DE2738085A1 - PROCESS FOR IMPROVING THE PROPERTIES OF SODIUM ALUMINUM SILICATE POWDER AND POWDER - Google Patents

Description

Kali-Chemie Aktiengesellschaft 3000 Hanover

Process for improving the properties of sodium aluminum silicate doughs and powders

Z1-PA / MH / Ka
August 23, 1977

909810/0127

Process for improving the properties of sodium aluminum silicate doughs and powders

The production of aluminum silicates of the zeolite types, including type A, by reacting an aqueous alkali silicate solution with an alkali aluminate solution has been known for years.

More recently, zeolite A has opened up further areas of application, e.g. as a builder in detergents. This new application entails additional requirements with regard to the Properties of the product. In addition to a high alkaline earth binding capacity, high degree of whiteness e.g. a small mean particle diameter with a narrow grain spectrum at the same time. An important requirement here is that the product, no matter what form it is in, when dispersed in water the original distribution again shows that it does not have any irreversible agglomeration.

In addition, it is expected that the sodium aluminum silicate in the form of the filter paste, which as such in the manufacture of Detergents can be used, has certain properties explained in more detail below.

The filter dough obtained during the production of the sodium aluminum silicate after the separation of the mother liquor and the washing, which as a rule contains 40-50% solids, shows, along with other theological anomalies, a high level of structural viscosity. This makes it possible in general to convey the dough in the further operation without diluting it by pumping. Furthermore, the part can be due to the mentioned rheo-

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Logical properties are generally stored in suitable containers and from there after using relatively little energy be brought to flow again by stirring, shaking or suction.

The term "in general" is intended to mean that the flow properties described in the vast majority of Cases are encountered. For the pumpability of the dough after storage, this applies in particular for a period of up to 48 Hours of storage. When stored for a long time, however, a tough sediment gradually appears, which neither pumps nor stirs leaves.

It has therefore been proposed in DOS 25 27 388 to improve the suspension stability and pumpability To add a dispersant, i.e. mainly organic surface-active substances, to sodium aluminum silicate suspensions or swellable clays, such as bentonite, etc. As the experiments given in the DOS show, organic surface surface active substances stabilized suspensions after 24 Still pumpable for hours and largely homogeneous. However, our own tests have shown that a Sediment forms and after three days the suspension can no longer be pumped. About the stability of mixed with bentonites Suspensions is not said in the DOS. Prepared clays also have the disadvantage that they are very carefully prepared from Iron must be freed and interfere with the washing process insofar as it is not completely removed during rinsing, so that it comes to deposits on the fiber until finally an encrustation occurs.

It has now been found that if sodium sulfate is present in the dough, the described difficulties in its further processing are fixed. The addition of sodium sulfate not only has the advantage that it is an inexpensive ingredient is introduced into the sodium aluminum silicate suspension, which is already present in the detergent, it also causes

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nor that when the dried product is dispersed in water, the sodium aluminum silicate is restored to its original state Grain distribution is present.

Spray drying is normally used as an expedient form of further processing of the sodium aluminum silicate dough. In addition to significant advantages over other types of drying, spray drying has a disadvantage: the product is obtained in the form of prills. However, this property, which is desirable per se, means that when dispersing in water, the particle size distribution originally given in the dough is not restored with sufficient certainty. The prills (30 - 80 μ mean diameter) often do not completely disintegrate again into the original primary particles with a fineness of approx. 98 - 99 % <15 μ, corresponding to 95 % <10 ^ u. This phenomenon is remedied by adding sodium sulfate.

It was not expected that sodium sulfate would have such a beneficial effect on the properties of sodium aluminum silicate suspensions would affect. DOS 25 27 388 shows that sodium sulfate has no stabilizing effect on the suspension have. It is pointed out that the sodium hydroxide still present in the washed filter paste is increased by sulfuric acid neutralize, but the suspension must also have the necessary stability to achieve the desired degree of stability Amount of dispersant to be added. It is recommended that the sodium hydroxide solution be at least partially neutralized with a dispersing agent with acidic character, in order to avoid non-stabilizing acids such as sulfuric acid to replace.

With the addition of sodium sulfate, the filter paste retained its. advantageous consistency, if necessary over the whole Observation period of eight weeks. In particular, no tough, non-pumpable, non-stirrable occurred

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be introduced that the sodium hydroxide, which is in Wash water, which is expediently conducted in countercurrent, is completely or partially neutralized with sulfuric acid. However As a rule, the amount of sodium sulphate introduced in this way is sufficient to improve the properties of Sodium aluminum silicate cores and powders do not work out and an additional addition of sodium sulphate is required. Also because The exact dosage of the sodium sulphate usually requires a further addition.

example 1

4.46 m sodium aluminate having the molar composition Na ₂ 0 / AI ₂ 0 = 6.2 and H ₂ 0 / Na ₂ 0 = 28 were added while stirring rapidly with 0.54 cbm simultaneously tapering sodium silicate solution having the molar composition Na ₂ 0 / Si0 ₂ = 0.83 and H ₂ 0 / Na ₂ 0 = 13.4 mixed. The mixture was stirred for 100 minutes at 90 ^° C., cooled rapidly, filtered and washed to pH 10.5. The filter paste contained 40.2 % solids.

Part of the filter paste remained in a 200 liter vessel (filling height 60 cm) without any additive. After 24 hours the dough was still flowable, as was evident when the vessel was slowly tilted by 45 °. With a stick slowly inserted vertically (Diameter: 25 mm, flat end) no inhomogeneity in the texture of the dough could be determined.

After 48 hours, a 1 cm high clear layer was visible over the dough. However, the dough was still flowable. With the vertical When the stick was inserted, a body was found about 2 cm high, which was tougher than the rest of the dough.

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After 72 hours there was an 8 cm high, clear protruding layer Above the dough and also an approx. 8 cm thick layer of soil that was tougher than the dough. The dough wasn't more fluid.

After one week, the clear, protruding layer had grown to 28 cm. When the vessel was tilted 135 °, the upper one ran Half of the dough immediately into a template, the mass of the bottom layer followed within 2 hours except for an approx. 1 cm thick residue adhering to the ground.

Homogenized by the shaking and by two hours dough flowable again made with a residual water content of 19 "6%, a sample in a laboratory dried (outlet temperature 11O ⁰ C).

The particle size distribution was carried out after dispersing in water (10 g of product; 700 ml of H ₂ O; 60 min. Stirring at 1000 rpm) by the Andreasen method.

The results are compiled in Table 1 below.

Table 1

Grain size after spray drying straight from filter dough <15 / u
<10 / i
<1 Λ ¹ 81%
73 96
5 96 99 %
96 - 97 96
2 96 50 £ 96 5.5 / 1 2.8 / i

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The comparison of the dispersed sample from the spray drying with a non-dried sample shows the unsatisfactory one Dispersibility of the dried product. The comparison sample from the dough meets the requirements of the detergent industry .

Example 2

In another part of the part prepared according to Example 1, 10 g of solid Na ₂ SO / per 1 kg of dough, corresponding to 2.4% of the amount of solid then present in the dough, were mixed in after washing out. The dough was also placed in a 200 l container up to a level of 60 cm and observed as in Example 1. The simple tests, slowly tilting the container by 45 °, inserting the stick, showed that after 7 days the dough was still homogeneous. Then gradually began to show the phenomena that occurred with a dough without the addition of _{Na 2 SO 4.}

Example 3

45 g of solid sodium sulfate per 1 kg of dough were mixed into a further part of the dough prepared according to Example 1, which corresponded to about 10 % of the amount of solids now present. As described in the preceding examples, the dough was observed when it was stored in a 200 l vessel (60 cm filling height).

The tests described above showed that settling began only after about 4 weeks in the sense of the formation of a clear protruding layer and a denser soil body. However, this sediment flowed even after 8 weeks of storage on an incline of the vessel by 135 ° practically quantitatively immediately with the

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Main mass into the template without stirring was necessary.

Example 4

In a further part of the dough prepared according to Example 1, 10Og solid Na ₂ SO ^ per 1 kg dough was mixed, which corresponded to about 20 96 of the total amount of solid. The dough was observed when stored in the 200 liter jar with a filling height of 60 cm. In terms of flowability, the dough showed the same behavior as that in Example 3.

After a standing time of 4 weeks, a sample of the homogenized dough was dried in a laboratory spray dryer. The particle size distributions after dispersion in water were determined according to Andreasen of the dried product and directly from the dough without Na _{2 SO ^ addition.} The influence of sodium sulfate on the density and viscosity of the aqueous medium was taken into account. The results are shown in Table 2.

Table 2

Grain size after spray drying straight from dough <15 / i
<10yU
<1A ¹ 97 96
96 %
2 96 98 %
96 56
2 96 50 £ 96 2.8 / u 2.8 / 1

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It can be seen from the table that the dried product practically reverts to its original state when dispersed in water Primary particle decays.

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Claims (5)

2733035 claims 1. A method for improving the properties of sodium aluminum silicate doughs and powders, characterized in that 1 - 25 % Na ₂ SO ^, based on the total _{solid present after the addition of the Na 2} SO ^, are added to the dough. 2. A method for improving the rheological properties of a sodium aluminum silicate dough according to claim 1, characterized in that 2 - 10 % sodium sulfate, based on the total solid present, are added to the dough. 3. A process for improving the dispersibility of sodium aluminum silicate powders, characterized in that 15-20% sodium sulfate is added to the sodium aluminum silicate during its production before drying. 4. Process according to claims 1 and 2, characterized in that the sodium sulfate is either one or both reaction solutions is added before the precipitation of the sodium aluminum silicate or the washed filter paste. 5. The method according to claims 1-3, characterized in that the sodium sulfate at least partially through use of washing water neutralized with sulfuric acid during the washing process of the precipitated sodium aluminum silicate is introduced. -3- 909810/0127 ORIGINAL INSPECTED