EP1130083A1 - Cleaning compositions - Google Patents

Cleaning compositions Download PDF

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Publication number
EP1130083A1
EP1130083A1 EP00301726A EP00301726A EP1130083A1 EP 1130083 A1 EP1130083 A1 EP 1130083A1 EP 00301726 A EP00301726 A EP 00301726A EP 00301726 A EP00301726 A EP 00301726A EP 1130083 A1 EP1130083 A1 EP 1130083A1
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EP
European Patent Office
Prior art keywords
hypochlorite
acid
solution
aqueous solution
sodium
Prior art date
Legal status (The legal status 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 status listed.)
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Application number
EP00301726A
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German (de)
French (fr)
Inventor
Nicola Rogers
Katherine Thompson
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Unilever PLC
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Unilever PLC
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Filing date
Publication date
Application filed by Unilever PLC filed Critical Unilever PLC
Priority to EP00301726A priority Critical patent/EP1130083A1/en
Publication of EP1130083A1 publication Critical patent/EP1130083A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
    • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
    • C11D3/02—Inorganic compounds ; Elemental compounds
    • C11D3/04—Water-soluble compounds
    • C11D3/042—Acids
    • C—CHEMISTRY; METALLURGY
    • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
    • C11D17/00—Detergent materials or soaps characterised by their shape or physical properties
    • C11D17/04—Detergent materials or soaps characterised by their shape or physical properties combined with or containing other objects
    • C11D17/041—Compositions releasably affixed on a substrate or incorporated into a dispensing means
    • C—CHEMISTRY; METALLURGY
    • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
    • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
    • C11D3/16—Organic compounds
    • C11D3/20—Organic compounds containing oxygen
    • C11D3/2075—Carboxylic acids-salts thereof
    • C—CHEMISTRY; METALLURGY
    • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
    • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
    • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
    • C11D3/395—Bleaching agents
    • C11D3/3956—Liquid compositions

Definitions

  • the present invention relates to systems containing a halogen bleach source, for example for use as household cleaning products.
  • hypochlorite bleaches in household hard surface cleaning compositions, for example as kitchen surface cleaners typically containing 0.1-1.5% by weight of sodium hypochlorite at a pH of approximately 11.5-13.0, or at higher levels, e.g. up to 3% by weight of hypochlorite for mould removal.
  • hypochlorite bleaching compositions giving the same high standards of cleaning (and hygiene) performance as these standard sodium hypochlorite household cleaning products but with lower hypochlorite levels to provide better sensory, safety and environmental properties.
  • the present invention solves this problem by reducing the pH of the hypochlorite solution at the point of delivery, by admixture with an acid.
  • WO-A-98/21308 describes the use of a dual-compartment pack to separate alkaline hypochlorite and a chlorine 'de-activating agent' such as sulphamic acid.
  • the mixed formulation has a pH of around 6 and is said to give good bleaching of mould and food/beverage stains on hard and soft surfaces but, as sulphamic acid acts as a chlorine scavenger, without the risk of producing toxic chlorine gas.
  • a hypochlorite to sulphamic acid ratio of 3.6 to 2.5 is specified to ensure adequate bleaching activity.
  • the use of thickening agents in conjunction with these formulations, to provide "cling" to vertical surfaces, is also disclosed.
  • the present invention differs from that disclosed in WO-A-98/21308 in that the usage pH range is greater than 6 and for this reason the formulation need not contain an amine compound as a chlorine 'de-activating agent'.
  • an aqueous solution of "a source of unipositive chlorine ions”, typically sodium hypochlorite, contains a chlorine stabilising agent such as sulphamic acid or a salt thereof, or an organic sulphonate or sulphonamide, and an acidic buffer, typically a mono-, di- or polycarboxylic acid or phosphoric acid.
  • a source of unipositive chlorine ions typically sodium hypochlorite
  • a chlorine stabilising agent such as sulphamic acid or a salt thereof, or an organic sulphonate or sulphonamide
  • an acidic buffer typically a mono-, di- or polycarboxylic acid or phosphoric acid.
  • the pH is buffered to be from around 2 to 6.5.
  • the present invention differs from that disclosed in WO-A-99/32596 in that being in two-pack form, the hypochlorite is stored at a more alkaline pH and therefore, does not require the chlorine stabilising agent.
  • US-A-4 236 891 describes the use of magnesium hypochlorite maintained at a pH in the range 3.5-7.7, by addition of mineral or organic acids, for industrial or domestic bleaching of textiles.
  • CA-A-1 087 955 relates to use of hydroxycarboxylic acid salts in reducing hypochlorite pH to between 5 and 8 for cleaning and disinfecting substrates including human skin and clothing.
  • the present invention now provides a dual container delivery system comprising a first container containing a first aqueous solution comprising a hypochlorite bleach or a source thereof and having a pH of at least 13, a second container containing an aqueous solution comprising an acid and delivery means for delivering the first and second solutions to a surface such that they mix just before or upon impacting the surface, the amount and strength of the acid in the second solution being such that the pH of the resulting mixture is from 8 to 13, preferably from 9 to 12.
  • the pH of the first aqueous solution i.e. that containing the hypochlorite, is at least 13. Furthermore, the pH of the composition resulting from mixing of the two aqueous solutions can also be as high as 13. However, it is to be understood that whatever the pH of the first aqueous solution before mixing, the pH of the resultant mixed solution will always be lower than that of the first aqueous solution, by virtue of the acid from the second aqueous solution.
  • the present invention involves delivery of hypochlorite formulations of 'reduced' alkalinity by mixing an alkaline hypochlorite solution with an acid at the point of delivery.
  • the alkaline hypochlorite and acid solutions are stored separately in the compartments of a dual-compartment pack and mix together during application onto the surface. In this way, the stability problems associated with use of reduced alkalinity hypochlorite are avoided.
  • the higher reactivity of the less alkaline hypochlorite formulation allows a reduction in the level of hypochlorite required to achieve current standards of cleaning and hygiene.
  • Systems according to the invention are applicable for use in a range of products where relatively high concentrations of hypochlorite bleach are currently required to achieve acceptable cleaning and hygiene performance.
  • Specific product types include mould removers, wc and kitchen cleaners.
  • the first and second aqueous solutions need to be kept in different containers so that their components do not react until use. This could be achieved by providing them in respective separate containers. The consumer could then apply each to the surface, either sequentially or simultaneously.
  • the delivery means then allows them to be delivered to the surface so that pH reduction of the hypochlorite solution occurs or is initiated as they are exiting the delivery means and/or in mid-air as they are directed to the surface and/or on the surface itself.
  • they are delivered to be mixed in approximately equal volumes, i.e. typically from 0.5 : 1 v/v to 1 : 0.5 v/v.
  • a particularly preferred delivery means is a trigger spray head.
  • this will preferably have two siphon tubes, respectively leading into each compartment and either a single nozzle with a mixing chamber or two separate nozzles substantially adjacent to each other.
  • a dispensing nozzle or nozzles configured to promote foaming may be used.
  • the hypochlorite or hypochlorite source is preferably present at about from 0.01% to 10% by weight, more preferably from 0.1% to 2%, most preferably from 0.05% to 0.5% by weight of the first aqueous solution.
  • the amount of acid will depend on the alkalinity of the hypochlorite (first aqueous) solution.
  • this will be typically present at about from 10 mole% to 200 mole%, more preferably from 50 mole% to 150 mole% based on the molar concentration of the hypochlorite present.
  • the quantity of acid required to achieve a specific pH will of course depend on the quantity of additional alkali added to the first solution. For n-valent mineral acids, these values will be divided by n. In the case of organic acids, these amounts are more difficult to express as the range of strengths of such acids is quite large. However, for a dicarboxylic acid such as malic, maleic or succinic acid, typical ranges might be from 10 mole% to 300 mole%, more preferably from 50 % to 150 mole%.
  • the hypochlorite or source thereof in the first solution may be a simple hypochlorite salt such as those of the alkali or alkaline earth metals or a compound which produces hypochlorite upon hydrolysis, such as the organic N-chloro compounds. Mixtures of such materials may also be used.
  • the acid in the second solution may be a mineral acid such as hydrochloric, sulphuric, phosphoric or nitric acid.
  • the term "acid” includes acidic salts such as sodium hydrogen sulphate. Alternatively, it may be organic acid such as a mono-, di- or polycarboxylic acid. Forms of any of these which are hydroxylated and/or contain keto and/or ester and/or amide groups may also be used. Saturated and unsaturated forms are included within these definitions.
  • Simple monocarboxylic acids such as formic acid and acetic acid may be used but are less preferred because of their unpleasant odours.
  • a non-exhaustive list of typical suitable organic acids includes propanoic, lactic, glycolic, pyruvic, crotonic, isovaleric, cinnamic, salicylic, carbanic, methylcarbanic, benzoic, glucanic, malic, maleic, sulphonic, methane sulphonic, toluene sulphonic, fumaric, malonic, itaconic, oxalic, tartaric, glutamic, aspartic and succinic acids.
  • citric acid is a generally preferred organic acid.
  • the acid component in the second aqueous solution may contain mixtures of two or more acids. However, whatever acid or acids are used, they preferably should not be of a type which would be oxidised within a few minutes of admixture with the hypochlorite. Again, mixtures of such materials may be used.
  • the weight ratio of the hypochlorite or its precursor to the acid is typically from 0.01 : 1 to 100 : 1.
  • hypochlorite (or source thereof) and acid solutions are stored separately using dual-compartmentalised packaging and react together on mixing during application onto the surface.
  • the resulting mixed formulations give efficient bleaching from the relatively low levels of the hypochlorite.
  • the hypochlorite is present in alkaline solution, in order to minimise decomposition, while the acid is present at a level sufficient that on mixing the final pH of the formulation is optimised for the specific usage scenario. It is important that the mixing process be carefully controlled so that the pH of the final mixed solution is constrained not to fall below a value of 8. Attempts to achieve lower pH values could result in incomplete mixing and localised areas of very low pH with the consequent risk of generating toxic chlorine gas.
  • the mixed composition may also contain surfactants, polymers and other formulation components such as a perfume, or dye. Some or all of these additional components can be stored separately from hypochlorite, i.e. together with the acid, allowing use of formulation ingredients that do not have long term stability in hypochlorite solution and are therefore not used in conventional single compartment hypochlorite bleach formulations.
  • composition according to the invention optionally may comprise detergent actives (surfactants).
  • surfactants may be chosen from a wide range of anionic, nonionic, cationic, amphoteric or zwitterionic surfactants well known in the art.
  • Suitable anionic surfactants are e.g. water-soluble salts, particularly alkali metal, alkaline earth metal and ammonium salts, of organic sulphate esters and sulphonic acids having in the molecular structure a C 8 -C 22 alkyl radical or a C 10 -C 22 alkaryl radical.
  • anionic surfactants are alcohol sulphate salts, especially those obtained from the fatty alcohols derived from the glycerides of tallow or coconut oil; alkyl-benzene sulphonates such as those having a C 9 -C 11 radical.
  • anionic detergents are alcohol sulphate alkyl group attached to the benzene ring; secondary alkanesulphonates; sodium alkyl glyceryl ether sulphates, especially those ethers of the fatty alcohols derived from tallow and coconut oil; sodium fatty acid monoglyceride sulphates, especially those derived from coconut fatty acids; salts of 1-6 EO ethoxylated fatty alcohol sulphates; salts of 1-8 EO ethoxylated alkylphenol sulphates in which the alkyl radicals contain 4-14 C-atoms; the reaction product of fatty acids esterified with isethionic acid and neutralised with sodium hydroxide.
  • the preferred water-soluble synthetic anionic surfactants are the alkyl benzene sulphonates, the olefin sulphonates, the alkyl sulphates, and the higher fatty acid monoglyceride sulphates and fatty acid soaps.
  • a special class of anionic surfactants which may be used in the cleaning compositions according to the invention are hydrotropes which are known in the art specifically for their thickening or liquid structuring capabilities.
  • hydrotropes which are known in the art specifically for their thickening or liquid structuring capabilities.
  • Well known examples of such compounds are the alkali metal salts of toluene-, xylene- and cumene-sulphonic acid.
  • Suitable nonionic surfactants can be broadly described as compounds produced by the condensation of alkylene oxide groups, which are hydrophilic in nature, with an organic hydrophobic compound which may be aliphatic or alkylaromatic in nature.
  • the length of the hydrophilic or polyoxyalkylene radical which is attached to any particular hydrophobic group can be readily adjusted to yield a water-soluble or water dispersible compound having the desired balance between hydrophilic and hydrophobic elements.
  • Particular examples include the condensation product of straight chain or branched chain aliphatic alcohols having 8-22 C-atoms with ethylene oxide, such as coconut oil fatty alcohol/ethylene oxide condensates having from 2 to 15 moles of ethylene oxide per mole of coconut alcohol; condensates of alkylphenols whose alkyl group contains 6-16 C-atoms with 2 to 25 moles of ethylene oxide per mole of alkylphenol; condensates of the reaction product of ethylenediamine and propylene oxide with ethylene oxide, the condensates containing from 40 to 80% of ethyleneoxy groups by weight and having a molecular weight of from 5,000 to 11,000.
  • tertiary amine oxides of general structure RRRNO where one R is a C 8 -C 22 alkyl group (preferably C 8 -C 18 ) and the other Rs are each C 1 -C 5 (preferably C 1 -C 3 ) alkyl or hydroxyalkyl groups, for instance dimethyldodecylamine oxide
  • tertiary phosphine oxides of structure RRRPO where one R is a C 8 -C 22 alkyl group (preferably C 8 -C 18 ) and the other Rs are each C 1 -C 5 (preferably C 1 -C 3 ) alkyl or hydroxyalkyl groups, for instance dimethyl-dodecylphosphine oxide
  • dialkyl sulphoxides of structure RRSO where one R is a C 10 -C 18 alkyl group and the other is methyl or ethyl, for instance methyltetradecyl sulphoxide
  • Suitable amphoteric surfactants are derivatives of aliphatic secondary and tertiary amines containing a C 8 -C 18 alkyl group and an aliphatic group substituted by an anionic water-solubilising group, for instance sodium 3-dodecylamino-propionate, sodium 3-dodecylaminopropane sulphonate and sodium N-2-hydroxydodecyl-N-methyl taurate.
  • Suitable cationic surfactants are quaternary ammonium salts having at least one C 8 -C 22 aliphatic or alkyl-aromatic group, e.g. dodecyl-trimethylammonium bromide or chloride, cetyltrimethyl-ammonium bromide or chloride, didecyl-dimethyl-ammonium bromide or chloride, octyl-benzyldimethyl-ammonium bromide or chloride, dodecyl- benzyldimethyl-ammonium bromide or chloride and (higher alkyl)- benzyldimethyl-ammonium bromide or chloride.
  • quaternary ammonium salts have antimicrobial properties and their use in cleaning compositions according to the invention leads to products having exceptionally effective disinfection properties against a wide range of micro-organisms. They are used in the cleaning compositions according to the invention in an amount of 0-10%, preferably 0.1-8%, more preferably 0.5-6%. Since virtually all cationic surfactants would be unstable in the presence of hypochlorite, when they are used, they should be incorporated in the second aqueous solution (i.e. the acid solution).
  • Suitable zwitterionic surfactants are derivatives of aliphatic quaternary ammonium, sulphonium and phosphonium compounds having a C 8 -C 18 aliphatic group and an aliphatic group substituted by an anionic water-solubilising group, for instance 3-(N,N-dimethyl-N-hexadecylammonium)propane-1-sulphonate betaine, 3-(dodecyl-methylsulphonium)-propane-1-sulphonate betaine and 3-(cetylmethyl-phosphonium)-ethane-sulphonate betaine.
  • Detergent surfactants often play an important role in thickening systems. Apart from that they are preferably added also for their wetting properties on hard surfaces and for their cleaning properties. Thus, preferably surfactants are present even if a non-surfactant thickening system is used. If not required for thickening, the total surfactants content is preferably between 0.1 and 20%, more preferably between 0.5 and 10%. If part of the thickening system the minimum total amount of surfactant will be at least 0.5%, preferably at least 1%.
  • Electrolytes are part of many thickening systems. Suitable salts are alkali metal carbonates, sulphates and halogenides. Electrolytes are used in an amount of 0-20%, preferably 0-15%, more preferably 0-10%.
  • thickening systems have been used in thickened hypochlorite bleach compositions. Such systems often consist of two or more different detergent surfactants, or of one or more such surfactants in combination with an electrolyte such as an inorganic salt. Many thickening systems comprise as one of their components tertiary amine oxides containing one long alkyl chain e.g. having 8-22 C atoms and two shorter alkyl chains e.g. having 1-5 C-atoms, often in combination with an anionic surfactant.
  • suitable thickening systems comprise polymeric substances which in solution thicken in response to an increase in pH or electrolyte concentration.
  • polymers of acrylic acid known for their thickening properties such as those sold under the trademark "Acusol”.
  • the final composition may be thickened if desired, preferably by a multi-component thickening system of which the components are divided over at least two partial compositions, such that on mixing of the partial compositions on delivery to the surface to be cleaned the combination of the components of the thickening system causes the final composition to thicken.
  • a multi-component thickening system of which the components are divided over at least two partial compositions, such that on mixing of the partial compositions on delivery to the surface to be cleaned the combination of the components of the thickening system causes the final composition to thicken.
  • the viscosity of the final composition after dispensing is at least 50 mPa.s, more preferably at least 100 mPa.s.
  • the viscosity is preferably not more than 1000 mPa.s.
  • a large number of multicomponent thickening systems is known in the art.
  • at least one component should be storage stable in the same partial composition as the hypochlorite bleach.
  • the total thickening system should be sufficiently stable in the final composition to enable it to thicken and remain on the surface for long enough to perform its cleaning action.
  • Another way to improve cling of the final composition to a non-horizontal surface is to cause it to foam on dispensing through the addition of a foaming surfactant to at least one partial composition and the use of an appropriate dispensing device such as foaming trigger sprays known in the art.
  • Surfactants which are storage stable in combination with the hypochlorite or hypochlorite source may be combined in the same (first) partial composition. Surfactants which do not have such stability should be made part of the other (second) partial composition.
  • the cleaning compositions according to the invention may also usefully contain a sequestering agent suitable for binding Ca ions.
  • Suitable sequestering agents for this purpose are well known in the art and include compounds such as: alkali metal tripolyphosphate, pyrophosphate and ortho- phosphate, sodium nitrilotriacetic acid salt, sodium methylglycine-diacetic acid salt, alkali metal citrate, carboxymethyl malonate, carboxymethyloxysuccinate, tartrate, mono- and di-succinate and oxydisuccinate.
  • the mixed composition on the surface may also contain polymers and other formulation components such as a perfume, colourant and foam control agents. Some or all of these additional components can be stored separately from the hypochlorite or hypochlorite source, i.e. together in the second solution with the acid, allowing use of formulation ingredients that do not have long term stability in strong oxidising agents and are therefore not used in conventional single compartment hypochlorite bleach formulations.
  • a typical non-limiting formulation suitable for delivery from a dual-compartment pack would be as follows:
  • Example 2a is the composition of a two-pack reduced alkalinity 'low' hypochlorite mould remover or kitchen cleaner formulation suitable for delivery from dual-compartment spray pack.
  • Compositions A & B are stable over extended periods and
  • Example 2b is the composition of the mixed formulation on delivery from the dual-compartment pack onto the surface.
  • Example 2a Typical partial compositions for a reduced alkalinity 'low' hypochlorite mould remover or kitchen cleaner Chemical Name % active level in formulation as delivered from pack Partial Composition A: Sodium xylene sulphonate 1.20 Sodium hydroxide 0.60 Sodium hypochlorite 1.00 Decyl-dimethyl amine oxide 0.40 Sodium laurate (soap) 0.20 Water to 100% Partial Composition B: Hydrochloric acid 0.55 Water to 100%
  • Example 2b Formulation of a prototype reduced alkalinity 'low' hypochlorite mould remover or kitchen cleaner on delivery to the surface formed upon mixture of the components of example 2a: Chemical Name % active level in formulation as delivered from pack Sodium xylene sulphonate 0.60 Sodium hydroxide 0.30 Sodium hypochlorite 0.5% Decyl-dimethyl amine oxide 0.20 Sodium laurate (soap) 0.10 Hydrochloric acid 0.275 Water to 100% The mixed formulation had a pH of 11.0
  • viscous products suitable for providing 'cling' to vertical surfaces are prepared by use of suitable surfactants or thickening agents. These are added to partial compositions A & B such that the partial compositions are non-viscous during storage but develop viscosity on mixing, during delivery from the pack.
  • a small amount of the 'mould paste' was applied to the surface of a porous ceramic tile and a small amount of distilled water added. This mixture was evenly spread across and rubbed into the surface of the tile using a flexible plastic spatula. Additional mould paste or water was added to ease the soiling process as necessary. The final appearance of the soiled tile was a uniform dark grey. The tiles were left to dry overnight in the dark and then large tiles were then cut into smaller test pieces using a standard 'tile cutter'.
  • test solution was allowed to remain in contact with the soil for a fixed contact time, i.e.
  • test piece was immersed in 1.0M sodium thiosulphate solution for 10 minutes (to quench the reaction and prevent further bleaching).
  • test pieces were then immersed in distilled water for 10 minutes before rinsing with further distilled water and air drying.
  • Test pieces were assessed for the level of mould bleaching by an expert panel, using a integer scale running from 0 (no decolorisation) to 6 (complete bleaching). Panel test data for each system were collated and analysed statistically to provide mean scores for each test system. Each test (bleaching) system was tested using at least 3 replicate tiles.
  • Example 4 Application as a Kitchen Cleaner
  • a length of pre-stained cotton cloth was cut into square swatches (2 cm x 2 cm).
  • Four replicate cloths were placed in the bottom of a clean glass beaker and covered with the cleaning liquor at room temperature. After a contact time of 2 to 5 minutes has elapsed, the cloths were removed from the cleaning solution using tweezers and immediately immersed in distilled water. The cloths were stirred in the water, and washing procedure repeated twice more using fresh water each time. Washed cloths were then pressed between two filters to remove excess water and placed on fresh filter papers, in the dark, to dry.
  • the test was designed to reflect the European Suspension Test protocol (European Standard EN1276).
  • the bacterial test suspension contained between 1.5 and 5.0 x 10 8 cfu.mL -1 .
  • test formulation was pre-diluted to the relevant concentration in sterile Water of Standard Hardness (24° French Hard). The presence of the bacterial test solution and interfering substance resulted in a further 1 : 1.25 dilution of the formulation in the test procedure.
  • Test Procedure A volume of the interfering substance was pipetted into a sterile container and an equal volume of the bacterial test suspension was added and contents of the tube were mixed. The bacteria and soil were allowed a contact time of 2 min ⁇ 10s. At the end of this contact time, a volume of the diluted formulation was added to produce an overall 1:10 dilution of both the bacterial test suspension and interfering substance and the contents of the tube were mixed again. The formulation was allowed a bactericidal contact time of 5 min ⁇ 10s.

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Abstract

A dual container delivery system comprises a first containing a first aqueous solution comprising a hypochlorite bleach or a source thereof and having a pH above 13. A second container contains an aqueous solution comprising an acid. Delivery means delivers the first and second solutions to a surface such that they mix just before or upon impacting the surface. The amount and strength of the acid in the second solution is such that the pH of the resulting mixture is from 8 to 13, preferably from 9 to 12.

Description

    Field of the Invention
  • The present invention relates to systems containing a halogen bleach source, for example for use as household cleaning products.
    • Background to the Invention
  • It is well known to use hypochlorite bleaches in household hard surface cleaning compositions, for example as kitchen surface cleaners typically containing 0.1-1.5% by weight of sodium hypochlorite at a pH of approximately 11.5-13.0, or at higher levels, e.g. up to 3% by weight of hypochlorite for mould removal. However, there remains a need to produce hypochlorite bleaching compositions giving the same high standards of cleaning (and hygiene) performance as these standard sodium hypochlorite household cleaning products but with lower hypochlorite levels to provide better sensory, safety and environmental properties.
  • The present invention solves this problem by reducing the pH of the hypochlorite solution at the point of delivery, by admixture with an acid.
  • WO-A-98/21308 describes the use of a dual-compartment pack to separate alkaline hypochlorite and a chlorine 'de-activating agent' such as sulphamic acid. The mixed formulation has a pH of around 6 and is said to give good bleaching of mould and food/beverage stains on hard and soft surfaces but, as sulphamic acid acts as a chlorine scavenger, without the risk of producing toxic chlorine gas. A hypochlorite to sulphamic acid ratio of 3.6 to 2.5 is specified to ensure adequate bleaching activity. The use of thickening agents in conjunction with these formulations, to provide "cling" to vertical surfaces, is also disclosed.
  • The present invention differs from that disclosed in WO-A-98/21308 in that the usage pH range is greater than 6 and for this reason the formulation need not contain an amine compound as a chlorine 'de-activating agent'.
  • Also, as disclosed in WO-A-99/32596, an aqueous solution of "a source of unipositive chlorine ions", typically sodium hypochlorite, contains a chlorine stabilising agent such as sulphamic acid or a salt thereof, or an organic sulphonate or sulphonamide, and an acidic buffer, typically a mono-, di- or polycarboxylic acid or phosphoric acid. The pH is buffered to be from around 2 to 6.5.
  • The present invention differs from that disclosed in WO-A-99/32596 in that being in two-pack form, the hypochlorite is stored at a more alkaline pH and therefore, does not require the chlorine stabilising agent.
  • There are several known examples of low pH hypochlorite bleaching systems in other applications. US-A-4 236 891 describes the use of magnesium hypochlorite maintained at a pH in the range 3.5-7.7, by addition of mineral or organic acids, for industrial or domestic bleaching of textiles. CA-A-1 087 955 relates to use of hydroxycarboxylic acid salts in reducing hypochlorite pH to between 5 and 8 for cleaning and disinfecting substrates including human skin and clothing.
    • Definition of the Invention
  • The present invention now provides a dual container delivery system comprising a first container containing a first aqueous solution comprising a hypochlorite bleach or a source thereof and having a pH of at least 13, a second container containing an aqueous solution comprising an acid and delivery means for delivering the first and second solutions to a surface such that they mix just before or upon impacting the surface, the amount and strength of the acid in the second solution being such that the pH of the resulting mixture is from 8 to 13, preferably from 9 to 12.
  • The pH of the first aqueous solution, i.e. that containing the hypochlorite, is at least 13. Furthermore, the pH of the composition resulting from mixing of the two aqueous solutions can also be as high as 13. However, it is to be understood that whatever the pH of the first aqueous solution before mixing, the pH of the resultant mixed solution will always be lower than that of the first aqueous solution, by virtue of the acid from the second aqueous solution.
  • Without being bound by any particular theory or explanation, the applicants have conjectured that the stability of sodium hypochlorite is optimised at high alkalinities where self-decomposition (disproportionation) and reactions with other formulation components are slow. Hypochlorite reactivity however increases with decreasing pH due to the increased levels of the conjugate acid, hypochlorous acid HOCl, which is a highly reactive electrophilic oxidant. These conflicting requirements for optimised reactivity and stability mean that standard hypochlorite based household cleaning formulations, which are delivered from single compartment formulations, use a combination of relatively high hypochlorite concentrations to maximise cleaning and hygiene activity, and relatively high alkalinities to maintain storage stability.
  • The present invention involves delivery of hypochlorite formulations of 'reduced' alkalinity by mixing an alkaline hypochlorite solution with an acid at the point of delivery. The alkaline hypochlorite and acid solutions are stored separately in the compartments of a dual-compartment pack and mix together during application onto the surface. In this way, the stability problems associated with use of reduced alkalinity hypochlorite are avoided. The higher reactivity of the less alkaline hypochlorite formulation allows a reduction in the level of hypochlorite required to achieve current standards of cleaning and hygiene.
  • Systems according to the invention are applicable for use in a range of products where relatively high concentrations of hypochlorite bleach are currently required to achieve acceptable cleaning and hygiene performance. Specific product types include mould removers, wc and kitchen cleaners.
    • Detailed Description of the Invention
  • Preferred forms of the first and second containers, the delivery means and the first and second aqueous solutions, will now be described in more detail.
    • The Containers
  • The first and second aqueous solutions need to be kept in different containers so that their components do not react until use. This could be achieved by providing them in respective separate containers. The consumer could then apply each to the surface, either sequentially or simultaneously.
  • However, it is more convenient to provide the products in a dual-compartment container in which the aqueous solutions are stored in separate compartments. The delivery means then allows them to be delivered to the surface so that pH reduction of the hypochlorite solution occurs or is initiated as they are exiting the delivery means and/or in mid-air as they are directed to the surface and/or on the surface itself. Preferably, they are delivered to be mixed in approximately equal volumes, i.e. typically from 0.5 : 1 v/v to 1 : 0.5 v/v.
  • A particularly preferred delivery means, especially for non-thickened systems, is a trigger spray head. In the case of a dual compartment system, this will preferably have two siphon tubes, respectively leading into each compartment and either a single nozzle with a mixing chamber or two separate nozzles substantially adjacent to each other. If desired, a dispensing nozzle or nozzles configured to promote foaming may be used.
  • For thickened systems a pouring dual compartment packaging form is generally preferred.
    • The Solutions
  • The hypochlorite or hypochlorite source is preferably present at about from 0.01% to 10% by weight, more preferably from 0.1% to 2%, most preferably from 0.05% to 0.5% by weight of the first aqueous solution. In the second solution, the amount of acid will depend on the alkalinity of the hypochlorite (first aqueous) solution. However, for typical commercial sources of hypochlorite solution, in the case when the acid in the second aqueous solution is a monovalent mineral acid, this will be typically present at about from 10 mole% to 200 mole%, more preferably from 50 mole% to 150 mole% based on the molar concentration of the hypochlorite present. The quantity of acid required to achieve a specific pH will of course depend on the quantity of additional alkali added to the first solution. For n-valent mineral acids, these values will be divided by n. In the case of organic acids, these amounts are more difficult to express as the range of strengths of such acids is quite large. However, for a dicarboxylic acid such as malic, maleic or succinic acid, typical ranges might be from 10 mole% to 300 mole%, more preferably from 50 % to 150 mole%.
  • The hypochlorite or source thereof in the first solution may be a simple hypochlorite salt such as those of the alkali or alkaline earth metals or a compound which produces hypochlorite upon hydrolysis, such as the organic N-chloro compounds. Mixtures of such materials may also be used.
  • The acid in the second solution may be a mineral acid such as hydrochloric, sulphuric, phosphoric or nitric acid. The term "acid" includes acidic salts such as sodium hydrogen sulphate. Alternatively, it may be organic acid such as a mono-, di- or polycarboxylic acid. Forms of any of these which are hydroxylated and/or contain keto and/or ester and/or amide groups may also be used. Saturated and unsaturated forms are included within these definitions.
  • Simple monocarboxylic acids such as formic acid and acetic acid may be used but are less preferred because of their unpleasant odours. A non-exhaustive list of typical suitable organic acids includes propanoic, lactic, glycolic, pyruvic, crotonic, isovaleric, cinnamic, salicylic, carbanic, methylcarbanic, benzoic, glucanic, malic, maleic, sulphonic, methane sulphonic, toluene sulphonic, fumaric, malonic, itaconic, oxalic, tartaric, glutamic, aspartic and succinic acids. However, citric acid is a generally preferred organic acid.
  • The acid component in the second aqueous solution may contain mixtures of two or more acids. However, whatever acid or acids are used, they preferably should not be of a type which would be oxidised within a few minutes of admixture with the hypochlorite. Again, mixtures of such materials may be used. The weight ratio of the hypochlorite or its precursor to the acid is typically from 0.01 : 1 to 100 : 1.
  • The hypochlorite (or source thereof) and acid solutions are stored separately using dual-compartmentalised packaging and react together on mixing during application onto the surface. The resulting mixed formulations give efficient bleaching from the relatively low levels of the hypochlorite. In a typical embodiment, the hypochlorite is present in alkaline solution, in order to minimise decomposition, while the acid is present at a level sufficient that on mixing the final pH of the formulation is optimised for the specific usage scenario. It is important that the mixing process be carefully controlled so that the pH of the final mixed solution is constrained not to fall below a value of 8. Attempts to achieve lower pH values could result in incomplete mixing and localised areas of very low pH with the consequent risk of generating toxic chlorine gas. The mixed composition may also contain surfactants, polymers and other formulation components such as a perfume, or dye. Some or all of these additional components can be stored separately from hypochlorite, i.e. together with the acid, allowing use of formulation ingredients that do not have long term stability in hypochlorite solution and are therefore not used in conventional single compartment hypochlorite bleach formulations.
    • Surfactants
  • The composition according to the invention optionally may comprise detergent actives (surfactants). These may be chosen from a wide range of anionic, nonionic, cationic, amphoteric or zwitterionic surfactants well known in the art.
  • Suitable anionic surfactants are e.g. water-soluble salts, particularly alkali metal, alkaline earth metal and ammonium salts, of organic sulphate esters and sulphonic acids having in the molecular structure a C8-C22 alkyl radical or a C10-C22 alkaryl radical.
  • Examples of such anionic surfactants are alcohol sulphate salts, especially those obtained from the fatty alcohols derived from the glycerides of tallow or coconut oil; alkyl-benzene sulphonates such as those having a C9-C11 radical. Examples of such anionic detergents are alcohol sulphate alkyl group attached to the benzene ring; secondary alkanesulphonates; sodium alkyl glyceryl ether sulphates, especially those ethers of the fatty alcohols derived from tallow and coconut oil; sodium fatty acid monoglyceride sulphates, especially those derived from coconut fatty acids; salts of 1-6 EO ethoxylated fatty alcohol sulphates; salts of 1-8 EO ethoxylated alkylphenol sulphates in which the alkyl radicals contain 4-14 C-atoms; the reaction product of fatty acids esterified with isethionic acid and neutralised with sodium hydroxide.
  • The preferred water-soluble synthetic anionic surfactants are the alkyl benzene sulphonates, the olefin sulphonates, the alkyl sulphates, and the higher fatty acid monoglyceride sulphates and fatty acid soaps.
  • A special class of anionic surfactants which may be used in the cleaning compositions according to the invention are hydrotropes which are known in the art specifically for their thickening or liquid structuring capabilities. Well known examples of such compounds are the alkali metal salts of toluene-, xylene- and cumene-sulphonic acid.
  • Suitable nonionic surfactants can be broadly described as compounds produced by the condensation of alkylene oxide groups, which are hydrophilic in nature, with an organic hydrophobic compound which may be aliphatic or alkylaromatic in nature. The length of the hydrophilic or polyoxyalkylene radical which is attached to any particular hydrophobic group can be readily adjusted to yield a water-soluble or water dispersible compound having the desired balance between hydrophilic and hydrophobic elements.
  • Particular examples include the condensation product of straight chain or branched chain aliphatic alcohols having 8-22 C-atoms with ethylene oxide, such as coconut oil fatty alcohol/ethylene oxide condensates having from 2 to 15 moles of ethylene oxide per mole of coconut alcohol; condensates of alkylphenols whose alkyl group contains 6-16 C-atoms with 2 to 25 moles of ethylene oxide per mole of alkylphenol; condensates of the reaction product of ethylenediamine and propylene oxide with ethylene oxide, the condensates containing from 40 to 80% of ethyleneoxy groups by weight and having a molecular weight of from 5,000 to 11,000. Other examples are: tertiary amine oxides of general structure RRRNO, where one R is a C8-C22 alkyl group (preferably C8-C18) and the other Rs are each C1-C5 (preferably C1-C3) alkyl or hydroxyalkyl groups, for instance dimethyldodecylamine oxide; tertiary phosphine oxides of structure RRRPO, where one R is a C8-C22 alkyl group (preferably C8-C18) and the other Rs are each C1-C5 (preferably C1-C3) alkyl or hydroxyalkyl groups, for instance dimethyl-dodecylphosphine oxide; dialkyl sulphoxides of structure RRSO where one R is a C10-C18 alkyl group and the other is methyl or ethyl, for instance methyltetradecyl sulphoxide; fatty acid alkylolamides; alkylene oxide condensates of fatty acid alkylolamides and alkyl mercaptans. Amine oxides are especially preferred because they blend very well with inorganic electrolytes and show good stability to hypochlorite bleach.
  • Suitable amphoteric surfactants are derivatives of aliphatic secondary and tertiary amines containing a C8-C18 alkyl group and an aliphatic group substituted by an anionic water-solubilising group, for instance sodium 3-dodecylamino-propionate, sodium 3-dodecylaminopropane sulphonate and sodium N-2-hydroxydodecyl-N-methyl taurate.
  • Suitable cationic surfactants are quaternary ammonium salts having at least one C8-C22 aliphatic or alkyl-aromatic group, e.g. dodecyl-trimethylammonium bromide or chloride, cetyltrimethyl-ammonium bromide or chloride, didecyl-dimethyl-ammonium bromide or chloride, octyl-benzyldimethyl-ammonium bromide or chloride, dodecyl- benzyldimethyl-ammonium bromide or chloride and (higher alkyl)- benzyldimethyl-ammonium bromide or chloride. Many quaternary ammonium salts have antimicrobial properties and their use in cleaning compositions according to the invention leads to products having exceptionally effective disinfection properties against a wide range of micro-organisms. They are used in the cleaning compositions according to the invention in an amount of 0-10%, preferably 0.1-8%, more preferably 0.5-6%. Since virtually all cationic surfactants would be unstable in the presence of hypochlorite, when they are used, they should be incorporated in the second aqueous solution (i.e. the acid solution).
  • Suitable zwitterionic surfactants are derivatives of aliphatic quaternary ammonium, sulphonium and phosphonium compounds having a C8-C18 aliphatic group and an aliphatic group substituted by an anionic water-solubilising group, for instance 3-(N,N-dimethyl-N-hexadecylammonium)propane-1-sulphonate betaine, 3-(dodecyl-methylsulphonium)-propane-1-sulphonate betaine and 3-(cetylmethyl-phosphonium)-ethane-sulphonate betaine.
  • Further examples of suitable surfactants are given in the well-known textbooks "Surface Active Agents", Volume I by Schwartz and Perry and "Surface Active Agents and Detergents", Volume II by Schwartz, Perry and Birch.
  • Detergent surfactants often play an important role in thickening systems. Apart from that they are preferably added also for their wetting properties on hard surfaces and for their cleaning properties. Thus, preferably surfactants are present even if a non-surfactant thickening system is used. If not required for thickening, the total surfactants content is preferably between 0.1 and 20%, more preferably between 0.5 and 10%. If part of the thickening system the minimum total amount of surfactant will be at least 0.5%, preferably at least 1%.
  • Electrolytes, particularly inorganic salts, are part of many thickening systems. Suitable salts are alkali metal carbonates, sulphates and halogenides. Electrolytes are used in an amount of 0-20%, preferably 0-15%, more preferably 0-10%.
  • Many thickening systems have been used in thickened hypochlorite bleach compositions. Such systems often consist of two or more different detergent surfactants, or of one or more such surfactants in combination with an electrolyte such as an inorganic salt. Many thickening systems comprise as one of their components tertiary amine oxides containing one long alkyl chain e.g. having 8-22 C atoms and two shorter alkyl chains e.g. having 1-5 C-atoms, often in combination with an anionic surfactant.
  • Examples of such thickening systems are described in EP-A-079697, EP-A-110544, EP-A-137551, EP-A-145084, EP-A-244611, EP-A-635568, WO95/08611, DE-A-19621048 and the literature cited in these patent applications.
  • Other suitable thickening systems comprise polymeric substances which in solution thicken in response to an increase in pH or electrolyte concentration. Examples thereof are polymers of acrylic acid known for their thickening properties such as those sold under the trademark "Acusol".
  • In the case of the dual container systems of the present invention, the final composition may be thickened if desired, preferably by a multi-component thickening system of which the components are divided over at least two partial compositions, such that on mixing of the partial compositions on delivery to the surface to be cleaned the combination of the components of the thickening system causes the final composition to thicken. This will improve the composition's ability to cling to a non-horizontal surface and prevent it from draining off before proper cleaning is obtained. Usefully the viscosity of the final composition after dispensing is at least 50 mPa.s, more preferably at least 100 mPa.s. On the other hand the viscosity is preferably not more than 1000 mPa.s.
  • A large number of multicomponent thickening systems is known in the art. For them to be suitable for the cleaning compositions according to the invention, preferably at least one component should be storage stable in the same partial composition as the hypochlorite bleach. The total thickening system should be sufficiently stable in the final composition to enable it to thicken and remain on the surface for long enough to perform its cleaning action.
  • Another way to improve cling of the final composition to a non-horizontal surface is to cause it to foam on dispensing through the addition of a foaming surfactant to at least one partial composition and the use of an appropriate dispensing device such as foaming trigger sprays known in the art.
  • Surfactants which are storage stable in combination with the hypochlorite or hypochlorite source may be combined in the same (first) partial composition. Surfactants which do not have such stability should be made part of the other (second) partial composition.
  • The cleaning compositions according to the invention may also usefully contain a sequestering agent suitable for binding Ca ions. Suitable sequestering agents for this purpose are well known in the art and include compounds such as: alkali metal tripolyphosphate, pyrophosphate and ortho- phosphate, sodium nitrilotriacetic acid salt, sodium methylglycine-diacetic acid salt, alkali metal citrate, carboxymethyl malonate, carboxymethyloxysuccinate, tartrate, mono- and di-succinate and oxydisuccinate.
    • Other Optional Components
  • The mixed composition on the surface may also contain polymers and other formulation components such as a perfume, colourant and foam control agents. Some or all of these additional components can be stored separately from the hypochlorite or hypochlorite source, i.e. together in the second solution with the acid, allowing use of formulation ingredients that do not have long term stability in strong oxidising agents and are therefore not used in conventional single compartment hypochlorite bleach formulations.
    • Examples A. FORMULATIONS Example 1
  • A typical non-limiting formulation suitable for delivery from a dual-compartment pack would be as follows:
  • Partial composition A: sodium hypochlorite - 1.0%, pH adjusted to 13.0 (in order to minimise hypochlorite decomposition).
  • Partial composition B: hydrochloric acid - 0.55%, pH 0.8.
  • Solutions A & B when dispensed from a suitable dual-compartment and mixed in equal proportions will produce a 'hypochlorite' solution with a pH of 11.0.
    • Example 2a and 2b
  • Example 2a is the composition of a two-pack reduced alkalinity 'low' hypochlorite mould remover or kitchen cleaner formulation suitable for delivery from dual-compartment spray pack. Compositions A & B are stable over extended periods and Example 2b is the composition of the mixed formulation on delivery from the dual-compartment pack onto the surface.
  • Example 2a: Typical partial compositions for a reduced alkalinity 'low' hypochlorite mould remover or kitchen cleaner
    Chemical Name % active level in formulation as delivered from pack
    Partial Composition A:
    Sodium xylene sulphonate 1.20
    Sodium hydroxide 0.60
    Sodium hypochlorite 1.00
    Decyl-dimethyl amine oxide 0.40
    Sodium laurate (soap) 0.20
    Water to 100%
    Partial Composition B:
    Hydrochloric acid 0.55
    Water to 100%
  • Example 2b: Formulation of a prototype reduced alkalinity 'low' hypochlorite mould remover or kitchen cleaner on delivery to the surface formed upon mixture of the components of example 2a:
    Chemical Name % active level in formulation as delivered from pack
    Sodium xylene sulphonate 0.60
    Sodium hydroxide 0.30
    Sodium hypochlorite 0.5%
    Decyl-dimethyl amine oxide 0.20
    Sodium laurate (soap) 0.10
    Hydrochloric acid 0.275
    Water to 100%
    The mixed formulation had a pH of 11.0
  • Further, if desired, viscous products suitable for providing 'cling' to vertical surfaces, such as wc bowls, are prepared by use of suitable surfactants or thickening agents. These are added to partial compositions A & B such that the partial compositions are non-viscous during storage but develop viscosity on mixing, during delivery from the pack.
    • B. CLEANING APPRAISAL DATA
  • Examples showing the enhanced cleaning efficacy of the reduced alkalinity/low hypochlorite solutions will now be described.
    • Example 3
  • Cultures of hyphal Cladosporium cladosporioides were prepared on agar jelly. Warm water was used to dissolve the jelly and separate it from the mould hyphae, which were then autoclaved. A little distilled water was added to the hyphae which were crushed to a 'paste' using a pestle and mortar. The 'paste' consisted of a mixture of fine particles of hyphal cell wall together with a dark black mould ink. Once prepared, the mould paste was stable to storage for several weeks at 5°C.
  • A small amount of the 'mould paste' was applied to the surface of a porous ceramic tile and a small amount of distilled water added. This mixture was evenly spread across and rubbed into the surface of the tile using a flexible plastic spatula. Additional mould paste or water was added to ease the soiling process as necessary. The final appearance of the soiled tile was a uniform dark grey. The tiles were left to dry overnight in the dark and then large tiles were then cut into smaller test pieces using a standard 'tile cutter'.
  • Small circular pieces of single ply tissue paper were cut to a convenient size and placed on the surface of the 'mould tile' test pieces, such that the edges of the test pieces remained uncovered. A fixed quantity of the test solution was allowed to drop onto the surface of the tissue and allowed to soak into the tile. The test solution only contacted that area of the tile that was originally covered by the tissue paper, thus preserving a background of untreated 'mould paste' around the periphery of the test piece about 1 cm3 of bleach liquor was required to cover a circular area around 3 cm in diameter). The test solution was allowed to remain in contact with the soil for a fixed contact time, i.e. about 3 minutes or 20 minutes, after which the test piece was immersed in 1.0M sodium thiosulphate solution for 10 minutes (to quench the reaction and prevent further bleaching). The test pieces were then immersed in distilled water for 10 minutes before rinsing with further distilled water and air drying.
  • Test pieces were assessed for the level of mould bleaching by an expert panel, using a integer scale running from 0 (no decolorisation) to 6 (complete bleaching). Panel test data for each system were collated and analysed statistically to provide mean scores for each test system. Each test (bleaching) system was tested using at least 3 replicate tiles.
  • Typical test data showing the effect of pH on mould bleaching are shown in Table 1.
  • The data show that the bleaching activity of a standard commercial sodium hypochlorite product (3.0% sodium hypochlorite, pH 13) can be achieved from just 0.5% sodium hypochlorite if the pH is reduced by a few units.
    Bleaching of 'autoclaved mould paste' by various hypochlorite containing systems (ambient temperature, 3 minutes contact time)
    Mean score
    pH
    Concentration of sodium hypochlorite (% w/w) 13.0 12.0 11.0 10.5 10.0
    0.2% 0.0 0.6 1.7 --- ---
    0.5% 1.3 2.2 3.1 4.2 5.6
    3.0% 5.4 6.0 --- --- ---
    • Example 4: Application as a Kitchen Cleaner
  • A length of pre-stained cotton cloth was cut into square swatches (2 cm x 2 cm). Four replicate cloths were placed in the bottom of a clean glass beaker and covered with the cleaning liquor at room temperature. After a contact time of 2 to 5 minutes has elapsed, the cloths were removed from the cleaning solution using tweezers and immediately immersed in distilled water. The cloths were stirred in the water, and washing procedure repeated twice more using fresh water each time. Washed cloths were then pressed between two filters to remove excess water and placed on fresh filter papers, in the dark, to dry.
  • Reflectance measurements were carried out on a Spectraflash 400 instrument. ▵R measurements were calculated using '40ptspec' software, using a portion of untreated cloth from the same cloth batch as a standard. Results obtained from each of the four replicate test cloths were then statistically analysed to obtain mean ▵R values for each bleach system. Test data showing the effect of reducing the pH of the sodium hypochlorite are shown in Table 2.
    Bleaching of tea stained cotton cloth (BC-1) by 'acidified' hypochlorite (1 minute contact time ambient temperature, c.a. 20°C).
    Mean Δ R (460nm)
    pH
    Concentration of sodium hypochlorite 13.0 12.0 11.0 10.0 9.0
    0.1% 4 8 13 16 18
    1.0% 10 22 26 27 28
  • The results show that bleaching efficacy of the hypochlorite significantly enhanced by controlled acidification. By this means, a ten-fold reduction in sodium hypochlorite content can be made whilst maintaining bleaching performance by reducing the 'in-use' pH by a few units. Thus a 0.1% sodium hypochlorite formulation at pH 11.0 can provide performance parity with a typical commercial based kitchen cleaner formulation containing c.a. 0.5% - 1.5% sodium hypochlorite at a pH of 11.0-13.0.
    • Example 5: Bactericidal Performance of Mixed Systems on Dilute Application
  • The test was designed to reflect the European Suspension Test protocol (European Standard EN1276). The bacterial test suspension contained between 1.5 and 5.0 x 108 cfu.mL-1.
  • Testing was performed under conditions of heavy soil. A stock solution of 3% bovine albumin was prepared as an interfering substance. The test formulation was pre-diluted to the relevant concentration in sterile Water of Standard Hardness (24° French Hard). The presence of the bacterial test solution and interfering substance resulted in a further 1 : 1.25 dilution of the formulation in the test procedure.
  • Test Procedure: A volume of the interfering substance was pipetted into a sterile container and an equal volume of the bacterial test suspension was added and contents of the tube were mixed. The bacteria and soil were allowed a contact time of 2 min ± 10s. At the end of this contact time, a volume of the diluted formulation was added to produce an overall 1:10 dilution of both the bacterial test suspension and interfering substance and the contents of the tube were mixed again. The formulation was allowed a bactericidal contact time of 5 min ± 10s.
  • At the end of the contact time an aliquot was removed and diluted 1:10 into a sterile container containing a suitable chemical quenching solution. The contents were mixed thoroughly and left for a contact time of 5 min ± 1 minute. The dilution process was repeated a further five times into a suitable diluent to produce a series of six dilutions of the bactericidal stage ranging from 10-1 to 10-6.
  • Total viable counts were enumerated by a suitable method and the reduction in number of viable cells elicited by the test formulation was calculated. Table 3 shows the biocidal activity of hypochlorite delivered from stock solutions at pH 13.4 and 9.0. The results were achieved after 1 : 40 dilution of the test formulation.
    Biocidal activity
    Log Reduction (SD)
    S. aureus E. hirae
    NaOCl (%)
    pH 13.4 1.2 2.03 (0.36) 0.23 (0.09)
    1.6 3.53 (0.89) 1.27 (1.03)
    2.0 4.67 4.78
    pH 9 1.2 3.18 (0.45) 1.58 (0.49)
    1.6 4.67 4.34 (0.89)
    2.0 4.67 4.78
  • A reduction in pH from 13.4 to 9.0 when the two solutions were mixed prior to dilution resulted in increased bactericidal activity from low levels of hypochlorite (<2.0%).

Claims (6)

  1. A dual container delivery system comprising a first container containing a first container containing a first aqueous solution comprising a hypochlorite bleach or a source thereof and having a pH above 13, a second container containing an aqueous solution comprising an acid and delivery means for delivering the first and second solutions to a surface such that they mix just before or upon impacting the surface, the amount and strength of the acid in the second solution being such that the pH of the resulting mixture is from 8 to 13, preferably from 9 to 12.
  2. A system according to claim 1, wherein the first and second containers respectively are in the form of first and second compartments of a dual-compartment container.
  3. A system according to either preceding claim, wherein the delivery means is in the form of a trigger-spray head, or pouring system.
  4. A system according to any preceding claim, wherein the first aqueous solution contains from 0.01% to 10% by weight, preferably from 0.1% to 2% by weight of the hypochlorite or hypochlorite source.
  5. A system according to any preceding claim, wherein the second aqueous solution contains from 0.01% to 5%, preferably from 0.1% to 2% by weight of the acid.
  6. A system according to any preceding claim, wherein the weight ratio of the hypochlorite or its precursor to the acid is from 0.01 : 1 to 100 : 1.
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