DE69027055T2 - cleaning supplies - Google Patents

Description

The present invention relates to liquid detergent compositions suitable for particular, but not exclusive, use in fabric washing, in shampoos and, furthermore, in manual dishwashing in both hard and soft water.

The term "dishes" as used here and below includes any utensils used in the preparation or consumption of food which must be washed to remove food particles and other food residues, fats, proteins, starches, gums, dyes, oils and burnt organic residues.

Liquid light detergent compositions, such as those suitable for use in washing dishes, are well known. Many formulations currently in commercial use are based on an anionic sulfonate-type detergent, particularly an alkylbenzene sulfonate, in combination with an alkyl polyethoxy sulfate (alkyl ether sulfate). The sulfonate-type detergent generally predominates.

The use of conventional dishwashing liquids based on alkylbenzene sulfonate (ABS)/alkyl ether sulfate (AES) or alkyl sulfate (PAS)/alkyl ether sulfate (AES) has been shown to have a detrimental effect on the condition of the hands of those using them. Consequently, mildness is considered a desirable quality feature in dishwashing liquids, with many specially formulated products on the market claiming this.

One of the main causes of skin irritation and roughness caused by surfactants is considered to be protein denaturation by surfactants (G. Imokawa et al., JOACS 52, 484-489, December 1975). The degree of protein denaturation by surfactants depends on the type of surfactants and their concentration.

Currently, the dishwashing formulations on the market which interact less strongly with proteins and are therefore considered milder are those based on a combination of ether sulphates and amine oxides (see, for example, US-A-3 928 249 of Procter & Gamble). Betaines can also be used instead of amine oxides (see, for example, US-A-4 554 098). However, such formulations - especially those containing amine oxides - are expensive not only because the active ingredients are expensive, but also because they require a large amount of expensive hydrotropic compounds such as xylene sulphonate and/or ethanol to form liquids which are stable and have an acceptable viscosity.

EP-A-0 232 153 (Unilever) describes detergent compositions based on a mixture of anionic and non-ionic surfactants together with foam boosters, at least some of the anionic surfactants consisting of alkyl ether sulfates.

Example 9 of EP-A-0 036 625 relates to a surfactant system comprising 33% of non-ionic compounds containing 9 to 10 EO units in combination with PAS, a special AES mixture and a betaine.

The incorporation of large amounts of non-ionic surfactants to form a mild system is preferred because such surfactants are inert to proteins in the skin and because formulations containing non-ionic compounds require smaller amounts of expensive hydrotropes.

Non-ionic compounds have also been shown to have good soil removal potential, particularly for removing greasy soils commonly found on dishes. However, non-ionic compounds as a class are low-foaming substances that form an unstable foam.

GB-A-2 165 855 (Colgate) discloses mild, liquid light cleaning agents based on non-ionic compounds, the non-ionic component accounting for more than 50% by weight of the total cleaning agent content. However, for the reasons given above, such formulations based on high levels of non-ionic compounds have deficiencies in terms of foaming performance.

The above-mentioned US-A-4 554 098 (Colgate) describes a mild dishwashing formulation based on an alkyl ether sulfate with an average of 5 to 12 moles of ethylene oxide in the molecule. However, such ether sulfates are not available commercially without difficulties. Furthermore, it is believed that the dioxane content in the ether sulfate raw material increases with the increase of the EO content in the ether sulfate. Consequently, for ease of commercial use, the use of widely used and generally available ether sulfates with less than 5 EO units is preferred.

Consequently, there is a need for the development of more cost-effective mild dishwashing formulations based on relatively cheap detergent raw materials that require smaller amounts of expensive hydrotropic compounds.

The present invention is based on the realization that low cost mild liquid dishwashing formulations with adequate performance can be obtained by careful selection of the active ingredients and their preparation, in particular by limiting the main anionic detergent active present and further incorporating selected amounts of alkyl ether sulfate, foam boosters and non-ionic detergent active material.

A first aspect of the present invention is a stable detergent composition in liquid form or gel form, which contains 10 to 80% by weight of an active detergent mixture of primary alkyl sulfate (PAS), alkyl ether sulfate (AES), water-soluble non-ionic detergent active material and betaine and/or amine oxide and further water and is characterized in that:

a) the AES has an average ethoxylation value between 1 and 5 and the PAS/AES weight ratio is in the range of 2/1 to 1/3,

b) the molar ratio of PAS/said betaine and/or amine oxide is in a range of 3/1 to 1/3 and

c) the non-ionic detergent constitutes more than 35 but less than 50 % by weight of the active detergent mixture.

Compositions according to the invention can display performance in detergency tests that is as good as that of conventional compositions containing alkylbenzene sulfonate, although the compositions according to the invention are significantly milder.

What is particularly surprising is that the mildness of the formulations based predominantly on non-ionic compounds can be fully retained by replacing a significant portion of the non-ionic compounds with ether sulfates with less than 5 EO units, while at the same time significantly increasing the foam performance and thus improving cost-effectiveness and economic efficiency.

Although in principle the concentration of the active detergent mixture can be as high as desired in the range 10 to 80%, provided that a stable liquid or gel product can be obtained, the concentration of the active detergent mixture is preferably in the range 5 to 60% by weight, with aqueous liquid compositions having an active detergent mixture in the range 5 to 40% by weight being of particular interest.

Primary alkyl sulfate (PAS) useful in the component of the invention preferably has the formula ROSO₃X, wherein R is a primary C₈-C₁₈ alkyl group and X is a solubilizing cation. Dobanol 23A from Shell is suitable, where R is predominantly a C₁₂ and C₁₃ group. As discussed in more detail below, alkyl sulfate is a constituent of the alkyl ether sulfates.

The active detergent mixture may further comprise one or more other detergent actives used in liquid compositions, for example alkyl glyceryl ether sulfonates or alkyl sarcosinates.

The second essential component of the active detergent mixture is alkyl ether sulfate (sometimes referred to as alcohol ether sulfate or alkyl polyethoxy sulfate) with at least one ethylene oxide residue per molecule. This is normally provided by incorporating into the composition an alkyl ether sulfate which is a mixture of materials of the following general formula:

R - (OCH₂CH₂)n - OSO₃X

where:

R is a primary or secondary C₁₀-C₁₈ alkyl group,

X is a solubilizing cation and the average degree of ethoxylation is between 1 and 5, preferably 3 and 4. Particularly preferred values of n are 3 and 4. R3 is preferably a C10-C16 alkyl group. In any given alkyl ether sulfate, several differently ethoxylated materials and some non-ethoxylated materials are present, with the value of n representing the average. The non-ethoxylated material is of course alkyl sulfate and contributes to the PAS content of the composition.

The amount of alkyl sulfate in any alkyl ether sulfate depends on the average degree of ethoxylation. If is 3, the alkyl sulfate typically constitutes 15 to 20% of the mixture, this value being lower if is 4 or more. If the proportion of alkyl sulfate is low, it may prove appropriate to ignore it. Nevertheless, it contributes to the PAS content of the composition.

When the average degree of ethoxylation is 2, the alkyl sulfate typically constitutes 30% of the mixture provided as "alkyl ether sulfate". Such a mixture may constitute both the PAS and AES components.

We have found that it is not possible to obtain an alkyl ether sulfate with an average degree of ethoxylation below 1.5 Unless the alkyl sulfate content of the ether sulfate represents a large part or all of the PAS component, it is preferred that the alkyl ether sulfate be formed by a material having on average at least 2 or 2.5 ethylene oxide residues per molecule.

Alkyl ether sulfate contains molecules with different numbers of ethylene oxide residues in a random distribution. In an alkyl ether sulfate in which the average degree of ethoxylation is 1.5 or more, the proportion of molecules with a single ethylene oxide residue is not substantially greater than the proportion with 2 ethylene oxide residues nor the proportion with the most frequently occurring number of ethylene oxide residues (if this is more than 2). Consequently, this feature is an observable property of AES. When the average degree of ethoxylation is 2 or more, as is preferred, the proportion of molecules with a single ethylene oxide residue is less than the proportion with 2 ethylene oxide residues and the proportion with the most frequently occurring number.

Preferred alkyl ether sulfates are mixtures of compounds of the above formula:

R-(OCH₂CH₂)n-OSO₃X

where is any positive integer, provided that the mean EO value is less than 5.

Examples of alkyl ether sulfates preferably used in the present invention are Dobanol (trademark) 23-3 from Shell, in which the degree of ethoxylation (n) is 3, and the equivalent material in which the degree of ethoxylation is 4. These materials are based on primary C₁₂-C₁₃ (50% each) alcohols (about 75% straight chain, 25% 2-methyl branched). Another preferred material is an alkyl ether sulfate based on Lial (trademark) 123 from Chimica Augusta, which is a branched chain primary alcohol with a degree of ethoxylation of 3 to 4 and with an alkyl chain length distribution similar to Dobanol 23. Also preferred is Empicol MD (trademark) from Albright & Wilson with a degree of ethoxylation of 4 based on mid-run coconut alkyl groups.

A suitable example of a secondary alcohol ether sulfate is a material derived from an alcohol such as Tergitol 15/S/3 (trademark) from Union Carbide (this material itself is not currently available). The conventional manufacturing process of the secondary alkyl ether sulfate is such that only a very small amount of alkyl sulfate is present in the product.

AES generally represents at least 12%, preferably at least 20 or 30%, of the active detergent mixture. Preferably it represents no more than 40% of the active detergent mixture.

The solubilizing cations of the anionic detergent actives of PAS and AES, designated X in the formulas above, can be any cations that impart the desired solubility to the anionic material. Monovalent cations such as alkali metal ions, ammonium and substituted ammonium are typical. Divalent ions that impart suitable solubility can be used, in particular magnesium ions used to improve soft water performance and can be incorporated as the magnesium salt of the anionic actives or as inorganic magnesium salts or incorporated in a hydrotropic system.

Betaine and amine oxide can be used as such or in a mixture. It is preferred to use significant amounts of betaine or amine oxide, especially amine oxides, for reasons of economy and hence cost-effectiveness. Preferably, the amount of amine oxide is not more than 10% by weight of the active detergent mixture. Preferably, the amount of betaine is not more than 30% by weight of this mixture. The total amount of amine oxide and betaine is conveniently not more than 30%, preferably not more than 15% or 10% by weight of the active detergent mixture. Preferably, betaines are used alone.

Suitable betaines are, for example, simple betaines of the formula:

and amidobetaines of the formula:

In both formulas, R is a straight chain or branched C₈-C₁₈ alkyl group. It can be a lauryl group or a mid-range coconut alkyl group. R₆ and R₇ each represent C₁-C₃ alkyl or C₁-C₃ hydroxyalkyl. Examples of sulfobetaines have the above formulas, where -CH₂CO₂⊃min; is replaced by

A suitable simple betaine is Empigen BB (TM) from Albright & Wilson. It has the formula given above, where R is C12-C14 alkyl derived from coconut and R6 and R7 are each methyl. Also preferred is Tego L7 (TM) from Goldsmidt which has the entire coconut alkyl group.

Suitable amine oxides have the following formula:

R₆ R₆ NTO

wherein R is a straight chain or branched C8-C18 alkyl group and R6 and R7 are each C1-C3 alkyl or C1-C3 hydroxyalkyl. A suitable amine oxide is Empigen OB (TM) from Albright & Wilson. In it, R is mid-run coconut alkyl and R6 and R7 are each methyl.

The water-soluble non-ionic detergent active materials are illustrated by examples of materials commonly used in detergent formulations. The betaines and amine oxides do not form part of the non-ionic component.

The non-ionic component is preferably a polyalkoxylated material, i.e. one or more ethoxylated non-ionic detergent active materials. It is suitable for such a material to have an HLB value in the range of 12.0 to 16.0.

The non-ionic component can consist of a polyethoxylated aliphatic alcohol with an alkyl chain length of 8 to 18 C atoms, preferably 8 to 16 C atoms, and an average degree of ethoxylation of 4 to 14. Suitable non-ionic cleaning agents include short-chain, high-foaming ethoxylated alcohols of the general formula:

R - (OCH2CH2)m - OH

wherein R is an alkyl group, preferably a straight-chain alkyl group having 8 to 18, better 8 to 16 carbon atoms, and in particular 9 to 12 carbon atoms, and the average degree of ethoxylation m is 5 to 14, preferably 6 to 12. A particularly preferred non-ionic cleaning agent is Dobanol 91-8 from Shell, wherein R is C9-C11 (predominantly straight-chain) and m is 8, or alternatively Lialet C11-10 EO.

Alternative suitable materials are those where R is a secondary alkyl having 8 to 18, preferably 11 to 15, carbon atoms and m is 5 to 14, preferably 6 to 12. An example of this is Tergitol (TM) 15/S/12 from Union Carbide (currently not available) or the Softanol (TM) A-series material (from Japan Catalytic).

Preferably, the polyethoxylated alcohol mixture is distilled to reduce the odor imparted to the composition. Another possibility for the non-ionic component is an ethoxylate alkanolamide of the general formula:

wherein R is straight chain or branched alkyl having 7 to 18 carbon atoms, R8 is ethyleneoxy or propyleneoxy, Y is hydrogen or -R8(CH2CH2O)qH, p is 1 or more, and q is 0, 1 or more, where R can be lauryl or coconut alkyl. Examples of ethoxylated alkanolamides are Amidox L5 and Amidox C5 from Stepan Chemical Company.

Other options for the non-ionic component are ethoxylated alkylphenols and ethoxylated fatty acids, i.e. polyethylene glycol esters of fatty acids.

The non-ionic component constitutes more than 35% by weight of the active detergent mixture, but less than 50% by weight.

Optionally, one or more mono- or dialkanolamides, preferably C8-C18, in particular C10-C18, carboxylic acid mono- or di(C2-C3)alkanolamides, may be present in the active detergent mixture of the composition according to the invention. These have the general formula R4 -CO - NHR5 or R4 - CO - N(R5)2, in which R4 is an aliphatic C7-C17 group, preferably straight-chain and preferably saturated, and R5 is a hydroxyethyl or hydroxypropyl group. R5 is preferably a 2-hydroxyethyl group.

Materials of this type are generally made from fatty acids of natural origin and contain a range of molecules with R4 groups of different chain lengths. For example, coconut ethanolamides consist predominantly of C12 and C14 material with varying amounts of C8, C10, C16 and C18 material. Preference is given to ethanolamides made from so-called middle run coconut fatty acids, in particular lauric acid.

The mono- and diethanolamides can make up 5 to 20% of the cleaning agent mixture.

It is generally necessary that the liquid detergent compositions according to the invention contain, in addition to the active detergent mixture and water, one or more hydrotropic compounds.

Hydrotropes are materials present in a formulation that control solubility, viscosity, clarity and stability but do not themselves actively contribute to the performance of the product. Examples of hydrotropes are lower aliphatic alcohols, particularly ethanol, urea, lower alkylbenzene sulfonates such as sodium, toluene and xylene sulfonates, and combinations of these compounds. Alcohols, urea and xylene sulfonate are preferred. Hydrotropes are expensive and take up space in a formulation without contributing to the performance of the formulation, so it is therefore desirable to use as small amounts of these compounds as possible.

For example, the use of the above-mentioned amine oxides requires a large amount of alcohol as a hydrotrope. For this reason and because of the high cost, it is preferable to avoid the use of a significant amount of any tertiary amine oxide in the present invention.

In preferred forms of the invention, the weight of the hydrotropic compound in the composition is not more than 12% by weight of the active detergent mixture.

The compositions of the invention may further contain the usual minor ingredients such as fragrances, colors, preservatives and germicides.

The stable liquid detergent compositions of the invention can be used for all normal detergent purposes, especially where foaming is advantageous, for example fabric washing products, general purpose domestic and industrial cleaning compositions, carpet shampoos, car washing products, body washing products, shampoos, bubble bath products and furthermore manual dishwashing products.

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

EXAMPLES

The foaming performance and mildness of various aqueous formulations were compared. Formulations I and II falling within the scope of the present application were compared with a comparable composition (A) containing more than 50% by weight of non-ionic active compounds.

The foaming performance was determined using a modified Schlachter-Dierkes test based on the principle described in Fette und Seifen 1951, 53, 207. 100 ml of an aqueous solution of each material to be tested at a concentration of 0.04% active detergent in 24º H water (French hardness) at a temperature of 45ºC were rapidly agitated in a graduated cylinder using a perforated disk that was moved vertically back and forth. After initial foam generation, 0.2 g increments of soil (9.5 parts commercial cooking shortening, 0.25 parts oleic acid, 0.25 parts stearic acid, and 10 parts wheat starch in 120 parts water) were added at 15 s intervals (10 s gentle stirring and 5 s rest) until the foam collapsed. The result was recorded as the number of soil increments (NSI score): a difference in score of 6 or less is generally considered non-significant. Each score was typically an average of 3 or 4 trials.

Several in vitro and in vivo methods for evaluating the protein denaturing efficacy of surfactants and their mixtures have been reported in the literature (see Miyazowa et al., Int. J. Cos. Sci. 6, 33-46, 1984 and the references cited therein). One such The method involves studying the interaction of cleaning agents with the acid phosphatase enzyme either from the skin (Prottey et al., Int. J. Cos. Sci. 6, 263-273, 1984) or from wheat germ (Tanaka et al., Anal. Biochem. 66, 489-498, 1975).

The in vivo mildness of formulations can be determined using the flexure wash test. In this test, the undiluted products were rubbed on the forearms of volunteers and rinsed off. The procedure was repeated four times a day for 5 days, with the degree of erythema formed being determined by experienced assessors.

A comparison of the results of the wheat germ acid phosphatase (WGAP) test and the flex wash test showed that formulations providing less than 50% enzyme inhibition are essentially bland under the test conditions. Any differences in blandness between products providing less than 40% inhibition do not show any detectable differences in blandness in the flex wash test. This indicates that the enzyme test is very sensitive and that in the real life situation there exists a threshold of protein denaturation below which all actives and products are indistinguishably bland. The results of the WGAP test are given as percent inhibition (i.e. 100% minus the remaining percent activity). Water gave no inhibition at all, i.e. 100% activity remained. Lialet 123-3S¹ Lialet 123-4S¹ Dobanol 23-A² Lialet 123-S² Lialet C₁₁ 10EO³ Empigen BB⁴ Empigen LME⁴ Flask Test (0.04% AB) % WGAP Inhibition 1 - Alkyl Ether Sulfate 2 - Primary Alkyl Sulfate 3 - Non-ionic 4 - Betaine 5 - Ethanolamide

The examples show that formulations I and II have better foaming performance than A. Although the percent WGAP inhibition of A is lower than that of I and II, there is no discernible difference in effective mildness for the reasons stated above. Thus, the compositions of the invention provide a combination of mildness and performance.

Claims (7)

1. A stable detergent composition in liquid or gel form containing 10 to 80% by weight of an active detergent mixture of a primary alkyl sulfate (PAS), alkyl ether sulfate (AES), a water-soluble non-ionic detergent active material and betaine and/or amine oxide and further water, characterized in that: a) the AES has an average ethoxylation value between 1 and 5 and the PAS/AES weight ratio is in a range of 2/1 to 1/3 and b) the molar ratio of PAS/said betaine and/or amine oxide is in a range of 3/1 to 1/3 and c) the non-ionic detergent constitutes more than 35 but less than 50 % by weight of the active detergent mixture. 2. Composition according to claim 1, wherein the PAS/AES weight ratio is in a range of 2/1 to 1/2. 3. A composition according to any one of the preceding claims, wherein the total amount of amine oxide and betaine is not more than 20% by weight of the active detergent mixture. 4. A composition according to any preceding claim, which contains substantially no amine oxide. 5. Composition according to one of the preceding claims, wherein the alkyl ether sulfate consists of a mixture of materials of the general formula: R - (OCH₂CH₂)n - OSO₃X where R is a C₁₀-C₁₈ alkyl group, X is a solubilizing cation and indicates the average degree of ethoxylation when it is between 2 and 5. 6. A detergent composition according to any one of the preceding claims, wherein the alkyl ether sulfate (b) consists of a primary alkyl ether sulfate, wherein the alkyl groups R are such that materials having an alkyl chain length of 14 carbon atoms or more account for less than 20% and the average degree of ethoxylation is 3 to 5. 7. A composition according to any one of the preceding claims, wherein the nonionic component is a material with a chain length of less than 12 carbon atoms.