CA1270172A - Thixotropic liquid automatic dishwasher detergent composition with improved physical stability - Google Patents

Abstract

THIXOTROPIC LIQUID AUTOMATIC DISHWASHER DETERGENT
COMPOSITION WITH IMPROVED PHYSICAL STABILITY
Abstract of the Disclosure The physical stability of liquid gel-like automatic dishwasher detergent compositions based on montmorillonite, attapulgite, hectorite or other inorganic colloid-forming clay or other thixotropic thickener is greatly improved by incorporating in the composition small amounts, such as 0.1 or 0.2 weight percent, of aluminum or zinc stearate or other polyvalent metal salt of long chain fatty acid.
The aqueous compositions containing inorganic builder salts and other functional inorganic salts, chlorine bleach, bleach-stable detergent, thixotropic thickener and polyvalent metal salt of a fatty acid as a physical stabilizer remain stable against phase separation for periods in excess of six weeks under a wide range of temperatures. The thixotropic properties can be retained or improved using smaller levels of the clay thixotropic thickener than in the absence of the physical stabilizer.

Description

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THIXOTROPIC LIQUI~ AUTOMATIC DISHWASHER DETERGENT
COMPOSITION WITH IMPROVED PHYSICAL STAB~LITY

The present invention relates to automatic dishwashing detergent compositions having thixotropic properties, improved chemical and physical stability, 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, moreover, generally cannot be used in automatic dishwashers due to high foam levels, unacceptably low viscosi~ies and exceedingly high alkalinity.
Recent research and development activity has focussed on ~he gel or "thixotropic" form of such compositions, e.g.
scouring cleansers and automatic-dishwasher products characterize as thixotropic pastes. Dishwasher products so provided sre primarily objectionable in that they are insufficien~ly viscous to remain "anchored" in the dispenser cup of the dishwasher, and moreover yield spot~y residues OD dishware, glassware, ch:ina and the like. Ideally, thixotropic cleansing compositions should be highly viscous in 8 quiescent state, Bingham plastic in nature, and have relatively high yield values. When subjected to shear s~resses, however, such ~ ~;27~'7~

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 isgenerally recommended that the automatic dishwashing detergent, hereinafter also designated ADD, contain (1) sodium tripolyphosphate (NaTPP) to soEten or tie up hard-water minerals and to emulsify and/or peptize soil; (2) sodium silicate to supply the alkalinity necessary for effective detergency and to provide protec~ion for fine china gla~e and pattern; (33 sodium carbona~e, generally considered to be optional, to enhance alkalinity; (4) a chlorine-releasing agent to aid in the elimination of soil specks which lead to water spotting; and (5) 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 approximatin~ ~o the afore-described compositions are mostly liquids or powders. Combi~ing such ingredients in a gel form e~fective for home-machine use has proved difficult. Generally, such compositions omit hypochlorite bleach, since it tends to react with other chemically active ingredients, particularly surfactan~, thereby degrading the suspending or thixotropic agent and 11 ~?~7~
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impairing its effectiveness. Thus, U.S. Patent 4,115,308 discloses thixotropic automatic dishwasher pastes eontaining a suspending agent, e.g. CMC, synthetic clays or the like;
inorganic salts including silicates, phosphates and poly-phosphates; a small amount of surfactant and a suds depressor.
Bleach is not disclosed. U.S. Patent No. 4, 147,650 is s~mewhat similar, optionally including Cl-(hypochlorite) bleach but no organic surfactant or foam depressant. The product is described, moreover, as a de~ergent slurry with no apparent thixotropic properties.
U.S. Patent NoO 3,985,668 describes abrasive scouring cleaners of gel-like consistency containing (1) suspending agent, preferably the Smectite and attapulgite types of clay; (2) abrasive, e.g. silica sand or perlite; and (3) filler comprising light density powdered polymers, expanded perlite and the like, which has a b,o~u`yancy and thus stabiliziDg effect on the composition in addition to serving as a bul~ing agent, thereby replacing water otherwise available for undesired supernatant layer formation due to leaking and phase destabilizat on The foregoing are the essential ingredients. Optional ingredient 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 prov;ded by the buffer, the amoun~ of such builder not exceeding 5% of the total composition, according to the patent. ~aintenanc of the desired (greater than) pH 10 level~ is achieved by the buffer/builder components. Hi~h pH is aid ~o minimize decomposition of chlorine bleach and undesired interaction between surfaetant and bleach. When present, NaTPP is limited ;~2~

to 5%, as stated. Foam killer is not disclosed.
Tn U.K. Patent Application GB 2,116,199A and GB 2,140,450A, both of which are assigned to Colgate-Palmolive, liquid ADD co~positions 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 dishwagher.
The normally gel-like aqueous automatic dishwasher detergent composition having thixotropic properties includes the following ingredients, on a wei~ht basis:
(a) 5 to 3% alkali metal tripolyphosphate;
(b) 2.5 to 20% sodium silicate;
(c) 0 to 9% alkali metal carbonate;
(d) 0.1 to 5% chlorine bleach stable, water dispersible organic detergent active material;
(e) 0 to 5% chlorine bleach stable foam depressant;
(f) chlorine bleach compound in an amount to provide about 0.2 to 4% of available chlorine; and (g) thixotropic thickener in an amount sufficient to provide the c~mposition with thixotropy index of about

2.5 to 1~.
ADD compositions so formulated are low-foaming;
are readily soluble in the was~ing medium and most effective at pH values best conductive ~o improved cleaning performance, viz, pH 10.S-13.5. The compositions are normally o gel ' consistency, i.e. a highly viscous, opaque jelly-like material having Bingham plastic character and thus rela~ively high yi~ld values. Accordingly, a definite shear force i5 necessary to initiate or increase flow, such as would obtain within the agitated dispenser cup of an energized automatic dishwasher.

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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, Bingham plastic state closely approximateing its prior con-sistency.
While these previously disclosed liquid ADD formulation are not subject or subject to a lesser degree to one or more of the above described deficiencies, i~ has been found that in actual practice, still further improvements in physical stability are required to increase the shelf-like of the product and thereby enhance consumer acceptance.
Accordingly, it is an object of ~he invention to provide liquid ADD compositions having thixotropic properties with improved physical stability and rheological properties.
It is also an obiect 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 reates and lower viscosities at high shear rates which are characteristic of the desired thixotropic properties.
These and other objects of the invention which will become more readily understood from the following detailed description of the invention and preferred embodiments thereof are achieved by incorporating in a normally gel-like aqueous automatic dishwasher detergent composition an amount of a polyvalent metal salt of a long chain fatty acid which is effective to inhibit settling of the suspended part~cles, such as thixotropic agent.
Accordingly, in one broad aspect, the present invention provides a normally gel-like aqueous automati~
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dishwasher detergent composition having thixotropic properties which include, on a weight basis:
(a) 5 to 35% alkali metal tripolyphosphate;
~b) 2.5 to 20% sodium silica~e;
(c) 0 to 9% alkali metal carbonate;
(d) 0.1 to 5~/O chlorine bleach stable, water dispersible organic detergent active material;
(e) 0 to 5% chlorine bleach stable foam depressant;
(f) chlorine bleach compound in an amount to provide about 0.2 to 4% of available chlorine;
(g~ thixotropic thickener in an amount suficient to provide the composition with a thixotropy index of about 2.0 to 10;
(h~ 0 to 3% sodium hydroxide;
(i) a polyvalent metal salt of a long chain fatty acid in an amount effective to increase the physical stability of the composition; and (j~ balance water.
In another aspect the invention provides a method for cleaning dishwar~ in an automatic dishwashing machine with an aqueous wash/bath containing an effective amoun~
of the liquid automatic dishwasher deterent (LADD) composition as described above. According to tlis aspect o~ 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 9 promptly thicken to its normal gel-like state to remain securely within the dispensin~ cup until shear forces are again applied the1reto, such 8S by the wster spray from the dishwash;ng machine.

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Generally, ADD effectiveness is directly related to (a) available chlorine levels; (b) alkalinityi (c) solubility in washing medium; and (d) foam inhibition. It is preferred herein that the pH of the ADD 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 relatively lower pH values, the ADD product is too viscous, i.e. solid-like, 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 carbona~e is also often needed herein, since it acts as a buffer helping to lS maintain the desired pH level. Excess cabonate is to be avoided, however, since it may eause the formation of needle-like crystals of carbonate, thereby impairin~ the stability, thixotrophy and/or detergency of the ADD product. Caustic soda (NaOH) serves the further function of neutralizing the phosphoric or phosphonic acid ester foam depressant when present. About 0.5 to 3wt% of NaOH and about ? to 9wt% of sodium carbonate in the composition are present.-About 0.5 to 3wt% of NaOH and about 2 to 9w~% of sodium carbonate in the composition are typical although it should be noted that sufficient alkalinity may be provided by the NaTPP and sodium silicate.
The NaTPP employed in the composition in a range of about 8 to 35 wt%, preferably about 20 to 30wt%9 should preferably be free of heavy metal which tends to decompose or inactivate the preferred sodium hypochlorite and other chlorine bleac:h compounds. The NaTPP may have an average I ~27~

¦ degree of hydration of less than about 1 or more than about 5 e.g. O to 2.7% byweight or at least 16.5% of water, including ¦ the stable hexahydrate wi~h a degree of hydration of 6 correspond ng to about 18% by weight of water or more. Actually, humidificatio to an average of about 0.3 to 1% water is highly effective, serving i~ is thought to form seeds of the stable hexahydrate which expedites hydration and solubilization of the remaining NaTPP particles. On average, the NaTPP contains abou~ 5 to 15% by weight water, corresponding to an average degree of hydration of about 1 to 5. If only the hexahydrate is used, the de~ergent product is liquid and has little if any thixotropic character. If only the anhydrous NaTPP
is used, the product is too thick and therefore unsuitab~e.
Effective compositions are obtained, for example, when using a 0.5:1 to 2:1 weigh~ ratio of anhydrous to hexahydrated NaTPP, values of about 1:1 bein8 particularly preferred.
Foam inhibition is important to increase dishwasher machine efficiency and minimize destabilizing effects which might occur due to the presence of excess foam within the washer during use. Foam may be sufficiently reduced by suitable selection of the ~ype and/or amount of detergent active material, the main foam-producing component. The degree of foam is also somwhat dependent on the hardne~s 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 inhibition However, it is generally preferred ~o include a ehlorine bleach stable foam depressant or inhibitor. Particularly effective are the alkyl phosphonic acid esters of ~he formula _~_ ~ 17Z - ~

HO P R
OR

available for example from BASF--Wyandotte (PCUK-PAE), and especially the alkyl acid phosphate esters of the formula HO - P- - 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_~0 alkyl group. Mix~ures 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-C16_1g alkyl acid phosphate ester~ such as monostearyl/
distearyl acid phosphates 1.2/1 (Knapsack~. When employed, proportions of 0.1 to 5wt~/o~ preferably about 0.1 to 0.5wt%, of foam depressant in the composition is typical, the weight ratio of detergent active component (d) to foam depressant (e) generally ranging from about 10:1 to 1:1 and preferably abou~ 4:1 to 1 1. Other defoamers which may be used include for example the known silicone~.
Although any chlorine bleach compound may be employed in the composi~ions of this invention, such as dichloro-isocyanurat~, dichloro-dimethyl hydantoin, or chlorinated TSP, alkali metal, e.g. po~tassium, lithium, magnesium and `
especially sodium, hypochlori~e is preferred. The composition should contain sufficient chlorine bleach compound to provide about 0.2 to 4.0% by weight of available chlorine~ as _g_ ~7~L7~

determined for example by acidification of 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 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 (NaOCl solution of ll of 13% available chlorine in amounts of about 3 to 20%, preferably about: 7 to 12%, can be advantageously l 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 2.5 to 20 wt%, preferably about 5 to 15wt%, in the eomposition.
The sodium silicate is generally added in the form of an aqueous solution, preferably having an Na2O:SiO2 ratio of about 1:2.2 to 1:2.8. At this point, it should be mentioned that most of the other components of ~hi~ composition, especially NaOH, sodium hypochlorite, foam depressant and thixotropic thickener, are also often added in the form of a preliminary prepared aqueous dispersion or solution.
Detergent active material useful herein must be stable in ~he presence of chlorine bleach, especially hypo-chlorite bleach, and preferably comprise those of the organic anionic, amine oxide, phosphine oxide, sulphoxide or betaine water dispersible surfactant types, the firæt mentioned anionics being most preferred. They are used in amou ~
ranging from about 0.1 to 5~/O preferably about 0.5 to 2.0%, more preferab]y about 0.3 to 0.8%. Particularly preferred surfactant~ hereint are the linear or branched alkali metal mono- and~or cli-~Cg_l4) alkyl diphenyl oxide mono and/or ~70~ ~

¦ disulphates, commercially available for example as DOWFAX
¦ (Registered Trade Mark) 3B-2 and DOWFAX 2A-l. In general, the paraffin sulphonates tend to impair, if not destroy l 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 alkylsulphonates, alkylr,ulphonates, alkylarylsulphonate~
and sec.- alkylsulphates. Examples are sodium Clo-C1~ alkylsulph ~es such as sodium dodecylsulpha~e and sodium ~allow alcoholsulphate;
sodium C1o-Clg alkanesulphonates such as sodiumhexadecyl-l~ulphon ~te and sodium C12-Clg alkylbenzenesulphonates such as sodcium dodecylbenzenesulphonates, The corresponding potassium salts may also be employed.
As other suitable surfactants or detergents, the amine oxide surfactants are typically of the structure R2RlNO, in which each R represent a lower alkyl group, for instance methyl, and Rl represents a long chain alkyl gr~up having from 8 to 22 carbon atoms, for instance a lauryl, myristyl, palmityl or cetyl group. Instead of an amine oxide, a corresponding surfactant pho~phine oxide R2RlPO
or sulphoxide RRlSO can be employed. Betaine surfactants are typically of the s~ructure R2RlN~R"COO- , in which each R represents a lower alkylene group having from 1 to 5 carbon atoms. Specific examples of ~hese surfactants are lauryl-dimethylamine oxide, myristyldimethylamine oxide, the correspondi ~g phosphine oxicles and sulphoxides, and the correspond}ng betaines including dodecyldimethylammonium acetate, tetra-decyldiethylammonium pentanoate, hexadecyldimethylammonium hexanoate and the like. For biodegradability, the alkyl groups in these surfactants should be linear, and such compounds ~ Z ~ ~ 7 are preferred.
Surfactan~s of the foregoin~ type, all well known in the art, are described, for example, in U.S. Patents

3,985,668 and 4,271,030.
Thixotropic thickeners, i.e. thickeners or suspending agents which provide an aque~us medium with thixotropic properties, are known in the art and may be organic or inorganic water soluble, waterdispersible or colloid-furming, and monomeric or polymeric, and should of course be stable in these compositions, e.g. stable to high alkalinity and chlorine bleach compounds, such as sodium hypochlorite. Those especially preferred generally comprise the inorganic, colloid-forming clays of smec~ite and/or attapulgite types. These materials were generally used in amounts of about 1.5 ~o lO,preferably 2 to 5 wt%, to confer the desired thixo~ropic properties and Bingham plastic character in the assignee's prior disclosed ADD formulation~ of the aforementioned GB 2,116,199A and GB 2,140,450A. It is one of the advantages of the ADD formulatio s of the pre6ent inven~ion that the desired thixotropic proper~ies and Bingham plastic character can be obtained in the presencç
of the polyvalent metal salt fatty acid stabilizer~ with lesser amounts of the thixotropic ~hickeners. For exampl~e, amounts of the inorganic colloid-forming clays of the smectite and/or attapulgite types in the range of from about 0.1 to 3~/O~ preferably 0.2 to 2.5%, especially 0.5 to 2.2%, are generally suff;cient to achieve the desired thixotropic properties and Bingham plastic character when used in combination with the physic:al stabilizer.
Smect:ite clays include montmorillonite (bentoni~e), hectorite, saponi~e, and the like. Materials of this type 1 ~7~

are available under trade names such as Thixogel (Registered Trade Mark) No. 1 and Gelwhite tRegistered Trade Mark) GP, H, etc from Georgia Kaolin Company (both being montmorillonites).
Attapulgite clays include the materials commercially available under the trade name Attagel ~Registered Trade Mark), i.e.
Attagel 40, Attagel 50 and Attagel 150 from Engelhard Minerals and Chemicals Corporation. Mixtures ofsmectite and attapulgite types in weight ratios of 4:1 to 1:5 are also useful herein.
Thickening or suspending agents of the foregoing types sre well known in the art, being described, for example, in U.S. Patent No. 3,985,668 referred to above. Abrasives or polishing agents should be avoided.
The amount of water contained in these compos;tions 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 byroutine experimentation in any particular instance, generally ranging frcm about 45 to 75 wt%, preferably about 55 to 65 wt%. The water should also be preferably deionized or softened.
So far, the description of the ADD produc~ exc~pt as otherwise noted, comforms to the compositions 8S diselosed in the aforementioned UK Patent Applications GB 2,116~199A
and GB 2,140,450A.
The ADD products of these prior disclosures exhibit improv d rheological properties ~s evaluated by testing product viscosity as a function of shear rate. The compositions exhibited higher viscosi~y at a low shear rate and lower viscosi~y at a high shear rate, the data indicating efficient fluidization and gellation well within the shear rates extant 3~'7~

within the dishwasher machine. In practical terms, this meant improved pouring and processing characteristics as well as less leaking in the machine dispenser-cup, compared to ~rior liquid or gel ADD products. For applied shear rates corresponding to 3 to 30 rpm, viscosities (Brookfield) correspondingly ranged from about 15,000 to 30,000 cps to about 3000-5000 cps, as measured ,at room temperature by means of a LVT Brookfield viscometer after 3 minutes using a No. 4 spindle. A shear rate of 7.4 sec~l corresponds to a spindle rpm of about 3. An approximate ten-fold increase in shear rate produces a six- to seven-fold reduction in viscosity. With prior ADD gels, the corresponding reduction in viscosity was only about twn-fold. Moreover, with such compositions, the initial viscosity taken at about 3 rpm was only about 2500-2700 cps. The compositions of the assignee's prior invention thus exhibi~ threshold 1uidizations 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 ADD produc~s of the prior invention is summarized in terms of a thixo~ropic index (TI
which ls the ratio of the apparent viscosity at 3 rpm and at 30 rpm. The prior compositions have a TI of from 2.5 to 10. -The ADD compositions tested exhibited subætantial and quick return to prior quiescent state consistency when the shear force was discontinued.
The present invention is based upon the discovery that the physical stability, i.e. resistance to phase separation settling, etc., of these prior liquid aqueous ADD composition~
can be significan~ly improved, without adversely affecting, and in some cases, advantageously affecting, their rheological properties, by adding to the composition a small but effective amount of ~ polyvalent metal salt of a long chaiD fatty acid.

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As an example oE ~he improvement in rheolo~ic~l propeties it has been found that the viscos,t~i`es at low shear rates, e.g. at a spindle rpm of ab~ut 3, apparent viscos;ties l may often be increased from two- to three-fold with the ¦ incorporation of as little as 0.2% or less of the fatty acid metal salt stabilizer. At the same time, the physical stability may be improved to such an extent that e~en after six weeks or longer, over temperature ranges extending from near freezing to 40C and more, the compositions containing the metal salt stabilizers do not undergo any visible phase separation.
The preferred long chain fatty acids are the higher aliphatic fatty acids having from about 8 to about 22 carbon atoms, more preferably from about 10 to 20 carbon stoms, and especially preferably from abuu~ 12 to 18 carbon atom~, inclusive of the carbon atom of the carboxyl group of the fatty acid. The aliphatic radic.al may be saturated or unsaturated and maybe straight or branched. Mixtures of fatty acids may be used, such as those derived from natural sources>
such as tallow fatty acid, coco fatty acid, soya fatty acid, etc. .
Thus, examples of the fatty acids from which the polyvalent metal salt stabilizers can be formed include, for example, decanoic acid, dodecan~ic acid, palmitic acid, myristic acid, stearic acid, oleic acid, eicosanoic acid, tallow fatty acid, coco f~tty acid, soya fatty acid, mixtures of these acids, etc. Stearic acid, in view of both commercial availability and results, is preferred.

.~ 2 The preferred polyvalent metals are aluminum and zinc, although other polyvalent metals, especially those of Groups IIA, IIIA, IVA, VA, VA, VIIA, IIB, IIIB, IVB, VB and VIII of the Periodic Table of the ElPments can also be used. Specific examples of such other polyvalent metals include Mg, Co, ~i, Zr, V, Nb, Mn, Fe, Co, Ni, Cd, Sn, Sb, Bi, etc. Pre~erably, the metal salts are used in their higher oxidation states.
Many of these metal salts are commercially available.
For example, the aluminum salts are available in the triacid form, e.g. aluminum stearate as aluminum tristearate, Al(C17H3sCOO)3. The monoacid salts, e.g. aluminum monostearate, Al(OH32(C17H3sCOO) and diacid salts, e.g. aluminum distearate, Al(OH)(C17H35C)2, and mixtur~s of two or three of the mono-, di- and tri-acid salts can be used for those metals, e.g. Al, with valences of +3, and mixtures of the mono- and di-acid salts can be used for those metals, e.g. Zn, with valences of ~2. It is most preferred that the diacids of the +2 vslent metals and the triacids of ~he ~3 valent metals, and the tetraacids of the +4 valent metals, be used in predominan amounts. For example, at least 30%, preferably at leas~
50%, especislly preferably from 80 to 100% of the total metal salt be in the highest possible oxidation state, i.e.
each of the poss;ble valence sites is occupied by a fatty acid residue.
The metal salts, as mentioned above, ase generally commer~ally available but can be easi~y produced by, for example, saponification of a fatty acid, e.gO animal fa~, stearic acid, etc., or the corresponding fatty acid ester, . .

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followed by treatment wi-th an hydroxide or oxide of the poly-valent metal, Eor example, in the case of the aluminum salt, with alum, alumina, etc.
Aluminum steara-te, i.e. aluminum tristearate, and zinc stearate, i.e. zinc distearate, are the preferred poly valent fatty acid salt stabilizers.
The amount of the fatty acid salt stabilizers to achieve the desired enhancement of physical stability will depend on such factors as the nature of the Eatty acid sal-t, the nature and amount of the thixotropic agent, detergent active compound, inorganic salts, especially TPP, other ADD
ingredients, as well as the anticipated storage and shipping conditions.
Generally, however, amounts of the polyvalent metal fatty acid salt stabilizing agents in -the range of from about 0.02 to 1%, preEerably from about 0.06 to 0.8%, especially preferably from about 0.08 to 0.4%, 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.
In particular preferred embodiments of the invention the composition comprises from about 0.1 to 0.2% by weight of the physical stabilizer and from about 0.5 to 2% by weight of an inorganic, colloid-forming clay as the thixotropic thickener or, in another embodiment, from about 0.3 -to 0.4% by weight of the physical stabilizer and about 0.25% by weight of an in-organic colloid--forming clay as the thixotropic thickener.
Accord:ing to one preferred method of making these t B d 17 -.~7~72 62301-1380l compositions, one should dissolve or disperse first all the inorganic sal-ts, i.e. carbonate (when employed), silicate and tripolyphosphate, in the aqueous medium. Thickening agent is added last. The foam depressor (when employed) is prelimi-narily provided as an aqueous dispersion, as is the thicken-ing agent. The foam depressant d:ispersion, caustic soda (when employed) and inorganic salts are first mixed at eleva-ted temperatures in aqueous solution (deionized water) and thereafter cooled, using agitation throughout.

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¦ Bleach, surfactant, fatty acid salt, stabilizer and thickener ¦ disp-:rsion at r~om temperature are thereafter added to the ¦ cooled (25-35C) solution. Excl~ding the chlorine bleach l compound, total salt concentration (NaTPP, sodium silicate ¦ and carbonate) is generally about 20 to 50wt%, preferably about 30 to 40wt% in the composition.
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 chlori~e bleach compound and high alkali~i~y (properties of all the componen~s). Especia'.ly preferred for colouring are ~he ch]or;nated phthalocyanines and polysulphides of alunl;nosilicate wh:;c~ provide, respectively, pleasing green and blue tint~. TiO2 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 u~ensils and the like in an automatic dish washer, provided with a suitable detergent dispenser, in an aqueous wash bath containing an effec~ive amount of the composition.
The inven~ion may be put into practice in various ways and a number of specific emobdiment~ will be described to illustrate the invention wi~h reference to the accompanying example~.
All amount~ and proportions referred to herein are by weight of the composition unless otherwise indicated.

Example 1 In order to demonstrate the effect of ~he metal salt stabilizer liquid ADD formula~ions are prepared with varying amounts of ~tabilizer and thixotropic thickener.
Initially ~he following ingredients are mixed in a Guis~i mixer at 50-60C:
%
Deionized waSer 41.10+y-x Caustic soda solu~ion (50% NaOH) l.OO
Sodium carbonate, anhydrous 5.00 Sodium silicate, 47.5%
solution of Na2:si2 ratio of 1:2.4 15.74 Sodium TPP (substantially ~nhydrous-i.e. 0-5%, especially 3%, moisture~
(Thermphos NW) 12.00 Sodium TPP (hexahydrate3 (Thermphos N hexa) 12.00 The mixture is cooled a~ 25-30DC and sgitation maintained throughout, and the followingingredients at room temperature are added there~o: -Sodium hypochlorite solution (11% available chlorine) 9.00 Monostearylphosphate 0.16 DOWFAX 3B-2 ~45% Na monodecyl/didecyl diphenyl oxide disulphonste-a~ueou solution) 0.80 Al tristearate or Zn distreate x Gel Wh;te H 2.00-y .

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The m~nostearyl phosphace foam depressant and Dowfax 3B2 detergent active compound are added to the mixture just before the aluminum tristearate or zinc distearate stabilizer or right before the Gel White H thickener.
Each of the resulting liquid ADD formulations as shown in Table I are measured for density, C~R (Capillary Drainage Rate), apparent viscosity at 3 and 30 rpm, and physical stability (phase separation) on standing and in a shipping test. The results are also shown in Table I.
From the data reported in Table I the following conclusions are reached:
The incorporation of 0.2 % Al stearate in a 1.5%
or in a 1% Gel White H containing formula as well as the incorporation of 0.1% Al stearate or of 0.1% Zinc stearate in a 2% Gel White H containing formula leads ~o a simultaneous increase of the physical stability and o the apparent viscosity (Table I, runs l (control), 2, 3, 6, and 9.
The incorporation of 0.1% Al stearate in a lD/o Gel White H ~ontaining formula, of 0.2% Al stearate in a O.5% Gel White H containing formula, and of 0.3 or 0.4%
Al stearate in a 0.25% Gel White H containing ormula leads to an increase of ~he physical s~ability without any drastic viscosity increase ~Table II, runs 1 (control), 4, 7, 10 and ll).
~5 For ~he combination of 0.1% Al stearate and 0.5/O
Gel White H (Run 8) the apparent viscosi~y values remain . acceptable bu~ no significant improvement in physical stability is obtained.

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~7al~72 Note~ to Table I
(1) No. 1 filter paper (~hatman) having a 6.4 cm circle traced therenn 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 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 ~hree side6 of the circle and averaged. Faster times means that the gel is not successfully retaining the solvent (water3 which can then leak into the filter paper. Times greater than 5 minut~ks are considered good. Times between 4 and 5 minutes are consider~d unstable but acceptable.
(2) Measured with spindle 4 after 3 minutes on 24 hour old~samples.
(3) In height.

(4) In weight.
(5~ At 4C, room tempera~ure (RT=20+2C), 35C and 43C in glass bottle.
~6) Liquid separation measured after 6 weeks and 3000 Km in a private c}r (in weight in a pla}ric bottle).-~ 7 Example 2 Using the same composition and preparation method as in Example 1 except that in place of Gel White H as the thixotropic thickener, 2% of Attagel 50 (an attapulgite clay) or 0.4% of Bentone EW (a specially processed Hectorite clay) was used with (runs 2 and 4) or without (control runs 1 and 3) aluminum tristearate. The apparent ViSCOsitieS
and physical stabilities were measured in the same manner as described for Example 1. The results sreshown in Table II.
From the results shown in Table II it can be seen that small amounts of aluminum stearate are equally effective in increasing ~he physical stability of attapulgite ~lay and hectorite clay based liquid thixotropic automatic dishwasher detergent compositions.

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. Example 3 This example shows that inorganic aluminum and zinc salts, including A1203, ZnS04 and A12(S04)3 and the monovalent metal fatty acid salts do no~ provide improved physical stability to the liquid thixotropic ADD composition~.
Using the same formulation as in Run 6 of Example l 0.1%
of each of A1203, ZnS04, Al2(S04)3 and sodium steara~e was used in place of 0.1% aluminum stearate. The reBults of the measurements of apparent viscosity and physical stability are shown in Table III.

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prepared followln~ th~ ~m~ ~gner~l procodure~ ~ In ~x~mple 1:
~LE~ ~'' Sodium ~llic~t~ (47.5% ~ol'n ~2~S1~2~1~2 . 4~ 7 . ~8 Mono~e~Rryl phoilphs~ O.16 Dowf~x ~-2 0 . 37 1~3rmphos N~ 12 . ~
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p~ 12.g ~o 12.9 a~ or ~un~s o~ por~ , colo~, ~tc. csln ~l~o b~ 2t ~o for~lult:ion .

~30_

Claims (22)

What is claimed is:

1. An aqueous thixotropic automatic dishwasher composition comprising approximately by weight:
(a) 5 to 35% alkali metal tripolyphosphate;
(b) 2.5 to 20% sodium silicate;
(c) 0 to 9% alkali metal carbonate;
(d) 0.1 to 5% chlorine bleach stable, water-dispersible organic detergent active material;
(e) 0 to 5% chlorine bleach stable foam depressant;
(f) chlorine bleach compound in an amount to provide about 0.2 to 4% of available chlorine;
(g) thixotropic thickener in an amount sufficient to provide the composition with a thixotropy index of about 2 to 10;
(h) 0 to 3% of sodium hydroxide;
(i) a polyvalent metal salt of a long chain fatty acid as a physical stabilizer in an amount effective to increase the physical stability of the composition; and (j) balance water.

2. The composition of claim 1 wherein the physical stabilizer (i) is a polyvalent metal salt of an aliphatic fatty acid having from about 8 to 22 carbon atoms.

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

4. The composition of claim 2 wherein the polyvalent metal is a metal selected from any one of Groups IIA, IIIA, IVA, VA, VIIA, IIB, IIIB, IVB, VB and VIII of the Periodic Table of the Elements.

5. The composition of claim 4 wherein the polyvalent metal is selected from the group consisting of Mg, Ca, Ti, Zr, V, Nb, Mn, Fe, Co, Ni, Cd, Sn, Sb, Bi, Al and Zn.

6. The composition of claim 2 wherein the physical stabilizer (i) is the aluminum salt or zinc salt of said fatty acid.

7. The composition of claim 1 wherein the physical stabilizer (i) is aluminum tristearate.

8. The composition of claim 1 wherein the physical stabilizer (i) is zinc distearate.

9. The composition of claim 1 wherein the physical stabilizer (i) is present in an amount of from about 0.02 to 1% by weight.

10. The composition of claim 1 wherein the physical stabilizer (i) is present in an amount of from about 0.06 to 0.8% by weight.

11. The composition of claim 1 wherein the physical stabilizer (i) is present in an amount of from about 0.08 to 0.4% by weight.

12. The composition of claim 1 wherein the thixotropic thickener (g) is an inorganic, colloid-forming clay.

13. The composition of claim 12 wherein the clay is a montmorillonite clay, an attapulgite clay, a hectorite clay or a smectite clay.

14. The composition of claim 12 wherein the amount of the clay thickener is in the range of from about 0.1 to 3%
by weight.

15. The composition of claim 12 wherein the amount of the clay thickener is in the range of from about 0.5 to 2.2%
by weight.

16. The composition of claim 6 which contains from about 0.1 to 0.2% by weight of the physical stabilizer (i) and from about 0.5 to 2% by weight of an inorganic, colloid-forming clay as the thixotropic thickener (g).

17. The composition of claim 6 which contains from about 0.3 to 0.4% by weight of the physical stabilizer (i) and about 0.25% by weight of an inorganic colloid-forming clay as the thixotropic thickener (g).

18. The composition of claim 1 in which the chlorine bleach compound (f) is sodium hypochlorite.

19. The composition of claim 1 which contains at least about 0.1wt% of the foam depressant (e).

20. The composition of claim 19 in which the foam de-pressant is an alkyl acid phosphate ester or an alkyl phos-phonic acid ester containing one or two C12-20 alkyl groups, or a mixture thereof.

21. The composition of claim 1 having a pH of 10.5 to about 13.5.

22. 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.