This invention relates to cleaning compositions and their use.
Bathroom cleaners are mainly acidic compositions, intended to combat calcium deposits. On the other hand kitchen cleaners are mainly alkaline compositions, intended to combat grease deposits. However there are situations in which for bathroom cleaning, an alkaline composition is required; and in which for kitchen cleaning, an acidic cleaning composition is required. The customer has to decide whether to purchase a plethora of different products for different cleaning tasks, or whether to compromise. It would be good to have a single composition which was able to combat the deposits attacked by acidic cleaning compositions and the deposits attacked by alkaline cleaning compositions, but the difficulty in achieving this is self-evident.
It would also be advantageous to have a cleaning composition which is initially acidic or alkaline, to effect cleaning, but which does not remain so, in order to prevent damage to a substrate and, if wished, to effect a second stage of cleaning.
In accordance with a first aspect of the present invention there is provided a cleaning composition which comprises reactants which undergo a chemical reaction after exposure to a locus to be cleaned, the reaction being such as to produce a delayed change of pH at that locus.
In accordance with a second aspect of the present invention there is provided a cleaning composition having the property that on exposure to a locus to be cleaned the locus renders acidic or alkaline or neutral, and that after an interval it renders the locus alkaline or neutral (if originally acidic) or acidic or neutral (if originally alkaline) or acidic or alkaline (if originally neutral).
The composition of any of the aspects may have the property that the locus containing the composition is initially an acidic liquid and after an interval becomes an alkaline liquid.
The composition of any of the aspects may have the property that the locus containing the composition is initially an alkaline liquid and after an interval becomes an acidic liquid.
Preferably the pH change takes place after an induction period (that is, an interval after exposure of the composition to the locus) of at least 10 seconds, more preferably at least 20 seconds, most preferably at least 60 seconds, and, especially, at least 100 seconds.
Suitably the said induction period is not more than 12 hours, preferably not more than 1200 seconds, more preferably not more than 600 seconds, most preferably not more than 400 seconds, and, especially, not more than 300 seconds.
A composition of the invention could be a single-pack composition, with the reactants being held in stasis if necessary. In such embodiments the pH change which takes place may be initiated by addition of an agent from which the reactants were previously protected. For example, it could be water, or oxygen, or carbon dioxide, or light.
Alternatively the reactants could be kept physically separated from each other prior to their use, as for example in a tablet or dissolvable sachet having two or more zones, which may be layers, portions or encapsulated sections, depending on the type of tablet or sachet, or in a twin-bottle package or twin-tablet package. In all such embodiments the key measure is that the reactants are combined only at the time of cleaning.
The composition may be provided in a package which emits the composition as a spray, mousse, gel or liquid jet. The package may suitably be a trigger spray or, preferably, an aerosol canister. A spray-emitting package of the composition, especially an aerosol canister, constitutes a further aspect of the invention. In other embodiments a wipable product, for example a sponge or cloth, is impregnated with a composition.
The composition may be a product for dilution in order to be used, or a product in ready-to-use form. When a product is for dilution, it may be a solid, for example a powder or tablet, or a liquid, or a gel.
The composition may be provided in packaging giving unit-dose supply of the composition.
The composition may be such that the chemical reaction causes a colour change. One or more of the reactants responsible for the change of pH may cause a change of colour, for example on exhaustion, or a separate dye or colorant may be included in the composition, responsive to pH change or to the presence of oxidant species, or reductant species, or temperature change in the case of an exothermic reaction.
Other means of indicating chemical change than colour may be employed. For example the system could be arranged to effervesce when the reaction takes place, for example by including a bicarbonate in a system which becomes acidic after the induction period. Another method useful in the case of an exothermic reaction employs a fragrance rendered volatile by a temperature rise.
The term “cleaning” as used herein may include: removal of soil deposits: prevention of soiling; bleaching; combating of allergens; and combating of microbes, including by one or more of antiseptic, disinfectant, bactericidal, sporicidal, fungicidal and viricidal action.
Preferably, the composition is antimicrobial. Preferably an antimicrobial effect is generated by the reaction, for example by temperature rise when the reaction is exothermic and/or by the pH change at the locus and/or by production of an antimicrobial chemical, in the reaction. Preferably an antimicrobial chemical is generated in situ by the reaction which changes the pH, and therefore with the same delay. The antimicrobial chemical may, for example, comprise an iodate, bromate, thiocyanate or chlorate.
The composition preferably produces a bleaching effect. Preferably a bleaching effect is generated by the reaction, for example by the temperature when the reaction is exothermic and/or by the pH change at the locus and/or by production of a bleaching chemical, in the reaction. Preferably a bleaching agent is produced in situ by the reaction which changes the pH, and therefore with the same delay. For example, the composition may include sodium chlorite generating, under acid conditions, sodium hydroxide and chlorine dioxide. Thus, both a bleaching agent and an alkaline agent may be generated.
Suitably the composition may contain hydrogen peroxide or a precursor to it as a bleaching agent and/or reactant.
The composition may include one or more surfactants. A surfactant used in the present invention may be selected from one or more surfactants which may be anionic, cationic, nonionic or amphoteric (zwitterionic) surface active agents.
One class of nonionic surfactants which may be used in the present invention are alkoxylated alcohols, particularly alkoxylated fatty alcohols. These include ethoxylated and propoxylated fatty alcohols, as well as ethoxylated and propoxylated alkyl phenols, both having alkyl groups of from 7 to 16, more preferably 8 to 13 carbon chains in length.
Examples of alkoxylated alcohols include certain ethoxylated alcohol compositions presently commercially available from the Shell Oil Company (Houston, Tex.) under the general trade name NEODOL (trade mark), which are described to be linear alcohol ethoxylates and certain compositions presently commercially available from the Union Carbide Company, (Danbury, Conn.) under the general trade name TERGITOL (trade mark) which are described to be secondary alcohol ethoxylates.
Examples of alkoxylated alkyl phenols include certain compositions presently commercially available from the Rhône-Poulenc Company (Cranbury, N.J.) under the general trade name IGEPAL (trade mark), which are described as octyl and nonyl phenols.
Another class of non-ionic surfactants that may be used are sorbitan esters of fatty acids, typically of fatty acids having from 10 to 24 carbon atoms, for example sorbitan mono oleate.
Examples of anionic surface active agents which may be used in the present invention include but are not limited to: alkali metal salts, ammonium salts, amine salts, aminoalcohol salts or the magnesium salts of one or more of the following compounds: alkyl sulphates, alkyl ether sulphates, alkylamidoether sulphates, alkylaryl polyether sulphates, monoglyceride sulphates, alkylsulphonates, alkylamide sulphonates, alkylarylsulphonates, olefinsulphonates, paraffin sulphonates, alkyl sulfosuccinates, alkyl ether sulfosuccinates, alkylamide sulfosuccinates, alkyl sulfosuccinamate, alkyl sulfoacetates, alkyl phosphates, alkyl ether phosphates, acyl saronsinates, acyl isothionates and N-acyl taurates. Generally, the alkyl or acyl group in these various compounds comprises a carbon chain containing 12 to 20 carbon atoms.
Other anionic surface active agents which may be used include fatty acid salts, including salts of oleic, ricinoleic, palmitic and stearic acids; copra oils or hydrogenated copra oil acid, and acyl lactylates whose acyl group contains 8 to 20 carbon atoms.
Amphoteric surfactants which may be used in the present invention including amphoteric betaine surfactant compounds having the following general formula:
wherein R is a hydrophobic group which is an alkyl group containing from 10 to 22 carbon atoms, preferably from 12 to 18 carbon atoms, an alkylaryl or arylalkyl group containing a similar number of carbon atoms with a benzene ring being treated as equivalent to about 2 carbon atoms, and similar structures interrupted by amido or either linkages; each R1 is an alkyl group containing from 1 to 3 carbon atoms; and R2 is an alkylene group containing from 1 to 6 carbon atoms.
One or more such betaine compounds may be included in the compositions of the invention.
Examples of cationic surfactants which may be used in the present invention include quaternary ammonium compounds and salts thereof, including quaternary ammonium compounds which also have germicidal activity and which may be characterized by the general structural formula:
when at least one of R1, R2, R3 and R4 is a hydrophobic, aliphatic, aryl aliphatic or aliphatic aryl group containing from 6 to 26 carbon atoms, and the entire cationic portion of the molecule has a molecular weight of at least 165. The hydrophobic groups may be long-chain alkyl, long-chain alkoxy aryl, long-chain alkyl aryl, halogen-substituted long-chain alkyl aryl, long-chain alkyl phenoxy alkyl or aryl alkyl. The remaining groups on the nitrogen atoms, other than the hydrophobic radicals, are generally hydrocarbon groups usually containing a total of no more than 12 carbon atoms. R1, R2, R3 and R4 may be straight chain or may be branched, but are preferably straight chain, and may include one or more amide or ester linkages. X may be any salt-forming anionic moiety.
Examples of quaternary ammonium salts within the above description include the alkyl ammonium halides such as cetyl trimethyl ammonium bromide, alkyl aryl ammonium halides such as octadecyl dimethyl benzyl ammonium bromide, and N-alkyl pyridinium halides such as N-cetyl pyridinium bromide. Other suitable types of quaternary ammonium salts include those in which the molecule contains either amide or ester linkages, such as octyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride and N-(laurylcocoaminoformylmethyl)-pyridinium chloride. Other effective types of quaternary ammonium compounds which are useful as germicides includes those in which the hydrophobic moiety is characterized by a substituted aromatic nucleus as in the case of lauryloxyphenyltrimethyl ammonium chloride, cetylaminophenyltrimethyl ammonium methosulphate, dodecylphenyltrimethyl ammonium methosulphate, dodecylphenyltrimethyl ammonium chloride and chlorinated dodecylphenyltrimethyl ammonium chloride.
Preferred quaternary ammonium compounds which act as germicides and which are useful in the present invention include those which have the structural formula:
wherein R2 and R3 are the same or different C8-C12alkyl, or R2 is C12-C16alkyl, C8-C18alkylethoxy, C8-C18alkylphenolethoxy and R3 is benzyl, and X is a halide, for example chloride, bromide or iodide, or methosulphate. Alkyl groups R2 and R3 may be straight chain or branched, but are preferably substantially linear.
A mixture of two or more surface active agents may also be used. Other known surface active agents not particularly described above may also be used. Such surface active agents are described in McCutcheon's Detergents and Emulsifiers, North American Edition, 1982; Kirk-Othmer, Encyclopaedia of Chemical Technology, 3rd Ed., Vol. 22, pp 346-387.
The compositions of the present invention may include therein one or more organic solvents, such as lower alkyl alcohols, lower alkyl diols or glycol ethers. Such compounds may function as a cleaning agent of the compositions, and may be especially useful in glass cleaners due to their lack of tendency to smear.
Preferably the composition is such that after exposure to an locus to be cleaned its temperature rises, preferably caused by the reaction which changes the pH, and therefore with the same delay. Thus, the reaction responsible for change in pH is preferably exothermic.
The composition may be such that after one pH change the pH may change in the reverse direction. For example a composition may go from acidic to alkaline and back to to acidic, or from alkaline to acidic and back to alkaline. It is possible that such compositions may undergo further pH changes. Each pH change preferably takes place over an induction period as defined above.
Thus, cleaning compositions based on pH-oscillatory systems may be envisaged. Suitable systems may include those described in the following references:
Oscillation, Waves and Chaos in Chemical Kinetics, S. K. Scott, Oxford University Press, 1995.
Design of pH-Regulated Oscillators, G. Rabai et al, Acc. Chem. Res., 1990,23,258-263.
A General Model for pH Oscillators, Y. Luo et al, J. Am. Chem. Soc., 1991,113,1518-1522.
Temperature compensation in the oscillatory hydrogen peroxide-thiosulfate-sulphite flow system, G. Rabai et al, Chem. Commun., 1999,1965-1966.
Kinetic Role of CO2 in the Oscillatory H2O2—HSO3 −—HCO3 − Flow System—G. Rabai et al, J. Phys. Chem. A1999,103, 7224-7229.
Chaotic pH oscillations in hydrogen peroxide-thiosulfate-sulphite flow system, G. Rabai et al, J. Phys. Chem. A1999,103,7268-7273.
Thus, preferably the composition may contain components which provide an abrupt pH step. The autocatalytic species for the reaction is H+ (or, more rarely, OH−) and pH steps may occur when a solution of a weak acid is oxidised to provide a strong acid, so that H+ concentration increases with the extent of reaction.
The chemical composition of a typical pH step system will involve an oxidant and a reductant. Typically, the reductant will be the salt of a weak acid and the corresponding oxidant will be a strong acid. Of course, a reaction may employ a plurality of oxidants and/or a plurality of reductants.
Many different species can be used as partners in these redox systems. In seeking appropriate species, a useful guide for the overall reaction stoichiometry is that the reducing agent should release more protons per electron than the oxidising agent consumes.
Within the existing literature, the following species can be identified and may be of use in cleaning compositions:
I peroxo-compounds (eg BrO3 −, IO3 −, ClO3 −, ClO2 −, S2O8 2−, ClO2, H2O2 or a precursor thereof)
II oxidising metal compounds stable in alkaline solutions (eg [Fe(CN)6]3−).
I all oxyanions of sulphur that contain S—S bonds (eg S2O3 2−, S4O6 2−, S2O4 2−, S2O6 2−).
II reducing agents that are significantly more basic than their oxidised counterparts (eg SO3 2−, HSO3 −, AsO3 3−, S2O3 2−, S4O6 2−, N2H5 +, [Fe(CN)6]4−).
Based on reactions described in the published literature, a matrix of combinations from some of these species can be constructed:
|Reductant || || || || || || |
|oxidant ||S2O3 2− ||S4O6 2− ||S2O4 2− ||SO3 2− ||S2O6 2− ||N2H5 + |
|BrO3 − ||Yes ||Yes ||Yes ||Yes ||Yes ||Yes |
|IO3 − ||No ||No ||Yes ||Yes ||Yes ||Yes |
|ClO3 − ||No ||Yes ||No ||No ||Yes ||No |
|ClO2 − ||Yes ||Yes ||Yes ||Yes ||Yes ||Yes |
|S2O8 2− ||Yes ||Yes ||Yes ||Yes ||Yes ||Yes |
where “Yes” indicates established evidence for pH step behaviour and “No” indicates no observed reaction under conditions investigated to date.
The most widely studied pH step reactions are those typified by the Landolt clock reaction, in which the oxidant is of formula XOn − when X is Cl, Br or I and n is 3 when X is Br or I, and 2, 3 or 4 when X is Cl; and the reductant is SO3 2−/HSO3 −. The classic Landolt system employs IO3 − as oxidant and is SO3 2−/HSO3 − as reductant. The reaction is autocatalytic in I− (depending on the second power of the iodide ion concentration) and is a pH step reaction system even in buffered solution. In unbuffered solution, the reaction is also autocatalytic in H+.
Beyond those combinations mentioned above, there are reports of pH step reactions with associated pH changes involving the following reagents:
permanganate ion as oxidant with reductant being sulphite, nitrite, selenite, arsenite thiosulfate+iodide+H2O2 or a precursor thereof.
Examples of precursors of hydrogen peroxide include urea hydrogen peroxide (UHP) and a cyclodextrin complexed with an organic peroxy acid, for example as described in EP-A-895777. An example is β-cyclodextrin complexed with an organic peroxy acid, e-phthalimido peroxyhexanoic acid (PAP). This product is available under the trade mark EURECO HC from Wacker Chemie GmbH.
The addition of a second reductant to a Landolt system (“mixed-Landolt system”) may produce a pH step reaction in which the pH swings from high to low at the end of an induction period, and then back to high pH on a longer timescale.
An example of a pH step reaction system starting at low pH and changing to high pH at the end of an induction period involves the reduction of H2O2 (which may be delivered by means of a precursor, as described above) by various multidentate complexes of Fe(II) or Co(II) ions, notably using Fe(CN)6 4− as the anion species, as described in G. Rabai et al, J. Am. Chem. Soc., 1989, III, p. 3870.
Cleaning compositions of the invention may be used, for example, for textile materials, including carpets and clothes. They may be used in dishwasher cleaning compositions and clothes washing compositions. The change of pH may, for example, initiate the dissolution of the coating of a washing tablet or of an insert product contained within a washing tablet, providing in each case delayed release of the contents.
A preferred cleaning composition of the present invention is a hard surface cleaner, for cleaning ceramics, glass, stone, plastics and wood; and particularly for cleaning bathroom and kitchen hard surfaces, for example sinks, bowls, toilets, panels, tiles and worktops. When acidic it is particularly effective in combating limescale. When alkaline it is particularly effective in combating grease and proteinaceous deposits.
Another preferred cleaning composition is adapted for cleaning dentures (normally of polyacrylic material) and is therefore effective in removing staining and/or plaque.
Another preferred cleaning composition is adapted for cleaning lavatory bowls and for this purpose the composition may be packaged in an ITB (In the Bowl) or ITC (In the Cistern) device, preferably in a holder which hangs from the rim of the bowl or cistern. In the case of chemical reactants which are desirably kept apart until cleaning takes place the reactants are preferably liquids kept in separate vessels, or solids formulated in separate tablets (for example compressed powders or granules, or gel blocks) or in one tablet with distinct zones for the different reactants. Of course, in some systems the reactants may be mixed and only react in use, in which case a single vessel or simple tablet may be used.
Another useful cleaning composition is adapted to clean marble surfaces effectively. Such a composition is acidic when applied in order to attack certain stains and soils, but becomes alkaline before any dissolution of the marble can occur. When alkaline it attacks other stains and soils, notably greases.
The invention will now be further described, by way of example, with reference to the following examples. Unless otherwise stated solutions of the reactants in distilled water were mixed at ambient temperature and stirred with a magnetic stirrer, whilst pH and temperature were monitored. Cationic species were sodium ions.