NL8302743A - METHOD FOR PREPARING AQUEOUS, NON-SEDIMENTING DISPERSIONS - Google Patents

Description

* —-% “'N / 31.6l5-Kp / Pf-f.

Process for the preparation of aqueous, non-sedimenting dispersions.

The invention relates to a process for the preparation of aqueous, non-sedimenting dispersions by dispersion of solid particles in water, characterized in that prior to the preparation of the dispersion in the aqueous medium or in the solid particles already containing dispersion, starch and carbamide, either separately or in the form of a previously mixed product, are distributed.

It is known that the particles of sols, which are of the order of the colloids, sediment extremely slowly, because a sedimentation equilibrium is established. The particles of the suspensions, in the coarser particle size range, sediment relatively quickly in case their density is greater than that of the medium (Erdey-Gruz. T.-Schay, Cs: Theoretical Physikalische Chemie, Tankönyvkiadd, Budapest, 1964, pp. 226-233).

When both colloids and coarser particle size ranges are present in the systems 20, the relatively larger sedimentation particles falling in the coarser particle size range catch up with the smaller particles, they can coalesce with the latter and finally the latter can collect. for small particles is not characteristic, but for high-speed polydisperse systems characteristic of so-called orthokinetic coagulation, sedimentation (Dr. BuzSgh A .: Praktikum der Kolloi-dik, Tankönyvkiadó, Budapest, 1962, p. 143-149).

In a large part of the industrial processes it is an aim to prepare good sedimenting systems, especially in the separation of substances with solid and liquid aggregate state, such as, for example, in the dewatering of various sludges or in the formation of leaves in the paper industry. In another part of the industrial processes, on the other hand, the aim is to increase stability and prevent sedimentation, for example in the preparation of drilling sludge for petroleum extraction / in the preparation of various emulsions or when the transport or storage of dispersions is specified. Typical examples of this are the preparation of filler suspensions in the paper industry, the stabilization of paraffin, bitumen - or also various plant protection emulsions applicable for various purposes, and also the preparation of various fertilizer dispersions.

In the stabilization of suspensions, from an economic point of view today one of the most important and therefore one of the fastest developing areas is to improve the preparation of suspended fertilizer. On this basis, the principles, practice and detailed issues of stabilization with the suspended fertilizer are presented as an example.

The storage and transport of the different powdered fertilizer mixtures is associated with large losses, while the unevenness in their spreading is always a disadvantage, the spreading of fertilizer mixtures of different active ingredients is only possible in a number of steps .

These problems can be avoided by suspensions prepared from fertilizer mixtures containing various active ingredients if, from the start of the preparation, via the storage, and the transport until the spreading, no disturbing sedimentation to be applied occurs.

The name of the suspended fertilizer mixes is misleading. Undoubtedly, the solid fertilizer components used for the preparation fall into the coarse dispersion range. The size and quality of the particles contained in the saturated solution of the components present a complicated picture because of the various interactions contained in the solution, double salt formation processes, particle separation, etc. The quality of the particles contained in these systems, resp. their size depending on their material quality has not yet been subjected to a detailed scientific examination; therefore, systems 40 - without particle size analysis - were called summary 8302743 * 3-persies. This definition offers space for the separate resp. common presence of particles falling both in the coloidal and in the coarse disperse size range.

In suspensions, electrolytes are usually used for stabilization against sedimentation.

These generate electrostatic repulsive forces between the particles and thus prevent their clumping.

Of course, this method cannot be used in the case of a medium of fertilizer dispersions consisting of a strong electrolyte solution.

So-called macromolecular colloids can also be used for the stabilization of the dispersions, which increase the viscosity of the medium, thereby complicating the sedimentation of particles, but also enclosing the particles as an envelope, which also prevents the ball from clumping together. To this end, gelatin, carboxymethyl cellulose, polyvinyl alcohol, casein, lignin sulfonic acid, respectively. their derivatives, sorbite, glucose etc. are used.

Synthetic silicates, various silicic acid derivatives, colloidal silicate sols, magnesium silicon silicates are proposed for stabilization of suspended fertilizer; furthermore, natural silicates are used, such as the concrete minerals, which are included in the clay minerals, illite, attapulgite, etc. Optionally, phosphate-based dispersion agents are also used in addition to the clay minerals.

In addition to the dispersing and stabilizing agents, the importance of the influence of the mechanical crushing is also emphasized. The prior art in question is, for example, in BuzSgh's Praktikum der Kolloidik (Tankönyvkiadó, Budapest, 1962, pp. 119-125, 143-149 and 176-199), further in German Patent 1,667,798 and in U.S. Patent 3,579,321.

With the methods described, a relatively good stability can be achieved, but in the systems stabilized in this way, the already sedimented components must in practice in most cases be re-homogenized by stirring from time to time.

A further problem lies in the relatively high price of industrial products caused by the 40 material and energy consumption. With the natural resp. However, the high quality effects of the various industrial by-products again hinder stabilization. The value of a process which has proved to be useful can optionally be reduced if the stabilizing agent has a chemical composition which is foreign to the base materials.

The object of the invention is to provide a method by means of which stabilization of suspensions of sufficiently constant quality and relatively inexpensive means available, which can be used without special chemical conversion, in principle does not deviate from the natural base components. made.

The invention is based on the insight that this problem can be solved with the aid of starch and urea. Quite surprisingly, it was found that the per se rapidly sedimenting starch resp. urea in water together not only does not sediment but also prevents the sedimentation of the dispersion solid particles.

This observation is even more surprising because according to the literature (Handbuch der Papierindustrie, Chief editor: György VSmos, Müszaki Könyvkiado, 25 Budapest, 1980, pp. 120-122 and 143), the starch is usually dissolved in oxidative, enzymatic, basic or acidic decomposition. can convert a non-sedimenting system and the product obtained in this way is usually not known as a stabilizing agent, but rather as a coagulation, ready or sedimentation agent.

Accordingly, according to the invention, one proceeds in such a way that prior to the preparation of the dispersion in the water or the aqueous medium or in the dispersion starch and carbamide already containing the solid particles, either separately or in the form of a mixture previously prepared dry.

The amount of starch used for stabilization is 1-50 mass percent, preferably 2-10 mass percent, based on the amount of water. The amount of carbamide is at least equal to the amount of 3302743. r> f: 5-starch, but not more than fiftyfold thereof / and preferably the 2- to 10-fold amount.

The starch can advantageously be used in undisclosed form / in the form of natural substances containing starch.

The starch and urea can preferably be used in the form of a dry mixture.

The method according to the invention provides mixtures of the most diverse material quality, which are soluble in different ways in water and which consist of inorganic and / or organic compounds, yield a non-sedimenting, well-liquid and easily shaking system. The method thus offers a better solution for various needs than the prior art: - It has been possible to stabilize suspensions with substances which are not foreign to the natural constituents of the soil and the living organisms.

The process is not limited to small groups of different materials, much more the necessary stability is ensured also when using particles of the dispersion with the most diverse chemical composition.

- In fertilizer suspensions, one stabilizing component, the urea, can be considered as a natural component of the fertilizer suspension.

25 - The method makes it possible to broaden the scope of starch, which is an important product of the industry based on agricultural production.

The process does not require the isolation of the starch from its natural appearance, since the desired effect is also obtained when ground products of varying starchy vegetable materials, for example of cereals, etc. are used.

The method according to the invention is now further elucidated on the basis of the following exemplary embodiments which show the effect to be achieved.

Comparative example I.

40 g of starch were dispersed in 500 ml of water with continuous stirring. A 250 ml sedimentation cylinder, with 2.5 ml increments in 8302743 "v -6- in the range 100 - 250 ml, was charged with the dispersion.

The volume of the sedimented substances was read after 1,2 and 24h, after which the nature of the sedimentation with the naked eye was determined after sedimentation for 24h.

Already after an hour, the sediment of the starch in the sedimentation cylinder dropped into the area under the 100 ml mark without scaling.

The sediment formed an extremely solid and very difficult to shake layer in 24 hours.

Comparative Example II.

The procedure was as described in comparative example I, with the difference, however, that in addition, 200 g of urea was dispersed with stirring. The urea dissolved during stirring, and a sedimentation test could not be performed.

Comparative Example III.

Proceed as in comparative example I, with the difference, however, that 150 g anthraquinone is dispersed instead of starch. Already after an hour, the sediment of the anthraquinone in the sedimentation cylinder dropped into the area below the 100 ml mark without scaling. The sediment formed an extremely solid and difficult to shake layer in 24 hours.

Example I.

The procedure was as in Comparative Examples 1 to 3, with the difference that 200 g of carbamide, 40 g of starch and 150 g of anthraquinone were dispersed in the 500 ml of water with stirring. After one hour, resp. no sedimentation was observed after 2 h, after 24 h a further 5 ml of clear medium could be seen above the sediment. After sedimentation for 24 hours, no sediment was formed and the dispersion remained homogeneous and easily shakable.

Comparative example IV.

35 The reference was made to comparative example II

as described, with the difference that instead of 200 g of 8302743-7 carbamide, 200 g of potassium chloride was dispersed. During stirring, only part of the potassium chloride dissolved. After pouring out the suspension formed in the saturated KCl solution, an extremely fast sedimentation system was formed. The sediment dropped already after an hour to the area below the 100ml mark without scaling. The sediment formed an extremely solid and difficult to shake layer in 24 hours.

Comparative example V.

The procedure was as described in comparative example 2, with the difference that monoammonium phosphate was dispersed. During the dispersion, part of the monoammonium phosphate dissolved. The saturated mono-ammonium phosphate suspension sedimented quickly in the sedimentation cylinder, already after 1 h the sediment sank into the area below the 100 ml mark without scaling. After 24 h, the sediment was loose, but had an extremely small volume, while shaking did not present a particular problem.

Comparative Example VI;

Proceed as described in comparative example V, except that 150 ml of 25% ammonium hydroxide was added to the suspension during the suspension. The suspension sedimented in the 250ml sedimentation cylinder slower than was observed in Comparative Example V, but nevertheless the volume of the sediment dropped to slightly below 100ml after 1 h. The sediment was relatively easy to shake after 24 hours.

Example II.

30 As described in comparative example I and.

II described, except that 500 g of water and 500 g of urea and 250 g of starch, which were previously mixed dry, were dispersed. The system so prepared had an extraordinarily high viscosity, and shaking was complicated by the viscosity. The system did not sediment even after 24 hours.

8302743 .-. -8-Example III.

The procedure was as described in Example 1, except that according to a nitrogen / phosphorus / potassium ratio of 1: 0.5: 0.5 in 650ml water, 1870g 5 urea, 40g starch, 1000 g of monoammonium phosphate, 900 g of 25% ammonium hydroxide and 880 g of potassium chloride were dispersed. The dispersion thus formed with an active substance content of 40% did not sediment in the sedimentation cylinder after 1 resp. 2 h, while after 24 h 7.5 ml of clear medium 10 had formed above the surface of the suspension. There was no sediment. The suspension was easily shaken.

Example IV.

The procedure was as described in Example III, with the difference that, in accordance with the ratio of nitrogen / phosphorus / potassium of 1: 1: 0 in 30 ml of water, 900 g of ammonium hydroxide, 720 g of urea, 1000 g of monoammonium phosphate and 40 g of starch dispersed. The dispersion thus formed, with an active substance content of 40%, did not sediment in the sedimentation agent of 240 ml within 1 or 20 ml. 2 h. After 24 h, 5 ml of clear medium had formed above the surface of the suspension. Homogenization was not necessary. A sediment did not form. The suspension was easily shaken.

Example V.

The procedure was as described in Example III, with the difference that according to the nitrogen / phosphorus /; potassium ratio of 1: 1: 1 in 710 ml of water. 900 g of ammonium hydroxide, 1000 g of monoammonium phosphate, 720 g of urea, 880 g of potassium chloride and 40 g of starch were dispersed.

The dispersion thus prepared with an active substance content of 40% did not sediment in the 250 ml sedimentation cylinder after 1 resp. 2 h. After 24 h, 10 ml of clear medium had formed above the surface of the suspension. A sediment did not form. The suspension was easily shaken.

Example VI.

The procedure was as described in Example III, with the difference that according to the nitrogen / phosphorus ratio of 1: 1: 2 in 920 ml of water 720 g urea, 1000 g monoammonium phosphate, 900 g of ammonium hydroxide, 1860 g of potassium chloride and 50 g of starch were dispersed.

The dispersion did not sediment after 1 resp. 2 h. After 24 h, 2.5 ml of clear medium had formed above the surface of the suspension. A sediment did not form. The suspension was easily shaken.

Example VII.

The procedure was as described in Example 3, with the difference that, according to the nitrogen / phosphorus / potassium ratio of 1: 2 in 3 ml of water, 300 g of ammonium hydroxide, 280 g of urea, 1000 g of monoammonium phosphate, containing 40 g of starch grain meal and 1350 g of potassium chloride were dispersed. The dispersion did not sediment in the sedimentation cylinder after 1 resp. 2 h. After 24 h, 12.5 ml of clear medium had formed above the surface of the suspension.

A sediment did not form. The suspension was easily shaken.

Example VIII.

125 g of urea, 1250 g of monoammonium phosphate, 375 g of ammonium hydroxide, 20 g of starch and 2656 g of potassium chloride were dispersed in 1750 ml of water. The dispersion 40% active substance thus formed did not sediment in the 250 ml sedimentation cylinder after 1 resp. 2 h. After 24 h, 15 ml of clear medium had formed above the surface of the suspension. A sediment did not form. The suspension was easily shaken.

8302743

Claims (3)

Process for the preparation of aqueous, non-sedimenting dispersions by dispersion of solid particles in water, characterized in that prior to the preparation of the dispersion in the water or aqueous medium or in the dispersion already containing the solid particles 1 -50 mass%, preferably 2-10 mass% starch, based on the water, as well as at least a fifty-fold, preferably a 2-10-fold amount of urea corresponding to the mass of the starch are being divided. 2. A method according to claim 1, characterized in that the starch is used in undisclosed form, in the form of starch-containing natural substances. 15 3. Process according to claim 1 or 2, characterized in that both the starch and the carbamide are used in the form of a dry mixture. / 8302743