EP2688995A1

EP2688995A1 - Method of cleaning laundry

Info

Publication number: EP2688995A1
Application number: EP12708849.0A
Authority: EP
Inventors: Ian Howell; Anthony Mckee
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2011-03-22
Filing date: 2012-03-15
Publication date: 2014-01-29
Anticipated expiration: 2032-03-15
Also published as: ES2620244T3; AU2012230538A1; BR112013024145B1; AU2012230538B2; CN103502413B; EP2688995B1; ES2620244T8; BR112013024145A2; ZA201307327B; PL2688995T3; WO2012126801A1; CA2830287A1; CN103502413A

Abstract

The present invention provides a method of cleaning laundry, comprises the steps of: (I) pre-treating the laundry with a liquid pre-treatment composition; and (II) washing the thus-pre-treated laundry in a wash liquor comprising a main wash detergent formulation, preferably a main wash detergent powder. The liquid pre-treatment composition used in said method comprises (a) 0.005 to 20 wt% hydroxamate and (b)3 to 80 wt% of detersive surfactant system,wherein the weight ratio a) to b) lies in the range 6: 1to 1:16000, preferably 1:10 to 1:400. It was found that enhanced detergency, in particular with respect to particulate soils stains removal, can be obtained when applying the method of the present invention.

Description

Method of cleaning laundry

Field of the invention

The present invention relates to the use of hydroxamic acid and its corresponding salts in laundry detergent compositions with low levels of zeolite and phosphate builder, leading to

improved detergency and stain removal.

Background of the invention

Improvement of stain removal is one of the constant goals of the detergent industry, as this may lead to savings on the use of chemicals in detergent compositions, or may lead to washing at lower temperatures, and/or for shorter times, and therewith saving energy. Therefore, there is still an interest to improve the detergency effect, especially the primary detergency effect of laundry detergent compositions on textile stains, for example particulate stains, such as stains comprising soils or clay, or plant based stains, such as grass. Especially

particulate stains are difficult to remove during the

laundering process.

Hydroxamic acids are a class of chemical compounds in which a hydroxylamine is inserted into a carboxylic acid. The general structure of a hydroxamic acid is the following:

o Formula 1 in which R is an organic residue, for example alkyl or

alkylene groups. The hydroxamic acid may be present as its corresponding alkali metal salt, or hydroxamate. The hydroxamates may conveniently be formed from the corresponding hydroxamic acid by substitution of the acid hydrogen atom by a cation:

(Formula 2)

L⁺ is a monovalent cation such as for example the alkali metals (e.g. potassium, sodium), or ammonium or a substituted

ammonium.

Hydroxamic acids and hydroxamates are known to be useful as metal chelators. They have also been used in detergent

compositions in order to improve bleaching performance, as well as use as a builder substance.

EP 388 389 A2 discloses bleach free under built liquid

detergent compositions containing hydroxamic acids and their derivatives which assist in the removal of bleachable wine stains from fabrics during laundering. Hydroxamic acids as in formula 1 are disclosed, wherein R¹ represents an optionally substituted straight- or branched chain C5- C21 alkyl or C5- C21 alkenyl group or an optionally-substituted phenyl group, and R^' represents hydrogen, or an optionally substituted C1-C6 alkyl group, or an optionally-substituted phenyl group. One of the examples shows an improved bleaching performance when a

hydroxamate is used in a detergent composition in hard water (20° German hardness, which is about 143 milligram calcium per litre) . The examples use C12 linear, C12 branched, C13 branched and Cis hydroxamates in detergent formulations comprising mixtures of anionic surfactant and nonionic surfactant. In examples I, II and IV there is an excess of nonionic surfactant of at least 1.25 to 1 and in example III there is 100% anionic surfactant. The liquids also contain at least 6 wt% ethanol, which assists in solubilising the long chain hydroxamates

EP 384 912 A2 discloses the use of hydroxamic acids and their derivatives as stabilizers for peroxygen bleach compounds in built, mainly granular, detergent compositions. Fully

formulated detergent powder examples with 20 wt% zeolite used Ci2, Ci3 and C₁2 branched hydroxamates. Ci₈ was also used.

US 4,874,539 discloses polymeric carboxy hydroxamic acids useful as detergent additives, especially as metal ion

chelating agents, and also leading to improved tea stain removal from a test cloth, as compared to a detergent powder without a metal ion chelating agent.

US 4,863,636 discloses liquid detergent compositions comprising one or more detersive surfactants and one or more of N- hydroxyimide or carboxy hydroxamic acid detergent additives. These compounds serve as active metal ion chelants, leading to improved stain removal. WO 97/48786 discloses a multicomponent system for use with detergent substances, containing an oxidation catalyst, a suitable oxidant, at least one mediator that has been selected from the group of, among others, hydroxamic acids and

hydroxamic acid derivatives, a co-mediator, and optionally a low quantity of at least one free amine of each inserted mediator. This system leads to improved bleach function of the detergent, and less consumption of a mediator. GB 1317445 discloses detergent compositions comprising an alkali-metal salt of a hydroxamic acid. The function of this salt is to prevent the corrosion of copper and copper alloys that is utilised in the construction of the washing machines.

Copending patent application PCT/EP2009/067193 describes laundry detergent formulations comprising 0.5 to 20% by weight hydroxamic acid or its corresponding hydroxamate having a structure as specified therein. It is also shown in this document that the primary detergent effect, especially on red clay particulate soil, can be improved when applying these laundry detergent formulations for treating soiled fabric.

It is known that this beneficial detergent effect cannot be obtained when using the hydroxamic acid or its corresponding hydroxamate in a fully built detergent in particular when the builder mainly contains zeolite and/or phosphate and/or

carbonate builder.

In this connection, it is an object of the present invention to provide an effective method for cleaning fabric wherein both a fully built detergent formulation and hydroxamic acid or its corresponding hydroxamate are used.

It has now surprisingly been found that this object could be achieved by a method of cleaning fabric comprising a

pretreating step followed by a main wash step whereby the hydroxamic acid is used in the pre-treatment step and the fully built detergent formulation, preferably a fully built detergent powder, is applied in the main wash step. Definition of the invention

Accordingly, in a first aspect the present invention provides a method of cleaning laundry, wherein said method comprises the steps of: (I) pre-treating the laundry with a liquid pre-treatment composition; and

(II) washing the thus-pre-treated laundry in a wash liquo comprising a main wash detergent formulation, preferably wash detergent powder,

wherein the liquid pre-treatment composition comprises:

(a) 0.005 to 20 wt% hydroxamic acid or its corresponding hydroxamate of the structure

o

wherein R is a straight or branched C4- C20 alkyl, or a

straight or branched substituted C4- C20 alkyl, ora straight or branched C4- C20 alkenyl, or a straight or branched substituted C4- C20 alkenyl, or an alkyl ether group CH₃ (CH₂)_n (EO)_m wherein n is from 2 to 20 and m is from 1 to 12, or a substituted alkyl ether group CH₃ ( CH2 ) _n (EO)_m wherein n is from 2 to 20 and m is from 1 to 12, and

the types of substitution include one or more of -N¾, -OH, -S-, -0-, -COOH, and

and R² is selected from hydrogen and a moiety that forms part of a cyclic structure with a branched R¹ group,

b) 3 to 80 wt% of detersive surfactant system comprising anionic nonionic, cationic zwitterionic surfactant or a

combination thereof, wherein the weight ratio a) to b) lies in the range 6: 1 to 1:16000, preferably 1:10 to 1:400, and c) optionally, other ingredients to 100 wt% provided that zeolite, phosphate and carbonate builders are present at less than 5 wt% and ethanol is present at a level of less than 5 wt% . It should be understood that references to a number of carbon atoms include mixed chain length materials provided that some of the hydroxamate material falls within the ranges specified and the ratios and amounts are determined by excluding any material falling outside of the specified range.

Soap is not included in the calculation of anionic surfactant amounts and ratios.

However, the pre-treatment composition may comprise from 1 to 15 wt% soap. The preferred soaps are made from saturated fatty acids .

It is undesirable to have ethanol present at all as it is an explosion hazard during manufacture, and subsequently. If a high level of surfactant is present, it is desirable to seek alternative hydrotrope systems. We prefer a hydrotrope system comprising propylene glycol and glycerol at levels of at least 6 wt%, more preferably at least 10 wt%. The preferred hydroxamates are those where R² is Hydrogen and R¹ is Cs to Ci alkyl, preferably normal alkyl, most preferably saturated .

Especially preferred pre-treatment compositions comprise at least 0.5 wt% of soil release polymer. This improves the multi wash performance of the detergent system for the removal of the clay. Inclusion of at least 0.5 wt% anti redeposition polymer is also beneficial due to the very high efficiency of primary detergency soil removal meaning that there is an increased level of soil in the wash liquor (particularly in step I of the method) , which must then be prevented from redeposition onto the same or a different piece of fabric. In the pre-treatment composition, the preferred weight ratio of hydroxamate to detersive surfactant system for optimum

particulate red clay soil removal lies in the range 1:10 to 1 : 100.

Preferably the pre-treatment composition used in the method of the invention comprises a surfactant system including nonionic and anionic surfactant whereby the level of anionic surfactant is 50 to 95 wt% based on the total weight of the surfactant system.

Said surfactant system can also suitably contain two different types of anionic surfactant of which the weight ratio lies in the range of 80:20 to 20:80. In such surfactant system, a first type of anionic surfactant is preferably alkyl benzene

sulphonate and the second type of anionic surfactant is

preferably selected from the group consisting of alkyl ether sulphate, alkyl sulphate and alkyl carboxylate. More

preferably, the second type of anionic surfactant is an alkyl ether sulphate.

The pre-treatment compositions used in the method of the invention are particularly suitable for use on particulate stains such as soils and clays, especially red clay, and also surprisingly grass. Therefore, in a second aspect, the present invention provides the use of a pre-treatment composition applied in the invention for the removal of particulate soils, preferably red clay, most preferably Georgia clay, from

polyester and cotton fabrics. Furthermore, in a third aspect, the present invention provides the use of 0.005 to 20% by weight hydroxamic acid or its corresponding hydroxamate of the structure C /OH

R1 N

R²

wherein R¹ is a Cs -C1 normal alkyl group, and R² is a hydrogen atom, in a laundry pre-treatment composition, for improving the particulate soils stain removal from a textile substrate, wherein the pre-treatment composition further comprises from 3 to 80 wt% of a detersive surfactant system; and optionally other ingredients to 100 wt% provided that zeolite, phosphate and carbonate builders are present at less than 5 wt%, and wherein the pre-treated fabrics are washed in a wash liquor comprising a main wash detergent formulation, preferably a main wash detergent powder, including surfactant and more than 15% by weight builder.

Detailed Description of the Invention

Whenever either the term hydroxamic acid' or hydroxamate' is used in this specification, this encompasses both hydroxamic acid and the corresponding hydroxamate (salt of hydroxamic acid), unless indicated otherwise. All percentages mentioned herein are by weight calculated on the total composition, unless specified otherwise. The

abbreviation ^xwt%' is to be understood as % by weight of the total composition. The stained fabric is treated with the liquid laundry pre- treatment composition comprising hydroxamate according to the invention and the primary detergency is the measured stain removal by the laundry composition on the stain. This is a separate process to so-called soil release using a polymer, which is treatment of fabric with a polymer (through a wash or other such treatment) , with subsequent staining of the fabric, the soil release polymer having the effect of the easier removal of the stain.

The following definitions pertain to chemical structures, molecular segments and substituents :

Molecular weights of monomers and polymers are expressed as weight average molecular weights, except where otherwise specified.

The textile/ fabric substrates used can be any typical

textile/ fabric substrate, such as cotton (woven, knitted & denim) , polyester (woven, knitted & micro fibre) , nylon, silk, polycotton (polyester/cotton blends), polyester elastane, cotton elastane, viscose rayon, acrylic or wool. Particularly suitable textile/ fabric substrates are cotton, polycotton and polyester substrates.

Particulate stains are stains comprising for example dirt, soil, clay, mud or soot. They are predominately solid in nature and come into contact with fabrics in the course of their regular use.

Hydroxamic acid and derivatives

The general structure of a hydroxamic acid in the context of the present invention has been indicated in formula 3, and R¹, is as defined above. When R¹, is an alkyl ether group CH₃ (CH₂)_n (EO)_m wherein n is from 2 to 20 and m is from 1 to 12 then the alkyl moiety terminates this side group. Preferably, R¹ is chosen from the group consisting of C , C5, Ce, C₇, C₈, C9, C₁₀, C₁₁, or C₁₂ or C1 normal alkyl group, most preferably R¹ is at least a Cs-i normal alkyl group. When the Cs material is used this is called octyl hydroxamic acid. The potassium salt is particularly useful.

octano drcixainic acid K salt

However, other hydroxamic acids, whilst less preferred, are suitable for use in the present invention. Such suitable compounds include, but are not limited to, the following compounds :

Lysine Hyd roxamate*HCI

Methionine Hydroxamate Norvaline Hydroxamate

Such hydroxamic acids are commercially available.

Without wishing to be bound by theory, we believe that the hydroxamate acts by binding to metal ions that are present in the soil on the fabric. This binding action, which is, in effect, the known sequestrant property of the hydroxamate is not, in itself, of any use to remove the soil from the fabric. The key is the "tail" of the hydroxamate i.e. the group R¹ minus any branching that folds back onto the amate Nitrogen via group R . The tail is selected to have an affinity for the surfactant system. This means that the soil removal ability of an already optimised surfactant system is further enhanced by the use of the hydroxamate as it, in effect, labels the

difficult to remove particulate material (clay) as "soil" for removal by the surfactant system acting on the hydroxamate molecules now fixed to the particulates via their binding to the metal ions embedded in the clay type particulates. The detersive surfactants will adhere to the hydroxamate, leading overall to more surfactants interacting with the fabric, leading to better soil release. Therewith the hydroxamic acids act as a linker molecule facilitating the removal and

suspension of the particulate soil from the fabric into a wash liquor and thus boosting the primary detergency.

This enhancing of the primary detergency of surfactant systems is especially relevant when using a concentrated liquid pre- treatment detergent compositions having a relatively low pH (7.5-8) as compared to traditional laundering processes with particulate detergent compositions (pH 9-10.5) . The lower pH during the laundry pre-treatment process with liquid detergent compositions may lead to reduced soil release, as the surface charges of the soils are less negative as compared to the higher pH during the conventional well built and buffered laundering processes, achieved with conventional zeolite or phosphate built powder products. This surface charge of the soil may lead to increased repellence of the surfactants by the soil, possibly leading to reduced release of the soil. Hence, in the method of the invention the hydroxamates are used in a liquid laundry pre-treatment composition, and more preferred the detersive surfactant concentration in said liquid pre- treatment composition is from 20 to 80 wt%. The hydroxamates have a higher affinity for transition metals, like iron, than for alkaline earth metals like calcium and magnesium, therefore the hydroxamic acid primarily acts to improve the removal of soil on fabric, especially particulate soils, and not additionally as a builder for calcium and magnesium. This selectively is especially beneficial if the laundering composition is underbuilt; especially when it comprises less than 5 wt% zeolite or phosphate builder. Surfactants

The pre-treatment laundry detergent composition in which the hydroxamate is used comprises a detersive surfactant system at a concentration from 3 to 80 wt%. By a detersive surfactant system, we mean that the surfactants therein provide a

detersive, i.e. cleaning effect to textile fabrics treated as part of a laundering process. Other surfactants, which are not detersive surfactants, can be used as part of the composition.

Preferably, the detersive surfactant is present at a level of from 5 to 60 wt%, more preferably from 10 to 50 wt%. Even more preferably, the detersive surfactant system comprises at least

20, or 30 or even 40 wt% of the composition.

In general, any surfactant may be used as detersive

surfactants, including anionic, nonionic, cationic, and amphoteric or zwitterionic surfactants, or combinations thereof .

In general, the nonionic and anionic surfactants of the surfactant system may -if present- be chosen from the

surfactants described in 'Surface Active Agents' Vol. 1, by Schwartz & Perry, Interscience 1949, Vol. 2 by Schwartz, Perry & Berch, Interscience 1958, in the current edition of

'McCutcheon ' s Emulsifiers and Detergents' published by Manufacturing Confectioners Company or in

^>Tenside-Taschenbuch' , H. Stache, 2nd Edn., Carl Hauser Verlag, 1981. Nonionic surfactant

For the purposes of this disclosure, ^ληοηίοηίο surfactant' shall be defined as amphiphilic molecules with a molecular weight of less than about 10,000, unless otherwise noted, which are substantially free of any functional groups that exhibit a net charge at the normal wash pH of 6-11.

Any type of nonionic surfactant may be used, although preferred materials are further discussed below. Highly preferred are fatty acid alkoxylates, especially ethoxylates, having an alkyl chain of from C₈-C₃5, preferably C₈-C₃o, more preferably C10-C2 , especially Cio-Cis carbon atoms, for example, the Neodol range from Shell (The Hague, The Netherlands); ethylene

oxide/propylene oxide block polymers which may have molecular weight from 1,000 to 30,000, for example, Pluronic (trademark) from BASF ( Ludwigshafen, Germany) ; and alkylphenol ethoxylates, for example Triton X-100, available from Dow Chemical (Midland, Mich. , USA) .

Other nonionic surfactants may also be considered. These include condensates of alkanolamines with fatty acids, such as cocamide DEA, polyol-fatty acid esters, such as the Span series available from Uniqema (Gouda, The Netherlands), ethoxylated polyol-fatty acid esters, such as the Tween series available from Uniqema (Gouda, The Netherlands), alkylpolyglucosides , such as the APG line available from Cognis (Diisseldorf,

Germany) and n-alkylpyrrolidones , such as the Surfadone series of products marketed by ISP (Wayne, N.J., USA) . Furthermore, nonionic surfactants not specifically mentioned above, but within the definition, may also be used.

The more preferred nonionic surfactants are the fatty acid ethoxylates with an average degree of ethoxylation of 7, alkoxylates with one propylene oxide and multiple ethylene oxide units, seed oil based surfactant, such as Ecosurf SA7 or SA9 available from Dow Chemical, APGs, and branched alcohol Guerbet nonionics.

Anionic surfactant

Anionic surfactants' are defined herein as amphiphilic

molecules comprising one or more functional groups that exhibit a net anionic charge when in aqueous solution at the normal wash pH of between 6 and 11.

Preferred anionic surfactants are the alkali metal salts of organic sulphur reaction products having in their molecular structure an alkyl radical containing from about 6 to 24 carbon atoms and a radical selected from the group consisting of sulphonic and sulphuric acid ester radicals.

Although any anionic surfactant hereinafter described may be used, such as alkyl ether sulphates, soaps, fatty acid ester sulphonates, alkyl benzene sulphonates, sulphosuccinate esters, primary alkyl sulphates, olefin sulphonates, paraffin

sulphonates and organic phosphate; preferred anionic

surfactants are the alkali and alkaline earth metal salts of fatty acid carboxylates , fatty alcohol sulphates, preferably primary alkyl sulfates, more preferably they are ethoxylated, for example alkyl ether sulphates; alkylbenzene sulphonates, alkyl ester fatty acid sulphonates, especially methyl ester fatty acid sulphonates and mixtures thereof. Cationic_r amphoteric surfactants and/or zwitterionic surfactants

Also cationic, amphoteric surfactants and/or zwitterionic surfactants may be present in the liquid laundry pre-treatment compositions in which the hydroxamate is used as cosurfactant according to the invention.

Preferred cationic surfactants are quaternary ammonium salts of the general formula RiR₂R.₃RN⁺ X^~, for example where Ri is a C±2 ~ Ci alkyl group, R₂ and R₃ are methyl groups, R is a

2-hydroxyethyl group, and X^~ is a chloride ion. This material is available commercially as Praepagen (Trade Mark) HY from Clariant GmbH, in the form of a 40% by weight aqueous solution.

In a preferred embodiment the liquid laundry pre-treatment composition in which the hydroxamate is used according to the invention further comprises an amphoteric or zwitterionic surfactant. Amphoteric surfactants are molecules that contain both acidic and basic groups and will exist as zwitterions at the normal wash pH of between 6 and 11. Preferably an

amphoteric or zwitterionic surfactant is present at a level of from 0.1 to 20% by weight, more preferably from 0.25 to 15% by weight, even more preferably from 0.5 to 10% by weight.

Suitable zwitterionic surfactants are exemplified as those which can be broadly described as derivatives of aliphatic quaternary ammonium, sulfonium and phosphonium compounds with one long chain group having about 8 to about 18 carbon atoms and at least one water solubilizing radical selected from the group consisting of sulfate, sulfonate, carboxylate, phosphate or phosphonate. A general formula for these compounds is: R_!(R₂)_XY⁺R₃Z- wherein Ri contains an alkyl, alkenyl or hydroxyalkyl group with 8 to 18 carbon atoms, from 0 to 10 ethylene-oxy groups or from 0 to 2 glyceryl units; Y is a nitrogen, sulphur or phosphorous atom; R₂ is an alkyl or hydroxyalkyl group with 1 to 3 carbon atoms; x is 1 when Y is a sulphur atom and 2 when Y is a nitrogen or phosphorous atom; R₃ is an alkyl or

hydroxyalkyl group with 1 to 5 carbon atoms and Z is radical selected from the group consisting of sulfate, sulfonate, carboxylate, phosphate or phosphonate.

Preferred amphoteric surfactants are amine oxides, for example coco dimethyl amine oxide. Detergency builders

The liquid laundry pretreatment compositions in which the hydroxamate is used preferably comprise low levels of

detergency builder, based on the weight of the total

composition. The amounts of the inorganic builders zeolite and phosphate are less than 5 wt%.

On the other hand, the main wash detergent formulation used in step (II) of the method of the invention preferably comprises surfactant material and more than 15% by weight of builder. Said main wash detergent is preferably a main wash detergent powder.

Preferably the builder used both in the pretreatment step (I) of the method of the invention is selected from the group of alkali and alkaline earth metal carbonates (e.g. sodium

carbonate), silicates (e.g. layered silicate), and organic builders such as citrates (e.g. sodium citrate), succinates, sulphamates and malonates, and any combination of these. The organic builders are preferred. They may be used at levels of 1 wt% or more, up to, say, 50 wt%.

Organic builders that may be present in the liquid pre- treatment composition include polycarboxylate polymers such as polyacrylates and acrylic/maleic copolymers; polyaspartates ; monomeric polycarboxylates such as citrates, gluconates, oxydisuccinates , glycerol mono-di- and trisuccinates ,

carboxymethyloxysuccinates , carboxy-methyloxymalonates ,

dipicolinates , hydroxyethyliminodiacetates , alkyl- and

alkenylmalonates and succinates; and sulphonated fatty acid salts .

Organic builders may be used in minor amounts. Especially preferred organic builders are citrates, suitably used in amounts of from 1 to 30 wt%, preferably from 1.5 to 10 wt%; and acrylic polymers, more especially acrylic/maleic copolymers, suitably used in amounts of from 0.5 to 15 wt%, preferably from 1 to 10 wt%.

Builders, both inorganic and organic, are preferably present in alkali metal salt, especially sodium salt, form.

Other optional Ingredients

In addition to the essential components detailed in the claims, the liquid pre-treatment formulation may include one or more optional ingredients to enhance performance and properties. While it is not necessary for these elements to be present in order to practice this invention, the use of such materials is often very helpful in rendering the formulation acceptable for consumer use. Examples of optional components include, but are not limited to: hydrotropes, fluorescent whitening agents, photobleaches , fibre lubricants, reducing agents, enzymes, enzyme stabilising agents (such as borates and polyols), powder finishing agents, defoamers, bleaches, bleach catalysts, soil release agents, especially soil release polymers for cotton or polyester or both, antiredeposition agents, especially antiredeposition polymers, dye transfer inhibitors, buffers, colorants,

fragrances, pro-fragrances, rheology modifiers, anti-ashing polymers, preservatives, insect repellents, soil repellents, water-resistance agents, suspending agents, aesthetic agents, structuring agents, sanitisers, solvents, including aqueous and non-aqueous solvents, fabric finishing agents, dye fixatives, wrinkle-reducing agents, fabric conditioning agents and

deodorizers.

These optional ingredients may further include any one or more of the following: soap, peroxyacid and persalt bleaches, bleach activators, sequestrants , cellulose ethers and esters, other antiredeposition agents, sodium sulphate, sodium silicate, sodium chloride, calcium chloride, sodium bicarbonate, other inorganic salts, fluorescers, photobleaches, polyvinyl

pyrrolidone, other dye transfer inhibiting polymers, foam controllers, foam boosters, acrylic and acrylic/maleic

polymers, proteases, lipases, cellulases, amylases, other detergent enzymes, citric acid, soil release polymers, fabric conditioning compounds, coloured speckles, and perfume.

The main wash detergent formulation used in the 2^nd step of the method of the invention may also suitably contain one or more of the optional ingredients mentioned hereinabove.

In particular, the main wash laundry detergent formulation may suitably contain a bleach system based on peroxy bleach compounds, for example, inorganic persalts or organic peroxyacids, capable of yielding hydrogen peroxide in aqueous solution. Suitable peroxy bleach compounds include organic peroxides such as urea peroxide, and inorganic persalts such as the alkali metal perborates, percarbonates , perphosphates , persilicates and persulphates . Preferred inorganic persalts are sodium perborate monohydrate and tetrahydrate, and sodium percarbonate. Especially preferred is sodium percarbonate having a protective coating against destabilisation by

moisture. Sodium percarbonate having a protective coating comprising sodium metaborate and sodium silicate is disclosed in GB 2 123 044B (Kao) .

The peroxy bleach compound is suitably present in an amount of from 5 to 35% by weight, preferably from 10 to 25% by weight.

The peroxy bleach compound may be used in conjunction with a bleach activator (bleach precursor) to improve bleaching action at low wash temperatures. The bleach precursor is suitably present in an amount of from 1 to 8% by weight, preferably from 2 to 5% by weight.

Preferred bleach precursors are peroxycarboxylic acid

precursors, more especially peracetic acid precursors and peroxybenzoic acid precursors; and peroxycarbonic acid

precursors. An especially preferred bleach precursor suitable for use in the present invention is N, N, N ' , N ' -tetracetyl ethylenediamine (TAED) . Also of interest are peroxybenzoic acid precursors, in particular, N, N, N-trimethylammonium toluoyloxy benzene sulphonate.

A bleach stabiliser (heavy metal sequestrant) may also be present in the main wash detergent powder. Suitable bleach stabilisers include ethylenediamine tetraacetate (EDTA) and the polyphosphonates such as Dequest (Trade Mark), EDTMP.

However, notwithstanding the above it is preferred for the said powder to contain no bleach and to rely on the improved clay stain removal derived from the novel hydroxamate and surfactant combinationpresent in the liquid pre-treatment composition used in the 1^st step of the method of the invention.

The main wash detergent formulation may also contain one or more enzymes. Suitable enzymes include the proteases, amylases, cellulases, oxidases, peroxidases and lipases usable for incorporation in detergent compositions.

Said detergency enzymes are commonly employed in granular form in amounts of from about 0.1 to about 3.0 wt%. However, any suitable physical form of enzyme may be used in any effective amount .

Antiredeposition agents, for example cellulose esters and ethers, for example sodium carboxymethyl cellulose, may also be present.

The main wash detergent formulation may also contain soil release polymers, for example sulphonated and unsulphonated PET/POET polymers, both end-capped and non-end-capped, and polyethylene glycol/polyvinyl alcohol graft copolymers such as Sokolan (Trade Mark) HP22. Especially preferred soil release polymers are the sulphonated non-end-capped polyesters

described and claimed in WO 95 32997A (Rhodia Chimie) . Product form and preparation

The pre-treatment composition used in the first step of the method of the invention is in the liquid form. Preferably, said composition contains a hydrotrope to solubilise the ingredients thereof. Ethanol is preferably avoided. Preferred hydrotropes are propylene glycol and glycerol. Based on this teaching the skilled person will be able to select other hydrotropes that avoid the use of highly volatile solvents like ethanol without the need for inventive activity.

The main wash detergent powders preferably used in the second step of the method of the invention may be of low to moderate bulk density. In that case they may be prepared by spray-drying slurry, and optionally post dosing (dry-mixing) further

ingredients. Routes available for powder manufacture include spray drying, drum drying, fluid bed drying, and scraped film drying devices such as the wiped film evaporator. A preferred form of scraped film device is a wiped film evaporator. One such suitable wiped film evaporator is the Cryex system' based on a wiped film evaporator available from Ballestra S.p.A.

Alternative equipment would be the Chemithon the ^λ Turbo Tube' dryer system wherein a high active surfactant paste is heated and metering to a multi tube, steam- acketed drying vessel.

Alternatively, the main wash powder may be a Concentrated' or Compact' powder. Such powders may be prepared by mixing and granulating processes, for example, using a high-speed

mixer/granulator, or other non-tower processes.

The invention will now be further described with reference to the following non-limiting examples.

EXAMPLE S

Measurement of Soil Release Index (SRI)

SRI is a measure of how much of a stain on textile is removed during a washing process. The intensity of any stain can be measured by means of a reflectometer in terms of the difference between the stain and a clean cloth giving ΔΕ* for each stain. It is defined as ΔΕ* and is calculated as:

L*, a*, and b* are the coordinates of the CIE 1976 ( L*, a*, b*) colour space, determined using a standard reflectometer . ΔΕ* can be measured before and after the stain is washed, to give

AE*_bw (before wash) and AE*_aw (after wash) . SRI is then defined as :

SRI = 1 00 - ΔΕ^*

A SRI of 100 means complete removal of a stain. ΔΕ after wash is the difference in L a b colour space between the clean (unwashed) fabric and the stain after wash. So a ΔΕ after wash of zero means a stain that is completely removed. Therefore, a SRI_aw (aw: after wash) of 100 is a completely removed stain. The clean (or virgin) fabric is an "absolute standard" which is not washed. For each experiment, it refers to an identical piece of fabric to that to which the stain is applied. Therefore, its point in L a b colour space stays constant . Determination of SRI-values

For the determination of the SRI -values, a standard protocol was used, called the Tergometer wash protocol.

Said Tergometer wash protocol is as follows:

1. Measurement of the colour of the stain on the textile cloth (before washing) .

2. Switch on the Tergometer and set to a temperature of 30°C. 3. Add water of required hardness, leave to heat to 30°C for 10 minutes .

4. Add formulation to each pot and then agitate at 100 rpm for 1 minute

5. Add the stained swatches and ballast into each pot.

6. Start the wash, agitate at 100 rpm and leave to wash for 12 minutes .

7. Rinse with fresh water (26°FH) for 2 minutes.

8. Repeat rinse.

9. Dry overnight in the dark.

10. Read stains after wash.

Example 1: Removal of a Indian Red Soil on knitted polyester, preteated with a liquid Formualtion and then washed using a powder formulation

Two liquid formulations A and B were formulated.

The surfactants present therein are sodium alkyl benzene sulphonate (Na LAS anionic) and alkyl ether sulfate (SLES 3EO Ex Unilever) . Furthermore, formulation B contains a Coco

Hydroxamic Acid (Ex AXIS House), as shown in Table 1. Other standard laundry ingredients were also included. The pH of these formulations was buffered to between 7 and 8.5. The formulations were made using demineralised water.

Table 1 : Liquid formulations used

Furthermore, a main-wash type detergent powder product C including the surfactant alkyl benzene sulphonate was

formulated having the composition shown in Table 2. Table 2: Powder detergent product C

The Indian Red soil on knitted polyester stains tested were treated with 0.8 g of one of the two liquid pre-treatment formulations and then after 5 mins standing time washed in 1L of wash liquor made in 26FH water with 2.8g/L of powder product C. The resultant SRI_aw values after applying the two pre- treatment formulations A and B followed by the wash step with powder product C as outlined above are shown in Table 3 below. Table 3: Stain removal values (SRI)

Table 3 shows the clear benefit in removal when pretreating stain with a formulation containing alkyl hydroxamic acid.

Example 2: Removal of a Indian Red Soil on knitted polyester and woven cotton, preteated with Liquid

(Anionic/Nonionic) Formualtions and then washed using a powder formulation

Two liquid formulations D and E were formulated.

The surfactants present therein are sodium alkyl benzene sulphonate (Na LAS anionic) and alcohol ethoxylate (Neodol 25- 7) . Furthermore, formulation E contains a Coco Hydroxamic Acid (Ex AXIS House), as shown in Table 4. Other standard laundry ingredients were also included. The pH of these formulations was buffered to between 7 and 8.5. The formulations were made using demineralised water.

Table 4 : Liquid formulations used

Ingredients LAS/NI (D) LAS/NI+coco

HXA (E)

% in formulation

Glycerol 5.00 5.00

PPG 9.00 9.00

NaOH 4.73 4.73

TEA 3.24 3.24 Citric Acid 0.98 0.98

LAS 27.60 27.60

Neodol 25-7 12.50 12.50

Soap 4.78 4.78

Dequest 2066 0.50 0.50

Coco hydroxamate 0 2

water demin Balance to Balance to

100% 100%

The powder product used in this example was the same as that of example 1.

The Indian Red soil (on knitted polyester and on woven cotton) stains tested were treated with 0.8 g of one of the liquid pretreatment formulations and then after 5 mins standing time washed in 1L of wash liquor made in 26FH water with 2.8g/L of powder product C. The resultant SRIaw after applying these two pre-treatment formulations D and E followed by the wash process with the powder product are shown in Table 5 below.

Table 5: Stain removal values (SRI)

Table 5 shows the clear benefit in removal when pretreating stain with a formulation containing alkyl hydroxamic acid.

Claims

1. Method of cleaning laundry, wherein said method comprises the steps of:

(I) pre-treating the laundry with a liquid pre-treatment composition; and

(II) washing the thus-pre-treated laundry in a wash liquor comprising a main wash detergent formulation, preferably a main wash detergent powder,

wherein the liquid pre-treatment composition comprises:

o

wherein R is

a straight or branched C4-C20 alkyl, or

a straight or branched substituted C4-C₂₀ alkyl, or

a straight or branched C4-C20 alkenyl, or

a straight or branched substituted C4-C₂₀ alkenyl, or

an alkyl ether group CH₃ (CH₂)_n (EO)_m wherein n is from 2 to 20 and m is from 1 to 12, or a substituted alkyl ether group CH₃

(CH₂)_n (EO)_m wherein n is from 2 to 20 and m is from 1 to 12, and

b) 3 to 80 wt% of detersive surfactant system comprising anionic nonionic, cationic zwitterionic surfactant or a combination thereof, and wherein the weight ratio a) to b) lies in the range 6: 1 to 1:16000, preferably 1:10 to 1:400, and c) optionally, other ingredients to 100 wt% provided that zeolite, phosphate and carbonate builders are present at less than 5 wt% and ethanol is present at a level of less than 5 wt% .

2. Method according to claim 1, wherein the hydroxamate in the pre-treatment composition has a structure wherein R¹ is chosen from the group consisting of C , C5, Ce, C₇, C₈, C9, C10, Cn, C12 or Ci normal alkyl group and R² is hydrogen.

3. Method according to claim 1 or 2, wherein R¹ is a Cs-i normal alkyl group.

4. Method according to any preceding claim, wherein the pre- treatment composition comprises a hydrotrope system containing propylene glycol and glycerol.

5. Method according to any preceding claim, wherein the pre- treatment composition comprises detergent surfactant at a concentration from 15 to 50 % by weight.

6. Method according to any preceding claim, wherein the

surfactant system present in the pre-treatment composition contains anionic surfactant and nonionic surfactant whereby the level of anionic surfactant is from 50 to 95 wt% based on the total weight of the surfactant system.

7. Method according to any preceding claim, wherein the surfactant system comprises 2 types of anionic surfactant of which the weight ratio lies in the range 80:20 to 20:80.

8. Method according to any preceding claim, wherein the weight ratio of hydroxamate to detersive surfactant system in the pre- treatment composition lies in the range of 1:10 to 1:100.

9. Method according to any preceding claim, wherein the main wash detergent formulation applied in step (II) comprises surfactant material and more than 15 % by weight builder.

10. Use of a pre-treatment composition as specified in claim 1, for the removal of particulate soils, preferably red clay, most preferably Georgia clay, from polyester and cotton fabrics.

11. Use according to claim 9, wherein the pre-treated fabrics are washed in a wash liquor comprising a main wash detergent powder including surfactant material and more than 15% by weight builder.

12. Use of 0.005 to 20% by weight hydroxamic acid or its corresponding hydroxamate of the structure o

wherein R is a Cs -C1 normal alkyl group, and R is a hydrogen atom, in a laundry pre-treatment composition, for improving the particulate soils stain removal from a textile substrate, wherein the pre-treatment composition further comprises from 3 to 80 wt% of a detersive surfactant system; and optionally other ingredients to 100 wt%, provided that zeolite, phosphate and carbonate builders are present at less than 5 wt%, and

wherein the pre-treated fabrics are washed in a wash liquor comprising a main wash detergent formulation including

surfactant and more than 15% by weight builder.