EP1397475A2

EP1397475A2 - Compactable powders

Info

Publication number: EP1397475A2
Application number: EP02735380A
Authority: EP
Inventors: Hendrick Petrus Frick; Richard Malcolm Clapperton
Original assignee: Huntsman International LLC
Current assignee: Huntsman International LLC
Priority date: 2001-05-31
Filing date: 2002-05-24
Publication date: 2004-03-17
Also published as: WO2002102948A3; AU2002310836A1; WO2002102948A2

Abstract

Powder compositions, which can be compacted into strong, water-dispersable tablets, such as laundry detergent tablets or bath bombs, are made by blending solid, particulate, preferably desalted, amphoteric surfactant, e.g. dried laurylamidopropyl betaine, with water-soluble and/or water-swellable inorganic and/or polymer particles, such as bentonite. A typical laundry tablet comprises a solid, non-hygroscopic, amidopropyl betaine, non-ionic surfactant, bentonite, builders and wash adjuvants.

Description

COMPACTABLE POWDERS

The invention relates to compactable powders suitable for making tablets, e.g. laundry- tablets, or bath bombs, which comprise surfactant and a particulate solid, and which can be added to aqueous systems, for example, washing machines, dishwashers, or bath- or other wash water, as a unit dose, and to tablets prepared by compacting such powders. It is especially applicable to laundry tablets. It is also useful for formulating, pesticide unit dose tablets, e.g. for horticultural applications, or sterilising tablets.

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 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).

Sodium tripolyphosphate may exist in any one of three forms: phase 1 anhydrous; phase 2 anhydrous; and hexahydrate. Commercial products often comprise a mixture of two or more of these phases. Spray dried powders contain only the hexahydrate. In general products containing relatively high proportions of phase 1 anhydrous tripolyphosphate dissolve more rapidly than either phase 2 or hexahydrate. However pure phase 1 crystals, on immersion, form a cement like composition which inhibits the disintegration of the tablet. This can be avoided if a small amount, e.g. 2 to 6% by weight of moisture is present in the crystal. A substantial proportion of any tripolyphosphate in a laundry tablet is therefore usually present as crystals, containing low proportions of phase 2, high proportions of phase 1 and a small amount of moisture, which are blended with the base powder. Other rapidly dissolving solids may be incorporated in the tablet as may water swellable polymers or effervescent mixtures such as citric acid and sodium bicarbonate, which aid disintegration. 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.

As well as laundry tablets, the invention is also applicable to bath bombs. The latter conventionally comprise a source of effervescence, e.g. a mixture of a salt of carbonic acid (typically sodium bicarbonate) with a water-soluble acid (typically citric acid). The mixture is compacted into a tablet, which disintegrates in a burst of effervescence on addition to bath water. The latter is softened by the dissolved components.

For some years manufacturers have sought to include a foaming agent in bath bombs. However it has proved extremely difficult to formulate bath bombs with a surfactant, which is high foaming and mild to skin. No satisfactory commercial product of this type currently exists.

We have found 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.

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.

The most widely used amphoteric surfactants are those of the betaine type, which are made commercially by reacting sodium chloroacetate with an amine, e.g. a tertiary amine comprising at least one long chain alkyl group, an imidazoline or amido amine. Sulphobetaines and phosphobetaines are made by analogous methods. The products are usually prepared at a concentration of about 31-35% surfactant. Attempts to concentrate these products above 36 or 37% have resulted in phase separation or given rise to intractable mesophases. Spray-drying amphoteric surfactants normally gives rise to hygroscopic solids.

The reaction with chloroacetate forms an equimolar amount of sodium chloride, and commercial amphoteric surfactants normally contain from 16 to 20% by weight of sodium chloride, based on the total weight of amphoteric surfactant. This typically corresponds to about 6 to 10% of inorganic salts, by weight, based on the total weight of aqueous surfactant. However, various methods have been proposed for removing salt from imidazolines, including membrane filtration and electroosmosis. Imidazolines containing low concentrations of inorganic salts, e.g. below 3% and even below 1% down to 0.1 or less, are available commercially for special uses. Such products are also normally available only as relatively dilute solutions or as hygroscopic solids. However we have recently found that some amphoteric surfactants derived from feedstocks with a narrow range of homologues, when desalted form a non-hygroscopic solid phase.

We have now discovered that the greater effectiveness of amphoteric surfactants, compared to anionic surfactants, enables the consumer to use less surfactant per wash. Moreover, the amount of tripolyphosphate builder in conventional laundry tablets is substantially in excess of that required for optimum wash performance. The excess is necessary to obtain sufficiently rapid dispersion of the surfactant. We have found that reducing the amount of surfactant allows the tripolyphosphate to be reduced proportionately. Since tripolyphosphate is the largest single component, amounting to nearly half the weight of a conventional tablet, this permits the preparation of substantially smaller and more compact tablets. We have also found that non-ionic / amphoteric based tablets wherein at least part of the amphoteric surfactant is blended with the other solid components in the form of a substantially anhydrous solid, which is preferably a low salt, non-hygrosopic solid, exhibit a desirable combination of strength, solubility and storage stability.

Conventional anionic tablets are unstable in moist air and must be individually wrapped, to prevent deterioration on storage. A common practice is to wrap two half- dose laundry tablets together, so that each package contains a full dose, but the consumer has the option of using the half dose for light loads. However, once the wrapper is opened, any unused tablet exposed thereby soon becomes crumbly. A similar problem is encountered, if the packaging is damaged, or faulty.

We have now found that, using non-hygroscopic amphoteric surfactants to provide at least a substantial part, preferably a major part and typically all, of the more polar component of the surfactant (i.e. excluding the non-ionic component), storage stability is greatly improved, compared with conventional anionic tablets.

We have further discovered that effervescable solid mixtures can be blended with substantially anhydrous amphoteric surfactants to form commercially acceptable foaming bath bombs.

We have further discovered that the incorporation of clay, and especially smectite clay such as bentonite or montmorillonite, into laundry tablets, permits substantially stronger tablets to be obtained, without impairing dispersibility.

We have also discovered that the strength of the tablet is increased, if at least part of the non-ionic surfactant is adsorbed onto or absorbed in a solid particulate substrate, such as bentonite, prior to incorporation into the powder. 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 a solid substrate prior to addition, and another part is 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.

According to one embodiment the invention provides a powder capable of compaction into tablets, which is formed by blending a solid surfactant with water-swellable and/or water soluble particles comprising inorganic solids and/or polymers, characterised in that the solid surfactant comprises particles consisting essentially of amphoteric surfactant. The particles of amphoteric surfactant preferably contain less than 12%, more preferably, less than 10%, most preferably less than 8%, based on the weight of amphoteric surfactant, of moisture.

Preferably the solid surfactant consists essentially of amphoteric surfactant and is a substantially non-hygroscopic solid containing less than 12% of sodium chloride, based on the weight of amphoteric surfactant.

The mean particle size, and preferably the size of at least the majority of particles, of the amphoteric surfactant is preferably greater than 300μ, more preferably greater than 500μ, most preferably greater than 700μ, usually greater than 750μ, especially greater than lOOOμ. It is preferred that the mean particle size, and preferably also the major proportion by weight, of the amphoteric surfactant particles, is less than 4mm, more preferably less than 3 mm, most preferably less than 2mm, especially less than 1.5mm.

The proportion, by weight, of the solid amphoteric surfactant, which is less than 250μ, is preferably less than 10%, more preferably less than 5%, most preferably less than 2%, especially less than 1%.

Wherever the context allows, references herein to particles of greater than or less than a given size are to be construed in its normal sense as referring to particles respectively retained by, or passing through, a sieve of the appropriate pore size, where the particles are approximately spheroidal, e.g. where the ratio of the biggest dimension to the smallest is less than about 1.5. In the case of needles, particle size refers to the longest dimension, whereas sieves tend to segregate needles according to their shortest dimension.

The particles comprising inorganic solid preferably comprise a builder, an effervescible mixture, a pesticide or a sterilant. The surfactant preferably consists essentially of non-ionic and amphoteric surfactant. The powder preferably comprises a mixture of surfactants consisting essentially of amphoteric and non-ionic surfactants.

According to a second embodiment the invention provides a powder comprising a solid particulate mixture, which is capable of effervescing on contact with water, and a solid, amphoteric surfactant said surfactant containing less than 10% of moisture, based on the weight of said surfactant, and preferably less than 12% sodium chloride. The solid particulate mixture, which is capable of effervescing in water, is preferably a mixture of sodium bicarbonate and citric acid.

According to a third embodiment, the invention provides a powder comprising: (A) non-hygroscopic particles consisting of at least 80%, preferably at least 90%, by weight of amphoteric surfactant; and (B) water soluble and/or water swellable particles comprising inorganic solids and/or polymers; all said particles, preferably, having a mean particle size between 400μ and 4mm,and less than 5% by weight passing a 250μ sieve.

According to a fourth embodiment, the invention provides a powder comprising a non-ionic surfactant and a solid, particulate builder characterised in that said powder additionally comprises a solid, particulate amphoteric surfactant and a smectite clay. According to a fifth embodiment, the invention provides a powder comprising a solid amphoteric surfactant, a liquid non-ionic surfactant and inorganic solid particles, capable of adsorbing or absorbing at least part of said non-ionic surfactant, characterised in that at least part of said non-ionic surfactant is premixed with at least part of said solid particles.

According to a sixth embodiment, the invention provides a tablet, or region of a tablet, made by compacting a powder of the invention.

It is conventional to use a spray-, or fluid bed-, dried base powder, containing surfactant and other components, as the basis for laundry tablets. However, we have discovered that, using amphoteric surfactants according to the present invention it is possible to include all the amphoteric surfactant in the binder and even to dry mix all the ingredients, saving on drying costs. We strongly prefer to manufacture by dry- mixing.

A seventh embodiment of our invention therefore provides a method of preparing a laundry detergent which comprises blending together particles of a solid amphoteric surfactant containing less than 12% moisture based on the weight thereof and solid particles of builder and preferably compacting the blend to form a tablet.

According to an eighth embodiment the invention provides a method of making a unit dose cleaning tablet comprising surfactant, which comprises the steps of (1) blending a spray dried or granulated base powder comprising at least sufficient inorganic solids to provide a free flowing powder, and optionally part of said surfactant, with a binder comprising at least part of said surfactant, to form a substantially solid blend and (2) compacting said blend to form said tablet, characterised in that said surfactant consists essentially of non-ionic and amphoteric surfactant and that said binder comprises at least part of said amphoteric surfactant, said part of said amphoteric surfactant preferably containing less than 10% moisture and, preferably, less than 12% of sodium chloride, based on the weight thereof. According to a ninth embodiment, the invention provides a method of preparing a detergent powder, which comprises mixing together: a solid, amphoteric surfactant; a liquid, non-ionic surfactant; and a particulate, inorganic solid, 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 inorganic solid to form a solid, particulate premix comprising particles of said inorganic solid having said non-ionic surfactant adsorbed thereon or absorbed therein, said premix is mixed with said solid 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.

Preferably said premix comprises particles of clay. Preferably said mixture contains particles comprising builders, diluents, water-swellable polymers and/or wash adjuvants. The premixed non-ionic surfactant, and any non-ionic surfactant added subsequently to the mixture, may be the same or different.

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%, usually less than 2%, often less than 1%, ideally less than 0.5%.

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. 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 nitrilo triacetate, 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, Upases 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, such as bentonite or ditallowyl betaines; perfumes; preservatives; pigments; dyes and/or polymers.

In the case of bath bombs the surfactant may be as little as 0.25%, preferably more than 0.5%, most preferably more than 1% of the total weight of the tablet. It is preferably less than 5%, more preferably less than 3%, most preferably less than 2%, by weight, of the bath bomb. However for most other applications the surfactant generally constitutes more than 2%, preferably more than 5%, more preferably more than 9%, most preferably more than 10%, sometimes more than 20% and in certain cases more than 30%, or even more than 40%, of the total weight of the tablet. Usually the total proportion of surfactant is less than 60%, generally less than 50%, and for most purposes less than 40%, preferably less than 30%, more preferably less than 20%, often less than 15%, based on the total weight of the tablet.

For laundry applications the surfactant preferably comprises non-ionic surfactant, and in particular, 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, e.g. 2 to 50, especially 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, most preferably greater than 10.5, usually greater than 10.5, e.g. greater than 11, but less thanlό, preferably less than 15, more preferably less than 14, e.g. 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%, most preferably more than 40%, typically more than 50%, often more than 60% and sometimes more than 70%, by weight of the total surfactant. Preferably 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: Pv ¹ ₂N⁺CH₂COO^", wherein R is an aliphatic hydrocarbyl, hydrocarbyl amido alkyl or hydrocarbyl ether group having an average of from 8 to 30, e.g. 10 to 25, especially 15 to 25 aliphatic carbon atoms and R¹ 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.(R¹)₂N⁺CH₂COO^"; where R² is a C₈-25 , preferably C_12-2o, alkyl group, n is from 2 to 4, and R¹ 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 is 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 ampho acetates, and traditionally ascribed the formula:

CH₂ CH₂

N *N — CH₂COO^"

X

R¹

R

although they are actually present, at least predominantly, as the corresponding linear amido amine

RCONH CH₂ CH2 N R¹

I

which is usually obtained commercially in admixture with the dicarboxymethylated form

RCONH CHz C^ R¹

I I

wherein R is an aliphatic group having from 8 to 25 carbon and R¹ is 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, N-alkyl sarcosines, carboxylated amido amines such as RCONH(CH₂)_nN⁺ 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.

The sodium chloride content of the solid amphoteric surfactant is preferably less than 12% by weight of said amphoteric surfactant, usually less than 10%, more preferably less than 8%, most preferably less than 5%, especially less than 3%, e.g. less than 1%.

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

The solid amphoteric surfactant is preferably substantially anhydrous. By this is meant a moisture content less than 12% more preferably less than 10%, most preferably less than 8%, e.g. 1 to 6% by weight of said amphoteric surfactant.

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

We prefer that the 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%, more preferably less than 8% at 40°C in an atmosphere having 65% humidity.

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

Where a base powder containing amphoteric surfactant is used, the proportion of the total amphoteric surfactant in the laundry tablet which is added separately from the base powder is preferably at least 20% by weight, more preferably at least 30%, most preferably at least 40%, usually at least 50%, desirably at least 60% more desirably at least 70%, most desirably at least 80%, e.g. more than 90%.

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

In the case of bath bombs the amphoteric surfactant may be used in conjunction with anionic surfactants and in particular high foaming anionic surfactants such alkyl sulphates or alkyl ether sulphates. The proportion of amphoteric surfactant may be from 20 to 100% preferably 30 to 70% by weight of the total surfactant.

Where a spray dried base powder is included in the formulation, the base powder preferably comprises a builder, which may for example comprise sodium tripolyphosphate, zeolite, sodium carbonate, sodium silicate, potassium pyrophosphate and/or sodium citrate. It preferably comprises conventional components of spray dried laundry detergent powders e.g. stain removers such as aminomethylene phosphonates, enzymes or oxidising bleaches, antiredeposition agents such as sodium carboxymethyl cellulose, optical brightening agents, perfume and colouring.

The inorganic content of the base powder is preferably at least 30% based on the total weight thereof, more preferably at least 40% most preferably at least 50%, e.g. 60 to 90%.

The blended solids may comprise, in addition to the solid amphoteric surfactant, and any base powder, builders such as tetra potassium pyrophosphate, high phase 1 sodium tripolyphosphate, or zeolite, water-swellable polymers, such as water- swellable polyacrylates and any of the conventional wash adjuvants, all of which may be included in proportions conventional for laundry tablets.

The total proportion of builder in the powder, or in the laundry tablet, for example, may be greater than 10%, preferably greater than 15%, more preferably greater than 20%, most preferably greater than 30%, usually greater than 40%, sometimes 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 tablet may comprise binders in addition to the solid amphoteric surfactant. For example any surfactant in the base powder will contribute to the binding effect, as will any citric acid / bicarbonate mixtures. The latter are conventionally compacted with a small amount of water, which gives a cementing effect. Alternatively or additionally there may be a polymeric binder present. Any liquid ingredients such as non-ionic surfactant may be sprayed on to the tablet or the mixture from which it is compacted, or onto porous particles added to the mixture

We have found that smectite clays, such as bentonite or montmorillonite, provide amphoteric-based tablets with greatly increased compression strength combined with rapid disintegrability and dispersability. We prefer that the clay, and also, desirably the other components of the tablet should have a mean particle size, and preferably also at least the majority of particles, greater than 250μ, e.g. greater than 300μ, more preferably greater than 350μ, most preferably greater than 400μ, typically greater than 450μ, especially greater than 500μ.

It is preferred that the mean particle size of the clay, and preferably also the size of at least the majority of the particles in the composition, be less than 2 mm, more preferably less than 1.5 mm, most preferably less than 1mm.

We prefer that the clay, and preferably the powder composition as a whole, should contain less than 10%, by weight, more preferably less than 5%, by weight, most preferably less than 3%, by weight, especially less than 2%, by weight, most desirably less than 1%, by weight, of particles smaller than 250μ

We prefer that the clay be used as the carrier for at least part of the non-ionic surfactant, and more preferably, at least the major part. The non-ionic surfactant is preferably sprayed onto the clay to form a premix prior to blending with the other components.

The clay may be present in a proportion of greater than 2%, preferably greater than 5%, more preferably greater than 6%, most preferably greater than 7%, especially greater than 8%, e.g. greater than 9%, 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 18%, most preferably less than 16%, e.g. less than 15%, by weight based on the total weight of the powder.

The proportion of non-ionic surfactant used to make the premix is preferably at least 30%, more preferably at least 40%, most preferably at least 50%, desirably at least 60%, more desirably at least 70%, most desirably over 75%, e.g. over 80%, of the total non-ionic surfactant in the powder. 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 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 solid 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 binders, such as bentonite, 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, the amphoteric surfactant had a mean particle size of 1.3 mm and the other solid components had a mean particle size between 600 and 700μ, and less than 1% by weight smaller than 250μ, unless the contrary is indicated.

Example 1

A base powder was prepared by spray drying an aqueous slurry. The base powder consisted of :- wt %

C i2-i4 alcohol 3 mole ethoxylate 3.5

C12-₁₄ alcohol 8 mole ethoxylate 3.5

Perfume 0.1

Sodium carbonate 10.0

Sodium perborate 16.0

C12-14 alkyl betaine 2.0

Sodium diethylentriamine pentakis (methylene phosphonate) 0.26

Silicone antifoam 0.6

Low phase 1 sodium tripolyphosphate 20.0

Sodium silicate 4.0

Sodium carboxymethyl cellulose 0.7

Sodium sulphate 32.4

Optical brightening agent 0.16 water balance

Three samples of the base powder were blended with solid particles comprising respectively three different samples of Cι_2-ι₄ alkylamidopropyl betaine. The total composition consisted of :-

Spray dried base powder 51.5

High phase 1 sodium tripolyphosphate 30.0

Zeolite 2.0

Ci2-i4 alcohol 3 mole ethoxylate 1.75

C12-14 alcohol 8 mole ethoxylate 1.75

Water-swellable polyacrylate 0.5

C12 alkyl amidopropyl betaine 2.5 The three amidopropyl betaines were all prepared from narrow cut (>80% C12), hardened, coconut feedstocks and had the following characteristics :

A. Desalted (less than 1% sodium chloride); dried (less than 0.5% moisture); particle size less than 150 microns.

B. Undesalted (ca 18% sodium chloride); dried (less than 0.5% moisture); particles size less than 150 microns.

C. Desalted (less than 1% sodium chloride); partially dried (2% moisture); particle size 250 -1400 microns.

The samples were compacted into tablets each weighting 35g by applying a pressure of 15kN. The tablets all had a compression strength of 41+4N.

The disintegration of the tables was measured by placing them in a net, which was firstly immersed in tap water (22°C) for 15 sees, then re-immersed 10 times over the next 15 sees, and finally held out of the water for 15 sees. This cycles was repeated

until the tablet had completely disintegrated and passed through the net. The measurement was repeated after one month's storage under laboratory ambient conditions. The number of cycles required for each formulation to disappear from the net was as follows:-

Tablet Age l day 1 month

A 10 cycles 8 cycles

B 16 cycles 20 cycles

C 8 cycles 4 cycles

The results indicate significantly faster disintegration times for the low salt betaine products. Example 2

A conventional (comparative) anionic tablet had the following composition: wt %

Low phase 1 sodium tripolyphosphate 6.7

Sodium silicate 1.6

Sodium carboxymethyl cellulose 0.28

Optical brightening agent 0.05

Sodium sulphate 10.0

Sodium carbonate 2.2

Sodium toluene sulphonate 0.9

Sodium perborate tetrahydrate 12.8

Tetracetyl ethylene diamine 3.0

Silicone antifoam 0.2

High phase 1 sodium tripolyphosphate 40.0

Water-swellable polyacrylate 1.0

Water-swellable sodium carboxymethyl cellulose 2.0

Anionic / nonionic surfactant 15%

Water balance

The surfactant comprised :- wt % Sodium Ci₀.i₂ linear alkyl benzene sulphonate 9

Sodium C12-₁ alkyl sulphate 2

C12-14 alkyl 3 mole ethoxylate 2

C12-14 alkyl 8 mole ethoxylate 2

A formulation according to the invention was prepared comprising the same ingredients in the same relative proportions, but replacing the 15% anionic/non-ionic surfactant with 10.15% of nonionic/amphoteric surfactant having the composition in % by weight based on the total composition of

C12-14 alkyl betaine 0.65

Alkyl amido propyl betaine C 3

C 12-14 alkyl 3 mole ethoxylate 3.25

C12-14 alkyl 8 mole ethoxylate 3.25

40, 35 and 30g tablets of each formulation were prepared and compared for washing effectiveness in a washing machine at 40°C using 7.5 1 of 200ppm hardness water with 1 tablet placed in a dispenser net in the drum. Average % soil removal from a range of test swatches was measured.

Dosage Cotton PE/Cot Polyester AV. Overall

Comparative 40g ^' _. 52.3 46.8 71.0 53.6

(Anionic) 35g 54.2 45.0 71.0 54.0

30g 50.8 41.0 65.5 50.0

Example 2 40g 56.3 55.0 73.5 58.8

35g 56.3 55.8 77.0 59.6

30g 55.3 52.3 73.0 57.2

The non-ionic / amphoteric tablet of the invention out-performed the conventional anionic/nonionic tablet at all doses. The 30g tablet of the invention out-performed the 40g conventional tablet. Example 3

A bath bomb was prepared from a mixture of equal weights of citric acid and sodium bicarbonate. The mixture was added to the tableting press in three equal layers. The mixture used to make the middle layer contained 2%, by weight of the mixture, of the surfactant C from Example 1 and 2% of sodium lauryl sulphate.

Example 4

The following powder formulation was prepared by mixing the solid components and spraying the non-ionic surfactant onto the mixed solids:

A 35 g tablet compressed under 30kN pressure had a compression-strength of 24N and a disintegration time of 30 seconds.

Example 5

The process of Example 4 was repeated substituting 9.4% of bentonite, based on the total weight of powder for an equal weight of the sodium sulphate, and premixing the non-ionic surfactant with the bentonite. The resulting tablet had a compression- strength of 107N and a disintegration time of 26 seconds. Example 6

The powder of Example 5 tended to segregate. Example 5 was repeated, premixing 4% of the non-ionic surfactant, based on the total weight of the powder, and post- adding the remaining 1.4%. No segregation was observed and the compacted tablet had a compression-strength of 40N and disintegration time of 25 seconds.

Example 7

A herbicidal composition was prepared by blending 70%, by weight, of the isopropylamine salt of glyphosate, 10%, by weight, of a dried and desalted lauryl amidopropyl betaine, 10%, by weight, of sodium capryl (6 mole ethoxy) methyl carboxylate and 10%, by weight, of bentonite. The powder was compressed to form a strong, rapidly soluble tablet.

Example 8

A laundry detergent tablet was prepared by compacting a powder consisting of:

Claims

CLAΓMS

1. A powder capable of compaction into tablets, which is formed by blending a solid surfactant with water-swellable and/or water soluble particles comprising inorganic solids and/or polymers, characterised in that the solid surfactant comprises particles consisting essentially of amphoteric surfactant.

2. A powder according to claim 1, wherein the particles of amphoteric surfactant have a moisture content less than 12%, by weight thereof.

3. A powder according to claim 2, wherein the particles of amphoteric surfactant have a moisture content less than 10%, by weight thereof.

4. A powder according to any preceding claim comprising a solid particulate mixture, which is capable of effervescing on contact with water, and a solid, amphoteric surfactant said surfactant containing less than 10% of moisture, based on the weight of said surfactant, and preferably less than 12% sodium chloride.

5. A powder according to claim 4, characterised in that the solid particulate mixture is a mixture of sodium bicarbonate and citric acid.

6. A powder according to any foregoing claim, characterised in that the particles of amphoteric surfactant are non-hygroscopic particles consisting of at least 90% by weight of amphoteric surfactant.

7. A powder according to any foregoing claim, characterised in that said powder has a mean particle size between 300μ and 2mm, and less than 5% by weight passing a 250μ sieve.

8. A powder comprising a solid, particulate amphoteric surfactant and a smectite clay.

9. A powder according to any foregoing claim, also comprising a non-ionic surfactant and a solid, particulate builder.

10. A powder comprising a solid amphoteric surfactant, a liquid non-ionic surfactant and inorganic solid particles, capable of adsorbing or absorbing at least part of said non-ionic surfactant, characterised in that at least part of said non-ionic surfactant is premixed with at least part of said solid particles.

11. A tablet, or region of a tablet, formed by compacting a powder according to any foregoing claim.

12. A method of making a unit dose cleaning tablet comprising surfactant, which comprises the steps of (1) blending a spray dried or granulated base powder comprising at least sufficient inorganic solids to provide a free flowing powder, and optionally part of said surfactant, with a binder comprising at least part of said surfactant, to form a substantially solid blend and (2) compacting said blend to form said tablet, characterised in that said surfactant consists essentially of non-ionic and amphoteric surfactant and that said binder comprises at least part of said amphoteric surfactant, said part of said amphoteric surfactant preferably containing less than 10% moisture and, preferably, less than 12% of sodium chloride, based on the weight thereof.

13. A method of preparing a laundry detergent, which comprises blending together particles consisting essentially of a solid amphoteric surfactant and solid particles of a builder.

14. A method according to claim 13, which additionally comprises compacting the blend to form a tablet.

15. A method of preparing a detergent powder, which comprises mixing together: a solid, amphoteric surfactant; a liquid, non-ionic surfactant; and a particulate, inorganic solid, 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 inorganic solid to form a solid, particulate premix comprising particles of said inorganic solid having said non-ionic surfactant adsorbed thereon or absorbed therein, said premix is mixed with said solid 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.

16. A method according to claim 15 characterised in that, said premix comprises particles of clay.

17. A method according to claim 16 characterised in that, said mixture contains particles comprising builders, diluents, water-swellable polymers and/or wash adjuvants.