EP0079697B2

EP0079697B2 - Cleaning compositions

Info

Publication number: EP0079697B2
Application number: EP82305666A
Authority: EP
Inventors: Anthony Francis Martin
Original assignee: Procter and Gamble Ltd; Procter and Gamble Co
Current assignee: Procter and Gamble Ltd; Procter and Gamble Co
Priority date: 1981-11-07
Filing date: 1982-10-26
Publication date: 1990-03-14
Anticipated expiration: 2002-10-26
Also published as: EP0079697B1; ATE17595T1; DE3268705D1; EP0079697A1; CA1202853A

Abstract

Aqueous cleaning compositions of viscosity > 180 centipoises at 20 DEG C are provided containing a trialkyl amine oxide of formula R1R2R3N->O, where 13 < R1 </= 18 and R2 and R3 are C1-C4 alkyl, as the sole surfactant at a level of 0.5% to 5.0% by weight of the composition. The compositions also incorporate one or more ionisable water soluble compounds to provide an ionic strength of 3.0 g mole/dm<3> minimum, and in preferred embodiments this is provided by an alkali metal hypochlorite bleach component.

Description

. This invention relates to aqueous cleaning compositions and especially to chlorine bleach-containing aqueous cleaning compositions useful for the removal of oxidisable stains from and the disinfection of hard surfaces. Compositions in accordance with the invention find particular utility in the cleaning of sanitary fittings such as toilets, bidets, sinks, baths and shower units in addition to the disinfection of drains and the washing of tiled surfaces.
Aqueous chlorine bleaching products are well known in the art and have been used for many years in a variety of bleaching and disinfecting applications. The active component of a product of this type is normally an alkali metal hypochlorite, usually at a level from 1 to 15% by weight, and the physical characteristics of the product are those of a dilute salt solution with a viscosity less than 20 centistokes (20 x 10-⁶ M2s^-1).
In recent years, interest has developed in chlorine bleach products of higher viscosity, in order to provide longer lasting adherence to vertical surfaces and hence greater efficacy, and a number of compositions have been disclosed that are stated to be both chemically stable and physically stable over an extended period of time.
Examples of such compositions are disclosed by British Patent No. 1329086, European Published Patent Applications Nos. 0021581, 0030401, French Published Patent Application No. 2355909 and British Patent Application No. 2003522A.
These thickened compositions incorporate one or more bleach stable surfactants as an aid in increasing viscosity and a preferred example of such a surfactant is an amine oxide containing one C₁₀―C₁₈ alkyl group and two lower alkyl, usually C₁-C₄ alkyl groups. The compositions also contain a source of alkalinity and alkali metal salts of various kinds.
In order to achieve a significant enhancement of viscosity the prior art has employed other surfactants in admixture with the amine oxide such as alkali metal fatty acid salts, alkali metal alkyl sulphate salts and saccharose esters, and viscosities of up to 150 centistokes (150 x 10^-6 m²s^-1) at 25°C are stated to be obtainable by this technique.
It has now surprisingly been found that stable aqueous chlorine bleach-containing compositions having viscosities appreciably in excess of 150 centistokes (150 x 10-⁶ m²s^-1) can be achieved without the necessity of employing the surfactant mixtures taught as necessary by the prior art.
This finding has also simplified the formulation of a thickened chlorine bleach composition insofar as it lowers the level of organic components in the formulation and thereby lessens the problem of ensuring chemical stability as well as reducing the cost of the composition.
It has also been found that compositions in accordance with the invention display cleaning advantages relative to commercially available chlorine bleach compositions embodying the prior art.
According to the present invention there is provided a stable single phase aqueous detergent composition incorporating a tertiary amine oxide as the sole surfactant species, together with at least one ionisable water soluble compound in an amount to provide a total ionic strength of the composition of at least 3.0 moles/dm³ wherein the amine oxide has the formula R₁R₂R₃N→O wherein R₁ contains an average of from 14 to 16 carbon atoms and is selected from linear moieties and moieties containing up to 25% methyl branching predominantly in the 2-position relative to the nitrogen atom of the amine oxide, R₂ and R₃ are C₁-C₄ alkyl groups or C_Z-C₄ hydroxyalkyl groups, the total ionic strength of the composition is not greater than 7.81 g moles/dm³ and the amine oxide is present in an amount of from 1.0% to 2.5% by weight of the composition, such that said composition has a viscosity of at least 0.18 Pa.s (180 cp) at 20°C.
In a preferred aspect of.the invention the composition incorporates a hypochlorite bleach.
In this specification fluid viscosity is expressed as the dynamic viscosity η in centipoises (10-³ Pa.sec). The dynamic viscosity is measured by a Brookfield RVT viscometer and for the purposes of this specification measurements are made with Spindle No. 3 at 100 rpm and a liquid temperature of 20°C. Fluid viscosity can also be expressed as the kinematic viscosity v in centistokes (10^-6m²·s^-1.) as measured by an Ostwald viscometer and is characterised by the expression v = n/p where η is the dynamic viscosity in centipoises and p is the density in g/cm³. Compositions in accordance with the present invention have a density in the range from 1.10 to 1.25 g/cm³, typically approximately 1.15 g/cm³, so that the numerical value of the kinematic viscosity in centistokes is slightly less than that of the dynamic viscosity in centipoises.
The invention will be described primarily with reference to an aqueous composition containing an alkali metal hypochlorite bleach, the latter providing the majority, and preferably substantially all, of the ionic strength requirement. However, the invention also embraces non-bleach compositions in which the ionic strength is provided by any ionisable alkali or alkali earth metal compound.
Bleach composition embodiments of the present invention therefore comprise an amine oxide of defined structure and an alkali metal hypochlorite there being sufficient ionisable inorganic salt present to provide an ionic strength of at least 3.0 g moles/dm³.
The alkali metal hypochlorite may be a lithium, potassium or sodium hypochlorite and the level of hypochlorite in the composition is normally arranged to lie in the range 1-12%, preferably 5-10% by weight. Customarily hypochlorite bleach compositions contain approximately 6% or 9% hypochlorite by weight. However, the activity of chlorine bleaching compositions is conventionally expressed in terms of the weight percentage of available chlorine in the composition, and the actual weight percentage of bleaching species is arranged to provide the desired level of 'available chlorine'. The preferred hypochlorite species is sodium hypochlorite which contains 95.3% available chlorine.
Alkali metal hypochlorites are commercially available as aqueous solutions containing 10-15% by weight 'available chlorine' and the bulk suppliers normally produce material having available chlorine contents towards the upper end of this range viz. 12-14% by weight. These commercially available hypochlorite solutions contain other salts as byproducts or contaminants, more specifically free alkalinity in the form of alkali metal hydroxide and alkali metal carbonate, and alkali metal chloride. Low levels of other species such as sodium chlorate are also believed to be formed during hypochlorite manufacture but their chemical stability is sufficiently low that they have largely decomposed by the time the hypochlorite is employed in product formulations. The levels of the byproduct materials depend on the processing conditions employed in the manufacture of the hypochlorite but in general they fall within the ranges

0.2-1.0% alkali metal hydroxide
0.01-0.1% alkali metal carbonate
10.0-18.0% alkali metal chloride
expressed as a weight percentage of the hypochlorite solution as supplied.

Amine oxides useful in the present invention have the formula R₁,R₂R₃N→O wherein R₁ is a linear alkyl group in which the number of carbon atoms is 14<R₁≤16 and R₂ and R₃ are C₁-C₄ alkyl groups or C_Z-C₄ hydroxy alkyl groups. The amine oxide is present in an amount of from 1.0% to 2.5% and, in preferred embodiments of the invention from 1% to 1.5% by weight of the composition. The R₁ group may be derived from natural or synthetic hydrocarbon sources. For the purposes of the present invention linear groups are defined as including moieties incorporating up to 25% methyl branching, predominantly in the 2-position relative to the nitroqen atom of the amine oxide.
For the hypochlorite bleach aspect of the composition, preferred compositions contain an amine oxide level <2.0%, more typically 1.0-1.5% and also a lower ionic strength viz. 3.0 g moles/dm³ minimum in order to achieve target viscosity. Both of these reductions in ingredient level lead to improved storage stability and also lower the cost of the product.
The ionisable water soluble compound which forms the other major component of the compositions of the invention is a non surface active organic, or inorganic, compound which must be present in an amount to provide an ionic strength of at least 3.0 g moles/dm³.
The ionisable compound(s) can be inorganic in nature e.g. hydroxide sulphate, halide (particularly chloride) carbonate, nitrate, orthophosphate, pyrophosphate, polyphosphate or silicate, or organic such as citrate, formate, acetate or succinate. In a preferred aspect of the invention in which sodium hypochlorite bleach is incorporated, the hypochlorite itself, together with the sodium hydroxide, chloride and chlorate associated with the bleach provides the, or a major proportion of the ionisable compounds required by the invention. In the preferred hypochlorite bleach-containing embodiments of the invention, certain inorganic compounds such as silicates, and organic compounds incorporating oxidisable groups are unstable and should be avoided.
The ionic strength of the composition is calculated by means of the expression
where

C, is the molar concentration of the ionic species in g moles/dm³.
Z, is the valency of the species.

The function C₁Z_l ² is calculated for each of the ionic species in solution, these functions are summed and divided by two to give the composition ionic strength.
The ionisable alkali metal compound normally comprises a caustic alkali such as sodium or potassium hydroxide either alone or in admixture with alkali metal salts. The level of sodium hydroxide necessary to provide a total composition ionic strength of 3.0 g moles/dm³ where the composition contains only the amine oxide would be approximately 11 % to 12% by weight of the composition dependent on the density of the solution. More preferably, for product safety reasons, the at least one ionisable compound comprises a mixture of a caustic alkali in an amount of from 0.5% to 2% by weight of the composition together with one or more alkali metal salts in an amount of at least 10% by weight, more usually at least 15-20%.
In that aspect of the invention directed to liquid detergent compositions suitable for cleaning hard surfaces such as walls and windows, the ionisable compound can include any of the water soluble inorganic and organic builder and sequestrant salts normally incorporated in such products. Compounds classifiable and well-known in the art as detergent builder salts include the nitrilotriacetates, polycarboxylates, citrates, ortho- and pyro-phosphates, and mixtures of any of these. Metal ion sequestrants include all of the above, plus materials like ethylenediaminetetraacetate, the amino- polyphosphonates and phosphates. A wide variety of poly-functional organic acids and salts is disclosed in European Patent Application Publication No. 0040882 which contains examples of the use of such materials in various cleaning compositions. In general the builder/sequestrant will comprise from 1 % to 25% of the composition. Citric acid (2%-20% as sodium citrate) is a preferred builder.
In the aspect of the invention in which a hypochlorite bleach is incorporated the bleach itself, containing the range. of by-product materials previously mentioned, provides a major portion of the ionic strength requirement, viz at least 3.0 g moles/dm³ assuming an available chlorine level of 9% in the composition. In practice therefore it is usually only necessary to add alkali metal hydroxide to obtain the desired ionic strength. A highly preferred bleach composition embodiment of the invention therefore comprises from 1 % to 1.5% C₁₄linear alkyl dimethyl amine oxide, from 9.0% to 9.5% sodium hypochlorite, from 9.0% to 9.5% sodium chloride and from 0.5% to 1.5% sodium hydroxide. A desirable optional component of compositions in accordance with the invention is a perfume which is present at a level of from 0.01 % to 0.5% preferably from 0.05% to 0.25% by weight of the composition.
The compositions are made by conventional mixing techniques. Although any order of mixing can be used, presolution of the alkali metal hydroxide and any alkali metal salt is desirable and these are normally added to a solution of the amine oxide. Perfume is then added under high shear agitation together with any additional water to provide the desired product concentration. In the aspect of the invention in which an alkali metal hypochlorite bleach is included, this component is added last.
The invention is illustrated in the following examples in which percentages are expressed by weight of the composition unless otherwise stated.
In the examples reference to ingredients have been abbreviated as follows:

Example 1

The following compositions were prepared by dissolving pelleted sodium hydroxide in soft water, adding this to the amine oxide solution and blending this mixture with high shear agitation into an aqueous sodium hypochlorite solution^*.
6 The density of each of these compositions was 1.15 g/ml and the ionic strength for each composition was calculated to be 3.5 g moles/dm^3. The product viscosity was measured with a Brookfield viscometer using the No. 3 spindle at 100 rpm at a temperature of 20°C.
^*GPR hypochlorite containing 11.5% by weight of available chlorine, supplied by British Drug Houses Ltd. 0

Example 2

The following compositions are in accordance with the invention.
All of the compositions exhibit viscosities in excess of 200 cp (0.20 Pa-sec.) at 20°C after 24 hours.

Claims

1. A stable single phase aqueous detergent composition incorporating a tertiary amine oxide as the sole surfactant species, together with at least one ionisable water soluble compound in an amount to provide a total ionic strength of the composition of at least 3.0 moles/dm³ characterised in that the oxide has the formula R₁R₂R₃N↦O wherein R₁ contains an average of from 14 to 16 carbon atoms and is selected from linear moieties and moieties containing up to 25% methyl branching predominantly in the 2-position relative to the nitrogen atom of the amine oxide, R₂ and R₃ are C₁-C₄ alkyl groups or C₂―C₄ hydroxyalkyl groups, the total ionic strength of the composition is not greater than 7.81 g moles/dm³ and the amine oxide is present in an amount of from 1.0% to 2.5% by weight of the composition, such that said composition has a viscosity of at least 0.18 Pa.s (180 cp) at 20°C.

2. An aqueous detergent composition according to Claim 1 characterised in that substantially all of the ionic strength is provided by a mixture of alkali metal hypochlorite, alkali metal chloride and alkali metal hydroxide.

3. An aqueous detergent composition according to Claim 2 characterised in that it comprises from 1% to 1.5% C₁₄ linear alkyl dimethyl amine oxide, from 9.0% to 9.5% sodium hypochlorite, from 9.0% to 9.5% sodium chloride and from 0.5% to 1.5% sodium hydroxide.

4. An aqueous detergent composition according to either one of Claims 2 and 3 wherein the composition incorporates a bleach stable perfume.

5. An aqueous detergent composition according to Claim 1 characterised in that the ionisable water soluble compound is an organic or inorganic builder or sequestrant salts.

6. An aqueous detergent composition according to Claim 5 wherein the water soluble compound is selected from alkali metal carbonates, citrates, pyrophosphates, amino polyacetates and amino polyphosphonates.