DE102011119939A1 - Method of making a composite, the composite and the use of the composite to make certain products - Google Patents

Abstract

The present invention discloses a process for the production of a composite material by means of fluidized bed technology, in particular by granulation in a jet bed installation, and hot pressing, wherein the composite material consists of at least a first material fraction A and at least one polymer or biopolymer and the method comprises the steps of: generating a fluidized particle layer consisting of the at least first material fraction and a fluid stream, injecting a solution of at least one solvent and the at least one polymer (biopolymer) or a melt of the at least one polymer into the fluidized bed, granulating the at least first material fraction A in combination with the at least one polymer a granulate and pressing the granules with heat, wherein the granules in a temperature range above a room temperature and below a decomposition temperature of the at least one polymer heated w ill.

Description

1. Field of the invention

The present invention relates to a method for producing a composite material by means of fluidized bed technology, in particular spouted bed granulation, and hot pressing, wherein the composite material consists of at least a first material fraction and at least one polymer or biopolymer. Furthermore, the present invention relates to the composite materials produced by the above-mentioned method and to the use of these composite materials for the production of certain products.

2. Background of the invention

Known composites often consist of a mixture of, for example, ceramic particles and / or metal particles and at least one polymer. The ceramic particles and the metal particles may consist of different ceramics and different metals and also have different particle size distributions, average particle sizes and particle shapes.

The properties of the composite are influenced by the proportions of material processed in the composite. For example, for many applications, a high proportion of ceramics is sought in composite materials, since, for example, the modulus of elasticity and hardness increase with increasing ceramic content. By a certain proportion of metal particles are also the typical. Properties of metals, such as good plastic deformability, high strength and high breaking strength at least partially transferred to the composite material, so that when a mixture of ceramic and metal particles in the composite, a leaning property relationship is formed.

The particles of material fractions, such as ceramic and / or metal, in the composite are bonded together using one or a mixture of polymers. Structural ceramics as well as functional ceramics are used in the ceramic material fraction in the composite material. While structural ceramics impart certain mechanical properties to the composite, such as strength, hardness, thermomechanical and chemical resistance, functional ceramics may influence other physical properties of the composite. Examples of structural ceramics are Al ₂ O ₃ , ZrO ₂ and an example of a functional ceramic is lead zirconate titanate (PZT). Also, lead-free piezoceramics and polymers such. As potassium-sodium niobate (KNN) or ferromagnetic ceramics and metals are preferred.

Achieving high ceramic levels and adjusting the polymer content in composites by known methods, such as blending (calendering, kneading), extrusion, and ultrasound, is difficult for small particle sizes below 50 microns. The addition of the particles to the polymer melt or polymer solution often leads to segregation of the polymer and the particle phase and, in the case of particle size distributions, to segregation. Furthermore, either due to the rapidly increasing viscosity in the suspension or melt with the ceramic component, sufficiently high ceramic fill levels in the later composite material can not be achieved or such mixtures with a ceramic component can not be used for small particle sizes, as for example in the vibratory compacting method.

It is therefore an object of the present invention to provide an alternative to the prior art manufacturing method for a composite material, with which the respective components can be adjusted within very wide limits and independently and high fill levels of the respective material fraction in the composite can be achieved. In particular, the invention discloses a manufacturing route for achieving very high ceramic and / or metal levels in a ceramic-metal-polymer composite. This is achieved, as further explained below, by the combination of granulation, in which a material fraction is encased by another material fraction, and hot pressing of the granules produced in this way under high pressure.

3. Summary of the present invention

The above object is achieved by a method for producing a composite material by means of spouted bed technology and hot pressing according to independent claim 1. Furthermore, the present invention provides a compressed composite according to independent claims 8, 10 and 11 and the use of this compressed composite in certain products according to independent claim 12. Further advantageous embodiments and further developments of the present invention are evident from the dependent claims, the following description and the attached drawings.

The inventive method comprises the production of a composite material by fluidized bed technology, in particular spouted bed granulation and hot pressing, wherein the compressed composite material consists of at least a first material fraction and at least one polymer. The method according to the invention comprises the following steps: producing a fluidized particle layer consisting of the at least first material fraction and a fluid stream, injecting a solution of at least one solvent and the at least one polymer or a melt of the at least one polymer into the fluidized bed, granulating the at least first Material fraction in combination with the at least one polymer to a granulate and pressing the granules under heat, wherein the granules is heated in a temperature range above a glass transition temperature and below a decomposition temperature of the at least one polymer, to form a composite material.

Spouted bed apparatuses and thus generally spouted bed technology are known in the art. They are for example in DE 100 04 939 C1 and WO 2010/028710 A2 described. Within the spouted bed technology, fluidization of a first material fraction takes place first. This is understood as meaning the displacement of a material fraction consisting of solid particles by an upward fluid flow into a liquid-like state. This fluid flow is realized for example by an air or more generally a gas flow. The fluidization takes place, in particular in the fluidization of small particles (<50 μPm), preferably in a jet bed system, but in principle any structure is suitable with which a fluidization of the particular desired particle fraction can be achieved and an injection can take place.

In this fluidized state, the particles of the first material fraction are suspended by the fluid flow, or they make a circulating movement in the apparatus, forming a vortex or spouted bed state. In this way, the particles of the first material fraction are present at least in the spray zone of the nozzle separated from each other, so that they are accessible from the outside around.

To externally coat these particles of the first material fraction in the fluidized bed with polymer droplets, the solution of the at least one solvent for the at least one polymer or the melt of the at least one polymer is sprayed into the fluidized bed.

For the production of granules which can be processed (pressed) into materials filled to a higher degree (> about 60% by volume), it is likewise preferred to introduce at least one further material fraction into the process of granulation in addition to the first material fraction. This at least one further material fraction is preferably suspended in the polymer solution or polymer melt or first suspended in the solvent with subsequent dissolution of the polymer in the suspension, and then sprayed into the fluidized bed and / or in combination with the first material fraction by the fluid flow in the fluidized bed swirled. It is preferred that the material fractions used have different mean particle sizes, in order to increase in this way the degree of filling of the compressed composite material.

After the granules consisting of the at least first material fraction in combination with the at least one polymer is present, this granulate is processed under pressure and / or temperature, preferably compressed with heat. Thus arises from the granules of the composite material. In order not to decompose the polymer during the pressurization under heat, only heat is supplied in a temperature range below a decomposition temperature of the at least one polymer. The pressing temperature is preferably used in a range between a glass transition temperature of a polymer and a decomposition temperature of a polymer, preferably in the range of a typical processing temperature depending on the polymers involved.

As already mentioned above, at least one second material fraction and optionally also a third and / or further material fractions are preferably used in addition to the first material fraction for the production of the composite material. As materials for the material fractions used, each type of ceramics, metals, metal alloys, prestructured particles (for example ceramic-metal, ceramic-polymer, metal-polymer, ceramic-metal-polymer) and, in principle, many types of polymers, for example Thermoplastics, thermosets and epoxy resins, are used. The particles may be spherical, non-spherical, angular, platy, oblong, acicular, or regularly shaped (e.g., square). The first material fraction consists, for example, of ceramic particles of a first mean grain size or of metal particles of a first average grain size or of a mixture of such ceramic and metal particles. The second material fraction preferably consists of ceramic particles of a second average particle size or of metal particles of a second average particle size or of a mixture of such ceramic and metal particles. As is apparent from the selection of the material fraction described above, the production method according to the invention is preferably suitable for the production of a ceramic-ceramic-polymer composite, a ceramic-metal-polymer composite, a metal-metal-polymer composite, a ceramic Polymer or a metal-polymer Composite. Furthermore, it is preferred to produce a polymer-polymer composite material in which, for example, one material fraction consists of an epoxy resin and the other material fraction consists of a thermoplastic.

In summary, ceramic and / or metal-polymer composites are produced by fluidized bed granulation and hot pressing. These are used in the manufacture of certain products. Depending on which properties the composite material should have, both the materials and their volume fractions in the composite material can be adjusted in a targeted manner. For example, for many applications, it is preferred to achieve a high ceramic content in the range of 50-90 vol.% And a polymer content in the range of about 1-50 vol.% In the compressed composite. For this purpose, a first and a second material fraction of ceramic particles are processed using the spouted bed technology. The ceramic particles of the second material fraction are preferably at least a factor of 2, more preferably at least a factor of 10 smaller than the ceramic particles of the first material fraction. These particle sizes open up the possibility that the small ceramic particles with the help of the at least one polymer as an agent on the surface of the large ceramic particles deposit, so that granules of large and small ceramic particles formed by the polymer. The injection of the polymer solution or the polymer melt - in which at least one material fraction is suspended - in the fluidized bed of a jet bed apparatus ensures that the at least one polymer droplets or in a relatively thin layer and evenly deposited on the ceramic and metal particles. A possible process variant is also to suspend a polymer in a liquid instead of dissolving it, and optionally to suspend a material fraction in this polymer suspension. The polymer suspension then becomes fluid during hot pressing and performs a similar function to the polymer solution described above. Thus, a polymer solution refers to at least one polymer dissolved in a solvent. A polymer suspension refers to at least one polymer suspended in a liquid. Both in the polymer solution and in the polymer suspension, at least one material fraction can be suspended in order to subsequently be able to produce a granulate in the spouted bed apparatus. The term polymer solution in the further description is exemplary of a polymer solution and a polymer suspension.

The effects described here on ceramic particles of course also take place in the same way when using other materials as a material fraction, for example, when using metals or the use of existing composites as a material fraction.

According to another alternative of the present invention, there is provided a compressed composite comprising at least a first material fraction of ceramic particles, at least a second material fraction of metal particles, and at least one polymer such that the composite material has a ceramic content X in the range of 50 to about 95% by volume. preferably from 60 to about 80% by volume, a metal content z in the range from 0 to 50% by volume and a polymer fraction Y in the range of Y = (100 - X - Z)% by volume.

In the preferred range of 64 vol.% To about 85 vol.% Of the ceramic fraction in the composite, the material composition can be varied. In this case, preferably the pressing pressure is chosen to be sufficiently large. However, it is also possible to realize ceramic fill levels of less than 64% by volume in the composite material, which is of interest for certain applications, such as, for example, filter materials. In this way, a desired porosity is set specifically, which forms the starting point or the practical basis for the later use of the composite material. A ceramic filling level <64 vol .-% can be realized by a correspondingly low selected pressing pressure. At very high pressures, the filling level does not increase with increasing pressure. However, with falling reduction of the pressing pressure, the degree of filling decreases with the pressing pressure, and the more so, the smaller the pressing pressure is selected. The lowest possible resulting degree of filling is given by the bulk density of the agglomerates of the first material fraction. In addition to or instead of the pressing pressure, the porosity of the composite material can also be adjusted by using a grain size for the material fraction suspended in the polymer solution, which is slightly smaller than the grain size of the first material fraction, for example ceramic. This results preferably in a particle size ratio of first to second material fraction of <10.

4. Brief description of the accompanying drawings

The preferred embodiments of the present invention will be explained in detail with reference to the accompanying drawings. Show it:

1 a schematic representation of a preferred embodiment of a jet bed plant for fluidized bed granulation,

2 a schematic representation of a preferred embodiment of the hot pressing and

3 a flow diagram of a preferred embodiment of the manufacturing method for a composite material.

5. Detailed Description of the Preferred Embodiments of the Present Invention

The present invention discloses the production of a composite material using spouted technology and hot pressing. In particular, granules G are produced from one or more material fractions A, B, C, D, preferably ceramic and / or metal, and at least one polymer P as starting materials in a known spouted bed system. In this granulate G, both the proportions of the material fraction or material fractions used and the polymer content can be adjusted. After granulation, the granules G are hot-pressed to the composite material. Despite the heat supplied to the granules G during pressing, the hot pressing temperature does not exceed a decomposition temperature T _Z of the polymer used, so that the polymer content is retained in the granules G and the resulting composite material.

Based on the use of spouted technology, for its more constructive details on DE 100 04 939 C1 . DE 103 22 062 A1 . DE 10 2006 011 391 and WO 2010/028710 A2 A high ceramic and / or metal content of the granulated with the at least one polymer P particles of the one or more material fractions A, B, C, D is achieved, so that in the later composite material after eliminating the void volume by pressing a high Filling degree of the introduced material fractions A. B, C, D preferably over 70 vol .-%, can be achieved. The use of the spouted technology also ensures a very good mixing of the components involved and thus a high degree of homogeneity in the later material.

Furthermore, it is advantageous that the thickness of the polymer layer forming on the particles of the material fraction (s) can be influenced and therefore the polymer content in the later composite material can be selectively adjusted. According to the use of ceramic, metal and composite particles in combination or alone with a polymer content, a composite material whose properties can be determined by the degree of filling of the material and polymer fraction. Accordingly, the polymer content of the composite material produced by jet technology can be controlled by varying the amount of polymer supplied.

The layer thickness of the polymer layer on the particles of the at least first material fraction can preferably be adjusted within wide limits by means of the production method according to the invention. The layer thickness takes values in the range of a few nanometers, while no second material fraction, a high dilution of the polymer solution, polymer melt or polymer suspension and a good wetting behavior of the polymer solution, polymer melt or polymer suspension on the first material fraction is present, and up to several hundred micrometers or even Millimeters. For a small layer thickness, the polymer solution, polymer melt or polymer suspension is preferably diluted, so that the resulting layer thickness is essentially determined by the interface properties between wetting liquid and particle surface. For a thick layer, increase the concentration of the polymer in the solution, the melt or the suspension and increase the total amount of polymer solution or polymer melt or polymer suspension to be sprayed. In this way, the layer thickness of the polymer used can be easily adjusted within these wide limits and thus adapted to the gap volume between the particles of the at least one material fraction.

For many applications, a composite material with, for example, a high proportion of ceramic is sought, whose mechanical properties, such as modulus of elasticity and hardness, also increase with increasing ceramic content. In this case, as dense a packing of ceramic particles in the compressed composite material is sought, which just contains just enough polymer that the remaining gap volume between the ceramic particles is preferably completely filled by the polymer portion of the composite material. In this way, according to a preferred embodiment of the present invention, pressed composite materials without porosity are produced.

A proportion of polymer in the composite which exceeds the void volume between the particles of the material fractions of the composite reduces the degree of filling of the material fraction or material fractions, such as ceramic, in the composite, while a polymer fraction below the available void volume in the composite restricts the residual porosity in the composite Episode has. Since a polymer fraction above or below the gap volume available in the composite material between the particles of the material fraction / material fractions can have a negative influence on mechanical / functional properties of the composite material, it is preferable to optimally adapt the polymer fraction to the void volume available in the composite material Particles of the material fraction or material fractions sought. This optimum adaptation of the polymer content leads to improved mechanical properties. Namely, the amount of polymer can For example, it can be adjusted to exactly fill the void volume of the processed material fractions after pressing. As a result, the polymer content does not cause a reduction in the degree of filling, and yet a non-porous structure is formed, so that the formation of cracking centers is made more difficult. Preferably, the proportion of polymer is adjusted by the amount or concentration of polymer solution / polymer melt in which a material fraction may otherwise be suspended.

The preferred composite material is composed of at least a first material fraction A and a polymer fraction. The first material fraction A consists of ceramic or polymer or metal particles or of particles of a pre-structured composite material. The particles of the first material fraction A preferably have a first mean grain size and a first grain size distribution.

The particles of the first material fraction A form the so-called bed material 10 which is fluidized in the vortex or spouted bed apparatus (SI). One on the bedding 10 against gravity directed fluid flow 20 , preferably air stream, generates a stable turbulence / circulation of the particles of the first material fraction A.

With the help of a heater, the fluid flow becomes 20 , prefers the air, heated to a drying process within the fluidized bed 30 to support. The targeted heating of the fluid flow 20 is adjusted depending on a vapor pressure of a solvent to be evaporated of a polymer solution (see below). In this case, the temperature range of the fluid flow 20 , preferably 10-100 ° C, such that, with at least partial to complete evaporation of the solvent of the polymer solution to a coating of the particles of the bed material 10 comes.

Preferably, as a bed material 10 the first material fraction A mixed with one or more further material fractions B (SII). On this basis, a ceramic-ceramic or ceramic-metal or metal / ceramic-prestructured particle mixture formed as bed material 10 in the spouted bed apparatus in the fluidized bed 30 is swirled.

In addition to the mixture of different materials, it is advantageous to achieve high degrees of filling when the different material fractions have different mean particle sizes. This helps to achieve a high degree of filling of the material fraction / material fractions in the composite material to be produced.

To produce the composite material, a solution of at least one solvent for at least one polymer and the at least one polymer or polymer melt in the fluidized-bed apparatus is introduced into the fluidized bed apparatus 30 made of bedding 10 injected (SVI). By injecting the polymer solution or polymer melt in the form of fine droplets of the fluidized bed 30 fed, so that the fine droplets of the polymer solution or polymer melt on the particles of the fluidized bed 30 of the bedding material 10 deposit.

For the polymer solution, the at least one polymer P is dissolved in a corresponding solvent L. It is further preferred to dissolve a plurality of polymers in corresponding more or only one solvent L. It is also preferred to prepare a polymer melt from a plurality of polymers (SIII). The coating process can also be carried out in succession with different polymer solutions or polymer melts, in which in turn different other material fractions can be dissolved in each case.

According to a preferred embodiment of the production method according to the invention, a further material fraction C is added to the polymer solution or polymer melt (SIV). This results in a polymer solution / polymer melt in which a second material fraction is suspended. Similar to the provision of the bedding material 10 Preferably, a further or a plurality of material fractions D are added to the polymer solution / polymer melt (SV). The addition of further material fractions depends on the properties to be achieved in the later composite material.

As second C and further material fractions D ceramic, metal and / or polymer particles and particles of composite materials are used alone or in combination. The particles of the second C and of the further material fractions D have a second average particle size which is smaller than the mean particle size of the particles of the bed material 10 , Preferably, the particles of the bed material 10 and the particles of the second C and further material fractions D have a size ratio in the range 4-10: 1 :, preferably 6-10: 1 and even more preferably from about 10-100: 1. It is also preferable to select an even larger size ratio of about 100: 1 up to about 100,000: 1. Accordingly, the particle sizes of the bed material 10 preferably in the range of. 10-30 microns and the particle sizes of the second C and other material fractions D preferably in the range of 0.2-5 microns. Depending on the requirements of the composite to be produced, larger or smaller average particle sizes can also be used the individual above-mentioned material fractions A-C are used.

In a further method step SVI (cf. 3 ), the polymer solution / polymer melt, in which at least a second material fraction is suspended in the fluidized bed 30 made of bedding 10 injected. The injection is preferably carried out via a two-fluid nozzle. The spraying rate during injection depends on the selected construction of the jet bed apparatus and a vapor pressure of the solvent L used for the polymer P. According to a preferred embodiment of the present production process, the spray rate is about 10 g / min.

During injection (SVI), the polymer solution / polymer melt or suspension is in the form of small droplets in the fluidized bed 30 distributed. These droplets are deposited on the particles of the bed material 10 so that the particles of the second C and further material fractions D as coating particles for the particles of the bed material 10 serve. The at least one polymer in the polymer solution serves as adhesion promoter between particles of the bed material 10 and coating particles as soon as the solvent L has evaporated from the droplets of the polymer solution.

Depending on how much polymer solution, polymer melt or polymer suspension in the fluidized bed 30 is injected more or less coating particles and polymer on the particles of the bed material 10 from. This process is schematically at the bottom right of 1 illustrated. The proportions to be used of the introduced into the spout apparatus materials depend on each other as follows. The optimum amount of bedding 10 , which is fluidized in the fluidized bed, is determined by the geometry of the used jet bed system. According to a preferred embodiment, this amount is about 200-400 g of ceramic particles. In addition, at this point in the production process, it is also possible to use metal particles, for example silver or copper, via the above-mentioned suspension of the fluidized bed 30 respectively. To achieve an optimum packing density with a bimodal particle distribution, the optimum ratio of large particles to small particles, ie of particles of the bed material, is 10 and the coating particles of the suspension, about 60:40 vol.%. This results in the amount of small particles in the suspension. In doing so, one should preferably note that the effective amount of bedding material 10 slightly lower than the amount of bed material fed into the spouted apparatus 10 , The reason is that during the manufacturing process there are certain losses of bed material 10 can come. These losses occur, for example, due to the adhesion of the particles of the bed material 10 on the walls of the jet bed apparatus as well as through the discharge of smaller particles of the bed material 10 over the fluid flow 20 from the fluidized bed 30 on.

The amount of dissolved polymer P in the polymer solution is determined by the fact that the void volume between the compressed particles in the composite material remaining after a hot pressing process (see below) is preferably completely filled with the polymer P or a plurality of polymers. The amount of solvent for the polymer P is again given by the amount of polymer P to be dissolved. The amount of the solvent is also preferably chosen so that the viscosity of the polymer solution or of the suspension of polymer solution and second / further material fractions is sufficiently low for injection ) C; D is guaranteed.

The pH of the suspension of polymer solution and second / further material fraction (s) C; D is adjusted by addition of any acid or base such that it deviates from the isoelectric point of the ceramic particles preferably used in the second material fraction C in order to stabilize the suspension and to avoid agglomeration of the ceramic particles in the suspension. Adjusting the pH is especially for small particle sizes, i. H. Particle sizes <5 microns, of importance, since there agglomeration occurs increasingly. The distribution or dispersion of the particles of the second material fraction C or further material fraction D in the suspension is carried out in an ultrasonic bath according to an embodiment of the present production method. Of course, other known methods are equally applicable for this purpose, which serve for distributing particles in a suspension.

By coating the particles of the bed material 10 in the fluidized bed 30 and drying or evaporating the solvent for the polymer P using the fluid stream 20 the fluidized bed 30 granulation takes place in the fluidized bed 30 existing material fractions A, B, C, D by means of the / the polymers (SVII). The resulting granulate G is subsequently pressed, preferably hot-pressed while supplying heat without reaching the glass transition temperature of the polymer (s), which in 2 is illustrated schematically.

The pressing process preferably takes place in a pressure range of 100 MPa to 1 GPa and preferably at a pressing temperature of (T _G + 10 ° C) to (T _G + 100 ° C). Pressure and temperature, as explained below, can also be chosen differently within very wide limits as required. at Polymers whose glass transition temperature is so low that their optimum processing temperature during the pressing process not by heat, but by heat dissipation, ie cooling, is reached, the pressing temperature can also be below room temperature. Therefore, the term "hot pressing" is to be understood as meaning that, in order to achieve optimum processing of the polymer (s) during pressing, an amount of heat is added or removed, the polymer (s) are therefore warm or cold relative to a room temperature of, say, 20 ° C be pressed.

The hot pressing of ceramic-polymer composites into composites having high packing densities (typically> 64 vol%) is preferably at a pressure and temperature sufficient to press the granules into the closest possible random packing structure. A further increase in the pressing pressure then causes only an elastic deformation of the ceramic particles. In particular, the pressure should be chosen so large that the particles of the injected (second or further) material fraction, which redistribute the fluidized first material fraction, are pressed into the void volume of the material particle fraction which is larger in terms of particle size during the pressing process. Preferred pressing pressures for an example process described are between 50 MPa and 1 GPa. Upwards, the pressing pressure is limited by possible damage in the material, which results from an excessive elastic deformation of the ceramic particles and subsequent relief in the material. Down there is no limit. In the case of ceramic-metal-polymer composite materials with a metal content, in turn, a significantly higher compression pressure may be useful, which is determined by the (possibly desired) plastic deformability of the metal particles. In order to achieve lower fill levels or a higher polymer content, it is also preferred to choose the pressing pressure much lower, for example, only a few 10 MPa or even smaller. In general, the pressing pressure is to be matched to the desired properties of the composite material. Since both very highly filled, low-filled, and also porous composite materials can be produced with the described invention, the respective suitable compression pressure in a wide range, namely of approximately 0 Pa - thus a highly porous composite produced only by heat during hot pressing - to several GPa - thus a highly filled composite material with possible plastic deformation of contained metal particles. The appropriate pressing pressure also depends on the pressing temperature used.

As mentioned, the pressing process preferably takes place with the supply of heat to the granulate G to be compacted. Based on the heat supply, a temperature T is reached which is preferably above a glass transition temperature T _G or melting temperature T _S and below a decomposition temperature T _Z of the polymer / polymer P used in the granulate G. In this context, it is further preferred that a temperature range above a glass transition temperature T _{G of} the polymer P used is set in the granules G. If a polymer composed of several components is used (eg, thermosets), then the lower limit may be given by the glass transition temperature and / or melting point of the individual components. It has also been recognized that the appropriate compacting pressure depends on the viscosity of the polymer P in the granules G under pressure loading, on the particle composition of the material fractions in the granules G, such as size, shape and size distribution of the particles, as well as on the desired properties of the compacted composite material.

Preferred execution of a batch process for the composite material

• 1) Man wählt aus zwei Partikelgrößen der ersten und zweiten Materialfraktion ein Partikelgrößenverhältnis dieser Partikel und ein Mengenverhältnis dieser Partikel aus, so dass sich eine Packungsdichte von 80 vol% bei dichtester zufälliger Packung dieser Partikel einstellt. Dies wird vorzugsweise aus empirischen Korrelationen gewonnen. Ein typisches Mengenverhältnis, bei dem sich hohe Packungsdichten im Bereich von 80 vol% erreichen lassen, liegt im Bereich 60 vol% große Partikel und 40 vol% kleine Partikel. Bei der Verwendung des gleichen Materials für die erste und zweite Materialfraktion ist dies auch deren Massenverhältnis.
• 2) Man kennt das optimale Schüttvolumen für die erste Materialfraktion, die verwirbelt wird. Dieses ist durch die Geometrie der Strahlschichtanlage (Größe der Prozesskammer) vorgegeben. Damit kennt man auch die Masse der ersten Materialfraktion, die während des Granulationsvorgangs einsetzbar ist. Man wählt zudem bevorzugt eine gewünschte Partikelgröße für die erste Materialfraktion.
• 3) Aus 1) und 2) berechnet man die Masse und Partikelgröße derjenigen Materialfraktion, die eingedüst wird. Damit sind die beiden Mengen an Partikeln, die im Granulationsvorgang eingesetzt werden, bekannt. Unter Kenntnis der Materialdichten der beiden Keramikfraktionen bestimmt man das Gesamtvolumen an Keramikpartikeln.
• 4) Unter der beispielhaften Annahme, dass dieses Volumen 80 Vol% des Verbundwerkstoffs ausmachen soll, löst man eine Menge an Polymer im Lösungsmittel oder stellt eine Polymerschmelze oder Polymersuspension her, deren Volumen genau 20% des Keramikvolumens beträgt (Umrechnung aus Gewicht über Materialdichte des Polymers).
• 5) In dieser Polymerlösung/Polymerschmelze/Polymersuspension suspendiert man die zweite Materialfraktion, und mit dieser Suspension beschichtet man die Partikel der ersten Materialfraktion im Strahlschichtprozess. Daraus resultiert dann eine entsprechende Schichtdicke.

The following description of an exemplary batch process illustrates how the amounts of the individual material fractions and hence also the layer thickness of the polymer layer result from the respective requirements for the composite material. The layer thickness of the polymer layer is calculated as follows from the desired composition of the composite material and the resulting volume fractions of the individual material fractions. For example, if a composite material with 80 vol% ceramic and 20 vol% polymer is desired, then dissolve just as much polymer in the solvent that the polymer content is 20 vol%. This is preferably realized in a batch process as follows.

• 1) It is selected from two particle sizes of the first and second material fraction, a particle size ratio of these particles and a ratio of these particles, so that sets a packing density of 80 vol% at the closest random packing of these particles. This is preferably obtained from empirical correlations. A typical ratio, which can reach high packing densities in the range of 80 vol%, is in the range of 60 vol% particles and 40 vol% small particles. When using the same material for the first and second material fractions, this is also their mass ratio.
• 2) One knows the optimal bulk volume for the first material fraction, which is vortexed. This is determined by the geometry of the spouted bed system (size of the process chamber). Thus one knows also the mass of the first material fraction, which during the Granulationsvorgangs can be used. It is also preferable to choose a desired particle size for the first material fraction.
• 3) From 1) and 2) calculate the mass and particle size of the fraction of material that is injected. Thus, the two quantities of particles used in the granulation process are known. Knowing the material densities of the two ceramic fractions, one determines the total volume of ceramic particles.
• 4) Assuming that this volume should account for 80% by volume of the composite, one dissolves an amount of polymer in the solvent or produces a polymer melt or slurry whose volume is exactly 20% of the ceramic volume (conversion from weight to material density of the polymer ).
• 5) The second material fraction is suspended in this polymer solution / polymer melt / polymer suspension, and this suspension is used to coat the particles of the first material fraction in the spouted bed process. This then results in a corresponding layer thickness.

It is worth noting that the particle size ratio under point 1), which leads to the desired packing density, represents a lower limit, but could also be chosen to be higher to some extent. If a larger particle size ratio is chosen, but the amount of polymer is not adjusted appropriately, then the presence of the preferably incompressible polymer prevents densification to higher packing densities.

It is furthermore preferred that the polymer coating on the particles of at least the first material fraction can also consist of a plurality of polymer layers applied one behind the other. For this purpose, preferably different polymer solutions / polymer melts / polymer suspensions with in each case other polymers and / or particles suspended therein are injected or sprayed successively or simultaneously into the jet bed apparatus. In this way, preferably three or more different particle sizes are combined.

It follows that, in general, in the production of the composite material according to the invention preferably several granulation stages, each having a different material composition, can be carried out successively. This opens up the preferred possibility of applying various polymers in layers to the particles of the at least one material fraction and then pressing them.

Preferred materials for the production of the composite material

Suitable polymer P is any plastic and also any biopolymer which can be dissolved in a corresponding solvent L or suspended in a liquid or whose melt has a sufficiently low viscosity for injection. Preferably, the polymers P polyvinyl alcohol (PVA) and polyvinyl butyral (PVB) were used, which dissolve in water or ethanol. Biopolymers in this context refer to polymers which consist of biogenic raw materials (renewable raw materials) and / or which are biodegradable. Examples of these are proteins, for which collagen is an example, or peptides, RNA and DNA. Such biopolymers are often referred to as biological macromolecules. The polymers and biopolymers are summarized under the name polymers for ease of explanation.

As material fraction A; B; C; D are all solid substances whose properties are of interest for the composite to be produced and which are present in a suitable average particle size or grain size or can be processed to achieve this average particle size. As examples of ceramics, there can be mentioned Al ₂ O ₃ , TiO ₂ , SiO ₂ , ZrO ₂ , BaTiO ₃ , PZT, KNN, BNT, ZnO, mullite, Fe ₂ O ₃ , hydroxyapatite, calcium phosphate, bioglass. As examples of metals and metal alloys, mention may be made of Cu, Ag, Al, Au, Fe, Si, Cu _x Zn _y , Ni _x Fe _y Ti _x Al _y . The particles of the material fraction A; B; C may have a spherical or non-spherical shape, such as angular, platy, rod-shaped. According to a preferred embodiment of the present production process, platelet-shaped α-Al ₂ O ₃ ceramic particles in the particle size range d ₅₀ = 32-38 μm and irregularly shaped α-Al ₂ O ₃ ceramic particles in the particle size range d ₅₀ = 21-25 μm as bedding material 10 used

As particles of the second (fine) material fraction C, which are suspended in the polymer solution, according to one embodiment, platelet-shaped α-Al ₂ O ₃ ceramic particles in the particle size range d ₅₀ = 1-2 μm and irregularly shaped α-Al ₂ O ₃ Ceramic particles used in the particle size range d ₅₀ = 0.5-5 microns. The polymer used is preferably partially hydrolyzed polyvinyl alcohol with deionized water as solvent and polyvinyl butyral with ethanol as solvent.

Preferred embodiments of the composite

a A homogeneously mixed pore-free ceramic-polymer composite

• i) When using a first material fraction A consisting of ceramic particles of a monomodal particle size distribution in combination with a injected polymer P without further material fraction a composite material with a ceramic content up to about 64 vol .-% in the pressed state can be produced.
• ii) Starting from example (i), a second material fraction C of smaller ceramic particles is mixed with the polymer solution / polymer melt in comparison with the particles of the first material fraction A. The ceramic particles of the second material fraction C are preferably smaller by at least a factor of 10 or more than the particles of the first material fraction A. If one mixes an amount of the second material fraction C of 60-65% by volume. the ceramic particles of material fraction A of the polymer solution, after completion of the manufacturing method described above, preferably obtained a compressed composite material with a 70-90% volume fraction of ceramic.

The ceramic proportion which arises is dependent on the size ratio of the particle classes, the mass ratio of the at least two particle fractions and the particle shape of the material fractions involved, given a sufficiently high pressing pressure and preferably randomly homogeneous mixing of the particle size classes. The respective influence of these factors let you take from literature data. When mixing two spherical particle size fractions can be achieved according to literature data maximum ceramic content of about 87 vol .-%, when mixing three particle size classes corresponding to a maximum ceramic content of about 95 vol .-%. In addition, the influence of the particle shape, as a deviating from the spherical shape particle shape can lead both to a lower and to a - with a special arrangement of the particles - higher ceramic content. When using platelet-shaped particles, under certain circumstances, for example, results in a higher volume fraction.

b) A homogeneously mixed pore-free metal / polymer composite material

By using metal powders instead of ceramic powders for the first A and second material fractions C, the production route described above is transferable to the metal / polymer material system. Due to the slightly different material properties of metal compared to ceramics, the production parameters are, for example, the metal / polymer interface behavior, the changed vortex behavior of the metal particles as bed material 10 in the fluidized bed 30 and to adapt the sedimentation behavior of the metal particles in suspended form in the polymer solution. As a result of the manufacturing process, composite materials with a degree of filling of up to 99.9% by volume of ceramic and / or metal are obtained, which can partly be attributed to the plastic deformability of the metal particles.

c) A homogeneously mixed pore-free ceramic-metal-polymer composite

By using ceramic powder (s) for the first A and of metal powder (s) as the second material fractions C, the above-described manufacturing route is transferable to the ceramic-metal-polymer material system. Due to the different material properties of metal and ceramic, the production parameters are, for example, the fluid behavior of the particles used as bed material 10 in the fluidized bed 30 and to adapt the sedimentation behavior of the particles. According to a preferred embodiment, a composite material is produced which has a ceramic content x of about 64 vol%, a metal content z of about 21 vol% and a polymer fraction y in the range of y = (100-x-z) vol%. It is also preferred to increase the ceramic content with a corresponding reduction of the metal content. It is furthermore preferred to have composites with a ceramic content x in the range of 50 to 85% by volume, a metal content z in the range of 0-50% by volume and a polymer fraction y in the range of y = (100-x-z) vol%.

Due to the plasticity of the metal particles during hot pressing, the addition of metal makes it possible in principle to increase the resulting packing density of the composite to 99.9% by volume. A preferred application is silver as a metal in a ceramic composite denture because silver kills bacteria, for example, when used as a dental filling or dental implant. Another example of a preferred metal is copper.

d) A porous ceramic-metal-polymer composite

The production method of the invention described above can also be used to produce a porous, yet solid filter material. To achieve a large pore volume of the polymer content and the volume fraction of the first A and second material fraction C are kept low. In this context, it is preferred that the second ceramic To omit material fraction C or to use particle sizes which are not so different from the grain size of the fraction A (so-called blocking grain). A volume fraction of the first material fraction A in the composite material can be reduced to a smaller value by reducing the compression pressure during hot pressing of about 64% by volume, so that a compressed preferred composite material having the following composition is obtained:
Ceramic content X = 40-50 vol.% Consisting of the first material fraction A
Polymer content Y = 1-10 vol .-% and
Porosity = 100 - (X - Y) Vol .-%

To assist in producing a porous composite of the above composition, the coated particles become the first material fraction A of the bed material 10 preferably agglomerated during the jet layer process.

For this purpose, the manufacturing process must be modified so that agglomeration occurs increasingly. For example, the temperature in the swirling layer may be reduced and / or the droplet size of the injected suspension may be increased (for example, by reducing the nozzle air flow).

Based on the porous structure of such agglomerates and a resulting low bulk density of these agglomerates consisting of the granules G of the manufacturing process described above can be achieved with a high proportion of porosity in the composite material during hot pressing with low compression pressure (preferably 0-100 MPa) small ceramic components.

Based on the above-described manufacturing method and its preferred embodiments, as well as the various compressed composites further produced by this manufacturing method, it can be seen that the composite method of the present invention uses compressed composites having a fill level of more than 70% by volume of the material fraction used , such as ceramic or metal can be achieved. Thus, a first material fraction A of Al ₂ O ₃ with a particle size of d ₅ 23 ≈ μm and a second material fraction C of Al ₂ O ₃ with a particle size of d ₅₀ 1-2 μm and polyvinyl butyral (PVB) as a polymer were compressed Composite material with a ceramic filling level of more than 75 vol .-%, a porosity <3%, a modulus of elasticity in the range 40-45 GPa, a flexural strength of over 100 MPa and thereby pronounced elastic-plastic behavior achieved with significantly pronounced yield strength before failure , Preferably, two material fractions A; C consisting of ceramic or metal particles with different mean grain size and therefore used with two different ball packages, so that a ceramic or metallic or mixed ceramic-metallic filling degree in the range of 50-90 vol.%, Preferably 65-90 vol .-% becomes.

Furthermore, it is preferable to combine platelet-shaped ceramic particles of a first material fraction A with plastically deformable metal particles of a second material fraction C in the above-described production method so that a volume fraction of the sum of both material fractions A and C in the range of 50-100% by volume, preferably 70-95% by volume.

Possible products or product groups which can be produced by the described method are: dentures and bone substitutes with precisely adapted properties, machine parts (for example gears, seals), artificial stone, kitchen worktops, tiles, dishes, filters, magnetic plastic, high-voltage electrical insulator Dielectric strength, adjustable di- and piezoelectric ceramic-polymer composites, silencers, adjustable ferromagnetic ceramic-metal-polymer composites, multiferroic ceramic-metal-polymer composites. Any products with increased wear resistance. Continuous transitions in plastic to ceramic-polymer-metal composites, which at certain points (eg.

Axle bushings) make the plastic harder and more wear-resistant. The use of biopolymers results in biodegradable environmentally friendly materials.

LIST OF REFERENCE NUMBERS

A

First material fraction

B

Further material fraction

C

Second material fraction

D

Further material fraction

G

granules

L

solvent

P

polymer

F

force

T

temperature

T _R

room temperature

T _G

Glass transition temperature

T _Z

decomposition temperature

10

bed material

20

fluid flow

30

fluidized bed

SI

Swirl bedding material

SII

Complete bedding

SIII

Prepare a polymer solution in a suitable solvent

SIV

Enter a second material fraction C in the polymer solution

SV

Enter a further material fraction into the polymer suspension

SVI

Injecting a polymer solution / suspension or a melt into the fluidized bed

SVII

Granulate

SVIII

hot pressing

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10004939 C1 [0009, 0024]
• WO 2010/028710 A2 [0009, 0024]
• DE 10322062 A1 [0024]
• DE 102006011391 [0024]

Claims (13)

Process for the production of a composite material by means of fluidized bed technology, in particular by granulation in a spouted bed, and hot pressing, wherein the compacted composite consists of at least a first material fraction (A) and at least one polymer (P) and the process comprises the following steps: a) producing a fluidized particle layer ( 30 ) consisting of the at least first material fraction (A) and a fluid stream ( 20 b) injecting a solution of at least one solvent (L) and the at least one polymer (P) or a melt of the at least one polymer (P) into the layer ( 30 ) or a suspension of the at least one polymer (P) in a liquid, c) granulation of the at least first material fraction A in combination with the at least one polymer (P) to form a granulate (G) and d) pressing the granulate (G) under heat in which the granulate (G) is heated in a temperature range above a glass transition temperature (T _G ) and below a decomposition temperature (T _Z ) of the at least one polymer (P). Method according to claim 1, with the further steps: Preparing the solution of the at least one solvent (L) and the at least one polymer (P) or the melt of at least one polymer (P) or the suspension of the at least one polymer (P) and Suspending at least one second material fraction (C) in the solution or the melt or suspension prior to injection. Process according to claim 1 or 2, in which the first material fraction (A) consists of a) ceramic particles or prestructured particles of a first mean grain size or b) metal particles of a first mean grain size or c) ceramic and metal particles. A method according to claim 2 or claim 3 in combination with claim 2, in which the second material fraction (C) consists of a) ceramic particles of a second mean grain size or b) metal particles of a second mean grain size or c) ceramic, metal or pre-structured particles. Process according to claim 3, in which the first material fraction (A) comprises a third material fraction ( 13 ) of ceramic and / or metal particles having a third average grain size. A method according to claim 4, wherein the second material fraction (C) comprises a fourth material fraction (D) of ceramic and / or metal particles of a fourth average grain size. Method according to one of the preceding claims, wherein during pressing a temperature above a glass transition temperature of the at least one polymer is adjusted. A compressed composite material, in particular produced by a method according to one of the preceding claims, comprising at least a first material fraction (A) of ceramic particles and at least one polymer, so that the composite material has a ceramic content in the range of 64 to 90 vol% and a polymer content in the range from 10 to 36% by volume. A composite material according to claim 8, comprising a second material fraction (C) of ceramic particles, wherein a mean grain size of the ceramic particles of the second material fraction (C) is at least a factor of 10 smaller than an average grain size of the ceramic particles of the first material fraction (A). A compressed composite material produced in particular by a method according to one of the preceding claims 1 to 7, which comprises at least a first material fraction (A) of metal particles and at least one polymer (P), so that the composite material has a metal content in the range from 50 to 90% by volume. and a polymer content in the range of 10 to 50 vol%. A compressed composite material, in particular produced by a method according to one of the preceding claims 1 to 7, comprising at least a first material fraction (A) of ceramic particles, at least a second material fraction (C) of metal particles and at least one polymer (P), such that the Composite material has a ceramic content x in the range of 50 to 85 vol%, a metal content z in the range of 0-50 vol% and a polymer content y in the range of y = (100 - x - z) vol%. A compressed composite material, in particular produced by a method according to one of the preceding claims 1 to 7, comprising at least a first material fraction (A) of polymer particles and at least one further polymer portion, wherein preferably one material fraction of an epoxy resin and the other material fraction consists of a thermoplastic , Use of a compressed composite material according to one of claims 8 to 12 as a dental prosthesis, bone substitute, machine parts, preferably gears and seals, artificial stone, Kitchen worktop, tile, muffler, dishes, filters, electrical insulator, axle feedthroughs.

Images