CA1325367C - Detergent for automatic dishwasher - Google Patents

Abstract

ABSTRACT

A thixotropic aqueous detergent for improved performance in household automatic dishwashers comprises a liquid phase which is water containing dissolved alkali metal tripolyphosphate and alkali metal silicate and dispersed non-swelling clay thickener and a solid phase which is mainly sodium tripolyphosphate. It contains a limited proportion of a potassium compound, to give a K:Na weight ratio in the range of about 0.4 to 0.5. A process for making such slurries is also disclosed.

Description

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la~J ~ ~ 62301-1325 ~ -One aspect of thiæ invention relates to an aqueous thixotropic automatic dishwasher detergent comprising a liquid pha~e which is water containing a detergent builder effective amount of dissolved tripolyphosphate, silicate and alkali metal ions and a thixotropically effective amount of a dispersed non-swelling clay thickener (preferably attapulgus clay~ and a solid phase which is mainly sodium tripolyphosphate. The composition preferably also contains a chlorine bleach (advantageously dissolved sodium hypochlorite) and a bleach-resistant anionic surfactant. It also preferably contains an alkali metal carbonate. Canadian Patent Applicatlon Serial No. -432,5g2 filed July 15, 1983 discloses certaln composltions of this type.
It has now been found that greatly improved results are obtalned by including a limlted proportlon of a water-soluble potassium compound, e.g., a potasslum salt (or KOH), in tha composltlon, to provide a K:Na weight ratio which ls in the range of about 0.04 to 0.5, preferably about 0.07 to 0.4 such as about 0.08 or about 0.15. The resultlng product is much -~
more stable in that it has less tendency to thicken undesirably or separate on aging at, say, 100F. Also, substitution of a ~ -portion of the sodium salt by the same weight of the correspondlng potassium salt results ln a considerable reduction ln viscosity (e.g. as measured with a Brookfield HATD
vi~cometer, at 25C at 20 rpm using spindle #4), greater stability against separation on aginq (e.g., at room temperature), and inhibitlon of growth.
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132~3~7 2301-1325 of relatively large crystals on storage. The reduction in viscosity makes for easier handling in the production plant, easier dispensing in use, and makes it easier for the consumer to destroy the thixotropic structure of the product (by shaking the container in which it is packaged) so that it can be poured readily into the detergent cup(s) of a household automatic washing machine.
In the formulation of the product the proportions and ingredients set forth in the above-mentioned Canadian Applica- -tion Serial No. 432,542 may be employed. In that application, one set of ranges of proportions is, approximately, by weight:
(a) 8 to 35~ alkali metal tripolyphosphate, (b) 2.5 to 20% sodium silicate, (c) O 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 abo-~t 0.2 to 4~ of available chlorine, and (g) thixotropic thickener in an amount sufficient to provide the composition with thixotropy index of about 2.5 to 10. ','' .. ~"

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13253~7 ~1 Preferably, in the compositions disclosed herein, the proportion of sodium tripolypho8phate is above 15% (more preferably in the range of about 20 to 25 or 30%), the proportion of ~odium silicate is at least about 4Z t9uch a8 in the range of a~out 5 to 10 or 15~, the proportlons of alkali metal carbonate is about 2 to 6 or 7%, the proportion of chlorine bleach i8 such as to provide above 0.5% available chlorine (e.g. about ~ to 2I available Cl), the proportion of detergent actlve materlal is in the range of 0.1 to 0.5%. Calculated as SiO2, a preferred rauge of pro-portions of sodium sillcate representg about 3.5 to 7 SiO2 in the composi~ion. , The proportion of water ln the compositions (measured by "Cenco*moigture analyzer" (ln which the gample iB heated, by an infrared lamp, until it co~es to constant weight) i~ preferably in the range of about 40-50% more preferably about 43-48% such as about 44 or 46Z.
The compositions di~closed herein usually have p~s well above 11 or 12. In one preferred type of formulation, the composition when diluted ~ith water to 0.75% concentration has a pH in th~ range of about 10.7 to 11.3.
The composit$on di0clo~ed herein are preferably for~ulated to bave ~iscosities (mea~ured ~lth a BrookfieIa*~ATD
viscometer at 25C at 20 rpm usiQg ~plndle J4) of le~s than about .
8000 cent$polgeg a~d more preferabl~ in the range of about 2,000 or 3,090 to 7,000 centipoiges ~uch 88 about 4a000 to 6,000 centi-po~se~. The viscosity, and other propertie8, ~ay be T.M.

~ 132S367 ;',measured several day~ (e.g. ~ a wee~) after the co~poR$tion i~
jprepared; it i8 good practice to shake the ~ample before measuring '¦ lts viscosity and to let the viscometer run for so~e 90 seconds ¦¦before taking the readlng.
The compocition~ dinclo~ed herein have yleld values well above 200 dyneg per c~2 and are preferably formulated to bave Yield value8 of le8s than about llO0 dyne~/cm2 and more than about 300 tynes/c~2, more preferably leg~ thgn about 900 dynes/c~2 such as about 400 to 600 dyne~/cm2. The yielt value i8 an in-dicat~on of the ~hear rate at ~hlch the tbisotropic ~tructure breaks do~n. It i3 measured with a Haa~e*BV 12 or ~V 100 ro-tational vigcometer ugin8 gpi~dle MVI~ at 25C vith a ~hear rate rising linearly ln 5 minutes (after a 5 ~inute rest period) from zero to 2a sec. l. In the ~aake vi~co~eter, a thin layer of the ~aterial 18 sbeared bet~een a rotating c~linder and the closel~ adJacent c~lindrical vall of e~e surrounding contalner.
Pig, 1-3 are graphs obtained on such esting of the product~ of the three ~ample~ indicated thereon, with the peaks Y sh~wing the yleld vslues.
A~other factor ~easured with t~e aforesaid Haa~e viscometer i8 the de8ree to whlch the co~position recovers its thi~otropic structure. In one ~ea~uri~g tech~ique after t~e 5 ~inute period of increaaing shear rate ~entioned above, the rotation is decelerated to zero over 5 ~inute~ then after a 30 secona rest period the rotation 19 again acc~leratea to rai~e the shear rate linearly in 5 ~inutes fro~ zero to 20 ~ec. 1.
T~is give~ a second ~ield value, i.e. pea~ ~r ln Plg. 1. /

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1 3 2 ~ 3 6 7 62301-1325 Preferably thls second Irecovered) yleld value ls at least 200 dynes/cm2, such as 50%, 75% or more of the lnitlally measured yleld value.
Flg. 4 is a photomlcrograph (taken on the scale ln-dlcated thereon) of the composltlon of Example 4.
The followlng Examples are glven to lllustrate thls lnventlon further. ;
In these Examples, Atta~el #50 ls powdered attapul-glte clay (from Engelhard Mlnerals & Chemlcals, whose trade literature lndlcate~ that, as produced, lt contalns about 12 wt.% free molsture, as meagured by heatlng at 220F, and has a B.E.T. surface area of about 210 m2/g calculated on a moisture-free baslsJ~ Graphtol Green 18 a colorlng agent~ LPKN 158 ls an antlfoam agent from Amerlcan Hoechst (Knapsack ) comprislng a 2:1 mlxture of mono and dl- (C16-C18) alkyl esters of phos-phorlc acld, the codlum slllcate has an Na20:S102 ratlo of 1:2.4~ Dowfax 3B2 is a 45% aqueous solutlon of Na monodecyl/-dldecyl dlphenyloxlde dlsulfonates, a bleach-reslstant anlonlc surfactant~ STPP ls sodlum trlpolyphosphate. Unless otherwlse lndlcated, the STPP ls added ln the form of the flnely powdered commerclal anhydrous materlal whose water content ls about 0.5%, ln such materlal typlcally about 4.5 - 6.5% of the msterlal ls present as the pyrophosphate. The water used ls delonlzed water unless otherwlse lndlcated.

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132~367 . ..

E%AMPL~ 1 The folloving ingredients are added to 8 ~e~el in the order gi~en belsw vhile ~ixing ~ith a conve~tional propeller-type laboratory st$rrer. The te~perature~ and ~ising tl~es at various stage~ are al80 indicated belo~:
~ass(g) temperature(F) lQX Graphtol green (color) 5 130P water 1746 ~olten LPR~ 158 (antifoa~) 8 .
Dovfas 3B2 (surfactant) 40 126 (2 ~i~) ~:1 misture of Attagel t50 and TiO2 white pig~ent 180 122 tl ~in) 120 (3 ~in~
80ta a~h 275 134 (1 ~i~) :
132 (3 ~in) ~inel~ povdered STPP herahydrate 750 127 (1 ~in) :-125 (3 ~in) 124 (5 Din) ~:
47.5~ aqueouo Bolutlon of ~otiu~ 421 silicatQ pre~i~ed ~ith 50S agueou~ ~olution o~ ~0~ 150 118 (3 ~ln) 13S aqueou~ ~olutio~ of ~aOCl 500 108 (3 uin) ~inel~ povaeret STPP he~ahydrat~ 750 108 (1 ~i~) ~oe~l 5000S 107 ~5 ~n) 132~367 ~

¦ The viscoslty of the ~ixture, measured as indicated I sbove, i~ about 5000 centipoi8e8 after aglng for 3 wee~s at 1 100F and i8 about 4800 centipoi8es after 3 months agin~ at 10~~.

In this E~ample, the STPP hexahydrate bc~ the fol-lowi~g sppros$mate slze distrlbution:

U.S-.S. Sle~e %
o~ ~10 OD ~40 0 on ~100 25.4 o~ t200 31.5 o~ ~325 16.5 through ~325 25.9 ~AMPL~ 2 The follo~lng for~ulatlono are prepsred and ~heir properties are measured as i~dicated below:
The ingredients are ~lxed in the follo~i~g order:
water, color, cla~, one h~lf of the phosphate, defoa~er, hypo-chlorito, ~odiu~ carbo~ste, pota~s~u~ cærbon-t~, NaOH, eillcate, eocout balf of phospbate, surfacta~t.

1 3 2 ~ 3 6 7 62301-1325 Ingredlents Pro~ortlons a b c d Clay tattagel 50) 3.285 3.285 3.285 3.285 3.285 STPP 23.0 23.0 17.~1 16.5 23.0 Potasslum tripo-lyphosphate - - - 6.5 Potasslum Pyro-phosphate - - 5.99 -Sodlum Carbonate 5.0 - 5.0 5.0 2.5 Potasslum ~arbonate - 5.0 - - 2.5 Sodlum Hypochlorlte (12%) 9.375 9.375 9.375 9.375 9.375 Sodlum Hydroxide (50~) 2.05 2.05 2.05 2.05 2.05 Sodlum Slllcate (47.5%) 10.53 10.53 10.53 10.53 10.53 Surfactant ~Dow-fax 3B-2) 0.80 0.80 0.80 0.80 0.80 Defoamer (Kna~-sack Lp Kn )0.16 0.16 0.16 0.16 0.16 Color 0.381 0.381 0.381 0.381 0.381 Water Balance ProPertles caplllary draln-age tlme (mln.) 8.2 12.1 10.9 ll.g 11.2 Vlscoslty ~cps) on 100F aglng 1 week 9080 3100 2900 5120 5400 2 weeks 9200 3480 2320 6340 5240 3 weeks 9300 3600 3040 6700 6560 The caplllary dralnage tlme ls a test ln whlch a 6.8 cm. diameter clrcle ls drawn on a 15 cm dlameter sheet of Whatman slze 41 fllter paper, a plastlc annulus ~3.5 cm lnslde dlameter, 4.2 cm outslde dlameter, 6.0 cm hlgh) 18 placed ver-tlcally, concen~rlc wlth the clrcle, on the fllter paper, and the annulus is fllled wlth the composltlon to be tested.
Llquld from the composltlon 13 thereby absorbed lnto the filter paper and spreads slowly to the drawn clrcle. The tlme whlch elapses untll the llquld contacts the clrcle ls measured at three predetermlned locatlons and an average value ls calcu-lated. Thls predlctlve test lndlcates relatlve stabllltles of these systems. Thus composltlon (b) has a lower vlscoslty and hlgher stablllty than composltlon (a) above.

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.1 I E~AMPL~ 3 ¦ T~e following formulatlon~ are prepared b~ m$~ing . the ingredient~ in the order intic~ted. The co~po~itlons are then centrifuged at 275 G u~tll there i8 no further lncresse ln the volu~e of the clear ~eparated liquld (continuous) pbase and the re~ulting llquld i8 a~alyzed:
a b c d deionized vater 27.106 ~ ~ -color 0.016 ~otiu~ carbonate 6 4 2 0 potas~iu~ carbonste 0 2 4 6 STPP 21.106 deionlzed ~ater 14.184 ~ttagel ~50 4.00 T12 0.444 __ _ ~ -~
: 50% 301utlon of NaO~ 2.5 4~.5X 801utio3 0~
sodiu~ ~ilicate 13.684 ~ >

sntifosm 0.16 13X ~olutlon of NaOCl 10.0 451 ~olution of ur-factant 0.8 ~ -~- >

` 100.00 ':

T~u~ the co~po itiong are ldentlcal escept for their ~:~a ratlo~

1 3 2 ~ ~ 6 7 623ol-l325 Pro~ertles of Product vlscosity after 1 day at room temperature 8320 5520 4200 2120 after 3 weeks at room temperature 8550 6200 4500 2420 after aglng at 100F for 7 weeks 9400 8000 5600 3400 Speclflc gravlty 1.37 1.37 1.40 1.39 Propertles of llquld Obtained bv Centrlfuaina vi~co~lty at 25C
relative to water at 1 cps. 4.4 4.4 4.8 6.3 % soluble silicate (calculated at mol ratio Na2O:~SiO2 of 1:2.4) 7.5 7.3 7.3 7.1 ~;
~ carbonate (calculated as Na2CO3 8.8 8.5 7.4 6.6 % phosphete ~ -(calculated as Na5P3Olo) 1.7 2.5 3.7 6.1 speciflc gravity 1.257 1.262 1.276 1.30 The viscositles of the product for this Example are measured with a Brookfield RVT viscometer splndle No. 5 at 80F
(26.7C.).
Examples 4-6 below illustrate a new and useful method -of another lnventor separately clalmed ln an appllcation filed on even date herewith for maklng the products descrlbed above (contalnlng llmlted amounts of potasslum). It can also be used for maklng f :

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1 3 2 ~ 3 6 7 2301-1325 other products of the type shown in the previously mentioned Canadian Application Serial No. 432,542 (e.g. in which the potassium compound is nct present) as well as other detergent slurries comprising fine particles of water-soluble inorganic builder salts dispersed in water containing dissolved builder salt, clay or other colloidal thickening agent, and surfactant.
In these Examples (in which the particles of builder salt in the product are largely STPP hexahydrate plus hydrated sodium carbonate) there is formed a highly viscous (e.g. 20,000-60,000 ~-cps viscosity) mixture of a limited amount of water, a highly alkaline saturated solution of builder salts and, as the major constituent, undissolved particles of water-soluble builder salt.
This viscous mixture is subjected to grinding of the undissolved particles with a high speed disperser after which solid particles of the clay thickener are added and the clay is mechanically deagglomerated; thereafter the balance of the .
ingredients of the formula (e.g., other liquids or materials which readily dissolve or disperse in the liquid phase of high electrolyte content) may be mixed in. The mixture may then be subjected to additional high shear mechanical action to further deagglomerate the clay. It is found that with this method pre-dispersion of the clay in aqueous medium is not needed. The solid particles of clay readily disperse even though the medium is highly alkaline. The grinding of the undissolved builder salt particles takes place much mcre efficiently and rapidly in the substantial absence of the clay.

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In the method lllustrated ln Examples 4-6 the builder salt whlch ls to constitute the ma~or portlon of the undlssol-ved partlcles ls preferably added to an aqueous solutlon whlch already contalns such a hlgh concentratlon of dlssolved other bullder salt that thls additlon cause~ bullder ~alt to be thrown out of solutlon (e.g. by common lon effect) and thus to recrystalll~e as tlny crystals.
Another slgnlflcant feature of the mlxlng method lllustrated ln Examples 4-6 ls the fact that lt enablei repeat-ed batches of reproduclble propertles to be made uslng theentire "heel" of the prevlously formè~ batch a~ an lngredlent .,:. . . -. ~
of each ~uccesslve batch.
As lndlcated earller, the use of the proces~ lllu-~trated ln Examples 4-6 18 not llmlted to the maklng of compo-sltlons contalnlng potasslum salts. Whlle lt has thus far found lts greatest utlllty ln maklng formulatlons ln whlch the clay ls attapulglte, lt may al80 be employed for composltlons ln whlch all, or part, of the clay ls of the swelllng type, e.g., a smectlte type of clay such a~ bentonlte (e.g., Gelwhlte GP ) or hectorlte.

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In 32.0 parts of delonized water mlxed wlth a small amount of a plgment (l.e., 0.028 parts of Graphtol green, an . ~, .
aqueous paste contalnlng 28% plgment) there are completely ^ -: ~
dlssolved 2.0 parts K2C03 (whose water solubillty ls over 100 parts per 100 parts of water even at 0C and 5.0 parts granular ` ;`
sodlum carbonate (whose water solublllty ls about 45 parts per 100 at 35C). The solutlon has a temperature of about 90F.

Then 23,116 parts of powdered STPP contalnlng about 0.5% water :~ ' Trade-mark 13 `:

1 3 2 ~ 3 6 7 62301-1325 of hydratlon are added whlle contlnuously sub~ectlng the mlx-ture to the action of a hlgh speed disperser. The amount of STPP ls much more than that whlch ls soluble in the amount of water present; its solublllty ln water ls about 20g per 100 ml at 25C. In this example, the STPP ls a product of Olln Corp.
havlng a phase I cont~nt of about 50%, a sodlum sulfate content of about 2~, and a very flne partlcle slze, it ls a blend of powdered anhydrous STPP made by the known "wet process" and powdered STPP hexahydrate. On addlng the STPP to the solutlon lt hydrates rapldly, formlng hard crystalllne lumps comprlslng STPP hexahydrate. (It wlll be noted that 23 parts of STPP has the capaclty, ln forming the hexahydrate, to take up about 7 parts of water). The ml~ture ls at flrst a thln slurry of ~
undlssolved STPP ln a llquid whlch ls a supersaturated 501U- ~ .
tlon. The temperature rlses owlng to the hydratlon reactlon, reachlng a peak of about 140F. In about 3 to 4 mlnutes the mlxture becomes much more vlscous; lts vlscosity rlses to above 20,000 cps (such as about 40,000-50,000 cps as measured at the slurry temperature e.g. wlth a Brookfleld RVT, splndle #6 at 10 RPM). It 18 belleved that during the process, sodlum carbonate crystalllzes (ln the form of very fine crystals) out of the solutlon phase owlng to the common lon effect (of the sodlum of the STPP). When the mlxture has become vlscous the hlgh speed dlsperser acts to grlnd the partlcles (e.g. of hydrated TPP) to a flne partlcle slze, the grlndlng actlon ls lndlcated, for one thlng, by the lncreased power consumptlon of the dlsperser and an addltlonal rlse ln temperature (e.g., to 150F, whlch ~auses lncreased dlssolutlon of bullder salts; these wlll, ln turn, recrystalllze ln flne form on coollng). Thls grlndlng ls con-tlnued for about 5 minutes after the lnltlal thlckenlng of the :. .

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1~2~3~7 62301-1~25 slurry; durlng grlndlng the vlslble lumps of materlal dlsappear and the partlcle ~lze of the undlssolved partlcles ls reduced so that, lt ls believed, substantlally all the partlcles have dlameters below 40 mlcrons. Then a further 9.367 parts of water are added, lowerlng the vlscoslty to less than 10,000 cps (e.g. ln the nelghborhood of 5000 cps, measured as lndlcated above), after whlch 3.3. parts of Attagel #50 and 0.732 parts of whlte T102 (anatase) plgment are added to the hlghly alka-llne mlxture (whose pH ls well over 9, e.g. 10.5) whlle the mlxture 15 contlnuously sub~ected to the actlon o~ the hlgh speed dlsper~er, whlch dlsperses (deagglomerates) the clay to a large extent, so that the thlck mlxture becomes homoyeneous and smooth in appearance. Then there are added 2.70 part~ of 50%

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aqueous ~olutlon of NaOH, 0.16 parts of antlfoam agent (Knapsack LPKN 158), 10.53 parts of 47.5% aqueous solutlon of -~
sodlum slllcate (whose Na20sS102 ratlo ls 1.2.4), 10.0 parts of ~ -a 12% aqueou~ solutlon of ~odlum hypochlorlte and 0.8 part of a 45% aqueous solutlon of a bleach-reslstant anlonlc surfactant ~-(Dowfax 3B2); these addltlons may be made under any deslred mlxlng condltlons, e.g., wlth slmple stlrring (although lt may ~ -be convenlent to contlnue the hlgh shear dlsperslng actlon for ~ `
such mlxlng). The mlxture ls then sub~ected to a mllllng ~ -actlon, as by pasglng lt through an in-llne mlll such as a Tekmar"Dlspax Reactor" twhlch operates at a top speed of 22 meters per second) whlch sub~ects the mlxture to a hlgh shear rate for a relatlvely short tlme (e.g. the "resldence tlme" ln the mlll may be merely two ~econds or legs). The prlnclpal effect of thls is to further deagglomerate the clay particles, as lndlcated by a slgnlflcant lncrease ln the yleld value, e.g.
ralslng the yleld value of the mlxture by some 33%.

, , 1 ~ 2 5 3 6 7 62301-1325 The resultlng mixture ls thlxotroplc. It ls belleved that the partlcle slze of the dlspersed solid partlcles therein ls so small that some 80% by welght, or more, have partlcle slzes below 10 mlcrons. The mlxture ls at a temperature ln the nelghborhood of 120-130F (at thls temperature lts vlscoslty ls hlgher than at say 70F). It ls dralned off from the mlxlng vessel (e.g., from a bottom valve when the vessel has a conlcal bottom, or from a lower slde valve of a substantlally flat-bottomed mlxlng vessel). About 10% of the mlxture remalns as a "heel" ln the vessel7 owlng to lts flow characteristlcs lt ls difflcult to remove all the compositlon from the ves~el.
The entlre procedure descrlbed above 18 then repeated over-and-over ln the same mlxlng vessel without removlng the heels at ali.
The hlgh-speed dl~perser may comprlse a clrcular horlzontal plate having alternately upwardly and downwardly extendlng clrcumferentlal teeth, whlch plate ls mounted (on a vertlcal downwardly extendlng shaft) æo ias to rotate æo rapldly that the clrcumferentlal speed (of the teeth) læ more than about 75 feet per second ~e.g. 90 feet per second). For lab-oratory operatlon a Cowles hlgh speed disperser ls sultable;
for larger æcale operatlon a Myers model 800 serles hlgh ~peed dlsperser may be used. These hlgh speed dlspersers reduce partlcles by lmpact grlndlng by the toothed plate and by laml-nar shear stress on the mlxture. The shear generates heat ln the batch, ln addltlon to the heat generated by the dlssolvlng, hydratlon, etc. At the resulting relatlvely hlgh temperature the lngredlent~ are more æoluble and on crystalllzatlon on coollng wlll glve relatlvely small partlcles whlch do not settle rapldly lf at all. The hlgh speed dlsperser lnduces a ' 16 1 3 2 ~ 3 6 7 62301-1325 ~,~
~rolllng~ of the mlxture l.e. the path of movement of the mlx-ture ls downward centrally of the vessel, outwardly along the rotatlng plate, upwardly along the slde walls of the vessel and -~
inwardly at the upper surface of the mlxture. In the course of thls movement deslrable deaeration occurs, l.e., alr (whlch is always lntroduced when powders are added) wlll leave the mlx-ture during the lnward leg of its clrcult. -Apparently, after processlng of the composltion des- -~
cribed above, crystal growth occurs to form many larger and relatlvely unlform-slzed crystals (as shown by photomicro-graphs). Thus Fig. 4 indlcates that crystals havlng diameters -~
on the order of 80 microns are pre~ent. These crystals appear to contain polyphosphate but have not yet been fully lndenti-fled. ~
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Example 4 ls repeated except that the STPP powder is a Monsanto anhydrous STPP made by the known "dry process" and comprlslng anhydrous STPP humldlfled to the extent that lts content of water of hydratlon ls ~% (or somewhat hlgher, e.g.
1~%). It's phase I content is about 20%. This STPP was also -used ln Example 3.

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.''~ ~ ,' ' '' ~32~67 2301-1325 Example 4 is repeated except that the initial propor-tion of water is 28.0 parts, the second proportion of water is 13.637 parts, and prior to the addition of the attapulgite clay there is added 1.11 parts of 45% aqueous solution of sodium polyacrylate (Acrysol LMW-45N*, having a molecular weight of about 4500). The amount of K2CO3 here is 3 parts and the amount of Na2CO3 is 4 parts.
The products of Examples 4-6 were found to have the following characteristics: -Example viscosity (cps) 4000 6000 4400 yield value (dynes/cm2) 450 600 450 capillary drainage time (min) 8.2 5.6 6.1 centrifugal separation (%) 16 26.3 12 Thixotropy index 5 4.3 4.1 "Centrifugal separation" is measured by centrifuging at 275G as described in Example 3, above, and measuring the volume of the clear liquid layer in relation to the total volume.
"Thixotropy index" is the ratio of the viscosity at 30 rpm to that at 3 rpm, measur~d at room temperature with a Brookfield HATD viscometer, #4 spindle, as described in said Serial No. 432,542. ~
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1~2~367 In Example 6 a soluble chlorine bleach-reslstant polymer ls present. It is found that the presence of the poly-mer improves the reslstance to separatlon of the product on -standing or on centrlfuging, wlthout lmpartlng a correspondlng-ly large lncrease in the vlscoslty of the product. It wlll be appreclated that the polymer ls present here ln a very hlghly concentrated (saturated) electrolyte solutlon. It ls also -found that the presence of the polymer leads to lmproved pro-tectlon of the over-glaze layer of dishware (fine china). In work, thus far, ~hese effects have been observed wlth poly-acrylic acld salts, whlch have been found to be entlrely com- ~
patlble wlth chlorine bleach and wlth the clay ln this system, -e.g. the active chlorine content is malntained, as ls the vis-cosity. Polymers of different molecular weights may be used;
for lnstance, the polymer may have a molecular welght less than 10,000 or a molecular welght of 100,000 or more. Preferred molecular welghts range from about 1,000 to 500,000. Molecular -weights of from about 1000 to 50,000 are partlcularly notable for providing less fllmlng on glass. The proportlons of poly-mer may be ln the range of 0.01 to 3% with the lower propor- ~ -tions being more sultable for the hlgher molecular welght poly-mers (e.g. 0.06% for a 300,000 molecular welght polymer). .
Other bleach-reslstant polymers may be employed e.g. Tancol 731 whlch ls a sodlum ~alt of a polymerlc carboxylic acid havlng a M.W. of about 15000.
In thls application all proportlons are by welght un-less otherwise lndlcated. In the Examples atmospherlc pressure ls used unless otherwlse indlcated. ~ :
It is understood that the foregoing detalled descrlp-tlon is glven merely by way of lllustratlon and that varlations ~
may be made thereln without departing from the splrit of the ~ -lnvention. -~

,,~ '`, . .

Claims (7)

1. An aqueous thixotropic automatic dishwasher composition comprising a liquid phase which is water containing a detergent builder effective amount of dissolved alkali metal tripolyphosphate and alkali metal silicate and a thixotropically effective amount of a dispersed non-swelling clay thickener and a solid phase which is mainly sodium tri-polyphosphate, the composition containing a stabilizing amount of a water-soluble potassium compound in such amount that the K.Na weight ratio is in the range of about 0.04 to 0.5.

2. A composition as in claim 1 having a yield value of at least 200 dynes/cm2.

3. A composition as in claim 2 containing a chlorine bleach, an alkali metal carbonate and a bleach-resistant surfactant.

4. A composition as in claim 1 in which said composition contains about 20 to 25% sodium tripolyphosphate.

5. A composition as in claim 3 wherein potassium carbonate is present.

6. A composition as in claim 3 wherein potassium tripolyphosphate is present.

7. A composition as in claim 3 including potassium pyrophosphate.