LU86042A1 - DETERGENT FOR A DISHWASHER - Google Patents

Description

One aspect of the present invention relates to a thixotropic aqueous detergent for an automatic dishwashing machine, comprising a liquid phase which is water containing, in dissolution, tripolyphosphate, 5-silicate and alkali metal ions and, in dispersion, a thickener of the non-swelling clay type (preferably of the attapulgite type) and a solid phase which consists mainly of sodium tri-polyphosphate. The composition preferably also contains a chlorine bleach (preferably dissolved sodium hypochlorite) and an anionic surfactant resistant to the bleach. It also preferably contains an alkali metal carbonate. United States patent application 497,615 (= FR.83.11811) filed May 24, 1983 describes certain compositions of this type.

It has now been found that greatly improved results are achieved by including a limited proportion of a water-soluble potassium compound, for example a potassium salt (or KOH) in the composition to obtain a K: Na weight ratio. which is in the range of about 0.04 to 0.5, preferably about 0.07 to 0.4, for example about 0.08 to about 0.15. The resulting product is much more stable in the sense that it has less tendency to thicken adversely or separate on aging, for example at -38ec. Likewise, the replacement of part of the sodium salt by the same weight of the corresponding potassium salt results in a considerable reduction in viscosity (for example as measured using a Brookfield HATD viscometer at 25 ° c at 20 rpm using spindle # 4), greater stability against separation upon aging (e.g., at room temperature), and inhibition of the growth of relatively large crystals to aging. The decrease in viscosity facilitates handling in the production facility, distribution in service, and helps the consumer to destroy = 35 ia thixotropic structure of the product (by shaking the container in which it is contained), so that it can be easily poured into the "* or detergent compartments of a ma- \ -n. k 2 tt | domestic automatic machine for washing dishes.

In the formulation of the product, the proportions and the ingredients indicated in the aforementioned United States patent application No. 497,615 can be used.

I; In this application, a series of ranges of proportions is approximately, by weight: (a) 8 to 35% of alkali metal tripolyphosphate, (b) 2.5 to 20% of sodium silicate, (c) 0 to 9 % of alkali metal carbonate, 10 (d) 0.1 to 5% of an active material of the organic detergent type dispersible in water and stable with respect to a chlorine bleach * (e) 0 to 5% of foam depressant stable against chlorine bleach, 15 (f) a chlorine compound as bleach, in an amount which can provide about 0.2 to 4% of available chlorine , and (g) a thixotropic thickener in a proportion sufficient to give the composition a thixotropy index of approximately 2.5 to 10.

Preferably, in the compositions described here, the proportion of sodium tripolyphosphate is greater than 15% (better still in the interval of about 20 to 25 or 30%), the proportion of sodium silicate is at least about 25 4% (for example in the range of about 5 to 10 or 15%), the proportion of alkali metal carbonate is about 2 to 6 or 7%, the proportion of chlorine bleach is such that it provides more than 0.5% of available chlorine (for example approximately 1 to 2% of available Cl), the proportion of active detergent material is in the range of 0.1 to 0.5%. Calculated as S i 0g, a preferred range of proportions of sodium silicate is about 3.5 to 7% SiO 4 in the composition.

The proportion of water in the compositions (measured 35 g using a Cenco humidity analyzer (in which the sample is heated by an infrared lamp), up to 1 3 i! O \.

9 * "3 (reaching constant weight) is preferably in the range of about 40 to 50%, more preferably about 43 to 48%, for example about 44 or 46%.

The compositions described here generally have a pH much higher than 11 or 12. In a preferred type of formulation, the composition, when diluted with water to a concentration of 0.75%, has a pH in the range of about 10.7 to 11.3.

The compositions described here are preferably formulated so as to have viscosities (measured with a Brookfield HATD viscometer at 25 ° C. at 20 rpm using a pin No. 4) of less than approximately 8000 mPa.s, and better still in the range of about 2000 or 3000 15 to 7000 mPa.s, for example about 4000 to 6000 mPa.s. Viscosity, and other properties, can be measured a few days (eg, a week) after the composition has been prepared; an advantageous practice is to shake the sample before measuring its viscosity and letting the viscometer run for about 90 seconds before taking the reading.

The compositions described herein have flow indices well above 20.0 Pa (200 dyne / cmz) and are preferably formulated to have flow indices of less than about 110.0 Pa and greater than about 30 .0Pa, more preferably less than about 90.0 Pa, for example about 40.0 to 60.0 Pa. The flow index is an indication of the shear rate at which the thixotropic structure collapses. It is measured with a 30 Haake RV 12 or RV 100 rotary viscometer using a ΜVIP spindle at 25 ° C with a shear speed which increases linearly in 5 minutes (after a rest period of 5 minutes) from zero to 20 seconds ” ^. In Haake's viscometer, a thin layer of the material is sheared between a rotating cylinder and the immediately adjacent cylindrical wall of the container. Figures 1-3 are graphs obtained with such a test on the products of the three examples * 4 shown, the crests Y showing the flow indices.

Another factor measured with the aforementioned Haake viscometer is the degree to which the composition recovers its thikotropic structure. In a measurement technique after the 5-minute period of increasing the shear speed mentioned above, the rotation is decelerated to zero in 5 minutes, then after a rest period of 30 seconds, the rotation is still accelerated to increase the shear speed linearly in minutes from zero to 20 seconds "^. This gives a second flow index, ie Yr in Figure 1. Preferably, this second index of flow (recovered) is at least 20.0 Pa, for example 50%, 75% or more of the flow index initially measured.

Figure 4 is a photomicrograph (taken to the scale indicated in this figure) of the composition of Example 4.

The following nonlimiting examples are given by way of illustration of the present invention.

In these examples, Attagel No. 50 is powdered attapulgite clay (from Engelhard Minerais & Chemicals, whose commercial literature indicates that, as produced, it contains about 12% by weight of free moisture, as measured by heating to 104 ° C, and has a BET specific surface area of approximately 210 mz / g calculated on a moisture-free basis); Graphtol Green is a coloring agent; LPKN 158 is an anti-foaming agent from American Hoechfet (Knapsack) comprising a 2: 1 mixture of mono- and dialkyl esters of C5 | C- | q of phosphoric acid, sodium silicate has a ratio Na ^ OiSiO ^ of 1: 2.4; Dowfax 3B2 is a 45% aqueous solution of sodium monodecyl- / didecyl-diphenyl oxide disulfonates, an anionic surfactant resistant to bleaching agents; STPP is sodium tripolyphosphate. Unless otherwise specified, STPP is added as the finely divided anhydrous commercially available material having a water content of about 0.5%; in this material, in general about · 4.5 to 6.5% of the material is present in the form of pyrophosphate. The water used is deionized water unless otherwise specified.

5 ’EXAMPLE 1

The following ingredients are introduced into a container in the order shown below while mixing with a conventional laboratory stirrer of the paddle type. The temperatures and the mixing times at the various stages are also indicated below:

Mass Temperature (g) (° C)

Graphtol green 10% (dye) 5

Water at 54.4 ° C 1746 15 LPKN 158 (defoamer) 8

Dowfax 3B2 (surfactant) 40 52.2 (2 min) 9: 1 mixture of Attagel No. 50 and TiOg as white pigment 180 20 50.0 (1 min) 48.9 (3 min)

Anhydrous sodium carbonate, 275 .K2C03 75 56.7 (1 min) 56.6 (3 min) STPP hexahydrate in fine powder, 750 52.8 (1 min) 51.7 (3 min) 51.1 (5 min) 30 Aqueous solution at 47, 5% sodium silicate 421 previously mixed with a 50% aqueous solution of NaOH 150 47.8 (3 min) 35 13% aqueous solution of NaOCl 500 42.2 (3 min) 6 t STPP hexahydrate in fine powder 750 42 , 2 (1 min)

Total 5,000 g 41.7 (5 min)

The viscosity of the mixture, measured as indicated above, is approximately 5000 mPa.s after 3 weeks aging at 38 ° C, and approximately 4800 mPa.s after 3 months aging at 38 ° C.

In this Example, the STPP hexahydrate has the following approximate particle size distribution:

Remains on a mesh screen of: 10 ("» "") (%) 2.00 0 0.42 0 0.149 25.4 0.074 31.5 15 0.044 16.5

Passes through a 0.044 mm mesh screen 25.9 EXAMPLE 2

The following formulations are prepared and their properties are measured as indicated below:

The ingredients are mixed in the following order: ** »water, dye, clay, half of the phosphate, antifoam, hypochlorite, sodium carbonate, potassium carbonate, NaOH, silicate, the second half phos-25 phate, .the surfactant.

Ingredients Proportions i h. £ d

Clay (Attagel 50) 3,285 3,285 3,285 3,285 3,285 STPP 23.0 23.0 17.01 16.5 23.0

Potassium tripolyphosphate 30 - - - 6.5

Potassium pyrophosphate - - 5.99 - 0

Sodium carbonate 5.0 - 5.0 5.0 2.5

Potassium carbonate - 5.0 - - 2.5 35 t 7 _a _b _c d

Sodium hypochlorite (12%) 9.375 9.375 9.375 9.375 9.375

Sodium hydroxide (50%) 2.05 2.05 2.05 2.05 2.05 5 Sodium silicate (47.5%) 10.53 10.53 10.53 10.53 10.53

Surfactant (Dowfax 3B-2) 0.80 0.80 0.80 0.80 0.80

Defoamer 10 (Knapsack LPKN) 0.16 0.16 0.16 0.16 0.16

Dye 0.381 0.381 0.381 0.381 0.381

Water

Properties Flow time 15 capillary (min) 8.2 '12.1 10.9 11.4 11.2

Viscosity (mPa.s) after aging at 38 ° C

1 week 9080 3100 2900 5120, 5400 20 2 weeks 9200 3480 2820.. 6340 5240 3 weeks 9300 3600 3040 6700 6560

The capillary flow time is a conventional test in which a circle with a diameter of 6.8 cm is drawn on a sheet of 15 cm diameter of paper-wire-25 be Whatman of dimension 41, a ring of plastic material (internal diameter of 3.5 cm, external diameter of 4.2 cm, height of 6.0 cm) is placed vertically, concentrically with the circle, on the Tilter paper, and the ring is filled with the composition to be tested. The liquid from the composition is thus absorbed on the filter paper and slowly spreads out to the traced circle. The time which elapses until the liquid comes into contact with the circle is measured at three predetermined points and an average value is calculated.

35 EXAMPLE 3 '

The following formulations are prepared by mixing the ingredients in the order indicated. The compositions are 8

,. *. 1.j. -JT · - »Mi · · -5 I

then centrifuged at 275 g until there is no more increase in the volume of the clear separate liquid phase (continuous) and the resulting liquid is analyzed: £ to £ £ 5 Deionized water 27,106 id id id

Dye 0.016 id id id

Sodium carbonate 6 420

Potassium carbonate 0 246 STPP 21,106 id id id 10 De ionized water 14,184 id id id

Attagel N ° 50 4.00 id id id

Ti02 0.444 id id id

2.5% NaOH solution 2.5 id id id

47.5% solution of .dd. sodium silicate 1 3,684 id id id

Defoamer 0.16 id id id

13% NaOCl solution 10.0 id id id

· 45% solution.

surfactant 0.8 id id 20 100.0

Thus, the compositions are identical except 17 made for their K: Na ratios.

Product properties a b c d 25 - _ - _

Viscosity (mPa.s) after 1 day at room temperature 8320 5520 4200 2120 after 3 weeks at room temperature 8550 6200 4500 2420 30 After aging at 38 ° C for 7 weeks 9400 8000 5600 3400

Density 1.37 1.37 1.40 1.39 Λ *

J

l ° J9rJitfes of 1 igjuuLe obtained by centrifugation ... - abcdl Visqositë at 25 ° c by \ 5 ^ water supply. at ImPa.s 4.4 4.4 4.8 6.3 J i of soluble silicate | (calculated at a molar ratio Na20: SiQ2 of 1: 2.4} 7.5 7.3 7.3 /, 1 I% carbonate (calculated! 10 as Na2CO3) 8.8 8, 6 7.4 * '*, 6 t% of phosphate (calculated as Na ^ P ^ O-jg) 1.7 3.5 3, t 6.1 1 Density 1,257 1,262 1,276 1,30 r Ί 5 [- J The viscosities of the product of this Example are measured with a screw cos ir? Trr Βϊ ocfc <i- * ld RVT. Pin N ° 5 to I 26.7 ° C.

II. * · * S examples 4 to 6 below illustrate a new and useful method for manufacturing the products described above (containing limited quantities of potacum). It can also be used to manufacture other products of the type indicated in the application for a brief î ces Γ. United States of America Ne497 616 mentioned above (example * in which H- potassium compound is absent) as well as other detergent suspensions comprising fine particles of salt s irrial detergency adjuvants water-soluble dis-; Pnrsées in water containing in dissolution! and this. ' adjuvant of detergency, clay or other thick. if ssanc colloï- * 30 dal, and the surfactant. In these Examples (in! Esc "1s ies the adjuvant detergency salt contained in the product consist largely of IF PP .y-

(V

ê draté plus soditm carbonate rvdrêtëK v se un i * ~ - | -.very viscous mixture (for example v ^ cost curd | 3 s? (î 000 to 60,000 mPa s' of a 'té 1 ir'? i iée c'esc, 'a saturated solution highly s: z', · '..Sevant detergency salts? T; i as cor.st ·' 'cv. Domûiant, cu particles' * doo ùi! Cdju. ···. * ·.; P. Laroence nydroso! Ut * "e .

10

This viscous mixture is subjected to grinding of the undissolved particles using a high speed dispersing apparatus after which the solid particles of the clay thickener are added and the clay is mechanically disaggregated; then the rest of the ingredients in the formula (for example other liquids or materials that dissolve or disperse easily in the liquid phase with a high electrolyte content) can be mixed with it.

The mixture may then be subjected to another mechanical action of high shear to deagglomerate the clay again. It has been found that with this process, the prior dispersion of the clay in an aqueous medium is not necessary. Solid clay particles are easily dispersed even if the medium is strongly alkaline. The grinding of the particles of adjuvant of undissolved detergency is carried out much more efficiently and rapidly in the almost total absence of the clay.

• In the process illustrated in examples 4 to 6, the detergency builder salt which constitutes the dominant part of the undissolved particles is preferably added to an aqueous solution which already contains such a concentration of other dissolved detergency builder salts than this addition results in the detergency builder salt being released from the solution (eg, by a common ion effect) and thus recrystallized as tiny crystals.

Another important feature of the mixing process illustrated in Examples 4-6 is the fact that it makes it possible to manufacture repeated batches having re-producible properties by using the entire "heel" of the batch previously formed as an ingredient in each batch. successive.

As indicated above, the use of the process illustrated in Examples 4 S 6 is not limited to the manufacture of compositions containing potassium-35 sium salts. Although it has so far found its greatest utility in the manufacture of formulations in which the ar-.

• η gile is attapulgite, it can also be used for compositions in which all or part of the clay is of the swelling type, for example a clay of the smectite type such as bentonite (for example Gelwhite GP) or T'hectorite.

EXAMPLE 4

In 32.0 parts of deionized water mixed with a small amount of a pigment (i.e. 0.028 part of Graphtol green, an aqueous paste containing 28% pigment), ^ 0 is dissolved completely 2.0 parts of I ^ CO. ^ (of which solubility in water is more than 100 parts per 100 parts of water even at 0 ° C) and 5.0 parts of granular sodium carbonate (including solubility in water is about 45 parts for 100 to 35 °°). The solution has a temperature of about 32.2 ° C. 23.116 parts of powdered STPP containing approximately 0.5% water of hydration are then added, while continuing to subject the mixture to the action of a high-speed dispersing apparatus. The amount of STPP is much greater than that which is soluble in the amount of water present; its solubility in water is approximately 20 g per 100 ml at 25 ° c. In this example, STPP is a product of Olin Corp. having a phase I content of about 50%, a sodium sulfate content of about 2%, and a very small particle size; it is a mixture of anhydrous powdered STPP made by the known "wet process" and of powdered hexahydrate STPP. When STPP is added to the solution, it hydrates rapidly, forming hard crystalline lumps comprising STPP hexahydrate. (Note that 23 parts of STPP can, by forming 3 ^ of the hexahydrate, absorb up to about 7 parts of water). The mixture is first of all a dilute suspension of STPP not dissolved in a liquid which is a supersaturated solution. The temperature rises due to the hydration reaction, reaching a maximum of around 60Dc. In about 33 to 4 minutes, the mixture becomes much more viscous; its viscosity is more than 20,000 mPa.s (for example around 40,000-50,000 mPa.s, as measured at the suspension temperature, for example with a Brookfield RVT viscometer, pin No. 6, at 10 rpm). It is believed that during the process, the sodium carbonate separates from the solution phase by crystalization (in the form of very fine crystals) due to the effect of common ions (sodium from STPP). When the mixture has become viscous, the high-speed dispersing apparatus acts to grind the particles (eg hydrated STPP) to a fine particle size; the grinding action is indicated on the one hand by the increased energy consumption of the dispersing apparatus and on the other hand by an additional rise in temperature (for example that at 65.6 ° C., which causes increased dissolution of the detergency builder salts; these, in turn, recrystallize as fine crystals upon cooling). This grinding is continued for approximately 5 minutes after the initial thickening of the suspension; during grinding, visible lumps of material disappear and the particle size of the undissolved particles is reduced so that it is assumed that almost all of the particles have diameters less than 40 microns. Then add another 9 ',' '367 parts of water, lowering' the viscosity to less than 10,000 mPa.s (for example in the vicinity of 5,000 mPa.s, measured as indicated above. ), to which is added 3.3 parts of Attagel No. 50 and 0.732 part of white TiO 4 (anatase) as * pigment to the highly alkaline mixture (whose pH is much higher S 9, for example 10.5 ), however, that the mixture is continuously subjected to the action of the high-speed dispersing apparatus, which disperses (deagglomerates) the clay to a great extent, so that the thick mixture becomes homogeneous and smooth appearance. 2.70 parts of aqueous 50% NaOH solution, 0.16 part of anti-foaming agent (Knapsack 35 LPKN 158), 10.53 parts of aqueous solution containing 47.5% sodium silicate (including Na ^ OrSiO ^ ratio is 1: 2.4), 3 10.0 parts of a 12% aqueous solution of hypochlorite

It sodium and 0.8 part of a 45% aqueous solution of an anonic surfactant resistant to the bleaching agent (Dow-fax 3B2); these additions can be made under any desired mixing conditions, for example by simple agitation (although it may be convenient to continue the high shear dispersing action for such mixing). The mixture is then subjected to a grinding action, for example by passing it through a continuous mill such as "Dispax Reactor" from Tekmar which operates at a top speed of 22 meters per second) which subjects the mixture to a high rate of shear for a relatively short time (for example the "residence time '1 in the mill can be as little as two seconds or less). The main effect of this is to deagglomerate the clay particles, as indicated by a marked increase in the flow index, for example by raising the flow index of the mixture by approximately 33%.

The resulting mixture is thixotropic. It is believed that the particle size of the dispersed solid particles therein is so small that about 80% by weight, or more, has particle sizes of less than 10 microns. The mixture is at a temperature in the region of 49-54.5ec (at this temperature, its viscosity is higher than, for example, 21.1 * c) - It drips from the mixing container (for example a lower valve when the container has a conical bottom, or a lower side valve of a mixing container with a substantially flat bottom). About 10% of the mixture remains as a "bead" in the container; due to its flow characteristics, it is difficult to remove the entire composition from the container.

The procedure described above is then repeated in its entirety many times in the same mixing container without being able to remove the heel.

35 The high-speed dispersing apparatus may include a circular horizontal plate having * »14 w · circumferential teeth alternating up and down, which plate is mounted (on a vertical shaft directed down) Turn quickly enough so that the circumferential speed (of the teeth) is greater than about 22.86 m / s (for example 24.5 m / s).

For laboratory scale operation, a Cowles high speed dispersing apparatus is suitable; for operation on a larger scale, one can use. Use a Myers high speed disperser S, 10 model 800. These high speed dispersers reduce particles by grinding, impact, by the toothed plate and by the laminar shear force exerted on the mixture. Shear generates heat in the load, in addition to the heat generated by dissolution, hydration, etc. At the resulting relatively high temperature, the ingredients are more soluble and, after crystallization on cooling, give relatively small particles which dissolve only slowly, if not at all. The high-speed dispersing device causes the mixture to "roll", that is to say that the path of the movement of the mixture descends in the center of the container, outwards along the rotary plate , upward along the side walls of the container, and inward at the top surface of the mixture. During this movement, a desirable deaeration occurs, that is, the air (which is always introduced when the lightning is added) leaves the mixture during its inward journey.

Apparently, after processing the composition described above, crystal growth appears giving many crystals of larger and relatively uniform size (as indicated by the photomicrographs). Thus, Figure 4 indicates the presence of crystals with a diameter of about 80 micrometers. These calls appear to contain polyphosphate but have not been fully identified.

:> 115 EXAMPLE 5

Example 4 is repeated with the difference that the STPP powder * is an anhydrous Monsanto STPP made by the known "dry process" and comprises anhydrous humidified STPP 5 as long as its water content of hydration is 0 , 5% (or slightly more, for example 1.5%). Its phase I content is approximately 20%. This STPP is also used in Example 3.

EXAMPLE 6 Example 4 is repeated with the difference that the initial proportion of water is 28.0 parts, the second proportion of water is 13.637 parts, and before the addition of attapulgite clay , 1.11 parts of a 45% aqueous solution of sodium polyacrylate (Acrysol LMW-45N, having a molecular weight of about 4500) are added. The amount of K ^ CO ^ here is 3 parts and the amount of ^ £ 00 ^ is 4 parts.

The products of Examples 4 to 6 were found to have the following characteristics: Example 4 5 6

Viscosity (mPa.s) 4000 6000 4400 * r »

Flow index (Pa) 45 60 45

Flow time 8.2 5.6 6.1 25 capillary (min) Separation by centrifugation (%) 16 * 26.3 12

Thixotropy index 5 4.3 4.1

"Separation by centrifugation" is measured by centrifugation at 275 g as described in Example 3, above, and by measuring the volume of the transparent liquid phase relative to the total volume.

The "thixotropy index" is the ratio of the viscosity at 30 rpm to that at 3 rpm, measured at room temperature with a Brookfield HADT aiming meter, pin No. 4, as described in said application Γ * 16,497,615.

In Example 6, a soluble polymer resistant to chlorine bleaches is present. The presence of the polymer has been found to improve the resistance to separation of the product at rest or by centrifugation, without imparting a proportionally greater increase in the viscosity of the product. Note that the polymer is present here in a very highly concentrated (saturated) electrolyte solution. It is also found that the presence of the polymer results in better protection of the glaze layer of the dishes (fine porcelain). In fact, so far, these effects have been observed with polyacrylic acid salts, which have been shown to be fully compatible with chlorine bleaches and the ar-15 gile of this system; for example the content of active chlorine is maintained, as well as the viscosity. Polymers of different molecular weights can be used; for example, the polymer may have a molecular weight of less than 10,000, or a molecular weight of 100,000 or more. Preferred molecular weight ranges are from about 1,000 to 500,000. Molecular weights from about 1,000 to 50,000 are particularly noteworthy for obtaining less film formation on the glass. The proportions of polymer can be from 0.01 to 3%, the lower proportions being more suitable for polymers of high molecular weight (for example 0.06% for a polymer of molecular weight of 300,000). Other polymers resistant to bleaching agents can be used, for example Tancol 731 which is a sodium salt of a polymeric carboxylic acid having a molecular weight of about 15,000.

In the present application, all the proportions are expressed by weight unless otherwise indicated. In the examples, atmospheric pressure is used, unless otherwise specified.

It goes without saying that the invention is not limited to the I embodiments described and that it is susceptible of various variants without departing from its scope.

Claims (10)

118 CLAIMS 1 - A thixotropic aqueous composition for an automatic dishwashing machine, characterized in that it comprises a liquid phase which is water containing 5-alkali metal tripolyphosphate, a clay type thickener, a compound chlorine bleaching and about 0.01% to about 3% water-soluble polymeric carboxylic acid. 2. Composition according to claim 1, character-ized in that the acid is an acrylate. 3. Composition according to claim 2, characterized in that the acrylate is a sodium polyacrylate having a molecular weight of approximately 1000 to 500,000. 4. Composition according to claim 3, character-ized in that the polyacrylate has a molecular weight of 1000 to 50,000. 5. Composition according to claim 4, characterized by the presence of a carbonate. 6. Composition according to claim 5, cqracté-20 laughed in that the carbonate comprises potassium carbonate. 7. Composition according to claim 5, characterized in that it contains potassium tripolyphosphate. 25 8 - Composition according to claim 5, character ized in that it comprises potassium pyrophosphate. 9. Composition according to claim 6, characterized in that the clay is a non-swelling clay. 10. Composition according to claim 9, character-ized in that the clay is 1 attapulgite.