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WO1996001309A1 - Bleaching compositions - Google Patents

Bleaching compositions Download PDF

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Publication number
WO1996001309A1
WO1996001309A1 PCT/GB1995/001535 GB9501535W WO9601309A1 WO 1996001309 A1 WO1996001309 A1 WO 1996001309A1 GB 9501535 W GB9501535 W GB 9501535W WO 9601309 A1 WO9601309 A1 WO 9601309A1
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WO
WIPO (PCT)
Prior art keywords
peroxide
composition
component
transition metal
sequestering agent
Prior art date
Application number
PCT/GB1995/001535
Other languages
French (fr)
Inventor
Vincent Brian Croud
Stephen James Tompsett
Susan Jane Scarborough
Original Assignee
Warwick International Group Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Warwick International Group Limited filed Critical Warwick International Group Limited
Priority to AU28011/95A priority Critical patent/AU2801195A/en
Publication of WO1996001309A1 publication Critical patent/WO1996001309A1/en

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Classifications

    • CCHEMISTRY; METALLURGY
    • C11ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11DDETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
    • C11D3/00Other compounding ingredients of detergent compositions covered in group C11D1/00
    • C11D3/39Organic or inorganic per-compounds
    • C11D3/3947Liquid compositions

Definitions

  • This invention relates to aqueous alkaline oxidising compositions which contain peroxide.
  • the invention particularly relates to concentrated bleaching compositions which contain peroxide and which can be diluted by the user to obtain a washing composition.
  • Acidic compositions are known, but it is desirable to produce alkaline peroxide-containing aqueous liquids because the activity of the peroxide is enhanced.
  • compositions In GB-A-2072643 stability of the compositions is obtained using a combination of non-aqueous solvent (ethanol) , amino compounds substituted by acetate or methylene phosphonates and hydroxy alkyl diphosphonates, particularly with a polyhydroxy carboxylate, preferably gluconate or an amino acetate.
  • ethanol non-aqueous solvent
  • amino compounds substituted by acetate or methylene phosphonates and hydroxy alkyl diphosphonates particularly with a polyhydroxy carboxylate, preferably gluconate or an amino acetate.
  • the particular difficulty of preventing the hydrogen peroxide from decomposing on storage in an alkaline composition is discussed.
  • the products are prepared by introducing each of the components of the composition sequentially or concurrently into a mixing tank and agitating.
  • compositions are prepared by forming a mixture of surfactant, then adding all of the other ingredients, with the hydrogen peroxide being added last.
  • stabilisation is achieved using a combination of isopropanol and an aminomethylene phosphonate or hydroxyalkyl diphosphonate, optionally with a polyhydroxy aliphatic carboxylate.
  • stabilisation is achieved by introducing into a concentrated aqueous acidic solution of hydrogen peroxide, amino poly(alkylene phosphonic acid) or a salt thereof, storing the mixture until the aminopoly(alkylene phosphonic acid or salt has been converted to a derivative in the acidic solution and then diluting the concentrate with alkali to form a mildly alkaline solution.
  • an aqueous alkaline hydrogen peroxide composition is buffered and stabilised using cyclohexane- 1,2-diaminotetramethylenephosphonic acid.
  • the phosphonic acid stabiliser was introduced into a buffered solution and shortly after an aqueous solution containing tetradecyldimethylamine oxide, a perfume and water and then aqueous hydrogen peroxide solution were added to the stabiliser-containing mixture and finally, sodium hydroxide was added until the composition reached a pH of 8.5.
  • a solid peroxide bleaching composition is prepared incorporating, for stability a chelating agent capable of forming a water-soluble or poorly water-soluble compound.
  • the chelating agent is either added to the final composition or it is present during the reaction of sodium carbonate, sodium pyrophosphate or sodium borate with hydrogen peroxide to form the inorganic bleaching agent.
  • the prior art may improve the stability of hydrogen peroxide-containing compositions under alkaline conditions
  • the gain in stability resulting from the prior art disclosures is short term only and often places considerable limitations on the detergent formulations which can be used so that the overall detergent properties of such compositions may not be satisfactory.
  • the present invention provides for long term storage stability and significantly improves the reproducibility of its attainment.
  • the invention also overcomes previous limitations in possible formulations and general detergent performance properties by enabling the use of components previously found to degrade the peroxide to unacceptably low levels.
  • the inventors of this invention have found that a surprising advantage can be achieved by incorporating a sequestering agent into such a composition using a carefully controlled preparation process for the composition.
  • a method for preparing a peroxide-containing concentrated aqueous alkaline oxidising composition in which components comprising an aqueous liquor and other optional components are mixed with peroxide, characterised in that prior to mixing with the peroxide, every component of the mixture which potentially includes transition metal ions which will contact the peroxide in the composition is pre-treated in a pre- treatment step by contact in an aqueous liquid with a sequestering agent for at least 45 minutes.
  • the present invention also includes a method for preparing a peroxide-containing concentrated aqueous alkaline oxidising composition in which components comprising an aqueous liquor and other optional components are mixed with peroxide, characterised in that prior to mixing with the peroxide, every component of the mixture having a transition metal ion content such that in the oxidising composition it will produce an AvOx (available oxygen from peroxide) loss of 50% or more, or even 25% or more, or most preferably every component which will produce an AvOx loss of 5% or more from the oxidising composition over 12 weeks at 37 ⁇ C and 80% relative humidity (RH) is pre-treated in a pre-treatment step by contact in an aqueous liquid with a sequestering agent for at least 45 minutes.
  • AvOx available oxygen from peroxide
  • the present invention has the additional advantage that it enables preparation of stable compositions which do not require incorporation of an additional, non-aqueous solvent such as an alcohol.
  • Alcohols are disadvantageous because they reduce the flash-point of the compositions. This is a particular problem due to the strongly oxidising (and therefore potentially explosive) nature of peroxides.
  • alcohols are disadvantageous because their use introduces additional processing costs.
  • the present invention may also be of value in preparing non-aqueous compositions and/or in which the pre- treat ent step is carried out in a non-aqueous solvent.
  • the oxidising composition is generally a bleaching composition.
  • the peroxide will be at least partially soluble in the composition and may be one or mixtures of more than one of hydrogen peroxide, organic peroxides and inorganic persalts which liberate hydrogen peroxide in water.
  • Suitable examples of inorganic persalts include alkali metal salts of perborate, persulfate, perphosphate or percarbonate.
  • This invention has been found to be particularly advantageous because it enables the use of hydrogen peroxide which, being a liquid under normal conditions of use is a particularly easily decomposed form of peroxide and is therefore particularly problematic.
  • Hydrogen peroxide is particularly preferred as it has a higher rate of reaction because it does not require dissolution time.
  • Pre-formed peracids may also be used as the peroxide component. Examples are perbenzoic or peracetic acid.
  • a pre-formed peracid may be used in addition to a peroxide salt or hydrogen peroxide and if so, the peracid may be encapsulated.
  • the concentration of peroxide in the final composition will generally be such as to provide a concentration equivalent to hydrogen peroxide (100%) in an amount of at least 0.5% preferably at least 1%, most preferably at least 3%. Generally it will be no greater than 15%, preferably below 10% and most preferably below 7% by weight of the oxidising composition.
  • the aqueous liquor and alkali for preparing the aqueous alkaline composition may be provided in the form of an aqueous solution of alkali or may be introduced separately as water and alkali components.
  • Alkalinity in the compositions of the present invention is generally provided by the addition of any conventional alkali. In particular hydroxides, especially alkali metal hydroxides are used.
  • the amount of alkali used is such that the pH of the final composition will be at least 7, generally being no greater than 13.5.
  • the pH of the final composition will be at least 8, or even at least 8.5.
  • the pH of the final composition will be up to around pH 11, most preferably from pH 9 to 10.5.
  • the method according to the present invention may be used to prepare an oxidising composition for any application.
  • the other, optional components for preparing the oxidising composition may comprise any of the typical additives used in oxidising, especially detergent compositions, for example surfactants, builders, bleach activators, electrolytes, hydrotropes, decouplingpolymers, optical brighteners, dyes, fragrances, anti-redeposition agents, dye-transfer inhibitors, enzymes and/or free radical scavengers and/or additional peroxide stabilisers.
  • detergent compositions for example surfactants, builders, bleach activators, electrolytes, hydrotropes, decouplingpolymers, optical brighteners, dyes, fragrances, anti-redeposition agents, dye-transfer inhibitors, enzymes and/or free radical scavengers and/or additional peroxide stabilisers.
  • Buffers such as carbonate compounds may also be included.
  • perhydrolytically or hydrolytically unstable materials if incorporated into the oxidising composition are preferably suitably protected, for example by releasable encapsulation, prior to incorporation.
  • the oxidising compositions of the present invention will be bleaching compositions, especially cleaning compositions, preferably they will contain at least surfactant.
  • the surfactant may be anionic, nonionic or cationic or mixtures of such surfactants.
  • anionic surfactants has been found to cause the most difficulties with respect to rate of decomposition of peroxide in an alkaline peroxide composition.
  • one of the particular advantages which have been found is that anionic surfactants can be incorporated into the oxidising compositions while surprisingly, maintaining good stability of the peroxide composition.
  • Suitable anionic surfactants include any surfactant useful in a detergent for example salts of sulphonic or monoesterified sulphuric acids such as alkyl benzene sulphonate, alkyl sulphates, alkyl ether sulphates, olefin sulphonates, alkyl phenol sulphates, alkyl phenol ether sulphates, alkyl ethanolamine sulphate, alkyl ethanolamine ether sulphates, alpha sulpho fatty acids or esters, each having at least one alkyl or alkenyl group from 8 to 22, more usually 10 to 20 aliphatic carbon atom and the alkyl or alkenyl groups preferably being straight chain primary groups.
  • sulphonic or monoesterified sulphuric acids such as alkyl benzene sulphonate, alkyl sulphates, alkyl ether sulphates, olefin sulphonates, alkyl
  • anionic surfactants include fatty alkyl sulphosuccinates, fatty alkyl ether sulphosuccinates, acyl sarcosinates, acyl taurides, and paraffin sulphonates.
  • the preferred anionic surfactants are salts of alkali metals or alkaline earth metals, preferably sodium.
  • Other salts include ammonium, monoethanolamine, diethanolamine, triethanolamine and alkyl amines having up to 7 aliphatic carbon atoms.
  • anionic surfactants for use in the present invention include sodium dodecylbenzene sulphonate, potassium hexadecylbenzene sulphonate, sodiumdodecyldimethylbenzy1 sulphonate, sodium lauryl sulphate, ammonium lauryl onoethoxysulphate, monoethanolamine cetyl ethoxylate sulphate and paraffin sulphonates.
  • Suitable nonionic surfactants include for example alkanolamides (such as CIO to C20) and/or ethoxylated alcohols, carboxylie acids, amines, alcohol amides, alcohol phenol, glyceryl esters, sorbitan esters, phosphate esters etc.
  • Suitable cationic surfactants include for example quaternary amines, imidizolines and quaternised imidizolines. Amphoteric surfactants may also be used.
  • surfactants are generally incorporated into the composition of the present invention in amounts of at least 1%, preferably at least 3%, or even at least 5%, more preferably at least 10% by weight of the finished oxidising composition.
  • the amount of surfactant in the composition will be up to 60% by weight and most preferably up to 50% by weight.
  • the formulation will be a heavy-duty laundry detergent containing a high proportion of active components, including at least 10% by weight surfactant, preferably at least 15% or even 25%.
  • the formulation may therefore be for example either isotropic or structured. Structured compositions may include decoupling polymers, optionally with electrolyte and isotropic compositions may include hydrotrope optionally with electrolyte.
  • the optional, other components of the composition are therefore selected according to the desired formulation.
  • any builder which is conventional for use in detergent compositions may be used in the compositions,of the present invention such as phosphates, carbonates, zeolites, acetates, citrates, etaphosphate, pyrophosphate, phosphonate, EOTA and/or polycarboxylates or silicates.
  • the builder may also contribute to the electrolyte concentration in the composition.
  • Builders such as silicates may also contribute to the alkalinity of the compositions of the present invention.
  • a preferred builder is an alkali metal citrate salt.
  • Certain builders may interfere with the sequestration of transition metal ions by the sequestering agents thereby decreasing the stability of the formulations, for example zeolites, phosphates, EDTA, polycarboxylates and/or phosphonates. If, for performance reasons, these are preferred components they should be included in a form such as to prevent this interference but still in a form which can be released into the wash bath, preferably by encapsulation.
  • Builders may be incorporated in the composition in amounts of from 0 to 40% by weight of the total composition, preferably at least 2%, most preferably at least 5%, generally no greater than 30% and preferably no greater than 25% by weight of the final composition. Bleach activators may be used in the composition.
  • any of the N-acyl or o-acyl compounds which are conventionally used as bleach activators is suitable. Particularly preferred compounds are for example as described in EP-A- 0331300 and EP-A-0332294. Examples of other well known and useful bleach activators include for example TAEO. Generally the activator if any will be incorporated in amounts of from 0.1% to 10%, preferably in amounts greater than 0.5% or even 1%. Generally the amount of activator will be no greater than 5%, or even 2.5% by weight of the final composition.
  • Bleaching catalysts or enzymatic activators may also be used in the compositions of the present invention. These are generally required at lower concentrations than the N-acyl or O-acyl activators, for example below 0.1%.
  • One or more of the optional components may be unstable under aqueous alkaline conditions or react with peroxide under aqueous alkaline conditions. This may be a particular problem for builders and/or activators and in some cases it may be advantageous to encapsulate one or more of the optional components for inclusion in the aqueous composition.
  • a suitable encapsulation technique for activators and suitable activators are described in for example British patent application number 9323634.7.
  • the electrolytes which may be used are any electrolytes commonly used in this type of composition either singly or mixtures of more than one electrolyte, and in amounts necessary to provide the desired degree of physical stability or viscosity to the composition.
  • the hydrotropes and decoupling polymers which are used are conventional and in the desired amounts for physical stability.
  • thickening agents may also be incorporated in the composition as an additional optional component.
  • any of the above components may be in the solid form, suspended in the aqueous liquid. However, preferably all of the components are in the form of liquids, most preferably as aqueous solutions. As explained above, some components may react with peroxide or be unstable in alkaline conditions. These are preferably incorporated as encapsulated solid materials.
  • Every component of the mixture potentially including transition metal ions which will contact the peroxide in the composition is pre-treated in the pre-treatment step.
  • Any solid components for suspension in the compositions may include transition metal ion impurities on their surface and if so, pre-treatment will be necessary to prevent decomposition of the peroxide in the composition.
  • any transition metal ions inside the particle which will not contact the peroxide on storage in the composition do not require sequestration and are not generally sequestered in the pre- treatment step. Therefore, generally every liquid component in the mixture having a transition metal ion content of at least 0.5ppm, preferably every component having a transition metal content of at least 0.05ppm and most preferably every component having a transition metal ion content of at least O.Olppm is pre-treated in the pre-treatment step. For any particulate solids, those having transition metals in these amounts on their outer surfaces or which will when in the aqueous liquid release transition metal ions in these quantities are generally pre-treated.
  • components which contain 0.5ppm, or above preferably all those which contain 0.05ppm and most preferably all those components which contain O.Olppm or above, or even amounts above O.OOlppm, transition metal ion impurities which are active in peroxygen decomposition under alkaline conditions are pre-treated in the pre- treatment step.
  • each component in the composition will be treated if the transition metal ion impurities in that component are such as to produce an AvOx (available oxygen from peroxide) loss of 50% or more from the oxidising composition over 12 weeks at 37 ⁇ C and 80% RH.
  • an oxidising composition is prepared containing all of the components except that to be tested, all of the components having been either pre-sequestered or purified so that they do not contain transition metal ion to degrade the hydrogen peroxide.
  • the component for testing is added to the oxidising composition, without having undergone a pre-treatment step.
  • the AvOx in the composition is measured immediately after addition of the component to be tested to find the initial AvOx. From the time of addition of the component to be tested, the AvOx loss of the composition is monitored over 12 weeks, the composition being maintained at conditions of 37°C and 80% relative humidity.
  • a control composition is also monitored for AvOx loss.
  • the control composition is identical to that being monitored (which includes the component to be tested) , with the exception that the control composition does not contain the component to be tested.
  • the AvOx loss of the control composition over 12 weeks at 37°C and 80% RH is subtracted from the AvOx loss over 12 weeks under the same conditions for the composition including the component being tested to arrive at a result indicating the AvOx loss from the oxidising composition due to the component being tested.
  • the resulting AvOx loss due to the component being tested over the 12 week period is 50% or more of the initial AvOx, then for preparation of effective oxidising compositions, that component should undergo the pre- treatment step.
  • every component which produces an AvOx loss of 30% or more, 25% or more or even 10% or more over 12 weeks at 37°C and 80% RH in accordance with the test described above will be pre-treated.
  • the final oxidising composition prepared will be such that transition metal ion impurities are pretreated to ensure the AvOx loss over 12 weeks at 37°C will be no greater than 50%, preferably no greater than 40% and most preferably no greater than 25% of the initial total AvOx of the composition, measured after preparation of the composition and prior to storage.
  • AvOx loss is measured by permanganate titration to detect remaining available oxygen and then by subtraction from the initial available oxygen.
  • each individual component for forming the mixture may be treated individually.
  • groups of mixtures of different components or, preferably, all of the components of the mixture are mixed together to form a pre-mix and the pre-mix is pre- treated prior to incorporation of the peroxide.
  • contact with the sequestering agent will be for at least 1 hour or even at least 2 hours.
  • Contact may be for at least 6 hours, preferably at least 12 hours and most preferably at least 24 hours. It has been found that satisfactory results can be achieved by allowing contact with the sequestering agent for as little as 45 minutes. However, preferably the contacting step is for a longer period in order to attain good long term stability and reproducibility.
  • Contact is by the addition of the sequestering agent or mixture of sequestering agents to the component or mixtures of components in an aqueous environment and the component and sequestering agent mixture is allowed to stand for the contact time.
  • the aqueous environment may be agitated, for example by stirring or other agitation means. It has been found that in some cases, agitation reduces the time required for effective sequestration of the transition metal ions.
  • the solid is dissolved in a solution, preferably aqueous, containing the sequestering agent(s) or to which the sequestering agent(s) is added, the solution is then left for the contact time and subsequently, the crystalline solid is recrystallised out of solution by any conventional means.
  • the crystalline solid may then be redissolved or added directly to the aqueous composition.
  • the time of contact between the components for preparing the composition and the sequestering agent in the pre-treatment step may vary depending upon other factors. For example, an increase in temperature may reduce the time needed for pre-treatment.
  • the temperature conditions in the pre-treatment step will be the same as or as close as possible to those of the storage of the final oxidising composition, (generally ambient 15- 25°C) , to ensure maximum stabilisation of the composition.
  • the temperature for the pretreatment step will be between 10 and 50°C, preferably being no more than 10°C preferably no more than 5 ⁇ C higher or lower than the temperature at which the final composition will be stored.
  • transition metal ion impurities from each of the components which will form the final oxidising composition form complexes with the sequestering agents. It is postulated that upon initial contact of the transition metal ions with sequestering agent, the kinetically preferred complexes are formed. After a time delay of at least 45 minutes, preferably at least 1 or even two hours, sufficient time is allowed to enable formation of the thermodynamically most stable complex. The time delay also allows those metals which undergo slow ligand exchange reactions, time to react with the sequestering agent or mixture of sequestering agents.
  • any transition metal ion impurities which are active in peroxide decomposition have a significantly reduced effect on the decomposition of hydrogen peroxide and surprisingly enhanced stability is obtained as a result of this effective sequestration.
  • the peroxide itself is also pre-treated by addition of sequestering agent(s) to a peroxide solution as described above.
  • the peroxide is provided in the form of a salt, recrystallisation of the salt can be performed as described above.
  • the peroxide is hydrogen peroxide and the pre-treatment step is carried out by contact of sequestering agent with hydrogen peroxide solution.
  • the aqueous liquid for the pre-treatment of the components with sequestering agent is alkaline.
  • a pretreated alkaline solution used to adjust alkalinity will inevitably have a higher pH than the final oxidising composition.
  • the pH of the aqueous liquid within which the contact with the sequestering agent occurs has a pH within one pH unit of the pH of the final oxidising composition, most preferably within 0.5 pH units of the final oxidising composition. This is particularly preferred for pre-treatment of surfactant and/or builder component.
  • alkaline pH and pH which is close to the pH of the final oxidising composition is preferred because it enables the production of the thermodynamically most stable complexes of the transition metal ions under the conditions which the transition metal ions will encounter in the final oxidising composition. This ensures that the thermodynamically most stable complexes will form prior to incorporation in the composition, thereby leading to the most stable final composition.
  • the peroxide may be added to any of the components or pre-mixtures of components for incorporation into the final composition. However, it must not be added to components which require pre-treatment and which have not yet been pre-treated. Where the components require pre-treatment, the peroxide should only be contacted with such components after they have undergone the pre-treatment step.
  • the peroxide is added after all of the other components of the mixture have been added.
  • final pH adjustment of the oxidising composition may be required to restore alkalinity. This is generally by the addition of further alkali solution, pre-treated where necessary.
  • the sequestering agent sequesters the transition metal ions so that they are no longer catalytic in peroxygen decomposition i.e.form complexes with the transition metal ions that are stable with respect to peroxygen decomposition. Suitable sequestering agents can be selected by testing the stabilising effect of a particular sequestering agent on transition metal ions in a hydrogen peroxide solution.
  • the sequestering agent comprises one or more chosen from those which form a stable complex with cobalt ions under alkaline conditions, particularly preferred examples include dimethylglyoxi e (DMG) or dipyridylamine (DPA) . It is particularly preferred to incorporate into the final composition at least one of those sequestering agents mentioned above and in addition, at least one sequestering agent which forms a stable complex with copper and/or iron and/or manganese ions under alkaline conditions.
  • DMG dimethylglyoxi e
  • DPA dipyridylamine
  • sequestering agents which are stable under alkaline conditions and in particular, suitable compounds are aminopoly(alkylene phosphonic acid) or salts, such as 1,2-cyclo-hexane diaminotetra(methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) and ethylene diamine tetra (methylene phosphonic acid) or salts thereof.
  • suitable compounds are aminopoly(alkylene phosphonic acid) or salts, such as 1,2-cyclo-hexane diaminotetra(methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) and ethylene diamine tetra (methylene phosphonic acid) or salts thereof.
  • suitable compounds are aminopoly(alkylene phosphonic acid) or salts, such as 1,2-cyclo-hexane diaminotetra(methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) and ethylene diamine tetra (methylene phosphonic acid) or
  • the amount of sequestering agent used depends to some extent on the amount of transition metal impurities in the component of the composition.
  • the sequestering agent will be present in amounts from at least 0.01% by weight of the composition for pre-treatment. Generally the total amount of sequestering agent will be at least 0.02 or even at least 0.03% by weight. The amount of sequestering agent may be up to 1% by weight, or even higher. This should be sufficient sequestering agent for complexing any transition metal impurities in the composition although more may be added if a high proportion of transition metal ion impurities is present as indicated by loss of AvOx, as explained above. Addition of excess sequestering agent can lead to loss of stability.
  • the composition will contain at least 0.005% of the sequestering agent which forms a stable complex with cobalt ions under alkaline conditions and at least 0.01% by a weight of the total composition of at least one sequestering agent which forms a stable complex with iron, copper and/or manganese, preferably each of these ions under alkaline conditions.
  • the proportion of transition metal ion impurities is particularly high in anionic surfactants and in builders. Therefore, in the separate pre-treatment of surfactant and/or builder, or in a pre-mix which includes for example at least 10% by weight surfactant and/or builder, the concentration of sequestering agent used in the pre-treatment step may be increased and will generally be at least 0.04% by weight of the total composition in the pre-treatment step.
  • components to be added to the mixture are known to be substantially free of transition metal ion impurities, for example in amounts below 0.5 ppm or even 0.05 ppm, most preferably which contain such transition metal impurities in amounts below O.Olppm, no pre-treatment with sequestering agent may be necessary for example, where deionised water or pre-purified components are used.
  • all of the components of the oxidising composition are mixed to form a pre-mix.
  • the pre-mix then undergoes a pre-treatment step by the addition of sequestering agent(s) in an amount of at least 0.04% by weight and at a pH of from 7.5 to 11 and the optionally pre-treated peroxide is subsequently added.
  • Final pH adjustment of the oxidising composition may be required to restore alkalinity.
  • the pH of the final oxidising composition is within 1 pH unit, preferably within 0.5 pH units of the pH of the pre-mix during the pre-treatment step.
  • Isotropic heavy duty laundry detergent liquids were prepared containing the components listed in Table 1, in the weight percentages of total composition listed in Table 1. T_ 19 I
  • the composition was prepared by firstly making up several pre-solutions. 1. Sodium Hydroxide
  • a 50% by weight solution of sodium hydroxide was prepared with deionised ice and water. After cooling,
  • Dequest 2066 (methylene phosphonate sequestering agent) was added at a concentration 0.5% by weight of the overall solution.
  • a solution of Dequest 2066 (sequestering agent) was prepared by an 8-fold dilution of the 25% stock solution with deionised water. 3. Dimethyl ⁇ l ⁇ oxime solution (DMG.
  • a 0.218M solution of DMG sodium salt sequestering agent was prepared in deionised water.
  • a 30% by weight solution of paraffin sulphonate was prepared from Hostapur SAS 93 using deionised water.
  • the required amount of paraffin sulphonate solution to provide the required weight of paraffin sulphonate was added to a beaker.
  • a pre-calculated amount of deionised water is added.
  • the solution was warmed to 40°C and Synperonic A7 solution was then added slowly with stirring.
  • the Dequest 2066 solution was then added and after mixing the DMG solution was added.
  • the pH was adjusted to 9.5 and the pre-mix solution left to stand at ambient for the required time delay.
  • the optionally pretreated hydrogen peroxide was then added dropwise over a period of 5-10 minutes. The pH was then readjusted to 9.5 using pretreated hydroxide solution.
  • the initial AvOx in the oxidising composition formulation was then measured using a permanganate titration.
  • the sample was placed on storage in a climate controlled chamber at 37°C, 80% relative humidity.
  • the stability data is given below. %% A ; VOX remaining
  • Dequest 2066 was added to water and the pH adjusted to 9.5 by addition of sodium hydroxide. The solution was allowed to stand for 24 hours at ambient before adding 10% peroxide solution to give a 0.5% peroxide concentration (Solution E) . The pH was adjusted back to 9.5 with further sodium hydroxide. A second solution was then prepared in an identical manner except that the 24 hour contact time was omitted (Solution F) . The Loss in Available Oxygen over time was measured in the same way as for Example l. The % AVOX remaining for Solution E was still 66% after 6 weeks compared with only 46% after 5 weeks for Solution F, thus clearly demonstrating the benefit of an extended contact time before addition of the peroxide. The loss of more than 50% AVOX in only 5 weeks at ambient indicates that a much greater loss would occur over 12 weeks at 37°c and 80% relative humidity.
  • a laundry detergent liquid was prepared, the final formulation comprising the following components in the weight percentages listed: Marlon AS 3 (linearalkylbenzene sulphonate) 7%
  • ambient storage refers to storage under conditions of ambient temperature, pressure and relative humidity. Accelerated storage signifies that the samples were stored at 37°C and 80% relative humidity.

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Abstract

The stability of aqueous peroxide containing liquid concentrates are improved by pretreating every component to be contacted with peroxide in aqueous solution with a sequestrant capable of sequestering transition metal ions. The sequestering step requires the contact of the sequestrant with the component for a period of time of at least 45 minutes. Mixtures of sequestrants can be used which are capable together of sequestering a range of transition metal ions which would otherwise catalyse decomposition of the peroxide. The invention is of particular value for pretreating pH adjusting components such as alkali.

Description

BLEACHING COMPOSITIONS
This invention relates to aqueous alkaline oxidising compositions which contain peroxide. The invention particularly relates to concentrated bleaching compositions which contain peroxide and which can be diluted by the user to obtain a washing composition.
Acidic compositions are known, but it is desirable to produce alkaline peroxide-containing aqueous liquids because the activity of the peroxide is enhanced.
However, it is well known that alkaline conditions present particular difficulties for liquid compositions containing peroxide because the peroxide tends to decompose rapidly under alkaline conditions. Therefore, there are considerable difficulties in trying to produce such a composition which is sufficiently storage stable. One way of overcoming this problem is to prepare an alkaline peroxide-containing composition and use it immediately, for example as described in GB-A-2030609, so that storage stability is not required.
There have however been several attempts to prepare stabilised liquid compositions which are alkaline and which contain peroxide, for example in US-A-5180514, GB-A- 2072643, EP-A-076166 and EP-A-37184 several different methods are disclosed, all of which require the use of an alcohol.
In US-A-5180514 aqueous peroxide bleaching compositions are described. It is described that trace metal cations in amounts of 0.5ppm or greater result in deterioration of peroxide compositions. Stabilisation is achieved in this reference by incorporating a heavy metal sequestering agent or chelating agent and an aromatic amine free radical scavenging agent. The sequestering agents chosen are known to sequester Felll and Cull ions. The pH of the bleach compositions is said to be in the range 1 to 8, more preferably 1 to 6 and most preferably 2 to 4. In the examples, the stabilised bleach formulations prepared are all acidic. There is no detailed description of the preparation of the bleaching compositions.
In GB-A-2072643 stability of the compositions is obtained using a combination of non-aqueous solvent (ethanol) , amino compounds substituted by acetate or methylene phosphonates and hydroxy alkyl diphosphonates, particularly with a polyhydroxy carboxylate, preferably gluconate or an amino acetate. The particular difficulty of preventing the hydrogen peroxide from decomposing on storage in an alkaline composition is discussed. The products are prepared by introducing each of the components of the composition sequentially or concurrently into a mixing tank and agitating. In EP-A-0037184 stabilisation is achieved using a combination of an alcohol and/or a polyhydroxy carboxylate, preferably gluconate in conjunction with a phosphonate, especially ethylene diamine methylene phosphonate. The compositions are prepared by forming a mixture of surfactant, then adding all of the other ingredients, with the hydrogen peroxide being added last.
In GB-A-2072643 it is specifically stated that deionised water is used to minimise peroxide decomposition.
In EP-A-0076166, stabilisation is achieved using a combination of isopropanol and an aminomethylene phosphonate or hydroxyalkyl diphosphonate, optionally with a polyhydroxy aliphatic carboxylate.
In O91/09807, stabilisation is achieved by introducing into a concentrated aqueous acidic solution of hydrogen peroxide, amino poly(alkylene phosphonic acid) or a salt thereof, storing the mixture until the aminopoly(alkylene phosphonic acid or salt has been converted to a derivative in the acidic solution and then diluting the concentrate with alkali to form a mildly alkaline solution.
In W093/13012 an aqueous alkaline hydrogen peroxide composition is buffered and stabilised using cyclohexane- 1,2-diaminotetramethylenephosphonic acid. In the preparation of the composition exemplified, the phosphonic acid stabiliser was introduced into a buffered solution and shortly after an aqueous solution containing tetradecyldimethylamine oxide, a perfume and water and then aqueous hydrogen peroxide solution were added to the stabiliser-containing mixture and finally, sodium hydroxide was added until the composition reached a pH of 8.5.
Thus, the problem of lack of stability of peroxide in aqueous alkaline compositions is well recognised and many methods are described for trying to stabilise such compositions. As will be seen from above, these include the incorporation of non-aqueous solvents, sequestering agents, free-radical scavengers and use of deionised water. In US-A-3951840, a solid peroxide bleaching composition is prepared incorporating, for stability a chelating agent capable of forming a water-soluble or poorly water-soluble compound. The chelating agent is either added to the final composition or it is present during the reaction of sodium carbonate, sodium pyrophosphate or sodium borate with hydrogen peroxide to form the inorganic bleaching agent. It was reported that the presence of the sequestering agent during that reaction produced more stable peroxide components. However, there is still a need for an improved one- pack peroxide-containing aqueous alkaline oxidising composition which will maintain sufficient stability to have a useful shelf-life.
Whilst it is recognised that the prior art may improve the stability of hydrogen peroxide-containing compositions under alkaline conditions, the gain in stability resulting from the prior art disclosures is short term only and often places considerable limitations on the detergent formulations which can be used so that the overall detergent properties of such compositions may not be satisfactory. The present invention provides for long term storage stability and significantly improves the reproducibility of its attainment. The invention also overcomes previous limitations in possible formulations and general detergent performance properties by enabling the use of components previously found to degrade the peroxide to unacceptably low levels.
The inventors of this invention have found that a surprising advantage can be achieved by incorporating a sequestering agent into such a composition using a carefully controlled preparation process for the composition.
In accordance with the present invention, a method is provided for preparing a peroxide-containing concentrated aqueous alkaline oxidising composition in which components comprising an aqueous liquor and other optional components are mixed with peroxide, characterised in that prior to mixing with the peroxide, every component of the mixture which potentially includes transition metal ions which will contact the peroxide in the composition is pre-treated in a pre- treatment step by contact in an aqueous liquid with a sequestering agent for at least 45 minutes.
The present invention also includes a method for preparing a peroxide-containing concentrated aqueous alkaline oxidising composition in which components comprising an aqueous liquor and other optional components are mixed with peroxide, characterised in that prior to mixing with the peroxide, every component of the mixture having a transition metal ion content such that in the oxidising composition it will produce an AvOx (available oxygen from peroxide) loss of 50% or more, or even 25% or more, or most preferably every component which will produce an AvOx loss of 5% or more from the oxidising composition over 12 weeks at 37βC and 80% relative humidity (RH) is pre-treated in a pre-treatment step by contact in an aqueous liquid with a sequestering agent for at least 45 minutes. The present invention has the additional advantage that it enables preparation of stable compositions which do not require incorporation of an additional, non-aqueous solvent such as an alcohol. Alcohols are disadvantageous because they reduce the flash-point of the compositions. This is a particular problem due to the strongly oxidising (and therefore potentially explosive) nature of peroxides. In addition, alcohols are disadvantageous because their use introduces additional processing costs. The present invention may also be of value in preparing non-aqueous compositions and/or in which the pre- treat ent step is carried out in a non-aqueous solvent.
The oxidising composition is generally a bleaching composition. The peroxide will be at least partially soluble in the composition and may be one or mixtures of more than one of hydrogen peroxide, organic peroxides and inorganic persalts which liberate hydrogen peroxide in water. Suitable examples of inorganic persalts include alkali metal salts of perborate, persulfate, perphosphate or percarbonate. This invention has been found to be particularly advantageous because it enables the use of hydrogen peroxide which, being a liquid under normal conditions of use is a particularly easily decomposed form of peroxide and is therefore particularly problematic. Hydrogen peroxide is particularly preferred as it has a higher rate of reaction because it does not require dissolution time. Pre-formed peracids may also be used as the peroxide component. Examples are perbenzoic or peracetic acid. A pre-formed peracid may be used in addition to a peroxide salt or hydrogen peroxide and if so, the peracid may be encapsulated.
The concentration of peroxide in the final composition will generally be such as to provide a concentration equivalent to hydrogen peroxide (100%) in an amount of at least 0.5% preferably at least 1%, most preferably at least 3%. Generally it will be no greater than 15%, preferably below 10% and most preferably below 7% by weight of the oxidising composition. The aqueous liquor and alkali for preparing the aqueous alkaline composition may be provided in the form of an aqueous solution of alkali or may be introduced separately as water and alkali components. Alkalinity in the compositions of the present invention is generally provided by the addition of any conventional alkali. In particular hydroxides, especially alkali metal hydroxides are used. The amount of alkali used is such that the pH of the final composition will be at least 7, generally being no greater than 13.5. Preferably, the pH of the final composition will be at least 8, or even at least 8.5. Preferably the pH of the final composition will be up to around pH 11, most preferably from pH 9 to 10.5. The method according to the present invention may be used to prepare an oxidising composition for any application.
The other, optional components for preparing the oxidising composition may comprise any of the typical additives used in oxidising, especially detergent compositions, for example surfactants, builders, bleach activators, electrolytes, hydrotropes, decouplingpolymers, optical brighteners, dyes, fragrances, anti-redeposition agents, dye-transfer inhibitors, enzymes and/or free radical scavengers and/or additional peroxide stabilisers.
Buffers such as carbonate compounds may also be included.
Oxidatively, perhydrolytically or hydrolytically unstable materials if incorporated into the oxidising composition are preferably suitably protected, for example by releasable encapsulation, prior to incorporation.
Generally the oxidising compositions of the present invention will be bleaching compositions, especially cleaning compositions, preferably they will contain at least surfactant. The surfactant may be anionic, nonionic or cationic or mixtures of such surfactants. The incorporation of anionic surfactants has been found to cause the most difficulties with respect to rate of decomposition of peroxide in an alkaline peroxide composition. In the present invention, one of the particular advantages which have been found is that anionic surfactants can be incorporated into the oxidising compositions while surprisingly, maintaining good stability of the peroxide composition.
Suitable anionic surfactants include any surfactant useful in a detergent for example salts of sulphonic or monoesterified sulphuric acids such as alkyl benzene sulphonate, alkyl sulphates, alkyl ether sulphates, olefin sulphonates, alkyl phenol sulphates, alkyl phenol ether sulphates, alkyl ethanolamine sulphate, alkyl ethanolamine ether sulphates, alpha sulpho fatty acids or esters, each having at least one alkyl or alkenyl group from 8 to 22, more usually 10 to 20 aliphatic carbon atom and the alkyl or alkenyl groups preferably being straight chain primary groups. Other suitable anionic surfactants include fatty alkyl sulphosuccinates, fatty alkyl ether sulphosuccinates, acyl sarcosinates, acyl taurides, and paraffin sulphonates. The preferred anionic surfactants are salts of alkali metals or alkaline earth metals, preferably sodium. Other salts include ammonium, monoethanolamine, diethanolamine, triethanolamine and alkyl amines having up to 7 aliphatic carbon atoms. Particularly preferred examples of anionic surfactants for use in the present invention include sodium dodecylbenzene sulphonate, potassium hexadecylbenzene sulphonate, sodiumdodecyldimethylbenzy1 sulphonate, sodium lauryl sulphate, ammonium lauryl onoethoxysulphate, monoethanolamine cetyl ethoxylate sulphate and paraffin sulphonates.
Suitable nonionic surfactants include for example alkanolamides (such as CIO to C20) and/or ethoxylated alcohols, carboxylie acids, amines, alcohol amides, alcohol phenol, glyceryl esters, sorbitan esters, phosphate esters etc. Suitable cationic surfactants include for example quaternary amines, imidizolines and quaternised imidizolines. Amphoteric surfactants may also be used.
All of the percentages given below are by weight as a percentage of the total weight of the oxidising composition. Surfactants are generally incorporated into the composition of the present invention in amounts of at least 1%, preferably at least 3%, or even at least 5%, more preferably at least 10% by weight of the finished oxidising composition. Preferably the amount of surfactant in the composition will be up to 60% by weight and most preferably up to 50% by weight.
Typically the formulation will be a heavy-duty laundry detergent containing a high proportion of active components, including at least 10% by weight surfactant, preferably at least 15% or even 25%. The formulation may therefore be for example either isotropic or structured. Structured compositions may include decoupling polymers, optionally with electrolyte and isotropic compositions may include hydrotrope optionally with electrolyte. The optional, other components of the composition are therefore selected according to the desired formulation.
Any builder which is conventional for use in detergent compositions may be used in the compositions,of the present invention such as phosphates, carbonates, zeolites, acetates, citrates, etaphosphate, pyrophosphate, phosphonate, EOTA and/or polycarboxylates or silicates. The builder may also contribute to the electrolyte concentration in the composition. Builders such as silicates may also contribute to the alkalinity of the compositions of the present invention. A preferred builder is an alkali metal citrate salt.
Certain builders may interfere with the sequestration of transition metal ions by the sequestering agents thereby decreasing the stability of the formulations, for example zeolites, phosphates, EDTA, polycarboxylates and/or phosphonates. If, for performance reasons, these are preferred components they should be included in a form such as to prevent this interference but still in a form which can be released into the wash bath, preferably by encapsulation. Builders may be incorporated in the composition in amounts of from 0 to 40% by weight of the total composition, preferably at least 2%, most preferably at least 5%, generally no greater than 30% and preferably no greater than 25% by weight of the final composition. Bleach activators may be used in the composition. Any of the N-acyl or o-acyl compounds which are conventionally used as bleach activators is suitable. Particularly preferred compounds are for example as described in EP-A- 0331300 and EP-A-0332294. Examples of other well known and useful bleach activators include for example TAEO. Generally the activator if any will be incorporated in amounts of from 0.1% to 10%, preferably in amounts greater than 0.5% or even 1%. Generally the amount of activator will be no greater than 5%, or even 2.5% by weight of the final composition.
Bleaching catalysts or enzymatic activators may also be used in the compositions of the present invention. These are generally required at lower concentrations than the N-acyl or O-acyl activators, for example below 0.1%. One or more of the optional components may be unstable under aqueous alkaline conditions or react with peroxide under aqueous alkaline conditions. This may be a particular problem for builders and/or activators and in some cases it may be advantageous to encapsulate one or more of the optional components for inclusion in the aqueous composition. A suitable encapsulation technique for activators and suitable activators are described in for example British patent application number 9323634.7.
The electrolytes which may be used are any electrolytes commonly used in this type of composition either singly or mixtures of more than one electrolyte, and in amounts necessary to provide the desired degree of physical stability or viscosity to the composition. Likewise, the hydrotropes and decoupling polymers which are used are conventional and in the desired amounts for physical stability. Optionally, thickening agents may also be incorporated in the composition as an additional optional component.
Any of the above components may be in the solid form, suspended in the aqueous liquid. However, preferably all of the components are in the form of liquids, most preferably as aqueous solutions. As explained above, some components may react with peroxide or be unstable in alkaline conditions. These are preferably incorporated as encapsulated solid materials.
Every component of the mixture potentially including transition metal ions which will contact the peroxide in the composition is pre-treated in the pre-treatment step.
Any solid components for suspension in the compositions may include transition metal ion impurities on their surface and if so, pre-treatment will be necessary to prevent decomposition of the peroxide in the composition.
For particulate solids, where on storage only the exterior of the particle is able to contact the peroxide in the composition, it is only necessary to pre-treat to such an extent that any transition metal ions from the exterior of the particle will be sequestered. Any transition metal ions inside the particle which will not contact the peroxide on storage in the composition do not require sequestration and are not generally sequestered in the pre- treatment step. Therefore, generally every liquid component in the mixture having a transition metal ion content of at least 0.5ppm, preferably every component having a transition metal content of at least 0.05ppm and most preferably every component having a transition metal ion content of at least O.Olppm is pre-treated in the pre-treatment step. For any particulate solids, those having transition metals in these amounts on their outer surfaces or which will when in the aqueous liquid release transition metal ions in these quantities are generally pre-treated.
More particularly, components which contain 0.5ppm, or above preferably all those which contain 0.05ppm and most preferably all those components which contain O.Olppm or above, or even amounts above O.OOlppm, transition metal ion impurities which are active in peroxygen decomposition under alkaline conditions, are pre-treated in the pre- treatment step. Generally, each component in the composition will be treated if the transition metal ion impurities in that component are such as to produce an AvOx (available oxygen from peroxide) loss of 50% or more from the oxidising composition over 12 weeks at 37βC and 80% RH. Thus, in order to assess whether a component in the composition does contain transition metal ion impurities such as to produce an AvOx loss of 50% or more from the oxidising composition over 12 weeks at 37°C and 80% relative humidity, an oxidising composition is prepared containing all of the components except that to be tested, all of the components having been either pre-sequestered or purified so that they do not contain transition metal ion to degrade the hydrogen peroxide. Finally, the component for testing is added to the oxidising composition, without having undergone a pre-treatment step. The AvOx in the composition is measured immediately after addition of the component to be tested to find the initial AvOx. From the time of addition of the component to be tested, the AvOx loss of the composition is monitored over 12 weeks, the composition being maintained at conditions of 37°C and 80% relative humidity.
A control composition is also monitored for AvOx loss. The control composition is identical to that being monitored (which includes the component to be tested) , with the exception that the control composition does not contain the component to be tested. Thus, the AvOx loss of the control composition over 12 weeks at 37°C and 80% RH is subtracted from the AvOx loss over 12 weeks under the same conditions for the composition including the component being tested to arrive at a result indicating the AvOx loss from the oxidising composition due to the component being tested.
If the resulting AvOx loss due to the component being tested over the 12 week period is 50% or more of the initial AvOx, then for preparation of effective oxidising compositions, that component should undergo the pre- treatment step.
Preferably, every component which produces an AvOx loss of 30% or more, 25% or more or even 10% or more over 12 weeks at 37°C and 80% RH in accordance with the test described above, will be pre-treated. The final oxidising composition prepared will be such that transition metal ion impurities are pretreated to ensure the AvOx loss over 12 weeks at 37°C will be no greater than 50%, preferably no greater than 40% and most preferably no greater than 25% of the initial total AvOx of the composition, measured after preparation of the composition and prior to storage. AvOx loss is measured by permanganate titration to detect remaining available oxygen and then by subtraction from the initial available oxygen.
In the pre-treatment step, each individual component for forming the mixture may be treated individually. Alternatively, groups of mixtures of different components or, preferably, all of the components of the mixture are mixed together to form a pre-mix and the pre-mix is pre- treated prior to incorporation of the peroxide. Preferably in the pre-treatment step contact with the sequestering agent will be for at least 1 hour or even at least 2 hours. Contact may be for at least 6 hours, preferably at least 12 hours and most preferably at least 24 hours. It has been found that satisfactory results can be achieved by allowing contact with the sequestering agent for as little as 45 minutes. However, preferably the contacting step is for a longer period in order to attain good long term stability and reproducibility.
Contact is by the addition of the sequestering agent or mixture of sequestering agents to the component or mixtures of components in an aqueous environment and the component and sequestering agent mixture is allowed to stand for the contact time. Optionally, during the contact time, the aqueous environment may be agitated, for example by stirring or other agitation means. It has been found that in some cases, agitation reduces the time required for effective sequestration of the transition metal ions.
For optional components which are crystalline and which can be provided in solid form either for dissolution or suspension in the aqueous composition, it has been found that it is particularly advantageous if, for the pre- treatment step, the solid is dissolved in a solution, preferably aqueous, containing the sequestering agent(s) or to which the sequestering agent(s) is added, the solution is then left for the contact time and subsequently, the crystalline solid is recrystallised out of solution by any conventional means. The crystalline solid may then be redissolved or added directly to the aqueous composition.
The time of contact between the components for preparing the composition and the sequestering agent in the pre-treatment step may vary depending upon other factors. For example, an increase in temperature may reduce the time needed for pre-treatment. However, preferably the temperature conditions in the pre-treatment step will be the same as or as close as possible to those of the storage of the final oxidising composition, (generally ambient 15- 25°C) , to ensure maximum stabilisation of the composition. Preferably the temperature for the pretreatment step will be between 10 and 50°C, preferably being no more than 10°C preferably no more than 5βC higher or lower than the temperature at which the final composition will be stored.
Not wishing to be bound by theory, it is postulated that in the pre-treatment step, transition metal ion impurities from each of the components which will form the final oxidising composition form complexes with the sequestering agents. It is postulated that upon initial contact of the transition metal ions with sequestering agent, the kinetically preferred complexes are formed. After a time delay of at least 45 minutes, preferably at least 1 or even two hours, sufficient time is allowed to enable formation of the thermodynamically most stable complex. The time delay also allows those metals which undergo slow ligand exchange reactions, time to react with the sequestering agent or mixture of sequestering agents. From the significant benefits which have been achieved due to the pre-treatment step described above it is clear that any transition metal ion impurities which are active in peroxide decomposition have a significantly reduced effect on the decomposition of hydrogen peroxide and surprisingly enhanced stability is obtained as a result of this effective sequestration.
Preferably the peroxide itself is also pre-treated by addition of sequestering agent(s) to a peroxide solution as described above. Where the peroxide is provided in the form of a salt, recrystallisation of the salt can be performed as described above. Preferably however the peroxide is hydrogen peroxide and the pre-treatment step is carried out by contact of sequestering agent with hydrogen peroxide solution.
Where possible, it is particularly preferred that the aqueous liquid for the pre-treatment of the components with sequestering agent is alkaline. A pretreated alkaline solution used to adjust alkalinity will inevitably have a higher pH than the final oxidising composition. However for other optional components to be treated, the pH of the aqueous liquid within which the contact with the sequestering agent occurs has a pH within one pH unit of the pH of the final oxidising composition, most preferably within 0.5 pH units of the final oxidising composition. This is particularly preferred for pre-treatment of surfactant and/or builder component.
The use of alkaline pH and pH which is close to the pH of the final oxidising composition is preferred because it enables the production of the thermodynamically most stable complexes of the transition metal ions under the conditions which the transition metal ions will encounter in the final oxidising composition. This ensures that the thermodynamically most stable complexes will form prior to incorporation in the composition, thereby leading to the most stable final composition.
The peroxide may be added to any of the components or pre-mixtures of components for incorporation into the final composition. However, it must not be added to components which require pre-treatment and which have not yet been pre-treated. Where the components require pre-treatment, the peroxide should only be contacted with such components after they have undergone the pre-treatment step.
Most preferably, the peroxide is added after all of the other components of the mixture have been added. Where the peroxide composition is acidic, final pH adjustment of the oxidising composition may be required to restore alkalinity. This is generally by the addition of further alkali solution, pre-treated where necessary. The sequestering agent sequesters the transition metal ions so that they are no longer catalytic in peroxygen decomposition i.e.form complexes with the transition metal ions that are stable with respect to peroxygen decomposition. Suitable sequestering agents can be selected by testing the stabilising effect of a particular sequestering agent on transition metal ions in a hydrogen peroxide solution. Preferably the sequestering agent comprises one or more chosen from those which form a stable complex with cobalt ions under alkaline conditions, particularly preferred examples include dimethylglyoxi e (DMG) or dipyridylamine (DPA) . It is particularly preferred to incorporate into the final composition at least one of those sequestering agents mentioned above and in addition, at least one sequestering agent which forms a stable complex with copper and/or iron and/or manganese ions under alkaline conditions. Particularly preferred examples include sequestering agents which are stable under alkaline conditions and in particular, suitable compounds are aminopoly(alkylene phosphonic acid) or salts, such as 1,2-cyclo-hexane diaminotetra(methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) and ethylene diamine tetra (methylene phosphonic acid) or salts thereof. Particularly preferred classes of sequestering agents are Dequest (trademark) , sequestering agents supplied by Monsanto and Briquest (trademark) sequestering agents supplied by Albright and Wilson.
The amount of sequestering agent used depends to some extent on the amount of transition metal impurities in the component of the composition. Preferably in the pre- treatment step, the sequestering agent will be present in amounts from at least 0.01% by weight of the composition for pre-treatment. Generally the total amount of sequestering agent will be at least 0.02 or even at least 0.03% by weight. The amount of sequestering agent may be up to 1% by weight, or even higher. This should be sufficient sequestering agent for complexing any transition metal impurities in the composition although more may be added if a high proportion of transition metal ion impurities is present as indicated by loss of AvOx, as explained above. Addition of excess sequestering agent can lead to loss of stability.
Preferably the composition will contain at least 0.005% of the sequestering agent which forms a stable complex with cobalt ions under alkaline conditions and at least 0.01% by a weight of the total composition of at least one sequestering agent which forms a stable complex with iron, copper and/or manganese, preferably each of these ions under alkaline conditions.
It has been found that the proportion of transition metal ion impurities is particularly high in anionic surfactants and in builders. Therefore, in the separate pre-treatment of surfactant and/or builder, or in a pre-mix which includes for example at least 10% by weight surfactant and/or builder, the concentration of sequestering agent used in the pre-treatment step may be increased and will generally be at least 0.04% by weight of the total composition in the pre-treatment step.
Where components to be added to the mixture are known to be substantially free of transition metal ion impurities, for example in amounts below 0.5 ppm or even 0.05 ppm, most preferably which contain such transition metal impurities in amounts below O.Olppm, no pre-treatment with sequestering agent may be necessary for example, where deionised water or pre-purified components are used.
In a particularly preferred embodiment of the invention all of the components of the oxidising composition are mixed to form a pre-mix. The pre-mix then undergoes a pre-treatment step by the addition of sequestering agent(s) in an amount of at least 0.04% by weight and at a pH of from 7.5 to 11 and the optionally pre-treated peroxide is subsequently added. Final pH adjustment of the oxidising composition may be required to restore alkalinity. Preferably, the pH of the final oxidising composition is within 1 pH unit, preferably within 0.5 pH units of the pH of the pre-mix during the pre-treatment step.
The following examples illustrate the invention. Example I
Isotropic heavy duty laundry detergent liquids were prepared containing the components listed in Table 1, in the weight percentages of total composition listed in Table 1. T_ 19 I
Component B
Paraffin Sulphonate* 15 15 15 15
Alcohol Ethoxylate 3.75 3.75 3.75 3.75
Phosphonate0 - 0.025 0.025 0.025
Dimethylglyoxime - 0.02 0.02 0.02
Sodium hydroxide qv qv qv qv
Hydrogen peroxide 5β 5 5 5
Deionised water to 100% to > 100% to 100% to 100%
a Hostapur SAS 93, ex Hoechst b Synperonic A7, ex ICI c Dequest 2066, ex Monsanto d Added as 50% w/w solution containing 0.5% Dequest 2066 e No Dequest 2066 in the peroxide solution
The composition was prepared by firstly making up several pre-solutions. 1. Sodium Hydroxide
A 50% by weight solution of sodium hydroxide was prepared with deionised ice and water. After cooling,
Dequest 2066 (methylene phosphonate sequestering agent) was added at a concentration 0.5% by weight of the overall solution.
2. Dequest 2066 solution
A solution of Dequest 2066 (sequestering agent) was prepared by an 8-fold dilution of the 25% stock solution with deionised water. 3. Dimethylσlγoxime solution (DMG.
A 0.218M solution of DMG sodium salt sequestering agent was prepared in deionised water.
4. Paraffin Sulphonate solution
A 30% by weight solution of paraffin sulphonate was prepared from Hostapur SAS 93 using deionised water.
5. Hydrogen Peroxide For each 250ml oxidising composition, lml Dequest 2066 solution described above was added to 24.8g of hydrogen peroxide (60% w/v) and stirred for 15 minutes and left to stand. The solution was added to the pre-mix of components for the composition at least one hour after the addition of Dequest 2066. For sample A, there was no pretreatment using Dequest 2066. For sample B, Dequest 2066 was added 1 hour prior to incorporation of the hydrogen peroxide into the pre-mix solution, for sample C, the delay was 4 hours and for sample D, 25 hours.
6. Preparation of the oxidising composition
The required amount of paraffin sulphonate solution to provide the required weight of paraffin sulphonate was added to a beaker. A pre-calculated amount of deionised water is added. The solution was warmed to 40°C and Synperonic A7 solution was then added slowly with stirring. The Dequest 2066 solution was then added and after mixing the DMG solution was added. The pH was adjusted to 9.5 and the pre-mix solution left to stand at ambient for the required time delay. The optionally pretreated hydrogen peroxide was then added dropwise over a period of 5-10 minutes. The pH was then readjusted to 9.5 using pretreated hydroxide solution.
For each of Samples A and B there was no time delay, the hydrogen peroxide being added as soon as the pre-mix solution was prepared. For Sample C, the pretreatment step was 3 hours and for Sample D, 24 hours.
The initial AvOx in the oxidising composition formulation was then measured using a permanganate titration. The sample was placed on storage in a climate controlled chamber at 37°C, 80% relative humidity. The stability data is given below. %% A ; VOX remaining
Composition 1 week 6 weeksi 12 weeks
A 0 B 95. 2 73.2 39.3
C 96.8 84.7 68.5
D 97 .2 85.7 68.6
The results shown above, demonstrate that a pre- treatment step for the components in the composition, prior to addition of peroxide to the composition, results in a significant benefit in terms of peroxide stability on storage, as shown by the % AvOx remaining over time. A comparison of for example, samples B and C shows that a 3 hour pre-treatment step results in an improvement in AvOx after 12 weeks of 29.2 percentage points. Example 2
Dequest 2066 was added to water and the pH adjusted to 9.5 by addition of sodium hydroxide. The solution was allowed to stand for 24 hours at ambient before adding 10% peroxide solution to give a 0.5% peroxide concentration (Solution E) . The pH was adjusted back to 9.5 with further sodium hydroxide. A second solution was then prepared in an identical manner except that the 24 hour contact time was omitted (Solution F) . The Loss in Available Oxygen over time was measured in the same way as for Example l. The % AVOX remaining for Solution E was still 66% after 6 weeks compared with only 46% after 5 weeks for Solution F, thus clearly demonstrating the benefit of an extended contact time before addition of the peroxide. The loss of more than 50% AVOX in only 5 weeks at ambient indicates that a much greater loss would occur over 12 weeks at 37°c and 80% relative humidity.
This example shows the effect of the sequestration time for an embodiment using a single sequestrant. Example 3
A laundry detergent liquid was prepared, the final formulation comprising the following components in the weight percentages listed: Marlon AS 3 (linearalkylbenzene sulphonate) 7%
Synperonic A7 (an alcohol ethoxylated with 7 moles ethoxy groups) 4%
Sodium Citrate 5%
Dipyridyl amine 0.03% Dequest 2066 (DTPMP sodium salt) 0.2%
Sodium hydroxide (50%w/w) 2%
Hydrogen peroxide 5%
Deionised water To 100%
In order to prepare the formulation, firstly the Marlon AS 3, Synperonic A7 and sodium citrate were mixed with deionised water at 40-50βC to ensure rapid dissolution/dispersion to form an aqueous pre-mixed solution. The dipyridyl amine and Dequest 2066 was then added to the aqueous pre-mix, and the mixture allowed to stand for 24 hours in a pre-sequestration step.
Subsequently, hydrogen peroxide was added to the pre- sequestered pre-mix. 50% w/w pre-sequestered sodium hydroxide was then added to bring the pH of the product solution to 9.5. The pre-sequestered sodium hydroxide was prepared in advance by the addition of 0.5% D2066 to a 50% w/w solution of NaOH. This had been prepared as a stock solution and kept for several weeks. Samples were then analysed for AvOx (available oxygen) stability over a period of 26 weeks. The result are given in Table 1 which lists percentage AvOx loss (1 - (measured AvOx/initial
AvOx)) x 100, AvOx being measured by permanganate titration. In Table 1, ambient storage refers to storage under conditions of ambient temperature, pressure and relative humidity. Accelerated storage signifies that the samples were stored at 37°C and 80% relative humidity.

Claims

1. A method for preparing a concentrated liquid peroxide oxidising composition in which components comprising a liquid vehicle and other, optional components are mixed with peroxide characterised in that, prior to being contacted with the peroxide, every component of the mixture potentially including transition metal ions is pre-treated in a pre-treatment step by contact in an aqueous liquid with a sequestering agent for at least 45 minutes.
2. A method according to claim 1 in which every component of the mixture having a transition metal ion content of at least 0.05ppm, preferably every component having a transition metal content of at least O.Olppm is pre¬ treated.
3. A method according to claim 1 in which every component of the mixture which will produce an AvOx loss of 30% or more, most preferably every component which will produce an AvOx loss of 10% or even 5% or more from the oxidising composition over 12 weeks at 37°C and 80% relative humidity, is pretreated.
4. A method according to any of claims 1 to 3 in which the pretreatment involves contact with sequestrant for at least one hour, preferably at least two hours, more preferably more than 4 hours, most preferably more than 12 hours.
5. A method according to any preceding claim in which all the components of the mixture other than the peroxide is mixed together to form a pre-mix and the pre-mix is treated in the pretreatment step.
6. A method according to any of claims 1 to 4 in which an intermediate composition is formed containing peroxide and all but one of the remaining components of the product and the one remaining component is subjected to the pretreatment step and is then added to the intermediate composition.
7. A method according to any preceding claim in which the liquid vehicle is aqueous.
8. A method according to claim 7 in which the concentrated liquid is alkaline.
9. A method according to any preceding claim in which the other, optional components include surfactant.
10. A method according to any preceding claim in which the optional component comprises a pH modifying material, preferably an alkali.
11. A method according to any preceding claim in which the peroxide comprises hydrogen peroxide, preferably also having been pre-treated in a pretreatment step.
12. A method according to any preceding claim in which the component which is pretreated comprises transition metal ion impurities in an amount of at least O.Olppm, and in which the sequestering agent is capable of sequestering transition metal ions.
13. A method according to claim 12 in which the sequestering agent comprises one or more chosen from sequestering agents which form a stable complex with cobalt ions, under alkaline conditions.
14. A method according to claim 13 in which the sequestering agent comprises dimethylglyoxi e (DMG) or dipyridylamine (DPA) .
15. A method according to claim 14 in which the sequestering agent comprises one or more sequestering agents which form a stable complex with iron, copper and/or manganese under alkaline conditions, preferably a non- cyclic amino poly(alkylenephosphonic acid) or salt, most preferably an amino(methylene phosphonic acid) or salt thereof.
16. A method according to any preceding claim in which the concentration of sequestering agent in the aqueous liquid for the pre-treatment step is at least 0.005, preferably at least 0.01% by weight, preferably being no greater than 5% most preferably no greater than 1% by weight of the component being pre-treated.
17. A method according to any preceding claim in which the aqueous liquid for the pre-treatment of the optional components is alkaline, preferably having a pH within 1 pH unit of the pH of the final concentrated oxidising composition, most preferably within 0.5 pH units of the pH of the final concentrate bleaching composition.
18. A method according to any preceding claim in which after incorporation of the peroxide the composition comprises from 10 to 50% by weight surfactant and from 3 to 25% builder.
PCT/GB1995/001535 1994-07-01 1995-06-30 Bleaching compositions WO1996001309A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU28011/95A AU2801195A (en) 1994-07-01 1995-06-30 Bleaching compositions

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9413307.1 1994-07-01
GB9413307A GB9413307D0 (en) 1994-07-01 1994-07-01 Bleaching compositions

Publications (1)

Publication Number Publication Date
WO1996001309A1 true WO1996001309A1 (en) 1996-01-18

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PCT/GB1995/001535 WO1996001309A1 (en) 1994-07-01 1995-06-30 Bleaching compositions

Country Status (3)

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AU (1) AU2801195A (en)
GB (1) GB9413307D0 (en)
WO (1) WO1996001309A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0037184A2 (en) * 1980-04-01 1981-10-07 Interox Chemicals Limited Liquid detergent compositions, their manufacture and their use in washing processes
EP0076166A2 (en) * 1981-09-30 1983-04-06 Interox Chemicals Limited Bleach composition
WO1991009807A2 (en) * 1989-12-23 1991-07-11 Interox Chemicals Limited Stabilisation of hydrogen peroxide solutions

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0037184A2 (en) * 1980-04-01 1981-10-07 Interox Chemicals Limited Liquid detergent compositions, their manufacture and their use in washing processes
EP0076166A2 (en) * 1981-09-30 1983-04-06 Interox Chemicals Limited Bleach composition
WO1991009807A2 (en) * 1989-12-23 1991-07-11 Interox Chemicals Limited Stabilisation of hydrogen peroxide solutions

Also Published As

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GB9413307D0 (en) 1994-08-24
AU2801195A (en) 1996-01-25

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