LU86731A1 - THIXOTROPIC GEL-LIKE AQUEOUS LIQUID CLEANING COMPOSITION AND METHOD USING THE SAME TO WASH DISHWASHER IN AN AUTOMATIC DISHWASHER - Google Patents

Description

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The present invention relates to a thixotropic aqueous suspension whose physical stability is improved. More particularly, the invention relates to the use of long chain fatty acids as a thixotropic agent for the formation of stable liquid suspensions similar to gels, suitable for use as liquid detergent compositions for automatic dishwashers.

The present invention relates in particular to 10-detergent compositions for automatic washing of dishes, endowed with thixotropic properties, better physical and chemical stability and increased apparent viscosity, and which can be easily dispersed in the medium for efficient cleaning of dishes, glasses, porcelain, etc.

Powdered detergents available commercially for automatic dishwashers have various disadvantages, for example a non-homogeneity of composition; the high cost of the operations necessary for their manufacture; a tendency to solidify during storage in high humidity, which leads to the formation of lumps which are difficult to disperse; a powdery or dusty state which is a particular source of irritation for users suffering from allergies; and a tendency to solidify in the dishwasher dispenser. However, liquid forms of such compositions generally cannot be used in automatic dishwashers due to high degrees of foaming, unacceptably low viscosities and too high alkalinity.

Research and development activity> i 2 have recently focused on the "gel" or "thixotropic" form of such compositions which are insufficiently viscous to remain "fixed" in the dispenser compartment of the dishwasher, and leave 5 in addition to residual stains on dishes, glasses, porcelain, etc. Ideally, the thixotropic cleaning compositions must be very viscous at rest, have a plastic nature according to Bingham and have relatively high flow limits. . However, when they are subjected to shear stresses, for example by being shaken in a container or expressed by an orifice, they must become fluid quickly and, when the shear stress ceases to be applied, quickly return to Bingham high viscosity / plasticity state. Stability is also of paramount importance, i.e. there should be no obvious indication of phase separation or pouring after prolonged rest.

It has therefore been found to be very problematic to have compositions for automatic dishwashers in gel form having the properties described above, in particular in the field of compositions intended for use in domestic dishwashers. For effective use, it is generally recommended that the detergent for automatic dishwashing, also referred to below as DLAV, contain: (1) sodium tripolyphosphate (NaTPP) used to soften or fix the mineral matter of the 'hard water and emulsify and / or pepti-ser dirt; (2) sodium silicate used to give the necessary alkalinity. Good detergent power and to protect varnishes and designs of fine porcelain; (3) sodium carbonate, t> 3 generally considered optional, to increase the alkalinity; (4) a chlorine releasing agent used to facilitate the removal of point dirt which leads to the formation of water spots; 5 and (5) a surfactant / foam suppressant to reduce foam, to improve machine efficiency and provide the necessary detergency. See, for example, SDA Detergents in Depth, "Formulations Aspects of Machine Dishwashing", Thomas Oberle 10 (1974). The cleaning products whose compositions approach those described above are mostly liquids or powders. It has proven difficult to combine these ingredients in an effective gel form for use in domestic machines. In general, such compositions do not include bleaching hypochlorite as it tends to react with other chemically active ingredients, especially the surfactant, thereby degrading the suspending or thixotropic agent and reducing its effectiveness. cited. Thus, the U.S. patent No. 4,115,308 describes thixotropic pastes for automatic dishwashers, containing a suspending agent, for example CMC (carboxymethyl cellulose), synthetic clays, etc .; mineral salts including silicates, phosphates and polyphosphates; a small amount of surfactant and a foam inhibitor. There is no mention of a bleaching agent. The E.ü.A. No. 4,147,650 is somewhat similar, optionally including a chlorine bleach (hypochlorite), but no organic surfactant or foam inhibitor. In addition, the product is described as a detergent suspension devoid of apparent thixotropic properties.

The U.S. Patent No. 3,985,668 describes (4 abrasive scouring cleaning agents having a gel consistency, containing (1) a suspending agent, preferably a clay of the smectite or atapulgite type; (2) an abrasive, for example silica sand or perlite; and (3) an inert filler comprising low density powdered polymers, perlite, etc. which exhibits buoyancy and thus exerts a stabilizing effect on the composition, in addition to serving agent giving volume, thus replacing water which otherwise would be available for the formation of an undesirable supernatant layer under the effect of pouring and phase destabilization. optional ingredients include a bleach hypochlorite, a bleach-stable surfactant and a buffer, for example silicates, carbonates and monophosphates. Detergency builders such as NaTPP can be included as other optional ingredients for exercising or complete the adjuvant function not exerted by the buffer, the proportion of such a detergency builder not exceeding 5% of the total composition, according to this patent. Maintaining the desired pH values (10 or higher) can be achieved by the buffer / detergency builder components. A high pH is said to minimize the decomposition of the chlorine bleach and an undesirable interaction between the surfactant and the bleach. As stated, NaTPP is limited to 5% if present. There is no mention of foam destroyers.

In patent applications GB-A-2,116,199 and -2,140,450 of the applicant, there are described DLAV compositions having properties advantageously characterizing a thixotropic gel-like structure and which each comprise the various necessary ingredients effective detergent action with an automatic dishwasher. The aqueous detergent composition, normally gel-like, for automatic dishwashers, having thixotropic properties, comprises the following ingredients, on a weight basis: (a) 5 to 35% alkali metal tripolyphosphate; (b) 2.5 to 20% sodium silicate; (c) 0 to 9 ° 4 of alkali metal carbonate; (D) 0.1 to 5% organic matter with detergent action dispersible in water, stable with respect to the chlorine bleach; (e) 0 to 5% of foam inhibitor stable against the chlorine bleach; (F) a chlorine compound as a chlorine bleach in an amount sufficient to provide about 0.2 to 4% of active chlorine; (g) a thixotropic thickener in an amount sufficient to give the composition a thi-xotropy index of about 2.5 to 10; and (h) what sodium hydroxide is needed to adjust the pH.

The DLAV compositions thus formulated exhibit little foam; they dissolve easily in the washing medium and are most effective at the pH most favorable for a better cleaning action, that is to say at pH 10.5-13.5. The compositions normally have a gel consistency, i.e. they are very viscous materials, similar to opaque jelly, having a plastic character according to

Bi-ngham and therefore high flow limits. Consequently, a defined shear force is necessary to initiate or increase the flow, as is the case in the dispenser compartment with the stirring of a live automatic dishwasher. Under these conditions, the composition fluidizes quickly and disperses easily. When the shear force is interrupted, the flowable composition quickly returns to a state of high viscosity and Bingham plasticity closely approaching its initial consistency.

The U.S. Patent No. 4,511,487 describes a low foaming detergent paste for dishwashers. The thixotropic washing agent of this patent has a viscosity of at least 30 Pa.s at 20 ° C, as determined using a rotary viscometer at a spindle speed of 5 revolutions per minute. The composition is based on a mixture of finely divided hydrated sodium metasilicate, an active chlorine compound and a thickener which is a laminated silicate of the hectorite type. A small amount of nonionic surfactants and alkali metal carbonates and / or hydroxides can be used.

The formation of organic clays by the interaction of clays (such as bentonite and hectorite) with organic compounds such as quaternary ammonium salts has also been described (WS Mardis, JAOCS, Vol. 61, N * 2, page 382 (1984)).

25 Although these liquid formulations of DLAV

described above are not subject or are subject to a lesser degree to one or more of the disadvantages described above, it has been found that in actual practice there is still a need to further improve physical stability in order to increase the shelf life of the product and thus improve consumer acceptability.

In the prior patent application in France N * 86 08287 filed on June 9, 1986, the physical stability of thixotropic liquid formulations based on clay is improved by adding small amounts, for example of about 0.02 to 1 % by weight, of a polyvalent metal salt of a long chain fatty acid, such as aluminum stearate.

Although the combination of a thickening clay and a stabilizing fatty acid salt has been found to provide satisfactory long-term stability, such as the absence of phase separation for periods of 12 weeks or more , the addition of clay to these formulations has several drawbacks.

For example, when thickening clays are used, the order of addition of the various ingredients and the control of the operating conditions during the preparation of the compositions are decisive for obtaining the desired thixotropic properties and the desired low foaming characteristics. . In addition, thickening clays are expensive materials and can take a large part in the final cost price to the consumer. In some cases, thickening clays can actually affect the overall cleaning performance.

It is therefore an object of the invention to provide stable thixotropic aqueous suspensions which avoid the use of thickening clays.

Another object of the invention is to provide liquid DLAV compositions endowed with thixotropic properties and having greater physiological stability than and better rheological properties.

Yet another object of the invention is to provide thixotropic liquid compositions of DLAV containing lower proportions of thixotropic thickener without this adversely affecting the generally high viscosities at low shear rates and the lowest viscosities at high rates of shear which are characteristic of the desired thixotropic properties.

More generally, an object of the present invention is to provide thixotropic, aqueous, stable, non-clay based compositions, in particular liquid detergent pastes or gels for automatic dishwashers, by incorporating into the aqueous suspension free of clay a minor amount of a fatty acid effectively inhibiting the sedimentation of suspended particles and preventing phase separation.

These objects of the invention, as well as others which will become apparent from the detailed description which follows, are achieved by incorporating into a aqueous liquid detergent composition a small but effective amount of a non-clay non-polymeric thixotropic agent which is a long chain fatty acid. More particularly, according to a preferred and particular form of the invention, there is provided a detergent composition normally analogous to an automatic dishwasher gel, in which about 0.03 to 0.5% by weight is incorporated, relative to by weight of the composition, a long chain fatty acid which is effective in inhibiting the deposition of suspended particles, for example alkali metal salts, detergency builders, etc., without the need for clay, polymer, etc., as thickeners.

According to this particular aspect, the present invention provides an aqueous detergent composition normally analogous to a gel for an automatic dishwasher, endowed with thixotropic properties, which comprises, on a weight basis: 9 (a) 5 to 35% of alkali metal tripolyphosphate ; (b) 2.5 to 40% sodium silicate; (c) 0 to 9% alkali metal carbonate; (d) 0.1 to 5% of an organic material with detergent action dispersible in water and stable towards the chlorine bleach; (e) 0 to 5% of a foam inhibitor stable against the chlorine bleach; (f) a chlorine compound as a chlorine bleach, in an amount providing about 0.2 to 4% of active chlorine; (g) 0.03 to 0.5% of a long chain fatty acid; (h) 0 to 8% sodium hydroxide; and (i) the remainder being water.

Also related to this particular aspect the invention provides a method for cleaning dishes in an automatic dishwasher with an aqueous washing bath containing an effective amount of the liquid detergent composition for an automatic dishwasher ( DLAV), as described above. According to this aspect of the invention, the DLAV composition can be easily poured into the dispenser compartment of the automatic dishwasher 25 and, in a few seconds, it thickens to reach its normal pasty or gel-like state so as to hold firmly in the dispenser compartment until shear forces are applied to it again, for example by the 30

Det water sent by the dishwasher.

The invention will now be described in more detail with reference to the appended drawing in which: the single figure is a graphical representation of the thixotropy index of two different formulations according to the present invention and a liquid detergent composition, thickened by a clay, for an automatic dishwasher, as described in patent application GB-A-2 140 450.

5 The DLAV products of the descriptions of the prior art appearing in GB-A-2 116 199 -2 140 450 and in the French application 86 08 287 mentioned above have better rheological properties, as evaluated by determining the viscosity 10 of a product as a function of the shear rate. The compositions have a comparatively high viscosity at a low shear rate and a comparatively low viscosity at a high shear rate, the results indicating that effective fluidization and gelation take place well below the limits of the shear rates encountered. in a regular dishwasher. In practice, this means better pouring characteristics and behavior in operation as well as less pouring in the dispenser compartment of the machine, compared to the liquid or gel DLAVs of the prior art. For shear rates corresponding to 3 to 30 rpm, the viscosities (Brookfield) are correspondingly between approximately 10,000 to 30,000 mPa.s and approximately 3000 to 7000 mPa.s, as measured at temperature. ambient using a Brookfield LVT viscometer after 3 minutes using _ 1 an N * 4 spindle. A shear rate of 7.4 s corresponds to a spindle speed of approximately 3 30 tr / min. By increasing the shear rate by about ten times, the viscosity is reduced by about 3 to 9 times. The compositions of the aforementioned patent applications therefore have. Liminal fluidizations at lower shear rates and 11 of a markedly greater magnitude in terms of increasing the shear rate as a function of the decrease in viscosity. This DLAV property of the aforementioned patent applications is summarized by a thixotropy index (IT) which is the ratio of the apparent viscosities at 3 rpm and 30 rpm. The prior compositions have an IT of 2 to 10. The DLAV compositions should exhibit a significant and rapid return to the consistency prior to the quiescent state when the shear force is no longer applied.

Although the determination of the IT thixotropy index as a ratio of the apparent viscosities at 3 and 30 rpm constitutes a satisfactory measure of the usefulness of the product, other research and experiments have shown that could obtain a more reliable evaluation of the thixotropy index and the usefulness of the product as a liquid DLAV by determining the thixotropy as a measure of the area of the hysteresis loop obtained by carrying graphically, under the conditions described below, the shear stress, S, as a function of the shear rate, Ή, when the shear rate is increased from 0 to a maximum value then brought back to 0. The thixotropy index is all the higher that the area of the hysteresis loop is larger. In terms of apparent viscosity, it has also been found that, as long as the viscosity at room temperature (22 * 1 * 0, measured in a Brookfield HATD viscometer, using an N * 4 spindle at 20 rpm, is less than about 20,000 mPa.s, the composition can be easily shaken so that a thixotropic composition can easily be "fluidized" or "liquefied" to allow product to be delivered by a conventional compressible tube or other dispenser appropriate.

The present invention is based on the surprising discovery that the same or better rheological properties and physical stability can be achieved, i.e. resistance to phase separation, deposition, etc., than those obtained with these prior aqueous liquid DLAV compositions, at a much lower cost price and without special processing requirements, by adding to the composition a small but effective amount of a long chain fatty acid in place of the clay serving as a thixotropic thickener and, optionally, also the metal salt of the fatty acid. At the same time, improvements in behavior in the formation of stains or films can be achieved (that is, there are less stains and less film formation).

As an example of the improvement of the rheological properties compared to a conventional thixo-trope liquid DLAV based on clay, reference is made to the appended drawing which is a plot of the shear stress, S, as a function of the shear rate. , '11) for a clay-based DLAV (3% by weight of clay) (curve 1) and for two similar DLAV compositions in which the clay is replaced by 0.06% by weight d stearic acid (curve 2) or with 0.08% by weight of stearic acid (curve 3). The shear stress, S, is measured in a static test using a Haake RV-3 apparatus fitted with a coaxial cup. The sample is placed in the outer cup and the inner cup is rotated by the apparatus at higher and lower shear rates up to a maximum of 113 s, then the rate of shear is lowered progressively ju-35 13 to zero. The response is automatically recorded directly under shear stress. The experiments were carried out using an MV II sensor system (constant values, A = 3.76 Pa, M = 0.9 -1 5 s). The area between the resulting curves for each sample is a measure of the thixotropy of larger areas indicating higher thixotropy. The flow limit of each sample can also be determined by the curves shown in the drawing; the flow limit corresponding to the maximum stress on the curve giving the shear stress as a function of the shear rate. At the same time, the physical stability is such that even after six weeks or more, in temperature ranges from near-freezing to 40 ° C. and above, the compositions containing the fatty acid as thickener do not undergo any visible separation of phases.

Preferred long chain fatty acids are higher aliphatic fatty raonocarboxylic acids having about 8 to about 22 carbon atoms, preferably about 10 to 20 carbon atoms, and more particularly about 12 to 18 carbon atoms, including carbon atom of the fatty acid carboxyl group. Polycarboxylic acids can also be used. The aliphatic radical can be saturated or unsaturated and it can be straight or branched. Straight chain saturated fatty acids are preferred. Mixtures of fatty acids, such as those from natural sources, such as tallow fatty acid, coconut fatty acid, soy fatty acid, etc., or synthetic sources, may be used. from industrial manufacturing processes.

35 14

Thus examples of fatty acids which can be used as thickeners in place of clay or polymers include, for example, decanoic acid, lauric acid, dodecanoic acid, ^ palmitic acid, myristic acid, stearic acid, oleic acid, eicosanoic acid, tallow fatty acid, coconut fatty acid, soy fatty acid and mixtures of these acids. In addition, the dimers or trimers of these acids can also be used. -'O Preference is given to stearic acid and mixed fatty acids, for example coconut fatty acid.

In the carbon chain length ranges of the monocarboxylic fatty acids indicated here, the viscosity of the product tends to decrease as the number of carbon atoms in the monocarboxylic fatty acid decreases. No systematic trend is observed for dimers or trimers or polycarboxylic acids.

The amount of thickening fatty acid necessary to obtain the desired degrees of thixotropy and physical stability depends on factors such as the nature of the fatty acid, the detergent-acting compound, mineral salts, in particular TPP, other ingredients of DLAV, as well as conditions 2 ^ envisaged for storage and transport.

In general, however, proportions of the fatty acid thixotropic agent are in the range of about 0.03 to 0.5%, preferably about 0.03 to 0.2%, and more preferably from about 0.03 to 0.08%, ensure long-term stability and the absence of phase separation during rest or transport both at low and high temperatures, which are suitable for a product be commercially acceptable.

15

In general, the effectiveness of a DLAV is directly linked to (a) the contents of active chlorine; (b) alkalinity; (c) solubility in the washing medium; and (d) inhibiting foam. It is preferable in this case that the pH of the DLAV composition is at least about 9.5, and more preferably about 10.5 to 13.5, and in particular at least about 11.5 . At relatively low pH values, DLAV is too viscous, i.e. it is analogous to a solid, and thus it does not readily fluidize under the shear forces generated in the dispenser compartment in normal machine operating conditions. In principle, the composition loses much, if not all, of its thixotropic character. The addition of NaCH is thus often necessary to bring the pH to the above ranges, and to increase the flowability properties. The presence of carbonate is also often necessary in this case, since it acts as a buffer, helping to maintain the desired pH. However, an excess of carbonate should be avoided, as it can cause the formation of needle-like carbonate crystals, which alter the stability, thixotropy and / or detergency of DLAV, as well as the ability of the product to be distributed to starting, for example, from bottles with compressible tube. Caustic soda (NaOH) has the other function of neutralizing the ester of phosphoric or phosphonic acid which may be present as a foam inhibitor. Representative proportions are about 0.5 to 3% by weight of NaOH and about 2 to 9% by weight of carbonate in the DLAV composition, although it should be noted that sufficient alkalinity can be obtained with NaTPP and sodium silicate.

16

NaTPP can be used in the DLAV composition in an amount of about 8 to 35% by weight, preferably about 20 to 30% by weight, and it should preferably be free of heavy metal which tends to decompose or inactivate the preferred sodium hypochlorite and other chlorine bleaching compounds. The NaTPP can be anhydrous or hydrated, and it can be the stable hexahydrate having a degree of hydration of 6, corresponding to about 18% by weight of water or more. In reality, taking into account the stability of the hexahydrate, the presence of a little water of hydration is very effective, and serves, it seems, to form seeds of the stable hexahydrate which accelerates the hydration and solubilizing the remaining 15 particles of NaTPP. If only hexahydrate is used, the detergent product may be too liquid and may have little or no thixotropic character. Conversely, if only anhydrous NaTPP is used, the product may in some cases be too thick and therefore unsuitable. Particularly advantageous DLAV compositions are obtained by using, for example, a weight ratio of 0.5: 1 to 2: 1 from anhydrous NaTPP to NaTPP hexahydrate, values of about 1: 1 being particularly preferred.

25 The inhibition of foam is an important criterion for increasing the efficiency of the dishwasher and minimizing the destabilizing effects which could appear due to the presence of an excess of foam in the machine during its use. Foaming can be reduced sufficiently by an appropriate choice of the type and / or quantity of detergent-acting material ... which is the main foam generating component. The degree of foaming also depends to a certain extent on the hardness 17 of the washing water contained in the machine, so that an appropriate adjustment of the proportions of NaTPP having a water softening effect can promote the obtaining the desired degree of foam inhibition. However, it is generally preferable to include a foam suppressor or inhibitor which is stable against the chlorine bleach. Particularly effective compounds are the alkyl esters of phosphonic acids of formula: 10 0

HO P — R

GOLD

15 available for example from the company BASF-Wyandotte (PCUK-PAE) and in particular the alkyl acid phosphates of formula: 20 s

HO - P-OR

GOLD

25 available, for example, to Hooker (SAP) and

Knapsack (LPKn-158), in which one or both R groups of each type of ester may independently represent a C 12 -C 20 alkyl group, mixtures of the two types, or all 3Q other stable types, may be used with respect to the chlorinated bleach, or to mixtures of mono- and di-esters of the same type. Particular preference is given to a mixture of acid phosphates of mono- and dialkyl-c18 'such as the monostearyl / distearearic 1,2 / 1 phosphates (Knapsack). When used, the foam inhibitor generally represents 0.01 to 5% by weight, preferably 0.1 to 5% by weight, in particular approximately 0.1 to 0.5% by weight of the composition, the weight ratio of the detergent-acting component (d) to the foam inhibitor (e) generally being between approximately 10: 1 and 1: 1, and preferably between approximately 4: 1 and 1: 1. Other foam inhibitors which can be used include, for example, known silicones.

Although any chlorine bleaching compound may be used in the compositions of the present invention, for example a dichloroisocya-nurate, dichlorodimethyl-hydantoin or chlorinated TSP, an alkali metal hypochlorite, for example potassium, is preferred , lithium, magnesium and in particular sodium. The composition should contain enough chlorine bleach to provide about 0.2-4.0% by weight of active chlorine, as determined for example by acidifying 100 parts of the composition with excess hydrochloric acid. A solution containing about 0.2 to 4.0% by weight of sodium hypochlorite contains or provides substantially the same percentage of active chlorine. A proportion of about 0.8 to 1.6% by weight of active chlorine is particularly preferred. For example, one can advantageously use a solution of sodium hypochlorite (NaOCl) of approximately 11 to approximately 13% of active chlorine in proportions of approximately 30 to 20%, preferably approximately 7 to 12 %.

Sodium silicate, which provides alkalinity and provides protection for hard surfaces, for example varnish and fine porcelain designs, is used in an amount between 19 about 2.5 and 40% by weight, preferably between about 10 and 35% by weight, in the composition. At the high contents indicated here, for example at contents greater than about 10% by weight, the silicate also increases the anti-staining action. The sodium silicate is generally added in the form of an aqueous solution, preferably having an Na 2 O: SiO 2 ratio of about 1: 2.2 to 1: 2.8, for example 1: 2.4. Most of the other components of the composition, in particular NaOH, sodium hypochlorite and the foam inhibitor, can also be added in the form of an aqueous dispersion or solution.

The detergent-useful material useful here must be stable in the presence of the chlorine bleach, especially bleach hypochlorite, and as such water-dispersible surfactants of the organic types are preferred. anionic, amide oxide, phosphine oxide, sulfoxide or betaine, the anionic materials mentioned first being particularly preferred. They are used in proportions ranging from about 0.1 to 5%, preferably from about 0.3 to 2.0%. Particularly preferred surfactants here are the mono and / or di (C 6 -C 14 alkyl) diphenyl 7 mono and / or alkali metal disulfates with straight or branched chains available commercially, for example under the designations DOWFAX (registered trademark). ) 3B-2 and DOWFAX 2A-1. In general, paraffin sulfonates tend to reduce, if not destroy, the thixotropy, and have been found to excessively increase viscosity causing large shear force problems. In addition, the surfactant must be compatible with the other ingredients of the composition. Other suitable surfactants include alkyl sulfates, alkyl sulfonates, primary alkylarylsulfonates and sec.-alkylsulfates. Examples include (C 1 -C 4 alkyl) sodium sulfates such as sodium dodecyl sulfate and (tallow alcohol) sodium sulfate; sodium (C1-C6-alkane) sodium sulphonates such as sodium hexadecyl-1-sulfonate and sodium (C1-C6 alkyl) benzenesulfonates such as sodium dodecylbenzene sulfonates. The corresponding potassium salts can also be used.

As other suitable surfactants or detergents, surfactants of the amine oxide type are generally of structure I ^ R NO, where each R 15 represents a lower alkyl group, for example Ί methyl, and R represents a long chain alkyl group of 8 with 22 carbon atoms, for example a lauryl, myristyle, palmityl or cetyl group. Instead of an amine oxide, the phosphoxne oxide R ~ R PO or the corresponding sulfoxide 1 Δ RR SO can be used as surfactant. Betaine type surfactants generally have the structure R2R ^ NR "COO-, where each R represents a lower alkylene group of 1 to 5 carbon atoms. Particular examples of these surfactants are lauryldimethylamine oxide, myristyldimethylamine, the phosphine oxides and the corresponding sulfoxides, and the corresponding betaines, including dodecyldimethylammonium acetate, tetrade-cyldiethylammonium pentanoate, hexadecyldimethylammonium hexanoate, etc. For reasons of biode gradability, the alkyl groups of these surfactants should be linear, and these compounds are preferred.

Surfactants of the above type, which are all well known in the art, are described, for example, in U.S. Patents. N * 3,985,668 and N * 4,271,030.

The amount of water contained in these compositions should naturally be neither so high as to produce an excessively low viscosity and fluidity, nor so low as to produce too high a viscosity and too low flowability, the both thixotropic properties being reduced or destroyed. This amount is easily determined by routine experimentation in any particular case, and is generally between about 25 and 75% by weight, preferably between about 55 and 65% by weight. The water should also and preferably be deionized or softened.

Other conventional ingredients can be incorporated into these compositions in small quantities, generally less than approximately 3% by weight: this is the case, for example, of perfume, hydrotropic agents such as benzene, toluene, xylene and sodium cumene sulfonates, preservatives, dyes and pigments, etc., all of which are obviously stable towards the chlorine bleach and very alkaline (properties of all components). Particularly preferred as the dye are chlorinated phthalocyanines and aluminosilicate polysulfides which provide, respectively, pleasant green and blue hues. T1O2 can be used to whiten or neutralize broken shades.

The liquid DLAV compositions of the present invention are easy to use in a known manner for washing plates, other kitchen utensils, etc. in an automatic dishwasher 22 fitted with a suitable dispenser. detergent, in an aqueous wash bath containing an effective amount of the composition.

Although the invention has been described in particular in connection with its application to liquid detergents for automatic dishwashers, it is obvious to those skilled in the art that the advantages of thixotropy and physical stability which are obtained by the addition fatty acid can also apply to the replacement of clay or polymeric thickeners in other thixotropic suspensions based on clay or polymer, such as the scouring formulations in pastes described in the US patent AT. No. 3 985 668 above, dental pastes, etc ...

The following nonlimiting examples illustrate the invention.

All the quantities and proportions referred to here are expressed relative to the weight of the composition unless otherwise specified.

EXAMPLE 1

In order to demonstrate the effect of fatty acid as a thickener, liquid DLA formulations are prepared with various amounts of fatty acid as a thixotropic thickener (Experiments 1, 2 and 3) as shown in Table 1. For comparison , a similar composition is prepared (Test N * 4) corresponding to the composition of Example 1 of British Application GB-A-2,140,450, according to the procedure described in this example.

23 TABLE 1

Component Test # 1 Test # 2 Test # 3 Test # 4

Water 32.99 32.96 32.94 41.92 5 Stearic acid 0.03 0.06 0.08

Clay (gel white GP) - - - 3.00

Sodium silicate 10 (47.5% solution of

Na20: Si02 in the ratio 1: 2.4) 25.00 25.00 25.00 13.73

Sodium tripolyphosphate (substantially anhydrous, i.e. about 3% moisture) 12.00 12.00 12.00 12.00

Sodium tripolyphosphate hexahydrated 20.00 12.00 12.00 12.00 12.00

Sodium carbonate (anhydrous) 7.00 7.00 7.00 7.00

Sodium hypochlorite (13% active chlorine) 7.61 7.61 7.61 7.61

Surfactant (Dowfax 3B-2, 45% aqueous solution of (mono- and didecyl-diphenyl oxide) Na di-sulfonate 0.80 0.80 0.80 0.80

Antifoaming agent (Knapsack LPKn 158), mixture of mono- and distearyl esters (C ^ gC ^ g) of phosphoric acid, molar ratio approximately 1: 1.3 0.16 0.16 0.16 0, 16 5 Caustic soda solution (50% NaOH) 2.40 2.40 2.40 2.40

Dye (Green

Graphitol) 0.01 0.01 0.01 0.01 10 100.00 100.00 100.00 100.00

A sample of each of the formulations of Tests N * 2 and 3 and of the comparative clay-based formulation (Test N * 4) is subjected to the measurement of shear stress using the apparatus.

Haake RV-3 as described above to determine the thixotropy index and the flow limit. The results are shown in the attached single Figure on which curve 1 is based on the sample from Trial N * 4, curve 2 is based on the sample from Trial N * 2, and curve 3 is based on the sample from Test N * 3. The value of the flow limit - the maximum value of the shear stress, S- is shown in Table 2.

Other properties are also shown in Table 2, including apparent viscosity, h, measured on a 24 hour old sample using a Brookfield HATD viscometer, using an N * 4 spindle at 20 rpm. min (Τ = 22 ^ 1 * 0, density, capillary drainage speed, stability and centrifugation., Capillary drainage speed (VDC) is a measure of stability, higher values indicating greater The VDC measurements are carried out by the following procedure: Whatman N * 1 filter paper, on which a 6.4 cm diameter circle is drawn, is placed on a 10 cm × 10 cm flat glass plate. A plastic tube 6.4 cm long and 3.4 cm in diameter is placed upright in the center of the circle and filled with the DLAV liquid composition sample (after standing The time required for the solvent to escape from the tube by infiltration and reach 10 the circle drawn. Time is measured on three sides of the circle and averaged. Shorter times mean that the gel does not properly retain the solvent (water) which can then permeate the filter paper. Times greater than about 7-15 minutes (all samples) are acceptable. The stability measurement is carried out by placing the sample in a glass bottle, left at room temperature, and noting the percentage of separation after 4 weeks. The centri-20 fugation test is also a measure of stability. Glass centrifuge tubes are filled with equal volumes of each sample and are rotated vertically, i.e. in a plane parallel to the ground, in a Sorwall centrifuge, for 25 minutes at 500 rpm. The volume of clear liquid is then measured. The results are reported in terms of the ratio of the height of clear liquid to the total height of sample, multiplied by 100, i.e. Height of clear liquid x100: 30. Total liquid height smaller numbers indicate greater stability.

26 TABLE 2

Property Test n * 1 Test n * 2 Test n‘3 Test n * 4 Viscosity, mPa.s 11 460 10 660 11 260 5 100 5 Flow limit Pa - 37.2 72.0 39.2

Density, g / ml 1.35 1.36 1.34 1.37 VDC (minutes) - 8.5 10.0 7.0] _q Stability (4 weeks at room temperature),% separation <1.0 0.0 0.0 5.0 d_5 Centrifugation <1.0 0.0 0.0 5.0

The results of Table 2 clearly show the superior stability with respect to phase separation of the formulations based on stearic acid, compared with the formulation based on clay. These results, associated with the thixotropic characteristics indicated by the graphic representations of the drawing, further demonstrate the superiority of the formulations of the invention with regard to pouring out of the dispenser compartment of the dishwasher.

25 EXAMPLE 2

Each of the formulations of Tests 1 to 4 of Example 1 is tested to compare the cleaning action (accumulation of stains and films on the glasses) using a Kenmore 30 dishwasher using tap water at a temperature of 54 * C and a hardness of 120 millionths. The testing process is described in ASTM D3566-79, except that only four cleaning cycles are used. The fr 27 formation of films and the formation of spots are evaluated according to the following rating scales: Evaluation scale of film formation 1. The best, no visible film 2. Light film, becomes visible 5 3. Appreciable film, increase 4. Continuous increase of a large film 5. Film formation becomes excessive 6. Strong film formation, excessive accumulation 7. Continuous increase in excessive film Scale for assessment of stain formation A. Best - no stains 10 B. Very few visible stains C. Distinct stains D. Significant overlap of around 50%

The results are indicated on table 3: TABLE 3

Test N * Behavioral evaluation

Film stains 15 1 B 1.2 2 B, C 1.2 3 B, C 2.3 4 C 2.3 EXAMPLE 3

Results similar to those described above are obtained by replacing stearic acid with isostearic acid, myristic acid, palmitic acid, lauric acid, dimer acid Emphol, trimer acid Emphol or the polyacid Emphol 1052.

In addition to their superior physical stability, thixotropy and cleansing properties, the compositions of the present invention have another important advantage of not requiring any particular order of addition of the respective ingredients. The 28 ingredients can all be added in any order or simultaneously in a single container, mixer, etc ... and stirred until a uniform homogeneous mixture is obtained. The mixing can be carried out at room temperature or at elevated temperature. It is not necessary to premix any of the ingredients or to use different shear mixing conditions.

Claims (12)

1. A gel-like thixotropic aqueous liquid cleaning composition, characterized in that it comprises water, at least one ingredient chosen from an organic detergent, a chlorine bleach, a detergency builder, a sequestering agent , foam inhibitors, abrasive particles, and mixtures thereof, and about 0.03 to about 0.5 percent by weight, based on the total composition, of a mono- or polycarboxylic acid having 8 to 22 carbon atoms, or dimers or trimers of such an acid. 2. A thixotropic aqueous composition for an automatic dishwasher, characterized in that it comprises, approximately by weight: 15 (a) 5 to 35% of alkali metal tripolyphoshate; (b) 2.5 to 40% sodium silicate; (c) 0 to 9% alkali metal carbonate; (d) 0.1 to 5% of an organic material with a detergent action, dispersible in water and stable with respect to the chlorine bleach; (e) 0 to 5% of foam inhibitor stable against the chlorine bleach; (f) a chlorine compound as a chlorine bleach, in an amount capable of providing about 0.2 to 4% of active chlorine; (g) 0.03 to 0.5% of an aliphatic fatty acid having 8 to 22 carbon atoms, of dimers or trimers of this acid; (H) 0 to 8% sodium hydroxide; and (i) the rest of the water. -: 3. Composition 'according to claim 2, characterized in that the aliphatic fatty acid (g) f 30 4 has about 10 to 20 carbon atoms. 4. Composition according to claim 3, characterized in that the fatty acid contains about 12 to 18 carbon atoms. 5. Composition according to claim 2, characterized in that the fatty acid is stearic acid. 6. Composition according to claim 2, characterized in that the fatty acid (g) is present in a proportion of approximately 0.03 to 0.2%. 7. Composition according to claim 5, characterized in that the fatty acid (g) is present in a proportion of about 0.03 to 0.08%. 8. Composition according to claim 2, characterized in that the chlorine bleaching compound (f) is sodium hypochlorite. 9. Composition according to claim 2, characterized in that it contains at least about 0.1% by weight of the foam inhibitor (e). 20 10 · Composition according to claim 9, characterized in that the foam inhibitor is an alkyl acid phosphate or an alkyl ester of phosphonic acid containing one or two C12 alkyl groups ~ ^ 20 '0U a m®lan9e these. 11. Composition according to claim 2, characterized in that it has a pH of approximately 10.5 to approximately 13.5. 12. Method for washing soiled dishes in an automatic dishwasher, characterized in that it consists in contacting soiled dishes - present in an automatic dishwasher with an aqueous washing bath containing, with dispersed state, an effective amount of the composition according to claim 2.