GB2166149A - Thickened liquid detergent compositions - Google Patents

Abstract

Liquid detergent compositions based on dialkyl sulphosuccinates are thickened with a blend of two hydrophilically substituted polysaccharides, one of higher molecular weight that the other. The preferred polymers are hydroxyethyl cellulosed. The use of two polymers rather than one gives improved cloud point and room temperature clarity, as well as a better viscosity profile.

Description

SPECIFICATION Detergent compositions The present invention relates to liquid detergent compositions containing salts of dialkyl esters of sulphosuccinic acid (hereinafter dialkyl sulphosuccinates) as a principal ingredient, and thickened with hydrophilically substituted cellulosic polymers.

The use of dialkyl sulphosuccinates as active ingredients in liquid detergent compositions is disclosed inter alia in GB 1 429 637, GB 2 108 520A, GB 2 130 235A, GB 2 130 236A and GB 2 130 238A (all Unilever). Dialkyl sulphosuccinates are highly efficient highly-foaming detergent-active agents but when used in liquid detergent compositions tend to give products having rather low viscosities. Even when concentrations of detergent-active material as high as 60 to 70% by weight are present viscosities may be 50 cp or less at ambient temperature, while consumer expectations in the UK at least are for products having viscosities in the 200-500 cp range. High viscosity is apparently equated to some extent with strength and efficiency.

GB 2 140 024A (Unilever), to be published on 21 November 1984, discloses liquid detergent compositions based on dialkyl sulphosuccinates, containing 2-60% of detergent-active material and 0.05-5% of a water-soluble polymer selected from polysaccharides having hydrophilic substituents, xanthan gums and synthetic polymers carrying carboxyl substituents in salt or amide form. The polymers simultaneously increase product viscosity and enhance foam stability. The disclosure is directed particularly to compositions having relatively low active detergent contents: 2-30%, preferably 2-20%, by weight. A preferred class of polymers is constituted by celluloses having hydrophilic substituents, particularly hydroxyethyl groups. These are exemplified by the Natrosols (Trade Mark) ex Hercules, especially the 250 HR and 250 HHR grades.Compositions containing active detergent levels ranging from 5.5 to 21% (dialkyl sulphosuccinate levels of 5.5 to 14%) and Natrosol levels ranging from 0.2 to 0.9% are described.

Our copending Application No. 84 12048 and our copending Application of even date (Case C.3050) are concerned with concentrated liquid detergent compositions (60-80% active matter) based on dialkyl sulphosuccinates, alkyl ether sulphates and optional nonionic sulphosuccinates, alkyl ether sulphates and optional nonionic surfactants. These compositions, containing relatively high levels of alcohol, tend to have low viscosities and may be thickened with certain selected polymers. According to Application No. 84 12048 only hydroxypropyl guars and polyethylene oxides are sufficiently soluble in these high-alcohol compositions, while according to our copending Application of even date hydrophilically substituted celluloses may also be used provided that they are incorporated by a particular processing route.

The present invention is based on a further development whereby liquid detergent compositions based on dialkyl sulphosuccinates are thickened by means of a mixture of at least two different hydrophilically substituted polysaccharides, one having a higher molecular weight than the other. This combination of polymers may be used to thicken compositions of both high and low active matter contents, to give products having good viscosity characteristics at both low and high shear rates which are clear at room temperature and have low cloud points.

Accordingly, the present invention provides a liquid detergent composition containing at least 2% by weight of an active detergent system comprising or consisting of at least one watersoluble salt of a C3-C12 dialkyl ester of sulphosuccinic acid, and further comprising from 0.05 to 2.0% by weight of a polymer mixture comprising (i) a first hydrophilically substituted polysaccharide, of which the Brookfield viscosity of a 2% aqueous solution at 25"C is less than 500 cp, and (ii) a second hydrophilically substituted polysaccharide, of which the Brookfield viscosity of a 2% aqueous solution at 25"C is at least 1000 cp, the weight ratio of (i) to (ii) being within the range of from 2:1 to 6:1.

The first polymer is of relatively low molecular weight while the second is of relatively high molecular weight, the viscosity of a dilute aqueous solution being used as a convenient indicator of molecular weight, in order to define and distinguish the two classes of polymer. The viscosity measurements are carried out in accordance with ASTM 2364, "Standard Methods of Testing Hydroxyethyl Cellulose", as described on pages 30-31 of the Hercules brochure "Natrosol Hydroxyethyl Cellulose: Physical and Chemical Properties", where details of spindle speeds and other conditions are set out.

Liquid detergent compositions thickened with hydrophilically substituted polysaccharides exhibit non-Newtonian, shear-thinning behaviour, the perceived viscosity decreasing as the applied shear is increased. The higher the molecular weight of the polymer used, the greater the departure from Newtonian behaviour; with low-molecular-weight polymers, however, inconveniently large amounts are required to give adequate thickening. A mixture of polymers of different molecular weight, provided the proportions are right, will give good viscosity properties over a wide range of shear rates. The present inventors have also found that the clarity of the compositions at room temperature, and their low temperature behaviour as evidenced by cloud points, can be favourably influenced by the choice of polymers and the ratio in which they are used.

The compositions of the invention contain as an essential ingredient a water-soluble salt of a dialkyl ester of sulphosuccinic acid, hereinafter referred to for simplicity as a dialkyl sulphosuccinate.

The detergent-active dialkyl sulphosuccinates used in the compositions of the invention are compounds of the formula I:

wherein each of R1 and R2, which may be the same or different, represents a straight-chain or branched-chain alkyl group having from 3 to 12 carbon atoms, preferably from 4 to 10 carbon atoms, and advantageously from 6 to 8 carbon atoms, and X, represents a solubilising cation, that is to say, any cation yielding a salt of the formula I sufficiently soluble to be detergentactive. The solubilising cation X1 will generally be monovalent, for example, alkali metal, especially sodium; ammonium; or substituted ammonium, for example, ethanolamine. Certain divalent cations, notably magnesium, are however also suitable.

The dialkyl sulphosuccinate component of the composition of the invention may if desired be constituted by a mixture of materials of different chain lengths, of which the individual dialkyl sulphosuccinates themselves may be either symmetrical (both alkyl groups the same) or unsymmetrical (with two different alkyl groups).

The alkyl groups R1 and R2 are preferably straight-chain or (in mixtures) predominantly straightchain.

Among dialkyl sulphosuccinates that may advantageously be used in the compositions of the invention are the C6/C8 unsymmetrical materials described and claimed in GB 2 105 325A (Unilever); the dioctyl sulphosuccinate/dihexyl sulphosuccinate mixtures described and claimed in GB 2 104 913A (Unilever); the mixtures of symmetrical and unsymmetrical dialkyl sulphosuccinates described and claimed in GB 2 108 520A (Unilever); and the C,/C8 and C6/C7/Ca dialkyl sulphosuccinate mixtures described and claimed GB 2 133 793A (Unilever).

The dialkyl sulphosuccinates are conveniently used in the form of their sodium salts.

The concentration of the dialkyl sulphosuccinate component in the whole composition is at least 2% by weight, and is preferably within the range of from 2 to 50% by weight, more preferably within the range of from 5 to 45% by weight.

Other detergent-active materials may also be present, as discussed below.

The second essential ingredient of the composition of the invention is a mixture of at least two different hydrophilically substituted polysaccharides of different molecular weights. Any suitable polysaccharides available with appropriate substituents and having appropriate molecular weights may be used. The preferred hydrophilic substituents are hydroxy (C2-C4) alkyl groups, and especially hydroxyethyl and hydroxypropyl groups. Non-hydrophilic substituents, for example, alkyl groups, may also be present.

The classes of polysaccharide of especial interest are the celluloses and the guars (galactomannans). Hydroxyethyl and hydroxypropyl celluloses are available in a wide range of molecular weights and appropriate grades are available for both the lower and higher molecular weight polymers used according to the present invention. Hydroxypropyl guars tend to be of higher molecular weight and are of interest for use as the second polymer in the compositions of the present invention.Some suitable commercially available polymers are listed in the following table: Trade Name Manufacturer Chemical type Methocel* Dow Hydroxypropyl ethyl J,K,E and F cellulose Natrosol* Hercules Hydroxyethyl cellulose Klucel* Hercules Hydroxypropyl cellulose Bermocoll* Berol Kemi Ethyl hydroxyethyl cellulose Jaguar* Meyhall Hydroxypropyl guar denotes Trade Mark Of these, the Natrosol series of hydroxyethyl celluloses is of especial interest. These are available in molar substitution levels of 1.8 (the 180 series) and 2.5 (the 250 series), each in a range of molecular weights.

The first, lower-molecular-weight polymer (i) is characterised by the Brookfield viscosity of a 2% aqueous solution at 25"C being less than 500 cp at 25"C, and preferably being within the range of from 150 to 400 cp. According to a preferred embodiment of the invention, this polymer (i) is a type G Natrosol, for example Natrosol 250 G or 250 GR. The Brookfield viscosity of a 2% aqueous solution of this grade at 25"C will typically be about 300 cp.

Type J and type L Natrosols may also be used, but are less preferred. These typically have Brookfield viscosities (2% aqueous solution, 25"C) of 20 and 14 cp respectively.

The second, higher-molecular-weight polymer (ii) is characterised by the Brookfield viscosity of a 2% aqueous solution at 25"C being least 1000 cp, preferably at least 2000 cp and advantageously at least 15000 cp. The corresponding figure for a 1% aqueous solution is advantageously within the range of from 1500 to 5000 cp. According to a preferred embodiment of the invention, the polymer (iii) is selected from Natrosols of types H, H4 and HH. The Brookfield viscosities of 1% aqueous solutions of these types at 25"C are approximately 1500-2500 cp, 2600-3300 cp and 3400-5000 cp respectively, and typical figures for a 2% aqueous solution are 30000, 50000 and 100000 cp respectively.

Natrosols of types MH, M and K may also be used, but are less preferred than types H, H4 and HH. These may typically have Brookfield viscosities (2% aqueous solution, 25"C) of 15000, 6000 and 2000 cp respectively.

According to another preferred embodiment of the invention, the polymer (ii) may be a hydroxypropyl guar. Examples of suitable commercial materials include Jaguar HP 8 and HP 60, of which the Brookfield viscosities (2% aqueous solution, 25"C) are typically in the 10000 to 100000 cp range.

The ratio of polymer (i) to polymer (ii) is very important in determining both optimum viscosity characteristics and product stability. This ratio is within the range of from 2:1 to 6:1, preferably from 3:1 to 5:1. Too high a level of polymer (II) can give haziness at room temperature and/or too high a cloud point, whereas too low a level of polymer (ii) gives too low a viscosity at low shear (20 s 1) Ratios of 4:1 and 5:1 are especially preferred.

It is of course possible to envisage the use of more than two types of polymer to give a desired balance of properties. The use of only two has the merit of simplicity and appears to be sufficiently flexible to allow the successful formulation of products having a wide range of active detergent levels.

The total polymer level is in the range of from 0.05 to 2.0% by weight, preferably 0.1 to 1.0% by weight.

As indicated previously, the composition of the invention may also contain one or more other detergent-active agents. A preferred second detergent-active agent is an alkyl ether sulphate.

These anionic detergents are materials of the general formula II R3-O-(CH2CH2O),-SO3X2 (II) wherein R3 is an alkyl group having from 10 to 18 carbon atoms and X2 is a solubilising cation, preferably alkali metal, ammonium, substituted ammonium or magnesium, desirably sodium or ammonium. The average degree of ethoxylation n preferably ranges from 1 to 12, more preferably from 1 to 8 and desirably from 1 to 5. In any given alkyl ether sulphate a range of differently ethoxylated materials, and some unethoxylated material (alkyl sulphate), will be present and the value of n represents an average. If desired, additional alkyl sulphate may be admixed with the alkyl ether sulphate to give a mixture in which the ethoxylation distribution is more weighted towards lower values.

The amount of alkyl ether sulphate present in the composition of the invention may range, for example, from 2 to 30% by weight, more preferably from 5 to 25% by weight.

It has been found that use of alkyl ether sulphate in ammonium or substituted ammonium salt form is advantageous in terms of low temperature stability of the product. Alkanolamine salts appear to be especially beneficial in this respect.

Dialkyl sulphosuccinate and alkyl ether sulphate are advantageously used together in a weight ratio of from 4:1 to 0.5:1, more preferably 2.5:1 to 1.5:1.

In addition to the alkyl ether sulphate, it may be desirable to include one or more nonionic surfactants in the composition of the invention, but it has generally been found that the amount of nonionic surfactant present should not exceed 30% by weight of the active detergent system.

A preferred level for the nonionic surfactant is from 5 to 25% by weight of the active detergent system.

The nonionic surfactant may advantageously be selected from the following classes: a) C,0-C18 alkyl di (C2-C3 alkanol)amides, preferably C12-C14 alkyl diethanolamides, for example, Empilan (Trade Mark) LDE and CDE ex Albright & Wilson and Ninol (Trade Mark) p 621 ex Stepan Chemical Company; and b) ethoxylated C8-C12 primary aliphatic alcohols, for example, Dobanol (Trade Mark) 91-8 ex Shell (Cg-Cll alcohol, 8 EO).

Mixtures of two or more nonionic surfactants selected from these classes may be used.

The diethanolamides of class (a) are especially preferred in that they give products having especially good low-temperature stability. Detergent compositions containing dialkyl sulphosuccinates, alkyl ether sulphates and diethanolamides are disclosed in GB 2 130 236A (Unilever).

The invention is of especial interest in connection with compositions having a high active matter content, for example, 50 to 80% by weight, and, in particular, the compositions described and claimed in our copending Application No. 84 12048. These compositions, having an active matter content of 60-80% by weight, contain dialkyl sulphosuccinate and alkyl ether sulphate in a weight ratio of from 4:1 to 0.5:1, an optional nonionic detergent in an amount not exceeding 15% by weight of the whole composition, at least 12% by weight of a C2-C3 alcohol, optionally up to 4% by weight of urea, and water, the alcohol to water ratio exceeding a certain value dependent on the active matter level.

These compositions are of relatively low viscosity and can be thickened with various polymers. Hydroxypropyl guars and polyethylene oxides can be incorporated directly, while, as described in our Application of even date (Case C. 3050), hydrophilically substituted celluloses can be included only if the compositions are made up by a particular method.The method in question comprises the following steps: (i) dissolving the cellulosic polymer in a quantity of water calculated to give the correct water level in the final composition, optionally in the presence of a part or the whole of the calculated quantity of the C2-C3 alcohol; (ii) if necessary, adding a further part, the remainder or the whole of the calculated quantity of the C2-C3 alcohol; (iii) mixing in the alkyl ether sulphate and the optional nonionic detergent, plus any C2-C3 alcohol still to be added; and (iv) mixing in the dialkyl sulphosuccinate.

A preferred procedure comprises the following steps: (i) dissolving the cellulosic polymer in a quantity of water calculated to give the correct water level in the final composition, (ii) when dissolution is complete, adding the calculated quantity of the C2-C3 alcohol; (iii) mixing in the alkyl ether sulphate and the optional nonionic detergent; and (iv) mixing in the dialkyl sulphosuccinate.

The polymer mix used in accordance with the present invention may be incorporated by this method. The polymers are dry-mixed and dissolved in water in stage (i), and the process then proceeds as for a single polymer.

This procedure may not be necessary for compositions having a lower active detergent level and/or a lower alcohol content. Under those circumstances polymer may be added last, until the desired viscosity is attained. When using the procedure given above, the optimum amount of polymer to be incorporated can first be ascertained by a series of trial and error experiments on small samples.

The invention is further illustrated by the following non-limiting Examples.

EXAMPLE 1 Compositions having the ingredients (weight %) shown in Table 1 were prepared by the preferred method described above.

The dialkyl sulphosuccinate was a C6/C8 mix as described in GB 2 108 520A (Unilever), prepared from 40 mole % n-hexanol and 60 mole % n-octanol as an 80% slurry by the method of our copending application No. 83 29074.

The alkyl ether sulphate was Dobanol (Trade Mark) 23-3A ex Shell, a sulphated ethoxylated (3EO) C12-C,3 oxo alcohol mixture, ammonium salt, as a 609e active matter composition contain ing 14% ethanol.

TABLE 1 - EXAMPLE 1 A B C D E F G H I Dialkyl sulphosuccinate 34 34 34 34 34 34 34 35 34 Alkyl ether sulphate 16 16 16 16 16 16 16 17.5 16 Coconut or lauric diethanolamide 8 8 8 8 8 8 8 9 8 Ethanol (total) 13 13 13 13 13 13 13 14 14 Perfume 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Natrosol 250 HHR - 0.2 0.35 - - - - - 0.15 Natrosol 250 MHR - - - 0.15 0.3 0.45 - - Natrosol 250 GR - - - - - - 1.0 0.75 0.75 Viscosity at 20 s-1 (cp) 32 142 210 76 166 169 506 364 585 Viscosity at 106 s-1 (cp) 32 100 154 63 126 185 365 274 353 Cloud point ( C) 0 +3 +5 -3 +2 0 +12 +8 +3 Clarity at room temperature clear clear clear clear clear clear clear hazy clear The coconut and lauric diethanolamides were Empilan (Trade Mark) CDE or LDE ex Albright & BR< Wilson, of approximately 100% active matter.

The figures given for ethanol content represent a total including that present in the dialkyl sulphosuccinate and the alkyl ether sulphate, plus added industrial methylated spirit.

The polymers used were three Natrosol hydroxyethyl celluloses as described previously: grades 250 HHR (relatively high molecular weight), 250 MHR (somewhat lower molecular weight), and 250 GR (relatively low molecular weight) Comparative Composition A represents a control system without polymer; the very low viscosity will be noted. In Comparative Composition B 0.2% by weight of the highest molecular weight polymer Natrosol 250 HHR was incorporated but the viscosities rose to only 142 cp (low shear) and 100 cp (high shear) and the cloud point also rose. Increase of the polymer level to the maximum its solubility will allow (0.35%-Comparative Composition C) caused only a modest viscosity increase and the cloud point also rose further.

In Comparative Compositions D, E and F a somewhat lower molecular weight polymer, Natrosol 250 MHR, was tried. As may be seen, levels of 0.15 and 0.3% gave insufficient viscosity increases, while a level of 0.45% (the solubility limit) gave good low-shear viscosity and cloud point, but the high-shear viscosity was still below 200 cp.

Comparative Compositions G and H represent an attempt to use a much lower molecular weight polymer, Natrosol 250 GR.

The higher level of 1.0% was initially chosen to give a good viscosity increase, but the cloud point rose to the unsatisfactory figure of + 12 C (Composition G). Use of a slightly lower level of this polymer in conjunction with slightly higher levels of the active detergents (Composition H) gave only a small improvement in cloud point, and the composition was also hazy at room temperature.

In Composition 1 according to the invention, the two polymers Natrosol 250 GR and 250 HHR were used in a ratio of 5:1 and at a total level of 1.0%, in conjunction with the same levels of active detergents as used in comparative Examples A to G. The cloud point and viscosities at both shear rates were good and the composition was clear at room temperature.

EXAMPLE 2 Compositions having a higher active ingredient level (64%) were prepared from the following ingredients: J 2 Dialkyl sulphosuccinate 36.5 36.5 Alkyl ether sulphate 18.5 18.5 Coconut or lauric diethanolamide 9 9 Ethanol (total) 14.5 14.5 Perfume 0.6 0.6 Natrosol 250 HHR - 0.087 Natrosol 250 GR - 0.348 Viscosity at 20 s 1 (cp) 28 285 Viscosity at 106 s 1 (cp) 28 201 Cloud point (OC) 0 +3 Clarity at room temperature clear clear It will be seen that the polymer mixture, used in 4:1 ratio, increased the viscosity of the base composition J to acceptable levels at both low and high shear, without detriment to the cloud point or the room temperature clarity.

Claims (10)

1. A liquid detergent composition containing at least 2% by weight of an active detergent system comprising or consisting of at least one water-soluble salt of a C3-Ct2 dialkyl ester of sulphosuccinic acid, and further comprising from 0.05 to 2.0% of a polymer mixture comprising.

(i) a first hydrophilically substituted polysaccharide of which the Brookfield viscosity of a 2% aqueous solution at 25"C is less than 500 cp, and (ii) a second hydrophilically substituted polysaccharide of which the Brookfield viscosity of a 2% aqueous solution at 25"C is at least 1000 cp, the weight ratio of (i) to (ii) being within the range of from 2:1 to 6:1.

2. A composition as claimed in claim 1, wherein the polymer (i) has a Brookfield viscosity (2% solution, 25"C) within the range of from 150 to 400 cp.

3. A composition as claimed in claim 1 or claim 2, wherein the polymer (ii) has a Brookfield viscosity (1% solution, 25"C) within the range of from 1500 to 5000 cp.

4.. A composition as claimed in any one of claims 1 to 3, wherein the weight ratio of polymer (i) to polymer (ii) is within the range of from 3:1 to 5:1.

5. A composition as claimed in any one of claims 1 to 4, containing from 0.1 to 1.0% by weight of polymers (i) and (ii).

6. A composition as claimed in any one of claims 1 to 5, wherein the polymers (i) and (ii) are selected from hydroxy (C2-C4) alkyl celluloses and hydroxy (C2-C4) alkyl guars.

7. A composition as claimed in claim 6, wherein polymer (i) is hydroxyethyl cellulose.

8. A composition as claimed in claim 6 or claim 7, wherein polymer (ii) is a hydroxyethyl cellulose or a hydroxypropyl guar.

9. A composition as claimed in any one of claims 1 to 8, containing from 50 to 80% by weight of active detergent.

10. A detergent composition as claimed in claim 1, substantially as described in Example 1 or Example 2 herein.