Device for the production of fine dispersions and for redispersing dispersions with sediment formation

Abstract

Device (10) for producing fine dispersions and for redispersing dispersions with already begun sediment formation according to the rotor / stator principle, characterized in that the device (10) has rotor / stator pairs (6, 7) in the form of concentrically interlocking ring pairs with through openings (8) instead of toothed rings 1 to 3.

Description

[0001] The present invention relates to a method and a device for producing fine dispersions and for redispersing dispersions in which sediment formation has already begun.

[0002] Dispersed preparations, or dispersions in general, play a vital role in many areas of technology in the form of emulsions or suspensions, such as in the food, pharmaceutical and cosmetics industries, or also in paints and varnishes.

[0003] Emulsions and suspensions produced using methods known in the prior art often have the disadvantage that the emulsified or suspended components have excessively large and uneven particle sizes and are therefore not homogeneously distributed within the emulsion. This can lead to sediment formation in dispersions, which can render the dispersion unusable if sufficient redispersion is not possible.

[0004] Since the emulsified or suspended particles of an emulsion often have particle sizes smaller than 0.001 mm, or should have such a size for optimal use, the known methods for producing dispersions are often insufficient. For example, paint or varnish spraying systems, where the spray cans contain metal balls to redisperse sediments that form during extended storage, can be cited as an example.

[0005] In the prior art, so-called gear-ring dispersing machines and associated methods are generally used for the purposes of the invention, as described, for example, in WO 00 / 01474 and DE 3319921 A1. These are rotor / stator dispersing machines that have interlocking gear rings in the rotor and stator sections. The gap volume, which is determined by the gap length and width between the rotor and stator gear rings and the rotor circumference, has a decisive influence on the achieved dispersion fineness. To produce the finest possible dispersions, the rotor speed would have to be increased. However, this is generally not technically feasible, as the maximum rotor speed is often only slightly above the normal operating speed.

[0006] The disadvantages of the prior art methods and devices for producing dispersions mentioned above should be avoided or at least minimized by the present invention. Furthermore, a corresponding device should be as simple and inexpensive to manufacture as possible.

[0007] The invention was therefore based on the objective of providing a method and / or a device with which dispersions (emulsions and suspensions) that are as stable as possible and thus storable for extended periods without sediment formation can be produced. This applies particularly with regard to the production of very finely divided emulsions and suspensions. Furthermore, the invention should eliminate the need for the addition of surfactants (so-called stabilizers) known in the prior art for the production of storage-stable dispersions.

[0008] Furthermore, methods and devices should also be suitable for the storage-stable redispersion of dispersions with sediment formation.

[0009] In prior art gear-type dispersing machines operating on the rotor / stator principle, several rotor / stator disks (preferably three disks) are typically arranged, with each disk usually having two or three concentric gear rings. The dispersion is accelerated to circumferential speeds of 20 to 30 m / s in the gear ring gaps of the rotor, resulting in turbulent flow in the gap between the rotor and stator gear rings. Dispersion takes place in the radially successive gear ring pairs, with the inner pairs serving for pre-dispersion and the outer pairs for fine dispersion. Typically, several dispersion stages of this type are axially connected in series within a single machine.

[0010] The invention provides a technically simple dispersing machine or device for the production of particularly fine dispersions (emulsions and suspensions) or for the reconstitution of dispersions in which sediment formation is imminent or has already begun. The device according to the invention is also based on the rotor / stator principle. However, the toothed rings for generating the share gaps are replaced by concentric solid rings, which have through-openings that can have various geometries, sizes, and arrangements.

[0011] A dispersion stage or device, which, as in gear-type dispersion machines, can be axially connected in series (preferably 2 to 4 of these dispersion stages), preferably has 1 to 3 such rings on the rotor and on the stator, which are arranged concentrically and interlocking. Preferably, a ring with the smallest diameter is provided concentrically to the center of the rotor. This is followed by a stator ring (concentric with a larger diameter) and then another ring arranged on the rotor with an even larger diameter, and so on. The device (a dispersion stage) has at least one such rotor / stator ring pair, wherein the outermost stator ring can also be formed by the outer wall (the housing) of the device. The outer stator ring always has at least one, preferably one, opening of a larger diameter through which the formed or reconstituted dispersion can exit the device / dispersion stage.

[0012] The through-holes in the rotor and stator rings can, in principle, assume any geometric shape. Examples include round, oblong, or oval holes, or holes with a rectangular, square, or triangular cross-section. The holes can be cylindrical or conical, for example. Furthermore, the holes in the rotor rings (moving rings) and the stator rings do not need to have the same geometry or size (e.g., 8 mm diameter in the rotor rings and 4 mm in the stator rings, or vice versa). The possible arrangements of the through-holes or holes (both terms are used synonymously for the purposes of this invention) are also not limited (e.g., wave-shaped arrangements, spiral arrangements, vertically stacked in a ring, etc.). The same applies to the hole spacing and hole sizes. These features can also vary from ring to ring (whether rotor or stator).

[0013] For the reconstitution of dispersions in which sediment formation has already occurred or is imminent, a container in which the dispersion is initially placed is connected to the device according to the invention via a pump, and the dispersion is applied directly to the rotor via the device's central inlet. The finished, homogenized dispersion exits the device via a drain on the side wall. To ensure simple and complete introduction of the dispersion with sediment into the device, it is advantageous for the supply container to be equipped with an agitator so that the sediment settling in the container can be broken up and pumped into the device without problems.

[0014] Dispersions reconstituted in this way usually remain stable for months without forming a new sediment.

[0015] For the production of suspensions or emulsions, the starting components, in liquid or slurry form, can be fed onto the rotor via two or more separate inlets and homogenized. The finished dispersion exits the device according to the invention via the lateral outlet. Preferably, the device according to the invention has two inlets.

[0016] Alternatively, to produce a dispersion (suspension, emulsion), the two or more pumped material streams of the starting components can first be mixed to form a so-called pre-dispersion, which is then fed directly onto the rotor for fine dispersion in the device, e.g. via a temperature-controlled intermediate volume.

[0017] The materials used to manufacture the device according to the invention are generally determined by the mechanical stresses that occur and the chemical properties of the dispersions to be produced. These are usually, for example, stainless steel for the housing and also the rotor and stator, or brass for the rotor and / or stator rings.

[0018] The invention offers, among other things, the following advantages: The device according to the invention makes it possible to produce stable and finely divided dispersions over long periods of time (e.g. over several months), which are not or hardly possible with conventional rotor / stator machines.

[0019] The energy input is reduced in the device according to the invention compared to known gear-ring dispersion machines, which can, for example, reduce the thermal stress on finely divided and temperature-sensitive dispersions.

[0020] Furthermore, the device or dispersing machine according to the invention is technically less complex and less expensive to manufacture than gear-type dispersing machines currently on the market. This is due, among other things, to the elimination of the technically complex gear rings for the rotor and stator.

[0021] The present invention will now be explained in more detail with reference to a drawing and an exemplary embodiment. It shows: Fig. 1 a schematic representation of the device according to the invention with two inlets

[0022] The Fig. Figure 1 shows a device 10 for producing fine dispersions and for redispersing dispersions with already begun sediment formation according to the rotor / stator principle with rotors 6 and stators 7, which are arranged alternately to each other.

[0023] A commercial paint dispersion, in which sedimentation has already begun, is redispersed using the device 10 according to the invention (hole diameter in rotor and stator rings 4 mm; 3 stator and 3 rotor rings). The resulting dispersion shows no sedimentation over a period of several months.

[0024] The device 10 does not have toothed rings, as in the prior art, but rather rotor / stator pairs 6, 7 in the form of concentrically interlocking ring pairs. The rotors 6 rotate about the axis of rotation 4. For synchronous movement with a drive 9, the rotors 6 can be arranged together on a plate member 5, on which the drive 9 acts.

[0025] The Fig. Figure 1 shows the drive 9 for driving the rotors 6. The rotor circumferential speed can preferably be between 20 m / s and 80 m / s.

[0026] In the present case, the outermost stator ring is formed by the housing of the device 10, which also has the outlet 2 of the device 10 for the finished dispersion.

[0027] Again Fig. As can be seen further in Figure 1, the device 10 preferably has two separate inlets 1 for introducing the substances to be dispersed into a mixing chamber 3 of the device, wherein the material streams to be dispersed are fed directly onto the rotor 6. The finished dispersion is discharged from the device 10 through the outlet 2.

[0028] For the production of dispersions and for the redispersion of dispersions, through-openings 8 are provided in the rotor 6 or stator 7 or in the rotor and stator rings 6, 7.

[0029] These through-openings 8 of the rotor and stator rings 6, 7 can have the same or different diameters and the same or different arrangements on the rings 6, 7.

[0030] The through-holes 8 can be in the form of cylindrical or conical holes and preferably have a maximum diameter of 4 to 8 mm.

[0031] In this case, several through holes 8 are arranged around the circumference of the rotor 6 or stator 7 and / or one above the other and / or next to each other on the rotor 6 and / or on the stator 7.

[0032] It is also conceivable that the number of through holes 8 differs between at least one adjacent rotor 6 and stator 7.

[0033] In one embodiment, the arrangement of the through holes 8 in the rotors 6 and stators 7 in the flow direction of the mixture in the device 10 can be spiral or wave-shaped.

[0034] The through holes 8 can have a round, oval, rectangular, triangular or square cross-section, or be designed as an oblong hole or conical and / or stepped.

[0035] The inlets 1 of the device 10 can be connected to a container with a stirrer in which a pre-dispersion is produced from the starting materials to be dispersed. Reference symbol list 1 Inlet 2 Procedure 3 Mixing room 4 axis of rotation 5 plate element 6 Rotor 7 Stator 8 through openings 9 Drive 10 Device QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 00 / 01474

[0005] DE 3319921 A1

[0005]

Claims

[1] Device (10) for producing fine-particle dispersions and for redispersing dispersions with already initiated sediment formation according to the rotor / stator principle, characterized by that the device (10) has 1 to 3 rotor / stator pairs (6, 7) in the form of concentrically intermeshing ring pairs with through openings (8) instead of gear rings. [2] Device (10) according to claim 1, characterized by that the device (10) has two separate inlets (1) and one outlet (2), wherein the inlets (1) feed the material flows to be dispersed directly onto the rotor (6). [3] Device (10) according to claim 1 or 2, characterized by that the through openings (8) of the rotor and stator rings (6, 7) have the same or different diameters and the same or different arrangements on the rings (6, 7). [4] Device (10) according to one of claims 1 to 3, characterized bythat the through openings (8) have the shape of cylindrical or conical holes. [5] Device (10) according to one of claims 1 to 4, characterized by that the through openings (8) have a largest diameter of 4 to 8 mm. [6] Device (10) according to one of the preceding claims, characterized by that several through holes (8) are arranged over the circumference of the rotor (6) or stator (7) and / or one above the other and / or next to each other on the rotor (6) and / or on the stator (7). [7] Device (10) according to one of the preceding claims, characterized by that the number of through holes (8) differs between at least one adjacent rotor (6) and stator (7). [8] Device (10) according to one of the preceding claims, characterized by that the arrangement of the through holes (8) in the rotors (6) and stators (7) is spiral or wave-shaped in the flow direction of the substance mixture in the device (10). [9] Device (10) according to one of the preceding claims, characterized by that the device (10) is provided with a drive (9) which generates a rotational speed corresponding to a rotor peripheral speed of 20 m / s to 80 m / s. [10] Device (10) according to one of the preceding claims, characterized by that the inlets (1) of the device (10) are connected to a container with a stirrer in which a pre-dispersion is produced from the starting materials to be dispersed. [11] Device (10) according to one of the preceding claims, characterized by that the outermost stator ring is formed by the housing of the device (10), which also has the outlet (2) of the device (10) for the finished dispersion.

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