WO1992004398A1

WO1992004398A1 - Granular agglomerate and process for its manufacture

Info

Publication number: WO1992004398A1
Application number: PCT/EP1991/001574
Authority: WO
Inventors: Peter Koepff; Helmuth Stahl; Eberhard Dick; Brigitte Uhe; Klaus BRÄUMER
Original assignee: Deutsche Gelatine-Fabriken Stoess Ag
Priority date: 1990-09-03
Filing date: 1991-08-20
Publication date: 1992-03-19
Also published as: DE4027887C2; DE4027887A1

Abstract

Described is a granular agglomerate consisting of dispersed particles of at least one solid and a binder holding the particles together in the agglomerate, pores remaining open between the particles. The agglomerate has the following characteristics: the binder is hydrous gelatine; the gelatine content, expressed as a percentage by volume, is lower than the pore content so that the gelatine does not completely fill the pores; and the amount of water contained, originating from the water content of the gelatine, is less than 2 % by wt. of the total weight of the agglomerate. The agglomerate is produced in an extruder, in particular a screw-feed extruder, to which the required amounts of gelatine and solids are supplied. A highly viscous composition is extruded as a continuous extrusion, dried to the required low water content and the extrusion granulated to give a granular agglomerate.

Description

Granular agglomerate and process for its production

The invention relates to a method according to the preamble of patent claim 1.

Such a method is known from JP 59-042 846 A (Derating Section No. 84-097 618/16).

However, no extruder is used here, in which a low-viscosity gelatin solution is first produced, with which the disperse particles are then coated immediately and also in the extruder.

It is an object of the invention to improve a generic method in such a way that the agglomerate can be produced quickly and easily.

The object is achieved by the characterizing features of claim 1.

It is unusual to produce a low-viscosity solution directly in an extruder. Normally, only highly viscous masses are processed in an extruder. It is also unusual to coat and agglomerate the particles to be agglomerated with this solution directly in the extruder in which the low-viscosity solution is produced. The following description of preferred embodiments of the invention serves in connection with some examples and a drawing for further explanation. Show on the drawing:

Figures 1 and 2 schematically examples of the inner

Structure of an agglomerate according to the invention.

The agglomerate according to the invention is not thermoplastic and contains water-containing gelatin as a binder, which firmly binds the individual solid particles to one another. It is important to use the smallest possible amount of gelatin so that the properties of the gelatin do not adversely affect the properties of the solid particles which are in the foreground. The binding capacity is still sufficient if the vol .-% of gelatin is smaller than the vol .-% of pores in the agglomerate grains, so that the gelatin does not completely fill the pores. Furthermore, the amount of water attributable to the gelatin contained in the granular agglomerate should correspond to the natural water content of gelatin. This depends on the prevailing air humidity ("equilibrium moisture"). It is usually between about 10 and 12% by weight, but can be up to about 16% by weight at high atmospheric humidity.

The rheological properties of the agglomerates correspond to those of the starting materials. This means that in the case of non-thermoplastic solid starting materials, the agglomerates produced therefrom also have these properties to have .

It is advantageous with the agglomerate according to the invention that it allows rapid dispersion and dissolution, for example in the case of so-called “instant products”, that separation processes, for example in the case of agglomerated medicines and animal feed, can be avoided and that appropriate additives can also be used in the Agglomera¬ tion can achieve a depot effect, especially with fertilizers and pesticides.

The granular agglomerates according to the invention are particularly advantageously produced with the aid of extruders, in particular screw extruders, in a single work cycle.

The ability of the gelatin to dissolve in water is used. Any viscosity can be set by means of temperature and amount of solvent. Solvents other than water are also suitable, for example glycerol or mixtures of glycerol and water.

The extruders used to produce the agglomerate according to the invention are preferably co-rotating twin-screw extruders with a relatively long process length. The long process length of the twin-screw extruder is necessary because all of the work processes essential for the production of the agglomerate take place in the extruder: the binder (gelatin, gelatin hydrolyzate or a mixture of gelatin and gelatin hydrolyzate) is dissolved in the solvent, heated, Additives are added that become agglomerating substances added and incorporated homogeneously.

A twin screw extruder is advantageous because it can be used to achieve particularly good homogenization. Homogenization is achieved on the one hand by kneading in the gap between the two screws and the use of special mixing parts, on the other hand, with the double screws rotating in the same direction, no complete chamber shut-off is achieved, so that the mass can flow back around the two screws . Both effects guarantee a sufficient mixing of the binder with the solvent and incorporation of the solid particles and homogenization of the highly viscous pseudoplastic mass to be extruded.

In a first area of the screw extruder, the binder, e.g. B. gelatin, added at a first metering station. The liquid solvent, eg. B. water. For example, over a length of 15 D, the mixture is mixed while continuously increasing the temperature and under increasing pressure. In an end section of this first area, which can have a length of 20 to 25 D, the gelatin is further dissolved and the solution is homogenized. ("D" is the inside diameter of the screw extruder.)

In a subsequent second area, which can have a length of 13 to 18 D, the dusty solids to be compacted are added. The addition can take place, for example, via a stuffing screw known per se. The viscosity of the mass is greatly increased by adding the substances. Depending on the particle size and amount, the viscosity can increase to a multiple of the low-viscosity gelatin solution.

This now highly viscous, "pseudoplastic" mass is pressed through a strand die and shaped as an endless strand, wherein at the same time several strands can emerge from several nozzle openings. The strands are z. B. deducted with a conveyor belt. At the same time, the strand is dried to equilibrium moisture by evaporation of the solvent, for example in a hot air stream, so that the gelatin, which is now returned to its natural water content, only fills a small volume of the pores in the interior of the agglomerate.

Due to the strong adhesive strength of the gelatin, it is achieved that with only small amounts of gelatin, after the solvent has been expelled, a strand which is still firmly connected is present. The strand is then cut to any grain size using a known granulator, so that the end product is a granular agglomerate.

FIG. 1 shows schematically a first typical form of the internal or microscopic structure of an agglomerate according to the invention. Individual particles 1 of a solid, for example a dust-like pigment, are (due to the processing described in the extruder, in particular screw extruder) essentially completely surrounded by a thin gelatin skin, which binds the individual particles firmly to one another or agglomerates due to their adhesive force. Here remain between the individual Particles 1 gelatin-free pores 3.

The agglomerate shown schematically in FIG. 2 differs from that according to FIG. 1 essentially in that the gelatin 3 contains the particles 1 - z. B. because of poor wettability - is not completely encased, but is only present in some areas on the circumference of the particles and there is an "adhesion" of the individual particles. The relative amount of gelatin is so small that the pores between the particles 1 are not completely filled with gelatin 2.

example 1

300 g / h gelatin with a water content of about 11% by weight corresponding to the equilibrium moisture content are metered continuously into a first area (feed zone) of a twin-screw extruder of 48 D. In the same area, 300 g / h of water are continuously added at another metering point via a valve. The temperature in this area rises steadily from 25 to 80 ° C. over its length.

In a subsequent area of the extruder, the temperature is increased to 95 ° C. The gelatin is completely and homogeneously dissolved in this area with the help of the double screw.

In a subsequent area, 2.7 kg / h of dust-like dye are metered in via a stuffing screw and mixed homogeneously into the gelatin solution. The now highly viscous, pseudoplastic mass is under pressure of 40 bar and at a temperature of 95 ° C extruded from a strand nozzle with four openings. The strands are dried in a stream of air during removal and then granulated.

The granular agglomerate obtained in this way is very strong and the individual grains have a smooth surface.

Example 2

The procedure is as in Example 1. However, 500 g / h of gelatin are metered in and 250 g / h of water are added via a valve. 2 kg / h of sugar are fed in via a stuffing screw. The pseudoplastic mass obtained in this way is extruded at a pressure of 20 bar. The extruded strands are dried and granulated into a granular agglomerate. The agglomerate is suitable, for example, as a compound for use in the confectionery industry.

Example 3

The procedure is as in Example 1. However, 250 g / h of gelatin hydrolyzate are used when the same amount of water is added. 2 kg / h of a mixture of sugar, citric acid, yellow and red color and orange aroma are added via the stuffing screw. There is no separation of the individual components, but rather a granular agglomerate of these components results, which can be fed to further processing in the confectionery industry. Example 4

The procedure is as in Example 2. However, 125 g / h gelatin hydrolyzate and 125 g / h gelatin are used. The water addition is unchanged. 250 g / h of herbicides are then continuously mixed into the solution thus obtained.

Additives, in particular plasticizers, emulsifiers, wetting agents and / or non-stick agents, can be added to the gelatin fed into the screw extruder in a known manner. Suitable plasticizers are, for example, glycerol or sorbitol, for example amine oxide or Na lauryl sulfate are suitable as wetting agents. Mg stearate or montan waxes have proven to be useful as anti-adhesive agents.

In general, the amount of water in which the gelatin is dissolved can be between 50 and 300% by weight based on the weight of the gelatin. The screw extruder is operated at temperatures between 30 and 140 ° C., preferably at temperatures between 30 and 100 ° C. The increased pressure prevailing in the extruder can be between 5 and 100 bar.

Claims

P a t e n t a n s r u c h e

Process for producing a granular agglomerate consisting of disperse particles of at least one solid and of these particles agglomerating gelatin, wherein pores remain free between the particles, characterized by the following steps:

A. In a first area of an extruder, in particular a screw extruder, a low-viscosity gelatin solution is produced by heating by continuously adding gelatin and solvent, in particular water;

B. at least one solid to be agglomerated is introduced into the low-viscosity gelatin solution in a subsequent area of the extruder with continued heating, and a highly viscous pseudoplastic mass is produced by homogeneously mixing the solid with the solution and under pressure;

C. this highly viscous pseudoplastic mass is extruded from the extruder through a nozzle in the form of a strand;

D. the strand is pre-dried and granulated into the granular agglomerate and E. Finally, the granules are dried to equilibrium moisture.

2. The method according to claim 1, characterized in that the gelatin is replaced by gelatin hydrolyzate or a mixture of gelatin and gelatin hydrolyzate.

3. The method according to claim 1, characterized in that the gelatin is mixed with plasticizers, emulsifiers, wetting agents and / or non-stick agents.

4. The method according to claim 1, characterized in that with respect to the gelatin between 50 and 300 wt .-% of water as a solvent is added.

5. The method according to claim 1, characterized in that one carries out the dissolving and mixing in the extruder at temperatures between 30 and 100 ° C.

6. The method according to claim 1, characterized in that one carries out the dissolving and mixing in the extruder at pressures between 5 and 100 bar.

7. The method according to claim 1, characterized in that the strand is dried in an air stream.