AU597612B2 - Thixotropic aqueous suspensions - Google Patents

Description

COMMONWEALTH OF AUSTRALI 9 2 Patent Act 1952 COMPLETE

SPECIFICATION

(ORIGINAL)

Application Number 713q187 Lodged Class Int. Class This document contains t;e amendments flowed under Section by the Su crvishig Examiner on and is correct for printing Complete Specification Lodged Accepted Published 7 January 1986 Priority S Related Art Name of Applicant Address of Applicant COLGATE-PALMOLIVE

COMPANY

300 Park Avenue, New York, New York 10022, United States of America Actual Inventory Address for Service Nagaraj S. Dixit F.B. RICE CO., Patent Attorneys, 28A Montague Street, BALMAIN 2041.

Complete Specification for the invention entitled: THIXOTROPIC AQUEOUS SUSPENSIONS The following statement is a full description of this invention including the best method of performing it known to usme:- I a OL o 00 d4 ~wQ THIXOTROPIC AQUEOUS SUSPENSIONS The application is related to commonly assigned prior application Serial No. 744,754 filed June 14, 1985 in the names of Drapier, et al orresp6nY 3g -h Ausfohvaa PC4"-IcI t\lo. SaSgs\ li ^e f\&e oF ogae- poM-l The present invention relates to thixotropic aqueous suspension with improved physical stability. More specifically the invention relates to the use of long chain fatty acids as a thixotropic agent for forming stable gel-like liquid suspensions suitable for use as liquid automatic dishwasher detergent composition.

The present invention specifically relates to automatic dishwashing detergent compositions having thixotropic properties, improved chemical and physical stability, and with increased apparent viscosity, and which are readily dispersible in the washing medium to provide effective cleaning of dishware, glassware, china and the like.

Commercially available household-machine dishwasher detergents provided in powder form have several disadvantages, e.g. non-uniform composition; costly operations necessary in their manufacture; tendency to cake in storage at high humidities resulting in the formation of lumps which are difficult to disperse; dustiness, a source of particular irritation to users who suffer allergies; and tendency to cake in the dishwasher machine dispenser. Liquid forms of such compositions, however, generally cannot be used in automatic dishwashers due to high foam levels, unacceptably low viscosities and exceedingly high alkalinity.

Recent research and development activity has focused on the gal or "thixocropic" form of such compositions,

II

-LYIYC 11 L 0 0 00 8 00 o 00 0 0 0

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0 0 o 0 00 S0 20 00 0 UO0 0 00 t o 20 insufficiently viscous to remain "anchored" in the dispenser cup of the dishwasher, and moreover yield spotty residues on dishware, glassware, china and the like. Ideally, thixotropic cleansing compositions should be highly viscous in a quiescent state, Bingham plastic in nature, and have relatively high yield values. When subjected to shear stresses, however, such as being shaken in a container or squeezed through an orifice, they should quickly fluidize and, upon cessation of the applied shear stress, quickly revert to the high viscosity/Bingham plastic state. Stability is likewise of primary importance, i.e. there should be no significant evidence of phase separation or leaking after long standing.

The provision of automatic-dishwasher compositions in gel form having the aforedescribed properties has thus far proven problematical, particularly as regards compositions for use in home dishwasher machines. For effective use, it is generally recommended that the automatic dishwashing detergent, hereinafter also designated ADD, contain (1) sodium tripolyphosphate (NaTPP) to soften or tie up hard-water minerals and to emulsify and/or peptize soil; sodium silicate to supply the alkalinity necessary for effective detergency and to provide protection for fine china glaze and pattern; sodium carbonate, generally considered to be optional, to enhance alkalinity; a chlorine-releasing agent to aid in the elimination of soil specks which lead to water spotting; and defoamer/surfactant to reduce foam, thereby enhancing machine efficiency and supplying requisite detergency. See, for example, SDA Detergents in Depth, "Formulations Aspects of Machine Dishwashing," Thomas Oberle (1974). Cleansers approximating to the afore- 0 u 0 00 0 j C' 00 o L3 D 2 described compositions are mostly liquids or powders. Combining such ingredients in a gel form effective for home-machine use has proved difficult. Generally, such compositions omit hypochlorite bleach, since it tends to react with other chemically active ingredients, particularly surfactant, thereby degrading the suspending or thixotropic agent and impairing its effectiveness. Thus, U.S. Patent 4,115,308 discloses thixotropic automatic dishwasher pastes containing a suspending agent, e.g. CMC, synthetic clays or the like; inorganic salts including silicates, phosphates and polyphosphate a small amount of surfactant and a suds depressor. Bleach is not disclosed. U.S. Patent No. 4,147,650 is somehwat similar, optionally including Cl-(hypochlorite) bleach but no organic surfactant or foam depressant. The product is described, moreover, as a detergent slurry with no apparent thixotropic properties.

U.S. Patent No. 3,985,668 describes abrasive scouring cleaners of gel-like consistency containing suspending agent, preferably the Smectite and attapulgite types of clay; abrasive, e.g. silica sand or perlite; and (3) filler comprising light density powdered polymers, expanded perlite and the like, which has a bouyancy and thus stabilizing effect on the composition in addition to serving as a bulking agent, thereby replacing water otherwise available for undesired supernatant layer formation due to leaking and phase destabilization. The foregoing are the essential ingredients. Optional ingredients include hypochlorite bleach, bleach stable surfactant and buffer, e.g. silicates, carbonates, and monophosphates. Builders, such as NaTPP, can be included as further optional ingredients to supply or supplement building function not provided by the buffer, -3- -L the amount of such builder not exceeding 5% of the total composition, according to the patent. Maintenance of the desired (greater than) pH 10 levels is achieved by the buffer/builder components. High pH is said to minimize decomposition of chlorine bleach and undesired interaction between surfactant and bleach. When present, NaTPP is limited to as stated. Foam killer is not disclosed.

In U.K. Patent Application GB 2,116,199A and GB 2,140,450A, both of which are assigned to Colgate-Palmolive, IS liquid ADD compositions are disclosed which have properties desirably characterizing thixotropic, gel-type structure and which include each of the various ingredients necessary )for effective detergency with an automatic dishwasher. The normally gel-like aqueous automatic dishwasher detergent 0composition having thixotropic properties includes the following ingredients, on a weight basis: 5 to 35% alkali metal tripolyphosphate; 2.5 to 20% sodium silicate; 00 0 to 9% alkali metal carbonate; 0.1 to 5% chlorine bleach stable, water dispersible o0" o organic detergent active material; 0 to 5% chlorine bleach stable foam depressant; chlorine bleach compound in an amount to provide about 0.2 to 4% of available chlorine; thixotropic thickener in an amount sufficient to provide the composition with thixotropy index of about to 10; and sodium hydroxide, as necessary, to adjust pH.

ADD compositions so formulated are low-foaming; 3 are readily soluble in the washing medium and most effective at pH values best conducive to improved cleaning performance, -4viz, pH 10.5-13.5. The compositions are normally of gel consistency, i.e. a highly viscous, opaque jelly-like material having Bingham plastic character and thus relatively high yield values. Accordingly, a definite shear force is necessary to initiate or increase flow, such as would obtain within the agitated dispenser cup of an energized automatic dishwasher.

Under such conditions, the composition is quickly fluidized and easily dispersed. When the shear force is discontinued, the fluid composition quickly reverts to a high viscosity, w Bingham plastic state closely approximating its prior consistency U.S. Patent 4,511,487 dated April 16, 1985 describes a low-foaming detergent paste for dishwashers. The patented thixotropic cleaning agent has a viscosity of at least Pa.s at 20 0 C as determined with a rotational viscometer at a spindle speed of 5 revolutions per minute. The composition

S

B is based on a mixture of finely divided hydrated sodium metasilicate, an active chlorine compound and a thickening agent which is a foliated silicate of the hectorite type.

Small amount of nonionic tensides and alkali metal carbonates 2a and/or hydroxides may be used.

0 The formation of organoclays by the interaction of clays (such as bentonite and hectorite) with organic compounds such as quaternary ammonium salts, has also been described Mardis, JAOCS, Vol. 61, No. 2, p. 382 (1984)).

While these previously disclosed liquid ADD formulations are not subject or are subject to a lesser degree to one or more of the above described deficiencies, it has been found that in actual practice, still further improvements in physical stability are required to increase the shelf-life of the product and thereby enhance consumer acceptance.

L_

In the above-mentioned copending application Serial No. 744,754 and its continuation-in-part application Serial S-No u..Poe- NO. No. oacf the physical stability of clay based thixotropic liquid formulations is improved by addition thereto of small amounts, for example, from about 0.02 to 1% by weight, of a polyvalent metal salt of a long chain fatty acid, such as aluminum stearate.

While the combination of clay thickener and fatty acid salt stabilizer has been found to provide satisfactory t long term stability, such as absence of phase separation for periods up to 12 weeks and longer, the addition of clay to these formulations has several drawbacks.

For example, when using clay thickeners the order of addition of the various ingredients and the control of the process conditions during formulation of the compositions is critical to obtain the desired thixotropic properties and low foam characteristics. In addition, the clay thickeners o are expensive materials and can contribute significantly oO to the final product cost to the consumer. In some cases the clay thickeners may actually interfere with overall cleaning performance.

Accordingly, it is an object of the invention to provide stable thixotropic aqueous suspensions which avoid the use of clay thickeners.

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

It is still another object of the invention to provide thixotropic liquid ADD compositions having reduced levels of thixotropic thickener without adversely effecting the generally high viscosities at low shear rates and lower viscosities at high shear rates which are characteristic of the desired thixotropic properties.

More broadly, it is an object of this invention to provide stable aqueous thixotropic non-clay based compositions especially liquid automatic dishwasher detergent pastes or gels, by incorporating in the clay-free aqueous suspension a minor amount of a fatty acid effective to inhibit the settling of the suspended particles and to prevent phase separation.

These and other objects of the invention which will become more readily understood from the following detailed description of the invention and preferred embodiments o thereof are achieved by incorporating in an aqueous liquid detergent composition a small but effective amount of a o*x-t^ non-clay, non-polymeric thixotropic agent which is a long chain fatty acid. More particularly, according to a preferred and specific embodiment of the invention, there is provided a normally gel-like automatic dishwasher detergent composition in which is incorporated from about 0.03 to 0.5% by weight 2Q of the composition of a long chain fatty acid which is effective to inhibit settling of the suspended particles, such as alkali metal builder salts, etc., without requiring any clay, polymeric or other thickeners.

In accordance with this particular aspect, the present invention provides a normally gel-like aqueous automatic dishwasher detergent composition having thixotropic properties which include, on a weight basis: 5 to 35% alk li metal tripolyphosphate; 2.5 to 40% sodium silicate; 0 to 9% alkali metal carbonate; -7- I ~L 1 _ii 0.1 to 5% chlorine bleach stable, water dispersible organic detergent active material; 0 to 5% chlorine bleach stable foam depressant; chlorine bleach compound in an amount to provide about 0.2 to 4% of available chlorine; 0.03 to 0.5% of a long chain fatty acid; 0 to 8% sodium hydroxide; and balance water.

Also related to this specific aspect, the invention provides a method for cleaning dishware in an automatic dishwashing machine with an aqueous wash bath containing an effective amount of the liquid automatic dishwasher detergent (LADD) composition as described above. According to this aspect of the invention, the LADD composition can be readily poured into the dispensing cup of the automatic dishwashing machine and will, within just a few seconds, promptly thicken to its normal gel-like or pasty state to remain securely within the dispensing cup until shear forces are again applied thereto, such as by the water Q spray from the dishwashing machine.

SThe invention will now be described in greater detail by way of specific embodiments thereof and with o the aid of the following drawing in which the FIGURE is a graphic representation of thixotropic index of two different formulations according to the present invention and a clay thickened liquid automatic dishwasher detergent composition as disclosed in GB 2,140,450A.

The LADD products of the prior disclosures in the aforementioned G.B. 2,116,199A, GB 2,140,450A and U.S.

S Serial No. 744,754 and its continuation-in-part exhibit improved rheological properties as evaluated by testing -8- $24 00 0 product viscosity as a function of shear rate. The compositions exhibited higher viscosity at a low shear rate and lower viscosity at a high shear rate, the data indicating efficient fluidization and gellation well within the shear rates extant within the standard dishwasher machine. In practical terms, this means improved pouring and processing characteristics as well as less leaking in the machine dispenser-cup, compared to prior liquid or gel ADD products. For applied shear rates corresponding to 3 to 30 rpm, viscosities (Brookfield) correspondingly ranged from about 10,000 to 30,000 cps to about 3000-7000 cps, as measured at room temperature by means of an LVT Brookfield viscometer after 3 minutes using a No. 4 spindle. A shear rate of 7.4 sec-1 corresponds to a spindle rpm of about 3. Aa approximate ten-fold increase in shear rate produces about a 3- to 9-fold reduction in viscosity. The compositions of the assignee's prior invention thus exhibit threshold fluidizations at lower shear rates and of significantly greater extent in terms of incremental increases in shear rate versus incremental decrease in viscosity. This property of the LADD products of the prior invention is summarized in terms of a thixotropic index (TI) which is the ratio of the apparent viscosity at 3 rpm and at 30 rpm. The prior compositions have a TI of from 2 to 10. The LADD compositions should exhibit substantial and quick return to prior quiescent state consistency when the shear force is discontinued.

While the determination of thixotropic index TI as a ratio of apparent viscosity at 3 and 30 rpm provides a satisfactory measure of product usefulness further research and experience has shown that a more reliable measure of thixotropic index and product usefulness as a liquid ADD -9is provided by determining thixotropy as a measure of the area in the hysterisis loop resulting from plotting, under the conditions described below, shear stress, S, as a function of shear rate, n, when the shear rate is in,reased from 0 to a maximu, value and then returned to 0. The larger the area in the hysterisis loop, the greater is the thixotropic index. In terms of apparent viscosity, it has also been ascertained that so long as the viscosity at room temperature (220±loC) measured in a Brookfield Viscosimeter HATD, using 0 a number 4 spindle at 20 rpm, is less than about 20,000 cps, the composition can be readily shaken so that a thixotropic composition can be easily "fluidized" or "liquefied" to allow the product to be dispensed through a conventional squeeze tube bottle or other convenient dispenser.

The present invention is based upon the surprising Sdiscovery that the same or improved theological properties and physical stability, i.e. resistance to phase separation, settling, etc., as in these prior liquid aqueous ADD compositions can be achieved, at significantly lower cost and without 4, 20 any particular processing requirements, by adding to the composition a small but effective amount of a long chain fatty acid in place of the clay thixotropic thickener and, S where used, also the metal salt of the fatty acid. At the same time, improvements in spotting and filming performance fewer spots and reduced filming) can be achieved.

As an example of the improvement in theological properties over a standard clay based thixotropic liquid ADD, reference is made to the attached drawing which is a plot of shear stress, S, as a function of shear rate, 0 n, for aclay based LADD (3 wt% clay) (curve 1) and for two similar LADD compositions iti which the clay is replaced by 0.06 wt% stearic acid (curve 2) or by 0.08 wt%

I

stearic acid (curve Shear stress, S, is measured in a static experiment using a Haake RV-3 machine provided with a coaxial cup. The sample is placed in the outer cup and the inner cup is rotated by the machine at progressively higher shear rates to a maximum of 113 sec 1 and then the shear rate is progressively lowered to zero. The response is automatically recorded as the shear stress. The experiments were carried out using an MV II sensor system (constant values, A=3.76 Pa, M=0.9 sec- 1 The area between the resulting curved lines for each sample is a measure of thixotropy, with larger areas indicating higher thixotropy.

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 curve of shear stress versus shear rate. At the same time, the physical stability is such that even after six weeks or longer, over temperature ranges extending from near freezing to 400C and more, the compositions containing the fatty acid thickeners do not undergo any visible phase separation, The preferrel long chain fatty acids are the higher aliphatic fatty monocarboxylic acids having from about 8 to about 22 carbon atoms, more preferably from about to 20 carbon atoms, and especially preferably from about 12 to 18 carbon atoms, inclusive of the carbon atom of the carboxyl g-oup of the fatty acid. Polycarboxylic acids can also be used, The aliphatic radical mnqy be 8atuxteor unsaturated and may be itraight or branchw* chain saturated fatty acids are preferre fatty acids may be used, such as those k .al sources, such as tallow fatty acid, coco i, soya fatty acid, etc., or from synthetic sources available from -11industrial manufacturing processes.

Thus, examples of the fatty acids which can be used as thickeners in place of clay o. polymeric thickeners include, for example, decanoic acid, lauric acid, dodecanoic acid, palmitic acid, myristic acid, stearic acid, oleic acid, eicosanoic acid, tallow fatty acid, coco fatty acid, soya fatty acid and mixtures of these acids. In addition, the dimers or trimers of these acids can also be used.

Stearic acid and mixed fatty acids, e.g. cocofatty acid, are preferred.

Within the ranges of carbon chain lengths of the monocarboxylic fatty acids specified herein the viscosity of the product tends to decrease as the number of carbon atoms in the monocarboxylic fatty acid decreases. No systematic trends are observed for the dimers or trimers or polybasic carboxylic acids.

The amount of the fatty acid thickener to achieve the desired values of thixotropy and physical stability will depend on such factors as the nature of the fatty acid, detergent active compound, inorganic salts, especially TPP, other LADD ingredients, as well as the anticipated storage and shipping conditions.

Generally, however, amounts of the fatty acid thixotropic agent in the range of from about 0.03 to preferably from about 0.03 to especially preferably from about 0.03 to 0.08%, provide the long term stability and absence of phase separation upon standing or during transport at both low and elevated temperatures as are required for a commercially acceptable product.

oa -12-

L

r^4~*cn~ 0 0 0 o o o o 0 0 0 O 2 n u °0 a 0 a0 o0 0 oO 0 0 Generally, LADD effectiveness is directly related to available chlorine levels; alkalinity; solubility in washing medium; and foam inhibition. It is preferred herein that the pH of the LADD composition be at least about 9.5, more preferably from about 10.5 to 13.5 and most preferably at least about 11.5. At the relatively lower pH values, the LADD product is too viscous, i.e. solid-lik and thus not readily fluidized under the shear-force levels created within the dispenser cup under normal machine operating conditions. In essence, the composition loses much, if not all, of its thixotropic character. Addition of NaOH is thus often needed to increase the pH to within the above ranges, and to increase flowability properties. The presence of carbonate is also often needed herein, since it acts as a buffer helping to maintain the desired pH level.

Excess carbonate is to be avoided, however, since it may cause the formation of needle-like crystals of carbonate, thereby impairing the stability, thixotropy and/or detergency of the LADD product, as well as impairing the dispensability of the product from, for example, squeeze tube bottles.

Caustic soda (NaOH) serves the further function of neutralizing the phosphoric or phosphonic acid ester foam depressant when present. About 0.5 to 3 wt% of NaOH and about 2 to 9 wt% of sodium carbonate in the LADD composition are typical, although it should be noted that sufficient alkalinity may be provided by the NaTPP and sodium silicate.

The NaTPP may employed in the LADD composition in a range of about 8 to 35 wt%, preferably about 20 to wt%, and should preferably be free of heavy metal which tends to decompose or inactivate the preferred sodium hypochlorit and other chlorine bleach compounds. The NaTPP may be i anhydrous or hydrated, including the stable hexahydrate with a degree of hydration of 6 corresponding to about 18% by weight of water or more. Actually, in view of the stability of the hexahydrate, the presence of some water of hydration is highly effective, serving it is thought to form seeds of the stable hexahydrate which expedites hydration and solubilization of the remaining NaTPP particles.

If only the hexahydrate is used, the detergent product may be too liquid and may have little if any thixotropic S character. Conversely, if only the anhydrous NaTPP is used, the product may, in some cases, be too thick and, therefore, unsuitable. Especially preferred LADD compositions are obtained, for example, when using a 0.5:1 to 2:1 weight ratio of anhydrous to hexahydrated NaTPP, values of about 1:1 being particularly preferred.

So oO. Foam inhibition is important to increase dishwasher o 0 machine efficiency and minimize destabilizing effects which a might occur due to the presence of excess foam within the o o o washer during use. Foam may be sufficiently reduced by suitable selection of the type and/or amount of detergent 'oo active material, the main foam-producing component. The degree of foam is also somehwat dependent on the hardness 9 of the wash water in the machine whereby suitable adjustment of the proportions of NaTPP which has a water softening effect may aid in providing the desired degree of foam o o0 inhibition, However, it is generally preferred to include a chlorine bleach stable foam depressant or inhibitor.

Particularly effective are the alkyl phosphonic acid esters of the formula -14- 0 0c a 0 0 o 0 0 0 0 0 00- 0 0 0, 0 0 0 0 0 00 0 0 f 0 11

HO-P--R

OR

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

OR

available, for example, from Hooker (SAP) and Knapsack (LPKn-158), in which one or both R groups in each type of ester may represent independently a C12-20 alkyl group.

Mixtures of the two types, or any other chlorine bleach stable types, or mixtures of mono- and di-esters of the same type, may be employed. Especially preferred is a mixture of mono- and di-C 1 6 1 8 alkyl acid phosphate esters such as min.ostearyl/distearyl acid phosphates 1.2/1 (Knapsack).

When employed, proportions of 0.01 to 5 wt%, preferably 0.1 to 5 wt%, especially about 0.1 to 0.5 wt%, of foam depressant in the composition is typical, the weight ratio of detergent active component to foam depressant (e) generally ranging from about 10:1 to 1:1 and preferably about 4:1 to 1:1. Other defoamers which may be used include, for example, the known silicones.

Although any chlorine bleach compound may be employed in the compositions of this invention, such as dichloroisocyanurate, dichloro-dimethyl hydantoin, or chlorinated TSP, alkali metal, e.g. potassium, lithium, magnesium and especially sodium, hypochlorite is preferred. The composition should contain sufficient chlorine bleach compound to provide about 0.2 to 4.0% by weight of available chlorine, as determined, for example, by acidification of 100 parts of the composition with excess hydrochloric acid. A solution containing about 0 00 00 B 0 0

I

A, r- _c -1 on O 0 0 0 00 100 oj; C8 a t Q a B O is ,^t E 0.2 to 4.0% by weight of sodium hypochlorite contains or provides roughly the same percentage of available chlorine.

About 0.8 to 1.6% by weight of available chlorine is especially preferred. For example, sodium hypochlorite (NaOC1) solution of from about 11 to about 13% available chlorine in amounts of about 3 to 20%, preferably about 7 to 12%, can be advantageous used.

The sodium silicate, which provides alkalinity and protection of hard surfaces, such as fine china glaze and pattern, is employed in an amount ranging from about to 40 wt%, preferably about 10 to 35 wt%, in the composition.

At the higher levels specified herein for example at levels greater than about 10 wt% the silicate also provides increased antispotting action. The sodium silicate is generally added in the form of an aqueous solution, preferably having an Na20:Si02 ratio of about 1:2.2 to 1:2.8, for example, 1:2.4.

Most of the other components of the composition, especially NaOH, sodium hypochlorite and foam depressant may also be added in the form of an aqueous dispersion or solution.

Detergent active material useful herein must be stable in the presence of chlorine bleach, especially hypochlorite bleach, and those of the organic anionic, amine oxide, phosphine oxide, sulphoxide or betaine water dispersible surfactant types are preferred, the first mentioned anionics being most preferred. They are used in amounts ranging from about 0.1 to 5% preferably about 0.3 to Particularly preferred surfactants herein are the linear or branched alkali metal mono- and/or di-(C8- 1 4 alkyl diphenyl oxide mono and/or disulphates, commercially available for example as DOWFAX (Registered Trademark) 3B-2 and DOWFAX 2A-1.

-16- 0 0 4 0 0 3o 'al

I

r

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*BBS

-m 00 0 o 0 In general, the paraffin sulphonates tend to impair, if not destroy, thixotropy, having been found to unduly increase viscosity causing severe shearing force problems. In addition, the surfactant should be compatible with the other ingredients of the composition. Other suitable surfactants include the primary alkylsulphates, alkylsulphonates, alkylarylsulphonates and sec.-alkylsuphates., Examples include sodium

C

10

-C

18 alkylsulphates such as sodium dodecylsulphate and sodium tallow alcoholsulphate; srdium CI 0

-C

18 alkanesulphonates such as sodium hexadecyl-l-sulphonate and sodium C 12

-C

18 alkylbenzenesulphonates such as sodium dodecylbenzenesulphonates.

The corresponding potassium salts may also be employed.

As other suitable surfactants or detergents, the amine oxide surfactants are typically of the structure

R

2

R

1 NO, in which each R represents a lower alkyl group, for instance, methyl, and R 1 represents a long chain alkyl group having from 8 to 22 carbon atoms, for instance a lauryl, myristyl, palmityl or cetyl group. Instead of an amine oxide, a corresponding surfactant phosphine oxide

R

2 RlPO or sulphoxide RRISO can be employed. Betaine surfactants are typically of the structure R 2

R

1 N R"COO0, in which each R represents a lower alkylene group having from 1 to 5 carbon atoms. Specific examples of these surfactants are lauryl-dimethylamine oxide, myristyldimethylamine oxide, the corresponding phosphine oxides and sulphoxides, and the corresponding betaines, including dodecyldimethylammonium acetate, tetradecyldiethylammonium pentanoate, hexadecyldimethylammonium hexanoate and the like. For biodegradability, the alkyl groups in these surfactants should be linear, and such compounds are preferred.

i' Jr j o 'cC 0t 0^ 0 0 0 o0 o 0 u i,oo 03 0 (O 00 0 0) 0 Surfactants of the foregoing type, all well known in the art, are described, for example, in U.S. Patents 3,985,668 and 4,271,030.

The amount of water contained in these compositions should, of course, be neither so high as to produce unduly low viscosity and fluidity, nor so low as to produce unduly high viscosity and low flowability, thixotropic properties in either case being diminished or destroyed. Such amount is readily determined by routine experimentation in any particular instance, generally ranging from about 25 to wt%, preferably about 55 to 65 wt%. The water should also be preferably deiinized or softened.

Other conventional ingredients may be included in these compositions in small amounts, generally less than about 3 wt%, such as perfume, hydrotropic agents such as the sodium benzene, toluene, xylene and cumene sulphonates, preservatives, dyestuffs and pigments and the like, all of course being stable to chlorine bleach compound and high alkalinity (properties of all the components). Especially preferred for coloring are the chlorinated phthalocyanines and polysulphides of aluminosilicate which provide, respectively, pleasing green and blue tints. TiO 2 may be employed for whitening or neutralizing off-shades.

The liquid ADD compositions of this invention are readily employed in known manner for washing dishes, other kitchen utensils a'nd the like in an automatic dishwasher, provided with a suitable detergent dispenser, 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 automatic dishwasher detergents it will be readily understood by ~~1 0 o OU, C) C)tl o o ooBI 0 o o 0 00 C 0 0 3Q i .1 ~Y i one of ordinary skill in the art that the benefits of thixotropy i and physical stability which are obtained by the addition of the fatty acid may apply equally well to replacement of clay or poln)eric thickeners in other clay or polymeric based thixotropic suspensions, such as the scouring paste formulations described in the aforementioned U.S. Patent 3,985,668, dental pastes, and the like.

The invention may be put into practice in various ways and a number of specific embodiments will be described to illustrate the invention with reference to the accompanying examples All amounts and proportions referred to herein are by weight of the composition unless otherwise indicated.

Example 1 In order to demonstrate the effect of the fatty acid thickener liquid ADD formulations are prepared with o varying amounts of fatty acid thixotropic thickener o o (Runs 1, 2 and 3) as shown in Table 1. For comparison, a similar composition (Run No. 4) corresponding to the Oo g0 composition of Example 1 of GB 2,140,450A is prepared according I oo 1 to the procedure disclosed in said example.

C 00 4 -19- 4I TABLE 1 Component R Water 3 Stearic Acid Clay (Gel White GP) Sodium Silicate (47.5% solution of Na20:Si02 ratio of 1:2.4) 2 Sodium tripolyphosphate (substantially anhydrous, i.e. about 3% moisture) 1 Sodium tripolyphosphate hexahydrate 1 Sodium Carbonate (Soda Ash) Sodium Hypochlorite (13% available chlorine) Surfactant (Dowfax 3B-2, 45% Na mono- and di-decyl diphenyloxide disulfonateaqueous solution) Antifoaming agent (Knapsack LPKn 158, mixture of mono- and di-stearyl

(C

1 6

-C

18 alkyl esters of phosphoric acid, mole ratio about 1:1.3 Caustic Soda Solution NaOH) Color (Graphitol Green) 10 un No.1 2.99 0.03 5.00 2.00 2.00 7.00 7.61 0.80 Run No.2 32.96 0.06 25,00 12.00 12.00 7.00 7.61 0.80 0.16 2.40 0.01 100.00 Run No.3 32.94 0.08 25.00 12.00 12.00 7.00 7.61 0.80 0.16 2.40 0.01 100.00 Run No.4 41.92 3.00 13.73 12.00 12.00 7.00 7.61 0.80 0.16 2.40 0.01 100.00 0,16 2.40 0.01 0.00 0 A sample of each of the formulations of Run Nos.

2 and 3 and the comparative clay based formulation (Run No. 4) is subjected to the shear stress measurement using the Haake RV-3 machine as described above to determine thixotropic index and yield point. The results are shown in the attached figure where curve 1 is based on the sample of Run No. 4, curve 2 is based on the sample of Run No. 2, L un n_ Plab it

I

and curve 3 in based on the sample of Run No. 3. The value of yield point the maximum value of shear stress, S, is shown in Table 2.

Other properties are also shown in Table 2, including the apparent viscosity, n, measured on a 24 hour old sample using a Brookfield HATD viscosimeter, using a No. 4 spindle at 20 rpm (T=22 0 ±1 0 density, capillary drainage rate, stability and centrifugation. Capillary drainage rate (CDR) is a measure of stability with higher values indicative I of higher stability. CDR measurements are made by the following procedure: No. 1 Whatman filter paper having a 6.4 cm diameter circle traced thereon is laid on a flat glass plate, 10 cm x 10 cm. A plastic tube, 6.4 cm long, 3.4 cm diameter, is placed in a standing position, centered S, on the circle. The tube is filled with the sample liquid ADD composition (after standing for one day). The time needed for the solvent to seep out of the tube and reach the traced circle is measured. Time is measured on three sides of the circle and averaged. Faster times mean that o o, 20 the gel is not successfully retaining the solvent (water) 0 0i o o which can then leak into the filter paper. Times greater p,0 than about 7 minutes (all samples) are acceptable. The stability measurement is made by placing the sample 1.

t a glass bottle, left at room temperature, and observing the separation at the end of 4 weeks. The centrifugation test is also a measure of stability. Class centrifuge tubes are filled with equal volumes of each sample and are spun vertically, i.e. in a plane parallel to the ground, in a Sorwall centrifuge, for 25 minutes at 500 rpm. The 3 volume of clear liquid is then measured. The results are i reported as the ratio of the height of clear liquid to total height.of sample multiplied by 100, i.e.

height clear liquid h h liqu x 100. Lower numbers indicate greater total height liquid stability.

Property Run No.1 Viscosity, cps 11,460 Yield Point, dynes/cm 2 Density, g/ml 1.35 CDR (minutes) Stability (4 weeks separation <1.0 Centrifugation <L.D TABLE 2 Run No.2 10,660 372 1.36 8.5 0.0 0.0 Run No.3 11,260 720 1,34 10.0 0.0 0.0 Run No.4 5,100 392 1.37 oc 0 to o a o o 0 0; 0 0 o 0 Q o1 6 0 000* The data in Table 2 clearly shows the susperior phase separation stability of the stearic acid based formulations as compared to the clay based formulation. These results, coupled with the thixotropy characteristics indicated by the graphical representations in the figure further demonstrate the superiority of the invention formulations with respect to dishwasher cup leakage.

Example 2 Each of the formulatios of Runs 1-4 of Example 1 are tested to compare cleaning performance (buildup of spots and films on glasswa'.'e) using a Kenmore dishwasher using tap water temperature at 130 0 F and 120 ppm hardness.

11 -22- The test procedure is described in ASTM D3566-79, except that only four cleaning cycles are used. The filming and spotting are evaluated according to the following scales: Film Rating Scale 1. Best, no apparent film 2. Filming slight, becoming apparent 3. Noticeable film, increasing 4. Continued increase of significant film Filming becoming excessive 0 6. Filming high, excessive buildup 7. Continued increase of excessive film.

Spot Rating Scale A, Best no spots B. Very few spots apparent C. Distinct D. Significant coverage approximately The results are shown in Table 3: 0o oo TABLE 3 J Run No. Performance Rating 20 Spot Film 1 B 1,2 2 B,C 1,2 3 BC 2,3 4 C 2,3 -23t- Example 3 Similar results to those described above are obtained if the stearic acid is replaced by isostearic acid, myristic acid, palmitic acid, lauric acid, Emphol dimer acid, Emphol trimer acid or Emphol 1052 polybasic acid.

In addition to the superior physical stability, thixotropy and cleaning performance the compositions of this invention have the additional significant advantage of not requiring any particular order of addition of the 0 respective ingredients. All of the ingredients can be added in any order or simultaneously to a single pot, mixer, etc., and stirred until a uniform homogeneous mixture is obtained. Mixing can be done at room temperature or o at elevated temperature, It is not necessary to premit any of the ingredients or to use different shear mixing conditions, Si ni| o 1 I -24-

Claims (10)

1. An aqueous gel-like thixotropic automatic dishwasher composition comprising approximately by weight: 5 to 35% alkali metal tripolyphosphate;

2.5 to 40% sodiim silicate; 0 to 9% alkali metal carbonate; 0.1 to 5% chlorine bleach stable, water-dispersible organic detergent active material; 0 to 5% chlorine bleach stable foam depressant; chlorine bleach compound in an amount to provide about 0.2 to 4% of available chlorine, 0.03 to 0.5% of an aliphatic fatty acid having from 8 to 22 carbon atoms, dimers thereof, or trimers thereof; 0 to 8% of sodium hydroxide; balance water. 2. The compositions of claim 1, wherein the aliphatic fatty acid has from 10 to 20 carbon atoms.

3. The composition of claim 2, wherein the fatty acid has from 12 to 18 carbon atoms.

4. The composition of claim 1 wherein the fatty acid is stearic acid.

5. The composition of claim 1 wherein the fatty acid (g) is present in an amount of from 0.03 to 0.2%.

6. The composition of claim 4 wherein the fatty acid (g) is prese;; in an amount of from 0.03 to 0.08%.

7. The composition of claim 1 in which the chlorine bleach compound is sodium hypochlorite.

8. The composition of claim 1 which contains at least 0.1 wt% of the foam depressant

9. The composition of claim 8 in which the foam depressant is an alkyl acid phosphate ester or aon alkyl phosphonic acid ester containing one or two C 12 20 alkyl groups, or a mixture thereof. The composition of claim 1 having a pH of 10.5 to

13.5. 11. A method for cleaning soiled dishware in an automatic dishwashing machine which comprises contacting the soiled dishware in an automatic dishwashing machine in an aqueous washbath having dispersed therein an effective amount of the composition of claim 1. DATED this 2nd day of March 1990 COLGATE-PALMOLIVE COMPANY Patent Attorneys for the Applicant: F.B. RICE CO. 0 0 00 000 0 o o 00 0 0000 0 o 00 0 0 o 03 o o00 00 0 uD ou -26-