NO179796B - Concentrated liquid detergent mixture containing alkylbenzene sulfonate and magnesium - Google Patents

Abstract

A concentrated light duty liquid detergent composition is described. The composition, which offers superior grease cutting and foam mileage, contains a surfactant mixture of magnesium alkylbenzene sulfonate, alkyl ethoxy sulfate and optionally, alkyl sulfate. The composition also contains a magnesium ion source in an amount such that the molar ratio of total magnesium ion to alkylbenzene sulfonate ranges from about 0.65:1.0 to 1.0:1.0.

Description

The invention relates to aqueous, liquid detergent mixtures containing alkylbenzene sulfonate and added detergent-enhancing amounts of magnesium ions.

Liquid detergent compositions, such as those suitable for use in washing cups, are well known. The performance of such mixtures depends both on the amount of foam, i.e. the number of dishes washed, and the grease removal ability. The liquid detergent mixtures currently on the market are designed to remove oil/grease dirt from glasses, plates and other cutlery and kitchenware while maintaining an acceptable foam layer.

Liquid detergent mixtures containing magnesium salts and magnesium-containing surface-active agents exhibit increased performance, as described in US Patent Nos. 2,908,651 and 2,437,253. Certain combinations of active ingredients can also provide a range of improved detergent properties. An improved performance liquid detergent composition, described in US Patent No. 4,435,317, contains (a) a C10-C16 alkyl sulfate, (b) a C10<->C16 alkyl ethoxy sulfate, and (c) a straight chain C10-C15 alkylbenzenesulfonate in a ratio of the total weight of (a) + (b) to the weight of (c) of less than or equal to 33:1, and it contains magnesium in a molar amount corresponding to 0.20 x - 0.70 x, where x is the number of moles of alkyl sulfate. The amount of magnesium salts that can be added to the mixtures described in US Patent No. 4,435,317 is limited as the salts increase the temperature for the formation of inorganic salt crystals in the mixtures after cooling.

US Patent No. 4,923,635, corresponding applicant, relates to a liquid detergent mixture containing 10-50%

water-soluble alkyl benzene sulfonate and alkyl ethoxy ether sulfate with a weight ratio of sulfonate to sulfate of from 0.8:1 to 2:1, and 1-8% ethanolamide. The amount of magnesium ions amounts to 0.5-1.8% by weight. The weight ratio between magnesium and triethanolammonium ions lies in the range from 2:1 to 1:2.4. The cations in the alkylbenzenesulfonate are preferably made up of 80% magnesium ions, and in the most preferred mixtures, sodium ions make up the rest. There will thus be no molar excess of magnesium in relation to alkylbenzene sulphonate. The amount of magnesium ions makes up up to 1.8% by weight of the mixture, which corresponds to one molar species

ratio of magnesium to alkylbenzene sulphonate of less than 0.5:1. This ratio is lower than that used in the present invention.

Increased performance in relation to grease removal ability and foam volume is also achieved by increasing the concentration of surfactants in the liquid detergent mixture. However, there are several problems associated with the preparation of liquid detergent mixtures containing high proportions of active detergent materials, in order to satisfy the requirements for the clarity, viscosity and stability of the product.

In general, it is necessary to add a fairly high proportion of hydrotrope to those detergent mixtures which have a high concentration of active detergent materials. Hydrotropes are quite expensive and they are generally inactive materials and thus do not contribute to the washing effect, but they have the effect of making active ingredients water-soluble and the mixture homogeneous at the temperatures normally encountered during transport and storage. Hydrotropes generally lower the "bleaching point" of liquid detergent compositions, thereby maintaining a clear, liquid composition at temperatures where a detergent composition lacking a hydrotrope would become cloudy and have an unappealing appearance. US Patent No. 4,235,758 describes that the use of a magnesium alkylbenzene sulfonate derived from a straight-chain C10-C13 alkylbenzene with an average molecular weight of 220-250 significantly reduces the need for hydrotrope at any level of active detergent material.

The present invention provides mixtures which consist of certain specific detergent active ingredients in unique combinations and quantity ratios, and which have an unexpected ability to perform better compared to other liquid detergents both in terms of foam volume and grease removal.

Accordingly, it is an object of this invention to provide physically stable liquid detergent compositions having excellent grease removal ability and suds duration.

Another object of the invention is to provide detergent compositions containing magnesium, alkylbenzene sulfonate and added detergent enhancing levels of magnesium ions, which are particularly effective in removing greasy soil and which have a reduced need for hydrotropes to

maintain an appropriate blanking point.

With the present invention, a liquid dishwashing detergent mixture is thus provided which provides stable foaming properties and which is particularly effective for removing greasy dirt. The dishwashing detergent mixture is characterized in that it comprises: (A) from 20 to 70% of a surface-active system comprising: (a) from 15 to 35% by weight of the magnesium salt of a C10-C18-alkylbenzenesulfonic acid as anionic surfactant, (b ) from 1 to 5% by weight of a water-soluble magnesium salt in such an amount that the molar ratio between the total amount of magnesium ions and alkylbenzene sulphonate is in the range from 0.65:1.0 to 1.0:1.0, (c) from 1 to 20% by weight of a water-soluble C10-C16 primary alkylethoxysulfate containing on average from 1 to 6 ethylene oxide groups per alkyl group in the alkyl ether sulfate, and (d) from 0 to 20% by weight of a primary, secondary or tertiary amine or alkali metal salt of C10-C18 alkyl sulfate, and (B) from 0.5 to 8% by weight of a foaming agent selected from C10-C18 ethoxylated and non-ethoxylated mono- or di-Ci-Cg alkanolamides and C12-C14 alkylamides condensed with up to 15 mol of ethylene oxide per mol of amide, (C) from 0 to 10% by weight of an organic solvent which irritates little,

(D) from 0 to 10% by weight hydrotropic, and

(E) from 0 to 10% by weight of one or more optional

additives selected from chelating agents, coloring agents,

dyes, perfumes, bactericides, fungicides, preservatives, sunscreens, pH modifiers, pH buffers, opacifiers, antioxidants and proteins, and

(F) the rest water.

The detergent mixtures in accordance with the present invention comprise a mixture of two or three mainly anionic surface-active agents with defined compositions and quantity ratios, and have a specific molar ratio between magnesium ion and alkylbenzene sulphonate that lies in the range from 0.65:1.0 to 1.0 :1.0.

The first essential surfactant is a water-soluble salt of alkylbenzenesulfonic acid which may be straight chain or branched. The alkyl group preferably contains from 10 to 18 carbon atoms, preferably from 11 to 13, especially approx. 12 carbon atoms, preferably in a straight-chain configuration. The alkylbenzenesulfonate may be present as an alkali metal, amine, ammonium or alkaline earth metal salt, preferably the magnesium salt. The most preferred alkylbenzenesulfonate is thus the magnesium salt of straight-chain dodecylbenzenesulfonate.

The acid form of alkylbenzenesulphonic acid can be converted to the magnesium salt form either before mixing with the other cleaning ingredients or after this. The conversion can be carried out either by direct neutralization with magnesium oxide or -hydroxide, or by ion exchange between e.g. an alkali metal salt or the ammonium salt of alkylbenzene sulfonate and a water-soluble alkaline earth metal salt. A source of magnesium ions is preferably added to the detergent mixture so that the desired salt of alkylbenzene sulfonate is formed. Magnesium chlorides, magnesium sulphates, magnesium acetates or magnesium hydroxides are examples of magnesium sources. The preferred sources of magnesium are magnesium oxides or hydroxides and

- sulfates.

The alkylbenzene sulfonate component is present in an amount from 15 to 35% by weight of the mixture, preferably in the range from 15 to 22%, most preferably in the range from 19 to 21% by weight.

The point of attachment between the alkyl chain and the benzene ring, referred to as the phenyl isomer distribution, is not decisive, but according to the invention preferably less than 20% of the alkylbenzene comprises the 2-phenyl isomer.

Another essential surfactant component according to the present invention is a primary alkyl ethoxy sulfate derived from the condensation product of a C10-C16 alcohol with an average of 1 to 6 ethylene oxide groups, preferably 2-4, especially 3, ethylene oxide groups per moles of alcohol. The C10-C16 alcohols can e.g. extracted from natural fats or by Ziegler olefin formation or oxosynthesis. It is preferred to use alkyl ethoxy sulfates and alkyl sulfates with the same carbon chain length, preferably C12-C13. The amount of alkyl ethoxysulphate in the present mixture is, in order to achieve the desired foaming and washing properties, 1-30% by weight, preferably in the range from 10 to 20% by weight, based on the total mixture.

The surface-active system in the detergent according to the present invention may optionally also comprise an amount in the range from 0 to 20% of the total mixture, preferably 10-15% by weight, of an alkali metal or ammonium or amine salt of a straight-chain or branched C10 -C18-alkyl sulfate as an anionic surface-active agent. The cationic counterion to the alkyl sulphate can be taken from alkali metals, ammonia and amines, e.g. triethylammonium, triethanolamine (TEA), diethanolamine or monoethanolamine etc. Alkali metals can e.g. be sodium or potassium, preferably sodium.

The mixture according to the present invention contains from 0.027 to 0.064 mol total amount of magnesium ion. Generally, 0.023 to 0.053 moles of magnesium ion is provided through the incorporation of the magnesium alkylbenzene sulfonate. Additional magnesium can be added to the mixture in the form of a water-soluble compound, preferably a salt, such as e.g. magnesium sulfate or magnesium chloride. The preferred source of magnesium is magnesium sulfate heptahydrate added to the mixture in an amount from 1 or 2 to 5% by weight, preferably from 2.5 to 3.5% by weight, corresponding to 0.01 to 0.014 mol of added magnesium. The ratio between the total amount of magnesium ion and alkylbenzene sulfonate in the mixture is adjusted so that it corresponds to a molar ratio of from 0.65:1.0 to 1.0:1.0, preferably from 0.65:1.0 to 0.8:1 ,0.

The additional magnesium ions added in salt form provide improved grease removal ability and also lower the flash point of the mixture better than the more expensive hydrotropes. The additional amount of magnesium salt also gives the mixture better phase stability. The use of magnesium to enhance detergency is known, and when used with a molar ratio of total magnesium ion to alkylbenzene sulfonate in the range from 0.65:1.0 to 0.8:1.0, the excess of magnesium salt not only increases the foam volume, but also increases the fluidity, which enables a reduction in hydrotrope and alcohol quantities, and thus lowers the concentration of inactive components that do not enhance the washing effect of the mixture. This reduction in the amount of inactive ingredients leaves room for an even greater amount of detergent-active ingredients in the mixture.

The amount of detergent active ingredients in the mixtures according to the invention is in the range from 20 to 70% by weight, preferably from 30 to 55%. This increased amount of active ingredients results in increased foam volume and thereby provides an excellent liquid delicate detergent. The common problems of increased viscosity, reduced stability and product fading are avoided by using an increased amount of magnesium ions in a molar ratio of magnesium ion to alkylbenzene sulfonate ranging from 0.65:1.0 to 1.0:1.0, preferably from 0, 8:1.0, and no or only a low concentration of hydrotrope. The additional quantity of magnesium ions in the mixtures according to the invention also enhances the washing effect of the surfactant system.

In general, the consumer considers foaming ability as a measure of cleaning ability. A foaming agent, such as e.g.

a mono- or dialkanolamide, can therefore be added to the present mixture in an amount from 0.5 to 8% by weight, preferably 1-6%, and most preferably 1-5% by weight. The preferred foaming agent is a mixture of lauric acid and myristic acid monoethanolamides. Alternatively, the alkyl group in the amide may be derived from coconut or palm kernel oil. Suitable alkanolamides include either mono- or dialkanolamides with a carbon chain distribution from Cx to C5, preferably from Cx to C3, especially mono- or diethanolamine. The alkanolamide may be ethoxylated or may be a mixture of non-ethoxylated alkanolamide and ethoxylated alkanolamide to increase the solubility of the alkanolamide in the mixture.

Although it is not of decisive importance, the clarity and homogeneity of the mixtures according to the invention can be improved by incorporating e.g. organic solvents or hydrotropes, and these and other non-essential additives may be incorporated into the compositions in amounts which do not adversely affect the desired properties. Organic solvents may be incorporated for their dilution effect, ability to lower the clearing point and for solubilization. Such organic solvents, such as e.g. isopropanol, n-propanol, ethanol, propylene glycol or mixtures thereof may be included. When solvent is used, the amount is usually less than or equal to 10% by weight, preferably less than 8%, preferably in the range of 5-8% by weight. Ethanol is the preferred solvent. It is also common to include a hydrotropic substance in the mixture, such as e.g. urea, sodium xylene sulfonate, potassium xylene sulfonate, sodium cumene sulfonate, and ammonium xylene sulfonate, and the like, to aid in solubilizing various constituents of the mixture, and to maintain a low clearing point. Mixtures of two or more hydrotropes can also be used. When the hydrotrope is used, it is generally present in amounts below 8%, preferably below 6%, such as 1-6%, especially 2-5% by weight.

Various other optional ingredients may also be included in the mixture for reasons of desirable aesthetic or functional properties. Such components include e.g. opacifying agents to give the composition a pearly appearance, such as behenic acid or ethylene glycol distearate; perfumes; heavy metal chelating agents, such as EDTA; bactericides, such as trichlorocarbanilide, tetrachlorosalicylanilide, hexachlorophene or chlorobromosalicylanilide; antioxidants; such thickeners as guar gum, polyacrylates, polyacrylamide or carrageenan; dyes, water-dispersible pigments; preservatives, such as formaldehyde or hydrogen peroxide; pH modifiers etc. When used, these optional excipients may be present in total amounts up to 10% by weight, preferably up to 3% by weight, based on the total composition. The pH in the mixtures can be within the range 6-8, preferably from 6.5 to 7.5, and can, if necessary, be regulated by adding suitable acids or bases, such as HC1, NaOH and the like. Excellent grease removal is achieved when an effective amount of the present compositions is dissolved in an aqueous detergent solution. Typical usage concentrations are usually at least 0.05% by weight in water. This can of course be regulated, depending on the amount and type of dirt, and the user's wishes.

At present, there is great commercial interest in the more concentrated, liquid detergent mixtures. The advantages of highly concentrated liquids are obvious, ie reduced transport and packaging costs, and smaller quantities of product needed by the consumer. The main disadvantage when developing mixtures with large amounts of active ingredient is the difficulty in adapting the composition to the increased "solids" concentrations. The word "solid" is used here to describe all components of the mixture other than solvents, such as water or alcohol.

The mixtures according to the present invention contain large amounts of anionic surface-active agents, which are generally less water-soluble than non-ionic surface-active agents. The reduced solubility of the anionic surfactants coupled with the increased concentration of active ingredients often results in thick pastes with very high viscosities, thereby necessitating the use of extra powerful mixing equipment or high shear mixing equipment. Consequently, in a preferred embodiment of the present invention, a non-conventional process is used for the preparation of the mixtures according to the present invention.

According to this method, a detergent base base comprising magnesium alkylbenzene sulphonate and amide foam enhancer is prepared, preferably by a method where alkanolamide in the specified quantity is added to an aqueous slurry containing magnesium oxide or hydroxide, hydrotropes and any inorganic salts or organic solvents in the liquid detergent mixtures according to the invention, in the indicated amounts, and the alkylbenzenesulfonic acid is added after the alkanolamide has been dissolved in the slurry. This method is described in more detail in Norwegian patent application no. 914545. This method has the advantage that conventional liquid mixing equipment is used while simultaneously obtaining a mixture with increased fluidity during neutralization and after cooling.

Example 1

The following mixtures are prepared with conventional low shear mixing equipment by mixing the following materials in the indicated proportions.

The mixture according to experiment no. 2 is a physically stable liquid after accelerated aging at an elevated temperature. The mixture according to experiment No. 1, although it has a higher content of hydrotrope, was found to exhibit phase separation after aging. Each of the mixtures according to experiments 1 and 2 is evaluated using the following performance criteria:

(A) Fat gain test

This test is used to measure fat removal with

the mixture with a concentration of 1% liquid detergent at 50 ppm water hardness and 27 °C, with 600 dipping cycles at 60 rpm. For this test, 0.5 g of lard is added evenly at room temperature to a ground microscope slide using a serrated knife blade. The results are calculated as milligrams of lard removed.

A modified version of the degreasing test is used to measure degreasing with a 0.05% solution of liquid detergent at 50 ppm water hardness and 42 °C, with 600 dipping cycles at 60 rpm. For this test, 0.1 ± 0.02 g lard is added to plastic test tubes by dipping the pre-weighed tubes into melted lard and spotting any excess fat before it solidifies. The tubes are then weighed again and used the same day they are prepared.

The detergent mixtures to be tested are prepared, heated to the appropriate temperature and poured into 250 ml beakers. The desired temperature in the solution is maintained by means of a circulating water bath. The test mixture is stirred with a stirring rod until a layer of foam covers the top of each. The beakers and the soiled tubes are placed in the dipping apparatus which is then run at 600 cycles and 60 rpm. After completion of the test cycle, the tubes are removed, rinsed in deionized water at 25°C, air dried overnight and weighed. The dirt removal capacity (percent cleaned) is then calculated using the following formula:

where A = weight of pipe, B = weight of pipe plus dirt,

C = the weight of the tube after washing.

A comparison of the average amount of grease removed by the mixture according to Test No. 2 with a best-selling fine dishwashing detergent mixture (Control 2), determined by the grease removal test with 0.05% detergent concentration, 50 ppm water hardness, 42 °C, and 600 dip cycles at 60 rpm are shown in Table 1.

(B) Manual dish washing test

6 liters of a diluted (0.1% or 0.075%) test solution prepared using 50 ppm water at 49°C is fed to a washing tub from a separatory funnel suspended above the tub to produce the foam layer. Plates soiled with 5.4 g of lard are washed up to the foam end point. This test measures the total number of plates that can be washed with the detergent mixture until the foam completely disappears.

(C) Dynamic foam stability test

This test is used to determine the dynamic

foam stability of a liquid detergent mixture at 50 ppm water hardness and 45 °C.

A diluted (0.05 or 0.04%) test solution is titrated with a constant supply of mixed dirt to the foam end point with constant stirring. The test measures the amount of mixed dirt required to use up the surfactants in the mixture.

(D) Cylinder foam test

This test is used to determine the foaming ability of

a liquid detergent mixture at 50 ppm water hardness and 45 °C.

100 ml of a 0.1% LOL test solution is placed in a 500 ml measuring cylinder. The cylinder is turned upside down 20 times, and the amount of foam is measured. Dirt (0.01 g) is added to the solution, and the cylinder is again turned upside down 20 times. The reduction in foam level is then noted.

The test results with the mixtures according to Trials No. 1 and 2 and the results with two different best-selling commercial delicate detergent mixtures are shown in Table 2.

The results of this test indicate that the mixture according to Test No. 2 removes twice as much grease at 42 °C as a commercially leading detergent intended for washing dishes by hand, containing similar detergent active ingredients, but having a molar ratio of magnesium ion to alkylbenzene sulfonate of 0, 31:1.0.

Control 1: Leading commercial hand dishwashing mixture containing 50% active ingredients including 17% straight chain alkylbenzene sulfonate, 23% alkyl ethoxysulfate, 10% fatty acid monoethanolamide and a total magnesium content of 0.70%. This mixture has a magnesium to alkylbenzene sulfonate molar ratio of 0.58:1.0.

Control 2: A second leading commercial hand dishwashing mixture containing 56% active ingredients including 24% straight chain alkylbenzene sulfonate, 22% alkyl ethoxysulfate-3 EO, 10% ethoxylated fatty acid monoethanolamide and also containing 0.5 magnesium, corresponding to a molar ratio of magnesium to alkylbenzene sulfonate of 0, 31:1.0.

Example 2

A stable, pourable, liquid detergent composition is prepared by mixing the following ingredients using a conventional low shear liquid mixer. The proportion of each component is as follows:

Claims (3)

1. Liquid dishwashing detergent mixture that provides stable foaming properties and is particularly effective for removing greasy dirt, characterized in that it comprises: (A) from 20 to 70% of a surfactant system comprising: (a) from 15 to 35% by weight of the magnesium salt of a C10-C18 alkylbenzenesulfonic acid as an anionic surfactant, (b) from 1 to 5% by weight of a water-soluble magnesium salt in such an amount that the molar ratio between the total amount of magnesium ions and alkylbenzene sulphonate is in the range from 0.65:1.0 to 1.0:1.0, (c) from 1 to 20% by weight of a water-soluble C10-C16 primary alkylethoxysulfate which contains on average from 1 to 6 ethylene oxide groups per alkyl group in the alkyl ether sulfate, and (d) from 0 to 20% by weight of a primary, secondary or tertiary amine or alkali metal salt of C10-C18 alkyl sulfate, and (B) from 0.5 to 8% by weight of a foaming agent selected from C10-C18 ethoxylated and non-ethoxylated mono- or di-Ci-Cg alkanolamides and C12-C14 alkylamides condensed with up to 15 mol of ethylene oxide per mol amide, (C) from 0 to 10% by weight of a low irritant organic solvent, (D) from 0 to 10% by weight hydrotrope, and (E) from 0 to 10% by weight of one or more optional additives selected among chelating agents, coloring agents, dyes, perfumes, bactericides, fungicides, preservatives, sunscreens, pH modifying agents, pH buffering agents, opacifying agents, antioxidants and proteins, and (F) the rest water. 2. Mixture according to claim 1, characterized in that it comprises: (A) from 30 to 55%, (B) from 1 to 6%, (C) from 5 to 8%, (D) from 0 to 6% (E) from 0 to 3%, and (F) the remainder water. 3. Mixture according to claim 1, characterized in that the surface-active system (A) comprises (a) from 19 to 21% by weight of the magnesium salt of a C10-C18 alkylbenzenesulfonic acid; (b) such an amount of a water-soluble magnesium salt that the molar ratio of magnesium ion to alkylbenzene sulfonate is 0.65:1.0 to 0.8:1.0; (c) from 10 to 13% by weight of a C10-C16 alkylethoxysulfate with three ethylene oxide groups per moles of alcohol; and (d) from 10 to 15% by weight of a <C>10-C16 alkyl sulfate.