AU5558698A

AU5558698A - Improvements relating to aqueous light duty cleaning compositions

Info

Publication number: AU5558698A
Application number: AU55586/98A
Authority: AU
Inventors: George Kerr Rennie; John William Harold Yorke
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1996-12-12
Filing date: 1997-11-21
Publication date: 1998-07-03
Anticipated expiration: 2017-11-21
Also published as: WO1998026036A1; AU721830B2; BR9714139A; HUP0000563A2; AR009661A1; CA2270374A1; ZA9710550B; GB9625884D0; HUP0000563A3; EP0944703A1

Description

IMPROVEMENTS RELATING TO AQUEOUS LIGHT DUTY CLEANING COMPOSITIONS

Technical Field

The present invention relates to aqueous light duty cleaning compositions and will be described herein with particular reference to hand dishwashing liquids.

Background of the Invention

Commercial hand dishwashing compositions typically comprise, as the principal surfactant component, one or more surfactants selected from a relatively small group. In particular, principal surfactants are typically selected from amongst primary alcohol sulphates (also known as primary alkyl sulphates) , secondary alkane sulphonates, linear alkyl benzene sulphonate, alkoxylated alcohols and alkyl ether sulphates. It is also known to use polyol derived surfactants such as alkylpolyglucosides, glucosamides and other sugar based surfactants, as well as alkyl glyceryl derivatives. Typically, hand dishwashing compositions are not structureds by the presence of a lamellar phase.

In addition to these principal surfactants it is commonplace for compositions to comprise a so-called 'foam-booster', selected from a ine oxides, alkanolamides (particularly the mono and di ethanolamides and isopropanolamides) and other nitrogen-based surfactant compounds, including poly-hydroxy amides and betaines . Many compositions are known which make use, as the principal surfactant, of ethoxylated alcohol nonionic surfactants of the general formul :

R-0- (CH₂-CH₂0)_n-H

where R is typically C8-C18 alkyl and n is typically 1-14, or the related alkyl ether sulphates of the general formula:

R-0-(CH₂-CH₂0)_n-S0₃ ^"

where R is again alkyl and n is typically 1-5.

In typical commercial formulations, a large proportion (often some 80%wt) of the total surfactant system comprises ether sulphates, with the balance of the actives comprising one or more foam-boosters. The overall active concentration on product typically varies from around 20% for 'economy' brands to around 40% for 'concentrated' products. Lower concentrations, down to 2% surfactant are known as are higher concentrations, up to 70% surfactant. The product comprising very high levels of surfactant are still aqueous, but may be in the form of pastes, gels or bars.

A common problem in hand dishwashing is encountered when the soil removed from the articles being washed contains a significant level of fat, grease or other oily matter. Under bowl-wash conditions, typical in use levels of surfactant of 0.04%wt are sufficient to remove grease from the articles and suspend it as droplets, however, coalescence of these droplets may occur to produce large and visible bodies of fatty material. These bodies of material are unsightly and can be redeposited on the articles being washed, the hands of the user or the bowl surface. The presence of visible droplets of fatty material may cause the user to believe that the wash liquor is spent and lead the user to discard the wash liquor causing unnecessary further use of products and release of surfactant into the environment.

As will be appreciated, the process of coalescence is largely the opposite of the processes of spontaneous grease removal which occurs under washing conditions. It has been found that with current commercial products there is an inverse relation between the rate of spontaneous grease removal and rate of grease droplet coalescence. Thus, with the above-mentioned products, manipulation of the surfactants in the formulation can generally only have a limited effect on the problem of coalescence without reducing the overall effectiveness of the formulation.

Attempts have been made to prevent redeposition of fatty soils by the use of polymeric surfactants. EP 0221774 (P&G, 1986) discloses the use of hydrophobic/hydrophilic linear block copolymers . Similar compositions are disclosed in EP 222557 (P&G, 1987) .

EP 0346995 and EP 0719857 (Unilever, 1988) : disclose a large number of formulations which include 'deflocculating polymers'. All are lamellar dispersions as the function of the polymer is to stabilise the lamellar dispersion against phase separation.

EP 0415698 (Unilever 1989) : discloses fabric softening compositions which comprise an aqueous base and one or more fabric softening components. Example II of this document discloses a composition which comprises 30% quaternary- fabric softener, 1-1.5% nonionic and 0.1-0.2% of a polymer. Example X of this document discloses compositions with various quats, 0.5% polymer and 1.5-2.0%. Despite the work in this field, there remains a need for formulations which retain their properties in terms of grease removal while improving their ability to prevent coalescence of removed grease. As light duty cleaning formulations are largely unbuilt, it is important that these properties are maintained in the presence of calcium ions, such as will be introduced into the formulation upon dilution with water to form a washing liquor.

Brief Description of the Invention

We have determined that coalescence of oil droplets during the dishwashing process can be significantly retarded, without detriment to the spontaneous grease removal properties of the formulation, by the presence of selected polymers having a hydrophilic backbone and hydrophobic side chains.

Accordingly, the present invention provides a non-lamellar, unbuilt, aqueous, light duty cleaning composition comprising:

a) 2-70%wt of surfactant selected from the group comprising: nonionic surfactant, a complex of anionic surfactant and zwitterionic surfactant, a complex of anionic surfactant and amphoteric surfactant and mixtures thereof, and,

b) 0.02-7%wt of a polymer, said polymer comprising a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil-soluble side chain.

wherein the ratio of polymer to surfactant falls in the range to 1:100-1:10.

A second aspect of the present invention provides a dishwashing process which comprises the step of treating the surfaces of the dishes with a composition as described above in neat or dilute form.

A third aspect of the present invention relates to the use of 0.02-7%wt of a polymer, comprising a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil-soluble side chain as an oil-coalescence inhibitor in a non-lamellar, unbuilt light duty cleaning composition comprising 2-70%wt of surfactant selected from the group comprising: nonionic surfactant, a complex of anionic surfactant and zwitterionic surfactant, a complex of anionic surfactant and amphoteric surfactant and mixtures thereof, wherein the ratio of polymer to surfactant in said light duty cleaning composition falls in the range to 1:100-1:10.

A fourth aspect of the present invention provides a non- lamellar, light duty cleaning composition which comprises surfactant selected from the group comprising: nonionic surfactant, a complex of anionic surfactant and zwitterionic surfactant, a complex of anionic surfactant and amphoteric surfactant and mixtures thereof, and, a polymer, said polymer comprising a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil-soluble side chain wherein the ratio of polymer to surfactant falls in the range to 1:100-1:10 and the extent of coalescence as defined herein is less than 20%.

Without wishing to limit the invention by reference to any theory of operation, it is believed that the oil-soluble hydrophobic side chains of the polymer partition into oil droplets, while the hydrophilic backbone remains in the waterphase to stabilise the droplets against coalescence through a combination of steric hindrance and electrostatic repulsion. The particular combinations of surfactants described above comprise non-charged surfactants and potentially surfactant complex-forming systems in which the charge of the anionic surfactant is in part shielded by the amphoteric or zwitterionic surfactant, this prevents significant complex formation between the anionic surfactant and the polymer which would otherwise inhibit the action of the polymer.

Detailed Description of the Invention

Physical Form:

As noted above the compositions of the present invention are non-lamellar. Preferably, the compositions of the present invention are single phase, isotropic systems.

Compositions are preferably pourable liquids. The viscosity of liquid compositions according to the invention is preferably in the range 200-300 cP at a shear rate of 21 reciprocal seconds as measured at a temperature of 25 Celcius using a Haake MV cup and bob. It is also believed possible to formulate products as pastes or gels or as powders to be dissolved in water prior to use.

Surfactant:

As noted above, it is considered important that the surfactant should comprise either nonionic surfactant or a surfactant blend which has the potential to form an anionic/ zwitterionic or anionic/amphoteric surfactant complex.

Of the nonionic surfactants both alkoxylated alcohols and alkyl poly glucoside (APG) have been found particularly suitable for use in the compositions of the present invention. Preferably, compositions according to the present invention comprise

a) 2-70%wt of surfactant, said surfactant comprising at least 5% on total surfactant of an alkylpolyglycoside, and,

wherein the ratio of polymer to surfactant falls in the range to 1:100-1:10.

Preferred levels of APG are such that the composition comprises 30-40%wt of APG on total surfactant.

Preferred APG's have an alkyl chain comprising C__.-i₆ and it is preferred that more than 50%wt of the APG present in the compositions of the invention comprises a Cι_ι₄ alkyl APG and that the majority of the remaining APG is C₈-Ci₈. The preferred degree of polymerisation is 1.1-1.6, more preferably 1.3-1.5. Suitable materials include GLUCOPON 600 (RTM ex HENKEL) .

It is believed that APG's with average alkyl chain lengths in the range C12-C16 show rapid fat removal from surfaces. The APG preferably consists predominantly of material with alkyl chain lengths C12-C14 and DP 1.3-1.5 as these are believed to show the most rapid fat removal from surfaces. In embodiments of the present invention compositions which comprises APG show exceptionally low levels of fatty coalescence.

Preferred alkoxylated alcohol, nonionic surfactants are those with an HLB of 11-15 as these, in combination with the polymers, show particularly low rates of coalescence. Of the anionic surfactants primary alkyl sulphate and/or alkyl ether sulphate are preferred components of compositions according to the invention.

Embodiments of the invention comprise a mixture of primary alkyl sulphate and alkyl ether sulphate which comprises:

(1) 5-45%wt on total surfactant of primary alkyl sulphate comprising essentially no ethoxylated material, and

(2) 5-40%wt on total surfactant of a mixture of primary alkyl sulphate and ethoxylated primary alkyl sulphate,

the ratio of ethoxylated to non-ethoxylated primary alkyl sulphate in (2) being such that the overall ratio of ethoxylated to non-ethoxylated primary alkyl sulphate (AES) in (1) + (2) is 0.5-2.5.

It is believed that the above constraint can be met by using primary alkyl sulphate (PAS) as (1) and technical grade PAS- 3EO as (2) . It is known that materials such as technical grade ethoxylated PAS with low ethoxylation numbers comprise significant levels of unethoxylated PAS, i.e. a material equivalent to (1). It is believed that PAS-1EO can replace both (1) and (2) and therefore comprise substantially all of (a) in the above-mentioned description of the invention.

Preferred levels of the mixture of PAS and AES are such that the mixture comprises equal weights of the two components, preferably each present as 30-40% of the total surfactant present. In particularly preferred embodiments of the invention the average ethoxylation value of the mixture of primary alkyl sulphate and alkyl ether sulphate is 0.75-1.25 EO. The preferred average ethoxylation level in the alkyl ether sulphate component taken alone is 2-4 EO .

The alkyl chain length of the PAS falls in the range C₈-Cι₆. Preferably the PAS has a C_i2-Cι₃ average alkyl chain length.

Preferably the PAS is substantially linear. Suitable materials include DOBANOL-23S [RTM] (ex. Shell) .

Preferably the alkyl ether sulphates are materials of the general formula:

R₁-(OCH₂CH₂)_m-S0₃ ^"

wherein Ri is linear or branched, C₈ to Cι₈ alkyl. More preferably the alkyl chain length of the AES falls in the range C₈-Ci₆. Preferably the AES has a Cι₂-Cι₃ average alkyl chain length. Preferably the AES is substantially linear. Suitable materials include DOBANOL-23-3S (RTM, ex SHELL) .

Preferred amphoteric and zwitterionic surfactants include betaines and/or amine oxides. Betaines are preferred to amine oxides for environmental reasons .

When present, the preferred level of betaine in the compositions according to the invention is around 5%wt on surfactant. Amidobetaines are particularly preferred.

Preferred amido betaines are propyl amido betaines of the general formula : R. CONH . CH₂. CH₂. CH₂. N⁺ (R₆R₇ ) . CH₂COO^~

wherein R is straight or branched C₈ to Cι₈ alkyl,

R₆ is Ci to C₃ alkyl or Ci to C₃ hydroxyalkyl , and

R₇ is Ci to C₃ alkyl or C_x to C₃ hydroxyalkyl; Preferably, the betaine has an alkyl chain length (R) of Cι₂_Cι ,

Suitable materials include TEGO BETAINE L5351 (RTM ex. Goldschmidt) .

Polymers :

As mentioned above, the polymers employed in the present invention have a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil-soluble side chain .

We have determined that cationic polymers increase the coalescence rate. It is believed that this is due to increased bridging between negatively charged oil droplets. Relatively uncharged polymers such carboxy-methyl cellulose and the GEROL (TM) class of polymers had no significant effect on coalescence.

Polymers having a negatively charged backbone are preferred. We have determined that these anionic charged polymers had the largest beneficial effect, slowing the rate of coalescence significantly. Typical backbones are polycarboxylate polymers formed as polymers of one or more of acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid, aconitic acid, citraconic acid. Polymers having a nonionic backbone, such as those derived from vinyl methyl ether, vinyl alcohol, acrolein, allyl alcohol and vinyl acetic acid are also envisaged as being suitable for putting the invention into effect.

Preferably the backbone is essentially linear, more preferably, branching in the backbone is limited such that the main chain of the backbone contains over 75% of its mass. Preferably the hydrophobic side chains are saturated and/or unsaturated alkyl chains having from 5-24 carbon atoms, preferably 6-18 carbon atoms, most preferably 8-16 carbon atoms,

Preferred polymers are those described in US 5147576. One particularly preferred polymer is that available in the marketplace as Narlex DC1 (TM, ex. National Starch)

Optional Components and Minors :

Hydrotropes are optional components. It is preferred that the level of hydrotrope is no more than 20% of the total surfactant content on product, e.g. for a product containing 20% surfactant, the hydrotrope level should preferably be less than 4% on product . Where hydrotropes are required they are preferably selected from conventional hydrotrope materials including one or more of lower alkanols, alkaryl sulphonates, including xylene sulphonates and/or ureas . Higher levels of hydrotrope are required if the surfactant actives present are of low quality.

Magnesium is an optional component of the formulations according to the present invention. It is believed that the presence of magnesium boosts the detergency of the anionic surfactants present in the formulation. Preferred magnesium levels are equivalent to 2-14% as MgSO₄.7H0. Magnesium may be present as the counter ion for the surfactant or be added.

Preferably, other electrolytes can be present at levels of 0.1-5% by weight of the overall composition. Particularly preferred amongst the electrolytes are alkali metal halides, carbonates, bicarbonates and sulphates. Of these, the most preferred electrolyte is sodium chloride. Sodium chloride is conveniently present at a level of 0.1-5%, as a viscosity modifier. Ammonium salts may be present. The preferred electrolyes for grease removal are magnesium and potassium ions .

Among other, inessential, ingredients which may also be used in compositions according to the present invention are opacifiers (e.g. ethylene glycol distearate) , thickeners (e.g., guar gum), antibacterial agents (e.g. formaldehyde or Bronapol (TM) ) , anti- tarnish agents, weak metal chelators (e.g. citrates, glycinates) , perfumes, abrasives (e.g. calcites and dolomites) and dyes. When magnesium is present, the use of strong metal chelating agents with a high affinity for magnesium is discouraged as these will reduce the benefits associated with the presence of magnesium.

Compositions according to the present invention can further comprise a solvent, preferably, when present, at level of l-15%wt on product, more preferably at a level of 2-7% on product .

Preferably, any solvent present 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.

Most preferably the solvent is either a glycol ether or a C₂-C₅ alcohol solvent.

Particularly 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 in the marketplace both as 'Butyl Digol ' [RTM] or 'Butyl Carbitol' [RTM]).

A further inessential component is alkylene glycol, typically present at a level of 0-10% on product, irrespective of the overall surfactant concentration. Propylene glycol is particularly suitable as a hydrotrope and/or viscosity modifier and while it is typically present in hand dishwashing compositions known in the art it may be dispensed of in compositions according to the present invention.

Preferred compositions according to the present invention comprising 15-50% surfactant on product are formulated such that they comprise, on surfactant, :

a) 50-70%wt of a mixture of primary alkyl sulphate and alkyl ether sulphate, wherein the average ethoxylation value of the mixture is 0.5-2.5,

b) 2-8%wt of a betaine, an amine oxide or a mixture of betaine and amine oxide, and,

c) 25-45%wt of an alkylpolyglucoside surfactant.

Particularly preferred compositions according to the present invention comprise 10-50%, preferably 15-35% surfactant on product, which surfactant comprises, on total surfactant:

a) 30-40%wt PAS having a Cι₂-ι₃ average alkyl chain length,

b) 30-40%wt AES having a Cι₂-ι₃ average alkyl chain length and an ethoxylation value of 2-4, c) 30-40%wt APG having a C₁₂-₁₄ average alkyl chain and a degree of polymerisation of 1.2-1.5, and,

d) 2-8%wt of an amido betaine having a C₁₂-₁4 average alkyl chain .

Preferred total compositions, as aqueous solutions, comprise:

a) 10-25%wt PAS/AES mixture, preferably sodium lauryl ether sulphate 1EO (MMW 339, C₁₂ 38-48%, C_i3 52-62%),

b) l-3%wt betaine, preferably lauryl amido propyl betaine (MMW 342, C12 95%) ,

c) 9-13% APG based on a natural fatty alcohol (C₁₂-C₁₄) having a degree of polymerisation of 1.4 (GLUCAPON 600CS UP is a suitable material)

d) 2-10%wt ethanol,

e) l-3%wt sodium cumeme sulphonate or other anionic hydrotrope

f) 0.1-0.5%wt polycarboxylyic acid, preferably citric acid,

g) >1% dyes, animicrobial agents (preferably including formaldehyde) .

i) 0.02-7%wt polymer having a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil- soluble side chain (NARLEX DC1 is a suitable material) .

In particularly preferred embodiments of the present invention the extent of coalescence is less than 20% when measured as follows: emulsions of olive oil in water were prepared with a phase ratio of 20:80 of the oil phase to the water phase, using a jet homogeniser (ex. LabPlant) at lOOpsi (7kg/m²) to obtain an emulsion with reproducible droplet sizes in the 1-10 micron range in a water phase which is a 0.6%wt active solution obtained by dilution of a light duty cleaning composition which comprises surfactant selected from the group comprising: nonionic surfactant, a complex of anionic surfactant and zwitterionic surfactant, a complex of anionic surfactant and amphoteric surfactant and mixtures thereof, and, a polymer, said polymer comprising a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil-soluble side chain, wherein the ratio of polymer to surfactant falls in the range to 1:100- 1:10: the extent of coalescence being determined after centrifugation of 10ml samples in graduated centrifuge tubes for 800 mins at 2000rpm, under conditions so as to produce an acceleration of 895g.

In order that the present invention may be further understood it will be described hereinafter by way of examples and with particular reference to the accompanying figures wherein:

Fig 1: shows a plot of the relation between the percentage of coalescence which occurs under the conditions specified below and the time taken to remove the grease from the Petri-dish using the method specified below.

Fig 2 : shows a plot of the relationship between the volume of coalescence which occurs under the conditions specified below and the zeta potential as defined below.

Fig 3: shows the effect of increasing water hardness on compositions in the presence of two different polymers. Fig 4: shows the effect of changing the polymer type on the rate of coalescence in centrifuge experiments as compared with a control .

Fig 5: shows the effect of changing the properties of the nonionic on the rate of coalescence both in the presence of polymer DC1 and otherwise.

Examples

In the following examples the polymers used are identified as follows :

Exp 2075/2072 Acrylic acid/dimethyldiallylammonium chloride: (ex. ALCO /National Starch)

Alcosperse 240 Acrylic acid/methylmethacrylate sulphonate:

(ex. ALCO (National Starch)

SCMC Sodium carboxy methy cellulose (ex Aldrich)

Gerol PEJ 594 Ethylene glycol/terephthallic acid sulphonate: (ex. Rhone-Poulenc)

TEPA E024 Tetraethylenepenta ine/ethylene oxide copolymer (prepared in house)

Exp 2289 Acrylic acid/methylmethacrylate sulphonate (ex. ALCO /National Starch)

CP5 Acrylic acid/maleic anhydride: (ex BASF)

DC1 Sodium acrylate/laurylmethacrylate: (ex. ALCO /National Starch) The names given in the left-hand column are believed to be trademarks. Of these polymers, only the last, 'DC1' is one which comprises a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil-soluble side chain.

The surfactants used in the following examples are identified as follows:

APG Akylpolyglycoside (Glucopon 600 (RTM) ex Henkel) .

APB Cocoamidopropylbetaine (Tegobetaine ex Goldschmidt )

LES Lauryl 3EO suphate (Dobanol 23 /3s [TM] ex Shell)

PAS Primary alkyl sulphate (Dobanol 23s/30 [TM] ex Shell)

Marlipal 013/30 Ethoxylated nonionic with Cll-13 alkyl and an average of 3EO (ex Huls) . Marlipal is believed to be a trademark.

Dobanol 91-5 Ethoxylated nonionic with C9-11 alkyl and an average of 5EO (ex Shell). Dobanol is a trademark.

Marlipal 013/80 Ethoxylated nonionic with Cll-13 alkyl and an average of 8EO (ex Huls) . Example 1 ; Relation between extent of coalescence and rate of grease removal, and effect of calcium.

In the following experiment rate of grease removal was determined in glass Petri dishes which were coated with fat ('Kilverts' (TM) lard) and the time taken to remove the fat under standard conditions (50 Celcius, 0.04% AD) was determined by the following method:

200g of fat was weighed into a beaker and heated slowly to 50 ± 2°C until melted. 0.4g ( 0.2% w/w) of dye, eg FAT RED 7B, was transferred to the fat with stirring and temperature increase to 60 ± 2°C, stirring was continued until all the dye has dissolved (~ 30 minutes ) . An alternative fat should be used if the fat available contains significant quantities of emulsifiers as the presence of these components will alter the results.

Each petri dish had a cross marked on it centrally using permanent ink. Petri dishes were placed in a clean oven at 45 ± 2°C for 5 minutes, removed from the oven and filled with 5mls of the fat (still maintained at 60 ± 2°C ) ensuring uniform coverage. The dishes were left to cool at room temperature over a period of l%-2 hours before use.

500mls of test solution of products A-E as described below, was prepared at the desired concentration (typically 0.04%AD, e.g. lgm/l^t of a 40% AD concentrate) using water of a specific hardness (typically 5, 12 or 24 deg FH) and heated to 50°C in a water bath. The hot test solution was poured into a large beaker (e.g. 2L) containing a layer of glass beads as insulation and minimising the volume of foam produced and placed back in the waterbath, the temperature being maintained at 50C. The test petri dish was added; time keeping was started as soon as the dish was submerged in the test solution. At the point at which the solution broke through to the glass surface on the base of the petri dish the time was recorded. The time at which the fat in each quadrant was fully removed was also recorded. While a tiny amount of small fatty speckles may have been left on the dish: where these covered a negligible fraction of the base, they were be ignored.

Emulsions of olive oil in water were prepared with a phase ratio of 20:80 of the oil phase to the water phase, using a jet homogeniser (ex. LabPlant) at lOOpsi (7kg/cm²) to obtain an emulsion with reproducible droplet sizes in the 1-10 micron range .

The water phase used, was a 0.6%wt active solution obtained by dilution of the compositions A-E as listed in tables la and lb below.

Table la

Table lb

Typical droplet sizes for products A and B are given below in table lc. Concentrations in table lc are given on product not on surfactant. D[4,3] and D[3,2] are in microns.

Table lc

The extent of coalescence which occurs in the presence of the formulations used was determined after centrifugation of 10ml samples in graduated centrifuge tubes for 800 mins at 2000rpm, under conditions so as to produce an acceleration of 895g. The volume of coalesced oil was measured to obtain an indication of the degree of coalescence expressed as a number in ml.

Measurements were also performed to determine the so-called ¹ zeta-potential ' of the olive oil droplets in the surfactant solutions (at 0.6%wt). The zeta potential is the potential at the plane of shear or slip, i.e. the plane which separates water of hydration from free water. Zeta potential was measured using a Malvern Zetasizer (TM) following the instructions supplied with it.

Figure 1 shows a plot of the relationship between the percentage of coalescence (C%) which occurs under the conditions specified above and the time (T) taken to remove the grease from the Petri-dish using the method specified above. Experiments were performed in 12 FH water.

Figure 2 shows a plot of the relationship between the volume of coalescence (Cvol) which occurs under the conditions specified above and the zeta potential (zeta) using the method specified above. Experiments were performed both in 12 FH water.

In Figs 1. and 2. markers at the heads of the arrows include the added polymer CP5, those at the tail do not. The products used are specified by the letter used to identify them in tables la and lb.

It can be seen that in formulations which do not contain polymer there is a clear inverse relation between the extent of coalescence and the rate of removal of fat: i.e. as the ability to remove fat increases, the formulations lose the ability to effectively hold this fat in solution. Figure 2. Shows the effects in terms of the zeta potential, in 12° FH water: it can also be seen that there is a clear relation between the extent of coalescence and the zeta potential.

It can also be seen from Fig 1. that upon the addition of the CP5 polymer there is a significant change in the properties of the formulations, and all show some improvement in the rate of coalescence, i.e. a reduction in the formation of large bodies of oil.

Figure 3. shows the effect of increasing water hardness on composition E in the presence of CP5 and DC1 polymers. Experiments were performed in both 12 and 24 FH water, using product E at a surfactant concentration of 0.6g/l. The polymer concentration in g/1 is plotted against the volume of oil coalesced from the emulsion after spinning at 2000 rpm for 800 minutes .

From figure 3, it can be seen that increased water hardness (to 24° FH from 12° FH) caused the beneficial effects of CP5 to be lost. In 12°FH, CP5 reduced coalescence from about 0.8cm³ coalesced oil to less than 0.2cm³ after 800 mins spinning. In 24°FH though, addition of CP5 gave no improvement. It is believed that this is due to precipitation of the polymer with calcium ions. Water hardness did not, however, appear to affect the performance enhancement obtained with DC1, which., when present at a sufficiently high level, reduced coalescence to below 0.2cm³ regardless of water hardness. Example 2 : Comparison with other polymers:

Figures 4a and 4b show the effect of changing the polymer type on the rate of coalescence in the centrifuge as compared with the control in which the waterphase of the emulsion was derived from E as described above. In these experiments, the concentration of surfactant was 0.6g/l and where polymer was present it was present at a level of 0.075g/l. The control was an emulsion in which the waterphase was derived directly from E and did not contain any polymer.

In the figure, the volume of oil (Cvol) coalesced at a given time (t) is plotted. Soft water (12 FH) was used.

It can be seen from figures 4a and 4b that the polymers DC1 and CP5 have the most marked effects on the stability of the emulsion. The addition of these polymers significantly reduces the rate of coalescence of the oil droplets. It can also be seen that many of the polymers used in comparative examples actually promoted the coalescence of the oil droplets as compared with the rate seen in the control

Example 3; Comparison with other surfactant systems:

Table 2. below, shows the volume of oil coalesced after 800min as described above in the presence of simple surfactant systems. The systems have a total surfactant concentration of 0.6gm/litre and are 50/50 mixtures of the two surfactants found by reading down or across the table. Good performance is generally associated with an oil volume coalesced of 0.2ml, or less. Table 2

Figures shown in bold and underlined in table 2 indicate formulations in which there is an improvement in the stability of the oil droplets in the presence of the polymer. In the absence of polymer, it can be seen that the presence of nonionics and amphoterics is beneficial, but that poor results are generally obtained with PAS a strongly charged anionic surfactant. LES, a less strongly charged anionic surfactant, shows some improvement over PAS . In the presence of the DCl polymer, APG and APB containing systems can be improved to give very low levels of coalescence, and in general it can be seen that the addition of the DCl polymer never causes a significant increase in the coalescence, while more often than not, improves the coalescence score.

Example : Further comparisons with other surfactant systems

Figure 5 shows the effect of changing the properties of the nonionic on the rate of coalescence both in the presence of polymer DCl and otherwise. Coalescence was measured as described above, i.e. by the centrifuge method using 24 FH water (i.e. moderately hard) to prepare the waterphase of the emulsion.

The surfactants used are a series of ethoxylated nonionics with increasing degrees of ethoxylation. This increase in ethoxylation has the effect of increasing the hydrophile/lipophile balance of the surfactant.

From the results presented in figure 5, it can be seen that under these hard water conditions, polymer DCl brings about an improvement in terms of retarding coalescence in all cases, across the whole range of nonionic tested, but that the lowest rates of coalescence are found with the most highly ethoxylated nonionics.

Claims

1. A non-lamellar, unbuilt, aqueous, light duty cleaning composition comprising:

wherein the ratio of polymer to surfactant falls in the range to 1:100-1:10.

2. Composition according to claim 1 comprising 2-70%wt of surfactant, wherein said surfactant comprises at least 5% on total surfactant of an alkylpolyglycoside.

3. Composition according to claim 1 wherein the polymer backbone is a polycarboxylate polymer formed as polymers of one or more of acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid, aconitic acid, citraconic acid.

4. Composition according to claim 1 wherein the at least one hydrophobic side chain comprises saturated and or unsaturated alkyl chains having from 5-24 carbon atoms. Composition according to claim 1 comprising 15-50% surfactant on product which comprises, on surfactant, :

a) 50-70%wt of a mixture of primary alkyl sulphate and alkyl ether sulphate, wherein the average ethoxylation value of the mixture is 0.5-2.

5,

c) 25-45%wt of an alkylpolyglucoside surfactant.

6. A dishwashing process which comprises the step of treating the surfaces of the dishes with a composition according to any one of claims 1-5 in neat or dilute form.

7. The use of 0.02-7%wt of a polymer, comprising a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil-soluble side chain as an oil-coalescence inhibitor in a non-lamellar, unbuilt, light duty cleaning composition comprising 2-70%wt of surfactant selected from the group comprising: nonionic surfactant, a complex of anionic surfactant and zwitterionic surfactant, a complex of anionic surfactant and amphoteric surfactant and mixtures thereof, wherein the ratio of polymer to surfactant in said light duty cleaning composition falls in the range to 1:100-1:10.

8. A non-lamellar, light duty cleaning composition which comprises surfactant selected from the group comprising: nonionic surfactant, a complex of anionic surfactant and zwitterionic surfactant, a complex of anionic surfactant and amphoteric surfactant and mixtures thereof, and, a polymer, said polymer comprising a negatively charged or neutral hydrophilic backbone with at least one hydrophobic and oil-soluble side chain, wherein the ratio of polymer to surfactant falls in the range to 1:100-1:10 and the extent of coalescence as defined herein is less than 20%.