WO1994029219A1

WO1994029219A1 - Stabilization of suspensions of very finely divided zeolitic alkali-metal aluminium silicates

Info

Publication number: WO1994029219A1
Application number: PCT/EP1994/001731
Authority: WO
Inventors: Wolfgang Seiter; Johannes Hachgenei; Rainer Scholl; Peter Freidank
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1993-06-04
Filing date: 1994-05-27
Publication date: 1994-12-22
Also published as: DE4318573A1

Abstract

Proposed is a way of stabilizing pumpable highly concentrated suspensions of very finely divided zeolitic alkali-metal aluminium silicates by means of selected water-insoluble clays with a particularly high swelling capacity.

Description

Stabilization of suspensions of very finely divided zeolitic alkali metal aluminum silicates

The present invention relates to a method for stabilizing pumpable suspensions of very finely divided zeolitic alkali metal aluminum silicates.

Such alkali metal aluminum silicates are used, for example, as builders for detergents, dishwashing detergents and cleaning agents, as molecular sieves, catalysts and sorbents and as an additive to ceramic frits and glazes.

As is known, the alkali metal aluminum silicates are prepared by hydrothermally reacting sodium silicate with sodium aluminate in the presence of alkali. The raw materials metered within defined concentration ranges form a highly water-containing gel in the precipitation container with an increase in viscosity. The precipitation is carried out in a relatively dilute solution and with vigorous stirring. The conversion into the highly ordered crystalline structure begins when the temperature is raised in the downstream crystallizing containers. After crystallization has ended, the mother liquor is drawn off via suitable separation devices (eg vacuum belt filter), and the approximately 30-50% by weight filter cake is washed. Mother liquor and washing water can partly flow back into the substance mixture directly or after evaporation in an evaporator system. (Ullmann's Encyclopedia of Industrie! Chemistry, 5th edition, volume A 8, keyword: detergents).

For further processing in detergents, the filter cake can be spray-dried or stabilized by additions in the form of a suspension.

DE 2527388 A1 discloses pumpable suspensions of the alkali metal aluminum silicates mentioned which are stabilized with at least one dispersant which is selected from: 1. an organic, macromolecular, carboxyl and / or hydroxyl group-containing polymer compound; 2. a phosphonic acid which has at least one further phosphonic acid and / or carboxyl group;

3. a phosphoric acid alkyl emulsifier with 3-20 C atoms in the alkyl chain;

4. a surfactant having a cloud point in water determined according to DIN 53917 - below 90 ° C;

5. a surfactant sulfonate;

6. a swellable water-insoluble silicate with a layered structure (layered silicate).

The dispersant is preferably used in amounts of 0.5 to 6% by weight, based on the total weight of the suspension. The suspensions contain 20 to 42% by weight of alkali metal aluminum silicates.

EP-0 000 130 B1 discloses silicate complexing agents for alkaline earth ions and processes for their production.

Special non-ionic surfactants, which also make their own contribution in the washing process, have become established as stabilizers in technology. In particular, fatty alcohol ethoxylates or oxo alcohol ethoxylates have been used in the past. These can stabilize alkali metal aluminum silicate suspensions during transport and interim storage for a sufficiently long period of time. In the usual processing by hot atomizing drying, however, these hot air and steam-capable ethoxylates tend to form so-called pluming, ie they are partially emitted in droplet and / or gaseous form with the tower exhaust air. The increasingly strict legal requirements regarding the concentration of organic compounds in the exhaust air therefore force in practice to lower the air temperatures and thus the production output in the atomization towers. Accordingly, the object of the present invention is to provide a method for stabilizing pumpable suspensions of very finely divided zeolitic alkali metal aluminum silicates, in which detergent-compatible and, in particular, detergent-active stabilizers are used which have no hot air volatility and which also have current ecological requirements enough detergent ingredients.

Surprisingly, it was found that specially selected swellable, water-insoluble sheet silicates with a particularly high swelling volume are particularly suitable for fulfilling the above-mentioned object.

Accordingly, a first embodiment of the present invention consists in a process for stabilizing pumpable suspensions of very finely divided zeolitic alkali metal aluminum silicates of the general formula (I),

xMe ₂ 0 ^• A1 ₂ 0 ₃ ^• ySiθ2 ^• 2H ₂ 0 (I)

in which Me is sodium and / or potassium, x is a number in the range from 0.8 to 1.3, y is a number in the range from 1.3 to 10 and z is a number in the range from 0 to 6, with a swellable water-insoluble Layered silicate, the layered silicate having a swelling volume in the range from 30 to 80 ml per 2 g of layered silicate. The swelling volume is determined by pouring 100 ml of fully demineralized water into a measuring cylinder, slowly and in portions adding 2 g of the layered silicate to the surface of the water and reading the volume of the layered silicate deposited after a standing time of 1 hour.

DE 25 27 388 describes the use of swellable, water-insoluble sheet silicates for the stabilization of alkali metal aluminum silicates, but the sheet silicates mentioned here are ultimately not suitable for the stabilization, since in the range of today's highly concentrated alkali metal aluminum silicate suspensions from 40 to 60% by weight, the amounts mentioned in DE 2527 388 AI of, for example, 2 to 4% by weight (Example 11) do not stabilize the AI lead potassium metal aluminum silicate suspension. Rather, solid suspensions that are no longer pumpable are obtained.

The above general formula (I) comprises a large number of substances which, although their chemical composition often differs only slightly, differ considerably in terms of their structure and properties. In addition to the chemical composition of crystalline types, the X-ray diffraction diagram is generally used to identify such zeolites. Of particular technical interest here are type A and X zeolites, but also, for example, P and Y.

For the purposes of the present invention, in particular highly concentrated pumpable suspensions of very finely divided zeolitic alkali metal aluminum silicates are used. While in DE 2527 388 Al generally pumpable suspensions with alkali metal aluminum silicates in the range from 25 to 40% by weight and in particular from 28 to 38% by weight are stabilized, since a yield point of about 42% by weight of alkali metal aluminum silicate is indicated, it was found with the aid of the present invention that even suspensions of up to 60% by weight of alkali metal aluminum silicate can be stabilized flowably. Accordingly, a further preferred embodiment of the present invention consists in that suspensions are used which contain 40 to 60% by weight, in particular 45 to 55% by weight and, with particular advantage, around 50% by weight of alkali metal aluminum silicates. The pH of such preferred suspensions is usually about 7 to 12.

The swellable, water-insoluble sheet silicates which are particularly selected in the context of the present invention and can preferably be used correspond to the general formula (II)

(Me ' ₂ 0) _a ^• (Me "0) _b • Me'" ₂ 0 ₃ • (Si0 ₂ ) _c

where the symbols have the following meaning:

Me '= sodium and potassium (the ratio of Na ₂ 0: K 0 preferably 10 to 100: 1 amounts),

Me "= magnesium and calcium (the ratio of MgO: CaO preferably being 0.5 to 3: 1), Me" ¹ = aluminum and iron, the ratio of A1 Ü3: Fe ₂ 03 preferably being 3 to 6: 1 , a = 1.6 to 6, preferably 3 to 5, b = 0.2 to 1, preferably 0.3 to 0.5 and c = 6.2 to 8, preferably 7.5 to 8.

EP-0 000 130 B1 describes that such swellable, water-insoluble sheet silicates can be prepared by loading alkali with a material obtained by acid activation of a mineral from the montmorillonite-beidellite series. In particular, acid-activated bentonite is used as the starting material. The acid-activated material is loaded with an alkali metal hydroxide, carbonate, phosphate or borate by dry or wet mixing. In particular, the loading of the acid-activated material is carried out in aqueous suspension and as a paste at 25 to 100 ° C. The swellable, water-insoluble sheet silicates produced in this way differ from the previously customary, commercially available sheet silicates, on the one hand, as described in EP-0000130 B1 by their particularly high specific surface area of about 200 to 350 m ² / g. According to the invention, however, it was found that the swellable, water-insoluble sheet silicates used according to the invention have a particularly high swelling volume. A commercial product from Südchemie, which is available under the name Vasagel (R), is advantageously used. As is known, water-insoluble layered silicates swell more or less quickly when they sink into water, depending on their swelling capacity, and occupy, for example, a more or less large space at the bottom of a measuring cylinder that corresponds to their swelling capacity.

The method for determining the swelling volume is carried out as follows: A commercially available, graduated measuring cylinder for 100 ml without spout

Rubber or ground glass stopper is filled with 100 ml of fully demineralized water. 2 g of the substance to be measured (swellable, water-insoluble layer silicate) is slowly and in portions, about 0.1 to 0.2 g each, added to the surface of the water with the spatula. You now wait for a portion to drop before adding the next portion.

After the 2 g of substance have been added and sunk to the bottom of the measuring cylinder, the amount of the swollen substance which it takes up in the measuring cylinder is read off in ml per 2 g after one hour. For the purposes of the present invention, it is therefore particularly preferred to use swellable layered silicates with a swelling volume of 50 to 70 ml determined in this way.

In the prior art, in particular in DE 25 27 388 AI, the amount of stabilizing agent to be used is described in a relatively wide range. It should be possible to use 0.5 to 6% by weight of stabilizing agents of the type mentioned at the beginning.

In the course of the present invention, however, it was found that when using specially selected, highly swellable, water-insoluble sheet silicates, the maximum amount of stabilizer can in no way be chosen freely. In particular, it was found that a high alkali content of the suspension to be stabilized resulted in a very high viscosity (> 10,000 Pas). Accordingly, it is preferred to set the alkali content of the suspension (filter cake) to values of less than 0.5% by weight (calculated as Na ₂ O). On the other hand, it is possible to increase the amount of swellable, water-insoluble sheet silicate in suspensions with a relatively low content of alkali metal aluminum silicate. For the purposes of the present invention, it has proven particularly advantageous to use suspensions which contain 0.1 to 2% by weight of the swellable, water-insoluble

Layered silicates included. Adequate stabilization of the suspension of alkali metal aluminum silicates over a long period (a few days to weeks) is possible within this range. If the specified amount is undershot, the stabilization effect is of course limited, while on the other hand, if the amount of stabilizer (layered silicate) is exceeded, it does not result in improved stabilization, but rather an increased viscosity, which occurs in particular in the case of highly concentrated alkali metal aluminum silicate suspensions. For the purposes of the present invention, therefore, particular preference is given to the stabilization of suspensions which contain 0.2 to 1% by weight of the layered silicates mentioned.

DE 25 27 388 A1 has already described that the suspensions can be prepared by simply mixing their constituents, the alkali metal aluminum silicates, for example as such or, if appropriate, from the preparation — already moist or in aqueous suspension — being used. It is particularly advantageous, also within the meaning of the present invention, to enter the alkali metal aluminum silicates which are still moist, for example as filter cakes, in a dispersion of the swellable, water-insoluble layer silicates. The dispersion of the layered silicates is preferably warmed somewhat, for example to 50-70 ° C.

However, it is also possible in the same way to use alkali metal aluminum silicates which have already been dried, ie which have been freed from adhering water and which may still have bound water. However, since the very finely divided zeolitic alkali metal aluminum silicates are usually already in suspended form, the layered silicate will in particular be incorporated directly into the suspension. In this case, it is particularly preferred to use the sheet silicates in large-scale production by using high-speed stirrers with speeds of more than 3,000 revolutions / min. in the alkali metal aluminum silicate suspension. Analogously, it is possible to use layered silicates in powder form or their aqueous suspensions. Due to thixotropy effects, a particularly good incorporation of a dry powder or an aqueous suspension is possible. If, for example, the layered silicate is pre-swollen in water, corresponding to a weight ratio of layered silicate to water of 1:10, a softer, more flowable batch is obtained. It was also found that the tolerance to higher alkalinity is greater. Through the use of swollen layered silicate, however, water is introduced into the filter cake, so that the concentration of alkali metal aluminum silicate drops. Therefore, if pre-swollen layered silicates are used, highly concentrated aqueous suspensions are preferred.

It is generally known that powdered layered silicates have an insufficient flowability and tend to form lumps. When these powdery layered silicates are introduced into the alkali metal aluminum silicate suspensions, the lump formation is increased by swelling of the layered silicates. These lumps would have to be destroyed again at great expense by introducing mechanical energy. So phyllosilicates are used in fine crystalline powder form in the inventive process, so be on the prevention of clot formation and thus to improve the ease of incorporation preferably those phyllosilicates used by known for these purposes additives to which spielsweise silicas (Aerosil® ^(R)), zeolites or count finely divided sodium sulfate powder, are fluidized.

For the purposes of the present invention, it is of course possible to use the further stabilizers described in DE 25 27 388 A1, which have already been listed above. It is particularly preferred to use these further dispersants in an amount of 0.1 to 3% by weight, based on the suspension.

The suspensions obtainable with the aid of the present invention are notable for particularly high stability. They can be pumped over a longer period of time (days to weeks), so that they make it easy to handle moist alkali metal aluminum silicates. Even after long interruptions in the pumping process, the suspensions can be pumped around again without any problems. Due to the high stability, the alkali metal aluminum silicate suspensions can also be transported sedimentation-stable in conventional tank tank wagons for several days without fear of the formation of useless or disruptive residues. There are also no phase separations. The highly concentrated alkali metal aluminum silicate suspensions are therefore in accordance with the present invention excellent as a delivery form of alkali metal aluminum silicates and for

Particularly suitable for delivery to detergent manufacturers, for example.

The alkali metal aluminum silicate suspensions can be stored at room temperature or at a higher temperature, pumped through pipelines or transported in some other way. The suspensions are usually handled at temperatures between room temperature and about 60 ° C.

The highly concentrated alkali metal aluminum silicate suspensions according to the invention are particularly suitable for further processing to appear dry, pourable or free-flowing products, for example for the production of powdered water softening agents and in particular washing and cleaning agents.

Since the swellable, water-insoluble sheet silicates to be used according to the invention have a binding capacity for calcium ions between about 700 and 1,000 meq / 100 g in a pH value range from about 9 to 11, according to EP-0 000 130 B1, when using these substances a detergent-active component is added, since the binding capacity of the layered silicates to be used here is about a power of 10 greater than the ion exchange capacity of natural bentonites, which is about 70 to 100 meq / 100 g.

B e i s p i e l e

In the following examples and comparative examples, the layer silicates 1 (according to the invention) and 2 (comparison) were used. As a further stabilizing agent, a tallow fatty alcohol with 5 moles of ethylene oxide per mole of tallow fatty alcohol was used. The chemical composition and important properties of the layered likate 1 and 2 are listed below:

Layered Silicate 1: Layered Silicate 2:

1 (according to the invention) (comparison)

Si0 ₂ 57.6% by weight 66.9% by weight

A1 ₂ 0 ₃ 15.0% by weight 12.7% by weight

Na ₂ 0 2.9% by weight 2.4% by weight

MgO 3.3% by weight 2.3% by weight

CaO 1.0% by weight 1.7% by weight

K 0 1.0% by weight 1.4% by weight

Ti0 ₂ 0.1% by weight 0.2% by weight

Fe ₂ 0 ₃ 1.5% by weight 1.7% by weight

Particle size

D50 in acetone 19.08 µm 16.84 µm

Bulk density 660 g / 1 620 g / 1 free moisture 11.7% by weight 6.0% by weight

Residual moisture content 5.9% by weight 4.8% by weight

Total moisture 17.6% by weight 10.8% by weight

Whiteness

(Berger) 61.2% 52.00%

Swelling volume 67 ml 18 ml Example 1:

1.1 kg of an alkali metal aluminum silicate filter cake (Sasil ^R ) from the applicant's current production with a content of 49.8% by weight of alkali metal aluminum silicate (free Na ₂ 0 = 0.25% by weight) were removed in the course of Layered silicate 1 in an amount of 0.5% by weight, based on the filter cake, was added for 20 minutes at a stirring temperature of 50 ° C. and a stirring speed of 450 revolutions / min.

The formation of sediment and the separation were evaluated, as described below, at a storage temperature of 48 ° C. and at room temperature (RT). Tables 1 to 2 show the data thus obtained.

Example 2:

1.1 kg of the filter cake mentioned in Example 1 were analogously mixed with the layered silicate 1 in an amount of 1% by weight, based on the filter cake. The data obtained analogously to Example 1 are shown in Tables 1 and 2.

Comparative Example 1:

1.05 kg of an alkali metal aluminum silicate filter cake (Sasil ^R ), from the applicant's current production, with a content of 48.3% by weight of alkali metal aluminum silicate (free Na ₂ 0 = 0.57% by weight) were analogous Example 1 with 0.5% by weight, based on the filter cake of the layered silicate 2, was added and stored. The data obtained are shown in Tables 1 and 2.

Comparative Example 2:

0.997 kg of the filter cake according to Comparative Example 1 were treated with the layered silicate 2 in an amount of 1% by weight, based on the filter cake, analogously to Comparative Example 1 and stored. The data obtained are shown in Tables 1 and 2. Comparative Example 3:

1.879 kg of a filter cake according to Example 1 were mixed and stored analogously to Example 1 with tallow fatty alcohol 5E0 in an amount of 1.5% by weight, based on the filter cake. The data obtained are shown in Tables 1 and 2.

Comparative Example 4:

1.1 kg of the filter cake according to Comparative Example 1 were mixed analogously with tallow fatty alcohol 5E0 in an amount of 1.5% by weight, based on the filter cake, and stored. The data obtained are shown in Tables 1 and 2.

The comparison of Examples 1 and 2 with the comparative examples in the following sections sediment and separation requires consideration of the different content of alkali metal aluminum silicate in the starting filter cake, 49.8% by weight alkali metal aluminum silicate in Examples 1 and 2 and comparative examples 3 and 4, compared to 48 , 3% by weight in Comparative Examples 1 and 2.

Comparative examples 3 and 4, which each contain the same type and amount of stabilizer (not according to the invention) with a different content of alkali metal aluminum silicate, made it clear that an increase in the concentration of alkali metal aluminum silicate involves difficulties in stabilizing the filter cake.

Sediment:

To determine the sediment, a 200 ml beaker with a screw cap was filled with the suspensions obtained. The amount of alkali metal aluminum silicate deposited and hardened on the bottom was assessed. In the time intervals specified in Table 1, a spatula was slowly lowered into the substance to be checked and the thickness, ie the amount of the hardened alkali metal aluminum silicate, was determined by light pressure. The grading was based on the following criteria:

0 = no sediment / homogeneous

1 = hardly any sediment

2 = very low

3 = low

4 = medium

5 = strong

6 = very strong

7 = completely

Table 1: sediment

1st day 2nd day 3rd day 7th day

Example No .: 48 ° C RT 48 ° C RT 48 ° C RT 48 ° C RT

1 0 0 0 0 0 0 0 0

2 0 0 0 0 0 0 0 0

See l 2 2 3 3 3 3 6 5

See 2 2 2 4 3 4 3 5 3

See 3 2 1 2 1 2 1 5 2

See 4 1 1 2 1 2 1 5 3

Separation:

The separation of the water from the solid was checked. To measure the separation, the substance is poured into a 100 ml standing cylinder and closed with a stopper, if necessary filled up to the 100 ml calibration mark. Difficulties sometimes arise when filling the cylinders with the viscous substances (air bubbles in the vessel, inaccurate calibration mark due to smearing on the edges).

The grading was based on the following criteria: 1 to 5 ml of water above the solid = weakly separated 5 to 10 ml of water above the solid = medium-strong separation 10 to 15 ml of water above the solid = strongly separated Table 2: Separation

l.Taq 2nd day 3rd day 7th day

Example No .: 48 ° C RT 48 ° C RT 48 ° C RT 48 ° C RT

1 1-5 1-5 1-5 1-5 1-5 1-5 1-5 1-5

2 O O O O O O O O See l 1-5 1-5 1-5 1-5 1-5 1-5 7 4 Compare 2 1-5 1-5 1-5 1-5 6 1-5 8 4 Compare 3 0 0 0 0 1 -5 0 1-5 0 See 4 0 0 0 0 1 0 1 0

Example 3:

An alkali metal aluminum silicate filter cake (Sasil ^R ) from the applicant's current production with a content of 49.3% by weight of alkali metal aluminum silicate (free Na ₂ 0 = 0.12% by weight) was mixed with 0.6% by weight .-% of the layered silicate 1 added in the form of a dry powder.

The suspension obtained in this way was stored for 2 weeks at room temperature and then the concentration of silicate was determined to be 49.8% by weight. In addition, it was found that the calcium binding capacity remains unchanged at 161 mg CaO / g atro.

Example 4:

Analogously to Example 3, the filter cake mentioned in this example was produced with the layered silicate 1 in the form of a dilute suspension, the amount of layered silicate 1 being set such that it corresponded to that of Example 3.

By combining 1 part by weight of layered silicate 1 with 10 parts by weight of fully demineralized water at a temperature of 50 to 80 ° C. the above-mentioned suspension of the layered silicate, ie a firm, cut-resistant gel of gray-brown color, was produced with stirring.

After two weeks of storage of the alkali metal aluminum silicate filter cake containing the layer silicate 1, it was found that the calcium binding capacity was reduced only from 164 mg CaO / g dry to 161 mg CaO / g dry. The concentration of silicate was determined here to be 47.6% by weight.

The layered silicate can be introduced in the form of an aqueous suspension in a technically simple manner. However, in this procedure additional water was introduced into the system, which ultimately reduced the concentration of alkali metal aluminum silicate.

Claims

Patent claims

1. Process for stabilizing pumpable suspensions of very fine zeolitic alkali metal aluminum silicates of the general formula (I),

xMe ₂ 0 • A1 0 ₃ ^• ySi0 ₂ ^• 2H 0 (I)

in the Me sodium and / or potassium, x a number in the range from 0.8 to 1.3, y a number in the range from 1.3 to 10 and z a number in the range from 0 to 6

means with a swellable water-insoluble layered silicate, characterized in that the layered silicate has a swelling volume in the range from 30 to 80 ml per 2 g of layered silicate.

2. The method according to claim 1, characterized in that one uses Suspen¬ sions containing 40 to 60 wt .-%, in particular 45 to 55 wt .-% and particularly advantageously by 50 wt .-% alkali metal aluminum silicates.

3. The method according to claim 1 or 2, characterized in that one uses suspensions which have a pH in the range from 7 to 12 sen.

4. The method according to 1 or more of claims to 3, characterized gekenn¬ characterized in that swellable, water-insoluble phyllosilicates are used which satisfy the general formula (II),

(Me ' ₂ 0) _a ^• (Me "0) _b ^• Me ₂ '" 0 ₃ ^• (Si0 ₂ ) _c (II)

where the symbols have the following meaning: Me '= sodium and potassium (where the ratio

Na ₂ 0: K ₂ 0, preferably 10 to 100: 1), Me "= magnesium and calcium (where the

MgO: CaO ratio, preferably

0.5 to 3: 1), Me '"= aluminum and iron, the

Ratio A1 ₂ 0 ₃ : Fe ₂ 0 ₃ , preferably 3 to 6: 1, a = 1.5 to 6, preferably 3 to 5 b = 0.2 to 1, preferably 0.3 to 0.5 and c ^~ 6.2 to 8, preferably 7.5 to 8.

5. The method according to claim 4, characterized in that one uses Schichtsi¬ likate with a swelling volume of 50 to 70 ml per 2 g of sheet silicate.

6. The method according to one or more of claims 1 to 5, characterized in that the alkali metal aluminum silicate suspensions 0.1 to 2 wt .-%, in particular 0.2 to 1 wt .-% layered silicate, based on the suspension, contain.

7. The method according to one or more of claims 1 to 6, characterized ge indicates that the sheet silicates are introduced in finely crystalline powder form or as an aqueous suspension in the alkali metal aluminum silicate suspension.

8. The method according to claim 7, characterized in that one uses layered silicates in the form of highly concentrated, pre-swollen aqueous suspensions.

9. The method according to claim 7, characterized in that sheet silicates are used in fine crystalline powder form, which are fluidized by known additives.

10. The method according to one or more of claims 1 to 9, characterized ge indicates that further dispersants are used which are selected from an organic, macromolecular carboxyl and / or hydroxyl group-containing polymer compound, a phosphonic acid, which has at least one further Phosphonic acid and / or carboxyl group, a phosphoric acid alkyl ester emulsifier with 3 to 20 carbon atoms in the alkyl chain, a surfactant that has a cloud point determined in water according to DIN 53917 below 90 ° C, a surface-active sulfonate and a swellable, water-insoluble silicate with layer structure.

11. The method according to claim 10, characterized in that one uses the Wei¬ tere dispersants in an amount of 0.1 to 3 wt .-%, based on the alkali metal aluminum silicate suspension.