DE69406531T2 - OXYDERS - Google Patents

Abstract

N-acyl compounds known as bleach activators especially tetraacetylalkylene diamines, are reacted with a peroxygen source in aqueous solution at an acidic pH to form an oxidising product which is a stronger oxidising agent than the peroxygen source used as the starting material. The product solution is used for instance as a bleach or disinfectant. The activator and peroxygen source may be provided as a concentrate product ready for dilution with components able to produce acidic pH in the aqueous solution. The product is, for instance in particulate solid form containing granules of activator and different granules of peroxygen source.

Description

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

It is well known in the detergent art to use a combination of a peroxygen bleach precursor (or peroxygen source) and a bleach activator in the same or separate compositions. The bleach activators are acyl donors. When the bleach precursor and activator are added to the aqueous wash liquor, they react with each other in a reaction involving attack of the activator by the peroxide anion to form a peroxygen bleach species, usually the peroxyacid anion. Wash liquors are invariably alkaline, usually having a pH of at least 9. The activator and peroxygen source do not react with each other during storage and are themselves stable under storage conditions.

It is known to coat or agglomerate bleach activators to improve their stability during storage in a detergent composition and/or to influence their solubility properties in the wash liquor. Fatty acids have been used and in WO-A-9213798 solid organic acids such as monomeric aliphatic hydroxycarboxylic acids including citric, lactic and glycolic acids are included in the activator particles. In EP-A-0028432 bleach particles are stabilized for storage by including acidic components. The particles are included in conventional alkaline detergents.

In report No. R202, October 1992, of the Wool Research Organisation of New Zealand, shrink proofing of wool by treatment with aqueous sodium perborate is described. The reaction is carried out at alkaline pH and in some cases tetraacetylethylenediamine is used as an activator. The effect of carrying out the treatment at neutral pH is investigated and it is concluded that the perhydroxy anion does not decompose to an active oxidising species at acidic pH. The concentration of sodium perborate in the aqueous solution is 0.1 M, regardless of whether a neutral or acidic pH was used. Acidification is achieved by adding acetic acid to the sodium perborate solution.

In American Dyestuff Reporter, June 1992, 34-41, El- Sisi et al. describe the activation of hydrogen peroxide used in the manufacture of cotton fabrics in a desizing, bleaching and rinsing step by urea. The effect of changing the pH between 4 and 10 is studied. The concentration of peroxide is always 8 g/L (0.24 M) or less. The reaction temperature is 95ºC. The activator mechanism postulated in this disclosure is different from the mechanism believed to be responsible for the activation properties of compounds included in detergents as bleach activators.

Organic peroxy compounds are well known as useful oxidizing agents for a wide range of specific oxidation reactions, which they perform in high to quantitative yield. A review of various processes known for the preparation of peroxyacids is available in "Organic Peroxides", Volume 1, Ed. D. Swern, Wiley Interscience (1970), 313-335. Most of the reactions described use the corresponding carboxylic acid, acid anhydride, acid chloride or aldehyde as starting materials, e.g. for a perhydrolysis reaction using hydrogen peroxide. One of the reactions uses the alkaline perhydrolysis of imidazolides of carboxylic acids to form the peroxycarboxylic acids (Folli, U. et al. (1968), Bollettino, 26, 61-69).

It is known to produce peracetic acid, a strong oxidizing agent, in situ by reaction of acetic acid and hydrogen peroxide, e.g. for use in epoxidation reactions. The advantage of using the peracid rather than the hydrogen peroxide itself is that it is a stronger oxidizing agent. However, peracids are unstable and transporting them in large quantities can be dangerous. 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 requires complex separation and recycling steps. Acetic anhydride was also used instead of acetic acid as the starting material for this in-situ reaction. The conditions during the in-situ reaction step and the subsequent oxidation reaction are acidic. Acetic acid and acetic anhydrides as starting materials for an in-situ reaction require special precautions during handling and are therefore not suitable for household use. Acetic anhydride is sensitive to water and therefore requires special storage conditions.

US-A-3551087 and US-A-3374177 describe a process in which formaldehyde or a formic acid ester or formamide is reacted with hydrogen peroxide to form a performic acid solution which is then used as a bleaching agent. The reaction and bleaching take place in an acidic environment. The bleaching process is part of the industrial dyeing process for wool and silk. However, performic acid is extremely unstable and even relatively dilute solutions can explode at ambient temperatures. It is also corrosive and an irritant, as is formic acid, the by-product of the bleaching reaction. For these reasons, formate activators are not desirable, especially for use in the home or other non-industrial setting.

EP-A-0545594 describes tooth whitening compositions containing peracetic acid as a bleaching agent. Compositions in which peracetic acid itself is included are acidic. It is suggested that the peracetic acid can be formed in situ by the reaction in aqueous solution of tetraacetylethylenediamine 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 detergent industry, but in which the reaction between precursor and activator and/or the subsequent oxidation step (including bleaching) takes place 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 an N-acyl compound in which the acyl group has at least 2 carbon atoms in a first step in aqueous solution under acidic conditions to form an oxidizing product.

The process determines that the oxidizing product is a stronger oxidizing agent than the peroxygen source.

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

wherein R¹ is an alkyl, alkenyl, aralkyl, alkaryl or aryl group, each of these groups has up to 24 carbon atoms and may be substituted or unsubstituted, and -NR²R³ is a leaving group, wherein R² and R³ are independently selected from H, C₁₋₂₄ alkyl, alkenyl, aralkyl, alkaryl or aryl groups and carbonyl-containing groups having at least 2 carbon atoms, wherein the carbonyl group is attached to the nitrogen atom in formula I, in a first step in aqueous solution under acidic conditions to form an oxidizing species which is a more powerful oxidizing agent than the peroxygen source itself.

Without being bound by theory, the present inventors believe that the reaction mechanism is such that the N-acyl activator is perhydrolyzed, with the N-containing portion of the molecule acting as a leaving group to form the respective percarboxylic acid of the acyl group.

It is therefore assumed that the product of the reaction of I with the peroxygen source is a percarboxylic acid of the formula II

In one embodiment of the process, the product containing the stronger oxidizing species is subsequently used as a bleaching agent in an aqueous environment at a pH of less than 7.

In another embodiment of the invention, the product of the first step (hereinafter sometimes referred to as the perhydrolysis step for convenience) is subsequently used as an oxidizing agent in an oxidation step which is carried out without removing any by-products from the first perhydrolysis step.

It is preferred that R¹ is an aliphatic group, preferably a C₁₋₁₈ alkyl or alkenyl group, or an aryl group.

In the present invention, alkyl and alkenyl groups may be straight chain, branched or cyclic.

In the compound of formula I, the groups R² and R³ may be linked together to form a cyclic group. R¹ may be further or alternatively linked to either R² or R³ to form a cyclic group. These cyclic groups may include heteroatoms, e.g. oxygen or optionally substituted nitrogen atoms, carboxyl groups, and -CH₂- groups or substituted derivatives thereof. They may be saturated or unsaturated.

Substituents on R¹, R² and R³ may include hydroxyl, =N-R⁴, where R⁴ is selected from any of the groups represented by R² and R³ and preferably represents lower alkyl, amine, acyl, acyloxy, alkoxy, aryl, aroyl, aryloxy, aroyloxy, halogen, amido and imido groups and the like, as well as other groups that do not adversely affect the activity of the compound.

In the invention, the compound of formula I is preferably any N-acyl compound described as a bleach activator for use in detergents. In the compound of Formula is preferably an amide derivative, such as an acyl imidazolide as described by Folli et al. op. cit.) and N,N-diacylamides, e.g. triacetylethanolamine or most preferably tetraacetylethylenediamine (TAED). Other examples of N-acyl derivatives are:

a) 1,5-Diacetyl-2,4-dioxohexahydro-1,3,5-triazine (DADHT);

b) N-alkyl-N-sulfonylcarbonamides, e.g. the compounds N-methyl- N-mesylacetamide, N-methyl-N-mesylbenzamide, N-methyl-N-mesyl- p-nitrobenzamide and N-methyl-N-mesyl-p-methoxybenzamide;

c) N-acylated cyclic hydrazides, acylated triazoles or urazoles, e.g. monoacetylmaleic hydrazide;

d) O,N,N-trisubstituted hydroxylamines, such as O-benzoyl-N,N-succinylhydroxylamine, O-p-nitrobenzoyl-N,N-succinylhydroxylamine and O,N,N-triacetylhydroxylamine;

e) N,N'-diacylsulfurylamides, for example N,N'-dimethyl-N,N'-diacetylsulfurylamide and N,N'-diethyl-N,N'-dipropionylsulfurylamide;

f) 1,3-Diacyl-4,5-diacyloxyimidazolines, e.g. 1,3-diacetyl-4,5-diacetoxyimidazoline, 1,3-diacetyl-4,5-dipropionyloxyimidazoline;

g) Acylated glycolurils, such as tetraacetylglycoluril and tetrapropionylglycoluril;

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 propylenediurea and 2,2-dimethylpropylenediurea, in particular tetraacetyl- or tetrapropionylpropylenediurea, and their dimethyl derivatives;

j) α-acyloxy-(N,N')polyacylmalonamides, such as α-acetoxy-(N,N')-diacetylmalonamide;

k) O,N,N-trisubstituted alkanolamines, such as O,N,N-triacetylethanolamine;

l) N-acyl lactams, such as N-benzoylcaprolactam, N-acetylcaprolactam, the analogous compounds formed from C₄₋₁₀-lactams;

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

In the process of the invention, the precursor peroxygen source may be hydrogen peroxide itself, but Alternatively, it is an inorganic persalt, e.g. a percarbonate or a perborate, e.g. 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 throughout the reaction. Since the pH usually decreases during the reaction due to the formation of the percarboxylic acid, this means that the pH at the beginning of the reaction should be acidic and should preferably be less than 6.5. Preferably, the pH at the beginning of the reaction is less than about 6.0. The pH at the beginning of the reaction and preferably throughout the reaction is usually more than 2.0, preferably more than 5.0.

In the perhydrolysis reaction, the amount of water present (expressed in moles) is preferably at least as large as that of the peroxygen source. When the peroxygen source is hydrogen peroxide itself, the concentration of hydrogen peroxide is preferably less than 70% w/v (i.e. weight of hydrogen peroxide based on the volume of water plus hydrogen peroxide plus other components in the mixture in question). Preferably, the concentration is less than 60% w/v and more preferably less than 30% w/v. When the product of the reaction is to be used in the home or other environment where it is difficult to take special precautions in handling the products, it is preferred that the concentration be less than 15 or even 10% w/v, e.g. 5% w/v or less. The concentration is usually at least 0.2%, preferably at least 1% w/v, more preferably at least 2% w/v. If the peroxygen source is other than hydrogen peroxide, the concentration is preferably such that an equivalent amount of available oxygen is provided to the stated concentrations of hydrogen peroxide. Expressed in moles, the concentration of hydrogen peroxide or perborate or percarbonate in the perhydrolysis reaction mixture is, for example, suitably in the range 0.01 M to 10 M, preferably in the range 0.05 or 0.1 M to 5 M, more preferably in the range 0.2 M to 2 M, often below 1 M.

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

The activator compound is generally used in an amount such that it is capable of providing 0.1 to 5.0 equivalents of acyl groups per mole of peroxygen source, preferably 0.2 to 1.0. The amount is often less than the stoichiometric amount, e.g. up to 0.9 or 0.8 of the stoichiometric amount. Tetraacetylethylenediamine, for example, reacts as an activator to donate an acyl group from each nitrogen atom and thus to provide 0.2 equivalents of acyl groups per mole of peroxide for complete reaction, 0.1 mole of TAED is required. Less than this is often used, although the optimum amount depends on the degree of enhancement of oxidation performance compared to the cost of the peroxygen source and activator.

The present invention also provides the use of a composite product comprising all the starting materials for the perhydrolysis reaction. Preferably, the product may simply be added to water to provide the total reaction mixture. The product therefore comprises a peroxygen source, an N-acyl activator compound₁, preferably of formula I, and components to render the pH of an aqueous solution to which the components of the product are added acidic if necessary, although the peroxygen source itself may in certain circumstances be sufficiently acidic so that no additional acidifying component is required.

An acidifying component may comprise an acid and/or a buffer material. The component may comprise a polybasic organic acid such as a polybasic carboxylic acid such as citric, succinic or adipic acid or sulfamic acid. Alternatively, the component may react with a by-product of the perhydrolysis reaction to form an acid. When perborate is used, borate is a by-product and thus any components known to react with borate to lower pH may be used, e.g. cis-1,2-diols, e.g. glycols and polyols, boric acid or sodium dihydrogen phosphate. Such acidifying components are also suitable for use with other inorganic persalts.

Although the composite product may contain the individual components in two or more separate compositions, e.g. one containing the peroxygen source (e.g. an aqueous solution of hydrogen peroxide as a concentrate for dilution or ready for use without further dilution) and another containing the activator, e.g. of formula I, it is preferred that a mixture of at least two of the components be provided in a single composition in which the components do not react and which is preferably substantially free of water. It is preferred to provide at least the activator and the acidifying component, if present, as a mixture in a single composition in a form in which they are stable. Such a product, not containing a peroxygen source, may be added, for example, to an aqueous solution of a peroxygen source such as hydrogen peroxide, which is readily available commercially, in the form of a 60%, 20%, 10% or preferably 5% w/v solution or less. It is most preferred that the activator, peroxygen source and any acidifying component be present in a single composition.

The products may be in liquid form, eg in a non-aqueous liquid medium in which the components may be dissolved or dispersed. For example, activator particles may be coated with protective coatings, eg by microencapsulation processes or Spray coating of solid activator may be suspended in an aqueous, or non-aqueous, solution of a peroxygen source. As an alternative to a solution of a peroxygen source, this component may also be dispersed in the liquid medium, either in a separate liquid phase or in a particulate dispersed phase, with particles of the solid peroxygen source optionally coated with a protective coating. Coated particles of either a peroxygen source or activator may be broken up simply by dilution in water or may be physically broken up by friction.

Preferably, the product is in solid form, e.g. as a mixture of particles of the individual components, or even more preferably it comprises particles each of which comprises all the components. Such particles may be provided by processes similar to those used in the detergent industry, and include, for example, particles prepared by spray drying liquid slurries, by granulation processes using binders, e.g. synthetic or natural polymers (or derivatives), or by melt blending followed by extrusion or other processes.

The composite product may contain other additives, e.g. stabilizers that stabilize the product before use, as well as stabilizers for the stronger oxidizing species formed in the reaction, in particular heavy metal sequestrants. The new product may also contain surfactants that act as wetting agents and inorganic salts that e.g. affect the physical properties of the solid form or act as diluents or serve to increase the rate of disintegration when the product is dissolved. Depending on the form of the product and the end use of the reaction product, e.g. fragrances, abrasives, other ingredients may be included.

Preferably, the product contains the active ingredients in appropriate relative amounts so that when the composition is diluted (or when the compositions are mixed) with water, the first step of the reaction takes place at an optimum rate and with the desired pH. For example, the activator and the peroxygen source are present in relative amounts such that 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 reaction product of the perhydrolysis reaction is preferably used immediately, without removal of any by-products or addition of other materials, in a second step in which it is used as an oxidizing agent, bleaching agent or disinfectant. Sometimes it may be desirable to add additional ingredients for the second step, such as pH adjusting agents and surfactants/wetting agents, which may be cationic, anionic, amphoteric or non-ionic. Other additives that can enhance the second step of the process include disinfectants, biocides, mucolytic agents, enzymes, inhibitors or radical scavengers, abrasives, etc. Cobiocides are particularly useful when the primary goal of the second step is disinfection/sterilization.

The second step of the process of the present invention can be used as a bleaching/disinfecting process, by which we mean any process in which undesirable colour is reduced or removed, uncoloured stains are reduced or removed and/or a substrate is disinfected. The second step can include, for example, processes in which hard surfaces in the home, industry or laboratory are cleaned, fabrics (e.g. during fabric manufacture and dyeing) are cleaned, or the solution is used in water or waste water treatment as a biocide, in pulp and paper bleaching, paper de-inking, wood bleaching, in fibre and fabric manufacture, as a biocide, fungicide, bactericide, sporicide and/or viricide, as a contact lens disinfectant or general disinfectant for use in cleaning a general environment, among others. Furthermore, the second step can be used in food manufacture, e.g. for bleaching flour, drinks or edible oils, in the food and brewing industry, e.g. for cleaning beverage containers. used pipes, or in cosmetic applications, eg hair bleaching or tooth or denture whitening and disinfection. The product of the first step can alternatively be used as an oxidizing agent in an organic synthesis, eg for use in epoxidation reactions of alkenes, or as a catalyst. For certain adhesives it can be used as a hardener.

Since the reaction can be carried out at a relatively low concentration, it can be carried out without special precautions, e.g. in the home or in the laboratory.

Compositions suitable for being diluted directly in water to allow the first and second steps of the reaction to proceed without further additions can be divided into four suitable categories.

The first category includes liquid formulations containing a surfactant. These compositions are suitable for use as hard surface cleaners and other uses where surface active disinfection and/or bleaching is required, e.g., floor cleaning compositions, household and laboratory hard surface cleaners, toilet disinfectants, general toiletry disinfectants, bottle disinfection, including glass and plastic bottles, and pipe cleaning compositions. For most of these uses, it is desirable that the composition be relatively low in foam, although for some, e.g., toilet disinfectants and general toiletry disinfectants, it may be desirable that the composition be relatively high in foam. The use of suitable foaming surfactants is well known in the art. For compositions where low foaming is desired, it may be desirable to include antifoaming agents, e.g. soaps or silicone antifoaming agents. Liquid formulations containing surfactants may be useful in other applications, such as for use in bleaching fibers or fabrics such as diapers, or in fabric manufacture, cellulosic fibers, particularly in paper de-inking operations, and in general cleaning operations.

A second category of compositions includes liquid formulations but do not contain surfactants. These may be useful where surface activity is not required, e.g. in water and waste water treatment, in toilet disinfectants, for use as a swimming pool treatment, for removing color from chemicals, from pulp during paper manufacture or recycling, in general industrial sterilization and in some household sterilization situations, e.g. as a general disinfectant for toiletries, in dental cleaning compositions, in disinfection of glass or plastic bottles or other containers, and in certain environmental cleaning operations. Furthermore, if the composition is to be used in a general industrial oxidation reaction, it may not be desirable for it to contain a surfactant.

The liquid formulations mentioned above may be pourable liquids, which may be aqueous or non-aqueous, or they may be in gel or paste form. Furthermore, the compositions may be biphasic, e.g. in cream form. Alternatively, the compositions could be in the form of a foam (if the composition contains a surfactant), particularly for cleaning hard surfaces in the home, by injecting a gas.

Another category of compositions is in solid form and contains a surfactant. The general uses of these compositions are similar to those for which the liquid formulations containing a surfactant are useful, as mentioned above.

Another category of formulations 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 be more stable during storage in solid form since it is generally easier to keep the bleach activator and the peroxygen donor compound in separate particles and prevent them from coming into contact with each other during storage. Furthermore, it is easier to separate other components of the composition from each other and from the bleach components, especially when storage-sensitive compounds such as enzymes, other biocides or fragrances are present.

Solid compositions may be in the form of particulate mixtures or may be tabletted. Tableted formulations or even granular formulations may include agents to increase the rate of dissolution of the compositions when added to water. The inclusion of suitable components in the tablets, for example, will assist in the disintegration of the tablet. Such components may, for example, induce gummy behavior; a suitable component is sodium bicarbonate or another alkali metal bicarbonate.

The compositions may also contain ingredients that contribute to their usability or stability or that improve their appearance, e.g. thickeners, dispersants, opacifiers, hydrotropes, dyes, fragrances, etc.

The following examples illustrate the invention. In the example, the concentration of the peroxygen source is expressed as the initial concentration of aqueous hydrogen peroxide to which other reactants are added. The molar concentration of the mixtures can be calculated.

example 1 Reaction of TAED and hydrogen peroxide

1.1 This area of investigation was to find a simple method to detect the presence of a stronger oxidizing species than hydrogen peroxide. To this end, a number of indicators containing oxidizable groups were tried to find out which one changed color upon addition of peracetic acid and the oxidizing product of an embodiment of the invention, but not hydrogen peroxide. The results showed that alizarin complexone (AC) was decolorized by peracetic acid but not by hydrogen peroxide. This material was therefore selected as the appropriate indicator.

1.2-Once an indicator had been found, it was possible to carry out the experiments to see if acid-catalyzed perhydrolysis was a possible mechanism. TAED (22.8 g, 0.1 mol) was added to 60% hydrogen peroxide (60 mL, 1 mol). The mixture was stirred for 10 minutes. An aliquot of 2 mL was taken and added to an alizarin complexone solution (0.5 mL). Within a few minutes, the color in the solution was seen to disappear as the indicator was bleached.

1.3 The successful outcome of this experiment led to comparative bleaching experiments being carried out on stained fabric samples. The stains used were red wine, tea and BCI (tea and clay). Comparisons were made between the bleaching performance of 60% H₂O₂, 10% peracetic acid PAAH and TAED/H₂O₂. The performance was assessed by measuring the initial brightness before washing and the final brightness after rinsing and drying the samples by applying an electric iron on wool setting using a Hunterlab D25M colorimeter. The results are given in Table 1.

1.4 A further series of experiments determined at which initial pH the greatest bleaching was observed. These experiments were carried out in 60 ml of 60% H2O2 with 22.8 g of TAED added. The pH of the peroxide was adjusted with sodium hydroxide before the addition of TAED. The highest pH available was 6.95, as above this the peroxide decomposed too quickly. The stains used in these tests were domestic tea stains. These were chosen as they showed the greatest residual colour in the previous tests. The pH of the solutions was measured first after 1 hour of bleaching, after 3 hours and finally after 24 hours. All bleaching experiments were carried out at room temperature. A blank test was carried out using distilled water at pH 6. The results are shown in Tables 2 and 3.

1.5 Experiments were also carried out to determine whether Fe(III) ions had an effect on the bleaching properties. Three systems were set up, one of which was Dequest 2066 (a alkylenepolyaminepolymethylenephosphonic acid) as a sequestrant, one with added 0.5 ml (20 mM) Fe(III) solution and one with hydrogen peroxide alone. These were all carried out at pH 6. The results are shown in Table 3.

1.6 Results and discussion

All experiments were carried out at room temperature in open beakers. The residence time in the bath was 1 hour. Table 1 Table 2 BC1 stains (tea and clay) Table 3 Tea stains

Notes: With 60% hydrogen peroxide and TAED at the upper limit of the acidic pH range, bleaching was visible on contact, with the other solutions bleaching was much slower. Foaming was visible in the reaction as the TAED dissolved, although this process was much faster at higher pH. All reactions containing TAED produced a distinct odor of peracetic acid. Notably, bleaching activity toward AC was still evident after 24 hours at room temperature.

1.7 These results demonstrate that TAED activates peroxide solutions at a range of pH values. The most rapid bleaching behavior is seen at higher pH, probably due to the faster dissolution of TAED and the formation of a stronger oxidizing species under these conditions. The formation of an acidic species upon dissolution of TAED in hydrogen peroxide is indicated by the observed pH change, the solutions only becoming significantly more acidic when TAED is present. Those experiments performed without TAED show very little change in pH over the same time frame. The distinct odor of peracetic acid, which is both quite distinctive and pungent, is also an indication of the presence of this species in the solution. Based on this index, it is considered that peracetic acid is probably the bleaching/oxidizing species responsible for the bleaching effect, although it may be a by-product, an intermediate or the product of a further reaction of another oxidizing species.

1.8 The experiments with and without Fe(III), at pH 6, showed very similar bleaching (percent stain loss was identical). This seems to indicate that iron-catalyzed radical reactions are not important under these conditions. This conclusion is confirmed by the results in the presence of a sequestrant, which were very similar to the results of the experiment without sequestrant at pH 6.

Example 2 TAED and DADHT as activators for peroxygen bleaches in acidic DH for stains in solution and on fabrics 2.1 Experiments 2.1.1 Pattern

The activator/peroxygen source combination method used was 60% hydrogen peroxide in a 10:1 ratio with the activator. Small fabric swatches (20-25 cm2) were used and the stain was chlorophyll. The bleaching experiments were carried out using 10 ml of hydrogen peroxide (60%) adjusted to the required pH using a sodium hydroxide solution. A weighed amount of the activator (16.7 mmol) was then added and the mixture was stirred for 2 minutes to dissolve the activator. The fabric swatch was then added and left for 30 minutes with occasional stirring. After 30 minutes, the samples were removed from the activator solutions, rinsed with deionized water to remove any remaining traces of bleach, dried using the procedure used in Example 1, and the brightness was measured using a Hunterlab D25M colorimeter. The pH of the solution was measured after the fabrics were removed. The results are shown in Table 4.

2.1.2 Dependence of pH on time

Experiments to monitor the relationship between pH and time were performed using TAED and DADHT as activators. The pH of 60% hydrogen peroxide was adjusted to about pH 6. To 20 ml of this solution, 33 mmol of activator was added. The pH was measured as a function of time.

2.1.3 Time-controlled bleaching

Timed bleaching experiments were carried out using the same procedure and quantities as in 2.1.1 above with different residence times of the sample in the bleach solution. Six separate solutions were prepared and A sample was added to each at the same time. After specified periods of time, the samples were removed and rinsed in deionized water. The periods used were 5 min., 10 min., 20 min., 30 min., 1 hour and 2 hours. The final brightness after drying by the conventional method was determined using the Hunterlab. The results are shown in Table 5.

2.1.4 Time/pH bleaching profile

The solutions and samples used were prepared as in the above experiments. Four solutions were prepared and after a set period of time a sample was added to each. The fabric was left in the bleach solution for 5 minutes and then removed and rinsed thoroughly with deionized water. The times at which the samples were added were after 1 min, 15 min, 30 min and 1 hr. A different solution was used for each sample. The activators used were TAED and DADHT. The final brightness after drying the fabric 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 batches of sodium perborate tetrahydrate (17.5 g) mixed with citric acid (8 g) (to lower the pH when reacting with borate) were prepared. To one batch was added TAED (2.6 g). Each of the mixtures was added to 50 mL of deionized water and stirred vigorously. The pH of the solutions was measured after dissolution was achieved. The results are given in 2.2.6 below.

2.2 Results and discussion

2.2.1 It was evident that the chlorophyll stain was resistant to bleaching under these severe conditions, making it a very good stain to use. The fewer stains removed, the better comparisons can be made between the bleaches.

2.2.2 DADHT reacted faster than TAED, see Table 7. The blank tests with peracetic acid, water and hydrogen peroxide (both at pH 6 and pH 1) show that activation occurs when the activator is present and that this is not an effect of the lower pH in the activated solutions (Table 4). The pH drop is a good indication that an acidic species is formed which is not present in the unactivated peroxide solution.

2.2.3 It was seen that the pH decreased rapidly upon addition of activator (Table 6). As would be expected, the rate varied with different activators due to differences in both the acid formed and the rate of perhydrolysis.

2.2.4 Bleaching of samples with different bleaching times showed the expected increase in bleaching with time (Table 5).

2.2.5 The effect of time and pH on the bleaching effectiveness of activated solutions was also investigated. In this case the residence time in the bleach solution was the same (5 min), but the samples were added at different times. Fabric was added to four separate solutions at 1 min, 15 min, 30 min and 1 hour. Each of these samples was a quarter of the same larger sample to ensure a constant substrate concentration. After 5 minutes in the bleach solution, the fabric was removed and rinsed with deionised water. Comparison of the different samples for the same activator provided a measure of the stability, rate of peracid release and pH dependence of bleaching. The relationship between these variables is complex but qualitative comparisons can be made. The results show that TAED gives constant bleaching within the first hour. DADHT, on the other hand, gives better initial bleaching but after 1 hour the effectiveness was similar (Table 7). This seems to show that DADHT is initially perhydrolyzed more rapidly, but after a certain time yields a similar concentration of peracid. This is confirmed by the pH measurements. The pH of the solution containing DADHT decreased more quickly than that of the solution containing TAED. After 20 hours, the numbers are much closer together (Table 6).

2.2.6 It was also evident that activation of sodium perborate solutions occurred under acidic conditions. The use of citric acid and sodium dihydrogen phosphate allows the preparation of acidic solutions of perborate which also provide some buffering. It was evident that the pH of the solutions was acidic (pH 5.1) and more stable than observed for more concentrated peroxide solutions. The pH of the activated and unactivated solutions was very similar. Table 4: Activation of acid peroxide with different activators Table 5: Effect of different bleaching times on the brightness and pH of the solution Table 6: Effect of activators on the pH of the solution as a function of time Table 7: Bleaching effectiveness versus time

DADHT - 1,5-Diacetyl-2,4-dioxohexahydro-1,3,5-triazine

Example 3 Biocidal activity of activator/hydrogen oxide mixtures

3.1 The assessments were carried out in a test tube situation following the principles of BS 6471:1984.

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

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

3.4 To achieve concentrations comparable to the 150 mg/l PPA reference solution, sample solutions of the formulations were prepared using TAED in the amount of 0.0225 g TAED in 100 ml 1% hydrogen peroxide solution as shown in the table below. In Example 3.6, the sample solution was aged for 24 hours before use. The other sample solutions were used immediately.

3.5 1 ml of the test bacterial culture was added to 9 ml of the appropriate formulation, mixed and left for 5 or 10 minutes at room temperature or at 40ºC (as indicated in the table).

3.6 1 ml of this liquid was transferred to 9 ml of a deactivator containing 50 g/l sodium thiosulfate and 0.25 g/l catalase in distilled water. The deactivator was filter sterilized using 0.45 µm membrane filters.

3.7 From these deactivated fluids, 10-fold sequential dilutions were made using Maximum Recovery Diluent (MRD). Pour plates were prepared using 1 ml amounts of each dilution mixed with molten Plate Count Agar (PCA).

3.8 For control purposes, the procedure was repeated using 1% hydrogen peroxide as a control for the two formulations and sterile distilled water as a control for PAA.

3.9 All plates were incubated for 48 hours at 37ºC, after which the number of colonies visible on each plate was counted. The reduction in the number of CFU compared to the control solution is calculated. The results give the log (base 10) of the control count/sample count. If the number is "greater than" the actual number, this indicates that the CFU count on the test plate was below the minimum that can be quantified using this method. Results Table 8 - Efficacy as a biocide

3.10 TAED/H₂O₂ generally did not appear to be particularly effective compared to PAA at room temperature for short contact times, although some reduction was seen against E. coli and Staph. aureus.

3.11 Increasing the temperature to 40ºC improved the performance of TAED.

3.12 Increasing the contact time from 5 minutes to 10 minutes etc. improved the results.

3.13 Aging the solution for 24 hours prior to use resulted in the same improvement as increasing the temperature. This improvement may be a consequence of the slow release characteristics of the system.

Example 4 Production of acidic percarbonate solutions

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

4.2 The following formulations were added to 1 litre of cold water. In each case 1.85 g of TAED was included as activator. The amount of percarbonate was varied, the amount of citric acid added being such that approximately the same pH was obtained in each test. The presence of hydrogen peroxide was determined by iodometric titration as described in Example 5 below. Table 9

Example 5 Acids and anhydrides as activators 5.1 Use of acetic acid (comparison) and TAED (invention) as acetyl donor

The following experiments were performed using 50 ml of 10% w/v hydrogen peroxide at room temperature with activator and compared against controls. Chlorophyll-spotted specimens were used as substrate.

Reflectance was measured using an ICS Texicon Spectra Flash 500 (a colorimeter using the CIELAB system) using software version 4.70.

The initial pHs of these solutions were recorded.

The samples were left in the solution for 75 minutes.

After rinsing with deionized water and drying as in the previous examples, the brightness was compared to an unbleached sample with chlorophyll stains. Results Table 10

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

5.2 Use of acetic anhydride (comparison) and TAED (invention)

Acetic anhydride is a widely used source of peracids under laboratory conditions. However, this material is 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 used in the above experiments (5.1) with acetic acid. Hydrogen peroxide was used at a concentration of 10%. A series of spotty patterns were used, these being chlorophyll, curry and blackberry. Samples were also assayed for peracetic acid using an iodometric titration.

5.2.1 Bleaching of spotty patterns

In the following experiments, the parameters shown in Table 10 Peroxide/activator combinations are used to make the bleach solutions.

All experiments were conducted at ambient temperature. Comparative formulation 5.2.4 was used only in the first two experiments. Reflectance was measured as in 5.1. The table shows the differences in reflectance. A positive value means that the bleached sample is lighter than the stained control sample and a minus sign means that it is darker.

Experiment A

Chlorophyll-stained samples were added to these solutions and allowed to bleach for 75 min. After this time, the samples were removed and washed in water to remove any remaining active species.

Experiment B

Samples with chlorophyll stains were added to the solutions used above and left overnight for 17 hours to bleach. The samples were rinsed. The pH of the bleach solution was measured after the fabrics were removed.

Experiment C

Fresh solutions were prepared using the first three compositions and allowed to stand overnight before adding chlorophyll-stained samples. Fabrics were allowed to bleach for 75 min and then removed and rinsed.

Experiment D

This experiment was the same as Experiment A, but using curry-stained samples. No water/acetic anhydride solution (Comparison 5.2.4) was tested.

Experiment E

This experiment was the same as Experiment A using blackberry stained samples. No water/acetic anhydride solution (Comparison 5.2.4) was tested.

5.2.2 Iodometric titration

The peracetic acid concentration of solutions 5.2.1 and 5.2.2 (comparison) used in Experiment E was determined at predetermined time intervals using an iodometric titration on ice so that hydrogen peroxide alone gives minimal values, the titration being carried out as soon as possible after preparation of the titration mixture. 5.2.3 Results Table 11

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

5.3. Determination of peracetic acid formed by acetic anhydride (comparison) and TAED

The respective concentration of oxidizing agent was determined at time intervals using an iodometric titration on ice. The solutions studied were those used in experiment 5.2.1 and comparative experiment E 5.2.2, as 5.3.1 and 5.3.2 respectively. The iodometric titration performed was the one used for the calibration of peracetic acid. The solution to be studied is placed in a flask containing potassium iodide, acetic acid and ice. The iodine released is titrated with sodium thiosulfate. Table 12

From the above results it can be seen that the TAED activated solution gives a lower initial strong oxidant concentration. However, over time, in this case 7 days, the strong oxidant concentration in the TAED solution increases while the acetic anhydride solution loses peracid. After a few days the strong oxidizing acid concentrations are higher in the TAED containing solution. After about 140 hours there is still a large amount of undissolved TAED. This makes this a very good slow release process.

Example 6 Perborate/TAED in a surfactant-free composition

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

1.8 g TAED

2.58 g sodium perborate monohydrate

without or with 1.58 g sodium bicarbonate

different amounts of citric acid or sodium dihydrogen orthophosphate as acidifying agent. The pH of the solution with varying amounts of acidic component was measured after 10 min. The results are shown in the following table. TABLE 13

The bleaching performance of some of the solutions was determined on unglazed tea-stained tiles. The bleach solution is applied to one half of the tile and the difference in whiteness, as determined using a Hunter Lab instrument, between the two halves is determined. The value is reported as ΔW. The Hunter Lab instrument is set to the CIE tristimulus XYZ scale. The W reading represents Z percent brightness.

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

Example 7 Surfactant - 3 compositions containing perborate and various activators

Mixtures containing 2.58 g of gnatium perborate monohydrate, 3 g of citric acid, 1.6 g of sodium bicarbonate and 1.8 g of TAED or an equivalent weight of activator comprising N-benzylcaprolactam (NBC) or triacetylethanolamine (TAE) or TAED-containing grains were dissolved in 1 liter of water. The peracid release rate was monitored as above using iodometric titration on ice. The results are given in the table below. Table 14

* Result after 3 days

Granule 1 is made of 90-94% TAED, carboxymethylcellulose binder and not more than 2% water formed Mykon ATC (available from the applicant company) and 95% have a particle size in the range of 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% methylenephosphonic acid sequestrant and not more than 2.5% water, with 95% having a particle size in the range of 0.2 to 1.6 mm.

The temperature during the reaction was 40ºC.

Example 8 Storage stability of compositions containing surfactants

The following compositions were prepared by mixing 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 using a conventional Avox titration. The percentage loss of available oxygen is given in the table below. TABLE 15

Example 9 Oxidizing agent concentration for different activators at pH 6.3

Mixtures comprising 2.58 g of sodium perborate monohydrate, 1.58 g of sodium bicarbonate and 2.1 g of sodium dihydrogen orthophosphate and 1.88 g of activator were dissolved in 2 liters of water. The concentration of strong oxidizing agent in the resulting solution was measured after different time intervals using the iodometric titration mentioned above. The results are given in the table below. Table 16

These results demonstrate that TAED provides excellent sustained release of strong oxidant, which continues to increase even after one hour.

Example 10

A solution of a flash liquid and a similar solution but with an added amount of a bleach enhancer mixture formed from TAED (at a concentration of 1.88 g/l), sodium perborate monohydrate (at a concentration of 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 to half of a stained tile with a brush 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 respectively were 4.0 and 9.7, respectively. The ΔW values for enhanced flash were 4.8 and 13.5, respectively.

Claims (20)

1. A process wherein a peroxygen source is reacted with an activator compound which is an N-acyl compound having at least two carbon atoms in the acyl group in a first step in aqueous solution under acidic conditions to form an oxidizing product which is a stronger oxidizing agent than the peroxygen source. 2. The process of claim 1, wherein the activator compound has the formula I wherein R¹ is an alkyl, alkenyl, aralkyl, alkaryl or aryl group, each of these groups having up to 24 carbon atoms and may be substituted or unsubstituted, and -NR²R³ is a leaving group, wherein R² and R³ are independently selected from H, C₁₋₂₄ alkyl, alkenyl, aralkyl, alkaryl or aryl groups and carbonyl-containing radicals having at least 2 carbon atoms, wherein the carbonyl group is bonded to the nitrogen atom in Formula I, wherein R² and R³ may be bonded together as a cyclic group and/or R¹ may be bonded to either R² or R³ to form a cyclic group. 3. A process according to claim 2, wherein R¹ is an aliphatic group, preferably a C₁₋₁₈ alkyl or alkenyl group, or is an aryl group. 4. A process according to any preceding claim, wherein the product containing stronger bleaching species is subsequently used as a bleaching and/or disinfectant in an aqueous environment at a pH of less than 7. 5. A process according to any preceding claim, wherein the product of the first step is subsequently used as an oxidizing agent in an oxidation step which is carried out without removing any by-products from the first step. 6. A process according to any preceding claim, wherein the peroxygen source is selected from hydrogen peroxide, organic peroxides and inorganic persalts. 7. A process according to any preceding claim, wherein the pH in the first step at the start of the reaction is less than 6.5, and preferably more than 2.0, more preferably more than 5.0. 8. A process according to any preceding claim, wherein the concentration of the peroxygen source in the reaction mixture of the first step is less than 10 M, preferably less than 5 M, more preferably less than 2 M, and preferably at least 0.01 M, even more preferably less than 1 M and at least 0.05 M, especially at least 0.1 M. 9. A process according to any preceding claim, wherein the temperature in the first step of the reaction is in the range of 0 to 95°C, preferably at least 20°C and up to 80°C, more preferably up to 60°C. 10. Use of a composite product comprising a peroxygen source and an N-acyl activator compound having at least two carbon atoms in the acyl group and, if necessary, an acidifying component capable of rendering an aqueous solution of the peroxygen source and the activator compound acidic, to form the reactant mixture for the first step of a process according to any preceding claim by adding the product to water to dissolve the peroxygen source, the activator and the acidifying component to form an acidic solution. 11. Use according to claim 10, wherein the activator compound is present in the product in an amount sufficient to provide 0.1 to 5 equivalents of acyl groups per mole of peroxygen source, preferably up to 1.0 equivalents. 12. Use according to claim 10 or 11, wherein the acidifying component is present in the product in an amount such that the pH is less than 6.5 when the components of the product are dissolved in aqueous solution, the peroxygen source being present in a concentration in the range of 0.01 to 10 M (preferably in the range of 0.1 to 1.0 M). 13. Use according to any one of claims 10 to 12, wherein the activator compound is as defined in claim 2 or claim 3. 14. Use according to any one of claims 10 to 13, wherein the peroxygen source is selected from hydrogen peroxide, organic peroxides and inorganic persalts. 15. Use according to any one of claims 11 to 14, wherein the composite product includes a surfactant. 16. Use according to any one of claims 10 to 15, wherein the aqueous product is used as an oxidizing agent, preferably as a bleaching and/or disinfecting agent. 17. An aqueous acidic solution comprising a peroxygen source, an N-acyl activator compound having at least 2 carbon atoms in the N-acyl group, a surfactant and, if necessary, an acidifying component. 18. Use of the solution of a product according to claim 17 as an oxidizing agent, preferably as a bleaching and/or disinfectant. 19. A process wherein a composite product as defined in any of claims 10 to 16 is diluted with water to form an acidic solution. 20. A process according to claim 19, wherein the aqueous acidic solution formed thereby is used as a bleaching agent, disinfectant, Sterilizing agent or biocide is used, the pH remaining less than 7 during use of the solution.