The present invention provides a liquid laundry detergent composition. In particular, it relates to a concentrated liquid laundry detergent composition for use in domestic laundry.

Laundry liquid formulations containing saturated long chain alkyl ether carboxylates with high degrees of ethoxylation are desirable as they provide enhanced cleaning particularly of sebum soil.

Saturated long chain alkyl ether carboxylates with high degrees of ethoxylation are solid waxy materials at room temperature.

To reduce weight in transportation it is desirable to have highly concentrated liquid laundry detergent with minimal contents of water. This may be used directly for washing or further mixed with other ingredients before washing. However it is highly desirable that the concentrated liquid detergent is a pourable liquid, both for ease of use for the consumer when using the concentrated liquid detergent, or when the concentrated liquid detergent is further processed into a more complex liquid detergent.

Accordingly, there is need for highly concentrated laundry detergents containing high levels of saturated long chain alkyl ether carboxylates that are pourable liquids at room temperature.

WO 2013/087286 (Unilever) discloses aqueous liquids formulations containing alkyl ether carboxylic acids, betaines, anionic surfactant, non-ionic surfactant for providing softening benefits.

WO 2014/060235 (Unilever) discloses an aqueous laundry detergent composition comprising (a) nonionic surfactant, (b) anionic surfactant, (c) alkyl ether carboxylic acid or carboxylate salt thereof, and, (d) a polyglucosamine or a copolymer of glucosamine and N-acetylglucosamine; and to its use to soften fabrics.

In one aspect, the present invention provides a liquid laundry detergent composition comprising:

1. (i) from 50 to 80 wt.% of a linear alkyl benzene sulfonic acid surfactant;
2. (ii) from 15 to 45 wt.% of an alkyl ether carboxylic acid surfactant of the following structure:
   
            R₁-(OCH₂CH₂)_n-OCH₂-COOH,
   
   wherein: R₁ is selected from saturated C₁₆ to C₂₂ linear or branched alkyl chains, preferably C₁₆ to C₁₈ linear alkyl chains, and wherein n is selected from 10 to 24;
3. (iii) less than 10 wt.% water;
4. (iv) from 0 to 20 wt.% non-ionic surfactant of the following structure
   
            R₂-(OCH₂CH₂)_n-OH,
   
   wherein: R₂ is selected from saturated C₁₂ to C₂₂ linear or branched alkyl chains, preferably C₁₆ to C₁₈ linear alkyl chains, and wherein n is selected from 5 to 30, preferably 10 to 20;

Preferably the pH of the formulation is from 0.5 to 2.0, more preferably from 0.5 to 1.5.

A preferred liquid laundry detergent composition comprises:

1. (i) from 60 to 80 wt.% of a linear alkyl benzene sulfonic acid surfactant;
2. (ii) from 20 to 40 wt.% of an alkyl ether carboxylic acid surfactant of the following structure:
   
            R₁-(OCH₂CH₂)_n-OCH₂-COOH,
   
   
   • wherein: R₁ is selected from saturated C₁₆ to C₁₈ linear alkyl chains,
   • and wherein n is selected from 10 to 20;
3. (iii) less than 10 wt.% water;
4. (iv) from 0 to 20 wt.% non-ionic surfactant of the following structure
   
            R₂-(OCH₂CH₂)_n-OH,
   
   wherein: R₂ is selected from saturated C₁₂ to C₂₂ linear or branched alkyl chains, preferably C₁₆ to C₁₈ linear alkyl chains, and wherein n is selected from 10 to 20;

Water contents are measured by Karl Fischer Titration. This may be accomplished using an automated Karl Fischer titrators, available from MetroOhm, and Mettler Toledo.

The pH of the formulation is that of a 1 wt.% solution of the liquid laundry detergent composition dissolved in demineralised water at 293K.

Room temperature as used herein is defined as 293K.

The liquid laundry composition comprises from 50 to 80 wt.%, preferably from 55 to 80 wt.%, more preferably from 55 to 75 wt.%, most preferably from 60 to 75 wt.% of the linear alkyl benzene sulfonic acid surfactant. Weights are expressed as the protonated form (i.e. the linear alkyl benzene anionic sulfonic acid form).

They may be used as salt version, for example alkali metal salt (preferably sodium salt), triethanolamine, monoethanol amine salt. The sodium salt is most preferred. Preferably the non-neutralised acid form is used.

Linear alkyl benzene sulfonic acid has the structure: where x + y = 7, 8, 9 or 10.
Preferably x + y = 8 is present at a weight level greater than 28 wt.% of the total level of the linear alkyl benzene anionic surfactant.
Preferably x + y = 9 is present at greater than 28 wt.% of the total level of the linear alkyl benzene anionic surfactant. Weights are expressed as the protonated form.

The surfactant may be produced by a variety of different routes. Synthesis is discussed in Anionic Surfactants Organic Chemistry edited by H.W. Stache (Marcel Dekker, New York 1996).

Linear alkyl benzene sulfonic acid may be made by the sulfonation of linear alkyl benzene. The sulfation can be carried out with concentrated sulphuric acid, oleum or sulphur trioxide. Linear alkyl benzene sulfonic acid produced by reaction of linear alkyl benzene with sulphur trioxide is preferred.

Linear alkyl benzene may be produced by a variety of routes. Examples include: Benzene may be alkylated with n-alkenes using HF catalyst.

Benzene may be alkylated with n-alkenes in a fixed bed reactor with a solid acidic catalyst such as Alumosilicate (DETAL process).

Benzene may be alkylated with n-alkenes using an aluminium chloride catalyst. Benzene may be alkylated with n-chloroparaffins using an aluminium chloride catalyst.

The liquid laundry composition comprises from 15 to 45 wt.%, preferably from 15 to 40 wt.%, more preferably from 17.5 to 40 wt.%, most preferably from 20 to 40 wt.% of the alkyl ether carboxylic acid anionic surfactant.

Weights of alkyl ether carboxylic acid are calculated as the protonated form, R₂-(OCH₂CH₂)_n-OCH₂COOH, where n is from 10 to 24. They may be used as salt version for example sodium salt, triethanolamine, monoethanol amine salt. The sodium salt is most preferred.

n may be from 10 to 24, preferably from, 10 to 20, more preferably from 15 to 20.

Alkyl ether carboxylic acids synthesis is discussed in Anionic Surfactants Organic Chemistry edited by H.W. Stache (Marcel Dekker, New York 1996). They may be synthesised via the reaction of the corresponding alcohol ethoxylate with chloroacetic acid or monochloro sodium acetate in the presence of NaOH:-

         R₂-(OCH₂CH₂)_n-OH + NaOH + ClCH₂COONa → R₂-(OCH₂CH₂)_n-OCH₂COOH + NaCl + H₂O

In this synthesis residual R₂-(OCH₂CH₂)_n-OH may be present, preferably levels of R₂-(OCH₂CH₂)_n-OH are from 0 to 10 wt.% in the alkyl ether carboxylic acid. Low levels of diglycolic acid and glycolic acid may be present as bi products.

The alkyl ether carboxylic acid may also be synthesised via an oxidation reaction:-

         R₂-(OCH₂CH₂)_n-O CH₂CH₂OH → R₂-(OCH₂CH₂)_n-OCH₂COOH

The oxidation is typically conducted using oxygen as the oxidant under basic conditions in the presence of metal catalyst such as Pd/Pt, as described in DE3135946; DE2816127 and EP0304763.

The alkyl chain may be linear or branched, preferably it is linear.

The alkyl chain is preferably selected from CH₃(CH₂)₁₅ and CH₃(CH₂)₁₇

The alkyl ether carboxylic acid is most preferably of the structure:

         CH₃(CH₂)₁₇(OCH₂CH₂)₂₀OCH₂COONa

Alkyl ether carboxylic acids are available from Kao (Akypo ®), Huntsman (Empicol®) and Clariant (Emulsogen ®).

The alkyl ether carboxylic acid is preferably used directly form the synthesis without further purification.

It is preferred that the weight ratio of linear alkyl benzene sulfonic acid surfactant to the alkyl ether carboxylic acid surfactant is preferably from 55:45 to 5:1, more preferably from 1.5:1 to 5:1. The weight ratio of linear alkyl benzene sulfonic acid surfactant to the alkyl ether carboxylic acid surfactant may be from 1.5:1 to 4.5:1, for example from 1.5:1 to 4:1; or from 2:1 to 4.5:1; or 2:1 to 4:1; or even 2.5:1 to 4.25:1; or even 2.5:1 to 4:1.

Water may be absent from the formulation, or present at a level of less than 10 wt.%, preferably less than 9 wt.%. If water is present, then it is present preferably at a level of from 0.01 to 8 wt.%, more preferably from 0.1 to 8 wt.%, most preferably from 1 to 8 wt.%.

Non-ionic surfactant may be absent from the formulation, or present at a level of less than 20 wt.%, preferably less than 15 wt.%, more preferably less than 12 wt.%. If non-ionic surfactant is present, then it is present preferably at a level of from 0.1 to 20 wt.%, more preferably from 0.1 to 15 wt.%, most preferably from 0.25 to 12 wt.%.

The non-ionic surfactant has the following structure:

         R₂-(OCH₂CH₂)_n-OH,

wherein: R₂ is selected from saturated C₁₂ to C₂₂ linear or branched alkyl chains, preferably C₁₆ to C₁₈ linear alkyl chains, and wherein n is selected from 5 to 30, preferably 10 to 20.

The liquid detergent composition of the invention can be considered a concentrated liquid detergent composition. It may be used directly, or more preferably used as an ingredient to formulate further liquid detergent compositions.

Such further liquid detergent compositions may comprise further ingredients such as: fatty acids or salts thereof, shading dyes, enzymes (such as lipase, protease, amylase, cellulase), antiredeposition polymers, dye transfer inhibiting polymers, builders, structurants or thickening polymers, sequestrants, perfumes, and/or soil release polymers.

The following mixtures containing 20 wt.% of alkyl ether carboxylate (R₁ = stearyl, n = 20, used as Na salt) and 80 wt.% second surfactant were prepared at 333K. At this temperature, all ingredients were liquid. They were then cooled to 293K. The phase results are shown in the table. Second surfactant Phase at 293K linear alkyl benzene anionic sulfonic acid Pourable Liquid inventive Sodium lauryl ether sulfonate with 1 mole of ethoxylation Solid comparative Sodium lauryl ether sulfonate with 3 mole of ethoxylation Soft Gel comparative Non-ionic surfactant: alcohol ethoxylate with C13-15 and 7 moles of ethoxylation Soft Gel comparative

The experiment with was repeated with different ratios of linear alkyl benzene anionic sulfonic acid to the alkyl ether carboxylate. The results are shown in the following table, along with the entry for the previous example:- Wt% alkyl ether carboxylate Wt% linear alkyl benzene anionic sulfonic acid Phase at 293K 100 0 solid comparative 50 50 Soft gel comparative 40 60 Pourable Liquid inventive 30 70 Pourable Liquid inventive 20 80 Pourable Liquid inventive