintegration of the tablets has the further disadvantage that conventional detergent tablets cannot be flushed into the washing process from the dispensing ' CA 02306381 2000-04-20 compartment of domestic washing machines because the tablets do not disintegrate sufficiently quickly into secondary particles which are small enough to be flushed into the drum of the washing machine from the dispensing compartment.
Many proposals have been put forward in the prior art with a view to overcoming the dichotomy between hardness, i.e. transportation and handling stability, and easy disintegration of the tablets. One proposed solution which is known in particular from the pharmaceutical field and which has been extended to detergent tablets is to incorporate certain disintegration aids which facilitate the access of water or which have a swelling or effervescing or other disintegrating effect on contact with water.
Other proposed solutions from the patent literature include the tabletting of premixes with certain particle sizes, the separation of individual ingredients from certain other ingredients and the coating of individual ingredients or the tablet as a whole with binders.
Thus, EP-A-0 522 766 (Unilever) describes tablets of a compacted particulate detergent composition containing surfactants, builders and disintegration aids (for example based on cellulose), the particles being at least partly coated with the disintegration aid which shows both a binder effect and a disintegrating effect during dissolution of the tablets in water.
This document also refers to the general difficulty of producing tablets combining adequate stability with good solubility. The particle size of the mixture to be tabletted is said to be above 200 Nm, the upper and lower limits to the individual particle sizes differing by no more than 700 Nm from one another.
Other documents concerned with the production of detergent tablets are EP-A-0 716 144 (Unilever), which describes tablets with an outer coating of water-soluble material, and EP-A-0 711 827 (Unilever) which mentions a citrate of defined solubility as an ingredient.
The use of binders which optionally develop a disintegrating effect ' CA 02306381 2000-04-20 (more particularly polyethylene glycol) is disclosed in EP-A-0 711 828 (Unilever) which described detergent tablets obtained by tabletting a particulate detergent composition at temperatures of 28°C to the melting point of the binder, the tabletting process always being carried out below the melting temperature. It is clear 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.
Detergent tablets in which individual ingredients are separated from others are described, for example, in EP-A-0 481 793 (Unilever). The detergent tablets disclosed in this document contain sodium percarbonate which is separated from all other components that could affect its stability.
The document in question does not make any reference to the particle size of the bleaching agent.
European patent application EP-A-0 466 484 (Unilever) claims detergent tablets which are produced by tabletting particulate material with particle sizes of 200 to 2000 Nm, the upper and lower limits to the particle sizes differing by no more than 700 Nm. The use of bleaching agents is merely mentioned as optional in this document which, moreover, makes no reference whatever to particle size ranges for the bleaching agents.
Earlier German patent application DE 198 06 200.1 (Henkel) describes detergent tablets which contain bleaching agents with a mean particle size above 400 Nm and which are preferably free from particles below 200 Nm in size. The only Examples and Comparison Examples disclosed in this application are tablets containing sodium perborate.
None of the cited prior art documents which are concerned with detergent tablets describes the use of percarbamide. None of the documents cited above is concerned with improving the solubility of detergent tablets by the selective use of percarbamide.

Summary of the Invention Accordingly, the problem addressed by the present invention was to provide detergent tablets which would combine high hardness with excellent disintegration properties. The detergent tablets provided by the invention would also be able to be dosed from the dispensing compartment without the consumer experiencing any disadvantages through residues in the dispensing compartment and too little detergent in the wash liquor.
Besides these tablet-specific properties, the cleaning performance of the tablets according to the invention would also be exemplary. The advantageous properties of the tablets would not be achieved by additives which merely serve to improve the properties of the tablets, but rather through the selective use of substances which also develop an effect in the washing process.
The present invention relates to detergent tablets of compacted particulate detergent which contain percarbamide.
Detailed Description of the Invention The percarbamide present in the tablets in accordance with the invention is a urea peroxohydrate which may be described by the formula H2N CO NH2~H202. Percarbamide is marketed in the form of white crystals which decompose above 40°C in the presence of moisture, is readily soluble in water (800 g per liter water at 20°C) and has a melting point of 80-90°C (with decomposition). The commercial product has a bulk density of ca. 600 g/I. Theoretically, the percarbamide has a hydrogen peroxide content of 36.16% by weight; powder-form commercial products normally have hydrogen peroxide contents of at least 35% by weight. This gives an active oxygen content (AO) of 17% by weight (theoretical) or >_ 16.5% by weight in commercial powders. Additions of sodium or ammoni-um dihydrogen phosphate or zinc sulfate improve the thermal stability of the percarbamide.
Percarbamide, which is often referred to as "solid hydrogen peroxide" by virtue of its high AO content, was obtained for the first time in 1908 by Tanatar by pouring 30% H202 into a solution of urea in water and cooling the solution. On an industrial scale, it is produced in basically the same way by mixing fine-particle urea with 35% hydrogen peroxide in the 5 presence of stabilizers. Percarbamide is recovered from the resulting solutions by freezing out and concentration. The crude product separated from the mother liquor is carefully dried at 30 to 40°C. Another industrial process for the production of percarbamide comprises spraying 35% H2O2 onto an agitated bed of urea particles (fluidized bed granulation).
Percarbamide is marketed, for example, by Degussa, Solvay-Interox and Peroxid-Chemie GmbH, Pullach, and is mainly used in hair bleaching and coloring preparations, as a disinfectant (for example for contact lenses) and partly for healing wounds.
The detergent tablets according to the invention preferably contain the percarbamide in quantities of 1 to 40% by weight, preferably in quantities of 5 to 30% by weight, more preferably in quantities of 7.5 to 25% by weight and most preferably in quantities of 10 to 20% by weight, based on the weight of the tablets.
The percarbamide is preferably used in certain particle size ranges.
According to the invention, detergent tablets in which the percarbamide has a mean particle size above 0.3 mm are preferred.
In the context of the present invention, the mean particle size is a calculated quantity which is obtained by multiplying the percentage content of a sieve fraction by the mesh width of the sieve. The individual values of such mean values can be scattered over a wide range if, for example, extremely small and extremely large particles are present alongside one another. According to the invention, however, the percarbamide does not have a broad particle size distribution, but a relatively narrow particle size distribution around the mean value. In particular, so-called fines should be ruled out as far as possible so that preferred detergent tablets according to ' CA 02306381 2000-04-20 the invention are characterized in that the percarbamide present in them has a mean particle size above 0.3 mm and is preferably substantially free from particles below 0.2 mm in size.
"Substantially free" in the context of the present invention means contents below 2% by weight, preferably below 1 % by weight and more preferably below 0.5% by weight.
According to the invention, not only are percarbamide dust and fines absent as far as possible, the content of particles below 0.4 mm in size should also be kept as small as possible. Thus, preferred detergent tablets are characterized in that the percarbamide present contains less than 30%
by weight, preferably less than 20% by weight and more preferably less than 10% by weight of particles below 0.4 mm in size and preferably more than 10% by weight, preferably more than 20% by weight and more preferably more than 30% by weight of particles larger than 0.8 mm in size.
In one particularly preferred embodiment, the percarbamide is substantially free from particles larger than 1.6 mm in size.
Accordingly, the percentage of relatively large percarbamide particles should be as high as possible. In another preferred embodiment, the percarbamide particles are not only larger than 0.4 mm in size, but are distinctly larger, for example larger than 0.8 mm. Nevertheless, the percarbamide should not of course be incorporated in the form of large lumps in the detergent tablets according to the invention. From the practical point of view, particle sizes of the percarbamide below 2.0 mm have proved effective, the percarbamide present in the detergent tablets preferably being substantially free from particles larger than 1.6 mm in size (see above).
According to the invention, the percarbamide may also be granu-lated with other raw materials and adjusted to the preferred particle spectrum by grinding and sieving operations. According to the invention, therefore, compounds of which at least 60% by weight, based on the compound, consist of percarbamide may also be used, these compounds preferably satisfying the particle size criteria mentioned above. According to the invention, other preferred detergent tablets are characterized in that they contain percarbamide-containing compounds in which at least 60% by weight of percarbamide, based on the weight of the compound, is present.
According to the invention, acidic constituents may be incorporated in the tablets. If the tablets contain carbonates, carbon dioxide is released by reaction of the acid with the carbonate or hydrogen carbonate. The resulting "effervescent effect" can promote disintegration. Oligomeric oligo-carboxylic acids, such as succinic acid, malefic acid and in particular citric acid, are normally used in effervescent systems. In preferred embodiments of the present invention, however, the detergent tablet is not an "effervescent tablet", i.e. preferred detergent tablets are free from oligomeric oligocarboxylic acids, more particularly citric acid.
Technically, it is also possible to coat the tablets with a coating which covers the entire tablet. Coated detergent tablets such as these can be produced by spraying a melt or solution of the coating material onto the tablet or by immersing the tablet in the melt or solution. In preferred embodiments of the present invention, however, the detergent tablets are not provided with a coating which covers the entire tablet.
As mentioned above, detergent tablets which take more than 60 seconds to disintegrate are normally almost completely insoluble and, accordingly, cannot be flushed in from the dispensing compartment. By applying sufficiently high tabletting pressures, it is possible with any premix to produce tablets which take longer than 60 seconds to disintegrate and which experience has shown to be unsatisfactory from the performance point of view. Hitherto, therefore, an upper limit has been imposed on the tabletting pressure and hence on the hardness of the resulting tablets. By using percarbamide in accordance with the invention, it is even possible to produce relatively hard tablets which, despite disintegration times of more than 60 seconds, still disintegrate into secondary particles and can there-fore being flushed in from dispensing compartments. Although it is possible in accordance with the invention to make the tablets so hard that disintegration times of more than 2 minutes can be achieved, the produc-tion of tablets according to the invention which have disintegration times below 100 seconds is preferred from the performance point of view (flushing-in cycle of domestic washing machines). With the use according to the invention, too, readily and rapidly disintegrating tablets are preferred so that, according to the invention, particularly preferred detergent tablets are characterized in that they disintegrate completely into their secondary particles in less than 60 seconds in water at 30°C, the secondary particles being so small that they can be flushed into the washing process from the dispensing compartment of a standard domestic washing machine.
In order to facilitate the disintegration of heavily compacted tablets, disintegration aids, so-called tablet disintegrators, may be incorporated in them to shorten their disintegration times. According to Rompp (9th Edition, Vol. 6, page 4440) and Voigt "Lehrbuch der pharmazeutischen Technologie" (6th Edition, 1987, pages 182-184), tablet disintegrators or disintegration accelerators are auxiliaries which provide for the rapid disintegration of tablets in water or gastric juices and the release of the pharmaceuticals in an absorbable form.
These substances, which are also known as "disintegrators" by virtue of their effect, are capable of undergoing an increase in volume on contact with water so that, on the one hand, their own volume is increased (swelling) and, on the other hand, a pressure can be generated through the release of gases which causes the tablet to disintegrate into relatively small particles. Well-known disintegrators are, for example, carbonate/citric acid systems, although other organic acids may also be used. Swelling dis-integration aids are, for example, synthetic polymers, such as polyvinyl pyrrolidone (PVP), or natural polymers and modified natural substances, ' CA 02306381 2000-04-20 such as cellulose and starch and derivatives thereof, alginates or casein derivatives.
Preferred detergent tablets contain 0.5 to 10% by weight, preferably 3 to 7% by weight and more preferably 4 to 6% by weight of one or more disintegration aids, based on the weight of the tablet.
According to the invention, preferred disintegrators are cellulose-based disintegrators, so that preferred detergent tablets contain a cellulose-based disintegrator in quantities of 0.5 to 10% by weight, preferably 3 to 7% by weight and more preferably 4 to 6% by weight. Pure cellulose has the formal empirical composition (C6H~pO5)n and, formally, is a ~3-1,4-polyacetal of cellobiose which, in turn, is made up of two molecules of glucose. Suitable celluloses consist of ca. 500 to 5000 glucose units and, accordingly, have average molecular weights of 50,000 to 500,000.
According to the invention, cellulose derivatives obtainable from cellulose by polymer-analog reactions may also be used as cellulose-based disintegrators. These chemically modified celluloses include, for example, products of esterification or etherification reactions in which hydroxy hydrogen atoms have been substituted. However, celluloses in which the hydroxy groups have been replaced by functional groups that are not attached by an oxygen atom may also be used as cellulose derivatives.
The group of cellulose derivatives includes, for example, alkali metal celluloses, carboxymethyl cellulose (CMC), cellulose esters and ethers and aminocelluloses. The cellulose derivatives mentioned are preferably not used on their own, but rather in the form of a mixture with cellulose as cellulose-based disintegrators. The content of cellulose derivatives in mixtures such as these is preferably below 50% by weight and more preferably below 20% by weight, based on the cellulose-based disintegrator. In one particularly preferred embodiment, pure cellulose free from cellulose derivatives is used as the cellulose-based disintegrator.
The cellulose used as disintegration aid is preferably not used in fine-particle form, but is converted into a coarser form, for example by granulation or compacting, before it is added to and mixed with the premixes to be tabletted. Detergent tablets which contain pram ~lar nr optionally co-granulated disintegrators are described in German patent 5 applications DE 197 09 991 (Stefan Herzog) and DE 197 10 254 (Henkel) and in International patent application WO-A-98/40463 (Henkel). Further particulars of the production of granulated, compacted or co-granulated cellulose disintegrators can also be found in these patent applications. The particle sizes of such disintegration aids is mostly above 200 Nm, at least 10 90% by weight of the particles being between 300 and 1600 pm in size and, more particularly, between 400 and 1200 Nm in size. According to the invention, the above-described relatively coarse-particle cellulose-based disintegrators described in detail in the cited patent applications are preferably used as disintegration aids and are commercially obtainable, for example under the name of Arbocel~ TF-30-HG from Rettenmaier.
Microcrystalline cellulose may be used as another cellulose-based disintegration aid or as part of such a component. This microcrystalline cellulose is obtained by partial hydrolysis of the celluloses under conditions which only attack and completely dissolve the amorphous regions (ca. 30%
of the total cellulose mass) of the celluloses, but leave the crystalline regions (ca. 70%) undamaged. Subsequent de-aggregation of the microfine celluloses formed by hydrolysis provides the microcrystalline celluloses which have primary particle sizes of ca. 5 pm and which can be compacted, for example, to granules with a mean particle size of 200 Nm.
According to the present invention, preferred detergent tablets are those which additionally contain a disintegration aid, preferably a cellulose-based disintegration aid, preferably in granular, cogranulated or compacted form, in quantities of 0.5 to 10% by weight, preferably 3 to 7% by weight and more preferably 4 to 6% by weight, based on the weight of the tablet.
To develop the required bleaching effect, the detergent tablets ~

according to the invention contain percarbamide. According to the invention, other bleaching agents may of course also be incorporated in the detergent tablets according to the invention, the usual bleaching agents from the group consisting of sodium perborate monohydrate, sodium perborate tetrahydrate and sodium percarbonate having proved to be particularly useful. If the percarbamide is to be used together with other bleaching agents, a mixture of percarbamide and sodium percarbonate in which the ratio by weight of percarbamide to sodium percarbonate may advantageously be between 1:100 and 100:1 has proved to be effective.
"Sodium percarbonate" is a non-specific term used for sodium carbonate peroxohydrates which, strictly speaking, are not "percarbonates"
(i.e. salts of percarbonic acid), but hydrogen peroxide adducts with sodium carbonate. The commercial material has the mean composition 2 Na2C03 3 HZ02 and, accordingly, is not a peroxycarbonate. Sodium percarbonate forms a white water-soluble powder with a density of 2.14 gcm~3 which readily decomposes into sodium carbonate and bleaching or oxidizing oxygen.
Sodium carbonate peroxohydrate was obtained for the first time in 1899 by precipitation with ethanol from a solution of sodium carbonate in hydrogen peroxide, but was mistakenly regarded as peroxycarbonate. It was only in 1909 that the compound was recognised as a hydrogen peroxide addition compound. Nevertheless, the historical name "sodium percarbonate" has been adopted in practice.
On an industrial scale, sodium percarbonate is mainly produced by precipitation from aqueous solution (so-called wet process). In this pro-cess, aqueous solutions of sodium carbonate and hydrogen peroxide are combined and the sodium percarbonate is precipitated by salting-out agents (mainly sodium chloride), crystallization aids (for example polyphos-phates, polyacrylates) and stabilizers (for example Mg2+ ions). The precipitated salt which still contains 5 to 12% by weight of mother liquor is then removed by centrifuging and dried at 90°C in fluidized bed dryers.
The bulk density of the end product can vary between 800 and 1200 g/I
according to the production process. In general, the percarbonate is stabilized by an additional coating. Coating processes and materials are widely described in the patent literature. Basically, any commercially available percarbonate types as marketed, for example, by Solvay Interox, Degussa, Kemira and Akzo may be used in accordance with the present invention.
In the case of the percarbamide - as with all the bleaching agents used - the content of this substance in the tablets is determined by the application envisaged for the tablets. Whereas conventional heavy-duty detergents in tablet form contain between 5 and 30% by weight, preferably between 7.5 and 25% by weight and more preferably between 12.5 and 22.5% by weight of percarbamide, bleach or bleach booster tablets contain between 15 and 50% by weight, preferably between 22.5 and 45% by weight and more preferably between 30 and 40% by weight of percarbamide.
In addition to the percarbamide and the additional bleaching agents optionally used, the detergent tablets according to the invention may contain bleach activators) which represents a preferred embodiment of the present invention. Bleach activators are incorporated in detergents in order to obtain an improved bleaching effect at washing temperatures of 60°C
or lower. According to the invention, compounds which form aliphatic peroxocarboxylic acids preferably containing 1 to 10 carbon atoms and more preferably 2 to 4 carbon atoms and/or optionally substituted perbenzoic acid under perhydrolysis conditions may be used as bleach activators. Suitable bleach activators are substances which contain O-and/or N-acyl groups with the number of carbon atoms indicated and/or optionally substituted benzoyl groups. Preferred additional bleach activators are polyacylated alkylenediamines, more especially tetraacetyl ethylenediamine (TAED), acylated triazine derivatives, more particularly 1,5-diacetyl-2,4-dioxohexahydro-1,3,5-triazine (DADHT), acylated glycol urils, more particularly tetraacetyl glycol uril (TAGU), N-acylimides, more particularly N-nonanoyl succinimide (NOSI), acylated phenol sulfonates, more particularly n-nonanoyl- or isononanoyl-oxybenzenesulfonate (n- or iso-NOBS), carboxylic anhydrides, more especially phthalic anhydride, acylated polyhydric alcohols, more especially triacetin, ethylene glycol diacetate and 2,5-diacetoxy-2,5-dihydrofuran.
In addition to or instead of the conventional bleach activators, so called bleach catalysts may also be incorporated in the tablets. Bleach catalysts are bleach-boosting transition metal salts or transition metal complexes such as, for example, Mn-, Fe-, Co-, Ru- or Mo-salen complexes or carbonyl complexes. Mn-, Fe-, Co-, Ru-, Mo-, Ti-, V- and Cu complexes with N-containing tripod ligands and Co-, Fe-, Cu- and Ru ammine complexes may also be used as bleach catalysts.
If the tablets according to the invention contain bleach activators, they contain between 0.5 and 30% by weight, preferably between 1 and 20% by weight and more preferably between 2 and 15% by weight - based on the tablet as a whole - of one or more bleach activators or bleach catalysts. These quantities may vary according to the application envisaged for the tablets. Thus, in typical heavy-duty detergent tablets, bleach activator contents of 0.5 to 10% by weight, preferably 2 to 8% by weight and more preferably 4 to 6% by weight are normal whereas bleach tablets can have much higher contents, for example between 5 and 30% by weight, preferably between 7.5 and 25% by weight and more preferably between 10 and 20% by weight. The expert is not restricted in his freedom of formulation and is able in this way to produce laundry detergent tablets, dishwasher tablets or bleach tablets with a stronger or weaker bleaching effect by varying the contents of bleach activator and bleaching agent.
A particularly preferred bleach activator is N,N,N',N'-tetraacetyl ethylenediamine which is widely used in laundry/dishwasher detergents.
Accordingly, preferred detergent tablets are characterized in that they contain tetraacetyl ethylenediamine in the quantities mentioned above as bleach activator.
Besides the ingredients mentioned above, the detergent tablets according to the invention may contain other ingredients in quantities determined by the particular application envisaged for the tablets. Thus, substances from the groups of surfactants, builders and polymers are particularly suitable for use in the detergent tablets according to the invention. The expert will again have no difficulty in selecting the individual components and the quantities in which to use them. Thus, a heavy-duty detergent tablet will contain relatively large quantities of surfactants) whereas a bleach tablet may well contain no surfactant at all. The quantity of builders) used also varies according to the particular application envisaged.
The detergent tablets according to the invention may contain any of the builders normally used in detergents, i.e. in particular zeolites, silicates, carbonates, organic co-builders and - providing there are no ecological objections to their use - also phosphates.
Suitable crystalline layered sodium silicates correspond to the general formula NaMSiX02x+~A y H20, where M is sodium or hydrogen, x is a number of 1.9 to 4 and y is a number of 0 to 20, preferred values for x being 2, 3 or 4. Crystalline layered silicates such as these are described, for example, in European patent application EP-A-0 164 514. Preferred crystalline layered silicates corresponding to the above formula are those in which M is sodium and x assumes the value 2 or 3. Both Vii- and 8-sodium disilicates Na2Si205A y H20 are particularly preferred, ~3-sodium disilicate being obtainable, for example, by the process described in International patent application WO-A- 91/08171.
Other useful builders are amorphous sodium silicates with a modulus (NaZO:Si02 ratio) of 1:2 to 1:3.3, preferably 1:2 to 1:2.8 and more preferably 1:2 to 1:2.6 which dissolve with delay and exhibit multiple wash cycle properties. The delay in dissolution in relation to conventional amorphous sodium silicates can have been obtained in various ways, for 5 example by surface treatment, compounding, compacting or by overdrying.
In the context of the invention, the term "amorphous" is also understood to encompass "X-ray amorphous". In other words, the silicates do not produce any of the sharp X-ray reflexes typical of crystalline substances in X-ray diffraction experiments, but at best one or more maxima of the 10 scattered X-radiation which have a width of several degrees of the diffraction angle. However, particularly good builder properties may even be achieved where the silicate particles produce crooked or even sharp diffraction maxima in electron diffraction experiments. This may be interpreted to mean that the products have microcrystalline regions 15 between 10 and a few hundred nm in size, values of up to at most 50 nm and, more particularly, up to at most 20 nm being preferred. So-called X-ray amorphous silicates such as these, which also dissolve with delay in relation to conventional waterglasses, are described for example in German patent application DE-A-44 00 024. Compacted amorphous silicates, compounded amorphous silicates and overdried X-ray-amorphous silicates are particularly preferred.
The finely crystalline, synthetic zeolite containing bound water used in accordance with the invention is preferably zeolite A and/or zeolite P.
Zeolite MAP~ (Crosfield) is a particularly preferred P-type zeolite.
However, zeolite X and mixtures of A, X and/or P are also suitable.
According to the invention, it is also preferred to use, for example, a co-crystallizate of zeolite X and zeolite A (ca. 80% by weight zeolite X) which is marketed by CONDEA Augusta S.p.A. under the name of VEGOBOND
AX~ and which may be described by the following formula:

nNa20 ~ (1-n)K20 ~ A12O3 ~ (2 - 2.5)Si02 ~ (3.5 - 5.5) H20.
The zeolite may be used both as a builder in a granular compound and as a kind of "powder" to be applied to the entire mixture to be tabletted, both routes normally being used to incorporate the zeolite in the premix.
Suitable zeolites have a mean particle size of less than 10 ~m (volume distribution, as measured by the Coulter Counter Method) and contain preferably 18 to 22% by weight and more preferably 20 to 22% by weight of bound water.
The generally known phosphates may of course also be used as builders providing their use should not be avoided on ecological grounds.
Among the large number of commercially available phosphates, alkali metal phosphates have the greatest importance in the detergent industry, pentasodium triphosphate and pentapotassium triphosphate (sodium and potassium tripolyphosphate) being particularly preferred.
"Alkali metal phosphates" is the collective term for the alkali metal (more particularly sodium and potassium) salts of the various phosphoric acids, including metaphosphoric acids (HP03)~ and orthophosphoric acid (H3P04) and representatives of higher molecular weight. The phosphates combine several advantages: they act as alkalinity sources, prevent lime deposits on machine parts and lime incrustations in fabrics and, in addition, contribute towards the cleaning effect.
Sodium dihydrogen phosphate (NaH2P04) exists as the dihydrate (density 1.91 gcm3, melting point 60°) and as the monohydrate (density 2.04 gcm3). Both salts are white readily water-soluble powders which, on heating, lose the water of crystallization and, at 200°, are converted into the weakly acidic diphosphate (disodium hydrogen diphosphate, Na2HZP20~) and, at higher temperatures, into sodium trimetaphosphate (Na3P309) and Maddrell's salt (see below). NaH2P04 shows an acidic reaction. It is formed by adjusting phosphoric acid with sodium hydroxide to a pH value of 4.5 and spraying the resulting "mash". Potassium dihydrogen phosphate (primary or monobasic potassium phosphate, potassium biphosphate, KDP), KH2P04, is a white salt with a density of 2.33 gcm', has a melting point of 253° [decomposition with formation of potassium polyphosphate (KP03)X) and is readily soluble in water.
Disodium hydrogen phosphate (secondary sodium phosphate), Na2HP04, is a colorless, readily water-soluble crystalline salt. It exists in water-free form and with 2 moles (density 2.066 gcm3, water loss at 95°), 7 moles (density 1.68 gcm3, melting point 48° with loss of 5 H20) and 12 moles of water (density 1.52 gcm3, melting point 35° with loss of 5 H20), becomes water-free at 100° and, on fairly intensive heating, is converted into the diphosphate Na4P20~. Disodium hydrogen phosphate is prepared by neutralization of phosphoric acid with soda solution using phenol-phthalein as indicator. Dipotassium hydrogen phosphate (secondary or dibasic potassium phosphate), K2HP04, is an amorphous white salt which is readily soluble in water.
Trisodium phosphate, tertiary sodium phosphate, Na3P04, consists of colorless crystals which have a density of 1.62 gcm3 and a melting point of 73-76° (decomposition) as the dodecahydrate, a melting point of 100° as the decahydrate (corresponding to 19-20% P205) and a density of 2.536 gcm3 in water-free form (corresponding to 39-40% P2O5). Trisodium phosphate is readily soluble in water through an alkaline reaction and is prepared by concentrating a solution of exactly 1 mole of disodium phosphate and 1 mole of NaOH by evaporation. Tripotassium phosphate (tertiary or tribasic potassium phosphate), K3P04, is a white deliquescent granular powder with a density of 2.56 gcm3, has a melting of 1340° and is readily soluble in water through an alkaline reaction. It is formed, for example, when Thomas slag is heated with coal and potassium sulfate.
Despite their higher price, the more readily soluble and therefore highly effective potassium phosphates are often preferred to corresponding ' CA 02306381 2000-04-20 sodium compounds in the detergent industry.
Tetrasodium diphosphate (sodium pyrophosphate), Na4P20~, exists in water-free form (density 2.534 gcm3, melting point 988°, a figure of 880°
has also been mentioned) and as the decahydrate (density 1.815 - 1.836 gcm3, melting point 94° with loss of water). Both substances are colorless crystals which dissolve in water through an alkaline reaction. Na4P20~ is formed when disodium phosphate is heated to >200° or by reacting phosphoric acid with soda in a stoichiometric ratio and spray-drying the solution. The decahydrate complexes heavy metal salts and hardness salts and, hence, reduces the hardness of water. Potassium dinhosnhatP
(potassium pyrophosphate), K4P20~, exists in the form of the trihydrate and is a colorless hygroscopic powder with a density of 2.33 gcm3 which is soluble in water, the pH value of a 1 % solution at 25° being 10.4.
Relatively high molecular weight sodium and potassium phosphates are formed by condensation of NaH2P04 or KH2P04. They may be divided into cyclic types, namely the sodium and potassium metaphosphates, and chain types, the sodium and potassium polyphosphates. The chain types in particular are known by various different names: fused or calcined phosphates, Graham's salt, Kurrol's salt and Maddrell's salt. All higher sodium and potassium phosphates are known collectively as condensed phosphates.
The industrially important pentasodium triphosphate, Na5P30~o (sodium tripolyphosphate), is a non-hygroscopic white water-soluble salt which crystallizes without water or with 6 H20 and which has the general formula Na0-[P(O)(ONa)-O]~-Na where n = 3. Around 17 g of the salt free from water of crystallization dissolve in 100 g of water at room temperature, around 20 g at 60° and around 32 g at 100°. After heating of the solution for 2 hours to 100°, around 8% orthophosphate and 15% diphosphate are formed by hydrolysis. In the preparation of pentasodium triphosphate, phosphoric acid is reacted with soda solution or sodium hydroxide in a stoichiometric ratio and the solution is spray-dried. Similarly to Graham's salt and sodium diphosphate, pentasodium triphosphate dissolves many insoluble metal compounds (including lime soaps, etc.). Pentapotassium triphosphate, K5P30~o (potassium tripolyphosphate), is marketed for example in the form of a 50% by weight solution (> 23% P205, 25% K20).
The potassium polyphosphates are widely used in the detergent industry.
Sodium potassium tripolyphosphates, which may also be used in accordance with the invention, also exist. They are formed for example when sodium trimetaphosphate is hydrolyzed with KOH:
(NaP03)3 + 2 KOH ~ Na3K2P30~o + H20 According to the invention, they may be used in exactly the same way as sodium tripolyphosphate, potassium tripolyphosphate or mixtures thereof. Mixtures of sodium tripolyphosphate and sodium potassium tripolyphosphate or mixtures of potassium tripolyphosphate and sodium potassium tripolyphosphate or mixtures of sodium tripolyphosphate and potassium tripolyphosphate and sodium potassium tripolyphosphate may also be used in accordance with the invention.
Organic cobuilders suitable for use in the detergent tablets according to the invention are, in particular, polycarboxylates/polycarboxylic acids, polymeric polycarboxylates, aspartic acid, polyacetals, dextrins, other organic cobuilders (see below) and phosphonates. These classes of substances are described in the following.
Useful organic builders are, for example, the polycarboxylic acids usable, for example, in the form of their sodium salts, polycarboxylic acids in this context being understood to be carboxylic acids which bear more than one acid function. Examples of such carboxylic acids are citric acid, adipic acid, succinic acid, glutaric acid, malic acid, tartaric acid, malefic acid, fumaric acid, sugar acids, aminocarboxylic acids, nitrilotriacetic acid (NTA), providing their use is not ecologically unsafe, and mixtures thereof.
Preferred salts are the salts of the polycarboxylic acids, such as citric acid, adipic acid, succinic acid, glutaric acid, tartaric acid, sugar acids and mixtures thereof.
5 The acids per se may also be used. Besides their builder effect, the acids also typically have the property of an acidifying component and, hence, also serve to establish a relatively low and mild pH value in detergents. Citric acid, succinic acid, glutaric acid, adipic acid, gluconic acid and mixtures thereof are particularly mentioned in this regard.
10 Other suitable builders are polymeric polycarboxylates such as, for example, the alkali metal salts of polyacrylic or polymethacrylic acid, for example those with a relative molecular weight of 500 to 70,000 g/mole.
The molecular weights mentioned in this specification for polymeric polycarboxylates are weight-average molecular weights MW of the particular 15 acid form which, basically, were determined by gel permeation chromatography (GPC) using a UV detector. The measurement was carried out against an external polyacrylic acid standard which provides realistic molecular weight values by virtue of its structural similarity to the polymers investigated. These values differ distinctly from the molecular 20 weights measured against polystyrene sulfonic acids as standard. The molecular weights measured against polystyrene sulfonic acids are generally higher than the molecular weights mentioned in this specification.
Particularly suitable polymers are polyacrylates which preferably have a molecular weight of 2,000 to 20,000 g/mole. By virtue of their superior solubility, preferred representatives of this group are the short chain polyacrylates which have molecular weights of 2,000 to 10,000 g/mole and, more particularly, 3,000 to 5,000 g/mole.
Also suitable are copolymeric polycarboxylates, particularly those of acrylic acid with methacrylic acid and those of acrylic acid or methacrylic acid with malefic acid. Acrylic acid/maleic acid copolymers containing 50 to 90% by weight of acrylic acid and 50 to 10% by weight of malefic acid have proved to be particularly suitable. Their relative molecular weights, based on the free acids, are generally in the range from 2,000 to 70,000 g/mole, preferably in the range from 20,000 to 50,000 g/mole and more preferably in the range from 30,000 to 40,000 g/mole.
The (co)polymeric polycarboxylates may be used either in powder form or in the form of an aqueous solution. The content of (co)polymeric polycarboxylates in the detergent is preferably from 0.5 to 20% by weight and more preferably from 3 to 10% by weight.
In order to improve solubility in water, the polymers may also contain allyl sulfonic acids, such as allyloxybenzene sulfonic acid and methallyl sulfonic acid, as monomer.
Other particularly preferred polymers are biodegradable polymers of more than two different monomer units, for example those which contain salts of acrylic acid and malefic acid and vinyl alcohol or vinyl alcohol derivatives as monomers or those which contain salts of acrylic acid and 2-alkylallyl sulfonic acid and sugar derivatives as monomers.
Other preferred copolymers are those which are described in German patent applications DE-A-43 03 320 and DE-A-44 17 734 and which preferably contain acrolein and acrylic acid/acrylic acid salts or acrolein and vinyl acetate as monomers.
Other preferred builders are polymeric aminodicarboxylic acids, salts or precursors thereof. Particular preference is attributed to polyaspartic acids or salts and derivatives thereof which, according to German patent application DE-A-195 40 086, are also said to have a bleach-stabilizing effect in addition to their co-builder properties.
Other suitable builders are polyacetals which may be obtained by reaction of dialdehydes with polyol carboxylic acids containing 5 to 7 carbon atoms and at least three hydroxyl groups. Preferred polyacetals are obtained from dialdehydes, such as glyoxal, glutaraldehyde, terephthal-aldehyde and mixtures thereof and from polyol carboxylic acids, such as gluconic acid and/or glucoheptonic acid.
Other suitable organic builders are dextrins, for example oligomers or polymers of carbohydrates which may be obtained by partial hydrolysis of starches. The hydrolysis may be carried out by standard methods, for example acid- or enzyme-catalyzed methods. The end products are preferably hydrolysis products with average molecular weights of 400 to 500,000 g/mol. A polysaccharide with a dextrose equivalent (DE) of 0.5 to 40 and, more particularly, 2 to 30 is preferred, the DE being an accepted measure of the reducing effect of a polysaccharide by comparison with dextrose which has a DE of 100. Both maltodextrins with a DE of 3 to 20 and dry glucose sirups with a DE of 20 to 37 and also so-called yellow dextrins and white dextrins with relatively high molecular weights of 2,000 to 30,000 g/mole may be used.
The oxidized derivatives of such dextrins are their reaction products with oxidizing agents which are capable of oxidizing at least one alcohol function of the saccharide ring to the carboxylic acid function. Dextrins thus oxidized and processes for their production are known, for example, from European patent applications EP-A-0 232 202, EP-A-0 427 349, EP-A-0 472 042 and EP-A-0 542 496 and from International patent applications WO 92118542, WO 93/08251, WO 93/16110, WO 94128030, WO 95107303, WO 95112619 and WO 95/20608. An oxidized oliaosaccharide corresponding to German patent application DE-A-196 00 018 is also suitable. A product oxidized at C6 of the saccharide ring can be particularly advantageous.
Other suitable co-builders are oxydisuccinates and other derivatives of disuccinates, preferably ethylenediamine disuccinate. Ethylenediamine-N,N'-disuccinate (EDDS) is preferably used in the form of its sodium or magnesium salts. Glycerol disuccinates and glycerol trisuccinates are also preferred in this connection. The quantities used in zeolite-containing and/or silicate-containing formulations are from 3 to 15% by weight.
Other useful organic co-builders are, for example, acetylated hydroxycarboxylic acids and salts thereof which may optionally be present in lactone form and which contain at least 4 carbon atoms, at least one hydroxy group and at most two acid groups. Co-builders such as these are described, for example, in International patent application WO-A-95/20029.
Another class of substances with co-builder properties are the phosphonates, more particularly hydroxyalkane and aminoalkane phos phonates. Among the hydroxyalkane phosphonates, 1-hydroxyethane-1,1 diphosphonate (HEDP) is particularly important as a co-builder. It is preferably used in the form of the sodium salt, the disodium salt showing a neutral reaction and the tetrasodium salt an alkaline reaction (pH 9).
Preferred aminoalkane phosphonates are ethylenediamine tetramethylene phosphonate (EDTMP), diethylenetriamine pentamethylenephosphonate (DTPMP) and higher homologs thereof. They are preferably used in the form of the neutrally reacting sodium salts, for example as the hexasodium salt of EDTMP or as the hepta- and octasodium salts of DTPMP. Of the phosphonates, HEDP is preferably used as a builder. In addition, the aminoalkane phosphonates have a pronounced heavy metal binding capacity. Accordingly, it can be of advantage, particularly where the detergents also contain bleach, to use aminoalkane phosphonates, more particularly DTPMP, or mixtures of the phosphonates mentioned.
In addition, any compounds capable of forming complexes with alkaline earth metal ions may be used as co-builders.
The quantity of builder used is normally between 10 and 70% by weight, preferably between 15 and 60% by weight and more preferably between 20 and 50% by weight. The quantity of builder used is again dependent upon the particular application envisaged, so that bleach tablets can contain larger quantities of builders (for example between 20 and 70%
by weight, preferably between 25 and 65% by weight and more preferably between 30 and 55% by weight) than, for example, laundry detergent tablets (normally 10 to 50% by weight, preferably 12.5 to 45% by weight and more preferably 17.5 to 37.5% by weight).
Preferred detergent tablets additionally contain one or more surfactant(s). Anionic, nonionic, cationic and/or amphoteric surfactants or mixtures thereof may be used in the detergent tablets according to the invention. Mixtures of anionic and nonionic surfactants are preferred from the performance point of view. The total surfactant content of the tablets is from 5 to 60% by weight, based on the weight of the tablet, surfactant contents above 15% by weight being preferred.
The anionic surfactants used are, for example, those of the sulfonate and sulfate type. Preferred surfactants of the sulfonate type are C9_~3 alkyl benzenesulfonates, olefin sulfonates, i.e. mixtures of alkene and hydroxy-alkane sulfonates, and the disulfonates obtained, for example, from C~2_~8 monoolefins with an internal or terminal double bond by sulfonation with gaseous sulfur trioxide and subsequent alkaline or acidic hydrolysis of the sulfonation products. Other suitable surfactants of the sulfonate type are the alkane sulfonates obtained from C~2_~8 alkanes by sulfochlorination or sulfoxidation and subsequent hydrolysis or neutralization. The esters of a-sulfofatty acids (ester sulfonates), for example the a-sulfonated methyl esters of hydrogenated coconut oil, palm kernel oil or tallow fatty acids.
Other suitable anionic surfactants are sulfonated fatty acid glycerol esters, i.e. the monoesters, diesters and triesters and mixtures thereof which are obtained where production is carried out by esterification by a monoglycerol with 1 to 3 moles of fatty acid or in the transesterification of triglycerides with 0.3 to 2 moles of glycerol. Preferred sulfonated fatty acid glycerol esters are the sulfonation products of satturated C6_22 fatty acids, for example caproic acid, caprylic acid, capric acid, myristic acid, lauric acid, palmitic acid, stearic acid or behenic acid.
Preferred alk(en)yl sulfates are the alkali metal salts and, in particular, the sodium salts of the sulfuric acid semiesters of C~Z_~8 fatty alcohols, for example coconut alcohol, tallow alcohol, lauryl, myristyl, cetyl or stearyl alcohol, or C~o_2o oxoalcohols and the corresponding semiesters of secondary alcohols with the same chain length. Other preferred 5 alk(en)yl sulfates are those with the chain length mentioned which contain a synthetic, linear alkyl chain based on a petrochemical and which are similar in their degradation behavior to the corresponding compounds based on oleochemical raw materials. C~2_~6 alkyl sulfates and C~2_~5 alkyl sulfates and also C~4_~5 alkyl sulfates alkyl sulfates are particularly preferred 10 from the washing performance point of view. Other suitable anionic surfactants are 2,3-alkyl sulfates which may be produced, for example, in accordance with US 3,234,258 or US 5,075,041 and which are commercially obtainable as products of the Shell Oil Company under the name of DAN~.
15 The sulfuric acid monoesters of linear or branched C~_2~ alcohols ethoxylated with 1 to 6 moles of ethylene oxide, such as 2-methyl-branched C9_» alcohols containing on average 3.5 moles of ethylene oxide (EO) or C~2_~g fatty alcohols containing 1 to 4 EO, are also suitable. In view of their high foaming capacity, they are normally used in only relatively small 20 quantities, for example in quantities of 1 to 5% by weight, in dishwashing detergents.
Other suitable anionic surfactants are the salts of alkyl sulfosuccinic acid which are also known as sulfosuccinates or as sulfosuccinic acid esters and which represent monoesters and/or diesters of sulfosuccinic 25 acid with alcohols, preferably fatty alcohols and, more particularly, ethoxylated fatty alcohols. Preferred sulfosuccinates contain C$_,$ fatty alcohol molecules or mixtures thereof. Particularly preferred sulfosuccinates contain a fatty alcohol molecule derived from ethoxylated fatty alcohols which, considered in isolation, represent nonionic surfactants (for a description, see below). Of these sulfosuccinates, those of which the ~

fatty alcohol molecules are derived from narrow-range ethoxylated fatty alcohols are particularly preferred. Alk(en)yl succinic acid preferably containing 8 to 18 carbon atoms in the alk(en)yl chain or salts thereof may also be used.
Other suitable anionic surfactants are, in particular, soaps. Suitable soaps are, in particular, saturated fatty acid soaps, such as the salts of lauric acid, myristic acid, palmitic acid, stearic acid, hydrogenated erucic acid and behenic acid, and soap mixtures derived in particular from natural fatty acids, for example coconut, palm kernel or tallow acids.
The anionic surfactants, including the soaps, may be present in the form of their sodium, potassium or ammonium salts and as soluble salts of organic bases, such as mono-, di- or triethanolamine. The anionic surfactants are preferably present in the form of their sodium or potassium salts and, more preferably, in the form of their sodium salts.
Preferred nonionic surfactants are alkoxylated, advantageously ethoxylated, more especially primary alcohols preferably containing 8 to 18 carbon atoms and, on average, 1 to 12 moles of ethylene oxide (EO) per mole of alcohol, in which the alcohol radical may be linear or, preferably, methyl-branched in the 2-position or may contain linear and methyl-branched radicals in the form of the mixtures typically present in oxoalcohol radicals. However, alcohol ethoxylates containing linear radicals of alcohols of native origin with 12 to 18 carbon atoms, for example coconut oil, palm oil, tallow or oleyl alcohol, and on average 2 to 8 EO per mole of alcohol are particularly preferred. Preferred ethoxylated alcohols include, for example, C~2_~a alcohols containing 3 EO or 4 EO, C9_» alcohol containing 7 EO, C~3_~5 alcohols containing 3 EO, 5 EO, 7 EO or 8 EO, C~2_~8 alcohols containing 3 EO, 5 EO or 7 EO and mixtures thereof, such as mixtures of C~2_~4 alcohol containing 3 EO and C~z_~8 alcohol containing 5 EO. The degrees of ethoxylation mentioned represent statistical mean values which, for a special product, can be a whole number or a broken ~

number. Preferred alcohol ethoxylates have a narrow homolog distribution (narrow range ethoxylates, NRE). In addition to these nonionic surfactants, fatty alcohols containing more than 12 EO may also be used, examples including tallow fatty alcohol containing 14 EO, 25 EO, 30 EO or 40 EO.
Suitable other nonionic surfactants are alkyl glycosides with the general formula RO(G)X where R is a primary, linear or methyl-branched, more particularly 2-methyl-branched, aliphatic radical containing 8 to 22 and preferably 12 to 18 carbon atoms and G stands for a glycose unit containing 5 or 6 carbon atoms, preferably glucose. The degree of oligomerization x, which indicates the distribution of monoglycosides and oligoglycosides, is a number of 1 to 10 and preferably 1.2 to 1.4.
Another class of preferred nonionic surfactants which may be used either as sole nonionic surfactant or in combination with other nonionic surfactants are alkoxylated, preferably ethoxylated or ethoxylated and propoxylated, fatty acid alkyl esters preferably containing 1 to 4 carbon atoms in the alkyl chain, more especially the fatty acid methyl esters which are described, for example, in Japanese patent application JP 581217598 or which are preferably produced by the process described in International patent application WO-A-90!13533.
Nonionic surfactants of the amine oxide type, for example N-coconutalkyl-N,N-dimethylamine oxide and N-tallowalkyl-N,N-dihydroxy-ethylamine oxide, and the fatty acid alkanolamide type are also suitable.
The quantity in which these nonionic surfactants are used is preferably no more than the quantity in which the ethoxylated fatty alcohols are used and, more preferably, no more than half that quantity.
Other suitable surfactants are polyhydroxyfatty acid amides corresponding to formula (II):
R' R-CO-N-[Z] (I I) in which RCO is an aliphatic acyl group containing 6 to 22 carbon atoms, R' is hydrogen, an alkyl or hydroxyalkyl group containing 1 to 4 carbon atoms and [Z] is a linear or branched polyhydroxyalkyl group containing 3 to 10 carbon atoms and 3 to 10 hydroxyl groups. The polyhydroxyfatty acid amides are known substances which may normally be obtained by reductive amination of a reducing sugar with ammonia, an alkylamine or an alkanolamine and subsequent acylation with a fatty acid, a fatty acid alkyl ester or a fatty acid chloride.
The group of polyhydroxyfatty acid amides also includes compounds corresponding to formula (III):
R'-O-R2 R-CO-N-[Z] (I I I) in which R is a linear or branched alkyl or alkenyl group containing 7 to 12 carbon atoms, R' is a linear, branched or cyclic alkyl group or an aryl group containing 2 to 8 carbon atoms and R2 is a linear, branched or cyclic alkyl group or an aryl group or an oxyalkyl group containing 1 to 8 carbon atoms, C» alkyl or phenyl groups being preferred, and [Z] is a linear polyhydroxy-alkyl group, of which the alkyl chain is substituted by at least two hydroxyl groups, or alkoxylated, preferably ethoxylated or propoxylated, derivatives of that group.
[Z] is preferably obtained by reductive amination of a reduced sugar, for example glucose, fructose, maltose, lactose, galactose, mannose or xylose. The N-alkoxy- or N-aryloxy-substituted compounds may then be converted into the required polyhydroxyfatty acid amides by reaction with fatty acid methyl esters in the presence of an alkoxide as catalyst, for example in accordance with the teaching of International patent application WO-A-95/07331.
According to the invention, preferred detergent tablets contain anionic and nonionic surfactant(s). Performance-related advantages can ' CA 02306381 2000-04-20 arise out of certain quantity ratios in which the individual classes of surfactants are used.
For example, particularly preferred detergent tablets are charac terized in that the ratio of anionic surfactants) to nonionic surfactants) is from 10:1 to 1:10, preferably from 7.5:1 to 1:5 and more preferably from 5:1 to 1:2. Other preferred detergent tablets contain surfactant(s), preferably anionic and/or nonionic surfactant(s), in quantities of 5 to 40% by weight, preferably 7.5 to 35% by weight, more preferably 10 to 30% by weight and most preferably 12.5 to 25% by weight, based on the weight of the tablets.
It can be of advantage from the performance point of view if certain classes of surfactants are missing from certain phases of the detergent tablets or from the entire tablet, i.e. from every phase. In another important embodiment of the present invention, therefore, at least one phase of the tablets is free from nonionic surfactants.
Conversely, a positive effect can also be obtained through the presence of certain surfactants in individual phases or in the tablet as a whole, i.e. in every phase. Introducing the alkyl polyglycosides described above has proved to be of particular advantage, so that detergent tablets in which at least one phase of the tablet contains alkyl polyglycosides are preferred.
As with the nonionic surfactants, the omission of anionic surfactants from individual phases or from all phases can result in detergent tablets which are more suitable for certain applications. Accordingly, detergent tablets where at least one phase of the tablet is free from anionic surfactants are also possible in accordance with the present invention.
Besides the ingredients mentioned (bleaching agent, bleach activator, builder, surfactant and disintegration aid), the detergent tablets according to the invention may contain other ingredients typical of detergents from the dyes, perfumes, optical brighteners, enzymes foam inhibitors, silicone oils, redeposition inhibitors, discoloration inhibitors, dye transfer inhibitors and corrosion inhibitors.
In order to improve their aesthetic impression, the detergents according to the invention may be colored with suitable dyes. Preferred dyes, which are not difficult for the expert to choose, have high stability in 5 storage, are not affected by the other ingredients of the detergents or by light and do not have any pronounced substantivity for textile fibers so as not to color them.
Any dyes which can be destroyed by oxidation in the washing process and mixtures thereof with suitable blue dyes, so-called blueing 10 agents, are preferably used in the detergent tablets according to the invention. It has proved to be of advantage to use dyes which are soluble in water or - at room temperature - in liquid organic substances. Suitable dyes are, for example, anionic dyes, for example anionic nitroso dyes. One possible dye is, for example, naphthol green (Color Index (CI) Part 1: Acid 15 Green 1; Part 2: 10020), which is commercially available for example as Basacid~ Grun 970 from BASF, Ludwigshafen, and mixtures thereof with suitable blue dyes. Other suitable dyes are Pigmosol~ Blau 6900 (CI
74160), Pigmosol~ Grun 8730 (CI 74260), Basonyl~ Rot 545 FL (CI
45170), Sandolan~ Rhodamin EB 400 (CI 45100), Basacid~ Gelb 094 (CI
20 47005), Sicovit~ Patentblau 85 E 131 (CI 42051), Acid Blue 183 (CAS
12217-22-0, CI Acid Blue 183), Pigment Blue 15 (CI 74160), Supranol~
Blau GLW (CAS 12219-32-8, CI Acid Blue 221)), Nylosan~ Gelb N-7GL
SGR (CAS 61814-57-1, CI Acid Yellow 218) and/or Sandolan~ Blau (CI
Acid Blue 182, CAS 12219-26-0).
25 In selecting the dye, it is important to ensure that the dye does not have an excessive affinity for the textile surfaces and, in particular, for synthetic fibers. Another factor to be taken into account in the selection of suitable dyes is that dyes differ in their stability to oxidation. Generally speaking, water-insoluble dyes are more stable to oxidation than water-30 soluble dyes. The concentration of the dye in the detergents varies according to its solubility and hence its sensitivity to oxidation. In the case of readily water-soluble dyes, for example the above-mentioned Basacid~
Grun and Sandolan~ Blau, dye concentrations in the range from a few 102 to 103 % by weight are typically selected. By contrast, in the case of the pigment dyes which are particularly preferred for their brilliance, but which are less readily soluble in water, for example the above-mentioned Pigmosol~ dyes, suitable concentrations of the dye in detergents are typically of the order of a few 103 to 104 % by weight.
The tablets may contain derivatives of diaminostilbenedisulfonic acid or alkali metal salts thereof as optical brighteners. Suitable optical brighteners are, for example, salts of 4,4'-bis-(2-anilino-4-morpholino-1,3,5-triazinyl-6-amino)-stilbene-2,2'-disulfonic acid or compounds of similar composition which contain a diethanolamino group, a methylamino group, an anilino group or a 2-methoxyethylamino group instead of the morpholino group. Brighteners of the substituted diphenyl styryl type, for example alkali metal salts of 4,4'-bis-(2-sulfostyryl)-diphenyl, 4,4'-bis-(4-chloro-3-sulfostyryl)-diphenyl or 4-(4-chlorostyryl)-4.'-(2-sulfostyryl)-diphenyl, may also be present. Mixtures of the brighteners mentioned above may also be used. The optical brighteners are used in the detergent tablets according to the invention in concentrations of 0.01 to 1 % by weight, preferably 0.05 to 0.5% by weight and more preferably 0.1 to 0.25% by weight, based on the tablet as a whole.
Perfumes are added to the detergent tablets according to the invention to improve the aesthetic impression created by the products and to provide the consumer not only with the required washing performance but also with a visually and sensorially "typical and unmistakable" product.
Suitable perfume oils or perfumes include individual perfume compounds, for example synthetic products of the ester, ether, aldehyde, ketone, alcohol and hydrocarbon type. Perfume compounds of the ester type are, for example, benzyl acetate, phenoxyethyl isobutyrate, p-tert.butyl ~

cyclohexyl acetate, linalyl acetate, dimethyl benzyl carbinyl acetate, phenyl ethyl acetate, linalyl benzoate, benzyl formate, ethyl methyl phenyl glycinate, allyl cyclohexyl propionate, styrallyl propionate and benzyl salicylate. The ethers include, for example, benzyl ethyl ether; the aldehydes include, for example, the linear alkanals containing 8 to 18 carbon atoms, citral, citronellal, citronellyloxyacetaldehyde, cyclamen aldehyde, hydroxycitronellal, lilial and bourgeonal; the ketones include, for example, the ionones, a-isomethyl ionone and methyl cedryl ketone; the alcohols include anethol, citronellol, eugenol, geraniol, linalool, phenyl ethyl alcohol and terpineol and the hydrocarbons include, above all, the terpenes, such as limonene and pinene. However, mixtures of various perfumes which together produce an attractive perfume note are preferably used. Perfume oils such as these may also contain natural perfume mixtures obtainable from vegetable sources, for example pine, citrus, jasmine, patchouli, rose or ylang-ylang oil. Also suitable are clary oil, camomile oil, clove oil, melissa oil, mint oil, cinnamon leaf oil, lime blossom oil, juniper berry oil, vetiver oil, olibanum oil, galbanum oil and labdanum oil and orange blossom oil, neroli oil, orange peel oil and sandalwood oil.
The detergent tablets according to the invention normally contain up to 2% by weight of perfumes, based on the formulation as a whole. The perfumes may be directly incorporated in the detergents according to the invention, although it can also be of advantage to apply the perfumes to supports which strengthen the adherence of the perfume to the washing and which provide the textiles with a long-lasting fragrance through a slower release of the perfume. Suitable support materials are, for example, cyclodextrins, the cyclodextrin/perfume complexes optionally being coated with other auxiliaries.
Suitable enzymes are, in particular, those from the classes of hydrolases, such as proteases, esterases, lipases or lipolytic enzymes, amylases, cellulases or other glycosyl hydrolases and mixtures thereof. All these hydrolases contribute to the removal of stains, such as protein-containing, fat-containing or starch-containing stains, and discoloration in the washing process. Cellulases and other glycosyl hydrolases can contribute towards color retention and towards increasing fabric softness by removing pilling and microfibrils. Oxidoreductases may also be used for bleaching and for inhibiting dye transfer. Enzymes obtained from bacterial strains or fungi, such as Bacillus subtilis, Bacillus licheniformis, Streptomyces griseus, Coprinus cinereus and Humicola insolens and from genetically modified variants are particularly suitable. Proteases of the subtilisin type are preferably used, proteases obtained from Bacillus lentus being particularly preferred. Of particular interest in this regard are enzyme mixtures, for example of protease and amylase or protease and lipase or lipolytic enzymes or protease and cellulase or of cellulase and lipase or lipolytic enzymes or of protease, amylase and lipase or lipolytic enzymes or protease, lipase or lipolytic enzymes and cellulase, but especially protease-and/or lipase-containing mixtures or mixtures with lipolytic enzymes.
Examples of such lipolytic enzymes are the known cutinases. Peroxidases or oxidases have also been successfully used in some cases. Suitable amylases include in particular a-amylases, isoamylases, pullanases and pectinases. Preferred cellulases are cellobiohydrolases, endoglucanases and ~3-glucosidases, which are also known as cellobiases, and mixtures thereof. Since the various cellulase types differ in their CMCase and avicelase activities, the desired activities can be established by mixing the cellulases in the appropriate ratios.
The enzymes may be adsorbed to supports and/or encapsulated in membrane materials to protect them against premature decomposition.
The percentage content of the enzymes, enzyme mixtures or enzyme granules may be, for example, from about 0.1 to 5% by weight and is preferably from 0.5 to about 4.5% by weight.
In addition, the detergent tablets according to the invention may also ~

contain components with a positive effect on the removability of oil and fats from textiles by washing (so-called soil repellents). This effect becomes particularly clear when a textile which has already been repeatedly washed with a detergent according to the invention containing this oil- and fat-s dissolving component is soiled. Preferred oil- and fat-dissolving compo-nents include, for example, nonionic cellulose ethers, such as methyl cellulose and methyl hydroxypropyl cellulose containing 15 to 30% by weight of methoxyl groups and 1 to 15% by weight of hydroxypropoxyl groups, based on the nonionic cellulose ether, and the polymers of phthalic acid and/or terephthalic acid known from the prior art or derivatives thereof, more particularly polymers of ethylene terephthalates and/or polyethylene glycol terephthalates or anionically and/or nonionically modified derivatives thereof. Of these, the sulfonated derivatives of phthalic acid and terephthalic acid polymers are particularly preferred.
The present invention also relates to a process for the production of detergent tablets by tabletting a particulate premix, characterized in that the premix contains percarbamide in quantities of 1 to 40% by weight, based on the premix.
Similarly to the foregoing observations on the detergent tablets according to the invention, preferred variants of the process according to the invention are also characterized in that the premix contains percarbamide in quantities of 5 to 30% by weight, preferably in quantities of 7.5 to 25% by weight and more preferably in quantities of 10 to 20% by weight, based on the weight of the premix.
The foregoing observations also apply in regard to the particle size distribution of the percarbamide introduced into the process according to the invention. Likewise, the use of other ingredients is also applicable to the process according to the invention. In preferred processes, the particulate premix additionally contains surfactant-containing granules and has a bulk density of at least 500 g/I, preferably of at least 600 g/I and more preferably of at least 700 g/I.
So far as the preferred particle size of the percarbamide is concerned, reference is made to the foregoing observations. In preferred processes according to the invention, the surfactant-containing granules 5 have particle sizes of 100 to 2000 Nm, preferably in the range from 200 to 1800 Nm, more preferably in the range from 400 to 1600 Nm and most preferably in the range from 600 to 1400 Nm.
The other ingredients of the detergent tablets according to the invention may also be introduced into the process according to the 10 invention, cf. the foregoing observations. Preferred processes are characterized in that the particulate premix additionally contains one or more substances from the group of bleach activators, disintegration aids, enzymes, pH regulators, perfumes, perfume carriers, fluorescers, dyes, foam inhibitors, silicone oils, redeposition inhibitors, optical brighteners, 15 discoloration inhibitors, dye transfer inhibitors and corrosion inhibitors.
The tablets according to the invention are produced by first dry-mixing the ingredients - which may be completely or partly pregranulated -and then shaping/forming, morre particularly tabletting, the resulting mixture using conventional processes. To produce the tablets according to 20 the invention, the premix is compacted between two punches in a die to form a solid compactate. This process, which is referred to in short hereinafter as tabletting, comprises four phases, namely metering, compacting (elastic deformation), plastic deformation and ejection.
The premix is first introduced into the die, the filling level and hence 25 the weight and shape of the tablet formed being determined by the position of the lower punch and the shape of the die. Uniform dosing, even at high tablet throughputs, is preferably achieved by volumetric dosing of the premix. As the tabletting process continues, the top punch comes into contact with the premix and continues descending towards the bottom 30 punch. During this compaction phase, the particles of the premix are pressed closer together, the void volume in the filling between the punches continuously diminishing. The plastic deformation phase in which the particles coalesce and form the tablet begins from a certain position of the top punch (and hence from a certain pressure on the premix). Depending on the physical properties of the premix, its constituent particles are also partly crushed, the premix sintering at even higher pressures. As the tabletting rate increases, i.e. at high throughputs, the elastic deformation phase becomes increasingly shorter so that the tablets formed can have more or less large voids. In the final step of the tabletting process, the tablet is forced from the die by the bottom punch and carried away by following conveyors. At this stage, only the weight of the tablet is definitively established because the tablets can still change shape and size as a result of physical processes (re-elongation, crystallographic effects, cooling, etc.).
The tabletting process is carried out in commercially available tablet presses which, in principle, may be equipped with single or double punches. In the latter case, not only is the top punch used to build up pressure, the bottom punch also moves towards the top punch during the tabletting process while the top punch presses downwards. For small production volumes, it is preferred to use eccentric tablet presses in which the punches) is/are fixed to an eccentric disc which, in turn, is mounted on a shaft rotating at a certain speed. The movement of these punches is comparable with the operation of a conventional four-stroke engine.
Tabletting can be carried out with a top punch and a bottom punch, although several punches can also be fixed to a single eccentric disc, in which case the number of die bores is correspondingly increased. The throughputs of eccentric presses vary according to type from a few hundred to at most 3,000 tablets per hour.
For larger throughputs, rotary tablet presses are generally used. In rotary tablet presses, a relatively large number of dies is arranged in a circle on a so-called die table. The number of dies varies - according to model - between 6 and 55, although even larger dies are commercially available. Top and bottom punches are associated with each die on the die table, the tabletting pressures again being actively built up not only by the top punch or bottom punch, but also by both punches. The die table and the punches move about a common vertical axis, the punches being brought into the filling, compaction, plastic deformation and ejection positions by means of curved guide rails. At those places where the punches have to be raised or lowered to a particularly significant extent (filling, compaction, ejection), these curved guide rails are supported by additional push-down members, pull-down rails and ejection paths. The die is filled from a rigidly arranged feed unit, the so-called filling shoe, which is connected to a storage container for the premix. The pressure applied to the premix can be individually adjusted through the tools for the top and bottom punches, pressure being built up by the rolling of the punch shank heads past adjustable pressure rollers.
To increase throughput, rotary presses can also be equipped with two filling shoes so that only half a circle has to be negotiated to produce a tablet. To produce two-layer or multiple-layer tablets, several filling shoes are arranged one behind the other without the lightly compacted first layer being ejected before further filling. Given suitable process control, shell and bull's-eye tablets - which have a structure resembling an onion skin -can also be produced in this way. In the case of bull's-eye tablets, the upper surface of the core or rather the core layers is not covered and thus remains visible. Rotary tablet presses can also be equipped with single or multiple punches so that, for example, an outer circle with 50 bores and an inner circle with 35 bores can be simultaneously used for tabletting.
Modern rotary tablet presses have throughputs of more than one million tablets per hour.
Where rotary presses are used for tabletting, it has proved to be of ' CA 02306381 2000-04-20 advantage to carry out the tabletting process with minimal variations in the weight of the tablets. Variations in tablet hardness can also be reduced in this way. Minimal variations in weight can be achieved as follows:
- using plastic inserts with minimal thickness tolerances - low rotor speed - large filling shoe - adapting the rotational speed of the filling shoe blade to the rotor speed - filling shoe with constant powder height - decoupling the filling shoe from the powder supply Any of the nonstick coatings known in the art may be used to reduce caking on the punch. Plastic coatings, plastic inserts or plastic punches are particularly advantageous. Rotating punches have also proved to be of advantage; if possible, the upper and lower punches should be designed for rotation. If rotating punches are used, there will generally be no need for a plastic insert. In that case, the surfaces of the punch should be electropolished.
It has also been found that long tabletting times are advantageous.
These can be achieved by using pressure rails, several pressure rollers or low rotor speeds. Since variations in tablet hardness are caused by variations in the pressures applied, systems which limit the tabletting pressure should be used. Elastic punches, pneumatic compensators or spring elements in the force path may be used. The pressure roller can also be spring-mounted.
Tabletting machines suitable for the purposes of the invention can be obtained, for example, from the following companies: Apparatebau Holzwarth GbR, Asperg; Wilhelm Fette GmbH, Schwarzenbek; Hofer GmbH, Weil; Horn & Noack Pharmatechnik GmbH, Worms; IMA
Verpackungssysteme GmbH Viersen; KILIAN, Cologne; KOMAGE, Kell am See, KORSCH Pressen GmbH, Berlin; and Romaco GmbH, Worms. Other suppliers are, for example Dr. Herbert Pete, Vienna (AU); Mapag Maschinenbau AG, Bern (Switzerland); BWI Manesty, Liverpool (GB); I.
Holand Ltd., Nottingham (GB); and Courtoy N.V., Halle (BE/LU) and Medicopharm, Kamnik (SI). One example of a particularly suitable tabletting machine is the model HPF 630 hydraulic double-pressure press manufactured by LAEIS, D. Tabletting tools are obtainable, for example, from Adams Tablettierwerkzeuge Dresden; Wilhelm Fett GmbH, Schwarzenbek; Klaus Hammer, Solingen; Herber & Sohne GmbH, Hamburg; Hofer GmbH, Weil; Horn & Noack, Pharmatechnik GmbH, Worms; Ritter Pharmatechnik GmbH, Hamburg; Romaco GmbH, Worms and Notter Werkzeugbau, Tamm. Other suppliers are, for example, Senss AG, Reinach (CH) and Medicopharm, Kamnik (SI).
The tablets can be made in certain shapes and certain sizes.
Suitable shapes are virtually any easy-to-handle shapes, for example slabs, bars, cubes, squares and corresponding shapes with flat sides and, in particular, cylindrical forms of circular or oval cross-section. This last embodiment encompasses shapes from tablets to compact cylinders with a height-to-diameter ratio of more than 1.
The portioned pressings may be formed as separate individual elements which correspond to a predetermined dose of the detergent.
However, it is also possible to form pressings which combine several such units in a single pressing, smaller portioned units being easy to break off in particular through the provision of predetermined weak spots. For the use of laundry detergents in machines of the standard European type with horizontally arranged mechanics, it can be of advantage to produce the portioned pressings as cylindrical or square tablets, preferably with a diameter-to-height ratio of about 0.5:2 to 2:0.5. Commercially available hydraulic presses, eccentric presses and rotary presses are particularly suitable for the production of pressings such as these.
The three-dimensional form of another embodiment of the tablets according to the invention is adapted in its dimensions to the dispensing compartment of commercially available domestic washing machines, so that the tablets can be introduced directly, i.e. without a dosing aid, into the dispensing compartment where they dissolve on contact with water.
However, it is of course readily possible - and preferred in accordance with 5 the present invention - to use the detergent tablets in conjunction with a dosing aid.
Another preferred tablet which can be produced has a plate-like or slab-like structure with alternately thick long segments and thin short segments, so that individual segments can be broken off from this "bar" at 10 the predetermined weak spots, which the short thin segments represent, and introduced into the machine. This "bar" principle can also be embodied in other geometric forms, for example vertical triangles which are only joined to one another at one of their longitudinal sides.
In another possible embodiment, however, the various components 15 are not compressed to form a single tablet, instead the tablets obtained comprise several layers, i.e. at least two layers. These various layers may have different dissolving rates. This can provide the tablets with favorable performance properties. If, for example, the tablets contain components which adversely affect one another, one component may be integrated in 20 the more quickly dissolving layer while the other component may be incorporated in a more slowly dissolving layer so that the first component can already have reacted off by the time the second component dissolves.
The various layers of the tablets can be arranged in the form of a stack, in which case the inner layers) dissolve at the edges of the tablet before the 25 outer layers have completely dissolved. Alternatively, however, the inner layers) may also be completely surrounded by the layers lying further to the outside which prevents constituents of the inner layers) from dissolving prematurely.
In another preferred embodiment of the invention, a tablet consists 30 of at least three layers, i.e. two outer layers and at least one inner layer, a peroxy bleaching agent being present in at least one of the inner layers whereas, in the case of the stack-like tablet, the two cover layers and, in the case of the envelope-like tablet, the outermost layers are free from peroxy bleaching agent. In another possible embodiment, peroxy bleaching agent and any bleach activators or bleach catalysts present and/or enzymes may be spatially separated from one another in one and the same tablet. Multilayer tablets such as these have the advantage that they can be used not only via a dispensing compartment or via a dosing unit which is added to the wash liquor, instead it is also possible in cases such as these to introduce the tablet into the machine in direct contact with the fabrics without any danger of spotting by bleaching agent or the like.
Similar effects can also be obtained by coating individual constituents of the detergent composition to be compressed or the tablet as a whole. To this end, the tablets to be coated may be sprayed, for example, with aqueous solutions or emulsions or a coating may be obtained by the process known as melt coating.
After pressing, the detergent tablets have high stability. The fracture resistance of cylindrical tablets can be determined via the diametral fracture stress. This in turn can be determined in accordance with the following equation:

a=
aDt where ~ represents the diametral fracture stress (DFS) in Pa, P is the force in N which leads to the pressure applied to the tablet that results in fracture thereof, D is the diameter of the tablet in meters and t is its height.
The present invention also relates to the use of carbamides for improving the hardness and disintegration time of detergent tablets. This use of percarbamide in accordance with the invention leads to tablets with advantageous properties, as the following Examples show. The foregoing ' CA 02306381 2000-04-20 observations on the process according to the invention apply equally to preferred embodiments of the use according to the invention (particle sizes, other ingredients, composition of the premix, etc.).
Embodiments of the Invention are described in the following specific examples which are not be construed as limiting Examples To produce percarbamide-containing detergent tablets, surfactant granules were mixed with other additive components and the resulting mixture tabletted in an eccentric tablet press. The composition of the surfactant granules is shown in Table 1 below while the composition of the premix to be tabletted (and hence the composition of the tablets) is set out in Table 2.
Table 1:
Surfactant granules [% by weight) C9_~3 alkyl benzenesulfonate 18.4 C~2_~8 fatty alcohol sulfate 4.9 C~2_~$ fatty alcohol + 7E0 4.9 Soap 1.6 Sodium carbonate 18.8 Sodium silicate 5.5 Zeolite A (water-free active 31.3 substance) Optical brightener 0.3 Na hydroxyethane-1,1-diphosphonate0.8 Acrylic acid/maleic acid copolymer5.5 Water, salts Balance Table 2:
Premix [% by weight]
Surfactant granules 62.95 Bleaching agent* 17.00 Tetraacetyl ethylenediamine7.30 Foam inhibitor 3.50 Enzymes 1.70 Repel-O-Tex~ SRP 4** 1.10 Perfume 0.45 Zeolite A 1.00 Cellulose 5.00 * Tablet E according to the invention E:
carbamide peroxide of Peroxid-Chemie, Pullach Comparison Example C:
sodium perborate monohydrate of Degussa AG
** Terephthalic acid/ethylene glycol/polyethylene glycol ester (Rhodia, Rhone-Poulenc) The tablettable premixes E and V were tabletted in a Korsch eccentric press (tablet diameter 45 mm, tablet height 22 mm, tablet weight 37.5 g). The tabletting pressure was adjusted so that three series of tablets (E, E', E" and V, V', V") differing in their hardness were obtained in either case.
The hardness of the tablets was measured by deforming a tablet until it broke, the force being applied to the sides of the tablet and the maximum force withstood by the tablet being determined.
To determine tablet disintegration, a tablet was placed in a glass ~

beaker filled with water (600 ml water, temperature 30°C) and the time taken for the tablet to disintegrate completely was measured. The experi-mental data of the individual tablet series are shown in Table 3:
Table 3:
Detergent tablets [physical data]
Tablet E E' E" V V' V"

Tablet hardness [N] 37 48 58 38 50 60 Tablet disintegration13 16 33 32 > 60 > 60 [s]

Claims (38)

1. Detergent tablets of compacted particulate detergent containing percarbamide.

2. Detergent tablets as claimed in claim 1, containing percarbamide in quantities of 1 to 40% by weight based on the weight of the tablets.

3. Detergent tablets as claimed in claim 2, containing percarbamide in quantities of 5 to 30% by weight.

4. Detergent tablets as claimed in claim 3, containing percarbamide in quantities of 7.5 to 25% by weight.

5. Detergent tablets as claimed in claim 4, containing percarbamide in quantities of 10 to 20% by weight.

6. Detergent tablets as claimed in any of claims 1 to 5, wherein the percarbamide has a mean particle size above 0.3 mm.

7. Detergent tablets as claimed in claim 6, wherein the percarbamide is substantially free from particles below 0.2 mm in size.

8. Detergent tablets as claimed in any of claims 1 to 7, wherein the percarbamide contains less than 30% by weight of particles below 0.4 mm. in size.

9. Detergent tablets as claimed in claim 8, wherein the percarbamide contains less than 20% by weight of particles below 0.4 mm. in size.

10. Detergent tablets as claimed in claim 9, wherein the percarbamide contains less than 10% by weight of particles below 0.4 mm. in size.

11. Detergent tablets as claimed in claim 8, wherein the percarbamide contains more than 10% by weight of particles larger than 0.8 mm in size.

12. Detergent tablets as claimed in claim 11, wherein the percarbamide contains more than 20% by weight of particles larger than 0.8 mm in size.

13. Detergent tablets as claimed in claim 12, wherein the percarbamide contains more than 30% by weight of particles larger than 0.8 mm in size.

14. Detergent tablets as claimed in claim 11, wherein the percarbamide is substantially free of particles larger than 1.6 mm in size.

15. Detergent tablets as claimed in any of claims 1 to 14, containing percarbamide-containing compounds which contain at least 60% by weight of percarbamide, based on the weight of the compound.

16. Detergent tablets as claimed in any of claims 1 to 15, which are free from oligomeric oligocarboxylic acids.

17. Detergent tablets as claimed in claim 16, which are free from citric acid.

18. Detergent tablets as claimed in any of claims 1 to 17, additionally containing a disintegration aid in quantities of 0.5 to 10% by weight based on the weight of the tablets.

19. Detergent tablets as claimed in claim 18, wherein said disintegration aid is present in quantities of 3 to 7% by weight.

20. Detergent tablets as claimed in claim 19, wherein said disintegration aid is present in quantities of 4 to 6% by weight.

21. Detergent tablets as claimed in any of claims 18 to 20, wherein the disintegration aid is cellulose-based.

22. Detergent tablets as claimed in claim 21, wherein the disintegration aid is in granular, co-granulated or compacted form.

23. Detergent tablets as claimed in any of claims 1 to 22, containing anionic or nonionic surfactant(s) in quantities of 5 to 40% by weight based on the weight of the tablets.

24. Detergent tablets as claimed in claim 23, containing surfactant(s) in quantities of 7.5 to 35% by weight.

25. Detergent tablets as claimed in claim 24, containing surfactant(s) in quantities of 10 to 30% by weight.

26. Detergent tablets as claimed in claim 23, containing surfactant(s) in quantities of 12.5 to 25% by weight.

27. A process for the production of detergent tablets by tabletting a particulate premix, wherein the premix contains percarbamide in quantities of 1 to 40% by weight, based on the premix.

28. A process as claimed in claim 27, wherein the premix contains percarbamide in quantities of 7.5 to 25% by weight.

29. A process as claimed in claim 28, wherein the premix contains percarbamide in quantities of 10 to 20% by weight.

30. A process as claimed in any of claims 27 to 29, wherein the particulate premix additionally contains surfactant-containing granules and has a bulk density of least 500 g/l.

31. A process as claimed in claim 30, wherein the premix has a bulk density of at least 600 g/l.

32. A process as claimed in claim 31, wherein the premix has a bulk density of at least 700 g/l.

33. A process as claimed in claim 30, wherein the surfactant-containing granules have particle sizes in the range of 100 to 2000 µm.

34. A process as claimed in claim 33, wherein the surfactant-containing granules have particle sizes in the range of 200 to 1800 µm.

35. A process as claimed in claim 34, wherein the surfactant-containing granules have particle sizes in the range of 400 to 1600 µm.

36. A process as claimed in claim 35, wherein the surfactant-containing granules have particle sizes in the range of 600 to 1400 µm.

37. A process as claimed in any of claims 27 to 36, wherein the particulate premix additionally contains one or more substances from the group of bleaching agents, bleach activators, disintegration aids, enzymes, pH regulators, perfumes, perfume carriers, fluorescers, dyes, foam inhibitors, silicone oils, redeposition inhibitors, optical brighteners, discoloration inhibitors, dye transfer inhibitors and corrosion inhibitors.

38. The use of percarbamide for increasing the hardness and reducing the disintegration time of detergent tablets.