This invention relates to surface active compositions.

Alcohol ether sulphate salts of which the anion has the formula where R is an alkyl group having 10 to 20 and preferably 12 to 16 carbon atoms and n is an integer in the range 1 to 7 and preferably 1 to 4 are known surface active agents which are used in, for example shampoos, liquid dishwashing liquids etc.

They are normally produced by ethoxylating an appropriate alcohol, reacting the product with a sulphating agent for example H_zS0₄, S0₃ or S0₂CI₂ and neutralising with an amine for example a C₁ to C₅ mono alkyl amine or ammonia or with an alkali or alkaline earth base or ammonium compound to give the salt which is normally produced as a concentrate containing for example 65 to 75% by weight of the salt and a minor amount of water which includes any water of neutralisation and any introduced as solvent for the neutralising agent. Such concentrates are normally viscous liquids, but if free inorganic sulphates, for example sodium sulphate, or the unsulphated alcohol ethoxylate is present the concentrate may become an elastic gel which is difficult to handle.

The alcohol ether sulphate salts are normally transported as concentrates and then diluted with water and optionally other materials to produce the product ultimately used by the consumer. On dilution of the concentrate another gel of a particularly troublesome type is encountered when a composition of about 55% of the alcohol ether sulphate salt and 45% of water is reached. Frequently ethanol is added to break the gels and allow dilution, but this represents a considerable expense and because of its volatility, a fire hazard.

We have found that the addition of a compound (other than a sulphate or sulphate salt) of average molecular weight 500 to 10,000, preferably 500 to 6,000 and more preferably 1,000 to 3,000, which comprises at least one polyalkylene glycol chain, the compound comprising a total of at least two ether linkages per seven carbon atoms, for example a polyethylene glycol of average molecular weight 500 to 6,000, reduces the problem of dilution with water. The said compounds are of low volatility, and the quantities required are small.

European Patent Application 24,711, published 11.03.81, discloses aqueous surfactant concentrates containing at least 20% by weight of water soluble salts of (inter alia) alkyl polyglycol ether sulphates which contain as viscosity regulators water-soluble salts of mono and/or disulphates of lower polyalkylene ether glycols having a molecular weight of at least 600 (for example polyethylene and polypropylene glycol sulphates) as viscosity regulators, if desired together with polyalkylene ether glycols having a molecular weight of at least 1500. In our invention the viscosity regulators/gel inhibitors do not include such sulphates.

The invention comprises a composition comprising at least 65% by weight of a salt of an alcohol ether sulphate of formula where R and n are as previously defined, M is an ammonium, substituted ammonium, alkali or alkaline earth metal ion and m is the valency of M, characterised in that it further contains an amount of a gel inhibiting compound (other than a sulphate or sulphate salt) of average molecular weight 500 to 10,000 preferably 500 to 6,000 and more preferably 1,000 to 3,000, which comprises at least one polyalkylene glycol chain, the compound comprising a total of at least two ether linkages per seven carbon atoms, for example a polyethylene glycol, which is sufficient to reduce the maximum elasticity of any gel encountered on dilution with water to at most 4x10-⁴ Newtons per sq mm.

The compound may be a polyalkylene or mixed polyalkylene glycol, for example polyethylene glycol or a mixed polyethylene/polypropylene glycol, a compound comprising a polyalkylene glycol chain linked to a phenol or alcohol, for example an alkyl phenol (suitably having 4 to 12 carbon atoms in its alkyl group or groups) or alcohol (suitably having 1 to 16 and preferably 10 to 16 carbon atoms)/ethylene oxide condensate or with two or more polyalkylene glycol chains linked to a residue of a compound having two or more active hydrogen atoms, for example, glycerol or butane 1,4 diol. The compound is very suitably a polyethylene glycol.

The amount of gel inhibiting compound is preferably sufficient to reduce the maximum elasticity of any gel encountered during dilution with water to at most 1 x 10-⁴ Newtons per sq mm. In general 0.5 to 5% by weight of polyethylene glycol is used. Compositions according to the invention tend to be thixotropic; they are readily pumpable in suitable conventional equipment.

The salt is suitably a sodium, potassium, magnesium or ammonium salt, and may be produced by neutralising the acid with a hydroxide, carbonate or bicarbonate of the cation. Direct neutralisation with ammonia or an amine may be carried out.

The invention also comprises a process in which the alcohol ether sulphate salt is mixed with an amount of a compound (other than a sulphate or sulphate salt) of average molecular weight 500 to 10,000, preferably 500 to 6,000 and more preferably 1,000 to 3,000, which comprises at least one polyalkylene glycol chain, the compound comprising a total of at least two ether linkages per seven carbon atoms, for example a polyethylene glycol, which is sufficient to reduce the maximum elasticity of any gel encountered on dilution with water to at most 4x10-⁴ Newtons per sq mm, and then diluted with water. Preferably the compound has at least two ether linkages per five carbon atoms.

A sodium salt of mixed C₁₃ and C₁₅ alcohol (7 to 3 by molar ratio) ethoxylated with an average of 3 mole C₂H₄0 per mole of alcohol, sulphated with S0₃ and neutralised with NaOH solution to produce a 70% mixture by weight of the salt with water (hereinafter referred to as material A) was tested in an oscillating can rheometer to determine its dynamic viscosity and elasticity at a frequency of oscillation of 9.8 cycles per second. Material A with the specified additives was also tested in the same way.

The elasticity of Material A was 745 Nm-² and its dynamic viscosity at 25°C at low shear was 3.95 Pascal seconds (39.5 poise).

Material A with 2.5% w/w of polyethylene glycol (800 mol wt) added had a dynamic viscosity under the same conditions of 3.7 Pascal seconds (37 poise) at low shear and an elasticity of 3.2 x 10^-4 N mm-2.

Material A with 1% w/w polyethylene glycol (1,000 mol wt) added had a dynamic viscosity under the same conditions of 3.4 Pascal seconds (34 poise) at low shear and an elasticity of 4.1 x 10^-4 N _mm-²_.

Material A with 2) w/w polyethylene glycol (1,000 mol wt) added had a dynamic viscosity under the same conditions of 3.6 Pascal seconds (36 poise) at low shear and an elasticity of 2.1 x 10^-4 N m m^-2.

The performance of other additives in material A is shown in the following table.

"Synperonic" TLE is a commercial product produced by alkoxylating methanol. It contains 28 ether links per 63 carbon atoms and has a molecular weight of 1,400.

"Synperonic" A50 is a commercial product produced by condensing a mixed C₁₃ and C₁₅ alcohol (7 to 3 by molar ratio) with c. 50 moles of ethylene oxide per mole.

"Synperonic" OP40 is a product of condensing octyl phenol with c. 40 moles of ethylene oxide per mole.

M.W. means molecular weight.

Materials with the additives all diluted much more readily with water than the pure material. The time required for comparable dilutions was substantially less, for example one tenth, and no problems were encountered with gel formation during dilution.

"Synperonic" is a trademark, the property of Imperial Chemical Industries PLC.