IE911056A1 - Fabric cleaning process - Google Patents

Abstract

A process is for washing fabrics in a horizontal drum type automatic washing machine that involves the establishment of a localised high concentration of a water soluble carboxylate chelating salt forming one of the builder components of the detergent composition in the wash liquor immediately surrounding the fabrics in the rotatable drum during the period immediately following the start of the wash cycle. The carboxylate chelating salt develops at least 80 % of its equilibrium concentration within 45 seconds and the free Ca ++ ion concentration is reduced to no more than 0.1 mmoles/litre after not more than 30 secs following the start of rotation or oscillation of the drum. The water soluble carboxylate chelating salt is preferably a monomeric or oligomeric carboxylate salt having a first carboxyl logarithmic acidity constant (pK) value of less than 9, preferably between 2 and 8.5.

Description

This invention relates to a process for washing fabrics and more particularly to a washing process in which a detergent product is employed that contains little or no phosphorus in its constituent components.

Much effort has been expended in recent years on the minimisation of the environmental impact of detergent products in view of increasing public concern in this area. One consequence of this concern has been the broad scale adoption of hydrated synthetic zeolites such as Zeolite A, X, P & Y as partial or total replacements for the polyphosphate builders traditionally used in detergent products.

Synthetic zeolites cannot however perform all of the builder functions carried out by phosphates and this has resulted in the development and commercial introduction of detergent products containing builder systems in which zeolites form but one of several components of a combination of materials. Examples of such compositions are disclosed in British Patent Nos. 1429143, 1473202, 2041394, European Patent No. 0103639 and European Patent Application Publication Nos. 0313143 & 0313144.

Such non-phosphate zeolite-containing products have achieved acceptable performance in consumer terms although parity technical performance with polyphosphate-built detergent products has not thereby been achievable. Furthermore, non phosphate zeolite-containing products are relatively more costly and complex than their phosphate-built counterparts and the roles played by the various components of the builder systems are not fully understood. Efforts have therefore continued to simplify these systems and to achieve the same or better performance at reduced cost and complexity.

It has now been found that establishment of a localised high concentration of certain water soluble components of a non-phosphate builder system in the immediate vicinity of a load of soiled fabrics at the start of a wash cycle can significantly improve the efficiency of the laundering process.

According to the present invention there is provided a process of washing fabrics in an automatic washing machine, said machine comprising a perforated container rotatable about a horizontal axis within an outer vessel serving as a wash liquor reservoir, said process comprising the steps of a) placing a load of soiled fabrics within said perforated container; b) charging said outer vessel with water such that the depth of water within the perforated container is no greater than two thirds of the internal radius thereof; c) commencing mechanical agitation of the fabrics by oscillatory and/or rotary motion of the perforated container; d) simultaneously with, or immediately after step c), contacting the fabrics in the perforated container with a detergent product comprising from 3% to 30% by weight of an organic surfactant and from 10% to 60% of a non-phosphate detergent builder system - 3 comprising a water soluble monomeric or oligomeric carboxylate chelating salt; e) removing the soil-containing wash liquor from said outer vessel; and f) treating said washed fabrics with rinse water to extract residual wash liquor therefrom wherein step d) comprises contacting the fabrics with an amount of said product to give an equilibrium product concentration of from 0.5% to 1.0% by wt of the water in such a manner that, after not more than 45 seconds after the commencement of step (c) said water soluble monomeric or oligomeric carboxylate chelating salt develops a transient concentration, at a pH of from 7 to 11 within the liquor in said perforated container, of at least 80% of the equilibrium concentration that would be reached in the volume of water charged to the machine; said builder system being such that; in a test in which 3 kg of unsoiled cotton fabric is contacted in the same machine in the same manner as in step (d) with lOOg of a composition comprising an amount of the builder system, bleach and buffer salt components corresponding to that in the product at the usage level employed in step (d) ballasted with neutral inorganic salts, the machine being charged with mineral hardness solution comprising 3.50 m moles/litre Ca+ + and 0.98 m moles/litre Mg-I- + in distilled water at 15 °C, in an amount corresponding to the amount of water charged to the machine in step (b), the level of free Ca+ + ions in the liquor within the container is reduced to no more than 0.1 m moles/litre within 30 seconds of the commencement of the first oscillatory or rotary motion of the perforated container.

Preferably the level of free Ca+ + ions is reduced to 0.06 m moles/litre or less within 30 seconds of the commencement of the first oscillatory - 4 or rotary motion of the perforated container.

Preferably the concentration of the water-soluble monomeric carboxylate chelating agent within the liquor in the perforated container reaches a transient value of at least 80% of the equilibrium concentration within 30 seconds of the start of the first rotary or oscillatory movement of the perforated container. More preferably the concentration of the water soluble monomeric carboxylate chelating salt within the liquor in the perforated container reaches a transient value of 80% of the equilibrium concentration within 15 seconds of the start of the first rotary or oscillatory movement of the perforated container.

Preferably also the water soluble monomeric carboxylate chelating salt is an alkali metal citrate or a mixture thereof with citric acid.

The present invention relates to a process for washing fabrics in a horizontal drum type automatic washing machine and to certain non-phosphate detergent compositions when used therein. The process involves the establishment of a localised high concentration of at least one of the builder components of the detergent composition in the wash liquor immediately surrounding the fabrics in the rotatable drum during the period immediately following the start of the rotation of the drum in the wash cycle.

It has been found that the addition of a detergent product through the dispensing compartment of an automatic washing machine results in the attainment of less than 50% of the equilibrium concentration of water soluble builder over the first 1-2 minutes of the wash cycle. In contrast the process of the present invention provides a concentration of the water soluble carboxylate chelating salt of more than 80% of the equilibrium concentration, in the wash liquor immediately surrounding the fabrics in the rotatable drum, within 45 seconds of the start of the - 5 rotation of the drum. Preferably this transient concentration is reached within 30 seconds and in the most preferred executions, it occurs within 15 seconds. Other builder components will also be available at higher concentrations than are normally attainable over this time interval and the overall effect is a rapid reduction in the free Ca+ + ion concentration in the vicinity of the soiled fabrics, thereby permitting enhancement of cleaning and other hardness-influenced effects.

The ability of the product to produce this enhanced cleaning by means of the washing process of the invention can be assessed by the performance of the carboxylate salt-containing builder system in a model test to determine Ca+ + ion reduction. This is described in detail hereinafter.

When the detergent product is used in an amount to give an equilibrium product concentration of from 0.5% to 2.0% by weight, preferably from 0.6% to 0.9% by weight in the water charged to the machine, enhanced cleaning performance relative to delivery via the conventional dispenser can be obtained.

The washing processes of the present invention utilise a wash liquor comprising a mixture of surfactant and detergent builders, preferably a mixture of soluble and insoluble detergent builders, optionally together with soil suspending agents, suds suppressing agents, oxygen bleaches, fluorescers, enzymes and other conventional functional ingredients.

The water-soluble builder can be any monomeric or oligomeric carboxylate chelating agent but is preferably a monomeric or oligomeric carboxylate chelating agent having a first carboxyl logarithmic acidity constant (pK) of less than 9, preferably of between 2 and 8.5, more preferably of between 4 and 7.5.

The logarithmic acidity constant is defined by reference to the equilibrium H+ + A ------?H + A where A is the fully ionized carboxylate anion of the builder salt.

The equilibrium constant is therefore Kj = H+ A__ H+ (A) and pKi = logioK.

For the purposes of this specification, acidity constants are defined at 25°C and at zero ionic strength. Literature values are taken where possible (see Stability Constants of Metal-Ion Complexes, Special Publication No. 25, The Chemical Society, London): where doubt arises they are determined by potentiometric titration using a glass electrode. In the case of polymeric polycarboxylate builders, the various carboxylate acidity constants are determined using the Katchalsky form of the Henderson-Hesselbalch equation (see A Katchalsky and P.

Spitnik, J. Polvm. Sci.. 1957, 22,451).

Preferred carboxylates can also be defined in terms of their calcium ion stability constant (pK£a +·+) defined, analogously to pKj, by the equations pKCa++ = l°glOKCa-H + where Kca++ = (Q++ A)_ (Ca++) (A) Preferably, the polycarboxylate has a pKca+ + in the range from about 2 to about 7 especially from about 3 to about 6. Once again literature values of stability constants are taken where possible. The stability constant is defined at 25 °C and at zero ionic strength using a glass electrode method of measurement as described in Complexation in Analytical Chemistry by Anders Ringbom (1963).

The carboxylate or polycarboxylate builder can be monomeric or oligomeric in type although monomeric polycarboxylates are generally preferred for reasons of cost and performance.

Monomeric and oligomeric builders can be selected from acyclic, alicyclic, heterocyclic and aromatic carboxylates having the general formulae (a) Rl cR2 γ- v - Λ L Z n or wherein Ri represents H, a Ομβθ alkyl or alkenyl group optionally substituted by hydroxy, carboxy, sulfo or phosphono groups or attached to a polyethylenoxy moiety containing up to 20 ethyleneoxy groups; R2 represents H,Ci_4 alkyl, alkenyl or hydroxy alkyl, or alkaryl, sulfo, or phosphono groups; X represents a single bond; O; S; SO; SO2; or NRj; Y represents H; carboxy;hydroxy; carboxy methy loxy; or Ci-30 alkyl or alkenyl optionally substituted by hydroxy or carboxy groups; Z represents H; or carboxy; m is an integer from 1 to 10; n is an integer from 3 to 6; p, q are integers from 0 to 6, p + q being from 1 to 6; and wherein X, Y, and Z each have the same or different representations when repeated in a given molecular formula, and wherein at least one Y or Z in a molecule contains a carboxyl group.

Suitable carboxylates containing one carboxy group include lactic acid, glycollic acid and ether derivatives thereof as disclosed in Belgian Patent Nos. 831,368, 821, 369 and 821,370. Polycarboxylates containing two carboxy groups include the water-soluble salts of succinic acid, malonic acid, (ethylenedioxy) diacetic acid, maleic acid, diglycollie acid, tartaric acid, tartronic acid and fumaric acid, as well as the ether carboxylates described in German Offenlegenschrift 2,446,686, and 2,446,687 and U.S. Patent No. 3,935,257 and the sulfinyl carboxylates described in Belgian Patent No. 840,623. Polycarboxylates containing three carboxy groups include, in particular, water-soluble citrates, aconitrates and citraconates as well as succinate derivatives such as the carboxymethyloxysuccinates described in British Patent No. 1,379,241, lactoxysuccinates described in British Patent No. 1,389,732, and aminosuccinates described in Netherlands Application 7205873, and the oxypolycarboxylate materials such as 2-oxa-l,l,3-propane tricarboxylates described in British Patent No. 1,387,447.

Polycarboxylates containing four carboxy groups include oxydisuccinates disclosed in British Patent No. 1,261,829, 1.1.2.2- ethane tetracarboxylates, 1,1,3,3-propane tetracarboxylates and 1.1.2.3- propane tetracarboxylates. Polycarboxylates containing sulfo substituents include the sulfosuccinate derivatives disclosed in British Patent Nos. 1,398,421 and 1,398,422 and in U.S. Patent No. 3,936,448, and the sulfonated pyrolysed citrates described in British Patent No. 1,082,179, while polycarboxylates containing phosphone substituents are disclosed in British Patent No. 1,439,000.

Alicyclic and heterocyclic polycarboxylates include cyclopentane-cis,cis,cis-tetracarboxylates, cyclopentadienide pentacarboxylates, 2,3,4,5-tetrahydrofuran - cis, cis, cis-tetracarboxylates, 2,5-tetrahydrofuran -cis - dicarboxylates, 2,2,5,5-tetrahydrofuran - tetracarboxylates, 1,2,3,4,5,6-hexane -hexacarboxylates and carboxymethyl derivatives of polyhydric alcohols such as sorbitol, mannitol and xylitol. Aromatic polycarboxylates include mellitic acid, pyromellitic acid and the phthalic acid derivatives disclosed in British Patent No. 1,425,343.

Of the above, the preferred polycarboxylates are hydroxy carboxylates containing up to three carboxy groups per molecule, more particularly citrates.

Whilst mixtures of polycarboxylate salts and their parent acids such as citrate/citric acid mixtures are contemplated by the present invention, it is important that the carboxylate chelating salt has an overall pH such that the pH of the wash liquor on dissolution of the carboxylate chelating salt particularly during the first 60 seconds is within the range pH 7-11, preferably from 8-11.

The monomeric or oligomeric polycarboxylate chelating salt can constitute the sole detergent builder material in the detergent builder system for the purposes of the process of the present invention. However it is preferred that the polycarboxylate chelating salt forms one component of a multi component builder system which is present at from 10% to 60% of the detergent product. This multi component builder system will be free or substantially free of phosphorus containing builders (substantially free being herein defined to constitute less than 1 % of the total detergent builder system), and in preferred products will incorporate a mixture of water-soluble and water-insoluble builders.

The water insoluble builder can be an organic polymeric ion exchange material, examples being those disclosed in Budenheim DOS 2055423, Colgate BP 1181077 and Henkel DOS 2330026, but is more commonly an inorganic hydrated aluminosilicate material, more particularly a hydrated synthetic zeolite such as hydrated Zeolite A, X, B or HS.

Preferred aluminosilicate ion-exchange materials have the unit cell formula Mz [(A102)z (SiO2)y] xH20 wherein M is a calcium-exchange cation, z and y are at least 6; the molar ratio of z to y is from 1.0 to 0.5 and x is at least 5, preferably from 7.5 to 276, more preferably from 10 to 264. The aluminosilicate materials are in hydrated form and are preferably crystalline, containing from 10% to 28%, more preferably from 18% to 22% by weight of water.

The above aluminosilicate ion exchange materials are further characterised by a particle size diameter of from 0.1 to 10 micrometers, preferably from 0.2 to 4 micrometers. The term particle size diameter herein represents the average particle size diameter of a given ion exchange material as determined by conventional analytical techniques such as, for example, microscopic determination utilizing a scanning electron microscope. The aluminosilicate ion exchange materials are further characterised by their calcium ion exchange capacity, which is at least 200 mg equivalent of CaCO3 water hardness/g of aluminosilicate, calculated on an anhydrous basis, and which generally is in the range of from 300 mg eq./g to 352 mg eq./g. The aluminosilicate ion exchange materials herein are still further characterised by their calcium ion exchange rate which is at least 130 mg equivalent of CaCO3/litre/minute/(g/litre) (2 grains Ca+ ^/gallon/minute/(gram/gallon)) of aluminosilicate (anhydrous basis), and which generally lies within the range of from 130 mg equivalent of CaCO3/litre/minute/(gram/litre) (2 grains/gallon/minute/ (gram/gallon)) to 390 mg equivalent of CaCO3/litre/minute/ (gram/litre) (6 grains/gallon/minute/ (gram/gallon), based on calcium ion hardness. Optimum aluminosilicates for builder purposes exhibit a calcium ion exchange rate of at least 260 mg equivalent of CaCO3/litre/minute/(gram/litre) (4 grains/gallon/minute/(gram/gallon)).

Aluminosilicate ion exchange materials useful in the practice of this invention are commercially available and can be naturally occurring materials, but are preferably synthetically derived. A method for producing aluminosilicate ion exchange materials is discussed in US Patent No. 3,985,669. Preferred synthetic crystalline aluminosilicate ion exchange materials useful herein are available under the designation Zeolite A, Zeolite B, Zeolite X, Zeolite HS and mixtures thereof. In an especially preferred embodiment, the crystalline aluminosilicate ion exchange material is Zeolite A and has the formula Nai2[(A102)l2 (SiC>2)l23 xH2° wherein x is from 20 to 30, especially 27. Zeolite X of formula Nagg [(A102)86(SiO2)l06]-276 H2O is also suitable, as well as Zeolite HS of formula Na6[(A102)6(SiO2)6l H2O.

Other inorganic builder materials that can form part of the builder system for the purposes of the invention include alkali metal carbonates, bicarbonates and silicates.

For the purposes of assessing whether a product will provide the benefits of the invention, the builder system is subjected to the following model test.

The product concentration which is proposed to be used is selected and the amount of product that would be added to a particular type of front loading automatic washing machine is calculated, based on the normal volume of water that would be charged to that machine for the wash step of a mainwash cycle. A mixture of the builder components in the builder system is formed in individual amounts corresponding to those present at this product usage and the balance needed to provide a composition weight of 100g is made up with added alkali metal sulfate. The mixture of builder components and the alkali metal sulphate used as a ballast ingredient should result in a sodium ion concentration in solution not exceeding 20 millimoles/litre. Sodium ion concentrations above this limit can contribute to non-reproducibility in the values of residual Calcium ion in solution measured by the Calcium ion selective electrode.

This composition is added to an open topped 500ml plastic container. A 3 kg load of clean dry prewashed cotton sheets, together with a square terry towel swatch of 60cm side dimension located in the centre of the load is placed in the drum of the machine and the plastic container is placed upright on the fabrics. The reservoir and pipework of the machine are emptied of any water or wash liquor and the machine is then charged with its normal volume of a made-up hardness solution at a temperature of 15°C. This solution comprises distilled water containing 3.50 m moles/litre of Ca+ + ion and 0.98 m moles Mg+ + ion (i.e. 25.2° German Hardness at a Ca:Mg ratio of 3.6:1).

The machine is then started so as to provide rotary or oscillatory motion and stopped after 30 seconds (normally 2 tumbles). The swatch is removed from the machine, wrung out and the wrung-out liquid immediately filtered through a 0.1 micrometer sized filter before being analysed for residual free calcium and soluble builder components.

The residual free calcium ion in solution is measured by means of Calcium selective electrode. The Calcium ion selective electrode used in the model test method is Model 93-20 electrode, manufactured by Orion Research AG, Fahnlinbrunnen Strasse 3 CH 8700 Kusnacht Switzerland, and is coupled to a Model EA 940 autoanalyser sold by the same manufacturer.

For the purposes of the present invention the Residual Free Calcium level should be not more than 0.1 mmoles/litre after 30 seconds. Preferably the value should be no more than 0.06 m moles/litre and most preferably no more than 0.04 mmoles/litre.

Analysis for the level of soluble builder component is carried out by means of High Pressure Liquid Chromatography using standard techniques known to those skilled in the art. The monomeric or oligometric polycarboxylate chelating agent should attain a level of at least 80% of its equilibrium concentration within 45 seconds of the start of the rotation of the drum, preferably within 30 seconds and most preferably within 15 seconds of the start.

A wide range of surfactants can be used in the detergent compositions.

I 5 A typical listing of anionic, nonionic, ampholytic and zwitterionic classes, and species of these surfactants, is given in U.S.P. 3,664,961 issued to Norris on May 23, 1972.

Mixtures of anionic surfactants are particularly suitable herein, especially mixtures of sulfonate and sulfate surfactants in a weight ratio of from 5:1 to 1:2, preferably from 3:1 to 2:3, more preferably from 3:1 to 1:1. Preferred sulfonates include alkyl benzene sulfonates having from 9 to 15, especially 11 to 13 carbon atoms in the alkyl radical, and alpha-sulfonated methyl fatty acid esters in which the fatty acid is derived from a C12-C18 fatty source, preferably from a Ci6_Cj8 fatty source. In each instance the cation is an alkali metal, preferably sodium. Preferred sulfate surfactants are alkyl sulfates having from 12 to 18, preferably 16 to 18 carbon atoms in the alkyl radical, optionally in admixture with ethoxy sulfates having from 10 to 20, preferably 10 to 16 carbon atoms in the alkyl radical and an average degree of ethoxylation of 1 to 6. The cation in each instance is again an alkali metal cation, preferably sodium.

One class of nonionic surfactants useful in the present invention are condensates of ethylene oxide with a hydrophobic moiety to provide a surfactant having an average hydrophilic-lipophilic balance (HLB) in the range from 8 to 17, preferably from 9.5 to 13.5, more preferably from 10 to 12.5. The hydrophobic (lipophilic) moiety may be aliphatic or aromatic in nature and the length of the polyoxyethylene group which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.

Especially preferred nonionic surfactants of this type are the C9-C15 primary alcohol ethoxylates containing 3-8 moles of ethylene oxide per mole of alcohol, particularly the C14-C15 primary alcohols containing 6-8 moles of ethylene oxide per mole of alcohol and the C12-C14 primary alcohols containing 3-5 moles of ethylene oxide per mole of alcohol.

Another class of nonionic surfactants comprises alkyl polyglucoside compounds of general formula RO (CnH2n0)tZx wherein Z is a moiety derived from glucose; R is a saturated hydrophobic alkyl group that contains from 12 to 18 carbon atoms; t is from 0 to 10 and n is 2 or 3; x is from 1.3 to 4, the compounds including less than 10% unreacted fatty alcohol and less than 50% short chain alkyl polyglucosides. Compounds of this type and their use in detergents are disclosed in EP-B 0070074, 0070077, 0075996 and 0094118.

A further class of surfactants are the semi-polar surfactants such as amine oxides. Suitable amine oxides are selected from mono C8-C20. preferably C10-C14 N-alkyl or alkenyl amine oxides and propylene-1,3-diamine dioxides wherein the remaining N positions are substituted by methyl, hydroxy ethyl or hydroxypropyl groups.

Cationic surfactants can also be used in the detergent compositions herein and suitable quaternary ammonium surfactants are selected from mono C8-C16, preferably C10-C14 N-alkyl or alkenyl ammonium surfactants wherein remaining N positions are substituted by methyl, hydroxyethyl or hydroxypropyl groups.

Mixtures of surfactant types are preferred, more especially anionic-nonionic and also anionic-nonionic-cationic mixtures.

Particularly preferred mixtures are described in British Patent No. 2040987 and European Published Application No. 0087914. The detergent compositions can comprise from 1 %-70% by weight of surfactant, but usually the surfactant is present in an amount of from 1% to 20%, more preferably from 5-15% by weight.

The surfactants, and the water soluble and any insoluble builders can be combined in any way but it is preferred that the water soluble monomeric or oligomeric carboxylate chelating salt or salts be incorporated in a manner that permits their rapid dissolution when added to the wash water. Dry mixing of the water soluble carboxylate chelating salts with the other components of the composition is a preferred technique for promoting this rapid dissolution.

Preferred detergent compositions for use in the process of the invention also comprise at least two particulate multi ingredient components. The first component comprises at least 30%, usually from 30% to 70%, and more preferably from 40% to 60% by weight of the composition and the second component from 1% to 50%, more preferably from 10% to 40% by weight of the composition.

The first component comprises a particulate incorporating an anionic surfactant in an amount of from 0.75% to 30% by weight of the powder and one or more inorganic and/or organic salts in an amount of from 99.25% to 70% by weight of the powder. The particulate can have any suitable form such as granules, flakes, prills, marumes or noodles but is preferably granular. The granules themselves may be agglomerates formed by pan or drum agglomeration or by in-line mixers but are preferably spray dried particles produced by atomising an aqueous slurry of the ingredients in a hot air stream which removes most of the water. For illustrative purposes, the first component is described hereinafter as a spray dried powder as this constitutes a preferred embodiment of the invention.

The primary characteristic of the anionic surfactant in the first component is that it should have a low rate of solubility in aqueous media at the water temperatures that prevail during the fill step of the wash cycle in an automatic washing machine. These temperatures can range from 5°C to 60°C depending whether or not a 'cold fill' or a 'hot fill' is used. For continental European machines and low temperature wash cycles in UK machines, a 'cold fill' is employed in which the water temperature lies in the range from 5°C to 20°C, more usually from 7°C to 12°C.

'Hot fill' temperatures range from 35°C to 60°C, depending on the machine type and the wash cycle selected. With respect to European wash habits as a whole, 'cold filling' is by far the predominant practice.

Suitable anionic surfactants for the purposes of the first component have been found to be linear alkyl sulfate salts in which the alkyl group has from 15 to 22 carbon atoms, and linear alkyl carboxylate salts in which the alkyl group has an average of from 16 to 24 carbon atoms.

Alkyl groups for the alkyl sulfates may be derived synthetically as by OXO synthesis or olefin build-up but are preferably derived from natural fats such as tallow.

Shorter chain alkyl sulfates or carboxylates, in which the alkyl group is derived from sources comprising a mixture of alkyl moieties more than 40% of which contain 14 or less carbon atoms, are less suitable as they cause the first component to form a gel like mass during dissolution. The alkyl groups for the carboxylate salts may be derived synthetically in a similar manner but are also preferably derived from natural sources such as tallow fat or marine oils. The counterion for these salts may be any of the alkali or alkaline earth metals but is preferably sodium for reasons of cost.

The level of anionic surfactant in the spray dried powder forming the first component is from 0.75% to 25% by weight, more usually from 2.5% to 20%, preferably from 3% to 15% and most preferably from 5% to 12% by weight. Although other, more water-soluble anionic surfactants such as linear alkyl benzene sulfonates can be included in the spray dried powder it is preferred that such water soluble anionic surfactants only comprise a minor proportion of the total surfactant in the slurry that is spray dried. Water soluble surfactants such as anionic or nonionic surfactants may however be applied subsequently to the spray dried powder by spray on.

The other major ingredient of the spray dried powder is one or more inorganic or organic salts that provide the crystalline structure for the granules. The inorganic and/or organic salts may be water- soluble or water insoluble, the latter type being comprised by the, or the major part of the water-insoluble builders where these form part of the builder system. Suitable water soluble inorganic salts include the alkali metal carbonates, bicarbonates, sulfates and borates. Alkali metal silicates can also be present in the spray dried granule provided that aluminosilicate does not form part of the spray dried composition. The level of alkali metal silicate is preferably from 3% to 15% by weight. Suitable silicate solids have a molar ratio of SiO2/alkali metal 2O in the range from 1.0 to 3.3, more preferably from 1.5 to 2.4.

As mentioned above, where the builder system includes an insoluble aluminosilicate such as zeolite A, X or B, it is preferred that at least part of this be incorporated into the spray dried granule and in such products the zeolite and silicate should be kept separate, e.g. in different particulates. This can be achieved in several ways, e.g. by producing separate spray dried particulates, only one of which contains the silicate, or more preferably by adding the silicate as a dry mixed solid ingredient. Silicates with an SiO2/alkali metal 2θ ratio in the range 2.0 - 2.2 are most suitable for this purpose.

Any of the previously mentioned organic builder salts can also be incorporated in the spray dried powder forming the first component.

The spray dried powder can also include some or even all of the water soluble monomeric or oligomeric carboxylate chelating agent but the incorporation of all of this carboxylate chelating agent is less preferred as it tends to inhibit the rapid solution of this ingredient.

The organic and/or inorganic salts comprise from 65% to 90% by weight of the first component, more preferably from 70% to 90% and most preferably from 75% to 85% by weight.

The spray dried powder normally contains up to 15% by weight of miscellaneous ingredients and from 7% to 11% moisture, preferably no more than 10% by weight.

The miscellaneous ingredients include optional ingredients that normally form part of such products. Heavy metal ion chelating agents, anti redeposition and soil suspension agents, optical brighteners, anticaking agents, dyes and pigments are examples of such optional ingredients and can be added in varying amounts as desired.

Suitable heavy metal ion chelating agents include the organic phosphonates, amino polyalkylene phosphonates and amino polycarboxylates.

Antiredeposition and soil suspension agents suitable herein include cellulose derivatives such as methylcellulose, carboxymethylcellulose and hydroxyethylcellulose, and homo- or co-polymeric polycarboxylic acids or their salts. Agents of this type include the homo- or copolymeric polycarboxylic acids or their salts in which the polycarboxylic acid comprises at least two carboxyl radicals separated from each other by not more than two carbon atoms. Polymers of this type are disclosed in GB-A-1,596,756. Examples of such salts are polyacrylates of MWt 2000-5000 and their copolymers with maleic anhydride, such copolymers having a molecular weight of from 20,000 to 70,000, especially about 40,000. In addition copolymers of maleic anhydride with ethylene, methylvinyl ether or methacrylic acid can also be used, the maleic anhydride constituting at least 20 mole percent of the copolymer. These materials are normally used at levels of from 0.5% to 10% by weight, more preferably from 0.75% to 8%, most preferably from 1% to 6% by weight of the composition.

Preferred optical brighteners are anionic in character, examples of which are disodium 4,4l-bis-(2-diethanolamino-4-anilino -s- triazin-6ylamino)stilbene-2:2l disulphonate, disodium 4, 4l-bis(2-morpholino-4-anilino-s-triazin-6-ylaminostilbene- 2:2^disulphonate, disodium 4, 4^ - bis-(2,4-dianilino-s-triazin-6-ylamino) stilbene-2:2l - disulphonate, monosodium 4^,4^ -bis-(2,4-dianilinos-triazin-6 ylamino)stilbene-2-sulphonate, disodium 4,4^ -bis(2-anilino-4-(N-methy 1-N-2-hydroxyethylamino)-s-tria zin-6-ylamino) stilbene-2,2^ - disulphonate, disodium 4,4l -bis-(4-phenyl-2,l,3triazol-2-yl)-stilbene-2,2ldisulphonate, disodium 4,4lbis (2-anilino-4-(l-methyl-2-hydroxyethylamino)-s-triazin-6-ylamino) stilbene- 2,21 disulphonate and sodium 2(stilbyl-4l 1 - (naphtho-ll,2F4,5) -1,2,3 - triazole-2H-sulphonate .

In preferred compositions where the first component is a spray dried powder, optional ingredients included in the first component should be heat stable to the extent necessary to withstand the temperatures encountered in the spray drying process. Where spray dried powder forms the first component of detergent compositions used in the process of the invention it will normally be dried to a moisture content of from 7% to 11% by weight, more preferably from 8% to 10% by weight of the spray dried powder. Moisture contents of powders produced by other processes such as agglomeration may be lower and can be in the range 1-10% by weight.

The particle size of the powder is conventional in that the particles should be neither excessively coarse nor fine. Thus preferably not more than 5% by weight should be above 1.4 mm in maximum dimension while not more than 10% by weight should be less than 0.15 mm in size. Preferably at least 60% and most preferably at least 80% by weight of the powder lies between 0.7 mm and 0.25 mm in size. For spray dried powders, the bulk density of the particles can range from 350 g/litre to 650g/litre but conventionally lies in the range 540 to 600 g/litre. Bulk densities in the upper part of the range from 600-650 g/litre are particularly useful where production of so called concentrated products is desired. However, bulk densities above this range may be produced if processes other than spray drying are used and highly concentrated products are desired.

The second component of a preferred composition useful in the process of the invention is a particulate containing a water soluble surfactant.

This may be anionic, nonionic, cationic or semipolar in type or a mixture of any of these. Suitable surfactants are listed hereinbefore but preferred surfactants are linear C11-C15 alkyl benzene sulfonates ^12-^15 alkyl sulfates and fatty C14-C18 methyl ester sulfonates.

The second component may have any suitable physical form, i.e. it may take the form of flakes, prills, marumes, noodles, ribbons, or granules which may be spray-dried or non spray-dried agglomerates. Although the second component could in theory comprise the water soluble surfactant on its own, in practice at least one organic or inorganic salt is included to facilitate processing. This provides a degree of crystallinity, and hence acceptable flow characteristics, to the particulate and may be any one or more of the organic or inorganic salts present in the first component.

The particle size range of the second component is not critical but should be such as to obviate segregation from the particles of the spray dried first component when blended therewith. Thus not more than 5% by weight should be above 1.4 mm in maximum dimension while not more than 10% should be less than 0.15 mm in size.

The bulk density of the second component will be a function of its mode of preparation. Thus, in spray dried granular form the second component may have a density of from 350 g/litre to 650 g/litre but more preferably will be in the range from 500 g/litre to 630 g/litre.

The preferred form of the second component however is a mechanically mixed agglomerate which may be made by adding the ingredients dry or with an agglomerating agent to a pan agglomerator, Z blade mixer, or more preferably an in-line mixer such as those manufactured by Schugi (Holland) BV, 29 Chroomstraat 8211 AS, Lelystad, Netherlands and Gebruder Lodige Maschinenban GmbH, D-4790 Paderborn 1, Elsenerstrasse 7-9, Postfach 2050 F.R.G. By this means the second component can be given a bulk density in the range from 650 g/litre to 1190 g/litre more preferably from 750 g/litre to 850 g/litre. This is particularly useful in formulating the so-called 'concentrated' products.

Preferred compositions include a level of alkali metal carbonate in the second component corresponding to an amount of from 3% to 20% by weight of the composition, more preferably from 5% to 20% by weight. This will provide a level of carbonate in the second component of from 20% to 40% by weight.

A highly preferred ingredient of the second component is also a hydrated water insoluble aluminosilicate ion exchange material of the synthetic zeolite type, described hereinbefore, present at from 10% to 35 % by weight of the second component. The amount of water insoluble aluminosilicate material incorporated in this way is from 1 % to 10% by weight of the composition, more preferably from 2% to 8% by weight. If the second component is spray dried, it is important that it does not contain both silicate and aluminosilicate ingredients for the reasons stated hereinbefore. In such circumstances, the silicate may be incorporated in the first component or, if that also contains aluminosilicate, may be added as a solid, together with other dry mixed materials, to the first and second components.

In a particularly preferred embodiment, the second component is made by forming the surfactant salt in situ in an inline mixer. The liquid acid form of the surfactant is added to a mixture of particulate anhydrous sodium carbonate and hydrated sodium aluminosilicate and neutralised to form the surfactant salt whilst maintaining the particulate nature of the mixture. The resultant agglomerated mixture forms the second component which is then added to other components of the product.

Preferred compositions also incorporate one or more separately mixed ingredients in addition to the first and second particulate components.

Thus the compositions preferably contain one or more of particulate builders or chelating agents, inorganic peroxy bleaches, peroxy carboxylic acid precursors (bleach activators), suds suppressors, soil suspending agents, polymeric soil release agents, enzymes and photoactivated bleaches. The compositions may also contain fabric softening agents and dye materials.

The first of these separately mixed ingredients is the carboxylate chelating agent described hereinbefore, which in preferred compositions is incorporated in its entirety by dry mixing. The level of addition is from 5% to 25%, more preferably from 5% to 20% by weight of the composition.

Any particulate inorganic perhydrate bleach can be used, in an amount of from 3% to 40% by weight, more preferably from 8% to 25% by weight and most preferably from 12% to 20% by weight of the composition. Preferred examples of such bleaches are sodium perborate monohydrate and tetrahydrate and mixtures thereof.

Another preferred separately mixed ingredient is a peroxy carboxylic acid bleach precursor, commonly referred to as a bleach activator, which is preferably added in a prilled or agglomerated form.

Examples of suitable compounds of this type are disclosed in British Patent Nos, 1586769 and 2143231 and a method for their formation into a prilled form is described in European Published Patent Application No. 0062523. Preferred examples of such compounds are tetracetyl ethylene diamine and sodium 3,5,5 trimethyl hexanoyloxybenzene sulphonate.

Bleach activators are normally employed at levels of from 0.5% to 10% by weight, more frequently from 1% to 8% and preferably from 2% to 6% by weight of the composition.

Another optional ingredient is a suds suppressor, exemplified by silicones, and silica-silicone mixtures. Silicones can be generally represented by alkylated polysiloxane materials while silica is normally used in finely divided forms, exemplified by silica aerogels and xerogels and hydrophobic silicas of various types. These materials can be incorporated as particulates in which the suds suppressor is advantageously releasably incorporated in a water-soluble or water-dispersible, substantially non-surface-active detergent-impermeable carrier. Alternatively the suds suppressor can be dissolved or dispersed in a liquid carrier and applied by spraying on to one or more of the other components.

As mentioned above, useful silicone suds controlling agents can comprise a mixture of an alkylated siloxane, of the type referred to hereinbefore, and solid silica. Such mixtures are prepared by affixing the silicone to the surface of the solid silica. A preferred silicone suds controlling agent is represented by a hydrophobic silanated (most preferably trimethyl-silanated) silica having a particle size in the range from 10 nanometers to 20 nanometers and a specific surface area above 50 m^/g. intimately admixed with dimethyl silicone fluid having a molecular weight in the range from about 500 to about 200,000 at a weight ratio of silicone to silanated silica of from about 1:1 to about 1:2.

A preferred silicone suds controlling agent is disclosed in Bartollota et al. U.S. Patent 3,933, 672. Other particularly useful suds suppressors are the self-emulsifying silicone suds suppressors, described in German Patent Application DTOS 2,646,126 published April 28, 1977. An example of such a compound is DC-544, commercially available from Dow Corning, which is a siloxane/glycol copolymer.

The suds suppressors described above are normally employed at levels of from 0.01 % to 1.0% by weight of the composition, preferably from 0.1% to 0.7% by weight. While they can be incorporated into the first or second multi-ingredient components it is preferred that they be sprayed on to the components once the latter have been formed or alternatively formed into separate particulates that can then be mixed with the particulates of the invention. The incorporation of the suds modifiers as separate particulates also permits the inclusion therein of other suds controlling materials such as C20-C24 fatty acids, microcrystalline waxes and high MWt copolymers of ethylene oxide and propylene oxide which would otherwise adversely affect the dispersibility of the matrix. Techniques for forming such suds modifying particulates are disclosed in the previously mentioned Bartolotta et al U.S. Patent No. 3,933,672.

Other useful polymeric materials are the polyethylene glycols, particularly those of molecular weight 1000-10000, more particularly 2000 to 8000 and most preferably about 4000. These are used at levels of from 0.20% to 5% more preferably from 0.25% to 2.5% by weight. These polymers and the previously mentioned homo- or co-polymeric polycarboxylate salts are valuable for improving whiteness maintenance, fabric ash deposition, and cleaning performance on clay, proteinaceous and oxidizable soils in the presence of transition metal impurities.

Soil release agents useful in compositions of the present invention are conventionally copolymers or terpolymers of terephthalic acid with ethylene glycol and/or propylene glycol units in various arrangements. Examples of such polymers are disclosed in the commonly assigned US Patent Nos. 4116885 and 4711730 and European Published Patent Application No. 0272033. A particular preferred polymer in accordance with EP-A-0272033 has the formula (CH3(PEG)43)o.75(POH)0.25[T-PO)2.8(T-PEG)o.4] T(PO-H)0.25((PEG)43CH3)o.75 where PEG is-(OC2H4)0-,PO is (OC3H6O) and T is (pCOC6H4CO). - 28 Certain polymeric materials such as polyvinyl pyrrolidones typically of MWt 5000-20000, preferably 10000-15000, also form useful agents in preventing the transfer of labile dyestuffs between fabrics during the washing process.

Another optional ingredient useful in the present invention is one or more enzymes. Preferred enzymatic materials include the commercially availably amylases, neutral and alkaline proteases, lipases, esterases and cellulases conventionally incorporated into detergent compositions. Suitable enzymes are discussed in U.S. Patents 3,519,570 and 3,533,139.

Photoactivated bleaching materials are discussed in EP-A-57088, highly preferred materials being zinc phthalocyanine tri- and tetra-sulfonates, such materials being present at from 0.0005% to 0.01% by weight of the composition.

Fabric softening agents can also be incorporated into detergent compositions in accordance with the present invention. These agents may be inorganic or organic in type. Inorganic softening agents are exemplified by the smectite clays disclosed in GB-A-1,400,898.

Organic fabric softening agents include the water insoluble tertiary amines as disclosed in GB-A-1514276 and EP-B-0011340 and dilong chain amides as disclosed in EP-B-0242919. The combination of the above water insoluble tertiary amines with mono C12-C14 quaternary ammonium salts is disclosed in EP-B-0026527 & 528. Other useful organic ingredients of fabric softening systems include high molecular weight polyethylene oxide materials as disclosed in EP-A-0299575 and 0313146.

Levels of smectite clay are normally in the range from 5% to 15%, more preferably from 8% to 12% by weight with the material being added as a dry mixed component to the remainder of the formulation. Organic fabric softening agents such as the water-insoluble tertiary amines or dilong chain amide materials are incorporated at levels of from 0.5% to 5% by weight, normally from 1 % to 3% by weight whilst the high molecular weight polyethylene oxide materials and the water soluble cationic materials are added at levels of from 0.1% to 2%, normally from 0.15% to 1.5% by weight. These materials are normally added to the spray dried portion of the composition, although in some instances it may be more convenient to add them as a dry mixed particulate, or spray them as a molten liquid on to other solid components of the composition.

Compositions useful in the processes of the invention can be made via a variety of methods including dry mixing, spray drying, agglomeration and granulation and combinations of any of these techniques.

A preferred method of making the compositions involves a combination of spray drying, agglomeration in a high speed mixer and dry mixing.

A first granular component containing a relatively insoluble anionic surfactant is spray dried and part of the spray dried product is diverted and subjected to a low level of nonionic surfactant spray-on before being reblended with the remainder. A second granular component is made by dry neutralisation of an anionic surfactant acid using sodium carbonate as the neutralising agent in a continuous high speed blender such as a Lodige KM mixer. The first and second components together with other dry mix ingredients such as the carboxylate chelating agent, inorganic peroxygen bleach, bleach activator, soil suspension agent, silicate and enzyme are then fed to a conveyor belt from which they are transferred to a horizontally rotating drum in which perfume and silicone suds suppressor are sprayed on to the product. In highly preferred compositions, a further drum mixing step is employed in which a low (approx. 2%) level of finely divided crystalline aluminosilicate is introduced to increase density and improve granular flow characteristics.

In order to obtain a transient localised high concentration of water soluble carboxylate chelating agent in the wash liquor immediately surrounding the soiled fabric load in the machine drum, the detergent composition must be delivered directly to the drum and not indirectly via the outer casing of the machine. This can most easily be achieved by incorporation of the composition in a bag or container from which it is rapidly releasable at the start of the wash cycle in response to agitation, a rise in temperature or immersion in the wash water in the drum. Alternatively the washing machine itself may be adapted to permit direct addition of the composition to the drum e.g. by a dispensing arrangement in the access door.

Products comprising a detergent composition enclosed in a bag or container are usually designed in such a way that container integrity is maintained in the dry state to prevent egress of the contents when dry, but are adapted for release of the container contents on exposure to a washing environment, normally on immersion in an aqueous solution.

Usually the container will be flexible, such as a bag or pouch. The bag may be of fibrous construction coated with a water impermeable protective material so as to retain the contents, such as is disclosed in European published Patent Application No. 0018678. Alternatively it may be formed of a water insoluble synthetic polymeric material provided with an edge seal or closure designed to rupture in aqueous media as disclosed in European published Patent Application Nos. 0011500, 0011501, 0011502, and 0011968. A convenient form of water frangible closure comprises a water soluble adhesive disposed along and sealing one edge of a pouch formed of a water impermeable polymeric film such as polyethylene or polypropylene.

In a variant of the bag or container product form, laminated sheet products can be employed in which a central flexible layer is impregnated and/or coated with a composition and then one or more outer layers are applied to produce a fabric-like aesthetic effect. The layers may be sealed together so as to remain attached during use or may separate on contact with water to facilitate the release of the coated or impregnated material.

An alternative laminate form comprises one layer embossed or deformed to provide a series of pouch-like containers into each of which the detergent components are deposited in measured amounts, with a second layer overlying the first layer and sealed thereto in those areas between the pouch-like containers where the two layers are in contact. The components may be deposited in particulate, paste or molten form and the laminate layers should prevent egress of the contents of the pouch-like containers prior to their addition to water. The layers may separate or may remain attached together on contact with water, the only requirement being that the structure should permit rapid release of the contents of the pouch-like containers into solution. The number of pouch-like containers per unit area of substrate is a matter of choice but will normally vary between 500 and 25,000 per square metre.

Suitable materials which can be used for the flexible laminate layers in this aspect of the invention include, among others, sponges, paper and woven and non-woven fabrics.

However the preferred means of carrying out the process of the invention is to introduce the composition into the liquid surrounding the fabrics that are in the drum via a reusable dispensing device having walls that are permeable to liquid but impermeable to the solid composition.

Devices of this kind are disclosed in European Patent Application Publication Nos. 0343069 & 0343070. The latter Application discloses a device comprising a flexible sheath in the form of a bag extending from a support ring defining an orifice, the orifice being adapted to admit to the bag sufficient product for one washing operation in a washing cycle. A portion of the washing medium flows through the orifice into the bag, dissolves the product, and the solution then passes outwardly through the orifice into the washing medium. The support ring is provided with a masking arrangement to prevent egress of wetted, undissolved, product, this arrangement typically comprising radially extending walls extending from a central boss in a spoked wheel configuration, or a similar structure in which the walls have a helical form.

The invention is illustrated in the following non limiting Examples, in which all percentages are on a weight basis unless otherwise stated.

In the detergent compositions, the abbreviated component identifications have the following meanings:.

Cj2 LAS Sodium linear Cj2 alkyl benzene TAS sulfonate Sodium tallow alcohol sulfate C14/15 AS : Sodium C14-C15 alkyl sulfate TAEn Tallow alcohol ethoxylated with n moles of ethylene oxide per mole of alcohol 45E7 A C14-C15 predominantly linear primary alcohol condensed with an average of 7 moles of ethylene oxide CnAE£6.5 A Cj2-Ci3 primary alcohol condensed with 6.5 moles of ethylene oxide. PEG Polyethylene glycol (MWt normally follows) TAED Tetra acetyl ethylene diamine ISONOBS : Sodium 3,5,5 trimethyl hexanoyl oxybenzene sulphonate Silicate : Sodium silicate having an SiO2:Na2O ratio of l.6 (# ratio of 2.0:1) Sulphate : Anhydrous sodium sulfate (*Potassium salt) Carbonate : Anhydrous sodium carbonate (*Potassium salt) CMC : Sodium carboxymethyl cellulose Zeolite A : Hydrated Sodium Aluminosilicate of formula Naj2(AlO2SiO2)i227H2O having a primary particle size - the range from 1 to 10 micrometers Polyacrylate : Homopolymer of acrylic acid of MWt 4000 Citrate : Sodium citrate dihydrate (*Potassium salt) Silicone Prill : Comprising 0.14 parts by weight of an 85:15 by weight mixture of silanated silica and silicone, granulated with 1.3 parts of sodium tripolyphosphate, and 0.56 parts of tallow alcohol condensed with 80 molar proportions of ethylene oxide. MA/AA : Copolymer of 1:4 maleic/acrylic acid, average molecular weight about 80,000. MVEMA : Maleic anhydride/vinyl methyl ether copolymer, believed to have an average molecular weight of 240,000. This material was prehydrolysed with NaOH before addition. - 35 - Perborate : Sodium perborate tetrahydrate of nominal formula NaBO2.3H2O.H2O2 Perborate monohydrate : Anhydrous sodium perborate bleach empirical formula NaBO2-H2O2 Enzyme Mixed proteolytic and amylolytic enzyme sold by Novo Industrie AS. Brightener : Disodium 4,4'-bis(2-morpholino-4- anilino-s-triazin-6-ylamino) stilbene-2:2' -disulphonate. DETPMP Diethylene triamine penta (methylene phosphonic acid), marketed by Monsanto under the Trade name Dequest 2060 Mixed Suds Suppressor; 25% paraffin wax Mpt 50°C, 17% hydrophobic silica, 58% paraffin oil.

Example 1 A product having the composition given below was used to wash fabrics in a Miele 756W automatic washing machine using a 30°C mainwash programme C12LAS 3.50 TAS 3.25 45E7 5.00 Zeolite 22.50 Citrate 10.57 MA/AA 3.60 Silicate# 5.00 Carbonate 16.50 DEDPMP 0.20 CMC 0.80 Perborate 10.00 PerborateMonohydrate 12.6 TAED prill(85 % active) 5.3 PEG 4000 2.00 Enzyme 2.00 Brightener 0.25 Perfume & Misc. 0.45 Na Sulfate 27.6 Moisture to 100 A series of experiments was carried out to determine the citrate concentration after various time intervals. On each occasion the machine was loaded with 3 kg of dry clean cotton sheets together with a square terry towelling swatch having a side length of 60 cms, the swatch being located within the load. 98g of a composition comprising 10.57g citrate, 28.50g Zeolite, 16.5g carbonate, 5.3g TAED prills, 12.6g Perborate monohydrate, 4.9g silicate and 27.6g sulfate was added to a 500 ml plastic beaker and placed on top of the sheets in the washer drum.

The machine was charged with 15 litres of a Hardness solution of temperature 15°C having a mineral Hardness of 22° German Hardness with a 3:1 Ca:Mg ratio, thereby giving an equilibrium product concentration of 0.65% by weight at a pH of 10.4.

The machine was then started and stopped at a particular time interval after the initial rotary movement commenced. The swatch was removed and wrung out and the residual liquor filtered through a 0.1 micrometer filter. (An Anotop 25 Disposable Syringe Filter manufactured by Anotec Separations Ltd., Wildmere Road, Daventry Road Industrial Estate, Banbury, Oxfordshire, England.) Analysis of the level of citrate in solution after 15 seconds and 30 seconds gave values of 1.9 m moles/litre and 2.1 m moles/litre respectively, approximately 82% and 88% of the equilibrium concentration that would arise on uniform dispersion of the product in the entire wash water charged to the machine.

In a corresponding test in which the same product was introduced via the mainwash detergent compartment of the dispenser drawer, the residual levels of citrate in solution were only 1.06 m mole/litre, at each time interval, i.e. 45% of the equilibrium concentration.

Example 2 A study was made of the rate of calcium ion depletion from a wash solution into which a detergent composition containing a mixture of a water insoluble detergent builder (Zeolite A) and a water soluble monomeric polycarboxyate chelating agent (Potassium citrate) was introduced via two different techniques. In each instance, a Miele IE 91105b 756W recirculating washing machine was loaded with 3 kg of clean dry cotton fabric together with a cotton terry towelling swatch of side length 60 cm.

The formulation of the detergent composition was as follows:- % active % by weight Citrate* 8 8.5 Zeolite A 22 27.5 TAED 5 5.8 Perborate monohydrate 12.5 12.5 Carbonate* 21.5 21.5 Silicate# 3.5 4.38 Sulphate* 19.8 total g 100 In one method lOOg, of the composition was added via the detergent compartment in the dispensing drawer, and in the other a dispensing device constructed in accordance with EP-A-0343070 was charged with lOOg of the mixture and placed in the washing machine drum. A 30°C mainwash cycle was then commenced and approximately 15 litres of water at 15°C and 25° Hardness (Ca:Mg = 3:1) was fed to the machine in the conventional manner (i.e. via the dispensing compartment). A sample of wash liquor was then taken from the wash drum by stopping the machine, removing the swatch, wringing it out, filtering the extracted liquor through a 0.1 micrometer pore filter and analysing the filtrate for residual Calcium ion in solution using the Ca+ + ion selective electrode described hereinbefore.

The results are shown below Dispensing Device Dispensing Drawer Residual Ca++ level Residual Ca++ level Time (secs) M Mols/ litre % of starting cone. M Mols/ litre % of starting cone. 0 3.50 100 3.58 100 15 0.04 1 0.26 7 30 0.03 <1 0.30 8 45 na na 0.30 8 120 0.04 1 0.14 4 It can be seen that a builder system incorporating a water soluble polycarboxylate chelating agent produces far lower levels of residual Calcium ion in the wash drum when delivered using the process of the present invention than when delivered from the conventional dispensing drawer.

Example 3 A comparison was made of the detergency performance of the formulation of Example 1 introduced into a Miele 756W washing machine by the two methods employed in Example 2.

The comparison was carried out at 30°C and 60°C using water of 25° German Hardness (Ca:Mg = 3:1). Each wash load comprised 3 Kg of mixed cotton fabrics (tea towels, terry towels, bed sheets) together with a swatch bearing a range of specific stains. The overall cleaning of representative articles (tea towels) from each load was assessed visually by set of four expert panellists using a five point Scheffe scale.

The results are expressed below in terms of an overall percentage preference for the cleanliness of the load washed in accordance with the method of the invention relative to that washed using the prior art technique.

°C 60°C 55/45 77/23 It can be seen that the method of the invention resulted in a superior cleaning end result at both temperatures, with the superiority at 60°C being statistically significant at the 95% confidence level.

The comparison of the cleaning of the specific stains showed a similar advantage for the method in accordance with the invention. Cleaning of these stains was again assessed by an expert panel using a five point Scheffe scale and the results are shown below in panel score units normalised to give a prior art score of zero.

Lipstick 1.1 0.9 Shoe Polish 1.1* 0.4 Blood 1.8* n.a. Tea 0.6 0.3 The starred results indicate statistical significance at the 95 % level of confidence

Claims (11)

Claims

1. A process of washing fabrics in an automatic washing machine comprising a perforated container rotatable about a horizontal axis within an outer vessel serving as a wash liquor reservoir, said method comprising the steps of a) placing a load of soiled fabrics within said perforated container; b) charging said outer vessel with water such that the depth of water within the perforated container is no greater than two thirds of the internal radius thereof; c) commencing mechanical agitation of the fabrics by oscillatory and/or rotary motion of the perforated container; d) simultaneously with, or immediately after step 3), contacting the fabrics in the perforated container with a detergent product comprising from 3% to 30% by weight of an organic surfactant and from 10% to 60% of a detergent builder system comprising a water soluble monomeric or oligomeric carboxylate chelating agent; e) removing the soil-containing wash liquor from said outer vessel; and f) treating said washing fabrics with rinse water to extract residual wash liquor therefrom wherein step d) comprises contacting the fabrics with an amount of said product to give an equilibrium product concentration of from 0.5% to 2.0% by wt of the water in such a manner that said water soluble monomeric or oligomeric carboxylate chelating salt develops a transient concentration in the liquor at a -42pH of from 7 to 11 within said perforated container after not more than 45 seconds after the commencement of step (c), of at least 80% of the equilibrium concentration that would be reached in the volume of water charged to the machine, said builder system being such that; in a test in which 3 kg of unsoiled cotton fabric is contacted in the same machine in the same manner as in step (d) with lOOg of a composition comprising an amount of the builder system, bleach and buffer salt components corresponding to that in the product at the usage level employed in step (d) ballasted with neutral inorganic salts, the machine being charged with mineral hardness solution, comprising 3.5 m moles/litre Ca+ + and 0.98 m moles/litre Mg+ + in distilled water at 15°C, in an amount corresponding to the amount of water charged to the machine in step (b), the level of free Ca+ + ions in the liquor within the container is reduced to no more than 0.1m moles/litre within 30 seconds of the commencement of the first oscillatory or rotary motion of the perforated container.

2. A process according to claim 1 wherein said monomeric or oligomeric carboxylate chelating salt develops a transient concentration in the liquor within said perforated container of at least 80% of the equilibrium concentration 30 seconds of the start of the first rotary or oscillatory motion of the perforated container. -433.

3.A process according to either one of claims 1 & 2 wherein the concentration of the water soluble monomeric or oligomeric carboxylate chelating salt reaches a transient value of at least 80% of the equilibrium concentration within 15 seconds of the start of the first rotary or oscillatory motion of the perforated container.

4. A process according to any one of claims 1-3 wherein the level of free Ca+ + ions is reduced to no more than 0.06 m moles/litre, preferably no more than 0.04 mmoles/litre within 30 seconds of the commencement of the first rotary or oscillatory motion of the perforated container.

5. A process according to any one of claims 1-4 in which the water soluble monomeric carboxylate chelating salt is an alkali metal salt of citric acid or a mixture thereof with citric acid.

6. A process according to any one of claims 1-5 wherein the water soluble monomeric or oligomeric carboxylate chelating salt forms one component of a multi component builder system.

7. A process according to claim 6 wherein another component of the builder system is a water insoluble ion exchange material.

8. A process according to either one of claims 6 & 7 in which the water insoluble ion exchange material is a synthetic aluminosilicate having the formula Na z ((A102) z (Si02^y) x H2O wherein z and y are integers of at least 6, the molar ratio of z to y -44is in the range from 1.0 to 0.5, x is an integer from 15 to 264 such that the moisture content is from 10% to 28% by weight, said aluminosilicate ion exchange material having a primary particle size of from 0.1 to 10 microns, a calcium ion exchange capacity of at least 200 meg/g and a calcium ion exchange rate of at least 2 grains/minute/gram.

9. A process according to any one of claims 1-8 wherein the pH of the wash liquor within the drum during the first 60 seconds is within the range from 7 to 11.

10. A process according to any one of claims 1-9 wherein step d) comprises releasing the detergent product from within a reusable dispensing device placed in the perforated container with the load of soiled fabrics.

11. A process according to claim 10 wherein the device comprises a flexible sheath in the form of a bag secured to, and extending from, a support ring defining an orifice, the orifice being adapted to admit to the bag sufficient product for one washing cycle in the washing machine and to remain at least partially open during the washing cycle, such that a portion of the washing medium flows through the orifice into the bag, dissolves the product and the solution then passes outwardly through the orifice into the washing medium, the support ring being provided with masking means to prevent egress of wetted undissolved product. -4513. 14. 15. 16 . 17 . 13. 14. 15. 16 . 17 . A granular detergent composition when used in a process according to any one of the preceding claims comprising from 3 % to 20% by weight of the composition of an organic surfactant selected from anionic, nonionic and cationic surfactants, and from 10% to 60% by weight of the composition of a detergent builder system comprising a water soluble monomeric or oligomeric polycarboxylate chelating salt, together with a mixture of a water insoluble aluminosilicate zeolite selected from Zeolite A, Β, X or HS, and one or more of a water-soluble builder selected from alkali metal carbonates, bicarbonates and silicates. A granular detergent composition according to claim 12 incorporating an oxygen bleach. A granular detergent composition according to claim 13 wherein the oxygen bleach is an inorganic perhydrate. A granular detergent composition according to claim 14 further incorporating a peroxycarboxylic acid bleach precursor. A process according to claim 1, substantially as hereinbefore described and exemplified. A granular detergent composition according to claim 12, substantially as hereinbefore described and exemplified .