WO2013156199A1

WO2013156199A1 - Baffle system and magnetic mixing system comprising such baffle system

Info

Publication number: WO2013156199A1
Application number: PCT/EP2013/054660
Authority: WO
Inventors: Erwin Bauters; Johan Paul
Original assignee: Strategisch Initiatief Materialen Vzw Departement Flamac
Priority date: 2012-04-16
Filing date: 2013-03-07
Publication date: 2013-10-24
Also published as: EP2653216A1

Abstract

A mixing system is disclosed, comprising • - a container (3) for receiving and containing substances; • - a magnetic stirring bar (8) positioned within a first region of the container, and an associated first magnetic driving means (5) adapted for generating a first changing magnetic field in the first region for driving a rotational movement of the magnetic stirring bar, wherein the mixing system further comprises • - a baffle system (2) arranged rotatably within the container, the baffle system comprising one or more baffles (4) or flow directing planes for directing a flow of substances within the container, the baffle system comprising at least one magnet (BM2, BM4); and • - a second magnetic driving means (6) adapted for generating a second changing magnetic field, the second changing magnetic field substantially extending into a second region of the container, the second region comprising the at least one magnet and being different from the first region, to thereby drive the at least one magnet. Said first magnetic driving means is arranged below a bottom surface of said container and said second magnetic driving means is arranged next to and adjacent to a sidewall of said container.

Description

Baffle system and magnetic mixing system comprising such baffle system.

The present invention relates to mixing systems for mixing substances in a container, more particularly magnetic mixing systems.

BACKGROUND TO THE INVENTION

Magnetic stirring for mixing of substances in a vessel or container, wherein a magnetic stirring bar is positioned at a lower region of the vessel, and wherein such stirring bar is being manipulated by a rotation magnetic field in order to have the magnetic stirring bar making a rotating movement, thereby stirring and mixing substances present in or added into the vessel, are known today. Examples of such stirring systems are disclosed in EP1816009 Bl and US4162855A.

The use of a baffle system in mixing systems for stirring and mixing substances, wherein the position of the baffle system is fixed with respect to the container, is known, as it may improve stirring and mixing performance.

For instance in US6109780A, an apparatus and method of stirring cells in liquid culture media is disclosed, wherein baffles are present along the interior wall of the container. A stirring apparatus is positioned inside the container. The liquid in the container is at a level below the top of the blades such that the blades are moved through the surface of the liquid. A magnetic bar is attached to the shaft and is driven by an external rotating magnetic bar. The mixing system of US6109780 is a dynamic vortex impeller and the baffle system has the role of causing the liquid to circulate from a position near the top of the fluid level to a position near the bottom of the fluid level. This may increase bubble and foam formation during mixing, which is often unwanted, for instance when optical characterization of the mixture is to be performed.

The use of fixed baffles has the disadvantage that regions with less or no fluid flow are created in regions adjacent to the baffle structures, especially near the inner sidewall of the container, which may negatively influence the stirring and/or mixing process. Also, i n such regions, substances more easily attach themselves better to the container or baffles. Moreover cleaning of containers after use becomes more difficult. For instance the angled regions created by the presence of fixed baffles i n the mixing container, for instance where the baffles contact or join the inner sidewali of the container, is often a problem. This problem can be linked for instance with the difficult reachability of such regions, or with the fact that cleaning liquids also flow less in those regions.

These problems are especially manifested when dealing with mixing of high viscosity substances or fluids. These problems become also more important for automated high throughput mixing of small amounts of substances, requiring a large number of containers. Automated high throughput mixi ng is typically performed by mixing the content of the large number of containers i n parallel or contemporaneously. The skilled person knows that during this so-called batch processing different containers may be filled with different substances or different amounts of substances. Moreover sequentially adding different substances, different amounts or different relative amounts of substances is possible into the containers or into one or more different subsets of containers without the need for a new setup.

In EP0824036 a stirring apparatus is disclosed which comprises a vessel including a predetermined number of liquid supply ports into which liquid to be stirred is made to flow, and a l iquid exhaust port from which liquid is exhausted after stirring; a plural of stirring impellers separately arranged at two positions opposed to each other in the vessel, the plural of stirring impellers being rotated in the directions opposite to each other so that liquid in the vessel is stirred; external magnets arranged outside the walls of the vessel close to the stirring impellers, the external magnets composing magnet couplings havin no penetrating shafts in conjunction with the stirring impellers; and drive means for driving the external magnets so as to rotate the stirring impellers, arranged outside the vessel. This stirring apparatus is of the flow-through type, is of the closed type, and is limited for being used in high throughput due to cleaning and cross contamination issues. There exists a need in industry for new magnetic stirring systems, which solve at least some of the above mentioned problems. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a magnetic stirring system, associated devices and methods, which solve at least some of the above mentioned problems.

This object is met with the methods and means according to the independent claims of the present invention. The dependent claims relate to preferred embodiments.

According to a first aspect of the present invention, a mixing system is disclosed, comprising - a container for receiving and containing substances;

a magnetic stirring bar positioned within a first region of the container, and an associated first magnetic driving means adapted for generating a first changing magnetic field in the first region for driving a rotational movement of the magnetic stirring bar, wherein the mixing system further comprises

a baffle system arranged rotatably ( for instance along an a is parallel to a longitudinal direction of the container) within the container, the baffle system comprising one or more, e.g. a plurality of baffles, being flow directing planes for directing a flow of substances within the container, for instance in a clockwise or counterwise direction, the baffle system comprising at least one magnet; and

- a second magnetic driving means adapted for generating a second changing magnetic field, the second changing magnetic field substantially extending into a second region of the container, the second region comprising the at least one magnet and being different from the first region, to thereby drive the at least one magnet, wherein the baffle system is adapted and arranged such that it can rotate within the container by driving the at least one magnet by the second magnetic driving means.

It is an advantage that an improved mixing performance can be achieved with mixing systems according to embodiments of the present invention.

The substances to be mixed can be fluid or solid, so solid-fluid mixing and fluid-fluid mixing, as well as solid-solid mixing can be improved. A fluid can include for instance fluids (e.g. liquid (water-based, oil-based, solvent-based), emulsions, suspensions, pastes, high solids ...). The fluids can be Newtonian or non-Newtonian fluids, they can be shear thickening of shear thinning i n nature. The solids can for instance comprise wax, granulates, nanoparticles, polymers (such as for instance acrylics, polyesters).

Some parameters which influence the mixing and homogenizing behavior of fluids are the viscosity, rheology, density, reactivity, polarity and temperature.

Some parameters which influences the mixing and homogenizing behavior of solids are shape, density, porosity, particle size, solubility, temperature (viscosity), reactivity.

It is another advantage that regions with relatively less or no fluid flow are adjacent to the baffle structures, as is the case with fixed baffles, can be avoided or reduced in number and/or size and/or time resistance. This reduces the risk on attachment of the substances to the vessel and/or baffles. This would for instance also improve cleaning of containers after use. No or less dead angles are in fact created. According to pre) erred embodiments, the baffle system can be removed from the container as disposable and/or to be reused. This provides an additional advantage of more effective cleaning of the container.

The advantages are even more pronounced when mixing high viscosity fluids or mixing a high viscosity fluid with solid particles. It is a further advantage of embodiment of the present invention, that the occurrence or risk of vortexing which would be generated by the magnetic stirring bar during use without a rotatable baffle system according to aspect of the present invention, can at least partially be compensated by such rotatable baffle system. Thus a larger degree of freedom exist in choosing a type of magnetic stirring bar, certain types which would generate vortexing but which may have other suitable properties for mixing predetermined substances, could still be used in combination with the rotatable baffle system according to aspects of the present invention.

It has been shown that mixing systems according to aspects of the present invention allow a better mixing than similar devices with fixed baffles. A better mixing typically refers to a mixing whereby less air bubbles are captured / less foam is produced in the mixture, for instance due to less or no vortex formation in the mixture during mixing. A better mixing can also refer to the speed of the mixing process, i.e. the required time for appropriately mixing two predetermined substances can be reduced, for instance when compared to a similar system with fixed baffles. It can be noted that the use of fixed baffles of the type illustrated for instance in the disclosure of US6109780, would not be suitable for improving the mixing of substances with high viscosity. The "rounded" nature of these baffles will cause a flow which is still too I ami nary in nature in order to substantially improve mixing of such substances. As described further, certain types of bat tles and baffle orientations may improve this mixing, in combination with the rotating baffle system according to aspects of the present invention.

The container can for instance be a vessel, a vial or a bottle or any similar type of container. The container can be made of for instance glass, ceramic, (thermo-)piastic (PC, PP. P I I I . HDPE,

PET, PEI, PA,...), metal (HDG-steel, aluminium, cold rolled steel, inox, ... and all kind of metal alloys) as well as teflon or silicone coated metals, with a content ranging from 5 ml to 5 1, or ranging from 20 ml up to 1000 ml, even more preferably ranging from 20 ml u to 125 ml. single or multi-neck, depending on the final application.

The container can have a substantially cylinder-shape, or can have a cylinder-shaped main body completed with a bottle neck structure in order to provide a container of the bottle -type. It can also have other shapes.

According to preferred embodiments, the magnetic stirring bar has a height which does not extend above a certain level within the container, for instance a level defined as 20%, or 15%, or 10% of the container height or usable container height. The magnetic stirring bar can be of the bar-type or cylinder- type. It can for instance be coated or encapsulated. It can comprise for instance glass, ceramic or plastic. The magnetic stirring bar can be of any type known to the skilled person, and is not limited to pure bar-shapes. For instance, the magnetic stirring bar may have as a basis a bar-shape, which is completed with protrusions, holes or extensions which can typically be added in order to tune the stirring characteristics or application. For instance the magnetic stirring bar is itself not bar-shaped (although named "bar"), but for instance cross shaped, or cylindrical, circular or otherwise shaped. The magnetic stirring bar should be magnetically drivable, and should be suitable for stirring the respective substances. It could for instance be any of the stirring bars commercially known as Pyrex® Spinbar® Glass Stirring Bars, Saturn Spinbar®, Spinfin®, Spinplus®, Spinring®, Spinstar®, Spinvane®, Spinwedge®.

According to preferred embodiments, the first magnetic driving means is arranged below a bottom surface of the container and the second magnetic driving means is arranged next to and adjacent to a sidewall of the container, or adjacent and above the container. These relative positions may naturally reduce the risk on unwanted interference between the first and second magnetic driving system. Such solutions are then more easily susceptible to finding suitable predetermined magnetic field strengths of the first and second magnetic driving system which reduce or avoid interference between the first and second magnetic driving system. The first magnetic driving means may further exert an attraction of pulling force on the magnetic stirring bar towards the bottom of the container.

When the first magnetic driving means is arranged below a bottom surface of the container and the second magnetic driving means is arranged next to and adjacent to a sidewall of the container, the second magnetic driving means, e.g. the magnets comprised therein, may further be adapted for being adjustable in height with respect to the bottom of the container or vial, for instance taking into account variability of the liquid level during formulation preparation in order to control e.g. aeration.

According to preferred embodiments, the first region of the container lies within the lower region of the container, the lower region being the region below the level defined as 80% of the container height, but preferably as 10%, or 20 % or 30% or 40 %,50%, 60% or 70% of the container height.

According to preferred embodiments, the baffle system is adapted to have its baffles, nor support structure supporting the baffles as described further below, not extend into the first region, said first region preferably corresponding to a central lower region of said container, wherein the magnetic stirring bar is positioned, to thereby not interfere with the magnetic stining bar present in the first region.

According to preferred embodiments, the relative surface area of a main surface of each of the baffles with respect to the surface of a maximal cross-sectional surface area of the container is above 5%.

According to preferred embodiments, the second region lies within the upper halve of the container, or within the upper 60%, or within the upper 70%, or within the upper 80%, or within the upper 90 % of the container, when considered without bottleneck, if such is present. According to preferred embodiments, a longitudinal direction of the baffles is oriented substantially vertical or at an angle within the container, or substantially parallel to a longitudinal axis of said container (for instance a symmetry axis of the container), and a main surface of each of the baffles is oriented substantially perpendicular on a representative rotation direction of the fluid. Such representative rotation direction can for instance be a direction laying within a plane perpendicular on the longitudinal direction, and can further be defined as a tangential line of a circle which has the longitudinal axis as a center.

According to preferred embodiments, the longitudinal direction of the baffles, for instance the longitudinal direction of a main surface of the baffles, can be oriented at an angle with respect to a substantially flat bottom surface of a container, the angle being different from 90 degrees. According to preferred embodiments, the longitudinal direction of the baffles, for instance the longitudinal direction of a main surface of the baffles, can be oriented at an angle different from zero with respect and/or with respect to a direction defined by the inner sidewaiis of the container, or with respect to a longitudinal direction of the container.

The baffles may extend from a lower level up until an upper level, over a distance larger than 20%, or larger than 30% or larger than 40% or larger than 50% or larger than 60% or larger than 70% or larger than 80% or larger than 90% of the useable container height. The usable container height refers to the relative compatibility in size and shape of the baffle, and baffle system, and internal surface of the container. The usable container height can be the full height of the container, or the full height of the container below a bottle neck if present. The usable container height may as well be 90% or 80% or 70% or 60% of such height.

According to preferred embodiments, the baffles are of the blade-type or plate -type; they comprise a first main surface and a second main surface which together constitute a substantial part ( for instance 80% or 90 % or 95 % or 99 %) of the total surface of the baffle, and are connected to each other by side surfaces forming the rims of the baffles (lower rim directed downwards, upper rim directed upwards, inner side rim directed towards the internal of the container when in use/placed in the container, outer side rim directed towards the external of the container when use/placed in the container). The main surfaces can be flat or curved. The main surfaces can be parallel to each other or can be arranged at an angle with respect to each other of for instance smaller than 50°, or smaller than 45° or smaller than 40°, or smaller than 30°, or smaller than 20°, or smaller than 10°. According to preferred embodiments, the ba fle system is adapted to have its baffles substantially extend over a full length of the container, or over a full length without the bottle neck, if present. According to preferred embodiments, a relative position of the plurality of baffles is fixed with respect to each other, the fixed positions being supported or by a support structure of the baffle system.

According to preferred embodiments, the support structure can comprise one or more connecting elements which can provide a rigid connection between the different baffles in order to define a fixed relative configuration of the baffles with respect to each other and with respect to the container. According to preferred embodiments, the support structure, and the respective connecting elements can be arranged such that they can be easily fold and unfold between a fixed extended state and a loose or fixed reduced state, as will be described further below. During transformation towards the fixed extended state, the connecting elements themselves may not be deformed. Alternatively, at least one of the connecting elements may be deformed, for instance elastically, in order to provide a resilient effect when returning towards the reduced state. According to preferred embodiments, the ba fle system is symmetrically arranged along a central axis, the central axis being adapted for corresponding to a longitudinal axis of the container. The baffles can be symmetrically arranged along a central axis of the baffle system.

According to preferred embodiments, the baffles are positioned substantially parallel to a common longitudinal direction, and at equidistant angular positions round a central of the baffle system, preferably corresponding to a longitudinal direction of the container when positioned in the container.

According to preferred embodiments, at least one of the baffles comprises at least one opening. The one or more openings can reduce the resistance and can be preferred especially for blending suspensions. The opening in the baffle is typically adapted for stirring both low and high viscosity liquids. According to preferred embodiments, the baffle system is arranged such that, for each baffle, a spacing exists between an external rim of the baffle and an inner wall of the container, the external rim being the rim directed towards the inner wall of the container. Such a spacing may be sustained and kept constant by spacer elements. Such spacer elements or spacers may be arranged or may constitute small protrusions at the outer rims of the baffles, which are adapted for interacting with the inner sidewall of the container when the distance between the outer rim and the inner sidewall of the container would become too small. The spacer elements may advantageously be positioned at the upper region of the bai l ies, for instance at the upper 50%, or upper 40%, or upper 30%, or upper 20%, or upper 10% of the baffles. The use of spacer elements may also contribute to avoid or limit a possible tilting of the bai lie system, away from a longitudinal axis of the container, during use.

According to preferred embodiments, the spacing is constant and is larger than a predetermined maximum grain size of a solid granulated substance to be mixed. This may especially be advantageous when mixing solid granulated substances, as mixing is possible without accumulation of solid particles near the outer end of the baffles, between the outer rim and the inner surface of the container.

According to preferred embodiments, each of the baffles extends into a lower peripheral region of the container. The lower peripheral region can be the region below a level of 40%, 30%, 20%, or 10 % of the height of the container, near the inner surface of the container, not including a central lower region wherein the magnetic stirring bar is positioned.

According to advantageous embodiments, the mixing system is in use filled u until a level which is below the upper portion of the baffles; in other words, the baffles do preferable extend upwardly from the top surface of the mixture. This provides an optimal mixing performance, even more in the case of mixing high viscosity substances. According to preferred

embodiments, the mixing system comprises a filling with substances to be mixed or which have been mixed. Preferably the filling level is below the level defined by the upper surface of the baffles when the baffle system is positioned in the container.

In relation to the description of the support structure above, the baffle system can preferably be adapted for being configurable in at least a reduced volume state (or reduced state) or full volume (or fixed extended) state. The container may comprise a container opening for receiving and removing substances. The container may for instance comprise a bottle neck portion and bottle opening. The baffle system in the full volume state not being removable from the container through this opening, while being removable through the opening in the reduced volume state. This allows an easy removal of the baffle system from the container, which may be advantageous in the context of cleaning and reuse of baffle systems and/or containers.

According to preferred embodiments, the container has an opening for receiving and removing substances at its upper side. The container may have a substantially open, partially open or completely open upper side. In case of a completely open upper side, this may be defined by an upper rim of the sidewalk of the container. The containers may also be provided with a removable closing lid for closing of the upper side or an opening in the upper side. According to certain embodiments, the closing lid can comprise a lid opening, and may on its turn be provided with a smaller closing lid for closing the lid opening. According to preferred embodiments, the containers may comprise no further opening than the opening or openings at its upper side. For instance, no openings may be present in its lower side, or in the sidewalis of the container. The container may thus embody a closed vessel with one, only one, or more openings at its upper side. Moreover, the container could be a disposable recipient.

According to preferred embodiments, the baffle system is adapted to be brought from a reduced volume state into a full volume state by centrifugal forces exerted on the baffle system when being rot at ably driven by the first magnetic driving means.

According to preferred embodiments, each of the bat tles comprises at least one magnet. The magnet may be positioned in the upper portion of the baffles, for instance in the upper 50 %, or the upper 40% , or the upper 30%, or the upper 20%, or the upper 10%, or the upper 5% of the bat tle. Preferably the magnet can be positioned near or at the outer rim of the baffles. According to preferred embodiments the spacer elements may comprise such magnets, at least in part or completely. According to preferred embodiments, the at least one magnet of the baffles has a north-pole and a south-pole, and has a north-south axis connecting the north-pole and the south-pole, and is arranged within the baffle system such that the north-south axis is positioned in a radial direction outward from a central axis of the container. According to alternative embodiments, each north-south axis lies along a direction substantially perpendicular to a radial direction outward from a central axis of the container.

According to preferred embodiments, the second magnetic driving means comprises one or more magnets which are arranged such that they can be driveably rotated along a longitudinal axis of the container around and along an external sidewall of the container at a height corresponding to the at least one magnet within the baffle system. According to preferred embodiments the height of the second magnetic driving means, for instance the height of the magnets used in the second magnetic driving means with respect to the bottom level of the container, may be varied. The second magnetic driving means may thus comprise a means for varying the height of the one or more magnets used for driving the baffle system. The second magnetic driving means may further comprise a controller device which is adapted for controlling the height of the magnets in the second magnetic driving means, and in certain embodiments thus of the associated baffle system, as a function of mixing parameters, for instance as a function of the filling level of the container.

The one or more magnets may be the same in number as the plurality of magnets of the baffle system. Each magnet of the baffle system may cooperate with a respective magnet of the second magnetic driving system. The corresponding magnets may be arranged in close vicinity, while being separated by the sidewall of the container. They may be arranged such that the magnetic attraction between the corresponding magnets is as large as possible.

According to preferred embodiments, the one or more magnets are arranged in a ring-shaped support structure at equidistant angular intervals, and the ring-shaped support structure is rot al ably arranged, i.e. arranged for rotating in a plane which is substantially perpendicular to a longitudinal direction of the container.

The ring shaped support structure may be driven by a driving means as for instance a motor, e.g. an electrical motor. As an alternative the magnetic stirring can alo be inductive - driven, stepper-driven or disc motor driven. According to preferred embodiments, the one or more magnets of the first magnetic driving system comprises a north pole and a south pole, the north pole and the south pole being connected by a north-south axis, and wherein the one or more magnets are arranged such that their north pole or south pole are positioned directed towards a south pole or a north pole respectively of the baffle system. According to preferred embodiments, the mixing system further comprises a control means for controlling a relative rotation speed and/or relative rotation direction of the first and the second magnetic driving means, preferably independently. Advantageously, the control means can be adapted for controlling the baffle system and the magnetic stirring bar to rotate in opposite directions, providing new opportunities and effects in the mixing process.

According to advantageous embodiments, the control means is adapted for controlling the baffle system and the magnetic stirring bar to rotate at different speeds. The optimal relative rotation speed and direction of the magnetic stirring bar and baffle system is believed to be dependent on for instance volume and viscosity of the substances to be mixed. The control means may be adapted for controlling the rotation speeds and directions of the magnetic stirring bar and baffle system as a function of these parameters. The control means may be adapted for controlling the relative rotation speeds and directions of the magnetic stirring bar and baffle system as a function of these and/or other parameters (as e.g. tempcrature.pl I. air-entrapment, vortexing).

According to advantageous embodiments, the baffle system (for instance its support structure) further comprises a low-friction guiding means for guiding the magnetic stirring bar in its rotational movement when the position of the magnetic stirring bar would move upwardly in the container up until a predetermined level, while blocking any further upward movement of the magnetic stirring bar within the container, and substantially independent on the rotational movement of the baffle system. Such a guiding means may for instance have a rounded surface. It may have a rounded, concave surface directed toward the bottom surface of the container. It may have a shape corresponding to a section of a sphere, for instance one of the sections of a sphere when the sphere would be cut and divided by a flat plane.

According to preferred embodiment, the one or more magnets of the baffle system are positioned above the filling level. Alternatively, the one or more magnets of the baffle system are positioned below the filling level.

Depending on the nature of the substances, the magnetic interaction between the magnets of the second magnetic driving system and the magnets of the baffles may be better below or above this level. According to preferred embodiment, the container comprises an opening, preferably at its upper or top side, for filling substances into the container while mixing the substances. According to preferred embodiment, the mixing system further comprises a weighting means for weighting the container possibly containing the substances mixed or to be mixed. The weighting means can advantageously collaborate with a dispersing device, for instance overhead dispersing device which is adapted for adding substances to the container while stirring; the amount of added substance can then easily be monitored and/or controlled.

According to preferred embodiments, the container has a width smaller than 50 cm, or smaller than 40 cm, or smaller than 30 cm, or smaller than 20 cm, or smaller than 10 cm, or smaller than 5 cm.

According to preferred embodiments, the baffles have a width larger than 1 cm.

According to preferred embodiments, the baffles have a width smaller than 25 cm, or smaller than 20 cm, or smaller than 15 cm, or smaller than 10 cm, or smaller than 5 cm.

According to preferred embodiments, the container has a height smaller than 50 or 40 or 30 or 20 or 10 cm, the baffles have a height or respective height larger than 25cm, or larger than 20cm, or larger than 15 cm, or larger than 10 cm, or larger than 5 cm.

According to a second aspect of the present invention, an automated platform for high throughput mixing is disclosed comprising a plurality of mixing systems according to any of the embodiments of the first aspect. The plurality of mixing systems can be arranged according to a matrix structure for parallel processing.

According to a third aspect of the present invention, the use of the mixing system according to any of the embodiments of the first aspect is disclosed.

According to a fourth aspect of the present invention, a baffle system is disclosed as described above for any of the embodiments of the first aspect.

According to a fifth aspect of the present invention, a method for stirring at least one substance, e.g. for mixing substances, in a container is disclosed, comprising: - magnetically driving a rotational movement of a magnetic stirring bar arranged within the container;

wherein the method further comprises

- magnetically driving a rotational movement of a baffle system, the baffle system positioned within the container and comprising a plurality of baffles planes for directing a flow of substances within the container, said baffle system comprising at least one magnet.

According to preferred embodiments, the magnetic stirring bar and baffle system are driven independently by a first and a second magnetic driving means respectively.

According to preferred embodiments, the method further comprises controlling the rotation speed of the controlling a relative rotation speed and/or relative rotation direction of the first and the second magnetic driving means.

According to preferred embodiments, the method further comprises controlling the baffle system and the magnetic stirring bar to rotate in opposite directions.

According to preferred embodiments, the method further comprises controlling the baffle system and the magnetic stirring bar to rotate at different speeds.

According to preferred embodiments, the method further comprises controlling the rotation speeds and directions of the magnetic stirring bar and baffle system as a function of volume and/or viscosity and/or other parameters. The control means may be adapted for controlling the relative rotation speeds and directions of the magnetic stirring bar and baffle system as a function of volume and/or viscosity and/ or other parameters (as for instance temperature, pi I, air-entrapment, vortex i ng ).

According to preferred embodiments, the method comprises filling the container up until a level which is lower then the level correspondin to the upper level of the baffle system. It will be appreciated that features and advantages disclosed for one of the above aspects of the present invention are applicable to any of the other aspects, mutatis mutandis. For instance, features and advantages disclosed for the mixing device of the first aspect, are applicable to the method for mixing of the fifth aspect, mutatis mutandis. BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the present invention will become apparent from the drawings, wherein: FIG. I Λ represents top views of embodiments according to an aspect of the present invention. Fig. IB represents a top view of another embodiment according to an aspect of the present invention.

Fig. 2 illustrates the principle of a second magnetic driving means according to embodiments of the present invention.

Fig. 3 shows a side view of an embodiment of a mixing system according to aspects of the present invention.

Fig. 4 shows a side view of an embodiment of a mixing system according to aspects of the present invention.

Fig. 5 to Fig. 7 are side views of embodiments of a mixing system according to aspects of the present invention.

Fig. 8a and 8b illustrate embodiment according to the present invention, in top view.

Fig. 9a and 9b depict a cross-sectional view of a container and a baffle, along a plane corresponding to a baffle plane, and illustrates parameters used in explaining certain embodiments of the present invention.

Figure 10 is a side cross-sectional view of an embodiment according to the present invention.

Figures 11 to 13 are perspective views of embodiments according to the present invention.

Figure 14 is a perspective view of an embodiment depicted in Fig. IB.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated. The term "comprising", used i n the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

In the drawings, like reference numerals indicate like features; and, a reference numeral appearing in more than one figure refers to the same element.

Fig. 1A shows a schematic top view of embodiments of the present invention. A cylindrical container 3, wherein a freely rotatable baffle system 2 is mounted, is depicted. A longitudinal axis of the baffle system 2 corresponds to a longitudinal symmetry axis of the container. Each of the baffles 4 constitutes a straight flat flow guiding plate. The baffles 4 are mounted around the longitudinal axis at equidistant angles. Preferably, the baffles can all have the same shape. The planes defined by the straight flat baffles are preferably parallel to the longitudinal axis of the cylindrical container. When N baffles are comprised in the baffle system, they are preferably positioned at angles of 3607N. Two baffles are for instance positioned relative to one another at 180°. Three baffles have equidistant angular spacings of about 120°; four baffles correspond to equidistant angular spacings of 90° etc. The baffle system comprises at least one magnet (not depicted). A magnetic driving system ("second magnetic driving system") can drive the rotational movement of the baffle system within the container. This can be achieved by a laterally positioned magnetic driving system, as described further below, wherein preferably a plurality of baffle magnets are comprised i n the baffle system, each of the magnets preferably provided within a respective baffle, for instance on a basis of one magnet per baffle. Alternatively, this can be achieved by driving for instance a single magnet, positioned in the upper central region of the baffle system, in a similar way as the magnetic si irri ng bar is driven, as also explained below.

The different baffles within the bat tle system are connected to each other by means of a support structure 20.

An alternative embodiment is depicted i n Fig. IB, wherein a single bat tle 4 is comprised in the baffle system 2. The baffle system is similar to the baffle system comprising two baffles as described before, but the second baffle is not present and is replaced by a thin extension or portion of the support structure 20 which extend upwards up until a level of the baffle magnet in the first bat tle. At his level or height the thin extension comprises a second bat tle magnet which can cooperate with a second magnet of the magnetic driving system for the bat tle system. Furthermore, a weight compensation of balancing element 201 can be provided on the support structure, for instance near the end of the support structure extension. This element 201 may comprise the second baffle magnet. The weight compensation of balancing element can provide the function of counter-balancing the larger weight of the first baffle when compared to the weight of the support structure extension and/or second bat tle magnet provided at the support structure extension, such that the baffle system remains in an essentially vertical position when being rotated within the container 3.

In Fig. 2, the functioning of the second magnetic driving means 6 is illustrated, according to aspects of the present invention. Centrally, a container 3 is depicted, comprising a bat tle system 2 as in the first and second figure of Fig. 2. The support structure is present but not depicted for clarity reasons. The two bat tles 4 i n the left example, and the four baffles 4 in the right example, each comprise a single magnet (not depicted). The magnetic drivi ng means 6 comprises a ring or other support structure 60. The support structure comprises or supports a number of magnets 61 , 62, 63, 64 at positions corresponding with the baffle magnets, and thus under similar configurations as described for the bat tle orientations (180°, 120°, 90°, etc.. . angular separation). The ring or support structure itself is rotatably mounted and driven by a driving means such as for instance an electrical motor, the rotation speed of which can be controlled. The magnets are arranged such that a permanent attraction takes place between bat tle magnets BM1 , BM2, BM3, BM4 and corresponding magnets 61 , 62, 63, 64 of the second driving means. Once the bat t le magnets are approaching their associated driving means magnets 61,62,63,64 (or vice versa) - both magnets may align automatically as they attract each other. Therefor, for instance, the north poles of the baffle magnets may be directed and facing the south poles of the corresponding magnets of the second magnetic driving means. The positions of the magnets, as well as their strength and field properties, are preferably predetermined and such that a strong attraction force is existing, which is strong enough to mix substances with relatively high viscosities. The resistance due to forces acting on the baffles by the substances to be mixed should in other words not allow the baffle magnets and the second magnetic driving means to be driving away from each other. When the support structure 60 is then rotated around an axis which substantially corresponds with a longitudinal axis of the container 3, whereby the distance between the respective pairs of baffle magnets driving means magnets is kept small enough, and preferably constant, the baffle system itself will start rotating along the same axis and will thus be driven. The rotation speed of the baffle system then corresponds to the rotation speed of the second magnetic driving means ( =( _s ), as well as its direction (negative or positive speed).

Fig. 3 illustrates a side view of a mixing system 1 according to embodiments of the present invention. The baffle system 2 is placed within the container 3. The baffle system comprises two baffles 4, which are of the straight flat type and which extend from the bottom of the vessel or container up into the upper region of the container 3. Their longitudinal axis is aligned with respect to a central axis of the cylindrical container 3. The baffles are arranged at 180° in a plane perpendicular on the central axis. Each of the baffles comprises a baffle magnet (BM2 and BM 4), at the same height within the container 3. The baffles' position is fixed with respect to each other, preferably by means of a support structure 20. The baffles 4 are, as an example, substantially rectangular. The baffles comprise an inner rim 44, and outer rim 43, a lower rim 46 and an upper rim 45, which connect a front main surface 41 and a back main surface 42 (front and back for instance defined with respect to facing and facing away from the incoming flow of substances respectively). The upper portion of the baffles extends from the surface of the filling, i.e. it extends above the filling level (FL), for improved mixing.

The baffles have a width BW, and a length BL, both of which can depend on the viscosity of the substances to be mixed. The lower rim 46 of the baffles preferably rests on the bottom of the container, but this is not necessary.

A magnetic stirring bar 8 is provided within the container 3. at a first portion as for instance at a central lower portion. The magnetic stirring bar comprises a north and a south pole which are positioned corresponding to the south and the north pole respectively of a magnet i n the first magnetic driving means 5, which is rotatabie mounted and which can be driven by means of for instance an electrical motor, the speed and direction of which can be controlled (e.g. c¾ ). The second magnetic driving means 6 comprises magnets 62 and 64 at positions corresponding with their associated baffle magnets BM2 and BM4, and is adapted for driving the magnets i n the baffle system, and thus for driving the rotational movement of the baffles in speed ((¾₎ and direction (negative or positive speed).

For instance, the first magnetic driving means can be driven at a speed coi (stirring bar rotating at this speed), while the second magnetic driving means can be rotated at a speed ω₂ (baffle rotation speed) which is half or double the speed ωι. ωι can be N times ω_2, N being an integer value. Or <¾ can be N times ooi. Advantageously, ooi and <a₂ can have opposite signs, i.e. baffle system and magnetic stirring bar can rotate in opposed directions. They can have opposite signs, while the same relation can apply for their absolute values I <»il and I ω₂Ι as described above. According to preferred embodiments, a gap G is present between the internal wall of the (eg cylindrical) container and the outer ri m 43 of the baffles 4. This may provide advantages with respect to mixing performance as well as to cleaning and the reduction of foaming. Note that the filling level (FL) is below the level of the baffle magnets. This is also illustrated in Fig. 8a and Fig. 8b. Fig. 4 illustrates a similar embodiment as depicted in Fig. 3, but here, the baffles comprise, or are foreseen of, spacer elements 7, which are positioned at the outer rim of the bat tles in order to perform gap size control. Moreover, the presence of such spacer elements may increase stability when rotating. Fig. 4 also illustrates the lower region of the container ( I K ) and the second region (R2) of the container where the second changing magnetic field substantially extends. The filling level (FL) is here above the level of the baffle magnets.

Whether the filling level should stay above or below the level of the baffle magnets can be predetermined, based on magnetic attraction properties in air or in substances to be mixed. In Fig. 5 illustrates the embodiment of Fig. 3, wherein the filling level is above the level of the baffle magnets, and as is advantageous, below the upper rim 45 of the bat t les. In Figure 5 the first region (Rl), wherein the stirring bar is positioned, and wherein the first changing magnetic field is generated, as well as the lower periferiai region Rip, which constitutes the lower region of the container next to the region where the stirring bar is located, i n order to avoid collision between stirring bar 8 and baffles 4.

In Fig. 6 a further embodiment according is depicted, wherein a second magnetic driving means comprises two support structures 6 and 6*, which are similar or identical, and which are provided the one below the other. This can preferably be combined with a second magnet per baffle for the baffle system. A first set of magnets BM1 , BM2, BM3, BM4 is arranged at a first height within the container, or at a first height of the baffles, and a second set of baffle magnets BM1 *, BM2*, BM3*, BM4* is arranged at a second height within the container, or at a second height of the baffles. Both sets of baffle magnets can then be attracted to corresponding magnets on the support structures 6 and 6* respectively. Support structures 6 and 6* are then preferably driving together at the same speed, and a fixed connection between both structures 6 and 6* can be foreseen. This may improve the strength of the connection and may be advantageous for substances with higher viscosities.

In Fig. 7, a similar embodiment is depicted as in Fig. 3, but the baffles comprise at least one opening 40. This may improve mixing performance or may reduce the necessary strength of magnetic coupling between the baffle system and the second magnetic driving means.

In Fig. 14 a side view similar to the one of Fig. 3 is depicted for embodiments described in relation with Fig. IB, wherein the baffle system comprises a single baffle, an extension of the support structure 20, and an optional balancing element 201.

In Fig. 9a and Fig. 9b, some parameters which may be used in defining the invention have further been clarified. The usable level (UL) of the container 3 may be a certain level below the top of the container. It may for instance be a level corresponding to the level where a bottle neck structure for a container starts when going upwards. The maximal cross-sectional surface area of said container can correspond to the maximal cross-sectional area (XS) of the container (depicted on the right for an open cylindrical container, i.e. a container having an open upper side, without bottleneck for instance). Alternatively, the maximal cross-sectional surface area (XS) of said container can correspond to the maximal total cross-sectional area of the container below the usable level (UL), for instance when the container would have a bottle neck section on top of a cylindrical section. Anyhow, the skilled person will understand that other shapes of containers can be used, and that the maximal cross sectional area for any of such containers can easily be determined.

In Fig. 10, an embodiment is depicted wherein the support structure 20 comprises a blocking means 21 for controlling the position of the magnetic stirring bar, if the latter would move upward during the mixing process. This may improve stability.

Aspects of the present invention thus disclose the use of two a priori independent rotational mixing devices in a container, as for instance recipients, for instance a disposable recipient that can be integrated in an automated and high-throughput formulation platform. According to certain sub aspects, the flexible (re-usable or disposable depending on application) character of the mixing devices and the disposable character of the recipients can offer a significant advantage compared to existing containers with integrated (fixed) mixing devices where cleaning is a real issue. Moreover, a decrease of the vortex formation and air-entrapment or bubble formation can be achieved to minimize the foaming and reduce the amount of air incorporated into the mixture.

Furhter optimizing the baffle shape and configuration can still further improve the mixing properties as to vortex creation and foaming reduction. The baffles can for instance be flat plate, triangle, propeller, helix, honey structure, c-curved, etc. ....

There is a limited amount of types of commercially available magnetic stirring bars, especially stirring bars with reduced vortex creation and foam formation. The baffle systems according to aspects of the present invention, can preferably be easily implemented/recovered in/from vials and can significantly enhance the mixing process.

The stirring speeds (rotation speed) and directions of both independent rotational mixing devices (e.g. torque or power required) can be controlled, which can optimize mixing. Depending on the viscosity specifications of the formulation/solution and the respective volume (or %) of the solution in the vial, these speeds and directions can be optimised. It is an advantage of mixing systems according to embodiments of the present invention that an optimal homogenization, and a reduction of air entrapment into some air-sensitive formulations can be established. The screening of different commercially available PTFE coated magnetic stirring bars (i.e. barbell, octahedral, cylindrical, plain, removable ring, oval, egg shaped, cross, pivot ring, tapered, triangular, triangular with rib, crosshead-double, crosshead-single, square, disc, spherical, hub, test tube wings, elliptical rare earth magnets and the like) has shown their limitation for mixing viscous solutions.

In Figure 10, a 100 ml container or vial 3, comprises a magnetic stirring bar 8 which can be driven by an external magnet, or first magnetic driving means 5. The container further comprises a re -usable independent baffled system 2, with magnets dial fie Magnets (BM)) incorporated in the baffles. These magnets, and thus the baffle system into which they are integrated, can be driven by the 2nd independent magnetic driving means 6. The magnets in the baffles can be positioned at different heights depending on the shape, the robustness and design of the baffles 4 or baffle system 2. Depending type of liquids/solids, adapted baffles (impeiier/propeiler/paddle) can be used. Due to the independent second rotational magnet drive (magnetic driving means), the baffle device can rotate clockwise or counter-clockwise at a rotation speed which can be different from the rotation speed of the first magnetic driving system. The most common baffles are straight flat "plates" that run along the straight side of vertically oriented cylindrical vials, but many variations are possible. Also the number of baffles can be 1, 2, 3, 4 or more, but can be larger. The baffle width is preferably chosen in function of the viscosity of the substances to be mixed or mixture. As the viscosity decreases, baffling becomes more important and the baffle width gets larger. Figure 11 shows a perspective view of a mixing system according to embodiments of the present invention.

Figures 12 and 13 illustrate baffle systems according to embodiments of the present invention, which are optimized for specific mixing applications and/or viscosity ranges or relative viscosity ranges of substances to be mixed. The baffle magnets can be positioned also near the lower portion of the container. The baffles are cross-linked and their relative position in preferably fixed with respect to each other, by means of the support structure 20. Experimentally, general formulations in a 100 ml container or vial containing low viscous to high viscous liquids/pastes with viscosities ranging from 1 mPa.s to 50,000 mPa.s (and which is believed to be extendable/applicable to viscosities u to 250,000 mPa.s) have been

homogenized in different mixing ratios. This was performed by combining a magnetic stirring bar generating a magnetic field strength of 150 nil' at the bottom of the recipient rotating at 1500 Rotations per minute (RPM) in a clockwise direction, with a counter clockwise rotating baffle system being rotated at a speed of ranging from 30 to 300 RPM. The bat tle system comprises magnets generating a magnetic field strength of 200 m l . The formulations were found to be homogeneous after 10 to 15 minutes, while normally at least 20 minutes is required if no baffles or if fixed baffles are used. This shows for instance that the use of a rotating baffle system in combination with a stirring bar improves the mixing process, as it reduces the required mixing time towards homogenization. Moreover, no bubble creation or foaming has been observed. The magnetic stirring bar can thereby have a magnetic field strength between 25 iiiT

600 m l . more preferably in the range of 45 - 200 in Γ and even more preferrably between 50 m Γ to 180 nil . The magnets of the magnetic driving means for the baffle system can have a magnetic field strength within the range of 100 to 750 m l , more preferably between 100 m l to 400 nil' and even more preferably between 120 nil^' to 300 nil .

When indicating 'acceptable' as mixing criteria, it is meant that homogenization is

accomplished within max. 30 min with limited or no aeration. When indicated 'borderline (long period)' as mixing criteria, it is meant that more than 30 min is required but less than 45 min to homogenize the mixture with limited or no aeration. It should thus be understood that the "acceptable" and "borderline" marking refer to the time budget needed for sufficient mixing with limited or no aeration.

As an example, a mixture of water (example A) and glycerin (example B) in different ratios, by means of addition of a blue dye drop in order to visualize the homogenization, were performed for a stirring system (magnetic impeller) without and with baffles and are mentioned in table 1. The initial mixing time was set to 5 minutes for low to medium viscous systems (1 - 1.000 mPa.s), extended to 15 min to be acceptable for viscous mixtures (up to 50.000 mPa.s) and borderline if mixing time is exceeding 30 min but within 45 min. The mixing speed of the magnetic impeller (first magnetic driving means) was varied between 100 RPM u to 2000 RPM. The rotational speed of the baffles (second magnetic driving means) was set at 40 RPM.

The following was found for a stirring system respectively without baffles and with baffles

Table 1. Mixing results of a stirring system respectively without and with baffles

Another example, a mixture of oligomers (e.g. polyester acrylate type) (example A and example C) and diluent (e.g. TMPTA) (example B) in different ratios, in order to visualize the homogenization, were performed for a stirring system without and with baffles and are mentioned in table 2 (low to medium viscous mixtures) and 3 (low to high viscous systems). The initial mixing time was set to 10 minutes for low to medium viscous systems (1 - 10.000 mPa.s), extended to 20 min to be acceptable for viscous mixtures (up to 50.000 mPa.s) and borderline if mixing time is exceeding 30 min but within 45 min. Mixing speed of the magnetic impeller was varied between 200 RPM u to 2000 RPM. The rotational speed of the bat tles was set at 40 RPM. The following was found for the stirring system according to aspects of the present invention respectively without rotatable baffles and with rotatable baffles.

Example Example B Ratio Homogenisation without Homogenisation with baffle

A low Ex A - baffle

viscous high Ex B

viscous

Observation RPM Observation RPM impeller impeller

115 8624 mPa.s 5/95 YES 2000 YES 600 mPa.s

115 8624 mPa.s 10/90 YES 2000 YES 600 mPa.s

115 8624 mPa.s 30/70 Acceptable 1300 YES 750 mPa.s

115 8624 mPa.s 50/50 Acceptable 1200 YES 750 mPa.s

115 8624 mPa.s 70/30 Acceptable 1500 YES 800 mPa.s

115 8624 mPa.s 90/10 YES 1300 YES 700 mPa.s

115 8624 mPa.s 95/5 YES 1200 YES 700 mPa.s

115 8624 mPa.s 100/0 YES 600 YES 300 mPa.s

115 8624 mPa.s 0/100 YES 2000 YES 1450 mPa.s

Exan pl Example C Ratio Ex A - Homogenisation without Homogenisation with c Λ Ex C

baffle baffle

low high

viscous viscous

Observatio RPM Observatio RPM n n

impeller impeller

115 48964 10 / 90 No 2000 Borderline 1200 - 2000 ml'a.s ml'a.s

115 48964 5 / 95 No 2000 Borderline 1200 - 2000 mPa.s ml'a.s

1 15 48964 30 / 70 No 2000 Borderline 1200 - 2000 ml'a.s ml'a.s

1 15 48964 50 / 50 No 2000 Acceptable 1700 ml'a.s ml'a.s

1 15 48964 70 / 30 No 2000 YES 1000 mPa.s ml'a.s

1 15 48964 90 / 10 No 2000 YES 1200 mPa.s mPa.s

1 15 48964 95 / 5 No 2000 YES 1000 ml'a.s ml'a.s

1 15 48964 100 / 0 YES 600 YES 300 ml'a.s ml'a.s

1 15 48964 0 / 100 No 2000 Borderline 1200 - 2000 ml'a.s mPa.s

Table 2. Mixing results of a stirring system respectively without and with baffles. In the experiments described above with the first magnetic driving means (magnetic impeller) and the second magnetic driving means (baffle system), both magnetic impeller and baffle system were driven in the same rotation direction. It has moreover been shown that when magnetic impeller and baffle system were driven in opposite rotation directions, similar homogenization performances were achieved. It is to be understood that the i nvention is not limited to the particular features of the means and/or the process steps of the methods described as such means and methods may vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used i n the specification and the appended claims, the singular forms "a" "an" and "the" include singular and/or plural referents unless the context clearly dictates otherwise. It is also to be understood that plural forms include singular and/or plural referents unless the context clearly dictates otherwise. It is moreover to be understood that, in case parameter ranges are given which are delimited by numeric values, the ranges are deemed to include these li mitation values.

The particular combinations of elements and features in the above detailed embodiments are exemplary only. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary ski l l in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not l i mit the scope of the i nvention as claimed.

It wi ll be appreciated that embodiments of the present invention are even more advantageous when used in automated high throughput mixing, as typical ly performed by mixing the content of the number (e.g. at least two, or at least 10, or at least 100 ) of similar containers in parallel or contemporaneously.

Different containers may be filled with different substances or different amounts of substances. Moreover sequentially adding different substances, different amounts or different relative amounts of substances is possible into the containers or into one or more different subsets of containers without the need for a new setup. It will be appreciated that the embodiments wherein the first magnetic driving means is arranged below a bottom surface of the container and wherein the second magnetic driving means is arranged next to and adjacent to a sidewall of the container is particularly suitable for batch processing, as for instance no obstacles for the second magnetic driving means are present next to and adjacent to the container, and as for instance the upper surface or side of the containers can be completely or at least partially open, or can be completely or partially opened and possible closed again thereafter.

Claims

1 . A mixing system, comprising

a container for receiving and containing substances;

a magnetic stirring bar positioned within a first region of said container, and an associated first magnetic driving means adapted for generating a first changing magnetic field in said first region for driving a rotational movement of said magnetic stirring bar, wherein said mixing system further comprises

a baffle system arranged rotatably within said container, said baffle system comprising one or more baffles or flow directing planes for directing a flow of substances within said container, said baffle system comprising at least one magnet; and a second magnetic driv in means adapted for generating a second changing magnetic field, said second changing magnetic field substantially extending into a second region of said container, said second region comprising said at least one magnet and being different from said first region, to thereby drive said at least one magnet; wherein said baffle system is adapted and arranged such that it can rotate within said container by drivi n said at least one magnet by said second magnetic driving means, and wherein said first magnetic driving means is arranged below a bottom surface of said container and wherein said second magnetic driv ing means is arranged next to and adjacent to a side wall of said container.

2. A mixing system according to claim 1 , wherein said container comprises at least one opening for receiving and removing substances at its upper side.

3. A mixing system according to claim 1 or 2, wherein said first region of said container lies within the lower region of said container, said lower region being the region below the level defined as 80% of the container height.

4. A mixing system according to any of the previous claims, wherein said baffle system is adapted to have its baffles not extend into said first region.

5. A mixing system according to any of the previous claims, wherein the relative surface area of a main surface of each of said baffles with respect to the surface of a maximal cross-sectional surface area of said container is above 5%.

6. A mixing system according to any of the previous claims, wherein said second region lies within the upper halve of said container.

7. A mixing system according to any of the previous claims, wherein a longitudinal direction of said baffles is oriented substantially vertically within said container, and wherein said main surface of each of said baffles is oriented substantially perpendicular on said rotation direction, and wherein said baffles extend from a lower level up until an upper level, over a distance larger than 30% of the useable container height.

8. A mixing system according to any of the previous claims, wherein said baffle system is arranged such that, for each baffle, a spacing exists between an external rim of said baffle and an inner wall of said container, said external rim being the rim directed towards said inner wall of said container.

9. A mixing system according to any of the previous claims, wherein said each of said baffles extends i nto a lower peripheral region of said container.

10. A mixing system according to any of the previous claims, wherein said baffle system is adapted for being configurable i n at least a reduced volume state or ull volume state, and wherein said container comprises a container opening for receiving and removing substances, said baffle system in said full volume state not being removable from said container through said opening, while being removable through said opening i n said in reduced volume state.

1 1 . Λ mixing system according to any of the previous claims, wherein each of said baffles comprises at least one magnet.

1 2. A mixing system according to any of the previous claims, wherein said first magnetic driving means comprises one or more magnets which are arranged such that they can be driven and rotated along an longitudinal axis of said container around and along an external side wall of said container at a height corresponding to said at least one magnet within said baffle system.

13. A mixing system according to any of the previous claims, further comprising a control means for controlling a relative rotation speed and/or relative rotation direction of said first and said second magnetic driving means.

14. A mixing system according to any of the previous claims, wherein said bat tle system further comprises a low-friction guiding means for guiding said magnetic stirri ng bar in its rotational movement when the position of said magnetic stirri ng bar would move upwardly i n said container u until a predetermined level, whi le blocking any further upward movement of said magnetic stirring bar within said container, and substantially independent on the rotational movement of said bat tle system.

15. A method for stirring at least one substance in a container, comprising magnetically driving a rotational movement of a magnetic stirring bar arranged within the container; wherein the method further comprises magnetically driving a rotational movement of a baffle system, the baffle system positioned within the container and comprising a plurality of baffle planes for directing a flow of substances within the container, said baffle system comprising at least one magnet.