CA2297458A1

CA2297458A1 - Abrasion-resistant detergent tablets with a high nonionic surfactant content

Info

Publication number: CA2297458A1
Application number: CA 2297458
Authority: CA
Inventors: Monika Boecker; Heinke Jebens; Hans-Friedrich Kruse; Andreas Lietzmann; Markus Semrau
Original assignee: Henkel AG and Co KGaA
Current assignee: Individual
Priority date: 1999-01-28
Filing date: 2000-01-28
Publication date: 2000-07-28
Also published as: AU2665000A; WO2000044871A1; DE19903289A1

Abstract

Detergent tablets which combine high hardness values and good dissolving behavior with high resistance to abrasion can be obtained if the ratio between the nonionic and anionic surfactants present in the tablets is in the range from 0.4:1 to 3:1.

Description

ABRASION-RESISTANT DETERGENT TABLETS WITH A HIGH
NONIONIC SURFACTANT CONTENT
FIELD OF THE INVENTION
This invention relates generally to compact shaped bodies having detersive properties. Detersive shaped bodies include, for example, laundry detergent tablets, tablets for dishwashing machines or for cleaning hard surfaces, bleach tablets for use in washing or dishwashing machines, water softening tablets or stain remover tablets. More particularly, the present invention relates to laundry detergent tablets which are used for washing laundry in domestic washing machines and which are referred to in short as detergent tablets.
BACKGROUND OF THE INVENTION
Detergent tablets are widely described in the prior-art literature and are enjoying increasing popularity 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. As a result, detergent shaped bodies are also comprehensively described in the patent literature. One problem which repeatedly arises in the use of detergent tablets is the inadequate disintegrating and dissolving rate of the tablets under in-use conditions.
Since sufficiently stable, i.e. dimensionally stable and fracture-resistant, tablets can only be produced by applying relatively high pressures, the ingredients of the tablet are heavily compacted so that disintegration of the tablet in the wash liquor is delayed which results in excessively slow release of the active substances in the washing process. The delayed disintegration of the tablets has the further disadvantage that typical detergent tablets cannot be flushed into the washing process from the dispensing compartment of domestic washing machines because the tablets do not disintegrate sufficiently quickly into secondary particles which are small enough to be flushed from the dispensing compartment into the drum of the washing machine. Another problem which occurs with detergent tablets in particular lies in the friability of the tablets and their often inadequate resistance to abrasion. Thus, although sufficiently fracture-resistant, i.e. hard, detergent tablets can be produced, they are often not strong enough to withstand the loads encountered during packaging, transportation and handling, i.e. impact and friction effects, so that broken edges and signs of abrasion spoil the appearance of the tablet or even lead to the complete destruction of its structure.
So far as the prior art is concerned, solutions to the problem of the friability or abrasion resistance of detergent tablets are disclosed solely in earlier German patent application DE 198 41 146.6 (Henkel KGaA). The solution proposed in this document is to incorporate liquid, non-surfactant binders in the premixes to be tabletted.
The use of surfactants in detergent tablets is the subject of numerous publications. Formulations rich in nonionic surfactants are described in particular in the following documents.
European patent application EP 355 626 (Henkel KGaA) discloses a process for the production of phosphate-free or low-phosphate detergent tablets in which at least two powder-form or granular components (A) and (B) are prepared, mixed and tabletted. Component (A) contains the total quantity of anionic surfactants while component (B) contains 75 to 100% of the total quantity of nonionic surfactants.
European patent application EP 466 485 (Unilever) also describes detergent tablets which contain builders and anionic and nonionic surfactants. The premix to be tabletted consists of particles, of which 20 to 100% consist of anionic surfactant, and of particles which are preferably free from anionic surfactants and which may contain nonionic surfactant.
There is no reference in this document to any particular ratio to be maintained between the nonionic and anionic surfactants. The problem of inadequate abrasion resistance is not mentioned either.
Detergent tablets which contain potassium carbonate as a compulsory component besides large quantities of nonionic surfactant are described in European patent application EP 482 627 (Kao Corp.).
According to the teaching of this patent specification, the solubility of the tablets is improved by a special ratio by weight between nonionic surfactant and potassium carbonate. This is also no mention in this document of anionic surfactant/nonionic surfactant ratios, nor any discussion of the problem of abrasion resistance.
The use of ethoxylated alcohols with an average C chain length below 12 (because at least 25% of the alkyl chains have a length of less than 12 carbon atoms) is disclosed in EP 598 586 (Unilever). Detergent tablets containing anionic surfactant in addition to nonionic surfactant are not explicitly described in this document. There is no mention of a particular ratio to be maintained between nonionic and anionic surfactants, nor any reference to the problem of abrasion.
Now, the problem addressed by the present invention was to provide tablets which, for predetermined hardness, would be distinguished by short disintegration times which and, accordingly, could even be flushed into the washing process from the dispensing compartment of commercially available washing machines. In addition to meeting these requirements, the tablets would have increased resistance to impact and friction, i.e. would show improved, i.e. reduced, friability and would exhibit reduced abrasion behavior. As far as possible, the advantageous properties would be achieved through the making-up of detergent ingredients in order to be able to dispense with the addition of auxiliaries that are "foreign" to the formulation, i.e. do not develop a detersive effect.
From this point of view, suitable active ingredients were, above all, the washing-active or detersive substances.
BRIEF DESCRIPTION OF THE INVENTION
It has now been found that the ratio by weight of nonionic to anionic surfactants in the formulation as a whole has a critical influence on friability.
The present invention relates to detergent tablets of compacted particulate detergent containing builders, anionic and nonionic surfactants and optionally other detergent ingredients in which the ratio of nonionic to anionic surfactants is in the range from 0.4:1 to 3:1.
In one aspect of the present invention provides a detergent tablet comprising compacted detergent granules containing builders, anionic and nonionic surfactants and optionally other detergent ingredients, wherein the ratio of nonionic to anionic surfactants in the tablet is in the range from 0.4:1 to 3:1.
In another aspect, the invention provides a process for the production of detergent tablets which comprises: mixing surfactant-containing granules with fine-particle after treatment components to form a mixture and subsequently forming/shaping the mixture to form a tablet the ratio of nonionic to anionic surfactants in the tablet is in the range from 0.4:1 to 3:1.
In yet another aspect, there is provided a method for improving the abrasion resistance of detergent tablets which comprises compressing a mixture comprising granules containing nonionic and anionic surfactants with a ratio of nonionic surfactants to anionic surfactants of from 0.4:1 to 3:1 and fine particle aftertreatment components.
In the context of the present invention, the term "ratio" characterizes the quotient of the percentages by weight of nonionic and anionic surfactants, the percentages by weight being based on the tablet as a whole. It does not matter whether the anionic and nonionic surfactants have been introduced into the detergent tablets in various ways or whether they are present in various phases or regions of the tablet. In preferred embodiments, the ratio is in an even narrower range so that detergent tablets in which the ratio of nonionic to anionic surfactants is in the range from 0.45:1 to 2.5:1, preferably in the range from 0.5:1 to 2:1 and more preferably in the range from 0.75:1 to 1.5:1 are preferred.
The detergent tablets according to the invention contain builders and anionic and nonionic surfactants as compulsory ingredients. These ingredients are described in the following.
DETAILED DESCRIPTION OF THE INVENTION
Suitable anionic surfactants are, for example, those of the sulfonate and sulfate type. Suitable surfactants of the sulfonate type are preferably C9_~3 alkyl benzenesulfonates, olefin sulfonates, i.e. mixtures of alkene and hydroxyalkane sulfonates, and the disulfonates obtained, for example, from C~2_~$ 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, for example 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, are also suitable.
Other suitable anionic surfactants are sulfonated fatty acid glycerol esters. Fatty acid glycerol esters in the context of the present invention are the monoesters, diesters and triesters and mixtures thereof which are obtained where production is carried out by esterification of 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 saturated fatty acids containing 6 to 22 carbon atoms, 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~2_~8 fatty alcohols, for example cocofatty alcohol, tallow fatty 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 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_~s alkyl sulfates, C~2_~5 alkyl sulfates and C~4_~5 alkyl sulfates are preferred from the point of view of washing technology. 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~.
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_~8 fatty alcohols containing 1 to 4 EO, are also suitable. In view of their high foaming capacity, they are only used in relatively small 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 acid with alcohols, preferably fatty alcohols and, more particularly, ethoxylated fatty alcohols. Preferred sulfosuccinates contain C8_~$ fatty alcohol residues or mixtures thereof. Particularly preferred sulfosuccinates contain a fatty alcohol residue 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 residues 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 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 oil, palm kernel oil or tallow fatty 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.
According to the invention, preferred detergents tablets are those which contain more than 5% by weight, preferably more than 7.5% by weight and more preferably more than 10% by weight of anionic surfactants, based on the weight of the tablet.
So far as the choice of anionic surfactants is concerned, there are no basic requirements to restrict the freedom of formulation. However, preferred surfactant granules do have a soap content in excess of 0.2% by weight, based on the total weight of the detergent tablet. Preferred anionic surfactants are alkyl benzenesulfonates and fatty alcohol sulfates, preferred detergent tablets containing 2 to 20% by weight, preferably 2.5 to 15% by weight and more preferably 5 to 10% by weight of fatty alcohol sulfate(s), based on the weight of the detergent composition.
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 component may be linear or, preferably, methyl-branched in the 2-position or may contain linear and methyl-branched residues in the form of the mixtures typically present in oxoalcohol residues. However, alcohol ethoxylates containing linear residues of alcohols of native origin with 12 to 18 carbon atoms, for example coconut oil, palm oil, tallow fatty 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_~$ alcohols containing 3 EO, 5 EO or 7 EO and mixtures thereof, such as mixtures of C~Z_~4 alcohol containing 3 EO and C~2_~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.
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-90113533.
Another class of nonionic surfactants which may advantageously be used are the alkyl polyglycosides (APGs). Suitable alkyl polyglycosides correspond to the general formula RO(G)Z where R is a linear or branched, more particularly 2-methyl-branched, saturated or unsaturated 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 glycosidation z is between 1.0 and 4.0, preferably between 1.0 and 2.0 and more preferably between 1.1 and 1.4.
Linear alkyl polyglucosides, i.e. alkyl polyglycosides in which the polyglycosyl component is a glucose unit and the alkyl component is an n-alkyl group, are preferably used.
The surfactant granules may advantageously contain alkyl polyglycosides, APG contents of more than 0.2% by weight, based on the tablet as a whole, being preferred. Particularly preferred detergent tablets contain APGs in quantities of 0.2 to 10% by weight, preferably in quantities of 0.2 to 5% by weight and more preferably in quantities of 0.5 to 3% by weight.
Nonionic surfactants of the amine oxide type, for example N-cocoalkyl-N,N-dimethylamine oxide and N-tallowalkyl-N,N-dihydroxyethyl-amine 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 (I):
R' R-CO-N-Z (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 (II):
R'-O-R2 R-CO-N-Z (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 polyhydroxyalkyl 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-95107331.
According to the invention, preferred detergent tablets contain more than 2% by weight, preferably more than 5% by weight and more preferably more than 7.5% by weight of nonionic surfactants, based on the weight of the tablet.
According to the invention, nonionic surfactants from all of the groups mentioned above may be used. Irrespective of the chemical nature of the nonionic surfactants used, the nonionic surfactants present in the detergent tablets preferably have a melting point below 40°C, preferably below 30°C and more preferably below 20°C.
As mentioned above, the nonionic and anionic surfactants can be incorporated in the detergent tablets according to the invention in various ways. The may be added to the premix to be tabletted, for example, in solid form or may be sprayed onto the premix in liquid form. It has been found to be of advantage to produce surfactant granules which are mixed with other powder-form components to form the premix to be tabletted.
According to the invention, preferred detergent tablets contain the surfactants in the form of surfactant-containing granules which are present in the tablets in quantities of 40 to 95% by weight, preferably 45 to 85% by weight and more preferably 55 to 75% by weight, based on tablet weight.
In order to incorporate the required amount of detersive substance in the detergent tablets, preferred detergent tablets contain surfactant granules with surfactant contents of 5 to 60% by weight, preferably 10 to 50% by weight and more preferably 15 to 40% by weight, based on the weight of the surfactant granules. According to the invention, detergent tablets containing surfactant granules with anionic surfactant contents of 5 to 45% by weight, preferably 10 to 40% by weight and more preferably 15 to 35% by weight, based on the weight of the surfactant granules, and surfactant granules with nonionic surfactant contents of 1 to 30% by weight, preferably 5 to 25% by weight and more preferably 7.5 to 20% by weight, based on the weight of the surfactant granules, are particularly preferred.
In order to obtain storage-stable free-flowing granules, carriers which contain the surfactant granules, i.e. builders, are preferably added in the production of the surfactant granules. Other detergent ingredients, more particularly so-called minor components, such as optical brighteners, polymers, defoamers, phosphonates, dyes and perfumes, may also form part of the surfactant granules. The substances are described in the following.

Besides the detersive ingredients, builders are the most important ingredients of detergents. Any of the builders normally used in detergents may be present in the detergent tablets according to the invention, including in particular zeolites, silicates, carbonates, organic co-builders and also - providing there are no ecological objections to their use -phosphates.
It has been found that the effect of improving abrasion resistance is greater if the surfactant granules contain only small quantities of carbonates. Accordingly, preferred detergent tablets have a potassium carbonate content of less than 10% by weight, preferably less than 7.5%
by weight and more preferably less than 5% by weight, based on the weight of the tablet, tablets free from potassium carbonate being particularly preferred.
Crystalline layer-form sodium silicates suitable as builders correspond to the general formula NaMSixOZX+~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 layer silicates such as these are described, for example, in European patent application EP-A-0 164 514. Preferred crystalline layer silicates corresponding to the above formula are those in which M is sodium and x assumes the value 2 or 3.
Both ~3- and 8-sodium disilicates Na2Si205A y H20 are particularly preferred, ~-sodium disilicate being obtainable, for example, by the process described in International patent application WO-A- 91108171.
Other useful builders are amorphous sodium silicates with a modulus (Na20: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 be obtained in various ways, for example by surface treatment, compounding, compacting or by overdrying. In the context of the invention, the term Aamorphous- is also understood to encompass AX-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 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 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.
If desired, more zeolite besides the quantity of zeolite P and/or X
introduced through the surfactant granules may be incorporated in the premix by adding zeolite as an aftertreatment component. The finely crystalline, synthetic zeolite containing bound water used in accordance with the invention is preferably a zeolite of the A, P, X or Y type. However, zeolite X and mixtures of A, X and/or P are also suitable. 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.
The sodium salts of the orthophosphates, the pyrophosphates and, in particular, the tripolyphosphates are particularly suitable.
Preferred detergent tablets contain less than 5% by weight, preferably less than 2% by weight and more preferably less than 1 % by weight of silica(s), based on the weight of the tablet.
Organic cobuilders which may be used in the detergent tablets according to the invention include, in particular, polycarboxy-lates/polycarboxylic acids, polymeric polycarboxylates, aspartic acid, polyacetals, dextrins, other organic cobuilders (see below) and phosphonates. Substances belonging to these classes 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 carrying more than one acid function). Examples include citric acid, adipic acid, succinic acid, glutaric acid, malic acid, tartaric acid, malefic acid, fumaric acid, sugar acids, aminocarboxylic acids, nitrilotriacetic acid (NTA), providing its 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.
The acids per se may also be used. Besides their builder effect, the acids typically have the property of an acidifying component and, accordingly, are also used to establish a lower and more mild pH value in laundry or dishwashing detergents. Citric acid, succinic acid, glutaric acid, adipic acid, gluconic acid and mixtures thereof are particularly mentioned in this regard.
Other suitable builders are polymeric polycarboxylates such as, for example, the alkali metal salts of polyacrylic acid or polymethacrylic acid, for example those having 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 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 weights measured against polystyrene sulfonic acids as standard. The molecular weights measured against polystyrene sulfonic acids are generally far higher than the molecular weights mentioned in this specification.
Suitable polymers are, in particular, 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 compositions is preferably between 0.5 and 20%
by weight and more preferably between 3 and 10% by weight.
In order to improve their solubility in water, the polymers may also contain allyl sulfonic acids, for example allyloxybenzenesulfonic acid and methallyl sulfonic acid as monomer.
Biodegradable polymers of more than two different monomer units are also particularly preferred, examples including 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 described in German patent applications DE-A-43 03 320 and DE-A-44 17 734 which preferably contain acrolein and acrylic acid/acrylic acid salts or acrolein and vinyl acetate as monomers.
Other preferred builders are polymeric aminodicarboxilic acids, salts or precursors thereof. Polyaspartic acids or salts and derivatives thereof which, according to German patent application DE-A-195 40 086, have a bleach-stabilizing effect in addition to their co-builder properties are particularly preferred.
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, terephthalaldehyde 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/mole. 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 syrups 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 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 93108251, WO 93116110, WO 95107303, WO 95112619 and WO 95120608. An oxidized oligosaccharide according 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 particularly 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 a sodium salt, the disodium salt showing a neutral reaction and the tetrasodium salt an alkaline ration (pH 9).
Preferred aminoalkane phosphonates are ethylenediamine tetramethylene phosphonate (EDTMP), diethylenetriamine pentamethylene phosphonate (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 and as the hepta- and octasodium salt of DTPMP. Within the class of phosphonates, HEDP is preferably used as builder. The aminoalkane phosphonates also show a pronounced heavy metal binding capacity. Accordingly, it can be of advantage, particularly where the detergents also contain bleaching agents, to use aminoalkane phosphonates, more especially 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 production of surfactant-containing granules is widely described in the prior art literature, including many patents and numerous synoptic articles and books. Thus, W. Hermann de Groot, I. Adami and G.F. Moretti describe various spray drying, mixing and granulation processes for the production of detergents in "The Manufacture of Modern Detergent Powders", Hermann de Groot Academic Publisher, Wassenaar, 1995.

On energy grounds, the surfactant-containing granules are preferably produced by a granulation process and not by spray drying according to the invention. Besides conventional granulation and agglomeration processes, which may be carried out in various mixer-granulators and mixer-agglomerators, press agglomeration processes, for example, may also be used. Accordingly, processes in which the surfactant-containing granules are produced by granulation, agglomeration, press agglomeration or a combination of these processes are preferred.
The granulation process may be carried out in a number of machines typically used in the detergent industry. For example, the spheronizers widely used in the pharmaceutical industry may be employed. In rotary machines such as these, the residence time of the granules is normally less than 20 seconds. Conventional mixers and mixer-granulators are also suitable for granulation. The mixers used may be both high-shear mixers and also normal mixers with lower rotational speeds. Suitable mixers are, for example, Series R or RV Eirich~ mixers (trademarks of Maschinenfabrik Gustav Eirich, Hardheim), the Schugi~
Flexomix mixer, the Fukae~ FS-G mixers (trademarks of Fukae Powtech, Kogyo Co., Japan), Lodige~ FM, KM and CB mixers (trademarks of Lodige Maschinenbau GmbH, Paderborn) and Series T or K-T Drais~
mixers (trademarks of Drais-Werke GmbH, Mannheim). The residence times of the granules in the mixers is less than 60 seconds, the residence time also depending on the rotational speed of the mixer. The residence times are shorter, the higher the rotational speed of the mixer. The residence times of the granules in the mixer/spheronizer are preferably under one minute and more preferably under 15 seconds. In low-speed mixers, for example a Lodige KM, residence times of up to 20 minutes are adjusted, residence times of under 10 minutes being preferred in the interests of process economy.
In the press agglomeration process, the surfactant containing granules are shear-compacted under pressure and, at the same time, homogenized and are then discharged from the machine via a shaping/forming stage. Industrially the most important press agglomeration processes are extrusion, roll compacting, pelleting and tabletting. Press agglomeration processes preferably used in accordance with the invention for producing the surfactant-containing granules are extrusion, roll compacting and pelleting.
In a preferred embodiment of the invention, the surfactant-containing granules are preferably delivered continuously to a planetary roll extruder or to a twin-screw extruder with co-rotating or contra-rotating screws, of which the barrel and the extruder/granulation head may be heated to the predetermined extrusion temperature. Under the shearing effect of the extruder screws, the premix is compacted under pressure (preferably at least 25 bar or - with extremely high throughputs - even lower, depending on the machine used), plasticized, extruded in the form of fine strands through the multiple-bore die in the extruder head and, finally, chopped by means of a rotating blade into preferably substantially spherical or cylindrical granules. The bore diameter of the multiple-bore extrusion die and the length to which the extruded strands are cut are adapted to the size selected for the granules. In this embodiment, it is possible to produce granules with a substantially uniform predetermined particle size, the absolute particle sizes being adaptable to the particular application envisaged. Important embodiments comprise the production of uniform granules in the millimeter range, for example in the range from 0.8 to 5 mm and, more particularly, in the range from about 1.0 to 3 mm. In one important embodiment, the length-to-diameter ratio of the primary granules formed by cutting the extruded strands is between about 1:1 and about 3:1. In another preferred embodiment, the still plastic primary granules are subjected to another shaping or forming step in which the edges present on the crude extrudate are rounded off so that spherical or substantially spherical granules can ultimately be obtained. Alternatively, extrusion/ compression can also be carried out in low-pressure extruders, in a Kahl press or in a Bextruder.
In another preferred embodiment of the present invention, the surfactant-containing granules are produced by roll compacting. In this process, the surfactant-containing granules are introduced between two rollers - either smooth or provided with depressions of defined shape -and rolled under pressure between the two rollers to form a sheet-like compactate. The rollers exert a high linear pressure on the premix and may be additionally heated or cooled as required. Where smooth rollers are used, smooth untextured compactate sheets are obtained. By contrast, where textured rollers are used, correspondingly textured compactates or individual pellets, in which for example certain shapes can be imposed in advance on the subsequent granules, can be produced.
The sheet-like compactate is then broken up into smaller pieces by a chopping and size-reducing process and can thus be processed to granules which can be further refined and, more particularly, converted into a substantially spherical shape by further surface treatment processes known per se.
In another preferred embodiment of the present invention, the surfactant-containing granules are produced by pelleting. In this process, the surfactant-containing granules are applied to a perforated surface and forced through the perforations by a pressure roller. In conventional pellet presses, the surfactant-containing granules are compacted under pressure, plasticized, forced through a perforated surface in the form of fine strands by means of a rotating roller and, finally, are size-reduced to granules by a cutting unit. The pressure roller and the perforated die may assume many different forms. For example, flat perforated plates are used, as are concave or convex ring dies through which the material is pressed by one or more pressure rollers. In perforated-plate presses, the pressure rollers may also be conical in shape. In ring die presses, the dies and pressure rollers) may rotate in the same direction or in opposite directions. A press suitable for carrying out the process according to the invention is described, for example, in DE-OS 38 16 842 (Schliiter GmbH).
The ring die press disclosed in this document consists of a rotating ring die permeated by pressure bores and at least one pressure roller operatively connected to the inner surface thereof which presses the material delivered to the die space through the pressure bores into a discharge unit. The ring die and pressure roller are designed to be driven in the same direction which reduces the shear load applied to the premix and hence the increase in temperature which it undergoes. However, the pelleting process may of course also be carried out with heatable or coolable rollers to enable the premix to be adjusted to a required temperature.
The surfactant granules are then mixed with other aftertreatment components to form a premix which may then be compressed to detergent tablets. In addition to the ingredients already mentioned, the premix to be compressed may contain other typical detergent ingredients as aftertreatment components, more particularly from the group of builders, disintegration aids, bleaching agents, bleach activators, enzymes, pH
regulators, fragrances, perfume carriers, fluorescers, dyes, foam inhibitors, silicone oils, redeposition inhibitors, optical brighteners, discoloration inhibitors, dye transfer inhibitors and corrosion inhibitors. However, the substances mentioned, either wholly or in part, may already form part of the surfactant granules.
Accordingly, the present invention also relates to a process for the production of detergent tablets by mixing surfactant-containing granules with fine-particle aftertreatment components and subsequent forming/shaping in known manner, characterized in that the ratio of nonionic to anionic surfactants in the tablets is in the range from 0.4:1 to 3:1.
In a preferred variant of the process according to the invention, the ratio of nonionic to anionic surfactants in the tablets is in the range from 0.45:1 to 2.5:1, preferably in the range from 0.5:1 to 2:1 and more preferably in the range from 0.75:1 to 1.5:1.
As mentioned above, the surfactants can be introduced into the tablets in various ways, their incorporation via surfactant granules being particularly advantageous. In this case, process-related advantages can arise from the separation of anionic and nonionic surfactants so that processes in which two batches of surfactant-containing granules are mixed with fine-particle aftertreatment components and the resulting mixtures are subjected to subsequent forming/shaping in known manner, one batch of granules containing the anionic surfactants and the other batch containing the nonionic surfactants, represent preferred embodiments of the invention.
It is of course also possible to use only a single batch of surfactant-containing granules, i.e. to carry out a variant of the process in which one batch of surfactant granules is mixed with fine-particle aftertreatment components and the resulting mixture is subjected to subsequent forming/shaping in known manner, the surfactant granules containing both anionic and nonionic surfactants.
In this variant of the process, the surfactant-containing granules preferably have total surfactant contents of 5 to 60% by weight, preferably 10 to 50% by weight and more preferably 15 to 40% by weight, based on the weight of the surfactant granules, the surfactant granules having anionic surfactant contents of preferably 5 to 45% by weight, more preferably 10 to 40% by weight and most preferably 15 to 35% by weight and nonionic surfactant contents of preferably 1 to 30% by weight, more preferably 5 to 25% by weight and most preferably 7.5 to 20% by weight, based on the weight of the surfactant granules.
Besides the surfactant granules, the detergent tablets according to the invention may contain other detergent ingredients, for example disintegration aids, bleaching agents, bleach activators, dyes and perfumes, etc. These substances, which may also be part of the surfactant granules, are described in the following.
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 pharma-zeutischen Technologie" (6th Edition, 1987, pages 182-184), tablet disintegrators or disintegration accelerators are auxiliaries which promote 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 disintegration aids are, for example, synthetic polymers, such as polyvinyl pyrrolidone (PVP), or natural polymers and modified natural substances, 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~o05)~ and, formally, is a ~-1,4-polyacetal of cellobiose which, in turn, is made up of 2 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 granular or optionally co-granulated disintegrators are described in German patent applications DE 197 09 991 (Stefan Herzog) and DE 197 10 254 (Henkel) and in International patent application WO 98140463 (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 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 Nm and which can be compacted, for example, to granules with a mean particle size of 200 Nm.
In order further to improve their mechanical properties, for example their abrasion resistance, the tablets may also be provided with a coating which covers the entire tablet. Coated detergent tablets such as these may be produced by spraying the tablets with or dipping them in a melt or solution of the coating material. In preferred embodiments of the invention, however, the detergent tablets are not provided with a coating that covers the entire tablet.
Among the compounds yielding HZ02 in water which serve as bleaching agents, sodium perborate tetrahydrate and sodium perborate monohydrate are particularly important. Other useful bleaching agents are, for example, sodium percarbonate, peroxypyrophosphates, citrate perhydrates and H202-yielding peracidic salts or peracids, such as perbenzoates, peroxophthalates, diperazelaic acid, phthaloiminoperacid or diperdodecane dioic acid. Even where the bleaching agents are used, there is no need for surfactants and/or builders so that pure bleach tablets can be produced. If pure bleach tablets are to be used in the washing of laundry, a combination of sodium percarbonate and sodium sesqui-carbonate is preferred irrespective of the other ingredients present in the tablets. If detergent or bleach tablets for dishwashing machines are being produced, bleaching agents from the group of organic bleaches may also be used. Typical organic bleaching agents are diacyl peroxides, such as dibenzoyl peroxide for example. Other typical organic bleaching agents are the peroxy acids, of which alkyl peroxy acids and aryl peroxy acids are particularly mentioned as examples. Preferred representatives are (a) peroxybenzoic acid and ring-substituted derivatives thereof, such as alkyl peroxybenzoic acids, but also peroxy-a-naphthoic acid and magnesium monoperphthalate, (b) aliphatic or substituted aliphatic peroxy acids, such as peroxylauric acid, peroxystearic acid, E-phthalimidoperoxycaproic acid [phthaloiminoperoxyhexanoic acid (PAP)], o-carboxybenzamidoperoxy-caproic acid, N-nonenylamidoperadipic acid and N-nonenylamidoper-succinates. and (c) aliphatic and araliphatic peroxydicarboxylic acids, such as 1,12-diperoxycarboxylic acid, 1,9-diperoxyazelaic acid, diperoxysebacic acid, diperoxybrassylic acid, diperoxyphthalic acids, 2-decyldiperoxy-butane-1,4-dioic acid, N,N-terephthaloyl-di(6-aminopercaproic acid).
Other suitable bleaching agents in dishwasher tablets are chlorine-and bromine-releasing substances. Suitable chlorine- or bromine-releasing materials are, for example, heterocyclic N-bromamides and N-chloramides, for example trichloroisocyanuric acid, tribromoisocyanuric acid, dibromoisocyanuric acid and/or dichloroisocyanuric acid (DICA) and/or salts thereof with cations, such as potassium and sodium.
Hydantoin compounds, such as 1,3-dichloro-5,5-dimethyl hydantoin, are also suitable.
In order to obtain an improved bleaching effect where washing is carried out at temperatures of 60°C or lower, bleach activators may be incorporated in the detergent tablets according to the invention. The bleach activators may be compounds which form aliphatic peroxocarboxylic acids containing preferably 1 to 10 carbon atoms and more preferably 2 to 4 carbon atoms and/or optionally substituted perbenzoic acid under perhydrolysis conditions. Substances bearing O-and/or N-acyl groups with the number of carbon atoms mentioned and/or optionally substituted benzoyl groups are suitable. Preferred bleach activators are polyacylated alkylenediamines, more particularly tetraacetyl ethylenediamine (TAED), acylated triazine derivatives, more particularly 1,5-diacetyl-2,4-dioxohexahydro-1,3,5-triazine (DADHT), acylated glycolurils, more particularly tetraacetyl glycoluril (TAGU), N-acylimides, more particularly N-nonanoyl succinimide (NOSI), acylated phenol sulfonates, more particularly n-nonanoyl or isononanoyloxybenzene-sulfonate (n- or iso-NOBS), carboxylic anhydrides, more particularly phthalic anhydride, acylated polyhydric alcohols, more particularly triacetin, ethylene glycol diacetate and 2,5-diacetoxy-2,5-dihydrofuran.
In addition to or instead of the conventional bleach activators mentioned above, 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, manganese-, iron-, cobalt-, ruthenium- or molybdenum-salen complexes or carbonyl complexes. Manganese, iron, cobalt, ruthenium, molybdenum, titanium, vanadium and copper complexes with nitrogen-containing tripod ligands and cobalt-, iron-, copper- and ruthenium-ammine complexes may also be used as bleach catalysts.

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 ~i-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 shell-forming substances to protect them against premature decomposition. The percentage content of the enzymes, enzyme mixtures or enzyme granules in the tablets according to the invention may be, for example, from about 0.1 to 5% by weight and is preferably from 0.1 to about 2% 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-dissolving component is soiled. Preferred oil- and fat-dissolving components 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 hydroxy-propoxyl 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 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)-diphen-yl, may also be present. Mixtures of the brighteners mentioned above may also be used.
Dyes and fragrances 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 fragrances include individual fragrance compounds, for example synthetic products of the ester, ether, aldehyde, ketone, alcohol and hydrocarbon type. Fragrance 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, citronellyloxy-acetaldehyde, 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 fragrances which together produce an attractive fragrance note are preferably used. Perfume oils such as these may also contain natural fragrance 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 less than 0.01 % by weight of dyes whereas perfumes/fragrances can make up as much as 2% by weight of the formulation as a whole.
The fragrances may be directly incorporated in the detergents according to the invention, although it can also be of advantage to apply the fragrances 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.
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 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.
Before the particulate premix is compressed to form detergent tablets, it may be "powdered" with fine-particle surface treatment materials.
This can be of advantage to the quality and physical properties of both the premix (storage, tabletting) and the final detergent tablets. Fine-particle powdering materials have been known for some time in the art, zeolites, silicates and other inorganic salts generally being used. However, the compound is preferably "powdered" with fine-particle zeolite, zeolites of the faujasite type being preferred. In the context of the present invention, the expression "zeolite of the faujasite type" encompasses all three zeolites which form the faujasite subgroup of zeolite structural group 4 (cf.
Donald W. Breck: "Zeolite Molecular Sieves" John Wiley & Sons, New York/London/Sydney/Toronto, 1974, page 92). Besides zeolite X, therefore, zeolite Y and faujasite and mixtures of these compounds may also be used, pure zeolite X being preferred.
According to the invention, preferred processes for the production of detergent tablets are those in which the, or one of the, fine-particle aftertreatment components subsequently incorporated is a zeolite of the faujasite type with particle sizes below 100 Nm, preferably below 10 Nm and more preferably below 5 Nm and makes up at least 0.2% by weight, preferably at least 0.5% by weight and more preferably more than 1 % by weight of the premix to be compressed.
In preferred processes according to the invention, the premix to be compressed has a bulk density of at least 500 g/I, preferably of at least 600 g/I and more preferably above 700 g/I and additionally contains one or more substances from the group of disintegration aids, bleaching agents, bleach acivtators, enzymes, pH regulators, fragrances, perfume carriers, fluorescers, dyes, foam inhibitors, silicone oils, redeposition inhibitors, optical brigtheners, discoloration inhibitors, dye transfer inhibitors and corrosion inhibitors.

To produce the tablets according to 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 the weight and shape of the tablet formed being determined by the position of the lower punch and the shape of the die. Uniform metering, even at high tablet throughputs, is preferably achieved by volumetric metering of the premix. As the tabletting process continues, the top punch comes into contact with the premix and continues descending towards the bottom 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 compound. 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.
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, KILIAN, Cologne, KOMAGE, Kell am See, KORSCH Pressen GmbH, Berlin, Mapag Maschinenbau AG, Bern (Switzerland) and Courtoy N.V., Halle (BE/LU). One example of a particularly suitable tabletting machine is the model HPF 630 hydraulic double-pressure press manufactured by LAEIS, D.
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 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 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 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 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 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 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=
~Dt where a 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 surfactant granules which, after mixing with fine-particle aftertreatment components, are compressed in known manner to form detergent tablets and in which the ratio of nonionic to anionic surfactants is in the range from 0.4:1 to 3:1 for improving the abrasion resistance of detergent tablets.. Through the use of the surfactants in a defined ratio by weight, the physical properties of the tablets can be improved, as shown by the following Examples:

Examples Various surfactant granules differing in their nonionic and anionic surfactant contents were produced by wet granulation in a 130-liter Lodige plowshare mixer. After granulation, the granules were dried in an Aeromatic fluidized bed dryer for 30 minutes at an inflowing air temperature of 60°C. After drying, the granules were sieved to remove the fine particles (< 0.06 mm) and coarse fractions (> 1.6 mm).
The surfactant granules E1 to E4 and V1 and V2 were then mixed with other components to form a compressible premix which was then tabletted in a Korsch eccentric press (tablet diameter 44 mm, height 22 mm, weight 37.5 g). The measured tablet hardnesses and disintegration times are the mean values of a double determination, the individual values varying by at most 2 N and 2 s, respectively, according to the type of tablet. The composition of the surfactant granules is shown in Table 1 while the composition of the premixes to be tabletted (and hence the tablets) is shown in Table 2.
Table 1: Composition of the surfactant granules [% by weight]
E1 E2 E~ E4 1f1' lt2 Cg~3 alkyl benzenesulfonate7.5 12.7 15.0 15.5 18.0 18.0 C,z_~8 fatty alcohol 2.5 4.3 5.0 5.5 6.0 6.0 sulfate C,z_~8 fatty alcohol 21.0 14.0 11.0 10.0 7.0 7.0 sulfate + 7E0 Soap 1.3 1.3 1.3 1.3 1.3 1.3 Sodium carbonate 10.0 10.0 10.0 10.0 10.0 10.0 Sodium sulfate 5.0 5.0 5.0 5.0 5.0 5.0 Zeolite A - 34.8 34.9 35.0 35.0 -Zeolite X 34.8 - - _ - 35.0 Na hydroxyethane-1,1- 1.0 1.0 1.0 1.0 1.0 1.0 diphosphonate Acrylic acid/maleic acid6.0 6.0 6.0 6.0 6.0 6.0~
copolymer NaOH, water-free active 0.1 0.1 0.1 0.1 0.1 0.1 substance Water, salts Rest Rest Rest Rest Rest Rest Sum of nonionic surfactant21.0 14.0 11.0 10.0 7.0 7.0 Sum of anionic surfactants11.3 18.3 21.3 22.3 25.3 25.3 Ratio of nonionic to 1.86:10.77:10.52:10.45:10.28:10.28:1 anionic surfactant Table 2: Composition of the premixes [% by weight]
Surfactant granules (Table 62.05 1) Sodium perborate monohydrate 17.4 TAED 7.3 Foam inhibitor 3.5 Enzymes 1.7 Repel-O-Tex~ SRP 4* 1.1 Perfume 0.5 Wessalith~ P (zeolite A) 1.0 Disintegration aid (cellulose)5.0 * Terephthalic acid/ethylene glycol/polyethylene glycol ester (Rhodia, Rhone-Poulenc) The hardness of the tablets was measured after two days' storage 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.
Dissolvability was tested in a Miele Novotronic W918 washing machine (main wash cycle, 60°C). After the flushing in phase (three tablets, cold mains water with a hardness of 16° dH), the residues were dried and weighed out.
Abrasion resistance was determined by placing a tablet on a 1.6 mm mesh sieve. The sieve was then placed in a Retsch analytical sieving machine and stressed at an amplitude of 2 mm for 120 seconds. The abrasion in % can be calculated by weighing the tablet on the sieve before and after stressing. The experimental data are shown in Table 3:
Table 3: Detergent tablets [physical data]
Tat~~et E1 E~ E3 E4 V1: V2 Tablet hardness 39 40 38 41 41 40 [N]

Residue [g] 3 7 7 4 6 6 Abrasion [%] 12 3 10 15 23 38 Whereas the hardnesses and residue values of tablets E and V are of the same order, the tablets E according to the invention show far better resistance to the friction effect of the vibrating sieve. A nonionic to anionic surfactant ratio below 0.4:1 (V1, V2) leads to tablets which lose a quarter (v1 ) and two fifths (V2) of their weight. With such drastic losses of weight, the original form of the tablet is no longer visible. The performance properties are thus further improved by the ratio of nonionic to anionic surfactant according to the invention.
.r._......_.~.~ . .~........_.,_

Claims

1. A detergent tablet comprising compacted detergent granules containing builders, anionic and nonionic surfactants and optionally other detergent ingredients, wherein the ratio of nonionic to anionic surfactants in the tablet is in the range from 0.4:1 to 3:1.

2. The detergent tablet as claimed in claim 1, wherein the ratio of nonionic to anionic surfactants is in the range from 0.45:1 to 2.5:1.

3. The detergent tablet as claimed in claim 1 wherein the tablet contains more than 5% by weight of anionic surfactants, based on tablet weight.

4. The detergent tablet as claimed in claim 1, wherein the tablet contains more than 2% by weight of nonionic surfactants, based on tablet weight.

5. The detergent tablet as claimed in claim 1 wherein the tablet contains the surfactants in the form of surfactant-containing granules which are present in the tablets in quantities of 40 to 95% by weight based on tablet weight.

6. The detergent tablet as claimed in claim 5, wherein the surfactant granules have surfactant contents of 5 to 60% by weight based on the weight of the surfactant granules.

7. The detergent tablet as claimed in claim 5 wherein the surfactant granules have anionic surfactant contents of 5 to 45% by weight, based on the weight of the surfactant granules.

8. The detergent tablet as claimed in claim 1 wherein the surfactant granules have nonionic surfactant contents of 1 to 30% by weight, based on the weight of the surfactant granules.

9. The detergent tablet as claimed in claim 1 wherein the tablet contains less than 10% by weight, of potassium carbonate, based on tablet weight.

10. The detergent tablet as claimed in claim 1 wherein the nonionic surfactants present in the tablet have a melting point below 40°C.

11. A process for the production of detergent tablets which comprises:
mixing surfactant-containing granules with fine-particle after treatment components to form a mixture and subsequently forming/shaping the mixture to form a tablet the ratio of nonionic to anionic surfactants in the tablet is in the range from 0.4:1 to 3:1.

12. The process as claimed in claim 11, wherein the ratio of nonionic to anionic surfactants in the tablet is in the range from 0.45:1 to 2.5:1.

13. The process as claimed in claim 11 wherein two batches of surfactant-containing granules are mixed with fine-particle aftertreatment components and the resulting mixture is subjected to subsequent forming/shaping to form the tablet, wherein one batch of granules contains the anionic surfactants and the second batch of granules contains the nonionic surfactants.

14. The process as claimed in claim 11 wherein the surfactant-containing granules are mixed with fine-particle aftertreatment components and the resulting mixture is subjected to subsequent forming/shaping to form the tablet, the surfactant granules containing both anionic and nonionic surfactants.

15. The process as claimed in claim 14, wherein the surfactant-containing granules have total surfactant contents of 5 to 60% by weight, based on the weight of the surfactant granules, the surfactant granules having anionic surfactant content of 5 to 45% by weight, and nonionic surfactant content of 2 to 30% by weight based on the weight of the surfactant granules.

16. The process as claimed in claim 11 wherein the surfactant-containing granules are formed by a method selected from the group consisting of granulation, agglomeration, press agglomeration or a combination of these methods.

17. The process as claimed in claim 11 wherein the premix to be tabletted has a bulk density of at least 500 g/l.

18. The process as claimed in claim 11 wherein the premix to be tabletted additionally contains at least one substance selected from the group consisting of disintegration aids, bleaching agents, bleach activators, enzymes, pH regulators, fragrances, perfume carriers, fluorescers, dyes, foam inhibitors, silicone oils, redeposition inhibitors, optical brighteners, discoloration inhibitors, dye transfer inhibitors and corrosion inhibitors.

19. A method for improving the abrasion resistance of detergent tablets which comprises compressing a mixture comprising granules containing nonionic and anionic surfactants with a ratio of nonionic surfactants to anionic surfactants of from 0.4:1 to 3:1 and fine particle aftertreatment components.

20. The detergent tablet of claim 2 wherein the ratio of nonionic surfactant to anionic surfactants is from 0.5:1 to 2:1.

21. The detergent tablet of claim 5 wherein the surfactant containing granules are present in the tablet at from 55% to 85% by weight of the tablet.

22. The detergent tablet of claim 6 wherein the surfactant granules contain from 10% to 50% by weight of surfactant.