The invention relates to a particle mixture and the stabilization of these particles in the mixture.
For protecting articles, such as e. g. documents of value, high-quality branded goods, etc. against forgery, frequently luminescent substances are used. These substances are typically processed in the form of powdered pigments, like described in EP 0 659 935 A2.
To increase protection from forgery it was suggested in WO 00/71363 to use mixtures of several luminescent substances, in particular also as to be able to produce codings. The coding can e. g. consist in the different luminescent substances being present in different amounts in the mixture.
Furthermore WO 02/078964 discloses a color coding for an object, wherein particles, which have different colors and which are not perceptible to the naked human eye, form a coding.
For the user it is decisive that the coding is uniform throughout the mixture and does not change within the mixture.
Particularly during the transport of larger packaging units from the producer to the customer there is frequently the problem that particle mixtures, which contain e. g. particles with different diameters, are segregated by jarring movements, since the smaller particles tend to migrate in the direction of the bottom of the packaging, whereas the bigger particles accumulate on the surface.
Proceeding from this state of the art, it is the problem of the invention to minimize or to prevent the segregation of powdered mixtures of different particles.
The solution to this problem can be found in the independent claims. Developments are subject of the subclaims.
According to the invention a particle system is provided, which comprises a container and a particle mixture disposed in the container. At least a part of the particles in the mixture differs in at least one measure from the rest of the particles, wherein the container has at least one means which essentially prevents the spatial movement of the particles relative to each other.
In particular in the case of a mixture in which the homogeneous distribution of particles differing from each other is important, the particle system according to the invention ensures that this distribution is stabilized.
“Measure” within the terms of the invention means any physical and/or chemical parameter which furthers a segregation of the particle mixture. In particular, this is the shape, the weight, the size, the density, the electrostatic charge and/or the surface roughness of the particles.
In the case that for example particles of different sizes are mixed homogeneously, these particles will be arranged by jarring movements of the container in such a way that smaller particles migrate toward the bottom of the container, and the bigger particles accumulate on the top. Without any counter measures, the result when viewing the total amount is thus an inhomogeneous distribution of the particles of different sizes.
Also particles which differ in regard of weight or of surface roughness exhibit a similar segregation tendency, i. e. heavier or smoother particles tend to move toward the bottom of the container in comparison to the lighter or rougher particles.
In addition to powdered particles, the invention also relates to dispersed particles. These particles are preferably powdered particles. Particularly preferably they are pigments. Very particularly preferably the particle mixture comprises luminescent substances.
Advantageously, the luminescent substances are inorganic substances such as rare-earth doped host lattices, such as described in WO 2002/070279.
In particular the luminescent substances are a mixture of chemically and/or physically differentiable luminescent substances. The substances are chemically and/or physically differentiable e. g. if they have different chemical formulas, different lattice structures or different spectra.
In an embodiment according to the invention a coding is produced on the basis of the differentiability of the particles in the mixture. This coding can for example be based on the presence or absence of certain substances or also on the different concentration ratios within the mixture. It is also conceivable to produce the coding on the basis of the spectral properties of the different substances.
For the particles preferably D99<50 μm, particularly preferably D99<20 μm, applies. In particular it applies for the particles to be incorporated in paper that D99<20 μm, and for particles which are to be used in printing that D99 is 6 to 10 μm.
The container is a typically used transport container for free-flowing cargo. These are for example plastic drums, metal drums, plastic sacks, etc.
According to the invention the container has at least one means which essentially prevents the spatial movement of the particles relative to each other. This means that the particles in the mixture do not change their spatial arrangement in relation to each other, in particular this means that the means essentially prevents a segregation of the particle mixture or stabilizes a homogeneous distribution of the particles in the mixture.
In an embodiment according to the invention the means produces overpressure or underpressure in the container in which the particles are disposed. Preferably, a suitable valve is used for this purpose. For producing overpressure preferably a pressure cushion is inserted in the container.
Alternatively it is possible according to the invention to divide the particle mixture into partial amounts and to separate those by suitable means.
The means for a spatial separation of the partial amounts are e. g. several separate packaging units, in which the partial amounts are each packed individually. As separate packaging unit e. g. small plastic sacks, in which the mixture is sealed, can be used.
Alternatively the particle mixture can also be filled into a tubular structure. This structure is placed in the container in a meandering shape. This structure preferably additionally has separate chambers and optionally a pull thread.
In an alternative embodiment at least one partition bottom and/or a partition wall is disposed in the container, thereby restricting the freedom of movement of the particles. The more partition walls and/or partition bottoms are used, the stronger the freedom of movement of the particles is restricted and hence the segregation is prevented.
In a further embodiment according to the invention an adhesive, preferably a water-soluble adhesive, is used as means to press the particles along with the adhesive so as to form a granulate material. Optionally the adhesive can be additionally activated by a temperature treatment. The dimensions of the pressed granular material are preferably in a range of 1 to 5 cm. Instead of the adhesive also a water-soluble PVA paste can be used. In a particularly preferred variant an additive is added, which disintegrates under the generation of gas upon contact with solvents and thus facilitates the dissolution of the granular material. For example NaHCl3 can be used for this purpose.
As a further alternative, instead of pressing, the particles can also be extruded into a polymer, preferably a water-soluble polymer.
It is also conceivable to incorporate the particles in a paste for stabilizing the mixture.
According to the invention also a method for producing an inventive particle system is provided.
Further embodiments and advantages of the invention will be explained in the following with reference to the Figure. The proportions shown in the figure do not necessarily correspond to the relations existing in reality and serve mainly to improve clarity.
The figures are described as follows:
a, b connection elements,
The packaging units preferably have a capacity of approx. 100 g to 5 kg particles. The number of packaging units depends on the size of the container, but should preferably be chosen in such a way that the space of the container is filled as completely as possible.
a shows an example of a partition wall in the form of a connection element.
The simultaneous use of partition bottoms and partition walls is most advantageous. In this case the filling is carried out in such a way that first a layer of connection elements, as schematically shown in
In a variant which is particularly easy to realize the pressure cushion 20 and the valve 19 can be omitted. In this case the restriction of the freedom of movement of the particles is achieved by filling the container 17 up to its edge and closing the container cover flush with the edge. Within the container there is thus preferably no free space which would allow the particles to move.
Number | Date | Country | Kind |
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10 2004 052 151.4 | Oct 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP05/11397 | 10/24/2005 | WO | 00 | 10/26/2007 |