WO1994004639A1

WO1994004639A1 - Liquid compositions

Info

Publication number: WO1994004639A1
Application number: PCT/EP1993/002060
Authority: WO
Inventors: Francesco Maria Puerari; David Roscoe
Original assignee: Unilever Plc; Unilever Nv
Priority date: 1992-08-11
Filing date: 1993-07-31
Publication date: 1994-03-03
Also published as: GB9217001D0; AU4706193A

Abstract

The invention provides a liquid, cleaning composition comprising: a) 2-40 % wt surfactant, said surfactant comprising primary alcohol sulphate (i) and optionally one or more nonionic surfactant (ii) wherein at least 50 % wt of the surfactant present is primary alcohol sulphate, b) 1-30 % wt of a potassium carbonate on aqueous phase. In typical formulations according to the present invention, the composition further comprises a solvent other than water.

Description

LIQUID COMPOSITIONS

Technical Field;

The present invention relates to surfactant containing, liquid compositions which show improved storage stability, and in particular to carbonate containing compositions which are stable at low temperatures.

Background to the Invention:

General purpose household cleaning compositions for hard surfaces such as metal, glass, ceramic, plastic and linoleum surfaces are commercially available in both powdered and liquid form. Powdered cleaning compositions consist mainly of builder or buffering salts such as phosphates, carbonates, silicates etc. Such compositions display good inorganic soil removal, but they can be deficient in cleaning ability on organic soils such as the calcium and/or magnesium salts of fatty acids and fatty/greasy soils typically found in the domestic environment.

Liquid cleaning compositions generally comprise an organic solvent and have the great advantage that they can be applied to hard surfaces in neat or concentrated form so that a relatively high level of surfactant material and organic solvent is directly delivered onto the soil. Typically, the surfactants used in commercial general purpose cleaners include one or both of linear alkyl benzene sulphonates and secondary alkane sulphonates.

These liquid compositions are of particular utility in the cleaning of hard surfaces such as floors and walls and kitchen or bathroom surfaces as mentioned above and in cleaning soft furnishings such as upholstery, carpets, curtains etc. Although such compositions were originally manufactured and sold in dilute form, there is currently a move towards concentrated compositions which can be diluted for general use or used neat on stubborn soils. These, concentrated products have the further advantages that they are more portable and can be packed at lower cost than dilute products.

The incorporation of certain surfactants into such solvent/water compositions presents no difficulties when these surfactants are present at relatively low concentrations, for example European Patent EP 0344847 (P&G) discloses compositions comprising butoxy-propanol solvents in combination with up to 5%wt sodium linear C8-C18 alkyl benzene sulphonate.

Mixtures of linear alkyl benzene sulphonates with alcohol ethoxylates and optionally small amounts of fatty soaps comprise the surfactant system used in a number of successful commercial products. In the presence of certain electrolytes, typically sodium carbonate, the aforementioned surfactants are known to form stable systems. This stability is important on storage of the product, particularly at low temperatures, as phase separation of components, particularly relative separation of two or more of builders, solvent and surfactant is prevented. The presence of sodium carbonate also buffers the pH of the product towards the alkaline, helping to saponify fats and oils and converting fatty acids into soaps while maintaining the pH in a region which is not particularly harmful to the skin providing that contact is not prolonged.

An outstanding technical problem with such compositions is that the surfactants which are most commonly used, are not as desirable for environmental reasons as other surfactant systems.

In particular, primary alcohol sulphate (hereinafter referred to as PAS) is an environmentally desirable surfactant, both due to its ease of biodegradability as compared with linear alkyl benzene sulphonates and secondary alkane sulphonates and the fact that it can be derived from natural materials such as coconut and other vegetable oils as a source of fatty acid residues.

However, it has not proved possible to form cold-storage stable concentrated systems comprising significant levels of PAS in combination with non-ionic surfactants, in systems containing carbonates. In domestic use and in commercial storage and transportation, products are occasionally subjected to temperatures as low as -15 Celcius and may often be subjected to temperatures at or below zero Celsius during winter months in temperate climates.

Prior disclosures of the use of PAS in liquid general purpose cleaners include EP 107946 (P&G: 1982) which relates to liquid detergent compositions comprising Mg-PAS, a water soluble C₁₃-C₁₈ alkane or alkene sulphonate and a water soluble alkyl ether sulphate. EP 039110 (P&G: 1980) also relates to compositions comprising Mg-PAS, alkylbenzene sulphonate and alkyl ether sulphate.

Brief Description of the Invention:

We have now determined that the use of potassium carbonate rather than sodium carbonate as the electrolyte significantly improves product stability at low temperatures in surfactant systems which mostly comprise primary alcohol sulphate. Detailed Description of the Invention:

According to the present invention there is provided a liquid, cleaning composition comprising:

a) 2-40%wt surfactant, said surfactant comprising primary alcohol sulphate (i) and optionally one or more nonionic surfactant (ii) wherein at least 50%wt of the surfactant present is primary alcohol sulphate,

b) l-30%wt of potassium carbonate on aqueous phase.

Generally, the potassium carbonate will be present as such at a level of l-20wt% on product. It should be noted that some or all of the potassium can be the potassium salt of the primary alcohol sulphate. Other sources of potassium ions can be employed: as a further alternative at least a part of the potassium may be supplied as potassium hydroxide: this has the advantage that the pH of the composition may be adjusted thereby.

Without wishing to restrict the scope of the invention by reference to any theory of operation, it is believed that the presence of potassium ions in the compositions leads to the formation of a network of potassium-PAS crystals at temperatures below 5 Celcius. Potassium carbonate does not crystallise out of solution due to its solubility parameters and it is believed that this subsequently prevents the formation of strong electrolyte solutions on re-heating to room temperature which could otherwise bring about phase separation.

Consequently, a characteristic functional definition of the present invention is that it provides, isotropic, liquid cleaning composition comprising surfactant, and a carbonate salt, wherein at least 50%wt of the surfactant is a primary alcohol sulphate and wherein the carbonate salt does not precipitate out when the product is cooled to zero Celsius and stored for 24 hours at that temperature.

Surfactants:

The preferred primary alcohol sulphate comprises a mixture of materials of the general formulation:

RO-SO₃X

wherein R is a C₈ to C₁₈ primary alkyl group and X is a solubilising cation. Suitable cations include sodium, magnesium, potassium, ammonium and mixtures thereof. Particularly preferred PAS molecules are those with a major proportion of C₁₀-C₁₄ alkyl residues. These can be obtained by forming the PAS from fatty acids obtained from coconut oil although they can also be obtained from synthetic sources.

In embodiments of the invention the final composition is such that the molar ratio of potassium ions to primary alcohol sulphate ions falls in the range 1:5 to 1:1 and is preferably around 1:2.

Preferred ranges for the surfactant: potassium carbonate ratios fall in the range 30:1 to 2:1, preferably 15:1 to 6:1. Typical potassium carbonate contents are l-10%wt, preferably 2-5%wt.

Particularly preferred compositions comprise 15-30% primary alkyl sulphate and 5-15% non-ionic surfactant. The preferred ratio of the PAS to the non-ionic is in the range 3:1 to 1:1 and is preferably around 2:1.

The preferred nonionic surfactant is selected from the group comprising ethoxylated alcohols of the general -formula:

R₁-(OCH₂CH₂)_m-OH

wherein R₂ is straight or branched, C₈ to C₁₈ alkyl and the average degree of ethoxylation m is 1-14, preferably 3-8. The starting materials for the synthesis of these ethoxylated alcohols, a minor component of the surfactant system,^' are available from both natural and synthetic sources.

Solvents

In typical formulations according to the present invention the composition further comprises a solvent other than water. Typical solvent contents are l-30%wt of the composition, preferably 5-20% of the composition. Preferred ranges for the surfactant:solvent ratios fall in the range 1:1 to 10:1, preferably 2:1 to 5:1. The presence of solvent is optional.

Preferably, the solvent is selected from: propylene glycol mono n-butyl ether, dipropylene glycol mono n-butyl ether, propylene glycol mono t-butyl ether, dipropylene glycol mono t-butyl ether, diethylene glycol hexyl ether, ethyl acetate, methanol, ethanol, isopropyl alcohol, ethylene glycol monobutyl ether, di-ethylene glycol monobutyl ether and mixtures thereof.

Preferred solvents are selected from the group comprising ethanol (preferably as industrial methylated spirits), propylene glycol mono n-butyl ether (available as 'Dowanol PnB' [RTM] ) and di-ethylene glycol monobutyl ether

(available as 'Butyl Digol' [RTM] or 'Butyl Carbitol'

[RTM] ) .

Minors:

The compositions of the invention can further comprise other components selected from the group comprising: perfumes, colours and dyes, hygiene agents, foam-control agents, viscosity modifying agents and mixtures thereof. Preferably the foam control agents comprise calcium sensitive soaps in combination with hydrocarbons.

Typically compositions according to the present invention are isotropic. An advantage of isotropic compositions, is that they need not be shaken vigorously before use.

Generally, compositions according to the present invention are transparent.

Preferably, compositions form a clear solution when diluted with water.

As mentioned above, compositions according to the present invention can contain a hydrophobic oil in combination with a calcium sensitive soap as a foam control system.

Preferably, the hydrophobic oil is a linear or branched chain hydrocarbon, a terpene or a silicone oil. More preferably, the hydrophobic oil is a paraffin: most preferably having a 50%wt loss boiling point in the range 170-300, Celsius. The term 50% loss boiling point being intended to indicate that 50% of the weight of the paraffin can be distilled off at a temperature within this range. In general the limits of boiling points of paraffin suitable for use in the composition of the present invention lie between 171 and 250 Celsius. We have found that the isoparaffins, i.e. branched chain paraffins, are particularly effective when compared with other hydrophobic oils such as n-decane and n-tetradecane.

The solubilised hydrophobic oil content of embodiments of the present invention is typically in the range 0.2-5wt%, preferably 1.0-2.0wt%.

The insoluble calcium salt-forming surfactant content of embodiments of the invention is 0.2-5%wt: the upper levels of this range being used for more highly concentrated compositions. Preferably the insoluble calcium salt-forming surfactant content is in the range 1.0-2.0%wt. Surfactants which form insoluble calcium salts include fatty acids and soluble salts of fatty acids (true 'soaps') with a suitable cation, preferably derived from fatty acids having an average carbon chain length in the range 8-24. Alternative surfactants include surfactant sulphates and sulphonates: in general, anionic surfactants of which the calcium salt has a Krafft temperature above product use temperature.

The preferred ratio of insoluble calcium salt forming surfactant to hydrophobic oil is in the range 0.5-1:1-0.5, preferably about 1:1.

Particularly preferred embodiments of the invention provide a liquid composition comprising:

a) 15-30%wt primary alcohol sulphate (i) and 5-15% nonionic surfactant (ii) wherein the ratio of (i) : (ii) falls in the range 3:1 to 1:1, b) l-5%wt potassium carbonate, c) 5-15%wt glycol ether or C₂-C₅ alcohol solvent, d) 0.2-5%wt hydrophobic oil, and, e) 0.2-5%wt insoluble calcium salt-forming surfactant.

In order that the present invention may be further understood it will be illustrated hereafter by way of example.

EXAMPLES:

The following formulations were prepared by mixing of the components as listed in table 1. The components were obtained as follows:

Iso: ISOPAR-L (RTM, ex Exxon), a branched hydrocarbon with a boiling point range of

171-191 Celsius;

PAS: LIAL-123S (RTM ex. Eniche ) , a sodium salt of primary alcohol sulphate having an average alkyl chain length in the range C₁₂-C₁₃;

Non: BIODAC L5-S52 (RTM: ex DAC) , nonionic, ethoxylated alcohol surfactant having an average alkyl chain length in the range C12- C16 and average EO of 5.5-6.0.;

Sol: Butyl Carbitol (RTM: ex Union Carbide);

CFA: Coconut fatty acid (available commercially) ;

Per: Commercial perfume

Table 1: Component Ex(1) Ex(2) Ex(3) Ex(4) Ex(5)

18.5 18.5 18.5 18.5

9.5 9.5 9.5 9.5

1.4 1.4 1.4 1.4

8.0 8.0 8.0 8.0

1.8 1.8 1.8 1.8

1.5 1.5 1.5 1.5

3.0 2.5 3.0 2.5

0.2 0.2

0.3 0.3

Water -to 100%wt-

The quantity of metal hydroxide added was sufficient to bring the pH of the composition to pH 11 in all cases, rather than being exactly 0.2. The precise quantity required is determined by experiment and is influenced by the free alkali level in the other components, particularly the PAS raw material .

The comparative examples Ex(2-5) were all found to form a precipitate identified by X-ray crystallography as sodium carbonate decahydrate after prolonged storage (more than 24 hours) at zero Celcius or after repeated (daily) freeze thaw cycles.

Example 2 shows that sodium carbonate leads to an unstable product and it can be seen from Example 3 that mere reduction in the level of carbonate has no effect . Examples 4 and 5 demonstrate that use of potassium hydroxide to neutralise the fatty acid in the composition provides insufficient potassium ions.

With Example 2, after freezing and subsequent re-heating to room temperature, a phase separation was observed and a lower layer of concentrated sodium carbonate solution formed. The separation of this layer was found to be irreversible without violent shaking of the product.

The Example Ex(l) formed a semi-liquid slurry when stored under the same conditions as the control. When re-heated to room temperature the slurry became liquid without any phase separation. Even after multiple freeze/thaw cycles or prolonged storage at -15 Celsius there was no irreversible phase separation.

Claims

CLAIMS :

1. Aqueous liquid, cleaning composition comprising:

b) l-30%wt potassium carbonate on aqueous phase.

2. Composition according to claim 1 further comprising a solvent other than water.

3. Composition according to claim 1 wherein potassium carbonate is present at a level of l-20wt% on product.

4. Composition according to claim 1 wherein the molar ratio of potassium ions to primary alcohol sulphate ions falls in the range 1:5 to 1:1.

5. Composition according to claim 2 wherein the surfactant: solvent ratios fall in the range 1:1 to 10:1.

6. Composition according to claim 1 wherein the ratio of the PAS to the non-ionic is in the range 3:1 to 1:1.

7. Composition according to claim 1 wherein the primary alcohol sulphate comprises a mixture of materials of the general formulation:

RO-SO₃X wherein R is a C₈ to C₁₈ primary alkyl group and X is a solubilising cation.

8. Composition according to claim 1 wherein the nonionic surfactant is selected from the group comprising ethoxylated alcohols of the general formula:

R₁-(OCH₂CH₂)_m-OH

wherein R_λ is straight or branched, C₈ to C₁₈ alkyl and the average degree of ethoxylation m is 1-14.

9. Composition according to claim 2 wherein the solvent is selected from the group comprising ethanol, propylene glycol mono n-butyl ether and di-ethylene glycol monobutyl ether.

10. Liquid cleaning composition according to claim 1 comprising: a) 15-30%wt primary alcohol sulphate (i) and 5-15% nonionic surfactant (ii) wherein the ratio of

(i) : (ii) falls in the range 3:1 to 1:1, b) l-5%wt potassium carbonate, c) 5-15%wt glycol ether or C₂-C₅ alcohol solvent, d) 0.2-5%wt hydrophobic oil, and, e) 0.2-5%wt insoluble calcium salt-forming surfactant..