CLEANING METHOD OF HARD SURFACES

Description

[0001] This invention relates to a method of cleaning a hard surface which is subject to deposition by limescale.

[0002] 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.

[0003] The patent document US 4 522 738 also solves the problem of removing scale deposits on toilet bowls. It discloses toilet bowl cleaners having inner and outer water-soluble envelopes. The inner envelope contains basic material and the outer envelope contains acidic material which dissolves first and then the inner envelop. The amounts are chosen in that way that the pH changes to release carbon dioxide gas, thereby agitate the bowl water and thus enhance the cleaning process.

[0004] The British patent document GB 2 000 177 discloses compositions for laundry washing based on an alkali metal carbonate which pH changes from acid to alkaline. There is no mentioning of removing the limescale on hard surfaces.

[0005] 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.

[0006] In accordance with a first aspect of the present invention there is provided a method of cleaning a hard surface which is subject to deposition by limescale, the method comprising the application to the hard surface of a cleaning composition which comprises reactants which undergo a chemical reaction after exposure to the hard surface to be cleaned, the reaction being such as to produce a delayed change of pH at the hard surface, the composition being initially an alkaline liquid and after an interval becomes an acidic liquid effective in combating limescale.

[0007] In accordance with a second aspect of the present invention there is provided a cleaning composition having the property that on exposure to a hard surface 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).

[0008] The composition of any of the aspects may have the property that the hard surface containing the composition is initially an acidic liquid and after an interval becomes an alkaline liquid.

[0009] 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.

[0010] Preferably the pH change of at least 2 pH units 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] The composition may be provided in packaging giving unit-dose supply of the composition.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] Suitably the composition may contain hydrogen peroxide or a precursor to it as a bleaching agent and/or reactant.

[0023] 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.

[0024] 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.

[0025] Examples of alkoxylated alcohols include certain ethoxylated alcohol compositions presently commercially available from the Shell Oil Company (Houston, TX) 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, CT) under the general trade name TERGITOL (trade mark) which are described to be secondary alcohol ethoxylates.

[0026] Examples of alkoxylated alkyl phenols include certain compositions presently commercially available from the Rhône-Poulenc Company (Cranbury, NJ) under the general trade name IGEPAL (trade mark), which are described as octyl and nonyl phenols.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] One or more such betaine compounds may be included in the compositions of the invention.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] Within the existing literature, the following species can be identified and may be of use in cleaning compositions:

Potential oxidant:

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-).

Potential reductant:

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-).

[0044] Based on reactions described in the published literature, a matrix of combinations from some of these species can be constructed:

where "Yes" indicates established evidence for pH step behaviour and "No" indicates no observed reaction under conditions investigated to date.

[0045] The most widely studied pH step reactions are those typified by the Landolt clock reaction, in which the oxidant is of formula XO_n^- 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⁺.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Another preferred cleaning composition is adapted for cleaning dentures (normally of polyacrylic material) and is therefore effective in removing staining and/or plaque.

[0053] 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.

[0054] 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.

[0055] 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.

Example 1

[0056] The variations of the induction period (the period between mixing of reactants and commencement of pH swing) and of pH swing with initial reactant concentrations for a dilute solution of bromate and sulphite ions, mixed as solutions at ambient temperature, and using concentrated sulphuric acid to adjust the pH, were determined in a series of experiments. As can be seen from Table 1 below, the induction period t_ind can be varied between 4 hours and 2 minutes, with t_ind being approximately inversely proportional to the initial concentrations of both BrO₃^- and H⁺ and independent of the initial concentration of SO₃^2-. The initial sulphite concentration appears to determine the pH swing, which is typically of the order of 4 to 5 pH units. The reaction occurs for compositions with initial pH values in the range 6.6 to 8.9.

Table 1

[BrO3-]0 = 0.06 M, [SO32-]0 = 0.054 M
Initial pH	Final pH	pH change	tind[s]
8.85	3.65	5.2	14400
8.5	3.4	5.1	9000
8.2	2.9	5.3	5580
8.0	2.7	5.3	4080
7.48	2.4	5.08	1320
7.18	2.25	4.93	695
6.9	2.15	4.75	390
6.57	2.04	4.53	140

[0057] The initial experiments were repeated varying the initial concentration of bromate ions in a sequence, with constant initial pH and sulphite concentration. This yielded the variations in induction period shown in Table 2 below.

Table 2

[BrO3-]0/M	0.06	0.054	0.048	0.042	0.036	0.030	0.024
tind/s	285	350	390	465	470	660	810

[0058] The initial experiments were then repeated with variations in the concentration of the reductant species sulphite, at constant bromate and initial pH. The effect of this on the induction period and pH swing is set out in Table 3 below.

Table 3

[SO32-]0	tind/s	Final pH
0.054	300	1.95
0.0486	325	1.95
0.0432	310	2.0
0.0324	290	2.0
0.027	305	2.05
0.0216	305	2.1

with [BrO₃^-]₀ = 0.06 M and an initial pH = 7.0.

[0059] Thus in these experiments induction period and pH swing were relatively insensitive to [SO₃^2-]₀.

[0060] Overall, the results showed that the system is of value as the basis for a new cleaning composition.

Example 2

[0061] A series of experiments were run with substantially higher concentrations of the reactants than used in Example 1, with the aim of using the concentration dependence to reduce the induction period whilst maintaining a large pH swing. Also, rather than adjusting the initial pH with concentrated sulphuric acid after dissolution of the reactants, the required initial pH was attained by using an appropriate mixture of sulphite and bisulphite salts. The variations with initial reductant concentrations of the induction period, final pH and the peak temperature observed during the reaction are given in Table 4 below. The results showed that the system could provide the basis of a promising new cleaning composition.

Table 4

[BrO3-]0 /M	[SO32-]0 /M	[S2O52-]0 /M	Initial pH	tind/s	Final pH	Peak temp/°C
0.27	0.516	0.018	7.9	438	2.1	48
0.27	0.555	0.018	7.95	432	2.1	49
0.27	0.62	0.018	7.95	438	2.1	56
0.27	0.674	0.018	7.95	580	2.1	54
0.27	0.754	0.018	8.0	77	2.4	54
0.3	0.516	0.018	7.85	374	2.1	46
0.3	0.555	0.018	7.95	418	2.1	50
0.3	0.62	0.018	7.95	358	2.2	57
0.3	0.67	0.018	8.0	395	2.2	58.5
0.3	0.674	0.018	8.0	395	2.2	58.5
0.3	0.754	0.018	8.05	608	2.3	57
0.35	0.56	0.021	7.85	238	2.05	53
0.35	0.6	0.021	7.95	262	2.1	54
0.35	0.63	0.021	7.9	284	2.1	56
0.35	0.71	0.021	8.05	314	2.2	59
0.35	0.79	0.021	8.05	347	2.35	61
0.35	0.875	0.021	8.05	423	2.5	60
0.4	1.0	0.026	8.0	227	2.5	77
0.539	1.24	0.042	8.0	97	2.4	93
0.539	1.24	0.036	8.2	142	2.7	92
0.539	1.24	0.03	8.4	178	3.0
0.539	1.24	0.024	8.8	532	4.0	70
0.6	1.24	0.024	8.7	325	3.8	78

Example 3

[0062] In this example the classic iodate-sulphite/bisulphite Landolt reaction was examined. The induction period is well known to be inversely proportional to the initial iodate ion concentration and to be independent of the initial sulphite ion concentration (provided the initial pH is maintained constant). The dependence of t_ind on the initial pH is less well understood, so these data were determined in the present programme. The solutions were of concentration 0.01M iodate (fixed) and 0.02-0.002M bisulphite. The results are set out in Table 5 below. In all cases the final pH was 2.2-2.3.

Table 5

pH0	6.8	7.0	7.2	7.3	7.4	7.5	7.6	7.7	7.8	7.8
tind/s	27	62	48	78	90	198	220	480	450	600

Example 4

[0063] The chlorate ion ClO₃^- can also be used as the oxidant in Landolt-type systems. A series of experiments were performed on this system. The reaction does not appear to occur starting from pH values higher than ca. 5.0, so the initial pH was adjusted using concentrated H₂SO₄ to the range 4.5-5.0 for the experiments reported below. The reaction is strongly exothermic and even for relatively dilute solutions, significant temperature rises (self-heating) occur. The results are set out in Table 6 and 7 below.

Table 6 -

variation of induction period with initial chlorate concentration
[SO32-]0 = 0.44 M, initial pH = 4.5

[ClO3-]0/M	tind/s	Final pH	Peak temperature/°C
0.29	128	0.4	45.0
0.264	155	0.5	43.0
0.235	177	0.7	40.5
0.206	220	0.8	38.0
0.177	240	1.0	35.3
0.147	260	1.1	33.0
0.118	337	1.3	31.0

Table 7 -

dependence on initial sulphite concentration
[ClO3-]0 = 0.290 M, initial pH = 4.5

[SO3-]0/M	tind/s	Final pH	Peak temperature/°C
0.44	128	0.4	45.0
0.409	162	0.4	43.0
0.364	120	0.5	41.0
0.321	110	0.5	39.5

[0064] These data indicate that the induction period is inversely proportional to the initial chlorate ion concentration and effectively independent of the sulphite concentration. The peak temperature rise decreases as the system is diluted. The system is of potential value as a cleaning composition.

Example 5

[0065] A series of experiments were performed in which chlorite ion was added to the bromate-sulphite reaction system to see if the latter could drive the production of ClO₂ after a suitable induction period. The experimental data set out in Table 8 below was collected.

Table 8

[BrO3-]0 /M	[SO32-]0 /M	[S2O52-]0 /M	[ClO2-] 0/M	pH0	tind/ s	Final pH	Peak temp/ °C
0.35	0.56	0.021	0.022	8.05	245	2.15	51
0.35	0.56	0.021	0.055	8.05	221	2.2	51
0.35	0.56	0.021	0.112	8.15	260	2.7	52
0.175	0.28	0.0105	0.0275	7.95	840	2.35	31
0.175	0.28	0.0105	0.0385	8.15	853	2.5	34
0.175	0.28	0.0105	0.055	8.15	690	2.55	33
0.175	0.28	0.0105	0.0825	8.3	865	3.05	35
0.175	0.28	0.0105	0.11	8.45	1005	3.65
0.175	0.28	0.0132	0.11	8.15	630	2.65	38
0.175	0.28	0.0158	0.165	8.1	289	3.2
0.175	0.28	0.0184	0.165	7.6	50	2.7	38
0.156	0.28	0.0132	0.111	7.9	475	2.6	35
0.168	0.28	0.0132	0.111	8.0	348	2.5	35
0.175	0.28	0.0132	0.111	8.15	330	2.65	38
0.186	0.28	0.0132	0.111	8.0	333	2.6	36
0.21	0.28	0.0132	0.111	8.0	300	2.6	36
0.175	0.238	0.0132	0.111	7.9	225	2.6	34
0.175	0.258	0.0132	0.111	7.9	278	2.5	35
0.175	0.278	0.0132	0.111	8.15	330	2.65	35
0.175	0.298	0.0132	0.111	8.0	405	2.6	36
0.175	0.317	0.0132	0.111	8.0	557	2.7	36

[0066] These results indicate that the system is reasonably robust to the addition of chlorite ion. The induction period and pH change is relatively insensitive to the chlorite ion concentration, although very high concentrations can inhibit the reaction.

[0067] From the drop in pH, it can be expected that the ClO₂^- will decompose to ClO₂. This has not been confirmed quantitatively, but the presence of ClO₂ was clearly detectable from its smell after the pH change occurred. Thus the system is of potential value for a cleaning agent having sterilizing properties.

Example 6

[0068] An experiment was carried out to investigate how mixing bromate and sulphite reactants in dry powder form affects induction time, temperature rise and pH. The experiment was carried out for varying sulphite concentration at two initial bromate concentrations (0.4 and 0.6M).

[0069] The reactants were weighed out in dry powder form so that when mixed with 50ml of water they would give the desired concentrations. Effervescence was seen when the water was added. A comparison was made with reactions using liquid reactants. The results are shown in Table 9 below.

[0070] Table 9 above shows how the induction period changes depending on whether the reactants are used in solution or dry powder form. The induction period was increased for the dry powder experiments, but this increase was very small and in most cases only increases the induction time by a few seconds. There was no noticeable difference in the temperature rise and initial and final pH between the dry powder and solution experiments. A powder system was accordingly shown to be of possible value in the present invention.

Example 7

[0071] An experiment was carried out to investigate how using tap water (in the School of Chemistry, University of Leeds, UK) instead of distilled water affects induction period, temperature rise and pH, in a sulphite-bromate system. The experiment was carried out for varying sulphite concentration at two initial bromate concentrations (0.4 and 0.6M) and a constant bisulphite concentration (0.018M). The results are shown in Table 10 below.

[0072] It can be seen from the above results that using tap water instead of distilled water had no significant effect on the induction time with the values staying substantially constant throughout all the experiments. The temperature rise and initial and final pH were also seen to remain substantially constant.

Example 8

[0073] In a bromate-sulphite system the co-addition of surfactants typically used in household cleaning compositions was studied. A set of initial concentrations were chosen (bromate 0.5M, sulphite 0.65M and bisulphite 0.018M) and a selection of surfactants were added, as identified in Table 11 below.

Table 11

Surfactants	tind	Max temp (°C)	Initial pH	Final pH	pH swing
None	190	59.5	8.1	2.9	5.2
sodium lauryl sulphate (0.5g)	252	58.5	8.1	2.9	5.2
sodium lauryl sulphate (0.2g)	211	58.0	8.0	2.9	5.1
Empigen BAC® 50 (1g)	178	59.5	8.4	3.2	5.2
Polytergent® SL-62 (1g)	172	59.5	8.3	3.0	5.3
Dipropylene glycol ether (1g)	182	59.5	8.2	3.0	5.2

[0074] Sodium lauryl sulphate is a well-known anionic surfactant. Polytergent® SL-62 is a non-ionic surfactant, a mixture of ethoxylated and propoxylated fatty alcohols, from BASF. The glycol ether was DOWANOL® DPnB glycol ether. Empigen® BAC 50 is a cationic surfactant, a benzalkonium chloride, more specifically C_10-16 (predominantly C_12-14) alkyl dimethyl benzylammonium chloride.

[0075] It can be seen that with the amounts added none of the surfactants has a large effect on the induction time. It can be seen that sodium lauryl sulphate does increase the induction time slightly whereas the Empigen® BAC 50, Polytergent® S162 and glycol n-butyl ether all slightly decrease the induction time. The temperature rise in all cases stays constant. The initial pH is slightly raised when Empigen® BAC 50, Polytergent® SL-62 and glycol n-butyl ether are added but the pH swing stays almost constant.

Example 9

[0076] A further experiment was carried out to determine in greater detail the effects of adding various surfactants to the bisulphite/sulphite-bromate reaction mixture.

[0077] Two different sets of initial concentrations were used:

i) bromate 0.5M, sulphite 0.65M and bisulphite 0.018M

ii) bromate 0.7M, sulphite 0.5M and bisulphite 0.018M

[0078] A small amount of a common surfactant was added to each experiment in the concentration ranges shown below:

Empigen® BAC 50: 1% w/w - 5%w/w

Sodium lauryl sulfate: 1% w/w - 5%w/w

Polytergent® SL-62: 1% w/w - 10%w/w

Dipropylene glycol n-butyl ether: 1% w/w - 10%w/w

[0079] Tables 12 and 13 show the results from the experiments In each case the results are the mean results of three replicates. Table 12 shows the results for the initial concentrations bromate 0.5M, sulphite 0.65M and bisulphite 0.018M and Table 13 shows the results for the initial concentrations bromate 0.7M, sulphite 0.5M and bisulphite 0.018M.

[0080] The general conclusion that can be drawn from these more detailed experiments is that none of the surfactants affect the reaction very much. The most important observations are that Empigen® BAC 50 seems to decrease the induction time slightly but raises the initial pH by approximately 0.5 units. The initial pH increases with increasing Empigen® BAC 50 concentration up to 8.6 (the pH of Empigen® BAC 50). Sodium lauryl sulphate slightly increases the induction time.

Example 10

[0081] An experiment was conducted to determine whether the dry powder chemicals for the sulphite-bromate system can be stored together and still react when mixed with water

[0082] The experiments were conducted as outlined previously, but over a period of 30 days. "Stirred" and "unstirred" variants were carried out. In the "stirred" variants the reaction mixtures were stirred constantly throughout the reactions. In the "unstirred" variants the reaction mixtures were stirred vigorously for 15 seconds, then left unstirred for the rest of the experiments.

[0083] It was noted that towards the latter stages of the experiments, orange specks were seen in the powder. Also throughout the experiments it was found that the powder set into a solid lump, which needed to be broken up prior to carrying out the experiments. The results are shown in Table 14 below.

Table 14

Day	Stirred					Unstirred
	pHmax	pHmin	ΔpH	tind/10 s	max T/°C	pHmax	pHmin	ΔpH	tind/ 10 s	max T/°C
1	8.05	2.9	5.15	19.4	59	8.1	2.9	5.2	24	61.5
2	8.05	2.85	5.2	26.1	55	8	2.85	5.15	28.8	58
3	8	2.85	5.15	17.9	59	8.05	2.9	5.15	20.2	61.5
4	8.1	2.9	5.2	19.2	59	8.1	2.9	5.2	19.6	62.5
5	8.1	2.9	5.2	18.6	60.5	8.1	2.9	5.2	28.6	61.5
6	8.05	2.9	5.15	19.3	59	8.1	2.9	5.2	20	60.5
7	8.15	2.95	5.2	21.8	56	8.15	2.95	5.2	35.2	58
8	8.1	2.9	5.2	20.3	56	8.1	2.95	5.15	22.3	58.5
10	8.15	2.95	5.2	23.2	53.5	8.05	2.9	5.15	28.4	56
12	8.15	2.95	5.2	24.7	52	8.1	2.95	5.15	28.7	54.5
14	8.15	2.95	5.2	23	53	8.1	2.95	5.15	26.2	55
16	8.1	2.9	5.2	23.5	52.5	8.05	2.9	5.15	24.3	57
19	8.05	2.9	5.15	24	51	8.1	2.9	5.2	38.6	54
22	8.15	2.95	5.2	22.5	52	8.1	2.9	5.2	35	52
26	8.1	2.9	5.2	21.3	52	8.1	2.95	5.15	33.9	52
30	8.15	2.9	5.25	21.4	55

[0084] It can be seen from Table 14 that in both the stirred and unstirred experiments the initial and final pH stayed almost constant with an initial pH of approximately 8.1 and a final pH of approximately 2.9. The maximum temperature rise also stayed approximately constant at 55°C. The average induction time of the stirred experiments was 216 ± 23.8s but can be seen to vary in the range of 179 - 261s. The induction time in the unstirred case had an average time of 276 ± 60s but with times varying from 196 - 386s.

Example 11

[0085] Experiments were carried out to investigate a hydrogen peroxide-sulphite/bisulphite system for suitability for use in the present invention. To deliver hydrogen peroxide in a stable manner urea hydrogen peroxide (UHP) CO(NH₂)₂H₂O₂ was used. Sodium sulphite was used in the concentration range 1 x 10^-3M to 5 x 10^-3M. UHP was used in the concentration range 1 x 10^-2M to 5 x 10^-2M. The experiments showed that induction period for a pH change event could be 80-2000 seconds, with the lower induction periods being promoted by the more concentrated UHP solutions. pH typically swung from an initial pH of 7.5-8.4 (higher with increasing sulphite concentration) to a final pH of 5.1, with UHP concentration having no effect on initial or final pH, and sulphite concentration having no effect on final pH. It was concluded that the system had promise as the basis for a cleaning composition.

Example 12

[0086] The compatibility of the UHP-sulphite system described in Example 11 with a number of surfactants was also investigated. The following surfactants were tested.

Empigen BAC 50: 1% w/w - 5%w/w

Sodium lauryl sulfate: 1% w/w - 5%w/w

Polytergent SL-62: 1% w/w - 10%w/w

Dipropylene glycol n-butyl ether: 1% w/w - 10%w/w

[0087] The reactants and their initial concentrations were as follows.

UHP	0.3M
Sulphite	0.01887M
Bisulphite	0.00113M

[0088] The results are set out in Figures 1 to 4. In these figures the leftmost bar of each block of results was a control (0% w/w surfactant) and the rightmost bar of each block of results denotes the highest concentration of surfactant employed.

[0089] The main conclusions are:

• All the surfactants reduced the initial pH by 0.1 - 0.2 units
• Dipropylene glycol n-butyl ether reduced the final pH. All the other surfactants increased the final pH.
• All surfactants decreased the induction period. In the case of Empigen® BAC 50, the decrease was significant, lowering the induction time by up to a minute at its lowest concentration. Dipropylene glycol n-butyl ether decreased the induction period the least, but still managed to decrease it by 30 seconds at its lowest concentration.

Example 13

[0090] The following samples were tested for antimicrobial properties.

Sample 1	Sodium bromate (NaBrO3) - [0.7M] Sodium sulphite (NaSO3) - [0.5M] Sodium bisulphite (NaS2O5) - [0.025M]
Sample 2	As Sample 1, but sodium bisulphite concentration 0.018M

[0091] In the first tests against S.aureus and E.coli, testing was undertaken (with Sample 1) using sterile purified water and in the absence of any organic soil. The second tests (with Sample 2) included two additional test organisms (P.aeruginosa and E.hirae), and were undertaken in hard water (300 ppm CaCO₃) and with the addition of organic soil, bovine serum albumin - BSA.

[0092] The test method for Sample 2 was as follows: 1ml bacterial suspension (10⁷ cfu/ml) of the selected bacterium was transferred to a flask containing 1ml of a 3% BSA suspension. The culture/ soil mix was vortex mixed and then shaken on an orbital shaker for 2 minutes. To the culture/ soil mix was added 8ml sterile hard water. Mixing was continued for another minute. Without interruption of the shaking, the chemical compounds of the appropriate samples were added to the flask in powder form, in amounts calculated to give the molarities mentioned above. 5 minutes after addition of the sample, shaking was stopped and a 1ml aliquot of the test mixture was transferred to 9.0ml neutralising medium. After a neutralisation period of 5 minutes, the sample was serially diluted and used to prepare pour plates which were subsequently incubated at 36°C for 48 hours before enumerating surviving bacteria. As an inactive control, testing was repeated without the addition of the test sample. The test method for Sample 1 was similar but as noted above did not employ hard water or BSA.

[0093] Microbiocidal Effect (ME) values were calculated as follows:
log (cfu/ml in test at t=0) - log (cfu/ml recoverable from test after 5 minute contact time). The results are shown in Tables 15 and 16 below.

Table 15.

Median ME values (n=3), for S.aureus and E.coli in preliminary tests
Test organism	Median ME values
	(Sample 1)	Water (control)
S.aureus	>5.7	0.1
E.coli	>5.4	0.1

Table 16.

Median ME values (n=3) from further testing
Test organism	Median ME values
S.aureus	5.3
E.coli	5.4
P.aeruginosa	>5.2

[0094] On the basis of these preliminary results, it appears that exposure of bacteria to the reactants in a standard suspension test produces considerable reductions in bacterial viability. Reductions in excess of log 5.0 were achieved for all four test organisms in the presence of the organic soil bovine serum albumin and hard water, and with a 5-minute contact time.

[0095] Accordingly, it was concluded that the system showed good activity as an antimicrobial cleaning composition.

Example 14

[0096] Experiments were carried out on a system postulated to cause an increase in pH, employing urea hydrogen peroxide and Fe(CN)₆^4-.

[0097] The experiments assessed the effect of concentration of the species above and of hydrogen ion concentration.

[0098] Tables 17-19 summarise the results of the experiments. In each case two species were kept at constant concentrations whilst the third was varied.

[0099] When not being varied, the initial species concentrations were:

• UHP = 2 x 10^-3 M
• Ferrocyanide = 2 x 10^-3 M
• H+ = 5 x 10^-4 M
  
  
  
  
  
  

[0100] No temperature rise was observed during any of the experiments. A colour change of colourless to pale yellow was observed. The mean pH increase varied between 3.5 and 4.9 and was often 4.4.

Example 15

[0101] A hard surface cleaning composition has the following composition.

TERGITOL® secondary alcohol	0.6% w/w
ethoxylate
Ethylene glycol-n-butyl ether
(non-ionic surfactant)
Fragrance	0.2% w/w
Colour	trace
H2O2	0.1% w/w
Na2S2O3	0.16% w/w
Na2SO3	0.05% w/w
H2SO4	0.005% w/w
Liquified petroleum gas (propellant)	20% w/w
Deionised water	to 100% w/w

[0102] During preparation the hydrogen peroxide was kept separate from a solution of the three sulfur-containing compounds. These input solutions were kept free of air before mixing and were mixed in the absence of air, and bottled in aerosol cans, free of air. Only on spraying a surface with this composition, for cleaning, does the pH step reaction start.

Example 16

[0103] A hard surface cleaner has the following composition:

Ethoxylated fatty alcohol (C12-14;3EO)	1% w/w
(non-ionic surfactant)
Ethylene glycol	5% w/w
Fragrance	0.1% w/w
Colour	trace
NaIO4	0.43% w/w
Na2S2O3	0.16% w/w
Na2SO3	0.06% w/w
H2SO4	0.01% w/w
Butane (propellant)	18% w/w
Deionised water	to 100% w/w

[0104] The components were mixed and loaded into spray canisters with exclusion of air. Only on spraying a surface with this composition, for cleaning, does the pH step reaction start.

Claims

1. A method of cleaning a hard surface which is subject to deposition by limescale, the method comprising the application to the hard surface of a cleaning composition which comprises reactants which undergo a chemical reaction after exposure to the hard surface to be cleaned, the reaction being such as to produce a delayed change of pH at the hard surface, the composition being initially an alkaline liquid and after an interval becoming an acidic liquid effective in combating limescale.

2. A method as claimed in claim 1, wherein the composition has the property that after exposure to the hard surface the composition produces a delayed change of pH at the hard surface of at least 2 pH units .

3. A method as claimed in claim 1 or 2, wherein the composition comprises an oxidant selected from a peroxy compound, and an oxidising metal compound stable in alkaline solutions; and a reductant selected from an oxyanion or sulfur that contains S-S bonds, and a compound substantially more basic than its oxidised counterpart.

4. A method as claimed in claim 3, wherein the oxidant is selected from the species BrO₃^-, IO₃^-, ClO₃^-, ClO₂^-, S₂O₈^2-, ClO₂, [Fe(CN)₆]^3- and H₂O₂ or a precursor thereto, and the reductant is selected from the species S₂O₃^2-, S₄O₆^2-, S₂O₄^2-, S₂O₆^2-, SO₃^2- and N₂H₅⁺, the oxidant and the reductant together participating in reactions producing pH oscillations.

5. A method as claimed in any preceding claim, wherein the composition produces an antimicrobial effect at the hard surface.

6. A method as claimed in any preceding claim, wherein the composition produces a bleaching effect at the hard surface.

7. A method as claimed in any preceding claim, wherein a temperature rise is generated by the reactants at the hard surface.

8. A method as claimed in any preceding claim, the composition being such that the pH change is evidenced by a change in colour or fragrance, or by effervescence.

9. A method as claimed in any preceding claim, comprising a surfactant.

10. A method as claimed in any preceding claim, wherein the composition is packaged with exclusion of oxygen and/or water and/or carbon dioxide and/or light, as required to prevent a pH change prior to exposure to use.

11. A method as claimed in any preceding claim, wherein the hard surface is in an aqueous environment and the method comprises dilution of the cleaning composition into the aqueous environment.

Ansprüche

1. Verfahren zur Reinigung einer harten Oberfläche, auf welcher sich Kalk ablagert, wobei das Verfahren das Aufbringen einer Reinigungszusammensetzung, die Reaktanten umfasst, die sich nach Einwirkung auf die harte Oberfläche einer chemischen Reaktion unterziehen, auf die harte Oberfläche umfasst, wobei die Reaktion derart ist, dass eine verzögerte Änderung des pH-Werts auf der harten Oberfläche erzeugt wird, indem die Zusammensetzung anfänglich eine alkalische Flüssigkeit ist und nach einem Zeitraum zu einer beim Bekämpfen von Kalk wirksamen sauren Flüssigkeit wird.

2. Verfahren nach Anspruch 1, wobei die Zusammensetzung die Eigenschaft aufweist, dass die Zusammensetzung nach Einwirkung auf die harte Oberfläche eine verzögerte Änderung des pH-Werts von mindestens 2 pH-Einheiten auf der harten Oberfläche erzeugt.

3. Verfahren nach Anspruch 1 oder 2, wobei die Zusammensetzung ein Oxidationsmittel, ausgewählt aus einer Peroxyverbindung und einer in alkalischen Lösungen stabilen oxidierenden Metallverbindung, und ein Reduktionsmittel, ausgewählt aus einem Oxyanion oder S-S-Bindungen enthaltendem Schwefel und einer Verbindung, die im Wesentlichen basischer als ihr oxidierter Gegenpart ist, umfasst.

4. Verfahren nach Anspruch 3, wobei das Oxidationsmittel ausgewählt ist aus der Spezies BrO₃^- IO₃^-, ClO₃^-, ClO₂^-, S₂O₈^2-, ClO₂, [Fe(CN)₆]^3- und H₂O₂ oder einer Vorstufe dazu, und das Reduktionsmittel ausgewählt ist aus der Spezies S₂O₃^2-, S₄O₆^2-, S₂O₆^2-, SO₃^2- und N₂H₅⁺, wobei das Oxidationsmittel und das Reduktionsmittel gemeinsam an pH-Schwankungen erzeugenden Reaktionen teilnehmen.

5. Verfahren nach einem der vorangehenden Ansprüche, wobei die Zusammensetzung eine antimikrobielle Wirkung auf der harten Oberfläche erzeugt.

6. Verfahren nach einem der vorangehenden Ansprüche, wobei die Zusammensetzung eine Bleichwirkung auf der harten Oberfläche erzeugt.

7. Verfahren nach einem der vorangehenden Ansprüche, wobei eine Temperaturerhöhung durch die Reaktanten auf der harten Oberfläche erzeugt wird.

8. Verfahren nach einem der vorangehenden Ansprüche, wobei die Zusammensetzung derart ist, dass sich die pH-Änderung durch eine Farb- oder Geruchsänderung oder durch Sprudeln zeigt.

9. Verfahren nach einem der vorangehenden Ansprüche, umfassend ein oberflächenaktives Mittel.

10. Verfahren nach einem der vorangehenden Ansprüche, wobei die Zusammensetzung unter Ausschluss von Sauerstoff und/oder Wasser und/oder Kohlendioxid und/oder Licht verpackt wird, wie es zum Verhindern einer pH-Änderung vor der Verwendungseinwirkung erforderlich ist.

11. Verfahren nach einem der vorangehenden Ansprüche, wobei die harte Oberfläche eine wässrige Umgebung ist und das Verfahren die Verdünnung der Reinigungszusammensetzung in der wässrigen Umgebung umfasst.

Revendications

1. Procédé de nettoyage d'une surface dure qui est soumise à un dépôt de tartre, ledit procédé comprenant l'application sur la surface dure d'une composition de nettoyage qui comprend des réactifs qui subissent une réaction chimique après une exposition à la surface dure à nettoyer, la réaction étant telle qu'elle produit un changement retardé du pH sur la surface dure, la composition étant initialement un liquide alcalin et, après un laps de temps, devenant un liquide acide efficace pour combattre le tartre.

2. Procédé selon la revendication 1, dans lequel la composition a la propriété que, après une exposition à la surface dure, la composition produit un changement retardé du pH sur la surface dure d'au moins 2 unités de pH.

3. Procédé selon la revendication 1 ou 2, dans lequel la composition comprend un oxydant choisi parmi un composé peroxy et un composé métallique oxydant stable dans des solutions alcalines ; et un agent réducteur choisi parmi un oxyanion ou du soufre qui contient des liaisons S-S, et un composé sensiblement plus basique que son équivalent oxydé.

4. Procédé selon la revendication 3, dans lequel l'oxydant est choisi parmi les espèces BrO₃^-, IO₃^-, ClO₃^-, ClO₂^-, S₂O₈^2-, ClO₂, [Fe (CN)₆]^3- et H₂O₂ ou un précurseur de celles-ci, et l'agent réducteur est choisi parmi les espèces S₂O₃^2-, S₄O₆^2-, S₂O₄^2-, S₂O₆^2-, SO₃^2- et N₂H₅⁺, l'oxydant et l'agent réducteur participant ensemble à des réactions produisant des oscillations du pH.

5. Procédé selon l'une quelconque des revendications précédentes, dans lequel la composition produit un effet antimicrobien sur la surface dure.

6. Procédé selon l'une quelconque des revendications précédentes, dans lequel la composition produit un effet de blanchiment sur la surface dure.

7. Procédé selon l'une quelconque des revendications précédentes, dans lequel une augmentation de la température est générée par les réactifs au niveau de la surface dure.

8. Procédé selon l'une quelconque des revendications précédentes, la composition étant telle que le changement de pH est démontré par un changement de couleur ou de fragrance ou par effervescence.

9. Procédé selon l'une quelconque des revendications précédentes, comprenant un agent tensioactif.

10. Procédé selon l'une quelconque des revendications précédentes, dans lequel la composition est emballée avec exclusion d'oxygène et/ou d'eau et/ou de dioxyde de carbone et/ou de lumière, ainsi que cela est requis pour empêcher un changement de pH avant exposition lors de l'utilisation.

11. Procédé selon l'une quelconque des revendications précédentes, dans lequel la surface dure est dans un environnement aqueux et le procédé comprend la dilution de la composition de nettoyage dans l'environnement aqueux.

Drawing