EP1335967B1

EP1335967B1 - Cleaning compositions

Info

Publication number: EP1335967B1
Application number: EP01995629A
Authority: EP
Inventors: Jelles Vincent Unilever Res. Vlaardingen Boskamp; Cristophe Michel Bruno Joyeux; Michel Jan Unilever Res. Vlaardingen DE RUIJTER; Alastair Richard Sanderson; Bart Unilever Research Vlaardingen SLENDEBROEK; Rahul Dominic Unilever Res. Vlaardingen VAS BHAT; Ronaldus Wilhelmus Johannes Westerhout; Douglas Unilever Research Port Sunlight WRAIGE
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2000-11-24
Filing date: 2001-11-01
Publication date: 2004-09-22
Anticipated expiration: 2021-11-01
Also published as: ATE277167T1; DE60105842T2; AU2002226327A1; ES2227322T3; DE60105842D1; EP1335967A1; WO2002042405A1

Abstract

The present invention provides a process for the manufacture of detergent tablets by granulation of organic surfactant and detergency builder to form granulated particles containing both surfactant and builder, with a water-soluble organic polymer which is solid at 25 DEG C incorporated into the particles during granulation, and, particles comprising one or more water soluble materials selected from either: compounds with a water-solubility exceeding 50 g/100g in water at 20 DEG C; or sodium tripolyphosphate, containing at least 50% of its own weight of the phase I anhydrous form, and which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate in the particles, are mixed with the granulated particles prior to compacting into tablets. Also provided is a tablet of compacted particulate detergent composition as described above. The tablets have good disintegration properties.

Description

This invention relates to cleaning compositions in the form of tablets. These tablets are intended to disintegrate when placed in water and thus are intended to be consumed in a single use. 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 (Unilever) and are now sold commercially. Tablets of composition suitable for machine dishwashing have been disclosed in e.g.EP-A-318204 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 washload, and they are more compact, hence facilitating more economical storage.
Tablets of a cleaning composition are generally made by compressing or compacting a composition in particulate form. Although it is desirable that tablets have adequate strength when dry, yet disperse and dissolve quickly when brought into contact with water, it can be difficult to obtain both properties together. Tablets formed using a low compaction pressure tend to crumble and disintegrate on handling and packing; while more forcefully compacted tablets may be sufficiently cohesive but then fail to disintegrate or disperse to an adequate extent in the wash. Tableting will often be carried out with enough pressure to achieve a compromise between these desirable but antagonistic properties. However, it remains desirable to improve one or other of these properties without detriment to the other so as to improve the overall compromise between them.
If a tablet contains organic surfactant, this can function as a binder, plasticising the tablet. However, it can also retard disintegration of the tablet by forming a viscous gel when the tablet comes into contact with water. Thus, the presence of surfactant can make it more difficult to achieve both good strength and speed of disintegration: the problem has proved especially acute with tablets formed by compressing powders containing surfactant and built with insoluble detergency builder such as sodium aluminosilicate (zeolite).
It is known to include materials whose function is to enhance disintegration of tablets when placed in wash water. For example, our EP-A-838519 mentioned above teaches the use of sodium acetate trihydrate for this purpose.
In our EP-A-466484 and EP-A-522766 it is taught that a material to act as a binder and as a disintegrant should be applied as a coating to particles of detergent composition. The arrangement which is exemplified is to coat particles of base powder by spraying onto them a solution of organic polymer in acetone. The acetone evaporates leaving a coating of the organic polymer which serves as binder and as disintegrant.
Our EP-A-716144 describes a procedure in which a particulate composition is made by a granulation process followed by admixing other solids. It is then sprayed with molten polyethylene glycol to coat the particles before these are compacted into tablets. A coating is also applied to the tablets after compaction.
DE 298 08 758 (Henkel GmbH) discloses detergent tablets comprising an extrudate prepared from a granulate comprising polyvinylpyrrolidone and/or an acrylic acid/maleic acid copolymer.
Surprisingly, we have now found that material which is effective as a binder also has a beneficial effect if it is incorporated into detergent particles while these are being made by granulation.
According to a first aspect of the present invention, there is provided a process for the manufacture of detergent tablets by granulation of organic surfactant and detergency builder to form granulated particles containing both surfactant and builder, wherein a water-soluble organic polymer which is solid at 25°C is incorporated into the particles during granulation, and, particles comprising one or more water soluble materials selected from either:

compounds with a water-solubility exceeding 50 g/100g in water at 20°C; or
sodium tripolyphosphate, containing at least 50% of its own weight of the phase I anhydrous form, and which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate in the particles.

In a second aspect, this invention provides a tablet of compacted particulate detergent wherein the particulate deteregent composition is a mixture of
(i) granulated particles of organic surfactant mixed with detergency builder, and a water-soluble organic polymer which is solid at 25°C, and,
(ii)5 to 17 wt % on total tablet of particles comprising one or more water soluble materials selected from either:
- compounds with a water-solubility exceeding 50 g/100g in water at 20°C; or
- sodium tripolyphosphate, containing at least 50% of its own weight of the phase I anhydrous form, and which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate in the particles
The term solid is used here to denote materials which have the appearance of an immobile solid at 25°C and can be handled as solids. They contrast with liquids which, even if viscous, can be seen to be capable of fluid flow. Organic polymers are general amorphous materials which are strictly classified as supercooled liquids - but of such high viscosity that for practical purposes they are solid.
The terms water-soluble is used to indicate that when the polymer is placed in water it appears, on visual inspection, to dissolve. Whether the solution is a true isotropic solution or has some colloidal character is not important to this invention.
The organic polymer is preferably applied in amounts of 1 to 15 wt% in the granulated particles.
A preferred polymer is polyethylene glycol.
We have found that the organic polymer when applied in the granulated particles provides a beneficial improvement in the speed at which a tablet disintegrates, compared with tablets of similar strength without the polymer (but otherwise similar in composition).
Alternatively, if tablets are made with similar disintegration times, a tablet with polymer displays greater strength then a tablet which does not have polymer included during granulation.
This result is surprising, since polymer incorporated into particles during granulation will not remain at the surface of the particles. This is in contrast to particles which are subsequently coated as taught in prior documents above, where the polymer is at the particle surface and available to bind particles together.
The granulated particles may consist of the said surfactant, detergency builder and the organic polymer with nothing else present in them, or they may include other materials. Particularly preferred is to include a small proportion of a salt which has a solubility exceeding 50 grams/100 grams in deionised water at 20°C.
The granulated particles may be the sole constituent of the composition which is made into tablets. Preferably, however they are mixed with other materials. These may include ingredients which participate in the overall fabric-cleaning, such as one or more of enzymes, peroxygen bleach, bleach activator and additional detergent builder. Another possibility is that the granulated particles may be mixed with materials which serve to promote tablet disintegration. It is a feature within this invention that the incorporation of water-soluble polymer in the granulated particles containing surfactant gives a benefit even when these particles are mixed with other materials which serve to promote tablet disintegration in contact with water. Notably these may be water-swellable disintegrant granules and water-soluble materials of high water-solubility which promote tablet disintegration. The last mentioned may possibly be a further quantity of one or more salts which have a solubility exceeding 50 grams/100 grams in deionised water at 20°C. This possibility may be utilised even when the granulated particles contain some of the same salts.
Forms of this invention, including preferred and optional features, and materials which may be used, will now be discussed in greater detail.
A tablet of the present invention may be either homogeneous or heterogeneous. In the present specification, the term "homogeneous" is used to mean a tablet produced by compaction of a single particulate composition, but does not imply that all the particles of that composition will be of identical composition. The term "heterogeneous" is used to mean a tablet consisting of a plurality of discrete regions, for example layers, inserts or coatings, each derived by compaction from a particulate composition. In a heterogeneous tablet according to the present invention, each discrete region of the tablet will preferably have a mass of at least 5 grams.
According to a preferred embodiment our process concerns the preparation of granulated particles containing;
a) from 10 to 70 wt% of organic surfactant
b) from 20 to 80 % by weight of detergence builder, and
c) from 1 to 15 % by weight of the organic polymer.

Water-soluble organic polymer

Tablets of the present invention require the incorporation of a water-soluble organic polymer which is solid at 25°C into the granulated particles containing organic surfactant and detergency builder.
It is preferred that the polymer material should melt at a temperature of at least 35°C, better 40°C or above, which is above ambient temperatures in many temperate countries. For use in hotter countries it will be preferable that the melting temperature is somewhat above 40°C, so as to be above the ambient temperature.
Some polymers which may be used are solids at temperatures up to 100°C, that is to say they retain a solid appearance even though they are in an amorphous state. They may soften and melt to a mobile liquid on heating further, or may decompose without melting on heating sufficiently in excess of 100°C. Such polymers will generally be added as a powder during the course of granulation. Another possibility would be addition as a solution in a volatile organic solvent, but that is not preferred.
Other polymers which may be used melt to liquid form at temperatures not exceeding 80°C and may be sprayed as molten liquid onto the surfactant and builder mixture during the course of granulation.
Organic polymers are in general amorphous solids. A significant parameter characterising amorphous solids is their glass transition temperature. When an amorphous hydrophilic polymer absorbs moisture, the moisture acts as a plasticiser and lowers the glass transition temperature of the polymer. Suitable polymers may have a glass transition temperature, when anhydrous, which is from 300 to 500K (i.e. approximately 25°C to 225°C) but may be incorporated in a moisture-containing state so that their glass transition temperature is lower.
Preferred polymer materials are synthetic organic polymers especially polyethylene glycol. Polyethylene glycol of average molecular weight 1500 (PEG 1500) melts at 45°C and has proved suitable. Polyethylene glycol of higher molecular weight can also be used (PEG 4000 melts at 56°C and PEG 6000 at 58°C).
Other possibilities are polyvinylpyrrolidone, and polyacrylate and water-soluble acrylate copolymers.
The amount of water-soluble polymer included in the particles which also contain organic surfactant and detergency builder is preferably between 0.2% or 0.5% or 1% and 15% by weight of the particles, possibly at least 1.5 or 3%. Further preferred is that the amount is not over 7 or 10% by weight. Alternatively, the amount of water-soluble polymer present may be defined in terms of the whole composition of the tablet or region thereof, in which case, it is desirably present in an amount of between 0.5% and 10% by weight, more preferably at least 1, 2 or 5% by weight. Possibly the amount of polymer does not exceed 7% by weight of the whole composition.
If further water-soluble polymer is incorporated into the composition as a separate ingredient, i.e. not in particles with organic surfactant and detergency builder, the total amount present should fall within the limits expressed above in terms of the whole composition.
The granulated particles containing the water-soluble polymer together with surfactant and detergency builder may be included in the composition in an amount of between 25% and 100% and 75% or 85% by weight of the tablet or region thereof. More preferably they provide from 35 to 85%, possibly 35 to 65 or 75% by weight of the whole composition, with the balance provided by other particles. The final composition is compacted to form tablets.

Surfactant Compounds

Compositions which are compacted to form tablets, or discrete regions thereof, of this invention contain one or more organic detergent surfactants. In a fabric washing composition, these preferably provide from 5 to 50% by weight of the composition of the tablet or region thereof, more preferably from 8 or 9% by weight of the composition up to 35% or 40% by weight. If the tablet is composed of more than one discrete region, then these preferred amounts of surfactant may apply to the tablet as a whole.
The proportion of organic surfactant in the granulated particles which also contain water-soluble polymer may be between 10 and 70% by weight of the particles, more preferably 15 to 50% by weight. In some embodiments of this invention all the surfactant is containing within these particles.
The surfactant may be anionic (soap or non-soap), cationic, zwitterionic, amphoteric, nonionic or a combination of these.
In a fabric washing tablet, anionic surfactant may be present in an amount from 0.5 to 40% by weight, preferably from 2% or 4% up to 30% or 35% by weight of the tablet or region thereof.
In a machine dishwashing composition, organic surfactant is likely to constitute from 0.5 to 8% by weight, more likely from 0.5 to 5% by weight of the composition of the tablet or region thereof and is likely to consist of nonionic surfactant, either alone or in a mixture with anionic surfactant.
Synthetic (i.e. non-soap) anionic surfactants are well known to those skilled in the art. Examples include alkylbenzene sulphonates, particularly sodium linear alkylbenzene sulphonates having an alkyl chain length of C₈-C₁₅; olefin sulphonates; alkane sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates.
In some forms of this invention the amount of non-soap anionic surfactant lies in a range from 5 to 20 or 25 wt% of the tablet or region thereof.
It may also be desirable to include one or more soaps of fatty acids. These are preferably sodium soaps derived from naturally occurring fatty acids, for example, the fatty acids from coconut oil, beef tallow, sunflower or hardened rapeseed oil.
Suitable nonionic surfactant compounds which may be used 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.
In certain forms of this invention the amount of nonionic surfactant lies in a range from 4 to 40%, better 4 or 5 to 30% by weight of the composition of the tablet or region thereof. Many nonionic surfactants are liquids. These may be absorbed onto particles of the composition prior to compaction into tablets.
Amphoteric surfactants which may be used jointly with anionic or nonionic surfactants or both include amphopropionates
The category of amphoteric surfactants also includes amine oxides and also zwitterionic surfactants, notably betaines
Another example of amphoteric surfactant are amine oxides
Cationic surfactants may possibly be used. These frequently have a quaternised nitrogen atom in a polar head group and an attached hydrocarbon group of sufficient length to be hydrophobic
The amount of amphoteric surfactant, if any, may possibly be from 3% to 20 or 30% by weight of the tablet or region of a tablet; the amount of cationic surfactant, if any, may possibly be from 1% to 10 or 20% by weight of the tablet or region of a tablet.

Detergency Builder

A composition which is compacted to form tablets or tablet regions contains a detergency builder which serves to remove or sequester calcium and/or magnesium ions in the water. In detergent tablets the amount of builder is likely to be from 15 to 80%, more usually 15 to 60% by weight of the tablet.
The proportion of detergency builder in the granulated particles which also contain water-soluble polymer may range from 20 to 80% by weight, more preferably 30 to 60% by weight.
Detergency builders 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, and are preferred in this invention. Alkali metal (preferably sodium) aluminosilicates may be either crystalline or amorphous or mixtures thereof, having the general formula: 0.8 - 1.5 Na₂O.Al₂O₃. 0.8 - 6 SiO_2. xH₂O
Suitable crystalline sodium aluminosilicate ion-exchange materials are described, for example, in GB 1429143 (Procter & Gamble). The preferred sodium aluminosilicates of this type are the well known commercially available zeolites A and X, the newer zeolite P described in EP 384070 (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".
Conceivably a detergency builder could be a layered sodium silicate as described in US 4664839. NaSKS-6 is the trademark for a crystalline layered silicate marketed by Hoechst (commonly abbreviated as "SKS-6"). NaSKS-6 has the delta-Na₂SiO₅ morphology form of layered silicate Other layered silicates, such as those having the general formula NaMSi_xO_2x+1.yH₂O wherein M is sodium or hydrogen, x is a number from 1.9 to 4, preferably 2, and y is a number from 0 to 20, preferably 0 can be used.
The less preferred category of water-soluble phosphorus-containing inorganic softeners includes the alkali-metal orthophosphates, metaphosphates, pyrophosphates and polyphosphates
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.
Tablet compositions preferably include polycarboxylate polymers, more especially polyacrylates and acrylic/maleic copolymers which have some function as water-softening agents and also inhibit unwanted deposition onto fabric from the wash liquor.

Water-Soluble Disintegration-Promoting Particles

A tablet or a region of a tablet contains particles comprising one or more water soluble materials to further promote disintegration. The water soluble material is mixed as separate particles with the granulated particles (comprising the water-soluble polymer) to form a particulate composition which is then compacted to form the tablet. The particles of the water soluble material are present in the detergent particulate composition as separate particles to the granulated particles comprising the water soluble material. Additionally water-soluble particles may also be present in the granulated particles. The water soluble material particles which are mixed with the granulated particles are selected from particles comprising either:

Such particles typically contain at least 50% (of their own weight) of one or more materials which is 1) other than soap or organic surfactant and which has a solubility of at least 50g/100g in deionised water at 20°C, or, 2) which is sodium tripolyphosphate, containing at least 50% of its own weight of the phase I anhydrous form, and which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate in the particles.
A small proportion of such soluble material may also be included in the granulated particles which contain organic surfactant, detergency builder and water soluble polymer, in an amount of preferably 1 to 25% by weight, more preferably 3 or 5% to 10 % or 15% by weight of these granulated particles.
As will be explained further below, these disintegration-promoting particles can also contain other forms of tripolyphosphate or other salts within the balance of their composition.
If the material in such water-soluble disintegration-promoting particles can function as a detergency builder, (as is the case with sodium tripolyphosphate) then of course it contributes to the total quantity of detergency builder in the tablet composition.
A solubility of at least 50 g/100g of deionised water at 20°C is an exceptionally high solubility: many materials which are classified as water soluble are less soluble than this.
Some highly water-soluble materials which may be used are listed below, with their solubilities expressed as grams of solid to form a saturated solution in 100g of deionised water at 20°C:-

Material Water Solubility (g/100g)

Sodium citrate dihydrate 72

Potassium carbonate 112

Urea >100

Sodium acetate 119

Sodium acetate trihydrate 76

Magnesium sulphate 7H₂O 71
Preferably this highly water soluble material is incorporated as particles of the material in a substantially pure form (i.e. each such particle contains over 95% by weight of the material). However, the said particles may contain material of such solubility in a mixture with other material, provided that material of the specified solubility provides at least 50% by weight of these particles.
A preferred material is sodium acetate, which may be in a partially or fully hydrated form.
It may be preferred that the highly water-soluble material is a salt which dissolves in water in an ionised form. As such a salt dissolves it leads to a transient local increase in ionic strength which can assist disintegration of the tablet by preventing nonionic surfactant from swelling and inhibiting dissolution of other materials. Alternatively it may be urea.
Specifically, tablets of this invention may contain water-soluble material, especially a material for example a salt, with a solubility exceeding 50g/100g of deionised water at 20°C, both as a small percentage within the granulated particles and as separate particles which are mixed with them.
Within the granulated particles which contain surfactant, builder and polymer, such highly water soluble material may be present in an amount from 1 to 15% by weight of those particles, preferably from 3 to 10% or 15% by weight thereof It is an advantage that the amount of such highly water soluble material which is mixed with the granulated particles is within the restricted range from 5 to 17% by weight of the tablet formulation.
Sodium tripolyphosphate is very well known as a sequestering builder in detergent compositions. It exists in a hydrated form and two crystalline anhydrous forms. These are the normal crystalline anhydrous form, known as phase II which is the low temperature form, and phase I which is stable at high temperature. The conversion of phase II to phase I proceeds fairly rapidly on heating above the transition temperature, which is about 420°C, but the reverse reaction is slow. Consequently phase I sodium tripolyphosphate is metastable at ambient temperature.
A process for the manufacture of particles containing a high proportion of the phase I form of sodium tripolyphosphate by spray drying below 420°C is given in US-A-4536377.
These particles should also contain sodium tripolyphosphate which is partially hydrated. The extent of hydration should be at least 1% by weight of the sodium tripolyphosphate in the particles. It may lie in a range from 1 to 4% by weight, or it may be higher. Indeed fully hydrated sodium tripolyphosphate may be used to provide these particles.
The remainder of the tablet composition used to form the tablet or region thereof may include additional sodium tripolyphosphate. This may be in any form, including sodium tripolyphosphate with a high content of the anhydrous phase IT form.
Suitable material is commercially available. Suppliers include Rhone-Poulenc, France and Albright & Wilson, UK.

Bleach System

Tableted compositions according to the invention may optionally contain a bleach system comprising a bleaching agent and optionally also a bleach activator. The bleach system is preferably mixed with the granulated particles. The bleach system preferably comprises one or more peroxy bleach compounds, , which may be employed in conjunction with activators to improve bleaching action at low wash temperatures.
Bleach activators, also referred to as bleach precursors, have been widely disclosed in the art and are also preferably mixed with the granulated particles
A bleach system may also include a bleach stabiliser (heavy metal sequestrant) such as ethylenediamine tetramethylene phosphonate and diethylenetriamine pentamethylene phosphonate.

Water-Swellable Material

A number of water-insoluble, water-swellable materials are known to be useful as tablet disintegrants, in particular for pharmaceutical tablets. A discussion of such materials is found in "Drug Development and Industrial Pharmacy", Volume 6, pages 511-536 (1980).
In tablets of the invention such materials may be included in an amount of 0.1% or 0.5% up to 10% by weight of the tablet or discrete region thereof. Preferably these materials are mixed with the granulated particles. Such materials may be mixed with each other, or mixed with other materials as carriers. If these water-swellable materials are included as part of disintegrant particles, these particles may be present in an amount of 1 to 10 % by weight.
Suppliers of water-swellable disintegrant materials include J Rettenmaier & Söhne in Germany and FMC Corporation in USA.
Such swelling materials are mostly polymeric in nature and many of them are of natural origin. Such disintegrants include starches, for example, maize, rice and potato starches and starch derivatives, such as Primojel™, or Explotab™, both of which are sodium starch glycolate also known as sodium carboxymethyl starch; celluloses, for example, Arbocel®-B and Arbocel®-BC (beech cellulose), Arbocel®-BE (beech-sulphite cellulose), Arbocel®-B-SCH (cotton cellulose), Arbocel®-FIC (pine cellulose) as well as further Arbocel® types from Rettenmaier and cellulose derivatives, for example Courlose™ and Nymcel™, sodium carboxymethyl cellulose, Ac-di-Sol™ cross-linked modified cellulose, microcrystalline cellulosic fibres and cross-linked cellulose; and various synthetic organic polymers.
Cellulose-containing fibrous materials originating from timber may be compacted wood pulps. So-called mechanical pulps generally incorporate lignin as well as cellulose whereas chemical pulps generally contain cellulose but little of the original lignin remains. Pulp obtained by a mixture of chemical and mechanical methods may retain some but not all of the original lignin. Cellulose based materials include Nylin LX-16 which is a water-insoluble compacted cellulose based disintegrant, commercially available from FMC Corporation.
Disintegrant granules may consist of a water-absorbent carrier material which may swell on initial contact with water, mixed with a minor proportion of another material which swells more strongly than the carrier material on contact with water. It may take up more water than the carrier material, or swell more rapidly or both. The disintegrant granules may contain a mixture of 0.001 to 10% of their own weight of a water-insoluble material which swells to at least twice its own volume on contact with water, and a balance from 90 to 99.999% of other material which swells to a lesser extent on contact with water. Preferably the proportions may be from 75% or 90% up to 99.9% of the carrier material and from 0.1 up to 10%, of the more strongly swelling material. Other material may be included to make up any balance.
An apparatus for measuring increase in volume is illustrated in "The Mechanisms of Disintegrant Action". Kanic & Rudnic, Pharmaceutical Technology, April 1984, pages 50-63. This article also refers to papers describing other apparatus.
Another parameter which characterises swellable materials is the force which they exert if they are allowed to take up water whilst confined within an enclosure.
We have found that materials and particles which swell on contact with water are effective as disintegrants if there is a rapid development of force when they come into contact with water.
We have carried out measurements using a relatively simple piece of apparatus shown in the attached drawing and an Instron materials testing machine type 5566 from Instron, UK (herein after referred to as "the Instron machine").
The apparatus consists of a cylinder (10) with internal diameter 25mm and a length of 20mm. This cylinder is perforated by a ring of holes (12) adjacent one end. There are 36 of these holes, of 1mm diameter, with centres 2.5mm from the end of the cylinder.
This end of the cylinder is glued to the base of a glass container (14) of internal diameter 73mm.
To test a sample of powdered disintegrant, 1.5 gram of the disintegrant is placed in the cylinder and gently tapped so that it forms a level bed (16) which is usually 6mm to 10mm deep depending on the bulk density of the powder.
A plunger (18) of the Instron machine is moved into the upper set of the cylinder, over this powder bed.
Under computer control of the Instron machine the plunger is applied to the top of the powder bed (16) with a force of 1 Newton.
50ml of distilled water at 22°C is tipped into the annular space (20) around the cylinder. This water passes through the holes (12) into the powder bed. The Instron machine is programmed to hold the plunger in position against the swelling bed of powder, and the force required for this is recorded.
It is preferred that a strongly swelling material, if tested, by itself, has ability to absorb at least twice its own volume of water and has a development of expansion force which exceeds 1.5 Newton/second.

The development of swelling force has been measured for a number of materials, as set out in the following table.

Trade Name	Chemical Nature	Disintegrating force development rate (N/sec)
	Maize starch	1.1
Explotab	Na-carboxy methyl starch ex. Mendell Co	2.0
Primojel	Na-carboxy methyl starch ex Avebe	2.2
Avicel PH 101	Micro crystalline cellulose ex. FMC	0.6
L-HPC	Low substituted hydroxy propyl cellulose ex. Shin-Etsu Japan	2.2
Ac-di-Sol	Cross-linked SCMC ex FMC	3.5
Polyplasdone XL	Cross-linked PVP ex. ISP	4.3
Amberlite IRP 88	K-salt of methacrylic acid cross-linked with divinylbenzene ex. Rohm & Haas	5.0
Plas-Vita	Co-polymer of formalin and casein ex. Eigenmann-Veronelli	3.1

The significant parameter is the maximum slope of a graph of expansion force against time.
Measurement of swelling can be recorded with the same apparatus. The plunger is again applied to the top of a bed of the dry powder, and pressed against it with a force of 1 Newton. 50ml of water is poured in as before. The Instron machine is programmed to allow expansion of the bed of powder, while maintaining a force on it of 1 Newton. Displacement of the plunger is recorded.
A strongly swelling material may come from a category referred to as a super-disintegrant. Such super disintegrants tend to be cross-linked synthetic or natural polymers and include cross-linked forms of carboxymethyl cellulose, cellulose, starch, polyvinylpyrrolidone and polyacrylate. The carrier materials are preferably selected from compounds which contain hydroxy groups. A carrier material may itself be a water-insoluble, and somewhat water-swellable material. Such materials include starches, for example, maize, rice and potato starches, celluloses, microcrystalline cellulosic fibres and some synthetic organic polymers. Disintegrant particles may also contain up to 15% or 20% by weight of a water-soluble polymer which acts as a binder, e.g. polyethylene glycol.
Specifically, a super-disintegrant may take up more than twice and possibly more than 2.5 or 3 times its own volume of water, and/or develop expansion force exceeding 1.5 Newton/second while a carrier for it takes up less water by volume than the super-disintegrant and develops less expansion force.
The disintegrant particles may be made by mixing the swellable disintegrant with the carrier material, then compacting the mixture, and if necessary comminuting the compacted mixture into disintegrant particles. Preferably these have a mean particle size in a range from 250 to 1000 microns.
Mixing of these materials can be carried out by standard apparatus for mixing particulate solids. Other ingredients can be incorporated at this stage. If a polymeric binder is incorporated, it can be added in particulate form during this mixing operation. Alternatively, if it can be melted, the molten polymer can be sprayed on to the mixture or on to one particulate ingredient of the mixture.
Compaction of the mixture can be brought about by forcing it between a pair of rollers. Suitable apparatus - a roller compactor - has a feed screw which delivers the mixture to the nip of the rollers. The speed of the feed screw, and hence the amount of material delivered to the nip of the rollers should be high enough to force an unbroken stream of material through the rollers, but not so high that the material is converted into a dough.
The sheet of material which issues from the rollers is next broken up and milled to the required particle size.
Manufacturers of both roller compactor and milling machinery include Hosokawa Bepex located at Heilbronn, Germany, Alexanderwerk located at Remschied, Germany and Fitzpatrick located at Elmhurst, USA.

Other Ingredients

Tablets of the invention may also contain one of the detergency enzymes well known in the art for their ability to degrade and aid in the removal of various soils and stains
The tablets of the invention may also contain a fluorescer (optical brightener).
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, particularly sodium ortho-, meta- or disilicate. The presence of such alkali metal silicates at levels, for example, of 0.1 to 10 wt%, may be advantageous in providing protection against the corrosion of metal parts in washing machines, besides providing some measure of building and giving processing benefits in manufacture of the particulate material which is compacted into tablets. A composition for fabric washing will generally not contain more than 15 wt% 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, fabric-softening agents; heavy metal sequestrants , perfumes; and colorants or coloured speckles.
The above may result in the most preferred composition wherein a process is applied wherein the composition contains;
a) from 25 to 75% of granulated particles
b) from 0 to 25% of peroxygen bleach
c) from 0 to 10% of bleach activator
d) from 1 to 10% of water-swellable disintegrant granules
e) and from 5 to 17% of one or more salts with a solubility of at least 50 g per 100 g in deionised water at 20°C.
The tablets which result from the process according to the invention are also part of the invention and can be formulated as:
a tablet of compacted particulate detergent composition , wherein the particulate detergent composition is a mixture of
(i)granulated particles of organic surfactant mixed with detergency builder, and a water-soluble organic polymer , which is solid at 25°C and
(ii) 5 to 17 wt % on total tablet of particles comprising one or more water soluble materials selected from either:
- compounds with a water-solubility exceeding 50 g/100g in water at 20°C; or
- sodium tripolyphosphate, containing at least 50% of its own weight of the phase I anhydrous form, and which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate in the particles.

Bulk Density & Granulation Process

While the starting particulate composition may in principle have any bulk density, the present invention may be especially relevant to tablets of detergent composition made by compacting powders of relatively high bulk density, because of their greater tendency to exhibit disintegration and dispersion problems. Such tablets have the advantage that, as compared with a tablet derived from a low bulk density powder, a given dose of composition can be presented as a smaller tablet.
Thus the starting particulate composition may suitably have a bulk density of at least 400 g/litre, preferably at least 500 g/litre, and possibly at least 600 g/litre.
Granular detergent compositions of high bulk density prepared by granulation and densification in a high-speed mixer/granulator, as described and claimed in EP-A-340013 (Unilever), or by the continuous granulation/densification processes as described and claimed in EP-A-367339 (Unilever), are inherently suitable for use in the present invention.
Another particularly suitable process for the preparation of a high-bulk density detergent powder is described in WO-A-98/11193 (Unilever). In this document, a feedstock of the starting acid for production of the anionic surfactant is partially neutralised, for example by sodium hydroxide, before being fed into a high-speed mixer densifier (e.g. Lodige CB 30 Recycler) where the partially neutralised acid feedstock is completely neutralised, whilst being mixed with the majority of other components of the detergent base powder granule. This powder can be further densified by treating in a moderate speed mixer (e.g. Lodige KM 300 mixer), before which stage further detergency builder may be added. The water-soluble polymer material is preferably added before the further densification step, although it may be added in the first mixer. The water-soluble polymer material may be heated to a temperature considerably above its melting point to obtain a free-flowing liquid. The resulting powder can be cooled and dried using a fluid bed, after which any desired particle size control can be exercised.
Another suitable granulation process is described in WO 00/77147 (Unilever). A liquid binder is contacted with a solid starting material in a high-speed mixer and the resulting mixture is treated in a medium or low speed mixer and finally in a gas fluidisation granulator, where more liquid binder is added.
Any separate particles containing further components of the finished formulation can be mixed with the base powder prior to compaction.

Particle Size Control

Particle sizes can be controlled in the manufacturing process of the particles included in the composition. Oversize particles are usually removed by sieving (for example by a Mogensen screen) at the end of the production process, followed by milling and recycling of the removed oversize fraction.
Undersize particles can also be removed by sieving, or if the manufacturing process employs a fluidised bed undersized particles may be entrained in the air stream and subsequently recovered from it for recycling to the granulation stage.
It is preferred that the average particle size of the granulated particles is between 400 and 1100 micrometers, preferably between 500 and 1000 micrometers. Preferably no more than 5% of these particles is smaller than 200 micrometers while no more than 5% is larger than 1400 micrometers.
Materials which are mixed with the granulated particles may also comply with these requirements concerning particle size.

Tableting

Tableting entails compaction of a particulate composition. A variety of tableting machinery is known, and can be used. Generally it will function by stamping a quantity of the particulate composition which is confined in a die.
Tableting may be carried out at ambient temperature or at a temperature above ambient which may allow adequate strength to be achieved with less applied pressure during compaction. In order to carry out the tableting at a temperature which is above ambient, the particulate composition is preferably supplied to the tableting machinery at an elevated temperature. This will of course supply heat to the tableting machinery, but the machinery may be heated in some other way also.
If any heat is supplied, it is envisaged that this will be supplied conventionally, such as by passing the particulate composition through an oven, rather than by any application of microwave energy.
The mass of a tablet will suitably range from 10 to 160 grams, preferably from 15 to 60 g, depending on the conditions of intended use, and whether it represents a dose for an average load in a fabric washing or dishwashing machine or a fractional part of such a dose. The tablets may be of any shape. However, for ease of packaging they are preferably blocks of substantially uniform cross-section, such as cylinders or cuboids. The overall density of a tablet for fabric washing preferably lies in a range from 1040 or 1050g/litre preferably at least 1100g/litre up to 1400g/litre. The tablet density may well lie in a range up to no more than 1350 or even 1250m/litre. The overall density of a tablet of some other cleaning composition, such as a tablet for machine dishwashing or as a bleaching additive, may range up to 2700g/litre and will often lie in a range from 1300 to 1550g/litre.
The invention will be further described by reference to the following examples. Further examples within the scope of the present invention will be apparent to the person skilled in the art.

Example 1 (comparative)

Two detergent base powders, incorporating organic surfactants and detergency builder were made using the process described in WO-A-98/11193, with incorporation of the PEG 1500 in Example B by spraying it on as a liquid at around 70°C before the moderate speed mixer. The powders had the following compositions. Amounts are shown both as weight percentages of the base powder..

Ingredient	wt. %
	A	B
Sodium linear alkylbenzene	23.59	20.73
sulphonate
PEG 1500	-	4.49
nonionic surfactant (C13-15 branched fatty alcohol 7EO)	7.05	6.19
Soap	1.65	1.45
zeolite A24	40.61	42.51
Sodium acetate trihydrate	10.21	8.98
Sodium carbonate	4.97	4.33
sodium carboxymethyl cellulose (SCMC)	0.92	0.81
Sodium citrate	3.06	2.69
Sodium sulphate, moisture and minor ingredients	7.93	7.82
Total	100	100.00

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. Sodium carboxymethyl cellulose is a commonly used water soluble anti-redeposition polymer.

A number of further ingredients were added to this base powder by dry-mixing (except the perfume, which was sprayed on) resulting in the following compositions:

	Parts by Weight
	Option 1	Option 2
Base powder A	41.06	-
Base powder B	-	43.22
Anti-foaming granule	1.74	1.74
Fluorescer on sodium carbonate	1.20	1.20
Soil release polymer (18% on carrier)	1.06	1.06
Acrylate-maleate copolymer	1.16	1.16
Na-silicate (granular) 80%	3.09	3.09
TAED granules (83% active)	4.91	4.91
Sodium Percarbonate (coated)	14.56	14.56
Sequestrant granules (Dequest 2047)	0.72	0.72
Sodium acetate trihydrate	22.79	22.79
Blue speckles	1.35	1.35
PEG 1500	2.17	-
Nylin LX-16	2.91	2.91
Enzymes	0.86	0.86
Perfume	0.44	0.44
TOTAL	100.00	100.00

Nylin LX-16 is a water-insoluble compacted cellulosic disintegrant commercially available from FMC Corporation. The amount of PEG 1500 added to option 1 is slightly more than the amount of PEG included in option 2 (which is present through the amount present in base powder B).
These compositions were compacted with several levels of applied force on a Fette rotary press to produce cylindrical tablets with a weight of approximately 42.5 grams, with target diametrical fracture stresses of 25 and 35 kPa.
The strength of the tablets, in their dry state as made on the press, was determined as their diametrical fracture stress DFS, which is calculated from the equation: DFS = 2Fmax πDt where DFS is the diametrical fracture stress in Pascals, F_max is the applied load in Newtons to cause fracture, D is the tablet diameter in metres and t is the tablet thickness in metres.
The test is carried out using an Instron type universal testing instrument to apply compressive force on a tablet diameter (i.e. perpendicular to the axis of a cylindrical tablet).
It is preferred that tablets have a DFS of at least 14kPa, better at least 20kPa and possibly at least 25kPa.
The disintegration of the tablets was tested by placing a tablet on a 1cm by 1cm gauze in 1 litre of still water at 10°C and measuring the time (t₉₀) it takes for 90% by weight of the tablet to fall through the grid. The results are shown below.

Option DFS [kPa] t₉₀ [s]

1 27 191

36 256

2 25 150

37 188

Example 2

Two detergent base powders, incorporating organic surfactants and detergency builder were made as in Example 1. They had the following composition, which is shown as weight percentages of the base powder. Base powder C and options 1a, 1b and 2a are comparative examples.

Ingredient	Wt. %
	C	D
Sodium linear alkylbenzene sulphonate	20.82	19.85
PEG 1500	-	2.81
nonionic surfactant (C13-15 branched fatty alcohol 7EO)	9.03	8.62
Soap	1.59	1.51
zeolite A24	46.52	46.01
Sodium acetate trihydrate	5.89	5.62
Sodium carbonate	6.92	6.29
sodium carboxymethyl cellulose (SCMC)	0.88	0.84
Sodium sulphate, moisture and minor ingredients	8.33	8.15
Total	100.00	100.00

A number of further ingredients were added to this base powder by dry-mixing (except the perfume, which was sprayed on) resulting in the following composition:

	Parts by Weight
	Option 1a	Option 1b	Option 2a	Option 2b
Base powder C	43.00	47.78	-	-
Base powder D	-	-	44.27	49.20
Anti-foaming granule	1.70	1.89	1.70	1.89
Fluorescer on sodium carbonate	1.30	1.44	1.30	1.44
PVP granule	0.15	0.17	0.15	0.17
Soil release polymer (18% on carrier)	0.50	0.56	0.50	0.56
Na-silicate (granular) 80%	2.25	2.50	2.25	2.50
TAED granules (83% active)	3.50	3.89	3.50	3.89
Sodium Percarbonate (coated)	14.00	15.56	14.00	15.57
Sequestrant granules(Dequest 2047)	0.75	0.83	0.75	0.84
Sequestrant granule(Dequest 2016)	0.50	0.55	0.50	0.55
Sodium citrate	3.00	3.33	3.00	3.33
Sodium acetate trihydrate	21.00	12.22	21.73	13.00
PEG 1500	2.00	2.22	-	-
Nylin LX-16	5.00	5.56	5.00	5.56
Enzymes	0.90	1.00	0.90	1.00
Perfume	0.45	0.50	0.45	0.50
TOTAL	100.0	100.0	100.0	100.0

The compositions were compacted on a Fette rotary press to produce cylindrical tablets with a weight of approximately 42.5 grams (for tablets of 1a and 2a) and 38.5 grams (for tablets of 1b and 2b). The applied force was adjusted to give strength close to a target diametrical fracture stress of 25 kPa. The tablets were chosen to provide approximately equal amounts of the surfactant, builder and bleach.
All of these tablets contained hydrated sodium acetate and citrate among the materials added to the granulated particles. Incorporation of this material is known to increase the speed of tablet dissolution, compared to tablets of similar strength without sodium acetate trihydrate, as taught in EP 838519 A (Unilever). The amounts used in options 1b and 2b were less than the amounts used in options 1a and 2a.

The diametrical fracture stress of the tablets was measured as in Example 1. The disintegration of the tablets was measured by placing two tablets of each type in a washing machine dispenser. The dispenser was of a type used in Philips washing machines (AWB 126/127). Water at 10°C flowing at a rate of 5 litres per minute was passed through the dispenser until the two tablets were completely washed out of the dispenser. The time was noted as the dispensing time and is reported in the table below which also summarises the distinctions between the four tablet formulations.

	option 1a	option 1b	option 2a	option 2b
	PEG added separately.	PEG added separately. Reduced acetate.	PEG in base powder.	PEG in base powder. Reduced acetate.
Weight (g)	42.6	38.5	42.6	38.5
Compaction Force (kN)	8.3	7.1	14.6	12.4
DFS (kPa)	24.9	25.4	25.5	27.7
Dispensing time(s)	70	102	68	66

Option 1a and option 2a used similar, fairly high, concentrations of sodium acetate. Both provided similar strength with similar time for the tablets to disintegrate and wash from the dispenser into the washing machine. Option 1b and option 2b had a reduced concentration of sodium acetate. option 1b gave a longer disintegration time than option 1a. Unexpectedly, however, option 2b disintegrated as rapidly as options 1a and 2a. Thus, the invention is enabling use of a reduced quantity of sodium acetate.

Claims

A process for the manufacture of detergent tablets by granulation of organic surfactant and detergency builder to form granulated particles containing both surfactant and builder, wherein a water-soluble organic polymer which is solid at 25°C is incorporated into the particles during granulation, and further wherein, particles comprising one or more water soluble materials selected from either:

compounds with a water-solubility exceeding 50 g/100g in water at 20°C; or

sodium tripolyphosphate, containing at least 50% of its own weight of the phase I anhydrous form, and which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate in the particles.

are mixed in an amount of 5 to 17 wt % on total tablet with the granulated particles to form a particulate composition, followed by compacting the particulate composition into tablets.
A process according to claim 1 wherein the water-soluble organic polymer is polyethylene glycol.
A process according to either claim 1 or claim 2 wherein the granulated particles contain from 1% to 15% by weight of the organic polymer.
A process according to any one of the preceding claims wherein the granulated particles contain;

a) from 10% to 70% by weight of organic surfactant,

b) from 20% to 80% by weight of detergency builder, and

c) from 1% to 15% by weight of the organic polymer.
A process according to any one of the preceding claims wherein the granulated particles contain from 1% to 15% by weight of material which has a solubility of at least 50 g per 100 g in deionised water at 20°C.
A process according to any one of the preceding claims, the process including a step of mixing the granulated particles with one or more other materials to form a particulate composition containing from 25% to 75% by weight of the granulated particles, followed by compacting that composition into tablet.
A process according to claim 6 wherein the other material mixed with the granulated particles is peroxygen bleach.
A process according to claim 7 wherein the other material mixed with the granulated particles is a bleach activator.
A process according to any one of claims 6 to 8 wherein the other material mixed with the granulated particles is water-swellable disintegrant granules.
A process according to claim 9 wherein the disintegrant granules contain a mixture of 0.001 to 10% of their own weight of a water-insoluble material which swells to at least twice its own volume on contact with water, and a balance from 90 to 99.999% of other material which swells to a lesser extent on contact with water.
A process according to any one of claims 6 to 10 wherein the composition contains;

a) from 25 to 75% of granulated particles

b) from 0 to 25% of peroxygen bleach

c) from 0 to 10% of bleach activator

d) from 1 to 10% of water-swellable disintegrant granules

e) and from 5 to 17% of one or more salts with a solubility of at least 50 g per 100 g in deionised water at 20°C.
A tablet of compacted particulate detergent composition , wherein the particulate detergent composition is a mixture of

(i)granulated particles of organic surfactant mixed with detergency builder, and a water-soluble organic polymer , which is solid at 25°C and

(ii) 5 to 17 wt % on total tablet of particles comprising one or more water soluble materials selected from either:

compounds with a water-solubility exceeding 50 g/100g in water at 20°C; or

sodium tripolyphosphate, containing at least 50% of its own weight of the phase I anhydrous form, and which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate in the particles.
A tablet according to claim 12 wherein the water-soluble organic polymer is polyethylene glycol.