WO2002050240A1

WO2002050240A1 - Washing device

Info

Publication number: WO2002050240A1
Application number: PCT/EP2001/014266
Authority: WO
Inventors: Jelles Vincent Boskamp; Mirjam Sta
Original assignee: Hindustan Lever Ltd; Unilever NV
Current assignee: Hindustan Unilever Ltd; Unilever NV
Priority date: 2000-12-20
Filing date: 2001-11-30
Publication date: 2002-06-27
Anticipated expiration: 2003-06-20
Also published as: AU2002227988A1

Abstract

A washing device comprising at least one tablet of compacted particulate cleaning composition in a water soluble pack comprising; (i) at least one part of high water solubility, and (ii) at least one part of medium water solubility, wherein the at least one part of medium water-solubility has a solubilisation time in water at 20 °C of at least 60 seconds more than that of the at least one part of high water solubility and forms a structure capable of enclosing the tablet(s) after solubilisation of the high water solubility part. A packaging film, pack, method of laundering fabrics and a method of producing a washing device are also provided. The invention provides for the dosing of cleaning tablets with a dispensing device but without the disadvantages associated with using conventional dispensing devices such as a net made of fabric.

Description

Washing device

This invention relates to a washing device comprising cleaning compositions in the form of tablets. The tablets may be suitable for use in machine dishwashing, the washing of fabrics or other cleaning tasks.

Detergent compositions in tablet form and intended for fabric washing have been described in a number of patent documents including, for example EP-A-711827, WO-98/42817 and WO-99/20730 (Unilever) and are now sold commercially. Tablets containing bleach for use as an additive to a fabric washing liquor have been disclosed in US-A-4013581 (Huber/Procter and Gamble) . Tablets containing a water-softening agent, for use as an additive in cleaning, are sold commercially and are one form of tablet disclosed in EP-A-838519 (Unilever) . Tablets of composition suitable for machine dishwashing have been disclosed in EP-A-318204 and US-A-5691293 and are sold commercially.

Tablets have several advantages over powdered products : they do not require measuring and are thus easier to handle and dispense into the wash-load, and they are more compact, hence facilitating more economical storage.

Dispensing devices for detergent tablet compositions are known. For example EP-A-576 234 discloses a dispensing device for laundry treatment tablets comprising a sleeve of elastic material which is stretched against its elasticity and conforms tightly to the tablets and which has apertures which are sufficiently large to allow water to flow therethrough. WO98/40550 describes a process for washing laundry employing a receptacle for tablets wherein the receptacle is a loosely fitting net bag having apertures with an average mesh size between 1 and 10 mm.

The use of the above re-usable receptacles has the disadvantage that prior to the washing process it requires a multi-step process to remove the tablets from their packaging material and then to insert the tablets into the receptacle. Furthermore the use of these receptacles has the disadvantage that after the washing cycle has been completed the receptacle needs to be found and removed from the laundry.

The present invention aims to provide a convenient way of packaging cleaning tablets wherein preferably one or more of the above mentioned problems are addressed.

According to a first aspect of the invention, there is provided a washing device comprising at least one tablet of compacted particulate cleaning composition in a water soluble pack, wherein the pack comprises;

(i) at least one part of high water solubility, and (ii) at least one part of medium water solubility, and further wherein the at least one part of medium water- solubility has a solubilisation time in water at 20°C of at least 60 seconds more than the solubilisation time of the at least one part of high water solubility and forms a structure capable of enclosing the at least one tablet after solubilisation of the at least one part of high water solubility.

According to a second aspect of the invention there is provided a water soluble packaging material suitable for packaging one or more cleaning tablets to form a washing device wherein the packaging material comprises; (i) at least one part of high water solubility, and

(ii) at least one part of medium water solubility, and further wherein the at least one part of medium water- solubility has a solubilisation time in water at 20°C of at least 60 seconds more than the solubilisation time of the at least one part of high water solubility and forms a structure capable of enclosing the at least one tablet after solubilisation of the at least one part of high water solubility.

According to a third aspect there is provided a water soluble pack for at least one tablet of compacted particulate cleaning composition wherein the pack comprises; (i) at least one part of high water solubility, and (ii) at least one part of medium water solubility, and further wherein the at least one part of medium water- solubility has a solubilisation time in water at 20°C of at least 60 seconds more than the solubilisation time of the at least one part of high water solubility and forms a structure capable of enclosing the at least one tablet after solubilisation of the at least one part of high water solubility.

According to a fourth aspect there is provided a method of laundering fabrics wherein said method comprises the step of contacting the fabrics in the presence of water with a washing device comprising at least one tablet of compacted particulate cleaning composition in a water soluble pack and wherein the pack comprises;

According to a fifth aspect there is provided a method of producing a washing device comprising at least one tablet of compacted particulate cleaning composition in a water soluble pack wherein said method comprises the step of placing the at least one tablet in a water soluble pack comprising: (i) at least one part of high water solubility, and (ii) at least one part of medium water solubility, and further wherein the at least one part of medium water- solubility has a solubilisation time in water at 20°C of at least 60 seconds more than the solubilisation time of the at least one part of high water solubility and forms a structure capable of enclosing the at least one tablet after solubilisation of the at least one part of high water solubility.

The terms 'high water solubility' and 'medium water solubility' as used herein refer to the relative times taken for these two parts of the pack to solubilise. It is not an absolute measure of solubility in water. A 'high water solubility' part of the pack solubilises in water in a shorter time than does a 'medium water solubility' part. This slower solubilisation time of the 'medium water solubility' part may be bought about, for example, by varying the thickness of the pack or the composition of the material used to form it, or it may have a slower rate of solubilisation in water at the temperature of use. Preferably the pack is sealed after the at least one tablet is placed therein.

Preferably the pack is a flexible enclosure for the tablets such as a sachet or bag. Especially preferred are loosely fitted packs; especially suitable are flow wrapped packs. The packs may be closed and enclose one or more tablets (e.g. sealed or otherwise closed) . Alternatively the packs may be empty or filled with one or more tablets and be re-openable (e.g. for inserting one or more tablets into the pack).

Preferably a pack is used wherein the part of high water solubility dissolves in the wash water prior to substantial disintegration or dissolution of the cleaning tablet and the part of medium water solubility dissolves after the substantial disintegration or dissolution of the cleaning tablets.

In a preferred embodiment the part of the pack which is of high water solubility comprises, or is composed of, several discrete elements or areas which after they have dissolved provide apertures in the pack. These apertures are preferably permeable for water and for solubilised or disintegrated cleaning composition but are preferably too small to allow the passage therethrough of substantially whole tablets.

Preferably the pack comprises a substantially continuous pattern of medium water solubility with discrete areas of high water solubility interspersed throughout the pattern. The pattern is preferably a grid-like pattern. For example,

It is especially preferred that after the part of the pack which is of high water solubility has dissolved a net-like structure remains (which is of medium water solubility) and which is capable of enclosing and retaining the tablets until the tablets have themselves substantially disintegrated.

For the avoidance of doubt, the term 'net' as used herein includes a web-type structure having a substantially continuous network or grid pattern with apertures formed between the network or grid.

In a preferred embodiment the pack comprises, or is composed of, a film material comprising discrete regions of high water solubility material and a continuous pattern of material of medium water solubility.

In another preferred embodiment the pack comprises, or is made of, a film of high water solubility to which is applied a continuous pattern of material such that those parts of the film to which the continuous pattern has been applied are of medium water solubility in the pack. For example a continuous pattern of a high water solublity material is applied to a film of the same material and the resulting film is used to produce the pack. The parts of the pack that comprise the high water solublity material both as the film and the continuous pattern applied thereon are of medium water solubility and the parts of the pack that comprise the high water solublity material as the film only are of high water solubility.

In another preferred embodiment the pack comprises, or is made of, an inner layer or film of medium water solubility which forms an open continuous structure (e.g. a net-like structure) capable of retaining the tablet, the inner layer or film being enclosed by an outer layer or film of high water-solubility. DE 19941480 (published 08 March 2001) discloses water soluble sachets for detergent compositions which when in contact with a suitable solvent forms pores in the sachet to allow the ingress of water.

The use of water soluble packs for detergent compositions has been disclosed, for example, in EP-A-479 404 which describes a sachet or bag containing a cleaning composition where the sachet or bag is made from a water soluble continuous base film material with a second less soluble plastic material present as a discontinuous layer thereon. The discontinuous layer is effective to prevent wet tack.

EP-A-1 072 675 describes a detergent product in packaging which has a high resistance to moisture but a major part of which is dispersible in a solvent. The package comprises a hydrophilic material and a hydrophobic material.

EP-A-253 566 describes a laundry product which comprises a particulate laundry composition releasably contained within a sachet formed of a film of water-soluble material, the film having an outer covering of a flexible, apertured, water- insoluble but water permeable non-woven, textile or paper sheet material .

EP-A-337 568 describes detergent sachets for laundry which sachets comprise readily water dispersible water soluble cellulose and cellulose fibers coated with water soluble PNA.

WO 00/04125 describes a detergent composition in a bag made from a water-soluble film. Sachets comprising non-laundry preparations are also known, for example, US 5 780 418 which discloses a granular bathing agent packed in a non woven or woven sachet .

Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about." All amounts are by weight, unless otherwise specified.

Pack material

Water soluble packaging materials suitable for producing the pack according to the invention are widely disclosed in the literature. Preferably the water soluble pack comprises one or more water soluble polymers Suitable polymers include for example polyester amides, polyvinyl alcohol, co-polymers of vinyl alcohol and methacrylate, polyethylene oxide, alginates, cellulose ethers such as carboxymethyl celluloses and methylcelluloses (for example, hydroxy alkyl methylcelluloses such as hydroxy ethyl methylcellulose, hydroxy butyl methylcellulose and hydroxy propyl methylcellulose) , water soluble starch derivatives, gelatin and combinations thereof.

The desired degree of solubility of the pack, or a part thereof, can be achieved by selection of the type of packaging material and/or its thickness. Thus in one embodiment a single material may be used to form the pack and the differences in water solubility for different parts of the pack are achieved by varying the thickness of that material in the different parts. In another embodiment, the differences in water solubility are achieved by using two or more different materials . For example a pack made from a thin polyethylene oxide film having applied to its surface a grid-like pattern of further polyethylene oxide will have a relatively short solubilisation time for those parts of the pack formed only from the film (which when dissolved form apertures in the remaining grid-like structure) and a longer solubilisation time those parts of the pack formed from film to which the grid-like pattern has been applied.

The pack material may comprise a plasticiser. Suitable plasticisers include polyethylene glycols such as PEG 200 (molecular weight) .

It is well within the ability of the skilled person to select (combinations of) packaging materials and/or thickness of the pack so that the desired level of water solubility is achieved.

One preferred combination of materials to be used in the pack is polyvinylalcohol and methyl celluloses such as hydroxy alkyl methylcelluloses such as hydroxy ethyl methylcellulose, hydroxy butyl methylcellulose and hydroxy propyl methylcellulose.

Pack form

In a preferred embodiment the pack is a sachet or bag enclosing one or more cleaning tablets .

Preferably the pack loosely fits around the tablet (s). Preferably the pack is closed e.g. by sealing. For some embodiments however the pack may be re-openable and this is especially advantageous if the number of tablets per cleaning operation can be varied. In a preferred embodiment the pack is a flow-wrapper pack.

In a preferred embodiment the part of the pack which is of high water solubility is composed of several discrete elements (or regions) which after they have dissolved leave apertures in the pack which are preferably permeable to water and to dissolved or disintegrated parts of the cleaning tablet. However, the apertures are preferably too small to allow passage of the substantially whole tablets therethrough. For example, the pack may comprise a continuous matrix of medium water solubility having, for example, the form of a grid-like pattern. The parts of the pack between this matrix, for example forming discrete inner spaces of the grid-like pattern, have a high water solubility.

In a preferred embodiment the pack comprises a film, the film comprising discrete regions of high water solubility and a continuous pattern of medium water solubility.

Upon immersing the pack in water, the discrete parts of the pack having high water solubility will dissolve first at which time the remaining part of the pack (the matrix) will not yet be substantially dissolved.

In another preferred embodiment the pack comprises a film of high water solubility to which is applied thereto a continuous pattern of a material (of the same or lesser solubility in water) such that parts of the film to which the continuous pattern has been applied are of medium water solubility. Upon immersing the pack in water the parts of the film to which no additional (continuous) material has been applied will dissolve first whereafter the continuous medium water solubility part (matrix) will remain until dissolved itself. For both of these embodiments the arrangement of the medium water solubility part of the pack is chosen such that this part (after solubilisation of the high water solubility part) is capable of enclosing and retaining the cleaning tablets for a desired period of time.

For example, if the medium water solubility part of the pack is of a grid-like pattern, this will form a water soluble net comprising apertures which is capable of enclosing and retaining the tablets upon solubilisation of the high water solubility part of the pack. However the apertures so formed between the remaining grid should be sufficiently large (open enough) to allow the passage of water and transfer of the tablet material once disintegrated into small enough pieces or once dissolved.

Preferably the shape of the medium water solubility part of the pack (or material) is chosen such that it forms a net shaped pack capable of retaining the tablets while they are substantially intact. The apertures in such a net can vary in size and may, for example, have an average size in the range of from 0.5 to 100mm², more preferred from 0.7 to 25mm², most preferred from 1 to 15mm².

By varying the type of material and/or the thickness (diameter) of the pack the strength of the net can be adapted such that it is strong enough to enclose and retain the tablets preferably for a period sufficient to allow the substantial disintegration or dissolution of the tablets.

Preferably when the high water solubility part of the pack dissolves on average of from 10 to 90%, more preferably of from 30 to 70%, even more preferably of from 35 to 65% of the original surface area of the pack is constituted by apertures.

For example, when a net is formed, preferably 10 to 90% of the surface area of the net is constituted by apertures, more preferably 30 to 70%.

In another preferred embodiment the pack comprises an inner layer of material which is of medium water solubility and which forms an open continuous structure capable of retaining the at least one tablet (for example a net-like structure as described above) and wherein the inner layer is enclosed in an outer film of high water-solubility.

The water soluble material used to form the pack may be a film material, which can be of substantially uniform material or of non-woven texture. Non-woven films are preferred for bleach containing tablets because oxygen gas formed on storage of the tablets can escape through the small apertures in the non-woven film.

Substantially uniform PVA film can for example be purchased from Chris Craft, Chicago, U.S.A., reference CC8534, and thermally non woven PVA fabric from BFF Nonwovens, Bridgewater, U.K., product name SOLUFAB HEN30.

The parts of the pack which form a grid like pattern and which are of medium water solubility can, for example, be produced by the application of pressure, heat, ultrasonics or a combination of these.

The water soluble film preferably is mainly composed of poly vinyl alcohol (PVA) or of a co-polymer of poly vinyl alcohol and poly methyl acrylate (PVA-PMA) . The term poly vinyl alcohol as used herein also includes partially hydrolysed poly vinyl acetates. The water soluble film can also contain minor quantities of plasticizers, antifoams, anti-oxidants, surfactants, perfumes and the like.

The exterior surface of the film may be treated with BITREX™ to discourage ingestion of the package of the invention by children.

The thickness of the high water solubility part of the pack will generally depend on the type of material used but will usually be in the range of from 10 to lOOOμm, preferably 20 to 80μm, most preferably 40 to βOμm. The thickness of the medium water solubility part of the pack will generally also be in these ranges. If the pack is made of a single type of material the thickness of the high water solubility part of the pack will be less than the thickness of the medium water solubility part of the pack. For example the high water solubility part of the pack may have a thickness in the range of from 25 to 55μm and the medium water solubility part of the pack may have a thickness in the range of from 65 to 500μm, preferably 70 to 200μm.

The application of energy to a part or all of the pack or film generally reduces the water solubility thereof. The energy can be applied in the form of heat, pressure, ultrasonics or a combination thereof. Therefore the application of energy to selected parts can provide the desired pattern on high water solubility areas (to which no or only a limited amount of energy is applied) and on medium water solubility areas (to which the energy is applied) . Examples of preferred methods to prepare the desired combination of high water solubility areas and medium water solubility areas in accordance to the inventions are:

• the local application of energy to (parts of) a high water solubility film; or by

• sealing onto a high water solubility film one or more films (e.g. of the same material) to generate a grid-like structure on the original film by the application of energy; or by

• sealing onto a high water solubility film one or more films, (e.g. of the same material) which contain apertures ranging from 0.5 to 100 square mm²; or by

• superposition of a high water solubility film with a gridlike structure such that windows of a high water solubility film of 0.5 to 100 mm² are alternated with medium water solubility material.

Upon immersing the pack in water the continuous outer film of high water solubility will quickly solubilise whereafter the material of medium water solubility will enclose the tablet (s) preferably until they are substantially disintegrated or solubilised.

The pack may be of any suitable shape and construction. The most convenient shapes from the viewpoints of both manufacture and packing are square and rectangular, but any other desired shape is also within the scope of the invention.

Test for measuring solubility.

A pack in accordance to the invention can suitably be tested by placing the pack on a gauze with square openings of 1 cm size each and submerging the pack in a beaker containing 1 litre of tap-water at a temperature of 20°C. The solubilisation of the pack is visually monitored over time and the solubilisation time is the time period by which the entire (part of the) packaging material is solubilised. In this context however it should be noted that sometimes on immersion in water the film may not show homogeneous solubilisation. Some parts may dissolve faster than other parts. Also, during the solubilisation process the film may rupture. For the purpose of this invention however the solubilisation time is the time at which substantially all of the relevant part of the pack are solubilised. In case of substantial inaccuracies in determining the solubilisation time, the measurement should preferably be repeated e.g. 5 to 10 times so that an average solubilisation time can be calculated.

The weight of the tablet on the gauze is measured as a function of time until the tablet has completely disintegrated and fallen through the openings in the pack and gauze.

The part of the pack which is of high water solubility preferably has a solubilisation time in water of 20°C of less than 300 seconds, more preferably less than 200 or 180 seconds, most preferably less than 60 seconds.

The tablets are preferably at least 90 wt% disintegrated and fallen through the opening in the pack before the medium water solubility part of the pack is solubilised.

For example, if a pack consists of a film containing alternating discrete areas of high water solubility film and a grid-like pattern of medium water solubility, the high water solubility part solubilises in about 20 seconds in water at 20°C and 90 wt% of the tablet disintegrates and falls through apertures in the pack within 120 seconds, then preferably the medium water solubility part of the pack should have a solubilisation time in excess of 140 seconds.

Alternatively if the pack consists of an inner grid like film of medium water solubility enclosed in an outer wrapper of high water solubility material, the high water solubility material solubilises in 20 seconds and 90 wt% of the tablet disintegrates and falls through apertures produced in the pack within 120 seconds, then preferably the part of the pack of medium water solubility should have a solubilisation time in excess of 140 seconds.

For most practical applications it is preferred that the part of the pack which is of medium water solubility has a solubilisation time in water at 20°C of at least 120 seconds more than the solubilisation time of the high water solubility part of the pack, more preferred at least 300 seconds more. Hence if the solubilisation time of the high water solubility part of the pack is 100 seconds, then the medium water solubility part has a solubilisation time of at least 160 seconds, more preferably at least 220 seconds, most preferably at least 400 seconds.

The solubility of the pack should however be such that the pack is solubilised before the end of a normal wash cycle such that the solubilised material is normally removed from the washing machine prior to rinsing. Generally therefore the part of the pack which is of medium water solubility preferably has a solubilisation time in water of 20°C of less than 1800 seconds, more preferably less than 1200 seconds, most preferably less than 600 seconds. Tablet composition

This invention is particularly applicable to cleaning tablets which comprise both surfactant and detergency builder e.g. tablets for fabric washing and machine dishwashing.

Cleaning tablets for use in the present invention generally have a weight of from 2 to 200g, more preferably of from 20 to lOOg, most preferably of from 30 to 80g. Preferably 1 to 500 tablets are enclosed in the pack, more preferably 1 to 10 or 20, most preferably 1 to 5, especially 1, 2 or 3.

Surfactant compounds

The tablets of the invention typically comprise one or more organic surfactants. Many suitable detergent-active compounds are available and are fully described in the literature, for example, in "Surface-Active Agents and Detergents", Volumes I and II, by Schwartz, Perry and Berch.

The surfactant may be anionic (soap or non-soap) , cationic, zwitterionic, amphoteric, nonionic or a combination of these. The preferred detergent-active compounds that can be used are soaps and synthetic non-soap anionic and nonionic compounds.

Anionic surfactant may be present in an amount from 0.5 to 50% by weight, preferably from 2% or 4% up to 30% or 40% by weight of the composition. Suitable examples include alkyl benzene sulphonates, particularly sodium linear alkyl ' benzene sulphonates having an alkyl chain length of Ce-Cis; olefin sulphonates; alkane sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates.

Suitable nonionic surfactant compounds include in particular the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example, aliphatic alcohols, acids, amides or alkyl phenols with alkylene oxides, especially ethylene oxide.

Specific nonionic surfactant compounds are alkyl (C₈-. ) phenol- ethylene oxide condensates, the condensation products of linear or branched aliphatic C₈-o primary or secondary alcohols with ethylene oxide, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylene-diamine .

In a fabric washing composition, these organic surfactants preferably provide from 5 to 50% by weight of the overall composition. In a machine dishwashing composition, organic surfactant is likely to constitute from 0.5 to 8% by weight of the overall composition and is likely to consist of nonionic surfactant, either alone or in a mixture with anionic surfactant.

Water-softening agent

Tablets for use according to this invention may contain a so- called water-softening agent, which serves to remove or sequester calcium and/or magnesium ions in the water. In the context of a detergent composition containing organic surfactant, a water-softening agent is more usually referred to as a detergency builder.

When a water-softening agent (detergency builder) is present, the amount of it is likely to lie in a broad range from 5%wt, preferably 15%wt up to 98%wt of the composition. The amount is likely to be from 15 to 80%wt, more usually 15 to 60%wt of the composition. Water-softening agents may be provided wholly by water soluble materials, or may be provided in large part or even entirely by water-insoluble material with water-softening properties.

Alkali metal aluminosilicates are strongly favoured as environmentally acceptable detergency builders for fabric washing. Suitable crystalline sodium aluminosilicate ion- exchange materials are described, for example, in GB 1 429 143 (Procter & Gamble) . The preferred sodium aluminosilicates of this type are the well known commercially available zeolites A and X, the newer zeolite P described and claimed in EP-A-384 070 (Unilever) and mixtures thereof. This form of zeolite P is also referred to as "zeolite MAP". One commercial form of it is denoted "zeolite A24" (ex Ineos Silicas, UK) .

The builder may also be a water-soluble phosphorus-containing inorganic softener for example alkali-metal orthophosphates, metaphosphates, pyrophosphates and polyphosphates . Specific examples of inorganic phosphate detergency builders include sodium and potassium tripolyphosphates , orthophosphates and hexametaphosphates .

Non-phosphorus water-soluble detergency builders may be organic or inorganic . Inorganics that may be present include alkali metal (generally sodium) carbonate; while organics include polycarboxylate polymers, such as polyacrylates, acrylic/maleic copolymers, and acrylic phosphonates , monomeric polycarboxylates such as citrates, gluconates, oxydisuccinates, glycerol mono- di- and trisuccinates, carboxymethyloxysuccinates , carboxymethyloxymalonates, dipicolinates and hydroxyethyliminodiacetates . Bleach system

Tableted compositions according to the invention may contain a bleach system. This preferably comprises one or more peroxy bleach compounds, for example, inorganic persalts or organic peroxyacids, which may be employed in conjunction with activators to improve bleaching action at low wash temperatures. If any peroxygen compound is present, the amount is likely to lie in a range from 10 to 85% by weight of the composition. If the tablet contains surfactant and detergency builder, the amount of peroxygen compound bleach is unlikely to exceed 25% of the composition.

Preferred inorganic persalts are sodium perborate monohydrate and tetrahydrate, and sodium percarbonate, advantageously employed together with an activator. Bleach activators, also referred to as bleach precursors, have been widely disclosed in the art .

Disintegration-promoting particles

A tablet may optionally also contain particles to promote disintegration. Such particles typically contain at least 40% (of their own weight) of one or more materials selected from

• compounds with a water-solubility exceeding 50 grams per 100 grams water

• water swellable materials such as for example cellulose, cross-linked polyethylene glycol, cross- linked polyvinyl pyrrolidone or an acrylic/maleic copolymer

• phase I sodium tripolyphosphate

• sodium tripolyphosphate which is partially hydrated so as to contain water of hydration in an amount which is at least 0.5% by weight of the sodium tripolyphosphate in the particles. The quantity of disintegration-promoting particles may be from 1 or 5% up to 30 or 40%wt of the tablet. The quantity may possibly be from 8% up to 25 or 30%wt or more. However, it is within this invention that the amount of water-soluble disintegration-promoting particles is low, below 5%wt of the tablet or region, reliance being placed on water insoluble water swellable disintegration particles.

Further optional ingredients

Detergency enzymes may be employed in the tablets and are commonly employed in the form of granules or marumes, optionally with a protective coating, in amount of from about 0.1% to about 3.0%wt of the composition. These granules or marumes present no problems with respect to compaction to form a tablet.

The tablets of the invention may also contain a fluorescer (optical brightener) , for example, Tinopal (Trade Mark) DMS or Tinopal CBS available from Ciba-Geigy AG, Basel, Switzerland. Tinopal DMS is disodium 4, 4 'bis- (2-morpholino-4-anilino-s- triazin-6-ylamino) stilbene disulphonate; and Tinopal CBS is disodium 2, 2 '-bis- (phenyl-styryl) disulphonate.

An antifoam material is advantageously included if organic surfactant is present; especially if a detergent tablet is primarily intended for use in front-loading drum-type automatic washing machines .

It may also be desirable that a tablet of the invention includes an amount of an alkali metal silicate. A tablet for machine dishwashing will frequently contain at least 20 wt% silicate. Further ingredients which can optionally be employed in fabric washing detergent tablets of the invention include anti- redeposition agents such as sodium carboxymethylcellulose, straight-chain polyvinyl pyrrolidone and the cellulose ethers such as methyl cellulose and ethyl hydroxyethyl cellulose, fabric-softening agents; heavy metal sequestrants such as EDTA; perfumes; and colorants or colored speckles.

Particle size and distribution

A tablet of this invention is preferably a matrix of compacted particles .

Preferably the composition before compaction has an average particle size in the range of from 200 to 2000μrn, more preferably from 250 to 1400μm. Fine particles, smaller than 180μm or 200μm may be eliminated by sieving before tableting, if desired, although we have observed that this is not always essential .

The starting composition before compaction may for example have a bulk density of at least 400 g/litre, preferably at least 500 g/litre, and most preferably at least 600 g/litre.

A composition which is compacted into a tablet or tablet region may contain particles which have been prepared by spray-drying or granulation and which contain a mixture of ingredients . Such particles may contain organic detergent surfactant and some or all of any water-softening agent (detergency builder) also present in the detergent tablet.

Tablets for use in accordance to the invention may be embodied as tablets for machine dishwashing. Such tablets typically contain a high proportion of water soluble salts, such as 50 to

95% by weight, at least some of which, exemplified by sodium citrate and sodium silicate, have water-softening properties.

EXAMPLES

The invention will be further described by reference to the following examples. Further examples within the scope of the invention will be apparent to the Skilled Person.

Example 1

A detergent base powder, incorporating organic surfactants, a small percentage of crystalline sodium acetate trihydrate, and zeolite MAP was made using known granulation technology. It had the following composition, shown as parts by weight.

The amount of zeolite MAP (zeolite A24) in the table above is the amount which would be present if it was anhydrous. Its accompanying small content of moisture is included as part of the moisture and minor ingredients. The base powder and other ingredients were mixed together as set out in the following table.

Wherein:

(1) Antifoam is 17%wt silicon oil, 71%wt sodium carbonate and the remainder petroleum jelly and phosphate ester.

(2) Fluorescer is 9.9%wt fluorescer and 82.5%wt sodium carbonate the remainder being minor ingredients

(3) TAED is 83%wt TAED in 9%wt sodium sulphate the remainder being minor ingredients.

(4) Soil release polymer is 18%wt soil-release polymer, 44%wt zeolite MAP, 21%wt sodium carbonate and minor ingredients.

(5) Acrylic/maleic polymer is Sokolan CP5 ex BASF (91%wt active)

(6) Cellulosic swelling disintegrant (Arbocel ex Rettenmaier) Tablets were made by mixing the ingredients (except for the cellulosic swelling disintegrant) and finally adding the cellulosic swelling disintegrant.

Tablets were made in a labscale Graseby Specac tabletting press; tablets had a weight of 32.4 grams and a strength (expressed in terms of the diametrical fracture stress) of approximately 25k Pa. The diametrical stress is defined as DFS=2*Fmax/ (π*D*t) with Fmax being the tablet strength expressed as the force required to break a tablet when it is applied on its circumference. D the tablet diameter and t its thickness .

Two tablets are enclosed in a loosely fitting net (in the shape of a flow wrap) made of polyvinylalcohol having apertures of about 12mm² and about 45 apertures per 10 cm² with the thickness of the net being such that the solubilisation time in water at 20°C is about 600 seconds.

The net is enclosed in continuous thin film of polyvinylalcohol in the form of a flow wrap. The thickness of the material was chosen such that the time to full solubilisation in water at 20° C for the net is about 200 seconds.

When the tablets of this example are immersed on their own in water, i.e. without packaging material, they require about 220 seconds before 90%wt thereof is disintegrated and/or solubilised.

The net of medium water solubility material is capable of enclosing and retaining the tablets during the entire process of substantial disintegration. Example 2

Laundry detergent tablets of the following formulation were made;

The formulation was prepared by granulating the components in a high shear granulator. Subsequently the composition was mixed with further ingredients as given below:

Tablets were made in a Graseby Specac labscale tabletting press with a weight of 37.5 grams. Tablets had a diametrical fracture stress (DFS) of 31 ± 1.5 kPa. Disintegration was measured in accordance to example 1.

Two tablets were enclosed in a loosely fitting closed bag composed of a thin film of polyvinylalcohol to which a grid like pattern was applied by means of pulse sealing. The grid like pattern had windows of 12mm² and on average 4.5 windows per cm². The thickness of the polyvinyl-alcohol film was chosen such that the windows have a solubilisation time in water at 20°C of about 200 seconds. The time of the punch sealing treatment to apply the slower dissolving grid was chosen to give a solubilisation time of about 300 seconds which is more than the time needed for disintegration of the tablets. Example 3

A 9cm x 9cm water soluble package for laundry detergent tablets was made comprising a medium water solubility polymer grid

(PVA) and high water solubility film (HBMC, HPMC and PEG 200) as detailed below. The high water solubility film was present as the material between the grid and was also partly applied thereto .

The medium water solubility polymer grid was made using a silicon rubber mould with triangular shaped grooves (about 2mm wide and 0.5mm thick). The grooves were filled with a 15%wt polyvinylalcohol solution (88% hydrolysed, wt 88,000) which was allowed to dry in the grooves of the mould. This was repeated three times to provide a medium water solubility film of the dimensions given.

An aqueous solution of 1.05%wt Hydroxy Butyl Methyl Cellulose (HBMC; hydroxy butyl content 3.5%wt and methoxyl content 31.5%wt), 1.67%wt Hydroxy Propyl Methyl Cellulose (HPMC; hydroxy propyl content 7-12%wt and methoxyl content 28-30%wt) and 0.62%wt Polyethyleneglycol 200 plasticiser was made by heating half of the water to 90°C, adding the polymer mixture and then adding the other half of the water, all under continuous stirring. This solution was added to the top of the PVA film in the mould and allowed to dry at ambient for 24 hours. The dried film formed 10 x 10mm high water solubility discrete parts of the pack of 150 microns thickness in the spaces between the medium water solubility PVA grid.

A commercially available zeolite built laundry tablet was put into the water soluble pack which was then sealed.

The dissolution of the laundry tablet inside the soluble pack (and of the unpackaged laundry tablet) was measured by placing the packaged tablet in a hemispherical rotating cage having a diameter of 140 mm and a mesh size of 1mm x 1 mm and rotating the cage at 200 RPM in 9 litres of 15° French Hardness water at

20°C. The conductivity of the water was measured as a function of time. The time taken to arrive at 90% of the equilibrium conductivity is the t₉₀ dissolution time.

As comparative example 3A, the same type of commercially available zeolite built laundry tablet was put into a conventional non-water soluble (flexible plastic/material) net and dissolution measured according to the above test. As comparative example 3B, the dissolution of the same type of laundry tablet was measured but no type of net or pack was used. The dissolution results are given in the table below;

It can be seen that the use of a net with laundry tablets generally slows down dissolution times. The T₉₀ dissolution times for examples 3 and 3A are comparable but example 3 has the advantage that the 'net' is a temporary one formed during immersion of the packaged tablet in water thus it does not need to be removed at the end of the wash cycle unlike the net used in Example 3A. <

The speed of dissolution of the temporary net according to the invention can be controlled by choice of the pack materials and the thickness of the various parts of the pack.

Claims

1. A washing device comprising at least one tablet of compacted particulate cleaning composition in a water soluble pack, wherein the pack comprises;

2. A washing device according to claim 1 comprising from 1 to 10 tablets for fabric cleaning or machine dishwashing.

3. A washing device according to either claim 1 or claim 2 wherein the water-soluble pack comprises one or more water soluble polymers.

4. A washing device according to claim 3 wherein the one or more water-soluble polymers comprise polyester amides, polyvinylalcohol, co-polymer of polyvinylalcohol and polymethylacrylate, polyethylene oxide, alginates, cellulose ethers, water soluble starch derivatives, gelatin and combinations thereof .

5. A washing device according to claim 4 wherein the cellulose ether is carboxymethyl cellulose or methylcellulose.

6. A washing device according to claim 4 or claim 5 wherein the water soluble polymers comprise polyvinylalcohol and methyl cellulose.

7. A washing device according to either claim 5 or claim 6 wherein the methylcellulose is hydroxy ethyl methylcellulose, hydroxy butyl methylcellulose or hydroxy propyl methylcellulose .

8. A washing device according to any one of the preceding claims wherein the structure capable of enclosing the at least one tablet after solubilisation of the at least one part of high water solubility is a water soluble net comprising apertures.

9. A washing device according to claim 8 wherein from 10 to 90% of the surface area of the net is constituted by apertures .

10. A washing device according to claim 9 wherein from 30 to 70% of the surface area of the net is constituted by apertures .

11. A washing device according to any one of claims 8 to 10 wherein the apertures have an average size in the range of from 0.5 to 100mm².

12. A washing device according to claim 11 wherein the apertures apertures have an average size in the range of from 0.7 to 25mm².

13. A washing device according to any one of the preceding claims wherein the at least one part of high water solubility has a solubilisation time in water at 20°C of less than 300 seconds.

14. A washing device according to claim 13 wherein the at least one part of high water solubility has a solubilisation time in water at 20°C of less than 200 seconds.

15. A washing device according to claim 14 wherein the at least one part of medium water solubility has a solubilisation time in water at 20°C of at least 120 seconds more than the solubilisation time of the at least one part of high water solubility.

16. A washing device according to any one of the preceding claims wherein the pack comprises a film, the film comprising discrete regions of high water solubility and a continuous pattern of medium water solubility.

17. A washing device according to any one of the preceding claims wherein the pack comprises a film of high water solubility to which is applied thereto a continuous pattern of a material such that parts of the film to which the continuous pattern has been applied are of medium water solubility.

18. A washing device according to any one of the preceding claims wherein the pack comprises an inner layer of material which is of medium water solubility and which forms an open continuous structure capable of retaining the at least one tablet and further wherein the inner layer is enclosed in an outer film of high water solubility.

19. Water soluble packaging material suitable for packaging one or more cleaning tablets to form a washing device wherein the packaging material comprises ;

20. A water soluble pack for at least one tablet of compacted particulate cleaning composition wherein the pack comprises;

21. A water soluble pack according to claim 20 wherein the pack is a sachet or bag.

22. A water soluble pack according to claim 21 wherein the pack can be opened to insert at least one cleaning tablet .

23. A method of laundering fabrics wherein said method comprises the step of contacting the fabrics in the presence of water with a washing device comprising at least one tablet of compacted particulate cleaning composition in a water soluble pack and wherein the pack comprises: (i) at least one part of high water solubility, and (ii) at least one part of medium water solubility, and further wherein the at least one part of medium water- solubility has a solubilisation time in water at 20°C of at least 60 seconds more than the solubilisation time of the at least one part of high water solubility and forms a structure capable of enclosing the at least one tablet after solubilisation of the at least one part of high water solubility.

24. A method of producing a washing device comprising at least one tablet of compacted particulate cleaning composition in a water soluble pack wherein said method comprises the step of placing the at least one tablet in a water soluble pack comprising:

25. A method according to claim 24 wherein the pack is sealed after the at least one tablet is placed therein.