CA1327739C - Process for making thixotropic detergent compositions - Google Patents

Abstract

ABSTRACT

Process for making a thixotropic detergent slurry, particularly suitable for improved performance in making composition useful in household automatic dishwashers. A slurry of particles of alkaline water-soluble builder salt, particularly sodium tripolyphosphate, is formed in a liquid containing dissolved alkaline builder salt, such as alkali metal carbonate. The proportion of solid particles is so high that the slurry has a viscosity of about 20,000 to 60,000 centipoises.
This viscous slurry is subjected to wet grinding with a high speed disperser. Water and powdered clay are then added and the clay is deagglomerated in the mixture by mechanical action. Improved compositions containing limited amounts of potassium compounds and water-soluble polymers are also disclosed.

Description

The present invention relates to a process for making a thixotropic detergent slurry which comprises forming a slurry of solid particles of alkaline water-soluble builder salt in a liquid which is water saturated with alkaline water-soluble builder salt, the proportion of such solid particles being so high that said slurry has a viscosity of about 20,000 to 60,000 centipoises, subjecting said viscous slurry to a high speed disperser operating at a tip speed of at least about 75 feet per second to effect wet grinding of said solid particles, then adding water, to lower the viscosity of said slurry, and powdered clay, and deagglomerating said clay in said slurry by mechanical action in the presence of said solid particles of soluble builder salt. Preferably said particles are at least in major part, sodium tripolyphosphate and said clay is attapulgite clay.
;One aspect of this invention relates to an aqueous thixotropic automatic dishwasher detergent comprising a liquid `Iphase which is water containing dissolved tripolyphoshate, silicate and alkali metal ions and 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 Application Serial No. 432,542 filed July 15, 1983 discloses certain compositions of this type.
It has now been found that greatly improved results are obtained by including a limited proportion of a water-soluble potassium compound, e.g., a potassium salt (or KOH), in the composition, to provide a K:Na weight ratio which is 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 resulting product is much more stable B

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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 corresponding potassium salt results in a considerable reduction in viscosity (e.g. as measured with a Brookfield HATD viscometer, at 25C at 20 rpm using spindle #4), greater stability against separation on aging (e.g., at room temperature), and inhibition of growth r 62301-132g of relatlvely large crystals on storage. The reduction ln viscoslty makes for easler handling ln the productlon plant, easler dlspenslng ln use, and makes lt easler for the consumer to destroy the thlxotroplc structure of the product (by shaklng the contalner in whlch lt ls packaged) so that it can be poured readlly lnto the detergent cup(s) of a household automatlc washlng machlr.e.
In a preferred embodlment ln formulatlng the product, the proportlons and lngredlents set forth ln the above-mentloned Canadlan Appllcatlon Serlal No. 432,542 may be employed. In that appllcatlon, one set of ranges of proportlons is, approximately, by welght:
(a) 8 to 35~ alkall metal trlpolyphosphate, (b) 2.5 to 20% sodlum slllcate, (c) 0 to 9% alkall metal carbonate, , (d) 0.1 to 5% chlorlne bleach stable, water-dlsperslble organlc detergent actlve materlal, (e) 0 to 5% chlorlne bleach stable foam depressant, (f) chlorlne bleach compound ln an amount to provlde about 0.2 to 4% of avallable chlorlne, and (g) thlxotroplc thlckener ln an amount sufflclent to provlde the compositlon wlth thlxotropy index of about ~.5 to 10.

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, ---` 1 327739 Preferably, in the compositions discloset herein, the proport$on of sodium tripolyphosphate is above 15% (more preferably in the range of about 20 to 25 or 30%), the proportion of sodium ~ilicat is at least about 4~ (such as in the range of about 5 to 10 or 1 15X), the proportions of alkali metal carbonate is about 2 to 6 ¦1 or 7Z, the proportion of chlorine bleach is such as to provide I¦ above 0.5% available chlorine ~e.g. about 1 to 2% available Cl), ¦¦ the proportion of detergent active material is in the range of Il 0.1 to 0.5X. Calcula~ed as SiO2, a preferred range of pro-t~ ¦ portions of sodium silicate represents about 3.5 to 7 SiO2 in the composition.
The proportion of water in the compo~itions (measured by "Cenco*mois~ture analyzer" (in which the Bample iB heated, by an infrared lamp, until lt comes to constant weight) iB preferably in the range of about 40-50X more preferably about 43-48X such as about 44 or 46X.
The composltions disclosed herein usually have p~s well above ll or 12. In one preferred type of formulation, the composition when diluted with water to 0.75X concentration has a p~ in the ran8e of about 10.7 to 11.3.
The composition disclosed herein are preferably for~ulated to have vlscosities (measured with a BrookfieIt*~ATD
~iscometer at 25C at 20 rpm using spindle ~4) of less than about 8000 centipoises and more preferably in the range of about 2,000 or 3,000 to 7,000 centipoises such ag about 4,000 to 6,000 centi-poises. The viscosity, and other properties, are preferably *T.M.

~ ` 1 327739 measured several days (e.g., a week) after the composition is preparet; it is good prsctice to ghake the sample before measuring I its viscosity and to let the vigcometer run for some 90 seconds before taking the reading.
i The compositions disclosed herein have yield values ¦well above 200 dynes per cm2 and are preferably formulated to have Yield values of less than about 1100 dynes¦cm2 and more than about 300 dynes/cm2, more preferably less than about 900 dynes/cm2 Il such as about 400 to 600 dynes/cm2. The yield value is an in-,¦dicatlon of the shear rate at which the thixotropic structure breaks down. It is measured with a Haake RV 12 or RV 100 ro-tatlonal viscometer using spindle MVIP at 25C with a shear rate I rising linearly in 5 minutes tafter a 5 minute rest period) from I zero to 20 sec. 1. In the Haake viscometer, a thin layer of I the material i8 sheared between a rotating cylinder and the I closely ad~acent cylindrical wall of the surrounding container.Fig. 1-3 are graph~ obtained on such testing of the products of the three Examples indicated thereon, with the peak~ Y showing the yleld values.
Another factor measured with the afore~ait Haake vlscometer is the de8ree to which the co~posltlon recovers its thixotropic structure. In one measurlng technlque after the 5 mlnute perlot of lncreaslng shear rate mentloned above, the rotatlon 18 decelerated to zero over 5 minutes then after 8 30 ~econd rest perlod the rotatlon i~ agaln accelerated to ralse the shear rate llnearly ln 5 mlnutes from zero to 22.6 ~ec.~l.
Thls glves a second yield value, i.e. peak~ Yr in Flg. 1.

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1 32773q Preferably thls second (recovered) yleld value 18 at least 200 dynes/cm2, such as 50%, 75% or more of the lnltlally measured yleld value.
Flg. 4 ls a photomlcrograph (taken on the scale lndlcated thereon) of the composltlon of Example 4.
The followlng Examples are glven to lllustrate thls lnventlon further.
In these Examples, Attagel #50 ls powdered attapul-glte clay (from Engelhard Mlnerals & Chemlcals, whose trade literature indlcates that, as produced, it contalns about 12 wt.~ free molsture, as measured by heating at 220F, and has a B.E.T. surface area of about 210 m2/g calculated on a moisture-free basis)~ Graphtol Green ls a colorlng agent1 LPKN 158 is ; an antlfoam agent from American Hoechst (Knapsack) comprlslng a 2~1 mlxture of mono- and di- (C16-C18) alkyl esters of phos-phoric acld, the sodlum sllicate has an Na20,SiO2 ratio of 1,2.4~ Dowfax 3~2 ls 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 mater-lal ls present as the pyrophosphate. The water used 18 delon-lzed water unless otherwlse lndlcated.

Trade-mark 6 1 32713q l, ~XAMPLE 1 The following iDgredients are added to a vessel in '! the order given below while mlxing with a conv~tional propeller-il type laboratory stirrer. The temperature~ and mising times at var$ous stages are alco indicatea below:
mass(g) temperature(F) lQ~ Graphtol green (color~ 5 130F water 1746 molten LPRN 158 (antifoam) 8 Dowfax 3B2 (surfactant) 40 126 (2 min) 4:1 mixture of Attagel ~50 and TiO2 white pigment 180 122 (1 mln) 120 (3 min) sota ash 275 134 (1 min) 132 (3 min) Finely powdered STPP hesahydrate 750 127 (1 min) 125 (3 min) 124 (5 min) 47.5Z aqueous solution of sodium 421 ~illcate premised with 50Z aqueous ~olutlon of NaO~ 150 118 (3 min) 13Z aqueous solution of NaOCl 500 108 (3 mln) Finely powdered STPP hesahydrate 750 108 (1 mln) Total 5000g 10~ ~5 ~in) i 327739 The viscoslty of the mixture, measured as lndicated ;above, i~. about 5000 centipolse6 after sging for 3 weeks at :l 100F and is about 4800 centfpoises after 3 months aging at j 100F.
'l In this Example~ the STPP hexahydrate has the fol-.1 lowing approximate size distrlbution:
¦ U.S.S. Sieve X
on #10 0 ~ on ~40 0 ! on #100 25.4 on ~200 31.5 on ~325 16.5 through #325 25.9 The followlng formulations are preparet and thelr propertles are measured 8~ indicated below:
The lngredlents are ml~ed ln the ollowing order:
water, color, clay, one balf of tbe phosphate, defoam~r, hypo-: chlorlte, sotlum carbonate, potas~ium carbonata, NaOa, sllicate, ~econd half of phosphate, surfactant.

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i Ingredients Proportlons a b c d I Clay (attagel 50) 3.285 3.285 3.285 3.285 3.285;' ST~P 23.0 23.0 17.01 16.5 23.0 i Potassium tripo-lyphosphate - - - 6.5 Potassium Pyro-i phosphate - - 5.99 - 0 i Sodium Carbonate 5.0 - 5.0 5.0 2.5 Potassium Carbonate - 5.0 - - 2.5 i Sodium ~ypochlorite Il (12X2 9.375 9-3759 375 9-375 9-375 ;I Sodium Hydroxide jl ~50%) 2.05 2.052.05 `2.05 2.05 ¦ Sodium S~licate l~ (47.5%) 10.53 10.5310.53 10.53 10.53 il Surfactant ~Dow-fax 3B-2) 0.80 0.800.80 0.80 0.80 Defoamer (Knap-sack Lp Kn) 0.16 0.160.16 0.16 0.16 Color 0.381 0.381 0.381 0.381 0.381 Water Balance Properties capillary drain-age time (min.~ 8.212.1 10.9. 11.4 11.2 Viscosity ~cps) on 100F agin8 1 week 9080 31002900 5120 5400 2 weeks 9200 34802820 6340 5240 3 weeks 9300 36003040 6700 6560 The capillary dralnage tlme i- a conventlonal te~t ln whlch a 6.8 cm. diamoter clrcle l~ trawn on a 15 cm dlameter ~heet of Whatman slze 41 fllter paper, plastlc nnulu~ ~3.5 cm in~lde dlameter, 4.2 cm outslde diametor, 6.0 c~ blgh) ic placed ver-tlcally, concentrlc wlth the clrcle, on the fllter paper, and the annulus 1B filled wlth the composltlon to be tested. Llquld from the composition is thereby absorbed lnto the fllter paper and spreats slowly to the drawn circle. The time wblch elapses until the liquid contacts the circle 1B measurea at three predetermlned locatlons and an average value is calculated.

_ g _ .- l 1 327739 i1 The following formulatlons are prepared by mlsing the ingredients in the order indicated. The compositions are ' then centr$fu3ed at 275 G untll there is no further lncrease in !
the volume of the clear separated liquid (continuous) phase and I the re6ulting liquid is analyzed:
:. a b c d deionized water 27.106 ;, color 0.016 I sotium carbonate 6 4 2 0 potassium carbonate 0 2 4 6 STPP 21.106 - ~ !
delonized water 14.184 ---- _ ¦ Attagel ~50 4.00 T102 0.444 50X solution of NaO~ 2.5 ~ --.-... -47.5X solutlon of sodium sllicate 13.684 ~~
l antifoam 0.16 ~~ - -! 13Z solutlon of NaOCl 10.0 -~- ---- . ......... ...
45% eolution of ur-factant 0.8 ~~ -~~

100.00 .
Thus the compositions are ldentical e~cept for their R:Na ratio~

Propertie6 of Product a b c d visc061ty after 1 day at room temperature 8320 5520 4200 2120 after 3 week6 at room temperature 8550 6200 4500 2420 aftOeF aging at 9400 8000 5600 3400 ¦l Speclfic gravity 1.37 1.37 1.40 1.39 , Propertie~ of liquid ;~ i! Obtained by Centrifuging .!
viscosity at 25C
I! relative to water at ¦1 1 CpB. 4.4 4.4 4.8 6.3 Z soluble silicate (calculated at mol ratlo Na20:S102 of ` 1:2.4) 7.5 7.3 7.3 7.1 i I X carbonate I! l (calculated as Na2C03) 8.8 8.5 7.4 6.6 ¦ % phosphate ~calculated as 5P3010) 1.7 2.5 3.7 6.1 specific gravity 1.257 1.262 1.276 1.30 !

1 The viscositles of the product for tbis E~ample ~A are measured with a Brookflelt aVT ~i~co~eter splndle No. 5 at ,j, 80F ~26.7C.).
Examples 4-6 below lllu~trate a new and useful method for making the products described above (contalniug ~ 1¦ llnlt~d unt- of pDt-BDiU~ It C - D 1BO b~ u--d for n-~iDg .i, 11 -11- l other products of the type shown in the previously mentioned Canadian Application Serial No. 432,542 (e.g. in which the potassium compound is not 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 i9 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 more efficiently and rapidly in the substantial absence of the clay.

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6~301-1324 In the method lllustrated in Examples 4-6 the bullder salt which is to constltute the ma~or portion 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 addltlon causes bullder salt to be thrown out of solutlon (e.g. by common lon effect) and thus to recrystalllze as tiny crystals.
Another slgnlflcant feature of the mlxlng method lllustrated ln Examples 4-6 ls the fact that lt enables repeat-ed batches of reproduclble propertles to be made uslng theentlre "heel" of the prevlously formed batch as an lngredlent of each successlve batch.
As lndlcated earller, the use of the process lllus-trated in Examples 4-6 ls not llmlted to the maklng of compo-sltlons contalnlng potasslum salts. Whlle lt has thus far found lts greater utlllty ln maklng formulatlons ln whlch the clay ls attapulglte, lt may also 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 as bentonlte (e.g., Gelwhlte GP*) or hectorlte.

In 32.0 parts of delonlzed water mlxed wlth a small amount of a plgment (l.e., 0.028 parts of Graphtol green, an agueous paste contalnlng 28~ plgment) there are completely dlssolved 2.0 parts K2C03 (whose water solublllty 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 of hydration are added whlle continuously sub~ectlng the mlx-ture to the actlon of a hlgh speed dlsperser. The amount of STPP ls much more than that which ls soluble ln the amount of water present; lts solublllty ln water ls about 20g per 100 ml at 25C. In thls example, the STPP ls a product of Olln Corp.
havlng a phase I content of about 50~, a sodlum sulfate content of about 2%, and a very flne partlcle slze, it ls a blen~ of powdered anhydrous STPP made by the known "wet process" and powdered STPP hexahydrate. On adding the STPP to the solution lt hydrates rapidly, formlng hard crystalllne lumps comprlslng STPP hexahydrate. (It wlll be noted that 23 parts of STPP has the capaclty, ln formlng the hexahydrate, to take up about 7 parts of water). The mlxture ls at flrst a thln slurry of undlssolved STPP ln a llquld whlch ls a supersaturated solu-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~ its vlscoslty rlses to about 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 durlng the process, sodlum carbonate crystalllzes (ln the form of very flne 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 pow~r consumptlon of the dlsperser and an addltlonal rlse ln temperature (e.g., to 150F, whlch causes lncreased dlssolutlon of bullder salts~ these wlll, ln turn, recrystalllze ln flne form-on coollng). Thls grlndlng ls contlnued for about 5 mlnutes after the lnltlal thlckenlng of the slurry~ durlng grlndlng the vlslble ~T

t 3277~

lumps of material disappear and the particle slze of the undls-solved particles ls reduced so that, lt ls belleved, substan-tlally all the partlcles have dlameters below 40 mlcrons. Then a further 9.367 parts of water are added, lowerlng the vlscos-lty to less than 10,000 cps (e.g. ln the nelghborhocd of 5000 cps, measured as indlcated above), after whlch 3.3 parts of Attagel #50 and 0.732 parts of whlte TlO2 (anatase) plgment are added to the hlghly alkallne mixture (whose pH ls well over 9, e.g. 10.5) while the mlxture ls contlnuously sub~ected to the actlon of the hlgh speed dlsperser, whlch dlsperses (deagglo-merates) the clay to a large extent, so that the thlck mlxture becomes homogeneous and smooth ln appearance. Then there are added 2.70 parts of 50% aqueous solutlon of NaOH, 0.16 parts of antlfoam agent (Knapsack LPKN 158), 10.53 parts of 47.5% aque-ous solutlon of sodlum slllcate (whose Na2O:SlO2 ratlo 18 1,2.4), 10.0 parts of a 12~ aqueous solutlon of sodlum hypo-chlorlte and 0.8 part of a 45% aqueous solutlon of a bleach-reslstant anlonlc surfactant (Dowfax 3B2)t these addltlons may be made under any deslred mlxlng condltlons, e.g., wlth slmple stlrrlng ~although it may be convenient to contlnue the hlgh shear dlsperslng actlon for such mlxlng). The mlxture ls then sub~ected to a mllllng actlon, as by passlng lt through an ln-llne mlll such as a Tekmar "dlspax reactor" (whlch 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 seconds or less). The prlnclpal effect of thls ls to further deagglomer-ate the clay partlcles, as lndlcated by a slgnlflcant lncrease ln the yleld value, e.g. ralslng the yleld value of the mlxture by some 33%.

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-The resultlng mlxture 15 thlxotroplc. It ls belleved that the partlcle slze of the dlspersed solld partlcles thereln ls so small that some 80~ by weight, 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 18 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 ves~el; owlng to lts flow characterlstlcs lt ls dlfflcult to remove all the composltlon from the vessel.
The entlre procedure descrlbed above ls then repeated over-and-over ln the same mlxlng vessel wlthout removlng the heels at all.
The hlgh-speed dlsperser may comprlse a clrcular horlzontal plate havlng alternately upwardly and downwardly extendlng circumferentlal teeth, whlch plate 19 mounted (on a vertlcal downwardly extendlng shaft) so as to rotate so rapldly that the clrcumferential speed tof the teeth) ls more than about 75 feet per second (e.g. 90 feet per second). For laboratory operatlon a Cowle~ hlgh speed dlsperser 18 sultable~
for larger scale operatlon a Myers model 800 serles hlgh speed dlsperser may be used. These hlgh speed dlspersers reduce partlcles by lmpact grlnding by the toothed plate and by laml-nar shear stress on the mlxture. The sheer generates heat ln the batch, ln addltlon to the heat generated by the dlssolvlng, hydratlon, etc. At the resultlng relatlvely hlgh temperature the lngredlents are more soluble and on crystalllzatlon on coollng wlll glve relatlvely small partlcles whlch do not settle rapldly lf at all. The hlgh speed dlsperser lnduces a "rolllng" of the mlxture l.e. the path of movement of the -h..
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1 32773~

mlxture ls downward centrally of the vessel, outwardly along the rotatlng plate, upwardly along the slde walls of the vessel and lnwardly at the upper surface of the mlxture. In the course of thls movement deslrable dearatlon occurs, l.e., alr (whlch is always lntroduced when powders are added) wlll leave the mlxture durlng the lnward leg of lts clrcult.
Apparently, after processlng of the composltlon des-crlbed above, crystal growth occurs to form many larger and relatlvely unlform-slzed crystals tas shown by photomlcro-graphs). Thus Flg. 4 lndlcates that crystals havlng dlameterson the order of 80 mlcrons are present. These crystals appear to contaln polyphosphate but have not yet been fully lndentl-fled.

Example 4 ls repeated except that the STPP powder ls 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' 8 phase I content ls about 20~. Thls STPP was also used ln Example 3.

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Example 4 is repeated except that the initial proportion 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, measured at room temperature with a Brookfield HATD viscometer, #4 spindle, as described in said Application Serial No. 432,542.

*Trade Mark In Example 6 a ~oluble chlorine bleach-resl~tant polymer lf present. It iB found that the presence of the polymer improve6 the reoistance to separation of the protuct on standlng or on centrifuging, without imparting a correspondingly large increase in the viscosity of the product. It wlll be appreciated that the polymer i~ present here in a very highly concentrated ~saturated) electrolyte solution. It i8 aleo found that the pre~nceof the p~ymer lead~ to improved protection of the over-glaze layer of di5hware(fine chlna). In work, thu~ far, these effects have been ob~erved with polyacrylic acid salts, which have been found to be entlrely compatlble with chlorine bleach ! and wlth the clay in thls system, e.g. the active chlorlne con-il tent 18 maintained, as i8 the viscosity. Polymers of different ¦ molecular welghts may be used; for lnstance, the polymer mayhave a molecular weight less than 10,000 or a molecular weight of 100,000 or more. The proportions of polymer may be ln the ran8e of 0.01 to 3% with the lower proportions bein8 more suit-able for the hi8her molecular weight polymers ~-8- 0.06% for i a 300,QOO molecular weight polymer~. Other bleach-resistant ~ polymers may be employed.
: In this applicatlon all proportions are by weight unlese otherwioe lndicatod. In the Examples atmospheric pres~ure io used unless otherwioe indicated.
It i8 understood that the foregolng detailed de-ocriptioD is given merely by way of illustration and that varl-atlone may be made thereln without departing from the splrt of ¦ tbe 1DVe lon.

Claims (11)

1. Process for making a thixotropic detergent slurry which comprises:
forming a slurry of solid particles of an alkaline water-soluble builder salt in a liquid which is water saturated with the alkaline water-soluble builder salt, the proportion of such solid particles being so high that the slurry has a viscosity of about 20,000 to 60,000 centipoises, subjecting the viscous slurry to a high speed disperser operating at a top speed of at least about 75 feet per second to effect wet grinding of the solid particles, then adding water, to lower the viscosity of the slurry, and powdered clay, and, deagglomerating the clay in the slurry by mechanical action in the presence of the solid particles of the soluble builder salt, wherein a K:Na weight ratio in the slurry is from about 0.04 to about 0.05.

2. Process as in Claim 1, in which the particles are, at least in major part, sodium triolyphosphate and the clay is attapulgite clay.

3. Process as in Claim 1 in which a water-soluble anionic surfactant is then added to the resulting mixture.

4. Process as in Claim 1 in which the viscous slurry is formed by adding substantially anhydrous sodium tripolyphosphate to a solution of an alkali metal carbonate in water.

5. Process as in Claim 4 in which the concentration of the alkali metal carbonate in the solution is so high that the presence of the added sodium tripolyphosphate causes crystallization of sodium carbonate from the solution.

6. Process as in Claim 1, carried out in a mixing vessel, which process includes the step of:
discharging most of the resulting deagglomerated clay-containing slurry from the vessel, while leaving a substantial heel of the slurry in the vessel and, then repeating the process in the presence of the heel, the heel constituting about 5 to 20% of the mixture during the repetition.

7. Process as in Claim 2 in which the proportion of the clay is about 1 to 5%.

8. Process as in claim 1, wherein conditions are chosen so that the resulting thixotropic detergent slurry has the following composition in water.
(a) 8 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, and, (g) dispersed non-swelling clay as a thixotropic thickener in an amount sufficient to provide the composition with thixotropy index of about 2.5 to about 10, in which the alkali metal tripolyphosphate, sodium silicate and the alkali metal carbonate are the alkaline water-soluble builder salt;
and the slurry has (1) a pH of above 11, (2) a viscosity of from about 2,000 to 7,000 centipoises and, (3) a yield value of from about 200 to about 1,100 dynes/cm2.

9. Process as in Claim 8, in which the particles are, at least in major part, sodium tripolyphosphate and the clay is attapulgite clay.

10. Process as in Claim 8 or 9 in which the proportion of the clay is about 1 to 5%.

11. Process as in any one of claims 1 to 9 wherein the clay is used together with TiO2 white pigment.