EP1874913B1

EP1874913B1 - Aqueous liquid bleach compositions

Info

Publication number: EP1874913B1
Application number: EP06704593A
Authority: EP
Inventors: Joanne C. Unilever R & D Port Sunlight O'KEEFFE; Philip M. Unilever R & D Port Sunlight RYAN; Katherine M. Unilever R & D Port Sunlight THOMPSON; David William Unilever R & D Port Sunlight THORNTHWAITE
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2005-02-16
Filing date: 2006-01-31
Publication date: 2008-07-23
Anticipated expiration: 2026-01-31
Also published as: AU2006215837B2; PL1874913T3; ES2311274T3; EP1874913A1; JP2008530320A; MX2007009846A; SI1874913T1; CA2597805C; AU2006215837A1; WO2006087099A1; RU2394880C2; CA2597805A1; ATE402247T1; BRPI0607200A2; CN101120078B; RU2007134397A; CN101120078A; DE602006001952D1; AR052373A1; BRPI0607200B1

Description

Technical field

The present invention relates to aqueous thickened liquid bleach and disinfectant compositions comprising hypochlorite, quaternary ammonium halogenide surfactant and a thickening system. The invention also relates to the use of such compositions for cleaning and disinfecting hard surfaces.

Background and prior art

Aqueous liquid hypochlorite bleach compositions are well known in the art. On the one hand they are used for bleaching and stain removal on laundry, on the other hand they are used for cleaning and disinfecting hard surfaces such as kitchen surfaces, floors and in particular toilets. To increase contact time between the surface and the bleach, on inclined and vertical surfaces bleach compositions intended for cleaning hard surfaces preferably have a relatively high viscosity and such compositions are generally known as "thick bleach".
Various thickening systems for hypochlorite have been described in the prior art involving a large variety of combinations of surfactants. Among these GB 1,466,560 describes thickening systems comprising an alkali metal sarcosinate or tauride surfactant and another surfactant chosen from amine oxides, quaternary ammonium compounds, betaines, alkanolamides and fatty acid soaps. From this latter list only combinations involving an amine oxide or a soap are exemplified. EP 298172 , US 5,055,219 and US 5,336,426 all disclose thickening mixtures comprising a quaternary ammonium compound and an organic counter ion which may be a C₁-C₁₀ alkyl or aromatic sulphonate or sulphate or aliphatic or aromatic carboxylate.
Although active chlorine compounds, and particularly hypochlorite, are known to be powerful disinfectants for hard surfaces, this disinfectant activity is short-lived, i.e. after a surface has been treated with an active chlorine compound it can quickly become microbially recontaminated again. This is particularly true if the surface is rinsed with water after the treatment, because this washes away any traces of active chlorine compound left on the surface.
In US 2,987,435 it is disclosed that quaternary ammonium salts are effective antimicrobial compounds. Treating a surface with a combination of hypochlorite and a quaternary ammonium salt leaves antimicrobial activity on the surface even after rinsing with water. The compositions typically contain 0.5-1% active chlorine. More concentrated compositions were said to lead to phase separation such as emulsions or precipitates. The compositions are particularly suitable for treating textiles and fibres and are therefore preferably thin liquids.
EP 844827 discloses that aqueous compositions comprising up to 0.25% active chlorine compound and up to 0.08% bactericidal quaternary ammonium compound are able to kill tubercule bacilli on hard surfaces. Preferred quaternary ammonium compounds are the di(C8-C12)alkyl-dimethylammonium salts and the (C12-C18)alkyl-dimethyl-benzylammonium salts Didecyl-dimethylammonium chloride and (C12-C16)alkyl-dimethyl-benzylammonium chloride are specifically mentioned. It is said to be advisable to keep the active chlorine solution and the quaternary ammonium salt solution separate until the moment of use to prevent the active chlorine solution to lose part of its active chlorine content.
Indeed it has been found by experimentation that in the long term most quaternary ammonium compounds are not stable in hypochlorite solution and that such solutions after weeks of storage tend to lose a significant part of the active chlorine as well as of the quaternary ammonium content. In those cases where the quaternary ammonium compounds were stable many were found to adversely interfere with the thickening system of the hypochlorite bleach, leading in many cases to unacceptable loss of viscosity and in some cases to excessive thickening causing the formation of thick gels which were impossible to be dispensed by pouring.
Desirable methods for oxidative cleaning/bleaching of any surface should provide powerful initial disinfectancy as well as give sufficient residual antimicrobial activity on a surface to prevent bacterial regrowth for extended periods of time, also after rinsing with water. Compositions suitable for use in such methods should be sufficiently stable to be manufactured, shipped and stored, on the shelf as well as by the consumer, without appreciable loss of active chlorine. Furthermore such compositions should have a suitable viscosity to cling on inclined or vertical surfaces, such as found in toilets and bathrooms and yet be able to be dispensed easily.

Summary of the invention

It has now been found that treatment of surfaces with a liquid composition comprising a combination of hypochlorite and one or more specific quaternary ammonium chlorides provides thorough oxidative cleaning and removal of stains while at the same time not only disinfecting the surface, but providing antimicrobial activity on the cleaned surface for an extended period of time. By selecting specific quaternary ammonium salts compositions are provided that can be stored for long periods of time without appreciable loss of active chlorine or quaternary ammonium compound and that have the suitable viscosity to be used as "thick bleach".
Thus, the invention provides thick liquid hypochlorite bleach compositions comprising one or more inorganic quaternary ammonium salts and a suitable thickening system comprising amine oxide surfactant and fatty acid.
Furthermore, the invention provides a method of cleaning and disinfecting hard surfaces, particularly inclined or vertical surfaces such as found in toilets and bathrooms comprising applying to the surface a liquid bleaching composition comprising hypochlorite and one or more specific quaternary ammonium halides and a thickening system comprising amine oxide surfactant and fatty acid.

Detailed description of the invention

All percentages mentioned herein are by weight based on the total composition, unless specified otherwise.
Accordingly, the invention provides aqueous liquid bleaching compositions comprising a hypochlorite salt and a quaternary ammonium salt characterised in that the ammonium salt has the general formula: R₁R₂R₃R₄N⁺ X^-, wherein R₁ is a C₁₂-C₁₈ alkyl group, each of R₂, R₃ and R₄ independently is a C₁-C₃ alkyl group and X is an inorganic anion and the composition comprises a thickening system comprised of amine oxide surfactant and fatty acid.
The hypochlorite salt is generally an alkali metal or alkaline earth metal salt although other salts may be used. The Na and Ca salts are most widely used. The compositions used for the purposes of the invention generally comprise 0.01-10% NaClO or an equivalent amount of other hypochlorite salt, which is equivalent to about 0.0095-9.5% available chlorine and to 0.0014-1.4 mol/l of hypochlorite ion. Preferably the hypochlorite ion content is 0.005-1.0 mol/l, more preferably at least 0.01 mol/l, most preferably at least 0.05 mol/l or even 0.1 mol/l.
In the quaternary ammonium salts according to the present invention R₁ is preferably a C₁₄-C₁₆ straight chain alkyl group, more preferably C₁₆. R₂-R₄ are preferably methyl groups. The inorganic anion is preferably chosen from halide, sulphate, bisulphate or OH^-. Thus, for the purposes of this invention, a quaternary ammonium hydroxide is considered to be a quaternary ammonium salt. More preferably the anion is a halide ion or sulphate, most preferably a chloride or sulphate. Cetyl-trimethylammonium chloride is a specific example of a suitable compound and commercially abundantly available.
In general the quaternary ammonium salts suitable for the invention are preferably stable enough to hypochlorite to have at least 60% of the original amount of available chlorine left after 4 weeks storage at 20°C, i.e. 2.9 wt% available chlorine starting from 4.8%wt in the fresh composition (Example formulation 1 below). More preferably at least 70% of the original amount available chlorine is left after the 4 weeks storage test.
The compositions according to, and used in the methods of the invention generally comprise 0.001-0.5 mol/l of the quaternary ammonium ion, preferably 0.005-0.1 mol/l, more preferably at least 0.01 mol/l. The molar ratio between hypochlorite ion and quaternary ammonium ion is usefully kept between 500:1 and 1:1, preferably between 200:1 and 2:1. Even more useful ratios are at or below 100:1. The halide ion is preferably chloride or bromide, more preferably chloride.
Suitable amine oxide surfactants for use in the thickening system are tertiary amine oxides of structure RRRNO, where one R is an alkyl group of 8 to 20 carbon atoms and the other R's are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms, preferably methyl groups. The large alkyl group preferably has at least 12, more preferably at least 14 carbon atoms. The amine oxide is preferably used in an amount of at least 0.02%, more preferably at least 0.05%, most preferably 0.1 or even 0.5%, but preferably not above 10%, more preferably 5%. Fatty acids are aliphatic carboxylic acids and suitable fatty acids have 8-20 carbon atoms, preferably in a straight chain. Preferred acids are those having a C₁₀-C₁₈ alkyl group, more preferred those having an alkyl group of at least 11 C-atoms. The fatty acids are preferably used in an amount of at least 0.05%, more preferably 0.1%, but preferably not above 5%, more preferably 2%.
For long-term stability the compositions used for the purposes of the invention need to be alkaline, i.e. have pH above 7. Preferably the pH is kept at or above 8, more preferably at least 9 or even 10.
The compositions according to the invention are particularly suitable to be used as is, i.e. without prior dilution. In order to be conveniently dispensed from suitable containers whilst also clinging to inclined surfaces they preferably have a viscosity of 20-5000mPa.s, preferably 100-2000 mPa.s, more preferably 200-1000 mPa.s (measured with a Haake RT20 Rotovisco rheometer fitted with a coaxial cylinder sensor DIN 53018 (Z41 rotor and Z43 measuring cylinder), using a 3 mm gap. Flow curves were obtained at 25° C over the shear rate range 0.1 to 1000 s^-1).
Whilst the pure compositions may not be suitable to come into contact with the human skin on account of their high content of hypochlorite, they can be applied to a surface manually (e.g. with a wipe or cloth or other implement) after proper dilution. Suitable dilution factors are generally between 1:5 and 1:500
As outlined above, compositions according to the invention, either dilute, but preferably pure are applied to the surface to be treated and are left in contact with that surface for a sufficiently long time to oxidatively clean and disinfect that surface, whereafter the surface may be rinsed if desired. Generally, contact times of 1 minute are sufficient for initial disinfectancy, with contact times of at least 5 minutes being used to obtain long term disinfectancy, preferably at least 15 minutes, more preferably at least 30 minutes. One example of such embodiment involves applying a composition according to the invention with a spraying device such as a trigger spray or similar as well known in the art of hard surface cleaning. Another embodiment of the invention involves applying a squirt of the product according to the invention straight from the container in which it is provided to the surface to be treated.
The invention particularly provides a method for cleaning and disinfecting toilet surfaces comprising applying to the surface a composition as described above. In a preferred embodiment, wherein the toilet surface to be treated is the toilet bowl, a composition as described above is applied directly from the container to the bowl, either above the water table to the surface of the bowl e.g. under the rim, or to the water in the bowl. Particularly suitable containers for that purpose are well known in the art. Typically for such containers the longitudinal axis of the dispensing opening in the cap makes an angle of generally less than 90° (preferably 10-80°) with the longitudinal axis of the bottle to enable easy application of the composition under the rim of the toilet bowl. An example of such a bottle is depicted in the UK Industrial Design registration no. 1057823 . Applying the concentrated composition to the water in the bowl will generate a diluted solution according to the invention.
As outlined above, treating a surface with a bleaching composition according to the invention will not only oxidatively clean and disinfect that surface, but also provides extended antimicrobial activity on that surface such that regrowth of micro-organisms is prevented for many hours after the treatment is completed, particularly if the composition is left to dry out on the surface. The antimicrobial activity remains after rinsing, even repeated rinsing, of the surface, in spite of the fact that the hypochlorite and quaternary ammonium salt in the composition are soluble in water and would be expected to be rinsed away.
The compositions according to the invention can optionally contain many other components known in the art to be useful in bleach compositions. The high viscosity cause the composition to slowly flow down the surface, thus providing prolonged contact time between the composition and the surface leading to improved cleaning and disinfection, and without any manual intervention.
Other optional components include builders, antioxidants, radical scavengers, chelating agents for metals prone to induce or accelerate hypochlorite decomposition such as silicates or periodates, hydrotropes, anticorrosion agents. Solid abrasives may be added as well.
Further hypochlorite stable surfactants may be added to improve cleaning properties, provided they do not adversely affect the properties of the thickening system.
Colorants, dyes and pigments may be added to impart a desired colour to the compositions and perfumes to give the compositions a desired odour, particularly to overcome the hypochlorite odour which many people do not appreciate. The components should chosen to be bleach-stable, as is well known in the art.
As outlined above, the compositions according to the invention are alkaline and sufficient alkali, preferably alkalimetal hydroxide, should be present to ensure this. The compositions could also usefully contain buffer to ensure long term pH stability. Alkali metal carbonates/bicarbonates and silicates are particularly useful for that purpose.

Examples

Aqueous liquid bleaching compositions were prepared according to the formulations 1-4 in Table 1 below (amounts in %) :

Table 1

	1	2	3	4
Na hypochlorite	4.80	4.80	4.80	4.80
Cetyl-trimethylamm. chloride	0.50	0.50	1.00	1.00
Empigen OD *	1.25	0.75	0.75	0.75
Lauric acid	0.30	0.30	0.20	0.10
Perfume	0.06	0.06	0.06	0.06
Alkaline Na silicate	0.05	0.05	0.05	0.05
Viscosity, mPas (at 1-3 s^-1)	455	545	800	170
Viscosity, mPas (at 21 s^-1)	360	390	480	140

All examples sufficient NaOH to pH 12.5. All examples demin water to 100%
*) C₁₀-C₁₈ alkyl-dimethylamine oxide marketed by Huntsman

Viscosity measurements

Formulation viscosities were measured using a Haake RT20 Rotovisco rheometer fitted with a coaxial cylinder sensor DIN 53018 (Z41 rotor and Z43 measuring cylinder), using a 3 mm gap. Flow curves were obtained at 25° C over the shear rate range 0.1 to 1000 s^-1.

Comparative tests:

The viscosity appearance, long lasting hygiene score and hypochlorite stability of Formulation 1 above and of compositions comprising hypochlorite and various other quaternary ammonium salts was determined and the results are presented below in Table 2. For the quaternary ammonium salts 0.5% of each compound was added instead of cetyl-trimethyl-ammonium chloride to a formulation according to Formulation 1.

Viscosity was measured and appearance assessed immediately after preparation and after 1 week storage at ambient temperature.
The absolute residual hypochlorite content was determined after 1 and 4 weeks in the dark at ambient temperature. The results are presented in Table 2 below.

Table 2

Quaternary ammonium salt	Appearance after prep.	Appearance after 1 week	*Hyg. score:**	Av.Cl 1 wk **	Av.Cl 4 wks **
Cetyl-trimethyl-amm. Cl	Standard viscosity	Standard viscosity	15		4.1
Cetyl-trimethyl-amm. Br	Increased viscosity	Increased viscosity	11	3.8	2.7
Tetradecyl-trimethyl-amm. Cl	Increased viscosity	Increased viscosity	5		3,5
Dodecyl-pyridinium Cl	Reduced viscosity	Very low viscosity	0	1.9	0.7
Cetyl-pyridinium Cl	Increased viscosity granular gel	Very low viscosity, particle separation	0	1.9	0.5
Benzalkonium Cl	Reduced viscosity	Very low viscosity	15	3.9	2.9
Tetrabutyl-amm. Cl	Very low viscosity	Very low viscosity	13	0.4	-
Tetraheptyl-amm. Cl	Very low viscosity	Very low viscosity, particle separation	15	3.7	3.3
1,3-Decyl-2-methyl-imidazolium Cl	Very low viscosity	Very low viscosity	11	1,6	0.8
1-Hexadecyl-3-methyl-imidazolium Cl	Increased viscosity	Very low viscosity Particle separation	0	1.9	0.3
Didecyl-dimethyl-amm. Br	Very low viscosity	Very low viscosity	13	3.6	2.9
Didecyl-dimethyl-amm. Cl	Reduced viscosity	Very low viscosity separation	15	3,5	2,4

* Hygiene score expressed as the number of rinses that a microtitre plate well remained bacteria-free.
** Expressed as available chlorine in wt% after 1 and 4 weeks storage at 20°C respectively, starting from 4.8% Na hypochlorite.

Chlorine determination

The residual available chlorine present was analysed iodometrically, using the following procedure: A known weight of the test solution (w) was placed in an iodine flask. The sample was diluted with approximately 20 ml distilled water. 10 g of 5% potassium iodide solution was added followed by 10 ml of 0.5 M sulphuric acid. The flask was stoppered and swirled to mix the contents before placing in dark for 5 minutes, until the brown colour of the evolved iodine had fully developed. The liberated iodine was titrated against 0.1 M sodium thiosulphate solution until the solution becomes colourless, with additional of soluble starch indicator near the end point to aid accuracy.

Hygiene score test

The test uses a high throughput screening method to assess the hygienic properties of standard samples of 10µl of product dispensed in microtitre plate wells that have been left to dry (at 30°C overnight) and are thereafter subjected to a number of automatic rinses. Each test is done in 8 replicates. The rinses were done with a Ascent Wellwash^™ plate washer with sterile water of standard hardness. After a set number of rinses the plates were dried at 30°C for 45 minutes and left to cool at 20°C for 15 minutes. Each well was thereafter incubated with 50µl of an aqueous suspension of E. coli (0.5x10⁸ cfu) in 0.3% protein (BSA) soil and left in contact for 1h at 20°C. The wells were then washed by adding 100µl water of standard hardness and shaking for 10sec., whereafter the wash liquour and unattached cells were aspirated off.
Thereafter 270µl of tryptone soya broth growth medium is placed in each well and the plates are incubated for 24h at 37°C to allow remaining bacteria to re-grow. A test is classified as successful after the set number of rinses if at least 80% of the samples show no regrowth. The highest number of rinses that lead to a successful test is taken as the hygiene score.

Claims

Aqueous liquid bleaching compositions comprising a hypochlorite salt and a quaternary ammonium salt characterised in that the ammonium salt has the general formula: R₁R₂R₃R₄N⁺ X^-, wherein R₁ is a C₁₀-C₂₀ alkyl group, each of R₂, R₃ and R₄ independently is a C₁-C₃ alkyl group and X is an inorganic anion and the composition comprises a thickening system comprised of amine oxide surfactant and fatty acid.
Aqueous liquid bleaching compositions according to claim 1 characterized in that they comprise at least 0.01 mol/l hypochlorite ion.
Aqueous liquid bleaching compositions according to claims 1 or 2 characterized in that R₁ is a C₁₄-C₁₆ straight chain alkyl group and R₂-R₄ are methyl groups.
Aqueous liquid bleaching compositions according to claims 1-3 characterized in that they comprise 0.001-0.5 mol/l quaternary ammonium ion.
Aqueous liquid bleaching compositions according to claim 4 characterised in that they comprise at least 0.01 mol/l quaternary ammonium ion.
Aqueous liquid bleaching compositions according to claims 1-5 characterized in that the molar ratio of hypochlorite ion to quaternary ammonium ion is between 500:1 and 1:1
Aqueous liquid bleaching compositions according to claim 6 characterized in that the molar ratio of hypochlorite ion to quaternary ammonium ion is at or below 100:1.
Aqueous liquid bleaching compositions according to any one of claims 1-7 characterized in that the quaternary ammonium salt is a halide.
Aqueous liquid bleaching compositions according to claims 1-8 characterized in that the amine oxide surfactant is an tertiary amine oxide of structure RRRN0, where one R is an alkyl group of 8 to 20 carbon atoms and the other R's are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms and the fatty acid has 8-20 carbon atoms.
Aqueous liquid bleaching compositions according to claim 9 characterized in that they comprise 0.05-10% amine oxide and 0.05-5% fatty acid.
Aqueous liquid bleaching compositions according to claims 1-10 characterized in that they have a viscosity of 20-5000 mPa.s.
A method for providing lasting antimicrobial activity on a hard surface comprising treating that hard surface with a composition according to any one of claims 1-11.
A method according to claim 12 characterized in that the surface is thereafter rinsed with water.
A method according to claim 12 characterized in that the surface is a toilet surface.
A method according to claim 13 characterized in that the toilet surface is the surface of the toilet bowl.
A container comprising a bottle and a cap with a dispensing opening, and a bleaching composition contained in the container, characterized in that the longitudinal axis of the dispensing opening makes an angle of less than 90° with the longitudinal axis of the bottle and the bleaching composition inside the container is a composition according to claims 1-11.