WO1994018297A1 - Oxidising agents - Google Patents

Abstract

The use of N-acyl and O-acyl bleach activator compounds to generate peroxy acids in aqueous acidic environments usually under relatively dilute conditions is described. The product is used in situ as a bleach, biocide or disinfectant. Preferred processes use hydrogen peroxide with tetraacetylethylene diamine or with the sodium salt of nonanoyloxybenzene sulphonate. The pH is preferably less than 6.5.

Description

Oxidising Agents

The present invention relates to the in situ production of peroxygen-based oxidising species from a peroxygen source and an activator followed by the use of the product as an oxidising agent, for instance as a bleach or a biocide.

It is very well known in the laundry detergent field to use a combination of peroxygen bleach precursor (or peroxygen source) and bleach activator in the same or separate compositions. The bleach activators are acyl- donors. The bleach precursor and activator when added to the aqueous laundry liquor react together in a reaction involving attack by peroxide anion on the activator to form a peroxygen bleaching species usually the peroxy acid anion. The conditions of laundry liquors are invariably alkaline, usually having a pH of at least 9. The activator and peroxygen source do not react together during storage and are themselves stable under storage conditions.

It is known to coat or agglomerate bleach activators to increase their stability on storage in a laundry detergent composition and/or to affect their dissolution characteristics in the wash liquor. Fatty acids have been used and in WO-A-9213798 solid organic acids such as monomeric aliphatic hydroxy carboxylic acids including citric, lactic and glycolic acids, are incorporated into activator particles. In EP-A-0028432 bleach particles are stabilised for storage by incorporating acidic components. The particles are incorporated into conventional alkaline laundry detergents.

In WO-A-9312067 (unpublished at the priority date of the present case) acylated citrate esters are used to increase the bleaching effect of hydrogen peroxide. The esters are incorporated into bleach booster compositions which then appear to be used in conjunction with normal laundry detergents. The bleach booster composition may be acidic or alkaline. InEP-A-0241137 liquid laundry bleaching compositions are described which contain a dispersion of a solid particulate bleach activator in acidic aqueous hydrogen peroxide. The preferred activators are substituted phenyl esters of alkanoic acids. The compositions are used in conjunction with conventional laundry detergents so that the detersive solution produced is alkaline.

In the Wool Research Organisation of New Zealand's Report No. R202 by S.J. McNeil of October 1992 the use of sodium perborate solution in the shrink proofing of wool is described. The perborate is used normally at alkaline pH since acidification (using acetic acid) to neutral or acidic (pH 4.5) is said to cause a loss of effectiveness as the oxidising species is not formed. The perborate is, in some instances, activated by the addition of tetraacetyl ethylenediamine.

In American Dyestuff Reporter, June 1992, 34-41 El- Sisi et al describe the activation of hydrogen peroxide used in the prepration of cotton fabrics in a desizing, bleaching and scouring step by urea. The effect of varying the pH between 4 and 10 is investigated. The concentration of peroxide is always 8g/l (0.24M) or less. The temperature of the reaction is 95°C. The mechanism of activation postulated in this disclosure is different from the mechanism which is thought to be responsible for the activation properties of compounds incorporated into laundry detergents as bleach activators.

Organic peroxy acids are well known as useful oxidising agents for a wide range of specific oxidation reactions that they perform in high-to-quantitative yield. A review of the various methods known for the preparation of peroxy acids is available in "Organic Peroxides", volume l, D. Swern Ed, Wiley Interscience (1970) 313-335. Most of the reactions described use the corresponding carboxylic acid, the acid anhydride, the acid chloride or the aldehyde as the starting materials for instance for a perhydrolysis reaction using hydrogen peroxide. One of the reactions uses the alkaline perhydrolysis of imidazolides of carboxylic acids to form the peroxy carboxylic acids (Folli, U et al (1968) Bollettino, 26, 61-69).

In GB-A-931,119 a process for producing carboxylic peroxy acids by reacting hydrogen peroxide with an ester of the organic carboxylic acid in the absence of water and in the presence of a catalytic quantity of an acid catalyst. The process is used to make peracetic, perbenzoic, peradipic, perpropionic and peroxalic acids. The process requires hydrogen peroxide to be dissolved into the liquid ester, water to be removed and then acid catalyst to be added only after complete removal of the water. In one example the product solution was subsequently used to oxidise cyclohexene to form cyclohexene oxide.

GB-A-930,056 describes a process for the reaction of an aromatic carboxylic acid ester with hydrogen peroxide in an alkane sulphonic acid to form the aromatic peroxy acid. Hydrogen peroxide was added to the reaction mixture as an aqueous solution having a concentration of at least 70%.

GB-A-1,363,916 describes anhydrous processes for producing percarboxylic acids which are aromatic or aliphatic in nature by carrying out the reaction in the presence of organic phosphorous compounds. The citation contemplates the use of acid derivatives, including esters, although anhydrides or the acids themselves are preferred and there are no worked examples using other derivatives. There may be some water left in the reaction mixture.

It is known to produce peracetic acid, a strong oxidising agent, in situ by reaction of acetic acid and hydrogen peroxide, for instance to be used in epoxidation reactions. The advantage of using the peracid rather than hydrogen peroxide itself is that it is a stronger oxidising agent. Peracids are however unstable and can be dangerous to transport in bulk. The problem with the in situ reaction of acetic acid and hydrogen peroxide is that water must be removed to drive the reaction or else a large excess of one of the reactants must be used which necessitates complex separation and recycling steps. Acetic anhydride has also been used in place of acetic acid as starting material for this in situ reaction. The conditions during the in situ reaction step and subsequent oxidation reaction will be acidic. Acetic acid and acetic anhydrides as starting materials for an in situ reaction require special precautions on handling and so are not suitable for use in a domestic environment. Acetic anhydride is water sensitive and so requires special storage conditions.

In FR-A-1176059 bleaching solutions for textiles are made by adding acetic anhydride to oxygenated water at pH 3 to 6. The solutions are used to bleach textiles at temperatures in the range 50 to 104°C. The production of oxygenated water requires special apparatus.

In FR-A-1187519 the bleaching properties of hydrogen peroxide solution at acidic pH is increased by the addition of anhydrides of organic carboxylic acids such as acetic anhydride. The resultant solution is used at high temperatures, from 70ºC up to over 100ºC. The utility appears to be in the industrial bleaching of fabrics. GB-A-901687 and US-A-3227655 constitute similar disclosures and describe the incorporation of heavy metal sequesterants into the bleaching solution and the use of ammonia or ethanolamine to regulate the pH. The solutions are used at temperatures of more than 60°C to bleach fabrics. In all of these disclosures the anhydride is incorporated in stoichiometric or higher amounts as compared to the amount of peroxide. Acetic anhydride is a liquid and reacts with water and other ingredients on storage and is difficult to formulate into a storage stable composition.

There have been descriptions of the in situ formation of peracid and the subsequent use of the solution of the peracid as a bleach under acidic conditions. However these tend to be for specialised or industrial processes and/or use activator compounds which are undesirable. For example in DE-A-2227602 dialkyl dicarbonate compounds are used to increase the bleaching effect of hydrogen peroxide at a range of pH's from acidic to alkaline. The mechanism of activation is not elucidated.

In US-A-3551087 and US-A-3374177 a process is described in which formaldehyde or a formic acid ester or formamide is reacted with hydrogen peroxide to form performic acid solution which is then used as a bleach. The reaction and the bleaching take place in an acidic environment. The bleaching process is part of the industrial dyeing process for wool and silk. Performic acid is, however, extremely unstable and even relatively dilute solutions can explode at ambient temperatures. It is furthermore corrosive and an irritant, as is formic acid, the by-product of the bleaching reaction. For these reasons formate activators are undesirable, especially for use in a domestic or other non-industrial context.

In EP-A-0545594 tooth whitening compositions are described which contain peroxy acetic acid as the bleaching agent. Compositions into which peroxy acetic acid itself is incorporated are acidic. It is suggested that the peroxy acetic acid can be generated in situ by the reaction in aqueous solution of tetraacetyl ethylene diamine and sodium perborate. In the specific examples of that embodiment of the invention the aqueous solution formed when the perborate and activator are dissolved is alkaline.

It would be desirable to find a system with the stability and advantages of the bleach precursor/activator combinations used in the laundry detergent industry, but where the reaction between precursor and activator and/or the subsequent oxidation (including bleaching) step are carried out under acidic conditions and at relatively low concentrations.

In a new process according to the invention a peroxygen source is reacted with an activator compound which is a C₂ or higher acyl donor in a first step in aqueous solution under acidic conditions, the peroxygen source being present in the reaction mixture at a concentration of less than 20M to form a product solution containing an oxidising product which is a stronger oxidising agent than the peroxygen source itself and the product solution is subsequently used as a bleach under acidic conditions.

In such a process the peroxygen source is reacted with an activator compound of the formula I

in which L is a leaving group and R¹ is an alkyl, aralkyl, alkaryl, or aryl group, any of which groups has up to 24 carbon atoms and may be substituted or unsubstituted, in a first "perhydrolysis step in aqueous solution under acidic conditions the peroxygen source being present at a concentration of less than 10M in the perhydrolysis reaction mixture, to form a product solution containing an oxidising species which is a stronger oxidising agent than the peroxygen source, itself and the solution containing the oxidising species is used as a bleach under acidic conditions.

Without being bound by theory, the present inventors believe that the mechanism of reaction is that the activator is perhydrolysed to form the percarboxylic acid of the acyl group. The oxidising product, the percarboxylic acid, is found to be a stronger oxidising agent that than the peroxygen source. It is believed that the activator of the formula I forms a percarboxylic acid of the formula II

The first step is consequently sometimes referred to as the perhydrolysis step.

The leaving group L is preferably a compound the conjugate acid of which has a pKa in the range 4 to 13, preferably 7 to 11, most preferably 8 to 11.

It is preferred that R¹ is an aliphatic group preferably a C_1-18 alkyl group, or an aryl group. In the present invention the term alkyl includes alkenyl and alkyl groups may be straight, branched or cyclic.

In the formula I L and R¹ may be joined to form a cyclic compound, usually a lactone or a lactam. These cyclic groups may include heteroatoms, for instance oxygen or optionally substituted nitrogen atoms, carboxy1 groups as well as -CH₂- groups or substituted derivatives thereof. They may be saturated or unsaturated. L can itself comprise a cyclic group, including heterocylic groups, for instance joined to the C=O group of the compound I via the heteroatom.

Substituents on R¹ and L can include hydroxyl,

=N-R² in which R² is selected from any of the groups represented by R¹ and is prefrably lower alkyl, amine, acyl, acyloxy, alkoxy, aryl, aroyl, aryloxy, aroyloxy, halogen, amido, and imido groups and the like as well as other groups not adversely affecting the activity of the compound.

In the invention the compound of the formula I can be any acyl-donor compound, usually an N-acyl or O-acyl compound, which has been described as a bleach activator for use in laundry detergents. The compound of the formula I may be an anhydride, but is preferably an ester or, even more preferably, an amide derivative.

Amide derivatives include acyl imidazolides as described by Folli et al (op. cit.) and N,N-di acylamides. Other examples of N-acyl derivatives are:

a) 1,5-diacetyl-2,4-dioxohexahydro-1,3,5-triazine (DADHT); b) N-alkyl-N-suphonyl carbonamides, for example the compounds N-methyl-N-mesyl acetamide, N-methyl-N-mesyl benzamide, N-methyl-N-mesyl-p-nitrobenzamide, andN-methyl- N-mesyl-p-methoxybenzamide;

c) N-acylated cyclic hydrazides, acylated triazoles or urazoles, for example monoacetyl maleic acid hydrazide; d) O,N,N-trisubstituted hydroxylamines, such as O-benzoyl- N,N-succinyl hydroxylamine, O-p-nitrobenzoyl-N,N-succinyl hydroxylamine and O,N,N-triacetyl hydroxylamine;

e) N,N'-diacyl sulphurylamides, for example N,N'-dimethyl- N,N'-dimethyl-N,N'-diacetyl sulphuryl amide and N,N'- diethyl-N,N'-dipropionyl sulphurylamide;

f) 1,3-diacyl-4,5-diacyloxy-imidazolines, for example 1,3- diformyl-4,5-diacetoxy imidazoline, 1,3-diacetyl-4,5- diacetoxy imidazoline, 1,3-diacetyl-4,5-dipropionyloxy imidazoline;

g) Acylated glycolurils, such as tetraacetyl glycoluril and tetraproprionyl glycoluril;

h) Diacylated 2,5-diketopiperazines, such as 1,4-diacetyl-

2,5-diketopiperazine, 1,4-dipropionyl-2,5-diketopiperazine and 1,4-dipropionyl-3,6-dimethyl-2,5-diketopiperazine; i) Acylation products of propylene diurea and 2,2-dimethyl propylene diurea, especially the tetraacetyl or tetrapropionyl propylene diurea and their dimethyl derivatives;

j) Alpha-acyloxy-(N,N')polyacyl malonamides, such as alpha-acetoxy-(N,N')-diacetyl malonamide.

k) O,N,N-trisubstituted alkanolamines, such as O,N,N- triacetyl ethanolamine.

Alternatively the compound may be an ester, for instance

1) N-acyl lactams, such as N-benzoyl-caprolactam,

N-acetyl caprolactam, the analogous compounds formed from

C_4-10 lactams.

m) N-acyl and N-alkyl derivatives of substituted or unsubstituted succinimide, phthalimide and of imides of other dibasic carboxylic acids, having 5 or more carbon atoms in the imide ring.

n) sugar esters, such as pentaacetylglucose,

o) esters of imidic acids such as ethyl benzimidate, p) triacylcyanurates, such as triacetylcyanurate and tribenzoylcyanurate, q) esters giving relatively surface active oxidising products for instance of C_8-18-alkanoic or -aralkanoic acids such as described in GB-A-864798, GB-A-1147871 and the esters described in EP-A-98129 and EP-A-106634, for instance compounds of the formula I where L comprises an aryl group having a sulphonic acid group (optionally salified) substituted in the ring to confer water solubility on a benzyl group, especially nonanoyloxy- benzenesulphonate sodium salt (NOBS), isononanoyloxy- benzenesulphonate sodium salt (ISONOBS) and benzoyloxy- benzenesulphonate sodium salt (BOBS)

r) phenyl esters of C_14-22-alkanoic or -alkenoic acids, s) esters of hydroxylamine,

t) geminal diesters of lower alkanoic acids and gem-diols, such as those described in EP-A-0125781 especially 1,1,5- triacetoxypent-4-ene and 1,1,5,5-tetraacetoxypentane and the corresponding butene and butane compounds, ethylidene benzoate acetate and bis (ethylidene acetate) adipate and u) enol esters, for instance as described in EP-A-0140648 and EP-A-0092932.

Where the activator is an anhydride it is preferably a solid material, and is preferably an intra-molecular anhydride, or a polyacid polyanhydride. Such anhydride compounds are more storage stable than liquid anhydrides, such as acetic anhydride. Anhydride derivatives which may be used as activator include

v) intramolecular anhydrides of dibasic carboxylic acids, for instance succinic, maleic, adipic, phthalic or 5- norbornene-2,3-dicarboxylic anhydride,

w) intermolecular anhydrides, including mixed anhydrides, of mono- poly-basic carboxylic acids, such as diacetic anhydride of isophthalic or perphthalic acid

x) isatoic anhydride or related compounds such as described in WO-A-8907639, for instance 2-methyl-(4H)3,1- benzoxazin-4-one (2MB4) or 2-phenyl-(4H)3,1-benzoxazin-4- one (2PB4) and y) polymeric anhydrides such as poly(adipic) anhydride or other compounds described in our co-pending application Wo- A-9306203.

In the process of the invention the precursor peroxygen source may be hydrogen peroxide itself, but is alternatively an inorganic persalt, for instance a percarbonate or, a perborate, for instance sodium perborate, or an organic peroxide such as benzoyl peroxide or urea peroxide.

The pH in the perhydrolysis step is preferably less than 6.5, more preferably about 6.0. The pH in the hydrolysis step is usually more than 2.0, preferably more than 5.0.

In the perhydrolysis reaction the amount of water present is preferably at least as much (in terms of moles) as the peroxygen source. Where the peroxygen source is hydrogen peroxide itself, the concentration of hydrogen peroxide is preferably less than 70% weight/volume (that is weight of hydrogen peroxide based on volume of water plus hydrogen peroxide plus other components in the mixture concerted). Preferably the concentration is less than 60% weight by volume and more preferably less than 30% w/v. Where the product of the reaction is to be used in a domestic environment or other environment where it is difficult to take special precautions in handling the products, it is preferred for the concentration to be less than 15% or even 10% w/v or less than 5% w/v. The concentration is usually at least 0.2%, preferably at least 1% w/v, more preferably at least 2% w/v. Where the peroxygen source is other than hydrogen peroxide then the concentration is preferably such as to give the equivalent available oxygen as the quoted concentrations of hydrogen peroxide. The concentration of peroxygen source in the aqueous liquid is for instance less than 10M, preferably less than 5M or sometimes even less than 3M down to 0.01M. Preferably the concentration is at least 0.05M, more preferably 0.1M, even more preferably at least 0.2M. The pH in the bleaching step is usually less than 6.5, preferably less than 6.0. The pH is usually more than 2.0, for instance more than 3.0, most preferably more than 5.0.

In the perhydrolysis step of the reaction the temperature is preferably in the range 0 to 95ºC, more preferably in the range 10 to 80ºC. The invention is most useful when the temperature is less than 60°C, or even less than 50°C, for instance less than 40ºC or even around room temperature. The temperature is often above 20°C. The temperature in any subsequent oxidising step is preferably in the same ranges as the temperature during the perhydrolysis step and is preferably substantially the same temperature especially where the product solution is immediately used for instance as a bleach or disinfectant. A particular advantage of using activators for the peroxygen source is that the oxidising product tends to be formed at a relatively low temperature, for instance less than hand hot which is advantageous from a safety point of view.

The present invention provides also a new use of a composite product comprising starting materials for the perhydrolysis reaction. Preferably the product can simply be added to water to provide the entire reaction mixture. The product therefore comprises a peroxygen source, an activator compound as well, if necessary, as components for rendering the pH of an aqueous solution to which the components of the product are added acidic. Acidifying components may not be necessary where the peroxygen source itself is sufficiently acidic to achieve the desired pH.

In one preferred embodiment of the composite product the activator is a solid anhydride compound. The peroxygen source may be hydrogen peroxide or a solid peroxygen compound.

In another preferred embodiment of the composite product the activator is other than an anhydride. In another preferred embodiment of the composite product the peroxygen source is a solid, preferably an inorganic persalt.

An acidifying component may comprise an acid and/or buffering material. The component may comprise a polybasic organic acid, such as a polybasic carboxylic acid such as citric, succinic, or adipic acid or sulphamic acid. Alternatively the component may react with a by-product of the perhydrolysis reaction to make an acid. Where perborate is used, borate is a by-product and so any component known to react with borate to drop the pH, eg cis-1,2-diols, such as glycols and polyols, boric acid, or sodium dihydrogen phosphate can be used. Such acidifying components are also suitable for use where percarbonate is the peroxygen source.

Although the composite product may contain the individual components each in separate compositions, for instance one of which contains the peroxygen source, another of which contains the activator and another of which contains an acidifying component, it is preferred to provide at least the activator and acidifying component as a mixture in a single composition in a form in which they are stable. Such a product which does not contain peroxygen source, may, for instance, be added to an aqueous solution of peroxgyen source such as aqueous hydrogen peroxide, which is readily commercially available, in the form of, for instance 60%, 20%, 10% or, preferably, 5% w/v or less solution. It is most preferred for all of the components to be provided in a single composition, in which the components do not react, and which is preferably therefore substantially waterfree.

The product(s) may be in liquid form, for instance in a non-aqueous liquid medium, in which the components may be dissolved or dispersed. For instance particles of activator with protective coatings, for instance produced by microencapsulation techniques or spray coating of solid activator, may be suspended in an aqueous, or non aqueous, solution of peroxygen source. As an alternative to a solution of peroxygen source that component may also be suspended in the liquid medium, either in a separate liquid phase or in particulate dispersed phase, particles of solid peroxygen source optionally being coated with a protective coating. Coated particles of either peroxygen source or activator may be disrupted or diluted in to water or with abrasion.

Preferably the or each composition of the composite product is in solid form, for instance as a mixture of particles of the individual components or, more preferably, comprising particles each of which comprise all of the components. Such particles may be provided by techniques similar to those used in the laundry detergent industry, for instance including particles produced by spray drying liquid slurries, by granulation techniques using binders (for instance synthetic or natural polymers or derivatives) or by melt blending followed by extrusion or other techniques.

Preferably the product contains the active ingredients in appropriate relative quantities so that when the composition is diluted (or the compositions are mixed) with water the first step of the reaction proceeds at the optimal rate and at the desired pH. The activator and peroxygen source are for instance present in relative amounts such that up to 500%, preferably 5% to 150% of the stoichiometric amount of activator (for complete reaction with the peroxygen source) is provided. Preferably the amount of activator is 10 to 100%, more preferably 20 to 80% of the stoichiometric amount.

The composite product may include other additives, for instance stabilisers which stabilise the product before use, as well as stabilisers for the peroxy acid oxidising species formed in the reaction, especially heavy metal sequestrants. The new product may also include surfactants to act as wetting agents and inorganic salts, for instance which affect the physical properties of the solid form or act as diluent. Other ingredients may be included depending on the mode of use of the composition on the final application of the reaction product, for instance perfumes, or agents to assist dissolution or dispersion of the product into water.

A preferred embodiment of the composite product for use in the present invention comprises a peroxygen source, an activator compound, a surfactant and, if necessary, an acidifying component.

The reaction product of the perhydrolysis reaction is preferably used immediately, without removal of any byproducts or addition of other materials, in the second step in which it is used as a bleaching (including disinfecting) agent. Sometimes it may be desirable to add additional ingredients for the second step such as pH-adjusters, surfactants/wetting agents which may be cationic, anionic, amphoteric or non-ionic, or other additives to improve the second step of the process for instance co-disinfectants, biocides, slimicides, enzymes, enzyme inhibitors or radical scavengers, abrasives etc. Cobiocides are particularly valuable where the primary objective of the second step is disinfection/sterilisation.

The second step of the process of the present invention may be used as a bleaching/disinfection process, by which we mean any process in which unwanted colour is reduced or removed, non-coloured stains are reduced or removed and/or a substrate is disinfected. For instance the second step may include processes in which hard surfaces eg floors, food preparation surfaces, utensils, toilets, washing facilities in domestic, industrial or institutional applications are cleansed, and bleaching processes for fabrics (for instance during fabric manufacture and dyeing). The second step may comprise water, effluent or sewage treatment as a biocide, pulp and paper bleaching, paper deinking, wood bleaching, fibre and fabric manufacture, use as an biocide, fungicide, bacteriocide, sporicide and/or viricide, as a contact lens disinfectant or general disinfectant for use inter alia in general environmental clean up. Furthermore the second step may be used in food production for instance to bleach flour, beverages, or edible oils in the food and brewing industries, for instance to clean pipes used for beverages, or, in cosmetic uses such as hair bleaching or tooth or denture whitening and/or disinfecting.

Since the reaction can be carried out at a relatively low concentration it can be carried out without special precautions, for instance in a domestic or institutional environment.

Compositions which are suitable to be diluted direct into water to allow the first and second steps of the reaction to proceed without further additions, may be categorised in four convenient categories.

The first category comprises liquid formulations which include a surfactant. These compositions will be suitable for use as hard surface cleaners and other uses where surface active disinfection and/or bleaching is required, for instance floor cleaning compositions, domestic and institutional hard surface cleaners, toilet disinfectants, general toiletries disinfectant, sanitising bottles, including glass and plastic bottles, and pipe cleaning compositions. For most of these uses it will be desirable for the composition to be relatively low foaming, although for some, for instance toilet disinfecting and general toiletries disinfectant, it may be desirable for the composition to have a relatively high foam. The use of suitable surfactants which will foam is well known in the art. For compositions which are desired to be low foam, it may desirable to incorporate anti-foaming agents, for instance soap or silicone anti-foams. Liquid formulations including surfactants may be useful in other applications such as for use to bleach fibres or fabrics, such as nappies or in fabric production, cellulose fibres, especially in paper de-inking operations, and in general environmental clean-up operations. A. second category of composition comprises liquid formulations but which contain no surfactants. These may be useful where no surface activity is necessary, for instance in effluent and water treatment, in toilet disinfectants, for use as a swimming pool treatment, for colour removal from chemicals, from pulp during paper making or recycling, in general industrial sterilisation and in some domestic sterilisation situations, for instance as a general toiletry disinfectant, in denture cleaning compositions, in sanitising glass and plastic bottles or other containers, as well as in certain environmental clean-up operations. Furthermore, where the composition is to be used as a general industrial oxidation reaction, it may be undesirable to include a surfactant.

The liquid formulations mentioned above may be pourable liquids, which are aqueous or non-aqueous, or may be in gel or paste form. Furthermore the compositions may be two-phase, for instance a cream form. Alternatively the compositions could be in the form of a mousse (where the composition contains surfactant) by the injection of a gas, especially for domestic hard surface cleaning operations.

A further category of composition is in solid form and includes a surfactant. The general uses of these compositions are similar to those for which the liquid formulations including a surfactant are useful, as mentioned above.

A further category of formulation comprises a solid composition but without surfactant. These compositions are useful in the same categories of uses as the liquid formulations without surfactant. The compositions may, in solid form, be more storage stable, since it is in general easier to keep the bleach activator and peroxygen donor compound in separate particles and prevent them coming into contact with one another during storage. It is furthermore easier to isolate other components of the composition from one another and from the bleach components, especially where storage sensitive compounds such as enzymes, other biocides or perfumes are present.

Solid compositions may be in the form of particulate mixtures or may be tabletted. Tabletted formulations, or even granular formulations, may include agents to increase the dissolution rate of the compositions upon addition to water. For instance suitable components incorporating into tablets aid disintegration of the tablet. Such ingredients may create effervescence, for instance; a suitable component is sodium bicarbonate, or other alkali metal bicarbonate.

The compositions may also contain ingredients to assist in their application or stability or which improve their appearance, for instance thickeners, dispersants, opacifiers, hydrotropes, dyes, perfumes etc.

The following examples illustrate the invention. In the examples the concentration of peroxygen source is reported in terms of the starting concentration of aqueous hydrogen peroxide, to which other reactants are added. The molar concentration can be calculated.

Example 1

Reaction of TAED and hydrogen peroxide

1.1 This area of investigation was to find a simple method of determining the presence of a stronger oxidising species rather than hydrogen peroxide. To this end a number of indicators containing oxidisable groups were tried, to identify which changed colour on addition of peracetic acid and the product of an embodiment of the invention, but not hydrogen peroxide. The results showed that alizarin complexone (AC) was decolourised by peracetic acid, but not by hydrogen peroxide. This material was therefore selected as the indicator of choice.

1.2 Once an indicator had been identified it was possible to carry out the experiments to see whether acid catalysed perhydrolysis was a possible mechanism. TAED (22.8g 0.1mol) was added to 60% hydrogen peroxide (60mls 1mol). The mixture was stirred for 10 minutes. A 2ml aliquot was removed and added to alizarin complexone solution (0.5ml). Over a period of a few minutes the colour in the solution was seen to disappear as the indicator was bleached.

1.3 The successful result of this experiment led to comparative bleaching experiments being carried out on stained swatches of cloth. The stains used were Red Wine, Tea and BC1 (tea and clay). Comparisons were made between the bleaching performance of 60% H₂O₂, 10% PAAH and TAED/H₂O₂. The performance was assessed by measuring the initial brightness before washing and final brightness using a Hunterlab D25M colorimeter after the swatches had been rinsed and dried by application of an electric iron set at the wool setting. The results are given in Table 1.

1.4 Another set of experiments determined at which initial pH was the greatest bleaching observed. These experiments were carried out in 60 ml 60% H₂O₂ with 22.8g TAED added. The pH of the peroxide was adjusted before the addition of TAED with sodium hydroxide. The highest pH attainable was 6.95 as above this the decomposition of the peroxide was too rapid. The stain used in these tests were tea stains produced in house. These were selected as they showed the greatest residual colour in the previous tests. The pH of the solutions were measured initially after 1 hour's bleaching after 3h and finally after 24h. All bleaching experiments were carried out at room temperature. A blank was run using distilled water at pH 6. The results are shown in Tables 2 and 3.

1.5 Experiments were also carried out to identify whether Fe(III) ions had an effect on the bleaching properties. Three systems were set up, one containing Dequest 2066 (an alkylene polyamine polymethylene phosphonic acid) as a sequestering agent, one with 0.5mls 20mM Fe(III) solution added and one with hydrogen peroxide only. All of these were carried out at pH 6. The results are shown in Table 3. 1.6 Results & Discussion

All experiments carried out at room temperature in open beakers. Dwell time in the bath of 1 hour.

Notes: With 60% hydrogen peroxide and TAED at the higher end of the acidic pH range bleaching was visible on contact, with the other solutions the bleaching was much less rapid. On reaction there was effervescence visible as the TAED dissolved, this process was much more rapid at higher pH. There was a distinct odour of peracetic acid from all reactions containing TAED. Remarkably the bleaching activity towards AC was still observed after 24 hours at room temperature.

1.7 These results show that TAED activates peroxide solutions at a range of pH's. The quickest bleaching performance is seen at higher pH probably due to more rapid dissolution of TAED and formation of peracetic acid under these conditions. The formation of an acidic species when TAED is dissolved in hydrogen peroxide is indicated by the pH change observed, the solutions only become markedly more acidic if TAED is present. Those experiments carried out without TAED show very little change in pH on the same time scale. The noticeable odour of peracetic acid, which is rather distinctive as well as pungent, is also evidence for the presence of this species in solution. It is assumed from this evidence that peracetic acid is likely to be the bleaching/oxidising species responsible for the bleaching effect, although it may be a by-product, an intermediate or the product of further reaction of another strong oxidising species.

1.8 The experiments with and without Fe(III), at pH 6, showed very similar bleaching (the %ge stain loss was identical). This seems to show that iron catalysed radical reactions are not important under these conditions. This conclusion is borne out by the results with sequestrant present which gave very similar results to the experiment without sequestrant at pH 6. Example 2

TAED, DADHT, SNOBS, BOBS, 2MB4 , ISONOBS as activators for peroxygen bleaches at acidic PH, for stains in solution and on fabrics

2.1 Experimental

2.1.1 Swatches

The activator/peroxygen source combination used was 60% hydrogen peroxide in a 10:1 ratio with the activator. Small swatches of cloth (20-25cm²) were used and the stain was chlorophyll. The bleaching experiments were run using lOmls hydrogen peroxide (60%) which was adjusted to the required pH using sodium hydroxide solution. A weighed quantity of the activator (sufficient to produce 33mmol of peracid) was then added and the mixture stirred for 2 minutes to dissolve the activator. The swatch of cloth was then added and left for 30 minutes with occasional stirring. After 30 minutes, the swatches were removed from the activator solutions, rinsed with deionised water to remove any remaining traces of bleach, dried by the technique used in example 1 and the brightness measured using a Hunterlab D25M colorimeter. The pH of the solution was measured after the cloths had been removed. The results are shown in Table 4.

2.1.2 The dependence of pH on time

Experiments to monitor the relationship between pH and time were carried out using TAED, BOBS, SNOBS, 2MB4 and DADHT as activators. The pH of 60% hydrogen peroxide was adjusted to about pH 6. To 20mls of this solution was added 33m mols of activator. The pH was measured with time. The results are shown in Table 6.

2.1.3 Timed bleaching

Timed bleaching experiments were carried out using the same technique and quantities as in 2.1.1 above with different dwell times of the swatch in the bleach solution. Six separate solutions were prepared and a swatch added to each at the same time. The swatches were removed and rinsed in deionised water after set time periods. The times used were 5mins, 10mins, 20mins, 30mins, 1hr and 2hrs. The final brightness after drying by the usual technique was determined using the Hunterlab. The results are shown in Table 5.

2.1.4 Time/pH bleaching profile

The solutions and swatches used were prepared as in the above experiments. Four solutions were prepared and a swatch added to each after a set period of time. The cloth was left in the bleach solution for 5mins and then removed and rinsed thoroughly with deionised water. The times at which the swatches were added were after 1min, 15mins, 30mins and 1hr. A different solution was used for each swatch. The activators used were TAED and DADHT. The final brightness after drying of the cloth was measured using the Hunterlab. The results are shown in Table 7.

2.1.5 Activation of sodium perborate solutions in the presence of acidifying components.

Two lots of sodium perborate tetrahydrate (17.5g) mixed with citric acid (8g) (to reduce the pH on reaction with borate) were prepared. To one lot TAED (2.6g) was added. Each of the mixtures was added to 50mls deionised water and stirred vigorously. The pH of the solutions was measured after dissolution had been achieved. The results are given in 2.2.6 below.

Two lots of sodium perborate tetrahydrate (20g) mixed with sodium dihydrogen phosphate (17.5g) (to reduce pH) were prepared. To one of these SNOBS (4.4g) was added. The mixtures were added to 100ml deionised water and a chlorophyll stained swatch added to each solution. After 1.5hrs the swatch was removed and the brightness measured on the Hunterlab. The pH was measured at timed intervals. 2.2 Results and Discussion

2.2.1 The chlorophyll stain was seen to be resilient to bleaching under these harsh conditions which makes it a very good stain to use. The less stain that is removed the better the comparisons which can be drawn between bleaches. 2.2.2 . Of the other activators BOBS and SNOBS gave the quickest results with DADHT fairly close behind. ISONOBS and TAED reacted more slowly. It should be noted however, that the activators are used on equivalent molar basis (i.e. equivalents of acyl group released) so that the weight of TAED is less than, for instance, the weight of SNOBS and BOBS. The blank experiments with peracetic acid, water and hydrogen peroxide (at both pH 6 and pH 1) show that activation is occurring, when the activator is present, and that this is not an effect of the lower pH in the activated solutions (Table 4). The drop in pH is good evidence that an acidic species is being produced which is not present in the unactivated peroxide solution.

2.2.3 The decrease in pH on addition of activator was seen to be rapid (Table 6). As would be expected the rate varied with different activators due to differences in both the acid being produced and the rate of perhydrolysis. BOBS was difficult to use, as addition to peroxide produced a thick frothy paste. It was because of this that SNOBS was used in subsequent experiments. The problem is probably due to the surfactant properties of these activators, a property which is important in some applications. This increases the wetting ability of the peracid solution.

2.2.4 The bleaching of swatches with different bleaching times showed the expected increase of bleaching with time (Table 5).

2.2.5 The effect of time and pH on the bleaching efficacy of activated solutions was also studied. In this case the dwell time in the bleaching solution was the same (5 mins) but the swatches were added after different times. In four separate solutions cloth was added after 1min, 15mins, 30mins and 1hr. Each of these swatches was a quarter of the same larger swatch, to ensure a constant substrate concentration. After 5 minutes in the bleaching solution the cloth was removed and rinsed with deionised water. Comparing of the different swatches, for the same activator, gave a measure of the stability, rate of peracid release and pH dependence of the bleaching. The relationship between these variable is complex but qualitative comparisons can be made. The results show that TAED gives consistent bleaching over the first hour. DADHT on the other hand gives better initial bleaching but after an hour the efficacy was similar (Table 7). This seems to show that DADHT released strong oxidising agent more rapidly initially but after time gives a similar concentration. This is borne out by the pH measurements. The pH of the solution containing DADHT decreased more rapidly than that of the TAED containing solution. After 20hrs the figures were much closer (Table 6).

2.2.7 SNOBS was seen to give better bleaching at all times in this test, i.e. up to 2 hours. The release of strong oxidising species seemed to be slow. The cloth added after lmin showed less bleaching than those added later (Table 2). In all cases the stability of the bleach activation with time was remarkably good. There was noticeably better bleaching than with peroxide alone in all cases.

2.2.8 The activation of sodium perborate solutions was also seen to occur under acidic conditions. The use of citric acid and sodium dihydrogen phosphate enable acidic solutions of perborate to be prepared which also give rise to some degree of buffering. When SNOBS was incorporated into such a solution there was noticeably quicker bleaching than occurred without any added activator. The pH of the solutions was seen to be acidic (pH 6.4 with phosphate and pH 5.1 with citrate) and much more stable than seen with more concentrated peroxide solutions. The pH of the activated and unactivated solutions was very similar in both cases. Table 4. Activating acidic peroxide with different activators.

Table 5. The effect of different bleaching times on brightness and solution pH.

Table 6. The effect of activators on solution pH with time.

Table 7. Bleaching efficiency against time.

SNOBS - sodium nonanoyloxybenzene sulphonate

BOBS - benzoyloxybenzoic acid sodium salt

DADHT - 1,5-diacetyl-2,4-dioxohexahydro-1,3,5-triazine 2MB4 - 2-methyl-(4H) 3,1-benzoxazin-4-one

(Cf. WO-A-8907639)

ISONOBS - Sodium isononanoyl oxybenzene sulphonate

Example 3

Biocidal activity of activator/hydrogen peroxide mixtures 3.1 The assessments were performed in a test tube situation following the principles of BS 6471:1984.

3.2 100ml volumes of Nutrient Broth were inoculated with Escherichia coli, Staphylococcus aureus and Streptococcus faecalis.

3.3 A 150mg/l solution of peracetic acid (PAA) was used for comparison. This was prepared in sterile distilled water.

3.4 In order to achieve concentrations comparable with the comparative 150mg/l PAA solution, test solutions of the formulations were prepared using TAED, SNOBS or acetic anhydride in the amount noted in the respective table below in 100ml of 1% hydrogen peroxide solution. In example 3.6 the test solution was left to age for 24 hours before use. Other test solutions were used immediately after make up.

3.5 1ml of the test bacterial culture was added to 9ml of the appropriate formulation, mixed and left for a period of time at a given temperature. (The conditions are noted in the respective table below.)

3.6 1ml of this liquor was transferred to 9ml of inactivator comprising 50g/l sodium thiosulphate and 0.25g/l catalase in distilled water. The inactivator was filter sterilised using 0.45μm membrane filters. (Example 3.9 using acetic anhydride as activator was inactivated by dilution with MRD (see below) alone.)

3.7 From these inactivated liquors, 10-fold serial dilutions were performed using Maximum Recovery Diluent (MRD). Pour plates were prepared using 1ml volumes of each dilution mixed with molten Plate Count Agar (PCA).

3.8 For controls the procedure was repeated using 1% hydrogen peroxide as the control for the test formulations and sterile distilled water as the control for PAA.

3.9 All plates were incubated for 48 hours at 37°C after which time the number of colonies visible on each plate was counted. The reduction in the number of cfu compound to the control solution is calculated. The results quote the log (base 10) of the control count/test count. Where the figure is "more than" the figure quoted this indicates the cfu count in the test plate was below the minimum which can be quantified using this technique.

3.10 Results

3.11 In general none of the formulations tested was particularly effective against Staph. aureus. 3.12 Low concentrations of TAED with H₂O₂ generally did not appear to be particularly effective when compared with PAA although some reduction was seen against E.coli. Increasing the temperature, increasing the contact time and the solution to age were all found to increase the effectiveness.

3.13 Acetic anhydride is an adequate activator under the test conditions, giving a total kill of E. coli and Strep, faecalis.

3.14 SNOBS/H₂O₂ was much more effective than TAED/H₂O₂ against all three test organisms. No growth was obtained from the treated cultures of E.coli or Strep. faecalis whilst the number of Staph. aureus colonies recovered was reduced by over half, although a remaining count of 1.5x10³ was still obtained.

3.15 PAA was more effective than SNOBS/H₂O₂ as, besides a total kill of E.coli and Strep, faecalis. at higher concentration it also reduced the numbers of recovered Staph. aureus by 98%. However, this figure of 98% still left over 3.0x10⁴ cfu/ml recoverable.

Example 4

Production of Acidic Percarbonate solutions

4.1 It has been found that citric acid and sodium dihydrogen phosphate are able to produce acidic solutions of hydrogen peroxide when mixed with sodium perborate and water. This experiment was designed to test whether the same was true for sodium percarbonate.

4.2 The following formulations were added to 1l cold water. In each case 1.85 g TAED, as activator was included. The amount of percarbonate was varied, with the amount of citric acid added being such as to give approximately the same pH in each test. The presence of hydrogen peroxide was determined by iodometric titration as described in Example 5 below.

Example 5

Acids and anhydrides as activaters

5.1 Using acetic acid (comparative) and TAED (invention) as the acetyl donor.

The following experiments were carried out using 50ml 10% by hydrogen peroxide at room temperature with activator and compared against controls. Chlorophyll stained swatches were used as the substrate. Reflectance was measured using an ICS Texicon Spectraflash 500 (a colorimeter using the CIE Lab system) using software version 4.70.

The initial pH's of these solutions were recorded.

The swatches were left in solution for 75 minutes. The brightness was compared to an unbleached chlorophyll stained swatch after rinsing with deionised water and drying as in the previous examples. Results

Table 10

It can be seen that acetic acid is ineffective as an activator under these conditions. This experiment also shows that the bleaching effect of TAED does not arise from hydrolysis followed by perhydrolysis of the resulting acetic acid.

5.2 The use of acetic anhydride (comparative) and TAED (inventive)

Acetic anhydride is a widely used source of peracids under laboratory conditions. This material is however water sensitive, corrosive and therefore not easy to handle. The following experiments were designed to see how effective acetic anhydride was as a peracid generator under dilute aqueous conditions.

The procedure used was similar to that in the above experiments (5.1) with acetic acid. Hydrogen peroxide was used at 10% w/v. A range of stained swatches were used, these were chlorophyll, curry and blackberry. Samples were also assayed for peracetic acid using an iodometric titration. 5.2.1 Bleaching stained swatches

In the following experiments the peroxide/activator combinations shown in Table 10 were used to prepare the bleaching solutions.

All experiments were carried out at ambient temperature. Formulation 5.2.4 Comparative was only used in the first two experiments. The reflectance was measured as in 5.1. In the table the reflectance differences are noted. A positive value means the bleached swatch is lighter than the control stained swatch and a negative sign means it is darker.

Experiment A

Chlorophyll stained swatches were added to these solutions and left to bleach for 75 mins. After this time the swatches were removed and washed in water to remove any remaining active species.

Experiment B

Chlorophyll stained swatches were added to the solutions used above and left to bleach overnight for 17 hours. The swatches were rinsed. The pH of the bleaching solution was measured after the cloths had been removed. Experiment C

Fresh solutions using the first three compositions were prepared and allowed to stand overnight before chlorophyll stained swatches were added. The cloths were left to bleach for 75 mins and then removed and rinsed. Experiment D

This was the same as experiment A but using curry stained swatches. There was no water/acetic anhydride solution (5.6 comp) tested.

Experiment E

This was the same as experiment A using blackberry stained swatches. There was no water/acetic anhydride solution (5.6 comp) tested.

5.2.2 Iodometric titration

The solutions 5.2.1 and 5.2.2 (comp) used in experiment E were tested at intervals for peracetic concentration using an iodometric titration carried out on ice, the titration being carried out immediately, so that hydrogen peroxide present would give minimal titres and primarily strong oxidising agent is determined.

5.2.3 Results

In general acetic anhydride/H₂O₂ reacted more quickly than either TAED/H₂O₂ or H₂O₂ itself. TAED/H₂O₂ gave better bleaching against chlorophyll stains than H₂O₂ alone.

5.3 Determination of the peracetic acid produced by acetic anhydride (comparative) and TAED.

The concentration of strong oxidising agent was determined at time intervals using an iodometric titration on ice. The solutions studied were those used in experiments 5.2.1 and 5.2.2 Comp Experiment E as experiments 5.3.1 and 5.3.2 respectively. The iodometric titration carried out was that used for calibrating peracetic acid. The solution to be assayed is added to a flask containing potassium iodide, acetic acid and ice. The iodine liberated is titrated with sodium thiosulphate.

It can be seen from the above results that the TAED activated solution gives a lower initial concentration of peracetic acid. However over time, in this case 7 days, the TAED solution increases in strong oxidising agent concentration while the acetic anhydride solution loses oxidising agent. After several days the levels of strong oxidising agent are higher in the TAED containing solution. There is still a large volume of TAED left undissolved after about 140 hrs. This makes this a very good slow release procedure.

Example 6

The use of penta-acetylglucose (PAG) as activator 6.1 This experiment is to determine the efficacy of PAG as an ester as a bleach activator under acidic conditions.

The bleaching experiments were carried out using chlorophyll stained swatches. The three formulations shown in Table 15. The samples were allowed 75 mins bleaching time. In a further stage to investigate further release of strong bleach 3 drops 50% w/w NaOH solution were then added to formulations 6.1 and 6.1 comp. A second swatch of material was added and bleached for 25 mins. Formulation 6.3 was at pH 5.6 immediately after NaOH addition (prior to this no bleaching occurred), 6.2 comp showed a pH of 7.5. After 2 hrs pH of 6.3 = 3.11, of 6.2 comp = 6.84.

The lightness, strength and colour after drying using an iron as described in Example 1 above determined by the use of a ICS Texicon Spectraflash 500 (a colorimeter which uses the CIE Lab) using version 4.70 software.

6.5 Results

Y is yellower Positive results in the table indicate lighter, stronger more yellow, respectively.

6.4 The results show that PAG is an effective activator under acidic conditions. The efficiency depends markedly on the pH of the solution. The more strongly acidic the peroxide solution the less effective the activation.

Example 7

Perborate/TAED in a non-surfactant containing composition

A mixture of the following powders was made and added to 1l of water:

1.8 g TAED

2.58 g sodium perborate monohydrate

without or with 1.58 g sodium bicarbonate

varying amounts of citric acid or sodium dihydrogen orthophosphate as acidifiers. The pH of the solution at the varying amounts of acid component were measured after 10 mins. The results are shown in .the following table.

The bleaching performance of some of the solutions was determined on un-glazed, tea-stained tiles. The bleaching solution is applied to one half of the tile and the difference in whiteness, as determined using a hunter Lab apparatus between the two halves is determined. The value is given as ΔW. The Hunter-Lab apparatus is set to CIE tristimulus XYZ scale. The W reading is the Z% brightness.

The solution as above with bicarbonate, which had a pH of 6.3 gave a ΔW value of 5.5.

Example 8

Surfactant - 3 Compositions Including Perborate and Various Activators

Mixtures containing 2.58 g sodium perborate monohydrate, 3 g citric acid, 1.6 g sodium bicarbonate and activator comprising 1.8 g TAED or an equivalent weight of N-benzyl caprolactam (NBC) or triacetyl ethanolamine (TAE) or granules containing TAED, were dissolved into 1l water. The peracid release rate was monitored. The results are given in the following table.

* RESULT AFTER 3 DAYS

Granule 1 is Mykon ATC (available from the applicant company) formed from 90-94% TAED carboxymethyl cellulose binder and no more than 2% water and has particle size 95% in the range 0.2 to 1.6 mm.

Granule 2 is Mykon ASD formed from 83 TO 87% TAED, CMC binder and 2.5 to 3.5% methylene phosphonic acid sequestrant and no more than 2.5% water having particle size 95% in the range 0.2 to 1.6 mm.

The temperature during the reaction was 40°C Example 9

Storage Stability of Compositions Containing Surfactants

The following compositions were formulated by blending the ingredients in particulate form and storing them in a closed container at ambient temperature. The amount of available oxygen after 12 weeks of storage was determined by a standard Avox titration. The percentage loss of available oxygen is reported in the following table.

Example 10

Oxidising Agent Concentration for Various Activators at pH 6.3

Mixtures comprising 2.58 g sodium perborate monohydrate, 1.58 g sodium bicarbonate and 21 g sodium dihydrogen orthophosphate and 1.88 g of activator, and dissolved into 2 litres of water. The concentration of strong oxidising in the solution generated was measured after various periods of time using the iodometric titration mentioned above. The results are given in the following table.

IA - isatoic anhydride

2PB4 - 2-phenyl-(4H)1,3-benzoxazin-4-one

These results show that, although the initial release rate for strong oxidising agent by SNOBS is higher than by TAED, TAED gives better long term release, continuing to increase even after one hour. 2MB4 gives an extra quicker initial release rate but the effect diminishes after a short period of less than half an hour.

Example 11

A solution of Flash liquid and a similar solution, but with an added amount of bleach booster mixture formed from TAED (at 1.88 g/l), sodium perborate monohydrate (at 2.58 g/l) and citric acid in an amount to give a final pH of 6.5, were compared for their performance in bleaching tea stains. The solutions were applied with a brush to half a tile and then either dipped in water or wiped with a cloth to remove the liquid. The whiteness was then recorded as described above. The ΔW values for Flash alone, removed by wiping and dipping, were 4.0 and 9.7, respectively. The ΔW values for the boosted Flash were 4.8 and 13.5 respectively.

Claims

1. A process in which a peroxygen source is reacted with an activator compound which is an acyl donor in a first step in aqueous solution under acidic conditions, the peroxygen source being present in the perhydrolysis reaction mixture at a concentration of less than 20M to form a product solution containing an oxidising product which is a stronger oxidising agent than the peroxygen source itself and the product solution is subsequently used as a bleach under acidic conditions in a second, bleaching step.

2. A process according to claim 1 in which the activator is a compound of the formula

R¹-C-L

in which L is a leaving group and R¹ is an alkyl, aralkyl, alkaryl, or aryl group, any of which groups has up to 24 carbon atoms and may be substituted or unsubstituted.

3. A process according to claim 1 in which the activator is a compound which is a solid at room temperature.

4. A process according to any preceding claim in which the first step is carried out at a pH less than 6.5, preferably in the range 2.0 to 6.5, more preferably in the range 5.0 to 6.5.

5. A process according to any preceding claim in which the peroxygen source is present in the reaction mixture for the first step at a concentration of less than 10M, preferably less than 5M, more preferably less than 1M.

6. A process according to any preceding claim in which the peroxygen source is selected from hydrogen peroxide, urea peroxide, organic peroxides and inorganic persalts, and is preferably a compound which is a solid at room temperature.

7. A process according to any preceding claim in which the peroxygen source is hydrogen peroxide and the concentration of peroxygen source in the aqueous liquid before the addition of activator compound is less than 60% w/v, preferably less than 20% w/v, more preferably less than 10% w/v, most preferably less than 5% w/v.

8. A process according to any preceding claim in which the temperature in the first step is in the range 0 to 95ºC, preferably at least 20°C and up to 80°C, more preferably up to 60ºC.

9. A process according to any preceding claim which is carried out in the presence of an acid-generating species.

10. Use of a composite product containing a peroxygen source, an activator and, if necessary, an acid generating species in quantities such that when all of the components of the products are added to water the pH is reduced to and remains below 7, to form the reactant mixture for a process according to any preceding claim by adding the product to water.

11. Use according to claim 10 in which any acid generating species is selected from a polybasic organic carboxylic acid or a compound which drops the pH on reaction with a by-product of the reaction, for instance a polyol, boric acid or sodium dihydrogen phosphate.

12. Use according to claims 10 or claim 11 in which the activator and any acid generating species are present in a single composition.

13. Use according to claim 12 in which in the product the peroxygen source, activator and any acid generating species are present in a single composition.

14. Use according to any of claims 10 to 13 in which the peroxygen source is in the form of a solid material, and, preferably, the product includes an acid generating species.

15. Use according to any of claims 10 to 14 in which the activator is a solid anhydride or is other than an anhydride.

16. Use according to any of claims 12 to 15 in which the said composition is in a particulate solid form.

17. Use according to claim 17 in which the composition comprises a single type of particle comprising all of the components of the product.

18. Use according to any of claims 10 to 17 in which the product contains a surfactant.

19. A product containing, in the same composition, a solid peroxygen source, an acyl donor activator compound, a surfactant and, if necessary, an acidifying component such that the product dissolves into water to form an acidic solution.