SEQUESTRANT

TECHNICAL FIELD

This invention relates to isotropic aqueous liquid laundry detergents that deliver lower than normal levels of surfactants to the wash and have correspondingly higher than normal levels of performance enhancers comprising polymers, enzymes and sequestrants to compensate for the reduced cleaning due to the reduction in surfactant. These performance enhancers are more weight efficient than the surfactant they replace and thus facilitate compositions that require very low dosage. BACKGROUND

WO09153184 (Unilever) suggests that a laundry detergent liquid concentrate may be designed by replacing surfactant with a mixture of more weight efficient ingredients selected from polymers and enzymes. A preferred composition uses a combination of EPEI and a polyester soil release polymer (SRP) to achieve excellent oily soil and particulate detergency at significantly lower in-wash surfactant levels than would normally be delivered from a high performance liquid. The exemplified compositions comprise anionic surfactant comprising linear alkyl benzene sulphonate neutralised with sodium hydroxide and further comprise soap formed by neutralisation of fatty acid by sodium hydroxide. The compositions are alkaline. It has been found that the SRP used for the examples has a higher level of stability if the concentrated liquid compositions including it are formulated at about pH6.5. There is insufficient space for a conventional bleaching system in such concentrated liquids. However, it is known that bleachable stains may also be removed if relatively high levels of sequestrants are included in the liquid. In the examples of WO09153184 the sequestrant used was Dequest 2066, a polyphosphonate. Other sequestrants disclosed in WO09153184 are: alkali metal, citrates, succinates, malonates, carboxymethyl succinates, carboxylates, polycarboxylates and polyacetyl carboxylates. Specific examples include sodium, potassium and lithium salts of oxydisuccinic acid, mellitic acid, benzene

polycarboxylic acids, C10-C22 fatty acids and citric acid. Other examples are DEQUEST™, organic phosphonate type sequestering agents and alkanehydroxy phosphonates.

FR2677370 (NLN SA) teaches to use a sequestering agent for liquid detergent compositions for linen (washing) containing at least 20 percent by weight of water. It consists of a mixed alkaline-earth metal and alkali metal ammonium C2-C8 alkanolamine or C2-C8 alkaneamine salt of 1 -hydroxyethane-1 1 -diphosphonic acid (HEDP) or of a mixture of the said mixed salts. Another subject of the invention is the stable liquid detergent compositions containing the said

sequestering agent. The HEDP is added to liquid detergents that don't have bleach. Alkanolamine neutralised surfactants may pose a problem for alkali metal salts of HEDP. This precipitation problem is made worse by protease in the liquid. The invention uses either sodium or potassium salts of HEDP premixed with magnesium chloride. TEA / HEDP compositions at pH 7.7 are stable when magnesium chloride is added.

We have confirmed this common general knowledge that the sequestrant 1 - Hydroxyethylidene-1 , 1 -Diphosphonic Acid, abbreviated as HEDP and available from Thermphos as Dequest 2010, gives excellent performance on bleachable stains, even when delivered from the mildly acidic concentrated liquid chosen for soil release polymer stability. However, HEDP has been found to be much harder to incorporate into isotropic liquids with acceptable physical stability compared with the prior art Dequest 2066, this is especially a problem at the incorporation levels needed for a 20ml dose to European front loading automatic washing machines. In particular the high temperature stability of acid HEDP containing versions of the liquids found in WO09153184 has been found to be poor.

WO 99/49009 (P&G) - suggests that the presence of certain EPEI polymers may stabilise HEDP in liquid detergent compositions. We have found that the presence of high levels EPEI does not provide sufficient stability to compositions of the type disclosed in WO09153184 if they are formulated with HEDP in place of Dequest 2066, at least this is true for the EPEI we have tested: Sokalan HP20 which is a nonionic polyethylene imine with a backbone molecular weight of about 600, ethoxylated with an average of 20 moles of ethylene oxide per nitrogen.

US2008015135 (P&G) discloses compact fluid laundry detergent compositions having good economics good cleaning and positive consumer value impression. Amine oxide or betaine may be used. HEDP is one of many possible chelants in the general disclosure.

JP2007077362A (Lion) discloses a liquid detergent composition for clothing which is effective for mud stain and has excellent storage stability. The composition comprises (A) a polyoxyethylene alkyl ether containing a 10-20C alkyl group and having the average addition mol number of ethylene oxide of 3-26 (B) 1 - hydroxyethane-1 1 -diphosphonic acid and/or its salt (C) monoethanolamine (D) one or more compounds selected from a semi-polar surfactant an amphoteric surfactant a polyoxyethylene addition type ammonium salt and a polyoxyethylene addition type amine. Paragraph 0032 makes clear that the pH should not be acidic. Amine oxides and Betaines are both preferred surfactants in these MEA containing liquids with HEDP. It seems that the LAS does not have to be neutralised with MEA. Besides being alkaline these compositions contain no EPEI or polyester soil release polymer. Examples use as "B-1 ": 1 - hydroxyethane-1 ,1 -diphosphonic acid. The maximum level of HEDP incorporated in the examples is 1 %. This is insufficient to obtain the required level of cleaning for low surfactant dose compositions of the type disclosed in WO09153184.

It is desired to include at least 1 .5 wt%, preferably at least 2 wt% of HEDP into low in wash surfactant high polymer, high enzyme compositions of the type disclosed in WO09153184.

SUMMARY OF THE INVENTION According to the present invention there is provided an isotropic liquid laundry detergent comprising: a) at least 10 wt% of a surfactant system, the surfactant system

comprising:

a(i) at least 5 wt% ethoxylated alcohol nonionic surfactant,

a(ii) optionally, amine oxide amphoteric surfactant,

a(iii) at least 5 wt% linear alkyl benzene sulphonate formed from

neutralisation of LAS acid by an amine that buffers at the pH of the composition and a second amine that does not buffer because its pKa is at least 2 units higher than the in-bottle pH of the composition,

a(iv) soap formed from the neutralisation of fatty acid by the first and second amine, and

a(v) optionally, Alkyl ether sulphate; b) at least 1 .5 wt% HEDP, c) at least 5 wt% of a polymer system comprising nonionic EPEI and nonionic PET POET polyester soil release polymer, and d) at least 2 enzymes. the in-bottle pH of the composition being in the range 6.0 to less than 7, preferably 6.3 to 6.7.

HEDP is 1 -hydroxyethane 1 ,1 -diphosphonic acid (HEDP). Preferably the composition comprises at least 2 wt%, more preferably at least 2.5 wt%, HEDP

Preferably the composition contains triethanolamine (TEA) as the buffer amine and monoethanolamine (MEA) as the non buffering amine with pKa at least 2 units higher than the in-bottle pH of the composition. Preferably, the surfactant system containing an amine oxide together with a linear alkylbenzene sulfonate (LAS), a neutralised fatty acid and an ethoxylated alcohol. Advantageously, the composition comprises at least 0.75 wt%, preferably at least 1 .0 wt% amine oxide (a(ii)). The composition also contains two or more enzymes and a polymer system containing ethoxylated polyethyleneimine (EPEI) and a polyethylene terephthalate (PET) polyoxyethylene terephthalate (POET) polyester. Preferred compositions comprise at least 4 wt% EPEI. More preferred compositions comprise at least 3 wt% polyester based soil release polymer.

The in-bottle pH of the composition lies in the range 6.0 to less than 7, preferably 6.3 to 6.7. By in-bottle we mean in whatever container or pack the liquid is stored. It could be a plastic pack in the form of a bottle, squeezable or rigid, stored upright or inverted, or a unit dose format such as a soluble pouch, or a sachet.

Preferably the composition comprises at least 1 .5 wt% triethanolamine.

The composition may comprise at least 10 wt% nonionic surfactant. The composition may comprise as an additional anionic surfactant at least 2 wt% alkyl ether sulphate. When the composition comprises MEA and TEA, the weight ratio of TEA to MEA is preferably from 1 :1 to at most 20:1 . The weight ratio of LAS acid to the total of MEA and TEA lies in the range 1 .1 :1 to 2.5:1 . According to a second aspect of the invention there is provided a washing process comprising the steps of adding to a front loading automatic washing machine 25 ml or less, preferably 20 ml, of a composition according to the first aspect, diluting it with at least 800 times as much tap water, washing clothes with the wash liquor formed by the dilution step and then rinsing the clothes.

DETAILED DESCRIPTION OF THE INVENTION

HEDP is not stable in concentrated isotropic aqueous laundry liquids as crystallization occurs on storage at low temperature. This instability is due to poor solubility of Na-HEDP. This salt of HEDP is formed when a composition comprising the acid form of HEDP is neutralised using sodium hydroxide. Sodium hydroxide is the normal neutralising system employed with linear alky benzene sulphonate surfactant in liquid detergent compositions. In more dilute liquids the amount of excess water is sufficient to keep even the sodium salt of the HEDP in solution. This becomes more difficult as the amount of water is reduced for a concentrated composition. The stability problem gets even worse when water hungry polymers are included into the composition at high levels as is the case with the liquids proposed in WO09153184.

With Empigen BB the level of HEDP that could be incorporated and retain stability was less than 0.4 wt%.

The necessary physical stability of HEDP in aqueous detergent liquids was obtained by replacing TEA/NaOH with TEA/MEA for buffering and pH adjustment (while still maintaining pSRP hydrolytic stability). The Empigen BB carbobetaine was also removed. Empigen BB and Dequest 2010 appear to be incompatible. In preferred embodiments to optimise the sequestrant cleaning benefit, Empigen OB amine oxide was added into the composition.

The MEA may be defined as a non buffering material because the pKa of its conjugate acid lies more than 2 units higher than the final, in-bottle pH of the composition provided the composition is formulated as an acidic in bottle composition. TEA must therefore also be used to provide some buffering capacity to the concentrated composition. This ensures that the polyester soil release polymer and other ingredients are maintained at the correct pH for their optimum storage stability.

Thus although the invention has been described with reference to use of TEA and MEA in practice the MEA could in principle be fully or partially replaced with other weak or strong bases which lie outside the buffering region of interest (pH 6 to 7). Examples of such materials include diethanolamine.

A proviso on the selection of the neutralising system is that the amount of alkali metal salts should not exceed 0.2 wt% in the liquid composition and they are preferably substantially absent to avoid the alkali metal, particularly sodium, forming HEDP salts that come out of solution and render the liquid non isotropic with poor cleaning due to the HEDP being absent from the upper parts of the liquid after storage in-bottle.

The TEA buffer could be partial or fully replaced with another material whose conjugate acid has a pKa of about 6.5.

The amphoteric surfactant could also be replaced with another that has a capacity to buffer to an acidic pH. The invention will now be further described with reference to the following non- limiting examples.

EXAMPLES

In the following examples the key to the material abbreviations is as follows:

MPG is mono propylene glycol,

MEA is monoethanolamine

TEA is triethanolamine.

Nl 7EO is C12-15 alcohol ethoxylate 7EO nonionic

Neodol® 25-7 (ex Shell Chemicals).

LAS acid is C12-14 linear alkylbenzene sulphonic acid.

Prifac® 5908 is saturated lauric fatty acid ex Croda.

Empigen® OB is amine oxide ex Huntsman

SLES 3EO is sodium lauryl ether sulphate with 3 moles EO.

Dequest® 2010 is HEDP (1 -Hydroxyethylidene -1 ,1 ,-diphosphonic acid). EPEI is Sokalan HP20 - ethoxylated polyethylene imine

cleaning polymer: PEI(600) 20EO ex BASF.

SRP is Texcare SRN170 polyester soil release polymer ex

Clariant.

Mannanase is Mannaway® 4.0L, a mannanase enzyme ex Novozymes.

Pectate Lyase is Xpect® 1000L, a Pectate lyase enzyme ex Novozymes

Cellulase is Endolase® 5000L, a cellulase ex Novozymes.

Amylase is Stainzyme 12L, an amylase ex Novozymes.

Protease is Relase® Ultra 16XL ex Novozymes.

Preservative is Proxel GXL

Colorant is a mixture of Patent Blue and Yellow dyes,

Perfume is free oil perfume Empigen® BB is an alkyl betaine ex Huntsman (Coco dimethyl

carbobetaine).

NaOH is 47% sodium hydroxide solution. For stability testing "Pass" means a stable and isotropic liquid was maintained for at least 12 weeks storage. "Fail" means that material had precipitated or the liquid had split into distinct phases. The target level of inclusion of HEDP for stain removal and cleaning is over 2.5 wt% in these liquids. Comparative Example A - using NaOH to adjust pH to 6.5

HEDP was added at gradually increasing amounts to the liquid composition given in table 1 and the pH adjusted to 6.5 with sodium hydroxide. The stability is shown in table 2.

Table 1 - Benchmark compositions: NaOH and Empigen BB

Table 2 - Stability of NaOH and Empiqen BB compositions with HEDP

HEDP crystallizes out of the liquid at levels of NaOH greater than 0.3 when the carbobetaine Empigen BB used. Insufficient HEDP can be included in this acidic modification of the liquids disclosed in WO09153184.

Example 1 - using MEA to adjust pH to 6.5

Table 3 - Modified compositions: MEA and no amphoteric

Table 4 - Stability of MEA neutralized compositions

With the carbobetaine removed and use of MEA to neutralise the LAS acid, high enough levels of HEDP may be successfully incorporated in this isotropic liquid with 0.75% fatty acid at pH 6.5.

Example 2 - using MEA with amine oxide

Table 5 - Modified compositions: MEA and Empiqen AO

Table 6 - Stability of MEA neutralized Empiqen OB compositions with HEDP

Conclusion: even increasing the fatty acid up to 1 .5 (and thus the amount of MEA needed for neutralization - 1 wt% fatty acid requires 1 .91 wt% MEA) still gives a stable isotropic liquid with the required level of HEDP for effective cleaning.