WO2004056950A1

WO2004056950A1 - Detergent composition

Info

Publication number: WO2004056950A1
Application number: PCT/EP2003/012796
Authority: WO
Inventors: Ricardo Luiz Iavarone; Luciano Augusto Trivelin
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 2002-12-19
Filing date: 2003-11-12
Publication date: 2004-07-08
Also published as: AU2003283405A1; CL2003002682A1; AR042499A1; GB0229502D0

Abstract

A shear-thinning detergent composition in paste or paste like form is provided, comprising an anionic surfactant in an amount of 5 to 40 wt.% of the composition and a hydratable builder salt in an amount of from more than 5 to 60 wt.% of the composition. The composition has a viscosity of from 30 to 200 Pa.s at a shear rate of 1s-1 at 25 °C and a viscosity of from 5 to 25 Pa.s at a shear rate of 10s-1 at 25 °C and the ratio of the viscosity at 1s-1 to the viscosity at 10s-1 is from 2:1 to 10:1.

Description

DETERGENT COMPOSITION

TECHNICAL FIELD

This invention relates to a detergent composition and in particular to a detergent composition in paste or paste-like form.

BACKGROUND AND PRIOR ART

Detergent compositions in paste form are known for use in hand washing, personal washing and laundry washing applications. Detergent products in the form of powders and bars are well known for use in the washing of fabrics and generally are employed far more widely than detergent pastes for this particular application. Pourable liquid detergent compositions are also known. However detergent pastes provide a suitable form of detergent product especially for washing applications in which the product is applied directly to the fabric to be washed. Furthermore detergent pastes may also be employed in which the detergent is dosed into a liquor to provide a solution wash as is the norm with detergent powders . Pastes therefore provide the consumer with a flexibility as regards the type of washing operation which may be employed.

It is desirable to ensure that the viscosity of the composition is such that the composition is substantially not pourable, so that significant wastage is avoided in a direct application washing process and also that the composition is not so viscous that dispersibility and dissolution in a solution washing process become unacceptable if this flexibility of use is to be retained. Control of the viscosity of the composition to provide an optimum combination of characteristics is desirable.

It is also important that the composition is stable, i.e. it does not separate over time.

WO 95/09224A (Henkel) discloses a fabric washing detergent composition in paste form containing a mixture of nonionic and anionic surfactant of the sulphate and sulphonate type. The problem addressed in this disclosure is to minimise changes in viscosity due to an increasing or variable salt content from the surfactant raw materials. WO 95/09224 also discloses that a relatively modest level of salt, 0.5% in the case of a paste composition containing long chain alkyl sulphate as the only anionic surfactant, may lead to an unacceptable decrease in the viscosity of the paste composition; thus the level of salt may affect viscosity of the paste composition. This document discloses that 0.05 to 5wt% of alkali metal and/or ammonium sulphate and/or chloride may be present in the composition together with the nonionic surfactant and alkyl benzene sulphonate and ether sulphate and/or alkyl sulphate surfactant. This approach can give problems if soluble or hydratable builder salts such as sodium tripolyphosphate are present .

GB 2 308 128A (Unilever) discloses a shear-thinning detergent paste with a viscosity of 100 to 700 Pa.s at a shear rate of Is and a viscosity of from 400 to 5000 Pa.s at a shear rate of 0.1 s

WO 01/68794A (Procter & Gamble) discloses a solid detergent composition comprising a surfactant and a thickener which may be made into a detergent paste having a viscosity of from 0.024 to 3 Pa.s at a shear rate of 20.2s

It is known to formulate dish washing compositions as thick liquids, for example as described in EP-A-0365271. However, such compositions contain relatively ' small quantities of surfactant (typically less than 5 wt%) .

We have surprisingly found that stable detergent paste and paste-like compositions may be obtained by including in the composition a hydratable builder salt at a level of more than 5 wt% of the composition without the need to necessarily employ a variety of surfactants in order to control the viscosity, and also that a specific type of shear-thinning viscosity is particularly suitable for direct application to fabrics.

DEFINITION OF THE INVENTION

The invention provides a shear-thinning detergent composition in paste form comprising

(a) an anionic surfactant in an amount of 5 to 40 wt% of the composition; and (b) a hydratable builder salt in an amount of from more than 5 to 60 wt% of the composition; and the composition has

(c) a viscosity of from 30 to 200 Pa.s at a shear rate of Is^" at 25°C; and

(d) a viscosity of from 5 to 25 Pa.s at a shear rate of 10s^" at 25°C; and

(e) the ratio of the viscosity at Is to the viscosity at 10s is from 2:1 to 10:1.

DETAILED DESCRIPTION OF INVENTION

The composition of the present invention is preferably a paste, gel, semi-solid or highly viscous liquid.

It is not normal in the detergent art to formulate viscous detergent compositions having a viscosity in the range covered by the present invention, because compositions in this range can be sensitive to variables such as temperature, composition etc. Surprisingly, the present inventors have discovered that a detergent composition having the viscosity range specified gives acceptable rates of dissolution in wash water while being particularly suitable for direct application to fabrics. The Viscosity Profile

Viscosity is measured at 25°C, as is standard in the art. Viscosity is preferably measured in a manner known in the art using a Haake VT 550 rotoviscometer using SV IIP cup and bob.

The composition of the present invention is shear thinning; that is, the viscosity decreases as the shear rate increases.

Preferably the detergent has a viscosity at a shear rate of Is^" at 25°C of from 30 to 140 Pa.s, preferably from 40 to 99 Pa.s. Preferably the detergent composition has a viscosity at a shear rate of 10s at 25°C of from 10 to 20

Pa.s. Preferably the the ratio of the viscosity at Is to the viscosity at 10s is from 3:1 to 7:1.

The viscosity of the composition may be tailored according to local market requirements. Less viscous compositions may be provided by including water in the composition at a relatively high level such as at least 45 wt% and, according to the viscosity required up to 75 wt% of the composition. The precise level may be selected according to the other components in the composition.

The viscosity according to the invention can be achieved by a number of techniques known to the skilled person. A filler or structurant may be included. For example, the balance of filler and surfactant may be adjusted. For example, the weight ratio of surfactant to filler may be in the region 2:1 to 1:2, preferably about 1:1. The quantity of water may be suitably controlled.

Viscosity may also be controlled by use of a thickening agent. A suitable thickening agent is a carbopol .

Detergent compositions according to the invention having a higher viscosity may be produced by incorporating a structurant or solid material for example a filler.

Suitable fillers include conventional inorganic fillers such as kaolin, silica, starch, bentonite, talc, clay, silicate and especially calcite. The amount of inorganic material included as a filler will vary according to the desired viscosity but generally will not exceed 40%, and or preferably not exceed 30 wt% of the composition.

The Hydratable Builder Salt

Suitably any hydratable salt may be employed although it is preferred if the hydratable builder salt is selected from builders such as polyphosphates, orthophosphates, tripolyphosphates, phosphates, tetraphosphates, pyrophosphates, carbonates and bicarbonates and the alkali metal and ammonium salts of any of the foregoing.

Silicates, preferably sodium silicates may be used, such as metasilicates, disilicates, alkaline silicates etc, or mixtures thereof. The hydratable builder salt may be added in solution if necessary.

Pyrophosphates are preferably present at a level less than 5 wt%, preferably less than 1 wt%, as they can lead to instability of the composition.

Preferably the hydratable salt is present at a level of at least 10 wt% and desirably at least 15 wt% of the composition. Suitably the level of the hydratable salt does not exceed 60% and preferably does not exceed 50 wt% of the composition and a level of not more than 40 wt% is especially preferred.

In a particularly preferred embodiment, the hydratable salt comprises sodium tripolyphosphate and optionally sodium carbonate. Sodium tripolyphosphate is preferably present in an amount of 5 to 25% and preferably less than 30 wt% of the composition and, if present, the carbonate is suitably at a level of 1 to 15% especially 4 to 12 wt% of the composition.

Additional builder components may be included, such as calcite, aluminosilicates such as zeolite, organic builders, including organic polymeric builders, and mixtures thereof.

The compositions of the present invention can dissolve quickly in wash water. Preferably at least 30 wt%, more preferably at least 40 wt% of the composition dissolves in 30 seconds in the wash water at 25 °C. The Anionic Surfactant

As regards the anionic surfactant, any conventional anionic surfactant may be employed including surfactant selected from linear or branched alkyl benzene sulphonate, alkyl sulphate, alkyl ether sulphate, alkane sulphonate, olefin sulphonate, fatty acid monoglyceride sulphate, alkyl glycerol ether sulphate, acyl sarcosinates, salts of Cβ to

C₂₀ fatty acids and rosin acids and mixtures thereof. Suitably the anionic surfactant is present as an alkaline metal, alkaline earth metal or an ammonium or substituted ammonium salt.

In another preferred embodiment, the anionic surfactant comprises linear alkyl benzene sulphonate. These surfactants suitably have a Cg to C₁₅ alkyl chain.

The anionic surfactant may be incorporated as a pre- neutralised material or the acid form of the surfactant may be incorporated with a suitable quantity of alkaline material in order to effect the neutralisation of the acid.

Preferably the level of anionic surfactant in the composition is from 7 to 35 wt%, more preferably from 10 to 30 wt%.

Other types of anionic surfactant may be present at a level of 1 to 35 wt%, more preferably 2 to 20 wt% of the composition. The level of surfactant in the composition is selected according to the performance criteria required and having regard to cost .

Detergent compositions of this type may be formulated with the quantity of anionic surfactant exceeding that of builder salt or with the quantity of builder salt exceeding that of anionic surfactant, in weight percent terms. The choice of composition will depend upon factors such as the hardness of the water to be encountered, relative costs of the components, the effect of the components on the viscosity of the mixture and wash habit. Surfactants which are relatively tolerant towards hardness in water, such as olefin sulphonates and lauryl ether sulphates may be used in quantities exceeding the level of builder.

The form of the surfactant may be controlled. Preferably, the surfactant is in the lamellar or a viscous micellar phase. The surfactant can be fixed in these phases by controlling its dilution or, by structuring with suitable structuring agents such as electrolyte, e.g. NaCl , Na₂Cθ₃.

The filler may be used to stabilise the dispersion against separation.

Other Detergent Ingredients

Other surfactants may be included in the composition as desired. Suitable other surfactants include other anionic surfactants, nonionic, amphoteric and cationic surfactants which may be included in order to provide improved cleaning performance or other desirable properties. If other surfactants are present, the detergent composition preferably contains nonionic surfactant, especially alcohol alkoxylates which desirably have a linear or branched alkyl chain having 9 to 15 carbon atoms and which have an average degree of ethoxylation of 1 to 15, preferably 1 to 10 for example 3 and 7. Nonionic surfactants may be employed in the composition in order to provide improved skin mildness characteristics .

However, nonionic surfactants are preferably present in low quantities, as they have a deleterious effect upon foaming. The level of foam produced is an important indicator to the user of effectiveness of the surfactant composition. Preferably, nonionic surfactant is present at a level of from 0.1 to 5 wt%, preferably from 0.5 to 3 wt%.

It is preferred not to use substantial quantities of fatty acid soap. However, as described below, fatty acid soap may be used as a structurant at a level of less than 3 wt% of the composition.

Preferably the detergent composition is formulated so that in use as a paste in a direct washing application, it has a pH of 8 to 11.5, preferably 9 to 11.

A filler may be added, such as clay, kaolin, silica, starch, bentonite, talc, silicates of other metals such as calcium, calcite or mixtures thereof .

A small quantity of soap may be included as a structurant. Soap may be defined as alkali metal salts of long chain moncarboxylic acids. Preferably, the alkali metal salt of C16-C26 carboxylic acids or a mixture thereof may be used. Preferably, C18-24 soaps are used, most preferably C20-C24.

The structuring properties of soap vary with temperature. The composition tends to become more liquid with increasing temperature. It has been found that long chain fatty acid soaps (C20-C24) retain their structuring properties up to temperatures in the region 40-50°C.

The soap structurant is preferably present in an amount of approximately 0.2-3 wt%, most preferably 0.5-2.0 wt%, preferably about 1 wt%. Excess quantities of sodium soap have been found to suppress formation of foam.

Other structurants may be used. It is preferred that a cross-linked carboxylic polymer structurant is substantially absent, as it is believed to be less effective. Similarly, it is preferred that clay, such as natural or synthetic hectorite clay structurant is substantially absent. Non- structurant clay may be included.

Manufacturing Methods

Compositions according to the invention may be prepared by incorporating the components of the composition into a batch mixer with agitation in order to provide a substantially homogeneous composition. For high viscosity pastes, a Winkworth Z-blade mixer may suitably be employed and for lower viscosity compositions, for example below about lOOPa.s, a conventional batch mixer equipped with paddles may be employed.

An alternative process involves the use of two mixing stages. This involves firstly making a slurry from some of the powder ingredients plus water and a second main mixer tank with the remaining ingredients.

A further alternative process is to use a three stage process. This is where liquid acidic surfactant precursors are added with a neutralising agent in a reaction tank in order to produce the neutralised surfactant, prior to using the two-stage process as described above.

Care must be taken with the control of the temperature and the speed of agitation.

Compositions according to the invention may comprise other ingredients conventionally found in detergent compositions, including fluorescers lather control agents or lather boosters as appropriate, dyes, perfumes and the like. Antiredeposition agents such as sodium carboxy methyl cellulose (SCMC) may be used at a level of 0.1 to 4% preferably 0.2 to 2 wt%. This list is not intended to be exhaustive. All amounts and proportions and by weight unless otherwise specified.

EXAMPLES

The invention is illustrated by the following non-limiting Examples . Example 1

The composition, indicated as weight percent, as detailed in Table 1 below was produced by dosing the components into a batch mixer. The process was conducted at about 40 °C and was carried out in a common Liquid Detergent (HDL) process plant :

The raw materials were sequentially added into a single stirrer tank.

Table 1

The composition produced according to Example 1 exhibited acceptable washing performance and desirable foaming and sensory properties when tested by manual application and washing of fabrics.

Claims

1. A shear-thinning detergent composition in paste form characterised in that it comprises:

(a) from 5 to 40 wt% of anionic surfactant;

(b) from 5 to 60 wt% of a hydratable builder salt; and the composition has

(c) a viscosity of from 30 to 200 Pa.s at a shear rate of Is^" at 25°C; and

(d) a viscosity of from 5 to 25 Pa.s at a shear rate of 10s^" at 25°C; and

(e) the ratio of the viscosity at Is^"1 to the viscosity at 10s^" is from 2:1 to 10:1.

A detergent composition as claimed in claim 1, characterised in that it has a viscosity of from 30 to

140 Pa.s at a shear rate of Is at 25°C.

3. A detergent composition as claimed in claim 2, characterised in that it has a viscosity of from 40 to

99 Pa.s at a shear rate of Is at 25°C.

4. A detergent composition as claimed in any preceding claim, characterised in that it has a viscosity of from

10 to 20 Pa.s at a shear rate of 10s^" at 25°C. A detergent composition as claimed in any preceding claim, characterised in that the ratio of the viscosity at Is to the viscosity at 10s is from 3:1 to 7:1.

6. A detergent composition according to any preceding claim, characterised in that the hydratable builder salt is selected from polyphosphates, orthophosphates, tripolyphosphates, phosphates, tetrasphosphates, pyrophosphates, carbonates, bi-carbonates, silicates, aluminosilicates, alkali metal and ammonium salts thereof and mixtures thereof .

7. A detergent composition according to any preceding claim, characterised in that the hydratable builder salt is present at a level of from 7 to 50 wt%, preferably from 10 to 40 wt%, more preferably from 15 to 30 wt% of the composition.

8. A detergent composition as claimed in any preceding claim, characterised in that it comprises from 7 to 35 wt% anionic surfactant.

9. A detergent composition according to any preceding claim, characterised in that the anionic surfactant is selected from linear or branched alkylbenzene sulphonate, alkyl sulphate, alkyl ether sulphate, alkane sulphonate, olefin sulphonate, fatty acid monoglyceride sulphate, alkyl glycerol ether sulphate, acyl sarcosinates, salts of C₆-C₂₀ fatty acids and rosin acids and mixtures thereof.