It is especially applicable to laundry tablets. It is also useful for formulating pesticide unit dose tablets, e. g. for horticultural applications.

Laundry tablets typically comprise as their main ingredients a surfactant mixture and a solid builder. The surfactant mixture typically comprises an anionic surfactant, often with a minor proportion of nonionic, and the builder is usually sodium tripolyphosphate, or less commonly, zeolite.

The main problem in formulating laundry tablets has been to obtain a product sufficiently strong to withstand normal handling, but sufficiently easily broken down by moisture to dissolve rapidly in wash liquor.

The problem has been met mainly by controlling particle size, by including rapidly soluble particles, such as phase 1 sodium tripolyphosphate, by choice of surfactant/solid ratio and by adding water swellable polymers.

Tablets are usually made from a base powder which is a spray dried or fluid-bed granulated mixture of those components of the tablet which are stable and compatible with water and with one another, under the conditions of spray drying or granulation.

The powder is blended with the remaining components, e. g. those which are sensitive to water, and the blend is then compressed into a tablet.

The tablets comprise a substantially higher concentration of wash-functional components than conventional powders because there is relatively little need for diluents, such as sodium sulphate, needed to make powders free flowing. Because of the higher levels of surfactant, which may make the base powder too sticky for convenient handling, it is sometimes preferred to include only part of the total surfactant in the liquor used to make the base powder and subsequently to blend the rest of the surfactant into the base powder, along with the water sensitive components such as bleach, phase 1 tripolyphosphate and water-swellable polymers.

Generally, the higher the compaction pressure, the stronger is the tablet but the slower the rate of dissolution. For a given formulation, the compaction pressure is adjusted to give a specified compression-fracture-strength (e. g. 70-80N).

The size of the laundry tablet has been largely fixed by the optimum dose of wash- functional laundry solids required for an average wash load, which is about 80g. To provide flexibility to cope with very light or extra heavy loads the standard tablet is half this amount (i. e. 40g), thereby enabling 40,80 or 120g dosages to be achieved by the use of one or more tablets.

We have discovered that laundry tablets, wherein the surfactant consists essentially of nonionic and amphoteric surfactants, give superior performance in soil removal compared to tablets containing anionic and non-ionic surfactants. This enables the consumer to use less surfactant per wash, and so permits the preparation of smaller and more compact tablets.

In conformity with the normal usage in the art, the term"amphoteric surfactant"is used herein to include those surfactants, which are more accurately described as zwitterionic.

In particular, we have discovered that the incorporation of aluminosilicates, preferably comprising a water-swellable clay, and especially a smectite clay such as bentonite or montmorillonite, into amphoteric laundry tablets, permits substantially stronger tablets to be obtained, without impairing dispersibility, even in relatively low concentrations.

We have further discovered that the strength of the tablet is increased, if at least part of the non-ionic surfactant is adsorbed onto, or absorbed in, solid inorganic particles, and especially particles comprising the water-swellable clay, prior to mixing with the amphoteric surfactant. However, we have found that if all the non-ionic surfactant is incorporated in this way the powder may exhibit an unacceptable tendency to segregate during handling or storage, but that if part of the non-ionic surfactant is premixed with the inorganic particles prior to mixing with the amphoteric surfactant, and another part is subsequently added directly to the powder in liquid form, an advantageous combination of physical stability of the powder prior to compaction, with strength of the compacted tablet, may be obtained.

In the following discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

The invention provides a method of preparing a powder, for compaction into tablets, comprising an amphoteric surfactant, a liquid non-ionic surfactant and particles comprising an aluminosilicate, characterised in that at least part of said non-ionic surfactant is premixed with at least part of said aluminosilicate.

According to a first preferred embodiment the invention provides a method of making a powder detergent, for compaction into tablets, which comprises: a mixture of surfactants consisting essentially of amphoteric surfactant and non-ionic surfactant and solid inorganic particles, said method comprising the steps of : (1) forming a bed of at least some of said particles; (2) spraying an aqueous solution of amphoteric surfactant onto said bed and drying said solution by heating and/or evacuation and/ or the action of particles of hydrateable salt included in the bed, characterised in that at least some of said particles are granules of aluminosilicate with at least part of said non-ionic surfactant absorbed therein and/or adsorbed thereon..

A second preferred embodiment of our invention provides a method of preparing a powder, for compaction into tablets, which comprises blending together particles of a solid amphoteric surfactant containing less than 10% moisture based on the weight thereof, and solid particles comprising granules of aluminosilicate with non-ionic surfactant absorbed therein and/or adsorbed thereon..

According to a further, particularly preferred embodiment, the invention provides a method of preparing a powder, for compaction into tablets, which comprises mixing together: an amphoteric surfactant; a liquid, non-ionic surfactant; and particles comprising an aluminosilicate, capable of absorbing or adsorbing at least part of said non-ionic surfactant; characterised in that, from 20 to 95% of the total weight of said liquid non-ionic surfactant is premixed with said particles to form a solid, particulate premix comprising said aluminosilicate and having said non-ionic surfactant adsorbed thereon or absorbed therein, said premix is mixed with said amphoteric surfactant to form a mixture, and from 5 to 80% of the total weight of said non-ionic surfactant is added to said mixture as a liquid. The premixed non-ionic surfactant, and the non- ionic surfactant added subsequently to the mixture, may be the same or different.

Preferably an aqueous solution of the amphoteric surfactant is sprayed onto an agitated (e. g. stirred or, preferably, fluidised) bed of clay and/or other inorganic, e. g. builder, particles. The solution is preferably dried by heating, preferably at a temperature below the softening point of the amphoteric surfactant, and/or by maintaining a sub-atmospheric pressure, and/or, most preferably, by incorporating particles of a hydrateable salt in the bed.

In one, preferred, method, aqueous amphoteric surfactant is sprayed onto a bed of, e. g. builder particles, and the dried particles are then blended with the aluminosilicate/ non-ionic granules. Where aqueous amphoteric surfactant is sprayed onto a substrate, it is preferred to use solutions containing at least 20%, by weight, of the surfactant, more preferably at least 25%, most preferably 30 to 40%.

The aluminosilicate preferably comprises a water-swellable clay and/or zeolite.

Preferred water-swellable clays include smectite clays such as montmorillonite or, preferably, bentonite The mean particle size, and preferably the size of at least the majority of the particles, is preferably greater than 250p, more preferably greater than 300t, even more preferably greater than 400p, more preferably still, greater than 500u, most preferably greater than 600. It is preferred that the mean particle size, and preferably also the major proportion by weight, of the particles, is less than 2mm, more preferably less than 1. 5mm, even more preferably less than lmm, most preferably less than 700z.

The proportion, by weight, of the particles, which is less than 250A, is preferably less than 10%, more preferably less than 5%, even more preferably less than 2%, most preferably less than 1%.

The powder preferably comprises a mixture of surfactants consisting essentially of amphoteric and non-ionic surfactants. Preferably the powder contains particles comprising builders, diluents, water-swellable polymers and/or wash adjuvants.

The builder for use according to our invention preferably comprises sodium tripolyphosphate, and most preferably sodium tripolyphosphate crystals containing more than 60% by weight thereof of phase I, and 1 to 10%, more preferably 2 to 6%, by weight, of moisture, which is preferably supplied, at least partly by the aqueous solution of amphoteric surfactant. Alternatively or additionally the builder may, for example, comprise zeolite, sodium or potassium carbonate, sodium or potassium citrate, sodium silicate, potassium pyrophosphate, sodium or potassium ethylenediamine tetracetate, sodium or potassium nitrilotriacetate, or a polycarboxylate.

The diluent, where required, typically comprises sodium sulphate, although any inert particulate solid could be used.

Wash adjuvants may, for example, include: bleach, such as sodium perborate or sodium percarbonate; bleach activators, such as tetraacetyl ethylenediamine ; enzymes, such as proteases, lipases and/or cellulases ; phosphonates, such as amino tris (methylene phosphonates), ethylene diamine tetrakis (methylene phosphonates) and diethylenetriamine pentakis (methylene phosphonates); antifoams, such as silicone antifoams or mineral oils ; antiredeposition agents, such as sodium carboxymethylcellulose ; optical brighteners; alkalis ; fabric conditioners; perfumes; preservatives; pigments; dyes and/or polymers.

The surfactant comprises non-ionic surfactant, preferably including non-ionic polyethoxylates, most preferably alkyl polyethoxylates having straight chain or branched alkyl or alkenyl groups with from 8 to 25, preferably 10 to 20 carbon atoms and an average of 1 to 60, preferably. 2 to 50, more preferably 3 to 10, ethylenoxy groups.

Typically the HLB of the non-ionic surfactant, or mean HLB of the mixture of non- ionic surfactants, is greater than 8, preferably greater than 9, more preferably greater than 10, even more preferably greater than 10.5, most preferably greater than 11, but less thanl6, preferably less than 15, more preferably less than 14, most preferably less than 13.

The non-ionic surfactant may optionally comprise, in addition to or instead of alkyl ethoxylates, other ethoxylates including fatty acid ethoxylate, fatty ester ethoxylate, e. g. sorbitan or glyceryl ester ethoxylates, amine ethoxylate, alkyl phenyl ethoxylates, polyoxypropylene ethoxylates, ethoxylated alkanolamides and ethoxylated phosphate esters.

In addition to, but preferably not instead of, ethoxylates the product may contain alkyl polyglycosides. The product may also contain sugar esters, alkanolamides, and/or amine oxides. The last are considered to be non-ionic surfactants for the purpose of this specification, notwithstanding the fact that they are sometimes classified separately in the literature.

The non-ionic surfactant preferably constitutes more than 20%, more preferably more than 30%, even more preferably more than 40%, more preferably still, more than 50%, most preferably more than 60% and sometimes more than 70%, by weight of the total surfactant. Preferably, however, the non-ionic surfactant constitutes less than 90%, more preferably less than 80%, most preferably less than 70% of the total weight of surfactant.

The amphoteric surfactant may comprise a betaine, e. g. a betaine of the general formula : RR12N+CH2COO-, wherein R is an aliphatic hydrocarbyl, hydrocarbyl amido alkyl or hydrocarbyl ether group having an average of from 8 to 30, preferably 10 to 25, more preferably 15 to 25 aliphatic carbon atoms and Rl is an alkyl or hydroxy alkyl group having an average of from 1 to 4 carbon atoms. Particularly preferred are the alkylamido betaines, e. g. of the formula: R2CONH (CH2) n. (R') 2N+CH2COO- ; where R is a C8-25, preferably C12-2o, alkyl group, n is from 2 to 4, and R'has the same significance as before. We especially prefer the C8. 25 alkyl amido propyl betaines, such as coconut amido propyl betaine (CAPB) or any of the corresponding alkyl and alkenyl amido propyl betaines derived from natural palm or coconut fatty acids or from synthetic carboxylic acids having a similar alkyl chain distribution often loosely referred to as CAPB, including hardened and unhardened full or cut oils.

Especially preferred are lauryl amido propyl betaine and other narrow cut alkyl amido propyl betaines, such as stearyl.

Also of use are the so-called quaternary imidazoline betaines, also called amphoacetates, and traditionally ascribed the formula: although they are actually present, at least predominantly, as the corresponding linear amido amine which is usually obtained commercially in admixture with the dicarboxymethylated form wherein R is an aliphatic group having from 8 to 25 carbon and Ru ils an alkyl or hydroxyalkyl group with from 1 to 4 carbon atoms. Other amphoteric surfactants for use according to our invention include alkyl amino propionates, alkylamine polyalkoxy sulphates, sulphobetaines, amido sulphobetaines, phosphobetaines and other quaternary amine or quaternised imidazoline sulphonic acids and their salts, and zwitterionic surfactants, e. g. N-alkyl taurines, carboxylated amido amines such as RCONH (CHZ)"N+ RZCHZCO'2 where n is 2 to 4, and amino acids having, in each case, at least one aliphatic group having from 8 to 25 carbon atoms.

Conventional, undesalted solutions of betaine sometimes provide undesirably sticky products, when sprayed onto a bed of particles, if the surfactant loading exceeds about 20%, by weight, of betaine, based on the dry weight of the particle. It is impractical to get loadings above about 25% in this way. However a desalted solution can provide loadings up to 50%.

The amphoteric surfactant may, alternatively, be added as a solid, which is preferably substantially anhydrous. By this is meant a moisture content less than 10%, preferably less than 8%, more preferably 1 to 6%, by weight of said amphoteric surfactant. However, undesalted solid amphoteric surfactants are hygroscopic. Any solid amphoteric is therefore preferably desalted. Desalting of amphoteric surfactants may conveniently be effected by membrane filtration or electroosmosis.

The sodium chloride content of desalted amphoteric surfactant is preferably less than 12% by weight of said amphoteric surfactant, more preferably less than 10%, even more preferably less than 8%, more preferably still, less than 5%, most preferably less than 3%, e. g. less than 1%.

We particularly prefer that the total inorganic salt content of the amphoteric surfactant is less than 15%, more preferably less than 10% most preferably less than 5%.

Aqueous solutions of low-salt amphoteric surfactant are able to provide higher loading of surfactant when sprayed onto inorganic substrates without losing long term stability.

Anhydrous amphoteric surfactant preferably comprises and most preferably consists of a CAPB derivative and in particular of laurylamidopropyl betaine..

We prefer that any solid amphoteric surfactant is based on a narrow cut alkyl feedstock, e. g. comprising more than 70% more preferably more than 80% most preferably more than 90% especially more than 95% of a single homologue. Said single homologue is preferably a betaine of the aforesaid general formula, wherein R has at least 15 aliphatic carbon atoms. For example the feedstock may be a narrow cut and/or hardened (i. e. hydrogenated) coconut or palm oil, or synthetic equivalent.

The solid amphoteric is preferably substantially non-hygroscopic i. e. it does not form a liquid or mesophase on standing in humid air. Preferably it has an equilibrium water content less than 10% at 40°C in an atmosphere having 65% humidity.

For laundry tablets, we prefer that the amphoteric surfactant constitute at least 0.25%, by weight of the composition, more preferably more than 0.5%, even more preferably more than 1%, most preferably more than 2%. , but is usually less than 50%, preferably less than 40%, more preferably less than 30%, even more preferably less than 20%, more preferably still, less than 10%, most preferably less than 5%.

Solid amphoteric surfactant is preferably added in particulate form, e. g. as powder, granules or needles.

For laundry applications it is generally preferred that the surfactant consists essentially of amphoteric and non-ionic surfactants. By this we mean that anionic and cationic surfactants, which tend to reduce the soil removing effectiveness of amphoteric/non-ionic mixtures, are substantially absent, i. e. not present in amounts sufficient, materially, to affect the soil removing performance of the surfactant mixture. What constitutes a substantial presence will, of course, depend on context, but in concrete terms, and without prejudice to the generality of the foregoing, we envisage anionic and cationic surfactants being present in laundry detergents of the invention in amounts less than 10% by weight of the total surfactant, preferably less than 5%, more preferably less than 2%, still more preferably less than 1%, most preferably less than 0.5%.

For laundry formulations, the total proportion of builder in the powder, or in the tablet may, for example, be greater than 10%, preferably greater than 15%, more preferably greater than 20%, even more preferably greater than 30%, more preferably still, greater than 40%, most preferably greater than 45%, e. g. greater than 50%, by weight based on the weight of the powder or tablet. Generally the proportion of builder is less than 90%, preferably less than 80%, more preferably less than 70%, e. g. less than less than 60%, by weight based on the weight of the powder or tablet.

The aluminosilicate may comprise a water-swellable clay, such as bentonite, which is preferably present in a proportion of greater than 0. 01%, preferably greater than 0. 1%, more preferably greater than 0.5%, even more preferably greater than 1%, more preferably still, greater than 1.5%, most preferably greater than 2%, by weight based on the total weight of the powder. The clay may typically constitute up to 25%, preferably less than 20%, more preferably less than 15%, even more preferably less than 10%, more preferably still, less than 5%, most preferably, less than 3%, by weight based on the total weight of the powder.

The clay may be incorporated into the composition as mixed granules comprising other inorganic material, including minerals, such as zeolite, or sodium tripolyphosphate. Such mixtures are preferred when a white tablet is required. For such formulations the amount of clay in the mixed granule may be less than 50% of the weight of the granule, preferably less than 30%, more preferably less than 20%, even more preferably, less than 10%, more preferably still, less than 5%, most preferably less than 3%.

The proportion of non-ionic surfactant used to make the premix is preferably at least 30%, more preferably at least 50%, even more preferably at least 70%, more preferably still, at least 75%, most preferably at least 80%, by weight, based on the total weight of non-ionic surfactant in the formulation.

If all the non-ionic surfactant is added in the premix there is a tendency for the components of the powder to segregate, in the course of transport, handling or storage, after the powder has been blended, and prior to compaction into a tablet. This can be reduced or avoided by adding a small amount of liquid non-ionic surfactant to the final formulation after mixing. The added surfactant may, for example, be sprayed onto the powder. The proportion post-added in this way is chosen to give whatever balance between the physical stability of the powder and the compression strength of the compacted tablet, the user may require. Preferably at least 5% more preferably more than 8%, most preferably between 10 and 15% of the total weight of non-ionic surfactant is post-added.

Compositions of our invention preferably contain at least 5%, more preferably at least 10%, most preferably at least 15%, optionally more than 20%, sometimes more than 30%, occasionally more than 40% of amphoteric surfactant, based on the total weight of the surfactant. The amphoteric surfactant usually constitutes less than 70%, preferably less than 60%, typically less than 50% of the total weight of the surfactant.

The compacted blend of amphoteric surfactant and solid particles may constitute the whole, or only a region or part of the total tablet. For example the tablet may comprise two or more layers of which at least one may consist of ingredients other than the amphoteric surfactant.

The tablet may be any convenient shape such as cuboid, disc or spheroid. It may be designed for direct addition to the drum or, if sufficiently soluble, to the drawer of a washing machine.

The invention has been described primarily in relation to cleaning compositions, but is useful for a variety of applications, in which an active ingredient needs to be dissolved rapidly in water, in conjunction with a surfactant. For example, biocides, including sterilants for clinics or hospitals, disinfectants for domestic, institutional, industrial or agricultural applications, or herbicides or pesticides for agricultural or horticultural use, may be formulated, together with wetting agents, as rapidly dissolving tablets in accordance with the teaching herein.

An example of a herbicide that can, advantageously, be incorporated into a tablet according to the present invention is glyphosate. For example mixtures of glyphosate with dry, desalted laurylamidopropyl betaine may be so formulated, optionally together with auxiliary wetting agents, such as ether carboxylates or amine oxides,, and/or disintegrants, such as a mixture of citric acid and sodium carbonate, or a water swellable polymer.

The invention is especially useful for active ingredients that are too water sensitive to be stored for extended periods in aqueous solutions, suspensions or emulsions.

The compositions described herein, are envisaged primarily as being for use in the form of tablets. However the powder compositions of the invention are capable of being used as such, and are not excluded from the scope of the invention when so used.

The invention is illustrated by the following examples wherein all percentages are expressed by weight based on total weight, and all solid components had a mean particle size between 600 and 700t, and less than 1% by weight smaller than 250p, unless the contrary is indicated.

Example 1 A tablet powder had the following composition: Bentonite/zeolite/Cl2_ls alkyl 7mole ethoxylate granules 13. 8% High phase I sodium tripolyphosphate 41.9 Sodium percarbonate 17.2 Tetra acetyl ethylenediamine 4 Cross linked sodium carboxymethyl cellulose 4.5 C12-15 alkyl 3 mole ethoxylate 1.5 Perfume 0.5 Antifoam 0.5 CAPB/sodium carbonate (1: 3 by weight) granule 16.2 The CAPB/carbonate granule was prepared by spraying aqueous CAPB (30% CAPB, 6% sodium chloride, by weight of the solution) onto a heated fluidised bed of anhydrous sodium carbonate. The aluminosilicate granule contained approximately one third of the total weight thereof, of non-ionic surfactant, 3% by weight bentonite, and the balance zeolite.

The solid components were blended to give a powder, which tended to segregate. The 3 mole ethoxylate was sprayed on to provide a stable free flowing composition.

The powder was compacted under a pressure of 30 KN to a 30g tablet, which had a compression-strength of 65N and a disintegration time of 26s at 30°C Example 2 Example 1 was repeated using a betaine/carbonate mixture, in which the CAPB was replaced by a solution of desalted LAPB (36% LAPB, <0.2% sodium chloride).

The tablet had a compression-strength of 61N and a disintegration time of 31s at 30°C.

Example 3 A detergent powder had the composition: Bentonite/C 12-15 alkyl 7 mole ethoxylate 13. 8 % High phase 1 sodium tripolyphosphate 41.9 Sodium silicate 5.0 Sodium percarbonate 20.2 Tetra acetyl ethylenediamine 4.0 Cross linked sodium carboxymethyl cellulose 4.5 C 12-15 alkyl 3 mole ethoxylate 1.5 Perfume 0. 3 Antifoam 0.5 LAPB/sodium carbonate granule (1: 1, wt/wt) 8.1 Attempts to prepare a 50% by weight, betaine on carbonate granule, using undesalted CAPB solution, gave a sticky mass that could not be mixed satisfactorily with the other components. However desalted LAPB solution gave a dry free-flowing powder.

The powder was compacted as in Example 1. The tablet had a compression-strength of 65N and a disintegration time of 25s at 30°C.

Example 4 A granular composition, consisting of co-granules of zeolite and bentonite was sprayed with a C, 2, 5 alkyl 7 mole ethoxylate. The co-granules had a final composition of 66% zeolite, 4% bentonite and 30% non-ionic surfactant.

The co-granules were added to the following detergent powder formulation: Dry desalted LAPB 2.8% Sodium silicate 8.0 Low phase I sodium tripolyphosphate 7.1 Tetraacetyl ethylenediamine 4.5 Antifoam 0.6 Optical brighteners 0.36 High phase I (>70%) sodium tripolyphosphate 46.1 C12-14 alkyl 3 mole ethoxylate 2.8 Perfume 0.4 Sodium percarbonate granules 12.2 Co-granules 11.4 Cross-linked sodium carboxymethyl cellulose 3.8 The powder was compacted as in Example 1. The tablet had a compression-strength of 56N and a disintegration time of 33s in water at 30°C.