NL8700019A - TRIXOTROPE AQUEOUS SUSPENSIONS WITH IMPROVED STABILITY. - Google Patents

Description

VO 8529

Title: Tixotropic aqueous suspensions with improved stability.

The present invention relates to thixotropic aqueous suspensions with improved physical stability. More particularly, this invention relates to the use of long fatty acids as a thixotropic agent to form stable gel-like liquid suspensions suitable for use as a liquid detergent composition for automatic dishwashers.

The present invention particularly relates to detergent compositions for automatic dishwashers with thixotropic properties, an improved chemical and physical stability and an increased apparent viscosity, which are readily dispersible in the washing medium and to an effective cleaning of the dishes, glassware, porcelain and the like.

Commercially available household dishwashing detergents that are delivered in powder form have various drawbacks, such as the non-uniform composition; a necessary expensive preparation method? the tendency to crumble when stored at high humidity, leading to lump formation, which lumps are difficult to disperse; dust, a source of particular irritation to allergy sufferers, as well as the tendency to clump in the dispenser of the dishwasher. However, liquid forms of such compositions generally cannot be used in automatic dishwashers because of the high foam levels, the unacceptably low viscosities and the exceptionally high alkalinity.

Recent research and development activities have focused on the gel or "tixotropic" form of such compositions, which are insufficiently viscous to remain "anchored" in the machine's dispenser and additionally a smudged residue on dishes, glassware, china and the like leave behind. Ideally, thixotropic detergents should be highly viscous, bingham plastic in their dormant state, and have a relatively high flow value. However, when subjected to shear stresses, for example when shaking in a container ✓ or squeezing through a narrow opening, they should fluidize quickly while returning to the high viscosity / Bingham plastic state when the applied shear stress is stopped. .

Stability is also of great importance, i.e. there should be no significant phase separation or leakage after long standing.

It is thus problematic to provide a bile form composition for an automatic dishwashing machine having the aforementioned properties, in particular as regards compositions for use in household dishwashers. For effective use, it is generally recommended that the automatic dishwashing detergent, hereinafter also referred to as ADD, contain (1) sodium tripolyphosphate (NaTPP) for softening or bonding the hard water minerals and for emulsifying and / or peptizing soil; (2) sodium silicate to provide the alkalinity necessary for effective washing power and protection of fine porcelain enamel and cartridges; (3) sodium 15 carbonate, generally considered optional, for improving alkalinity; (4) a chlorine releasing agent to promote the removal of stains that give rise to water stains, and (5) defoamer / surfactant to reduce the foam, thereby increasing the efficiency of the machine and obtaining the required washing power. See, for example, SDA Detergents in Depth, "Formulations Aspects of Machine Dishwashing", Thomas Oberle (1974).

Cleansers approximating the aforementioned compositions are usually liquids or powders. Combining such ingredients into a gel form effective for use in household machines has proved difficult. Typically, in such a composition, hypochlorite bleach is omitted since it can react with other chemical active components, especially the surfactant, to degrade the suspension or triotropic agent and deteriorate its effect.

Thus, U.S. Patent 4,115,308 describes thixotropic automatic dishwashing pastes containing a suspending agent such as CMC, synthetic clays and the like; inorganic salts including silicates, phosphates and polyphosphates; contain a small amount of a surfactant and a suds suppressor.

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No bleach is described. The U.S. patent. 4,147,650 is somewhat similar, and includes an optional Cl (hypo-chlorite) bleach but no organic surfactant or suds suppressor. In addition, the product is described as a wax-5 suspension without apparent thixotropic properties.

U.S. Patent 3,985,668 discloses abrasive cleaners of a gel-like consistency that (1) contain a suspending agent, preferably the smectite and attapulgite-type clays; (2) an abrasive, for example silica sand or perlite; 10 and (3) a filler consisting of low-density polymer powders, expanded perlite and the like, which have buoyancy and thus exert a stabilizing effect on the composition in addition to acting as a filler, thereby replacing water that otherwise contributes to an undesired top layer formation due to settling and phase stabilization. The aforementioned are the essential components. Optional components include hypochlorite bleach, bleach-stable surfactants and buffers, for example, silicates, carbonates and monophosphates. Builders such as NaTPP may also be included as further optional components that provide or supplement a building action that is not provided by the buffer, the amount of such a builder being no more than 5% of the total composition, according to the patent. Maintaining the desired (more than) pH 10 levels is achieved by the buffer / builder components. High pH is said to minimize decomposition of the chlorine bleach 25 and the undesired interaction between surfactant and bleach. When NaTPP is present, this is limited to 5% as stated. No foam suppressant is described.

In British patent applications 2.116.199A and 2.140.450A, from. questioner, liquid ADD compositions are described having properties that characterize a desired thixotropic gel-type structure and comprising each of the various ingredients necessary for effective washing ability with an automatic dishwasher. The normal gel-like aqueous automatic dishwashing detergent composition with thixotropic properties comprises the following ingredients, by weight: 8700019

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- 4 - (a) 5-35% alkali metal tripolyphosphate; (b) 2.5-20% sodium silicate; (c) 0-9% alkali metal carbonate; (d) 0.1-5% chlorine bleach-stable, water-dispersible organic detergent material; (e) 0-5% suds suppressor stable to the chlorine bleach; (f) chlorine bleach in an amount to provide 0.2-4% available chlorine; (G) tixotropic thickener in an amount sufficient to give the composition a tixotropy index of about 2.5-10; and (h) sodium hydroxide to adjust the pH if necessary.

ADD formulations so formulated are low foaming; easily soluble in the wash medium and very effective at the pH-15 values which are most favorable for improved cleaning capacity, i.e. pH 10.5-13.5. The compositions normally have a gel-like consistency, i.e., a highly viscous, opaque jelly-like material with Bingham plastic character and thus with relatively high yield values. Thus, a clear shear force is necessary to initiate or increase flow, as would be obtained within the stirred dispenser of a working automatic dishwasher. Under such conditions, the composition is rapidly fluidized and easily dispersed. When the shearing force is interrupted, the fluid composition quickly returns to a high viscosity, Bingham plastic state close to its previous consistency.

U.S. Patent 4,551,487 describes a low foaming detergent paste for dishwashers. The patented thixotropic detergent has a viscosity of at least 30 Pa.s at 20 ° C determined with a rotary viscometer at an axis speed of 5 rpm.

The composition is based on a mixture of finely divided hydrated sodium metasilicate, an active chlorine compound and a thickener which is a hectorite-type layered silicate. A small amount of nonionic detergents and alkali metal carbonates and / or hydroxides are useful.

The formation of organic clays through the interaction of 8700019 * i - 5 clays (such as bentonite and hectorite) with organic compounds such as quaternary ammonium salts has also been described (WS Mardis, JAOCS, Vob. 61, No. 2, p. 382 (1984)).

Although these previously described liquid ADD compositions do not have, or to a lesser extent, one or more of the above defects, it has been found that in actual practice, still further improvements in physical stability are required to extend the shelf life of the product and thereby improve consumer acceptance.

In a previously filed Serial No. 744,754 of July 14, 1985 and a partial continuation thereof, the physical stability of clay-based tixotropic liquid compositions is improved by adding to them small amounts, for example 0.02 to 1 weight percent of a polyvalent metal salt of a long fatty acid, such as aluminum stearate . While the combination of clay thickener and fatty acid salt stabilizer provides satisfactory long-term stability, such as absence of phase separation for up to 12 weeks or more, the addition of clay to these compositions has certain drawbacks.

For example, when using clay thickeners, the addition of the various ingredients and the control of process conditions during formulation of the composition is critical to obtain the desired thixotropic properties and low foaming properties.

In addition, clay thickeners are expensive materials which considerably increase the price of the end product for the consumer. In some cases, the clay thickeners can actually interfere with the total washing capacity.

It is thus an object of the invention to provide stable thixotropic aqueous suspensions which prevent the use of clay thickeners.

It is another object of the invention to provide liquid ADD compositions with thixotropic properties that have improved physical stability and improved rheological properties.

It is a still further object of the invention to provide 35 tixotropic liquid ADD compositions with reduced levels of 8700019 * - 6 - thixotropic thickener without the generally high viscosities at low shear rates and the lower viscosities at high shear rates, which are typically are adversely affected for the desired thixotropic properties.

More generally, it is an object of this invention to provide stable aqueous thixotropic non-clay based compositions, in particular liquid detergent pastes or automatic dishwashing gels, by incorporating in the clay-free aqueous suspension a minor amount of a fatty acid which effectively prevents the settling of the suspended particles and prevents phase separation.

These and other objects of the invention, which are described in detail below, are achieved by incorporating a small but effective amount of a non-clay, non-polymeric thixotropic agent which is a long fatty acid into an aqueous liquid detergent composition. More particularly, according to a preferred and specific embodiment of the invention, there is provided a normal gel-like detergent composition for automatic dishwashers incorporating about 0.03-0.5 weight percent based on the composition of a long fatty acid that effectively settles the suspended particles, such as an alkali metal builder salt, etc., without the need for any clay, polymer or other thickeners. In this particular aspect, the present invention provides a normal gel-like aqueous detergent composition with thixotropic properties intended for automatic dishwashers, comprising by weight: (a) 5-35% alkali metal tripolyphosphate; (b) 2.5-40% sodium silicate; (c) 0-9% alkali metal carbonate; (D) 0.1-5% chlorine bleach stable, water dispersible organic detergent material; (e) 0-5% chlorine bleach-stable foam-reducing agent; (fj chlorine bleach in an amount providing about 0.2 "- 4% / available chlorine; 35 (g) 0.03 - 0.5% of a long fatty acid;. 8700019 - 7 - (h) 0-8% sodium hydroxide ; and (i) with residual water.

Also, in connection with this particular aspect, the invention provides a method of cleaning dishes in an automatic dishwashing machine with an aqueous washing bath containing an effective amount of the liquid automatic dishwashing detergent (LADD) described above. According to this aspect of the invention, the LADD composition can be easily poured into the automatic dishwashing machine's dispenser and will quickly thicken to its normal gel-like or paste-like state within seconds and thus be maintained within the dispenser until shear forces are applied again such as by the water jet from the dishwasher.

The invention will now be described in more detail with reference to specific embodiments thereof and with the aid of the following drawing, in which the figure is a graphical representation of the tixotropy index of two different compositions according to the invention and a clay-thickened liquid detergent for an automatic dishwasher as described in GB 2 140 450A.

The LADD products as described in the aforementioned GB 2 116 199A, 20 GB 2 140 450A and U.S. Application No. 744 754 as well as their continuation exhibit improved rheological properties when evaluated by examining product viscosity as a function of shear stress. The compositions exhibit a high viscosity at a low shear stress and a low viscosity at a high shear stress, the data indicating efficient fluidization and gelling well within the shear rates existing within the standard dishwasher. In practical terms, this means improved pouring and process properties as well as less leakage in the machine dispenser, compared to the known liquid or gel 30 ADD products. For applied shear rates corresponding to 3-30 rpm, viscosities (Brookfield) correspond in the range from about 10,000 - 30,000 cps to about 3,000 - 7,000 cps, measured at room temperature using an LVT Brookfield viscometer after 3 minutes on a No. 4 axis. A shear rate of 7.4 seconds-35 den * corresponds to an axis speed of approximately 3. An approximate 8700019 - 8 -

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a tenfold increase in shear rate produces an approximately 3 to 9fold decrease in viscosity. Thus, the compositions of applicant's younger invention exhibit threshold fluidizations at lower shear rates and of significantly greater magnitude expressed in incremental shear rate increases versus incremental decrease in viscosity. This property of the LADD products of the younger invention is summarized in terms of a tixotropy index (TI) which is the ratio of the apparent viscosity at 3 rpm and at 30 rpm. The previous compositions have a TI of 2-10. The LADD-10 formulations should exhibit a nearly complete and rapid return to the previous resting state consistency when the shear stress is interrupted.

Although the determination of the tixotropy index TI as a ratio of apparent viscosity at 3 and 30 rpm provides a satisfactory measure of product usability, further research and experience has shown that a more reliable measure of the tixotropy index and product usability as a liquid ADD is provided by determining the thixotropy as a measure of the area in the hysteresis loop that results from plotting the shear stress S under the conditions described below as a function of the shear rate, η, when the shear rate is from 0 to the maximum value is increased and then returned to O. The larger the area in the hysteresis loop, the larger the tixotropy index. Expressed in apparent viscosity, it has also been determined that as long as the viscosity at room temperature (22 ± 1 ° C) measured in a Brookfield viscometer EEATD, using a No. 4 shaft at 20 rpm, is less than about 20,000 cps. composition can be easily shaken, such that a tixotropic composition can be easily "fluidized" or "liquefied" to deliver the product through a conventional squeeze bottle or other suitable dispenser.

The present invention is based on the surprising discovery that the same or improved rheological properties and physical stability, i.e. resistance to phase separation, settling, etc.

As in these previous liquid aqueous ADD compositions, achievable 8700019 -9- *> * is at a significantly lower price and without any particular process conditions due to the composition a small but effective amount of a long fatty acid instead of the clay -tixotropic thickener and where applicable also add the metal salt of the fatty acid. At the same time, improvements in stain removal and film capacity can be achieved (i.e. less stains and reduced film formation).

As an example of improving the rheological properties over a standard clay-based tixotropic liquid aDD, reference is made to the accompanying drawing which is a graph of the shear stress S as a function of the shear rate η, for a clay-based Is LADD (3 weight percent clay) (curve 1) and for two similar LADD compositions in which the clay has been replaced by 0/06 weight percent stearic acid (curve 2) or by 0.08 weight percent stearic acid (curve 3). The shear stress S is measured in a static test with a Haake RV-3 machine fitted with a coaxial tray. The sample is placed in the outer tray and the inner tray is rotated by the machine at progressively higher shear rates up to a maximum of 113 seconds * after which the shear rate is gradually reduced to 0. The reaction is automatically written down as the shear stress. The experiments were performed with an MV IX sensor system (constant values A = 3.76, Pa, M = 0.9 sec. *). The area between the curved lines obtained for each sample is a measure of the tixotropy, with larger areas indicating a higher tixotropy. The yield point of each sample can also be determined from the curves shown in the figure; the yield point is the maximum stress in the shear stress versus shear rate curve. At the same time, the physical stability is such that even after 6 weeks or more in temperature ranges, extending from near freezing point to 40 ° C or more, the compositions containing the fatty acid thickeners do not undergo visible phase separation.

Preferred long fatty acids are the higher aliphatic monocarboxylic acids having about 8 to about 22 carbon atoms, preferably about 10 to 20 carbon atoms and especially about 12 to 18 35 carbon atoms, including the carbon of the carboxyl 8700019

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- ίο - group of the fatty acid. Polycarboxylic acids can also be used. The aliphatic group can be saturated and unsaturated or straight or branched. Preferred are branched or saturated fatty acids. Mixtures of fatty acids, such as those derived from natural sources, such as tallow fatty acid, coconut fatty acid, soy fatty acid, etc., or from synthetic sources available from industrial manufacturing processes can be used. Thus, examples of the fatty acids which can be used as thickeners instead of clay or polymer thickeners are, 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 . The dimers or trimers of these acids can also be used. Stearic acid and mixed fatty acids such as coconut fatty acid are preferred.

Within the ranges of the carbon lengths of the monocarboxylic acids as indicated herein, the viscosity of the product tends to decrease as the number of carbon atoms in the monocarboxylic fatty acid decreases. No systematic tendency for the dimers or trimers or polybasic carboxylic acids has been observed.

The amount of the fatty acid thickener to achieve the desired value of the thixotropy and physical stability depends on factors such as the nature of the fatty acid, the detergent compound, inorganic salts, in particular TPP, other LADD ingredients, as well as the expected storage and transport conditions.

Generally, however, amounts of the tixotropic fatty acid agent provide in the range of from about 0.03 to 0.5%, preferably from about 0.03 to 0.2%, especially from about 0.03 to 0.08% , the long term stability and absence of phase separation on standing and during transport at both lower and elevated temperatures, as is necessary for a commercially acceptable product.

In general, however, the LADD effectiveness is proportional to (a) available chlorine levels; (b) alkalinity; (c) solubility in the wash medium and (d) suds suppression It is preferred here that the pH of the LADD composition is at least about 9.5, preferably about 10.5 to 13.5, especially at least about 11.5 is.

At the relatively low pH values, the LADD product is too viscous, 8700019. I.e., solid, and thus is not easily fluidized at the shear force levels created within the dispenser under normal machine operating conditions.

In essence, the composition loses much if not all of its tixotropic 5 character. Addition of NaOH is often necessary to raise the pH to within the above ranges and improve the flowability properties. Sometimes, the presence of carbonate is also required, as this acts as a buffer that helps maintain the desired pH.

However, excess carbonate should be avoided as this can cause the formation of needle-like crystals of carbonate, which worsens the stability, thixotropy and / or detergent of the LADD product, as well as the pourability of the product from e.g. squeeze tube bottles are deteriorated.

Lye (NaOH) further serves to neutralize the phosphoric acid or phosphonic acid ester foam reducer when present.

Typically about 0.5 to 3 weight percent NaOH and about 2 to 9 weight percent sodium carbonate are in the LADD composition, although it is noted that sufficient alkalinity can also be provided by the NaTPP and sodium silicate.

The NaTPP can be used in the LADD composition in a range of about 8 to 35 weight percent, preferably about 20 to 30 weight percent, and preferably should be free of heavy metal that tends to decompose the preferred sodium hypoclorite or other chlorine bleach or deactivate. The NaTPP can be anhydrous or hydrated including the stable hexahydrate with a degree of hydration of 6 corresponding to about 18 weight percent water or more.

In fact, in view of the stability of the hexahydrate, the presence of some hydrate water which is believed to be

It acts to form seed crystals of the stable hexahydrate thereby promoting hydration and solubilization of the remaining NaTPP particles. If only the hexahydrate is used, the detergent product may be too liquid and have little or no triotropic character. Conversely, if only the anhydrous NaTPP

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When used, the product may in some cases be too thick and therefore unsuitable. Particularly preferred LADD compositions are obtained, for example, using a 0.5: 1 to 2: 1 weight ratio of anhydrous to hexahydrate NaTPP, with values of about 1: 1 being particularly preferred.

Foam suppression is important to increase the effectiveness of the dishwasher and minimize the destabilizing effects that may occur in the presence of excess foam in the washing machine during use. Foam can be sufficiently reduced by an appropriate choice of the type and / or amount of detergent material, the main foam-producing component. The degree of foam also depends, somewhat, on the hardness of the washing water in the machine, whereby an appropriate adjustment of the amounts of NaTPP, which has a water softening effect, may be conducive to providing the desired degree of foam suppression. However, it is generally preferred to include a suds suppressor or inhibitor stable to the chlorine bleach. The alkylphosphonic acid esters of the formula HO-P (aO) (-OR) -R are particularly effective,

Which is available, for example, from BASF-Wyandotte (PCUK-PAE), and in particular the alkyl acid phosphate esters of the formula HO-P (= 0) (- OR) -OR

which are preferably available from Hooker (SAP) and Knapsack (LPKn-158), in which case one or both R groups in each type of ester can independently represent an alkyl group. Mixtures of the two types or any other chlorine bleach stable type, or mixture of mono- and diesters of the same type are useful. Particularly preferred is a mixture of mono and di-C 1-6 alkyl acid phosphate esters, such as monostearyl / distearyl acid phosphates 1,2 / 1 (Knapsack). When used, amounts of 0.01 to 5 weight percent, preferably 0.1 to 5 weight percent, especially about 0.1 to 0.5 weight percent, foam suppressant in the composition are typical, the weight ratio of the detergent component (d) until the suds suppressor (e) generally ranges from 10: 1 to 1: 1 and preferably is about 4: 1 to 1 µ1. Other 8700019 * * - - 13 - useful defoamers include, for example, the well-known silicones.

Although any chlorine bleaching agent, such as dichloroisocyanurate, dichlorodimethylhydantoin or chlorinated TSP, may be used in the composition of this invention, alkali metal, for example, potassium, lithium, magnesium and especially sodium hypochlorite is preferred. The composition should contain enough chlorine bleach to provide about 0.2 to 4.0 weight percent available chlorine, as determined, for example, by acidifying 100 parts of the composition with excess hydrochloric acid. A solution containing about 0.2-4.0 weight percent sodium hypochlorite or providing roughly the same percentage of available chlorine. Particularly preferred is about 0.8-1.6 weight percent available chlorine. For example comb. sodium hypochlorite (NaOCl) solution with about 11 to about 13% available chlorine in amounts of 3 to 20%, preferably about 7 to 12%, are advantageously used.

The sodium silicate providing alkalinity and hard surface protection, such as fine china glaze and cartridges, is used in an amount in the range of about 2.5 to 40 weight percent, preferably about 10 to 35 weight percent, in the composition.

At the higher levels specified herein, for example at levels above about 10 weight percent, the silica also provides increased anti-staining activity. The sodium silicate is generally added in the form of an aqueous solution, preferably with a Na 2 O: SiO 2 ratio of about 1: 2.2 to 1: 2.8, for example 1: 2.4. Most other components of the composition, such as NaOH, sodium hypochlorite and suds suppressor, can also be added in the form of an aqueous dispersion or solution.

The detergent material useful herein should be stable in the presence of the chlorine bleach, especially the hypochlorite bleach, with those of the organic anionic, amine oxide, phosphine oxide, sulfoxide, or betaine water-dispersible surfactant types being preferred, and the aforementioned anionics most preferred. They are supplied in amounts ranging from about 0.1% to 5%, preferably about 0.3% to 2.0%, in the range 8700019 ο · ν ......

- 14 - applied. Particularly preferred surfactants herein include the straight or branched alkali metal mono- and / or di (C) alkyl diphenyl-0-14 oxide mono- and / or disulfates, commercially available as, for example, DOWFAX (registered trademark) 3B-2 and DOWFAX 2A- 1.

5. Generally, the paraffin sulfonates tend to deteriorate if not destroy the tixotropy since they have been found to increase the viscosity undesirably causing serious shear problems. In addition, the surface active agents must be compatible with the other components of the composition.

Other suitable surfactants include the primary alkyl sulfates, alkyl sulfonates, alkyl aryl sulfonates, and sec alkyl sulfates. Examples include sodium C 1 -alkyl sulfates, such as sodium dodecyl-10-10 phosphate and sodium tallow alcohol sulfate; sodium C 1 -C 4 g alkane sulfonates, such as sodium hexadecyl-1-sulfonate, and sodium C 1 -C 5-alkyl benzene sulfonates, such as sodium dodecyl benzene sulfonates. The corresponding potassium salts are also useful.

As other suitable surfactants or detergents, the amine oxide surfactants typically have the structure of R ^ R ^ NO, wherein each R has a lower alkyl group, such as methyl, and R * 20 has a long alkyl group of 8-22 carbon atoms, such as a lauryl, represents myristyl, palmityl or cetyl group. Instead of an amine oxide, a corresponding surface-active phosphine oxide R 1 R 1 P 0 or 1 sulfoxide RR SO can be used. Betaine surfactants typically have the structure R 1, R 1, N R '' C00 in which each R represents a lower alkylene group of 1 to 5 carbon atoms. Specific examples of these surfactants include lauryl dimethylamine oxide, myristyl dimethylamine oxide, the corresponding phosphine oxides and sulfoxides, and the corresponding betaines including dodecyldimethyl ammonium acetate, tetradecyldiethyl ammonium pentanoate, hexadecyldimethyl 30 ammonium hexanoate. For biodegradability, the alkyl groups in these surfactants should be straight and such compounds are preferred.

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

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The amount of water present in these compositions should, of course, be neither so high as to cause an undesirably low viscosity and fluidity nor so low as to produce an undesirably high viscosity and low fluidity, reducing or destroying thixotropic properties in both cases. . Such amount is readily determined by routine testing at any time, and generally ranges from about 25 to 75 weight percent, preferably about 55 to 65 weight percent.

The water should also preferably be deionized or softened.

Other conventional ingredients may be included in these compositions in small amounts, generally less than about 3 weight percent, such as perfume, hydrotope agents such as sodium benzene, toluene, xylene and cumene sulfonates, preservatives, fillers and pigments and the like, all of which stable to the chlorine bleach and high alkalinity (properties of all components). Particular preference for coloring is the chlorinated phthalocyanines and polysulfides of aluminosilicate which provide pleasant green and blue shades, respectively. TiCl2 can be used for whitening or neutralizing shade.

The liquid ADD compositions of this invention are readily used in any known manner for washing the dishes, other utensils and the like in an automatic dishwashing machine equipped with a suitable detergent tray, in an aqueous wash bath containing an effective amount of the composition.

While the invention has been particularly described in connection with its application to liquid detergents for automatic dishwashers, it will be appreciated that the benefits of the thixotropy and physical stability obtained by the addition of the fatty acid also apply to the replacement of clay or polymeric thickeners in other clay or polymeric tixotropic suspensions, such as the abrasive paste compositions described in the aforementioned U.S. Patent 3,985,668, toothpaste and the like.

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The invention can be practiced in various ways and a number of specific embodiments will now be described to illustrate the invention with reference to the following examples. All amounts and parts as stated herein are by weight of the composition unless otherwise indicated.

EXAMPLE I

In order to demonstrate the effect of the fatty acid thickener, liquid ADD compositions are prepared with different amounts of the fatty acid tixotropic thickener (Runs 1.2 and 3), as shown in Table A. For comparison, a similar composition (Run No. 4) ) corresponding to the composition of Example 1 of GB 2,140,450A prepared according to the procedure described in that example.

TABLE A

Component Test Test Test Test No. 1 No. 2 No. 3 No. 4 15 Water 32.99 32.96 32.94 41.92

Stearic acid 0.03 0.06 0.08

Clay (Gel White GP) - 3.00

Sodium silicate (47.5% solution of Na2O: SiQ2, ratio 1: 2.4) 25.00 25.00 25.00 13.73

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

Sodium tripolyphosphate hexahydrate 12.00 12.00 12.00 12.00

Sodium carbonate (anhydrous) 7.00 7.00 7.00 7.00

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

Surfactant (Dowfax® 30 3B-2, 45% Na-mono- and di-decyl-diphenyloxidisulfonate aqueous solution) 0.80 0.80 0.80 0.80 87-0 0 0 1 9 -17-.

TABLE A (continued)

Component Test Test Test Test No. 1 No. 2 No. 3 No. 4

Anti-foaming agent (Knapsack) 5 LPKn 158, mixture of mono and di-stearyl (C 1 -C-C-gjalkyl esters of phosphoric acid, molar ratio about 1: 1.3 0.16 0.16 0.16 0.16

Caustic solution (50% NaOH) 2.40 2.40 2.40 2.40 10 Color (Graphitol Green) 0.01 0.01 0.01 0.01 100.00 100.00 100.00 10.00

A sample from each of the compositions of Runs Nos. 2 and 3 and the similar clay-based formulation (Run No. 4) is subjected to shear measurement with the Haake RV-3-15 machine as described above to determine the tixotropy index and the yield point. The results are shown in the accompanying figure in which curve 1 is based on the sample of Test No. 4, curve 2 is based on the sample of Test 2, and curve 3 is based on the sample of Test No. 3. The value of the yield point - the maximum value of the shear stress S - is shown in table B.

Other properties are also listed in Table B, including the apparent viscosity η, measured on a 24 hour old sample with a Brookfield HATD viscometer using a No. 4 shaft at 20 rpm (T = 22 ± 1 ° C ); density, capillary draining rate, stability and centrifugation. Capillary Drain Rate (CDR) is a measure of stability where higher values indicate higher stability. The CDR measurements are carried out using the following procedure: No. 1 Whatman filter paper with a drawn circle having a diameter of 6.4 cm is placed on a flat glass plate 10 cm x 10 cm. A plastic tube, 6.4 cm long, 3.4 cm diameter, is placed in the upright position, centrally on the circle. The tube is filled with the sample of the liquid ADD composition (after standing for 1 day).

8700019 V * · £ »- 18 -

The time it takes for the solvent to seep out of the tube and reach the drawn circle is measured. Time is measured on three sides of the circle and averaged. Faster times mean that the gel cannot successfully retain the solvent (water) that then leaks into the filter paper. Hours greater than about 7 minutes (all samples) are acceptable. The stability measurement is carried out by placing the sample in a glass bottle, leaving it at room temperature and observing the percentage separation after 4 weeks. The centrifugation test is also a measure of stability.

The 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, at 500 rpm for 25 minutes. The volume of clear liquid is then measured. Results are reported as the ratio of the height of the clear liquid to the total height of the sample multiplied by 100 i.e. height clear liquid / total height liquid x 100. Lower numbers indicate greater stability.

TABLE B

Property Test Test Test Test No. 1 No. 2 No. 3 No. »4 20 Viscosity, cps 11,460 10,660 11,260 5,100

Yield point, dynes / cm2 372 720 392

Density, g / ml, 1.35 1.36 1.34 1.37 CDR (minutes) - 8.5 10.0 7.0

Stability (4 weeks R.T.), 25% separation <1.0 0.0 0.0 5.0

Centrifugation <1.0 0.0 0.0 5.0

The data in Table B clearly demonstrate the superior phase separation stability of the stearic acid based compositions compared to the clay based composition.

.30 These results coupled with the tixotropy properties indicated by the graphical representation in the figure further demonstrate the superiority of the composition of the invention 870 0 0 1 9 * -19--

with regard to leakage in the dishwasher's dispenser. EXAMPLE II

Each of the compositions of Tests 1-4 of Example I is tested for comparison of cleaning power (formation of 5 stains and films on glassware) with a Kenmore dishwasher using tap water at a temperature of 55 ° C and a hardness of 120 ppm. The test procedure is described in ASTM D3566-79, with the exception that only four cleaning cycles have been used.

The film and staining are rated according to the following scales: 10 Film rating scale 1. Very good, no film visible 2. Light film formation, becomes visible 3. Observable film, increases 4. Continuous increase of a significant film 15 5. Film formation becomes excessive 6. Film formation large, excessive build-up. 7. Continued increase of excessive film

Stain rating scale A. Very good - no stains 20 B. Only very few stains visible C. Clear stains D. Significant stain coverage, approx. 50%.

The results are shown in Table C.

TABLE C

25 No. Test Quality Assessment

Stains Film 1 B 1.2 2 B, C 1.2 3 B, C 2.3 30 4 C 2.3

EXAMPLE III

Similar results to those described above were obtained when replacing the stearic acid with isostearic acid, 8700019

V

- 20 - myristic acid, palmetic acid, lauric acid, Emphol dimer acid, Emphol trimer acid or Emphol 1052 polybasic acid.

In addition to superior physical stability, thixotropy and cleaning capacity, the compositions of this invention have the additional significant advantage of not requiring any particular order of the respective ingredients. All ingredients can be added in any order or simultaneously in a single vessel, mixer, etc. and stirred until a uniform homogeneous mixture is obtained. Mixing can be performed at room temperature or elevated temperature. It is not necessary to pre-mix any of the ingredients or apply different shear mixing conditions.

8700019

Claims (12)

An aqueous gel-like thixotropic liquid cleaning composition comprising water, at least one component selected from organic detergents, chlorine bleaches, detergent builders, sequestering agents, suds suppressors, abrasive particles and mixtures thereof, and about 0.03 to about 0.5 weight percent based on the total composition of a mono- or polycarboxylic acid with 8-22 carbon atoms or the dimers or trimers thereof. Aqueous tixotropic automatic dishwashing machine composition comprising approximately by weight: 10 (a) 5 - 35% alkali metal tripolyphosphate; (b) 2.5 - 40% sodium silicate; (c) 0-9% alkali metal carbonate; (d) 0.1-5% water-dispersible organic detergent material stable to the chlorine bleach; (E) 0-5% foam suppressor stable to the chlorine bleach; (f) Chlorine bleach in an amount providing about 0.2-4% available chlorine; (g) 0.03-0.5% of an aliphatic fatty acid of 8-22 carbon atoms, 20 dimers thereof or trimers thereof; (h) 0-8% sodium hydroxide; with (i) residual water. Composition according to claim 2, characterized in that the aliphatic fatty acid (g) contains about 10-20 carbon atoms. Composition according to claim 3, characterized in that the fatty acid contains about 12-18 carbon atoms. Composition according to claim 2, characterized in that the fatty acid is stearic acid. Composition according to claim 2, characterized in that the fatty acid (g) is present in an amount of about 0.03 to 0.2%. S Composition according to claim 5, characterized in that the fatty acid (g) is present in an amount of about 0.03 to 0.08%. 8700019 - 22 - Composition according to claim 2, characterized in that the chlorine bleach (f) is sodium hypochlorite. Composition according to claim 2, characterized in that it contains at least about 0.1% by weight of the foam suppressor (e) 5. A composition according to claim 9, characterized in that the suds suppressor is an alkyl acid phosphate ester or an alkyl phosphonic acid residue with 1 to 2 carbonyl groups or a mixture thereof. 11. A composition according to claim 2, characterized in that it has a pH from about 10.5 to about 13.5. 12. A method of washing contaminated dishes in an automatic dishwasher comprising contacting the contaminated dishes in an automatic dishwasher with an aqueous washing bath in which an effective amount of the composition according to claim 2 is dispersed. 87 0 0 0 1 3