NO165405B - PROCEDURE FOR THE PREPARATION OF TIXOTROPIC DETERGENTS. - Google Patents

Description

The invention relates to a method for production

of a thixotropic detergent slurry, and the method is characterized by the fact that a slurry of solid particles of alkaline water-soluble building salt is formed in a liquid which is water saturated with alkaline water-soluble building salt,

using an amount of such solid particles so high that the slurry has a viscosity of 20,000-60,000 centipoise, and subjecting the viscous slurry to treatment in a high-velocity dispersing apparatus operating at a tip velocity of at least 22.9 m/s for to cause wet-

grinding of the solid particles, after which water, to lower the viscosity of the slurry, and powdered clay are added,

and the clay is deagglomerated in the slurry by mechanical action in the presence of the solid particles of soluble building salt.

In US Patent No. 4740327 which was filed on May 24, 1983,

are certain detergents of the in the present process

manner manufactured type described.

In the present method, the quantities and

the ingredients specified in the above-mentioned US patent no. 4740327 are used. In this US patent, the approximate weight percentages for the various components are as follows:

(a) 8-35% alkali metal tripolyphosphate

(b) 2.5-20% sodium silicate

(c) 0-9% alkali metal carbonate (d) 0.1-5% of a chlorine bleach stable,

in water dispersible, organic, detergent active

material

(e) 0-5% of an antifoam which is stable

against chlorine bleaches

(f) a chlorine bleach compound in an amount sufficient

to give 0.2-4% available chlorine, and

(g) a thixotropic thickener in an amount which

is sufficient that the mixture will get a

thixotropy index of 2.5-10.

In the detergents described here, the amount of sodium tripolyphosphate is preferably above 15% (more than 20-25 or 30%), the amount of sodium silicate at least i%

(e.g. 5-10 or 15%), the amount of alkali metal carbonate 2-6 or 7%, the amount of chlorine bleach such that it gives more than 0.5% available chlorine (e.g. 1-2% available Cl) ., and the amount of detergent-active material 0.1-0.5%'i .. Calculated as SiO2, a preferred range for the amount of sodium silicate is 3.5-7% SiC>2 in the detergent.

The amount of water in the detergents (measured* with a moisture analyzer of the Cenco type, where the sample is heated with an infrared lamp until it attains a constant weight) is preferably 40-50, more preferably 43-48, e.g. approx..44 or 46, %. ;The detergents described here have - as a rule - pH values well above 11 or 12. For a preferred type of recipe, the detergent, when diluted with water to a 0.75% concentration, has a pH of 10.7-11.3 . The detergents described here are preferably manufactured so that they have viscosities (measured with a viscometer of the Brookfield HATD type at 25°C and 20 rpm, using spindle no. 4) below 8000 centipoise; and more preferably within the range of 2000 or 3000-7000 centipoise, e.g. 4000-6000 centipoise. The viscosity and other properties can be measured several days (e.g. a week) after the detergent has been prepared. It is good practice to shake the sample before measuring its viscosity and to let the viscometer run for approx. 90 seconds before the reading is taken. The detergents described here have flow limit values well above 200 dyn/cm<2> and are preferably manufactured so that they have flow limit values of below 1100 idyn/cm<2> and, above 300 dyn/cm, more preferably below 900 dyn/em <2>, such as e.g. 400-600 dyn/cm2... The yield point value is an indication of the shear stress at which the thixotrope structure breaks down. It is measured with a rotational viscometer of the type Haake RV 12 or RV 100 in use, avvspindle MVIP at 25 C and with an increasing shear stress. linearly for 5 minutes (after a rest period' of 5 minutes) . from 0 to »20 sec.<*1>.

In the Haake viscometer, a thin layer of material is subjected to shear stress between a rotating cylinder and the closely adjacent cylindrical wall of the surrounding container. Fig. 1-3 shows curves obtained by such testing of the products according to the three examples indicated in the figures, where the peaks Y show the yield strength values.

Another factor that is measured with the above-mentioned Haake viscometer is the degree to which the detergent obtains

bake its thixotropic structure. In a measurement method carried out after the above period of 5 minutes of increasing shear stress, the rotation is decelerated to zero within 5 minutes, and after a rest period of 30 seconds the rotation is then accelerated again so that the shear stress increases linearly within 5 minutes from 0 to 22.6 sec. 1. This gives another yield limit value, i.e. the peaks Y r in Fig. 1. Preferably, this second (recovered) yield limit value is at least 200 dyn/cm, which e.g. 50%, 75% or more of the originally measured yield strength value.

Figure 4 is a photomicrograph (taken with the scale indicated on the figure) of the detergent according to example 1.

The invention is described in more detail using the examples below.

In these examples, 'Attagel' No. 50 is powdered attapulgite clay which, according to the manufacturer, contains approx. 12% by weight of free moisture, measured when heated to 10 4°C, and has a B.E.T. surface area of approx. 210 m 2 /g calculated on a moisture-free basis, "Graphtol Green" is a coloring agent, LPKN 158 is an antifoam agent comprising a 2:1 mixture of mono- and di- (Cj_6~C^g) alkyl esters of phosphoric acid, sodium - the silicate has a Na20:SiO2 ratio of 1:2.4, Dowfax<®> 3B2 is a 45% aqueous solution of Na-monodecyl/didecyldiphenyloxide disulfonates which is a bleach-resistant, anionic surfactant, and STPP is sodium tripolyphosphate. If nothing else is specified, STPP is added in the form of a finely pulverized, commercially available, anhydrous material with a water content of c. 0.5%. In such a material, typically 4.5-6.5% of this is present in the form of the pyrbic phosphate. The water used is deionized water unless otherwise stated.

The following examples 1-4 show the present one. method for producing thixotropic detergent slurries.

The present method can also be used for preparation of other products of the type described in the previously mentioned US patent no. 4740327 (e.g. where the potassium compound is not present), as well as for other detergent slurries comprising finely divided particles, of water-soluble, inorganic building salts dispersed in water which contains dissolved building salt, clay or•another colloidal thickening agent> and surface-active agent. In these examples (in which the particles of builder's salt in the product mainly consist of STPP hexahydrate plus hydrated sodium carbonate) a highly viscous (with a viscosity of 20,000-60,000 eps) mixture is obtained from a limited amount of water, a highly alkaline, saturated solution.of builder's salts and, as the main component, undissolved particles'of water-soluble builder's salt. In this viscous mixture, the dissolved particles are ground down using a high-speed dispersion device, after which solid particles of the clay thickener are added, and the clay is mechanically deagglomerated. Then the rest of the ingredients according to the recipe (eg other liquids or materials which easily dissolve or disperse in the liquid phase with a high electrolyte content) can be mixed in. The mixture may then be subjected to further mechanical high shear stress application to further deagglomerate the clay. It has been found that when this method is used, it is not necessary to carry out a preliminary dispersion of the clay in an aqueous medium. The solid particles of clay are easily dispersed even if the medium is strongly alkaline. The degradation of the undissolved building salt particles takes place far more efficiently and quickly when the clay is essentially not present.

In the method described in examples 1-4, the builder's salt, which is to make up the bulk of the undissolved particles, is added to an aqueous solution which already contains such a high concentration of another dissolved builder's salt that this addition causes building salt will be pulled out of the solution (e.g. by normal ion action) and thus recrystallize in the form of small crystals.

Another important characteristic of the mixing method

described in Examples 1-4, is the fact that it enables repeated batches of reproducible properties to be produced using the entire "remainder" of the previously formed batch as a component in each subsequent batch.

The use of the method described in examples 1-4 is not limited to the production of detergents containing potassium salts. Although this has so far proved to be of the greatest use for the production of detergents in which the clay is attapulgite, it can also be used for detergents in which all or part of the clay is of the swelling type, e.g. a smectite-type clay, such as ben-tonite (eg "Gelwhite GP") or hectorite.

Example 1

In 32.0 parts of deionized water mixed with a small amount of pigment (ie 0.028 parts of "Graphtol" green in the form of an aqueous paste containing 28% pigment), 2.0 parts of K2C03 ^v;i's water solubility is above 100 parts per 100 parts of water even at °C) and 5.0 parts of granular sodium carbonate (whose water solubility is about 45 parts per 100 parts of water at 35°C) completely dissolved. The solution has a temperature of approx. 32°C. Then 23.116 parts of powdered STPP containing approx. 0.5% water of hydration added while subjecting the mixture to a high speed dispersing apparatus. The amount of STPP is far greater than the amount that is soluble in the amount of water present. Its solubility in water is approx. 20 g/100 ml at 25°C. According to this example, the STPP used is a product with a phase I content of approx. 50%, a sodium sulphate content of approx. 2% and a very fine particle size. It is a mixture of powdered anhydrous STPP

produced using the known "wet process" and powdered STPP hexahydrate. When STPP is added to the solution, it hydrates rapidly to form hard, crystalline clumps comprising STPP hexahydrate (it should be noted that

23 parts STPP when forming the hexahydrate is able to

record approx. 7 parts water). The mixture is first a thin slurry of undissolved STPP in a liquid which is a supersaturated solution. The temperature rises due to the hydration reaction and reaches a peak at approx. 60°C. During approx. 3 to 4 minutes, the mixture becomes far more viscous. Its viscosity rises to over 20,000 eps (e.g. 40,000-^50,000 eps measured at slurry temperature for example with a Brookfield RVT viscometer, spindle #6 at 10 rpm).

It is assumed that the sub-process crystallizes sodium carbonate (in the form of very finely divided crystals) out of the solution phase due to the common-ion effect (of the sodium in the used STPP). When the mixture has become viscous, the high-speed dispersing apparatus operates so that the particles (eg of hydrated TPP) are reduced to a finely divided particle size. On the one hand, the grinding down effect is manifested by the increased power consumption of the dispersing device and by a further increase in temperature (e.g. to 65.6°C which ■ causes■ increased dissolution of building salts. These will in turn recrystallize in finely divided form when cooling). This painting continues for approx. 5 minutes after the initial thickening of the slurry. During the painting down, the visible clumps of material disappear, and the size of the undissolved particles is reduced so that, it is assumed:-:,. essentially, all particles have diameters below -40 µm. Then an additional 9.367 parts of water is added, lowering the viscosity below 10,000 eps (eg, to, near 5,000 eps, measured as above); after which 3.3 parts of "Attagel No. 50" and 0,732 parts of white Ti£>2 (anatase) pigment is added to the strongly alkaline mixture (if the pH is well above 9, e.g. 10.5), while the mixture is continuously exposed to the action of high-speed dispersing devicesfc. which disperses (deagglomerates) the clay to a great extent, so that the thick mixture becomes homogeneous and acquires a.smooth appearance.i. Then 2.70 parts of a 50% aqueous solution of NaOH, 0.16 parts of antifoam agent ("Knapsack LPKN 158") are added. 10 , 53 parts of a 4 7.5% aqueous solution of sodium silicate (whose ratio

Na2O:SiO2 is 1:2.4), 10.0 parts of a 12% aqueous solution

of sodium hypochlorite and 0.8 part of a 45% aqueous solution of a bleach-resistant anionic surfactant (Dowfa 3B2). These additions can be made under any desired mixing conditions, e.g. with simple agitation (although it may be convenient to continue the high shear stress dispersion action for such a mixture). The mixture is then subjected to grinding down, e.g. in that the mixture is passed through a mill arranged in the production line, such as a mill of the type "Tekmar Dispax Reactor" (which works with a top speed of 22 m/s), and this exposes the mixture to high shear stress for a relatively short time ( for example, the "dwell time" can

in the mill turn in just two seconds or less). The main effect of this is that the clay particles are further deagglomerated, which manifests itself in a significant increase in the yield strength value, e.g. in that the yield strength value for the mixture is increased by approx. 33%.

The mixture obtained is t Lxotrope. It is assumed that

The particle size of the dispersed, solid particles in the mixture is so small that approx. 80% by weight or more have particle sizes below 10 µm. The mixture has a temperature of 48.8-54.5 oC (at this temperature its viscosity is higher than at, for example, 21°C). It is drained off from the mixing container (e.g. via a bottom valve when the container has a conical bottom, or via a low side valve when the mixing container has a substantially flat bottom). About. 10% of the mixture remains as a "residue" in the container. Due to its fluidity properties, it is difficult to

remove the entire mixture from the container.

The overall method described above is then repeated several times in the same mixing container without removing the "leftovers" at all.

The high-speed dispersing apparatus may comprise a circular, horizontal plate with circumferential teeth that alternately extend upward and downward, and this plate is mounted (on

a vertically downward pulling shaft) so that it rotates so fast that the circumferential speed (of the teeth) is greater than 22.9 m/s (eg 27.4 m/s). For execution in the laboratory

a high speed dispersing apparatus of the Cowles type is suitable. For execution on a larger scale, a Myers model 800 high-speed disperser tag apparatus can be used. These high-speed dispersers reduce the particles by impact grinding the toothed blade and due to laminar shear stress against the mixture. The shear stress develops heat in the batch in addition to the heat that is developed: "during the dissolution and hydration, etc. At the relatively high temperature obtained, the components are more soluble and, upon crystallization on cooling, will give relatively small<4> particles that do not settle to the bottom quickly if in the at all.. The high-speed dispersing apparatus initiates a "rolling" of the mixture, i.e. the path of movement of the mixture is directed centrally downwards in relation to the container, >outwards along the rotating plate,

upwards along the side walls of the container and inwards at the upper surface of the mixture. During this movement, a desired deaeration takes place, i.e. air (which is always introduced when powder is added) will leave the mixture during the inward portion of its circuit.

After treatment of the mixture described above, apparent crystal growth takes place with the formation of a number of larger crystals of relatively uniform size (as shown by means of microphotographs. Fig. 4 thus indicates that crystals with diameters of approximately 80 µm are present. These .crystals .seem to contain polyphosphate, but they are

not yet fully identified'..

Example 2

Example 1 is repeated, except for the STPP powder

an anhydrous STPP powder produced by the known "dry process" and comprising anhydrous STPPFspm has been moistened to such an extent that its hydration water content is 0.5%

(or somewhat higher, e.g. in 1.5%) . Its content of phase I is approx. 20%.

Example 3

Example 1 is repeated, except that the original amount of water is 28.0 parts and the second amount of water is 13.637 parts, and before the addition of the attapulgite clay, 1.11 parts of a 45% aqueous solution of sodium polyacrylate ("Acrysol LMW-45N" with a molecular weight of about 4500). The amount of K^CO-^ is here 3 parts and the amount of Na^cO-^ 4 parts.

The products according to examples 1-3 proved to have the following properties:

Capillary drainage time is a common test where a circle with a diameter of 6.8 cm is drawn on a sheet of diameter 15 cm and consisting of Whatman filter paper size 41, a plastic ring (3.5 cm inside diameter,

4.2 cm outside diameter, 6.0 cm high) is placed vertically, concentric with the circle, on the filter paper, and the ring is filled with the material to be examined. Liquid from the material is then absorbed in the filter paper and slowly spreads towards the drawn up circle. The time that elapses before the liquid comes into contact with the circle is measured at three predetermined locations, and an average value is determined.

"Centrifugal separation" is measured by centrifuging at 275G until there is no increase in the volume of the clear, separated liquid (continuous) phase and by measuring the volume of the clear liquid layer relative to the total volume.

"Thixotropy number" is the ratio between the viscosity at 30 rpm and the viscosity at 3 rpm, measured at room temperature with a viscometer of the BrookfieldoHATD type, spindle no. 4, as described in said US patent 4740322'."'

According to Example 3, an insoluble, chlorine bleach resistant polymer is present. It has been shown that the presence of the polymer improves the product's resistance to separation by standing or by centrifugation without this contributing to a correspondingly strong increase in the product's viscosity. It will be understood that polymer enrhef is present in a very highly concentrated (saturated) electrolyte solution. It has also been shown that. the presence of the polymer leads to improved protection of the overglaze layer on the tableware (porcelain). In tests which have been carried out so far, these effects have been shown by the use of polyacrylic acid salts which have been shown to be completely compatible with chlorine bleaches and with the clay in this system, e.g. that the fractious chlorine content is preserved in the same way as the viscosity. Polymers with different molecular weights can be used. For example, the polymer may have a molecular weight below 10,000 or <:>a molecular weight of 100,000 or higher. The amounts of polymer can lie within the range 0.01-3%, the lower amounts being more suitable for the polymers of higher molecular weight (e.g. 0.06% for a polymer with a molecular weight of 300,000)..' Others bleach-resistant polymers can be used.

Example 4

The following mixtures are prepared, using the present method, by mixing the ingredients in the order indicated. The mixtures are then centrifuged at 275 G until no increase in the volume of the clear, separated liquid (continuous) phase occurs, and the liquid obtained is analyzed:

Thus, the mixtures are identical except for their K:Na ratios.

The viscosities for the product according to this example are measured with a viscometer of the Brookfield RVT type with spindle no. 5 at 26.7°C.

All quantities here are based on weight unless otherwise stated. In the examples, atmospheric pressure is used if nothing else is specified.

Claims (7)

1. Method for producing a thixotropic detergent slurry, characterized in that a slurry of solid particles of alkaline water-soluble building salt is formed in a liquid which is water saturated with alkaline water-soluble building salt, using an amount of such solid particles that is so high that the slurry has a viscosity of 20,000-60 000 centipoise, and the viscous slurry is subjected to treatment in a high speed dispersing apparatus operating at a tip speed of at least 22.9 m/s to effect wet grinding of the solid particles, after which water, to lower the viscosity of the slurry, and powdered clay are added, and the clay is deagglomerated in the slurry by mechanical action in the presence of the solid particles of soluble building salt. 2. Method according to claim 1, characterized in that the particles i ' the least is mainly used sodium tripolyphosphate and as clay attapulgit clay. 3. Method according to claim 1, characterized in that a water-soluble, anionic, surfactant is then added to the mixture obtained. 4. Method according to claims 1-3, characterized in that the viscous slurry is formed by adding essentially anhydrous sodium tripolyphosphate to a solution of alkali metal carbonate in water. 5. Method according to claim 4, characterized in that such a high concentration of the alkali metal carbonate is used in the solution that the presence of the added sodium tripolyphosphate causes that sodium carbonate crystallizes from the solution. 6. Method according to claim 1 carried out in a mixing container, characterized in that it includes the step that the majority of the resulting slurry containing the deagglomerated clay is drained from the container, while a substantial remainder of the slurry is left in the container, after which the process is repeated in the presence of the remainder constituting 5-20% of the mixture during said repetition. 7. Method according to claims 1-6, characterized in that the clay is used in an amount of 1-5%.