HK1203886B - Mixer. method of mixing raw material for powder metallurgy binder for injection moulding composition - Google Patents

Description

Method and mixer for mixing in powder metallurgy and binder for injection moulding compositions

Technical Field

The invention relates to a mixer for producing ceramic pellets (pellet), known as feed, comprising: in one aspect, at least one inorganic powder comprising at least one component of the oxide or cermet (cermet) or metal or nitride type, or at least one compound comprising at least one of the above components; in another aspect, at least one organic binder; the mixer comprises at least one container in which at least one mixing device is movable, and a heat exchanging device.

The invention also relates to the use of a mixer of this type for producing pellets of the ceramic type, known as feed material, said pellets comprising: in one aspect, at least one inorganic powder comprising at least one oxide or cermet or metal or nitride type component, or at least one compound comprising at least one of the foregoing components; in another aspect, at least one organic binder.

The invention also relates to a binder composition for injection moulding and to an injection moulding composition (feed) for producing shaped metal or ceramic parts.

The invention also relates to a method for mixing raw materials for powder metallurgy, in particular for producing given ceramic-type feed pellets from a mixture comprising: at least one inorganic powder containing at least one component of oxide or cermet or metal or nitride type, or at least one compound comprising at least one of the above components; and at least one organic binder.

The present invention relates to the field of powder metallurgy for obtaining ceramics, in particular to a process for mixing raw material mixtures to form an intermediate mass as a feed material to be supplied to an injection molding press for forming the element to be produced.

Background

Powder metallurgy technology can be used in the production of hard materials for the jewelry-and watch-making industries, or technical applications such as the medical, electronics, telephone or tool industries, mechanical cutting inserts, consumer goods industries, in particular hard materials commonly known by the generic name inorganic "ceramics". The resulting inorganic composite material will be referred to herein as "ceramic" regardless of whether the material is sapphire, ruby, synthetic diamond, sapphire glass, ceramic, micro-magnets, metal, alloy, or otherwise in nature.

The base materials have different properties, some of which are kept secret in order to protect the product. Conventionally, the raw materials used at least include: on the one hand ceramic powders and on the other hand organic binders, such as resins, or plastic materials, or other similar materials, which allow injection moulding and allow the correct bonding of the mixture with all the raw materials to produce the element. Other additives may also be included in the mixture. It can be appreciated that the raw materials can be of different textures: solid, powder, liquid or slurry. The structure of the mixture may change during its formation, particularly (but not limited to) when the complementary components of the resin composition undergo polymerization.

The overall process for manufacturing an inorganic ceramic element comprises at least the following steps:

-preparing a starting material,

mixing the raw materials and/or, if desired, carrying out two or more pre-mixes,

-a homogeneous mixing of the components,

-granulation (pelletizing),

-moulding a quantity of powder or feed pellets obtained by mixing and granulation, in particular in a moulding cavity, to form a "green" element. Such moulding can be carried out by injection under pressure, in particular in a screw injector, which comprises means for heating the quantity of powder or feed pellets obtained by mixing and granulation;

-thermal debinding (thermal debinding) to burn off and/or dissolve some of the components of the mixture as binders, heat treating, or sintering, the "green" element;

-heat treating, or sintering, the "green" element after degumming, so that the finished element has final consistency. This heat treatment causes dimensional shrinkage, so that the element of final dimensions can be obtained;

-subjecting the element to a surface polishing treatment.

This simplified introduction to the process hides the complexity of the actual development process, which is unique for each raw mixture and each polished element, both in terms of its physical properties, in particular its abrasion resistance and appearance, and in terms of its mechanical and chemical properties.

Each step requires care to be taken and requires precise parameters to be followed, otherwise irreversible changes to the properties of the blend, injection molded "green" component, degummed "green" component, or sintered component can occur.

The homogeneous mixing step is particularly decisive for the subsequent steps of the process. This mixing step may sometimes be combined with a prior raw material mixing step, performed directly in a manufacturing plant, referred to herein as a "compounder".

In fact, during mixing, reactions occur between some of the starting materials that immediately change the physical state of the mixture being mixed. In particular, uncontrolled and uncompensated exothermic reactions can lead to complete transformation of the mixture, which can result in its failure to be used for the manufacture of the intended polishing element. The parameters of temperature, speed and torque must all be closely monitored. The physical properties finally obtained must be reproducible and therefore the mixing must be perfectly adjusted so that the reactions taking place are predictable and controllable.

In particular, when this type of mixture is mixed by means of rotating blades in a mixer, the temperature of the components in the mixture rises rapidly above the melting temperature of the components due to the effect of friction, so that they are mixed with one another in the form of a slurry. The problem is that there is a very high temperature gradient in the mixture when approaching the melting temperature, on the order of a few degrees celsius per second, even 10 ℃ per second. It is difficult to achieve effective cooling to prevent heat loss and deterioration of the mixture.

European patent application EP2338590a1 by NITTO DENKO CORP discloses a method and a plant for producing resins by means of a paddle mixer, according to a very specific arrangement, in relation to the output of the material at the lower end of the vessel, in the form of a curved section equipped with heat exchange means, the progressive solidification of the synthetic resin being controlled by cooling before crushing. The material is melted only by friction. This document relates in particular to polymeric resins, not intended for powder mixtures, and not suitable for the production of feedstock.

European patent application EP0956918a1 to LOEDIGE maschinkanba GmbH describes a method for producing an intermediate product for injection molding, which intermediate product is made of a metal or ceramic powder and an organic binder. The mixer produces an annular mixture of materials to obtain a powder that can be poured out and is mechanically treated to melt the organic binder without any heating other than the rise in temperature caused by friction between the materials.

ADVANCED MATERIALS TECH, EP1344593a2, relates to a method for producing an aluminium alloy part by injection moulding from a sintered material made from a mixture of at least 95% by weight of aluminium powder and an oxide or additive, and very specific parameters for this mixture are described. This document does not describe an apparatus for heating a material.

The process for manufacturing the cermet feed is described in U.S. patent application US2004/217,524A1 to MORIS ROBERT CRAIG, carried out according to specific parameters and in particular at a rather low temperature, without using a rotating system, but premixed in another vessel and then fed to a screw extruder.

It is another object of the present invention to provide an optimized binder for injection molding compositions that facilitates powder metallurgical mixing to obtain ceramics or metals to obtain products with highly reproducible quality and controllable coefficient of shrinkage.

From US5145900, for example, thermoplastic masses (feedstock) are known for the manufacture of shaped ceramic parts, which contain sinterable inorganic powder and a polymeric organic binder consisting essentially of polyoxymethylene and of a mixture of polyoxymethylene and polytetrahydrofurane (polyoxolane) copolymer.

However, these feeds have been found to suffer from a number of drawbacks and problems, such as lack of sufficient flowability for injection molding, cracking or delamination in the molded shape and retention in the final product. This is particularly true for complex shaped parts. They also present environmental problems due to the need to use corrosive products such as nitric acid, especially in the final organic phase removal step. Furthermore, the use of water in the removal of the organic binder carries a risk of oxidation of the feed material containing the metalliferous material.

Disclosure of Invention

The invention aims to improve the powder metallurgical mixing process for producing ceramics in order to obtain products of highly reproducible quality and with a controlled shrinkage factor, with a relative deviation of less than two thousandths, or even less than one thousandth.

The invention therefore relates to a mixer for producing pellets of the ceramic type known as feed, said pellets comprising: in one aspect, at least one inorganic powder comprising at least one oxide or cermet or metal or nitride type component, or at least one compound comprising at least one of the foregoing components; in another aspect, at least one organic binder; said mixer comprising at least one container in which at least one mixing device is movable, and a heat exchange device, characterized in that said heat exchange device comprises a heating device for heating said container and/or its contents to a temperature between a lower temperature (lower temperature) above which the mixture corresponding to a given type of ceramic becomes a slurry and an upper temperature (higher temperature) below which the mixture corresponding to said given type of ceramic must be kept, said lower temperature and said upper temperature being stored in a memory for the mixture corresponding to said given type of ceramic; further characterized in that in a first connection, the heating device exchanges energy with a first heat exchange and mixing temperature maintenance circuit external to the vessel, wherein the thermal inertia of the first circuit is higher than the thermal inertia of the mixture-laden vessel.

According to one characteristic of the invention, the heat exchange device also comprises a cooling device which, in the second connection, exchanges energy with a second circuit at ambient temperature external to the container, wherein the thermal inertia of the second circuit is much higher than the thermal inertia of the container filled with the mixture, by a second factor (factor).

The present invention also relates to a binder for shaped compositions which overcomes the above drawbacks and has as a further object to improve the homogeneity and flowability of the feed, to enable the manufacture of metal or ceramic parts of more complex shape, to reduce the production cycle time, to increase the mechanical resistance of the "green" and degummed bodies to the production stresses (handling and various cutting processes) and finally to avoid the use of environmentally harmful products of debindered organic binders, while using as an alternative a non-polluting solvent which can be eliminated by simple heat treatment.

Accordingly, the present invention relates to a binder for an injection molding composition, comprising:

-35-54 vol% of a polymer matrix,

-40-55 vol% of a mixture of waxes,

-and about 10 vol% of a surfactant,

wherein the polymer matrix comprises a copolymer of ethylene and methacrylic acid or acrylic acid, or a copolymer of ethylene and vinyl acetate, or a copolymer of ethylene comprising maleic anhydride, or a mixture of these copolymers, and polyethylene, polypropylene and acrylic resin.

The invention also relates to an injection moulding composition (feedstock) for the manufacture of shaped metal or ceramic parts, comprising 76 to 96 wt% of an inorganic powder and 4 to 24 wt% of a binder, said binder comprising:

-35-54 vol% of a polymer matrix,

-40-55 vol% of a mixture of waxes,

-and about 10 vol% of a surfactant,

wherein the polymer matrix comprises a copolymer of ethylene and methacrylic acid or acrylic acid, or a copolymer of ethylene and vinyl acetate, or a copolymer of ethylene comprising maleic anhydride, or a mixture of these copolymers, and polyethylene, polypropylene and acrylic resin.

The invention also relates to a method for mixing raw materials for powder metallurgy, in particular for producing feed pellets of a given type of ceramic from a mixture comprising: at least one inorganic powder containing at least one component of oxide or cermet or metal or nitride type, or at least one compound comprising at least one of the above components; and at least one organic binder, according to which:

-feeding the mixture into a blender container comprising at least one mixing device,

-stabilizing the temperature of the vessel and its contents and approaching a mixing temperature between a lower temperature limit above which the mixture becomes pasty and below which the mixture must be kept, by connecting a heat exchange device to a first heat exchange and mixing temperature maintenance circuit,

-setting the mixing device to move at a speed lower than or equal to 700 revolutions per minute,

-mixing the mixture until a compact homogeneous mass is obtained,

-stopping the high temperature stabilizing effect on said container and its contents, which have been allowed to cool, at a temperature higher than or equal to the characteristic temperature of the relevant mixture, and which is a compact homogeneous mass.

According to one feature of the invention, when the high temperature stabilizing action of the container and its contents is stopped at a temperature higher than or equal to the characteristic temperature of the mixture in question and of a compact homogeneous mass, the temperature of the container and its contents is lowered by natural means or by using the heat exchange device with a negative temperature gradient, or by connecting the heat exchange device to a second circuit at an ambient temperature close to 20 ℃.

According to another characteristic of the invention, during or after said temperature reduction, the compact lumps are crushed, either in the container at a temperature lower than 100 ℃ and at a speed higher than or equal to 700 revolutions per minute of the mixing device, or in a crushing device attached to a blender.

Drawings

Other features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

fig. 1 is a schematic view of a control system of a mixer according to the invention.

Fig. 2 is a partial schematic view (including a simple sketch connected to a control system) of a mixer according to a first variant of the invention, in section along an axis passing through the mixing shaft, wherein the mixing container comprises only one energy exchange circuit and one heating circuit.

Fig. 3 shows, in a similar way to fig. 2, a second variant of a mixing container, wherein the mixing container comprises two energy exchange circuits, one exchanging energy with the heating circuit of fig. 2 and the other exchanging energy with the cooling circuit.

Fig. 4 and 5 show schematic side views of two exemplary mixing shafts assembled according to different compositions.

Fig. 6 shows a partially schematic top view of a mixer according to the first variant of fig. 2 (the connection to the control system is omitted).

Fig. 7 shows a mixer according to a second variant of fig. 3 in a similar manner to fig. 6.

Fig. 8 shows a partially schematic top view of the mixer according to the invention (omitting the connection to the control system), in which the mixing shaft is removed and replaced by a set of movable blades and vanes, which combine with a worm screw housed in a recess in the bottom of the container, for breaking up and separating "cakes".

Fig. 9 is a flow chart of a mixing process according to the invention in a mixer according to the invention.

Detailed Description

More specifically, the powder known as ceramic used within the scope of the invention is an inorganic powder containing at least one component of the oxide or cermet or metal or nitride type, or at least one compound containing at least one of the above-mentioned components.

For example, the inorganic powder may include, in a non-limiting manner, zirconia or alumina, carbides or nitrides or similar substances.

These components or oxides are selected so as to ensure high hardness, high wear resistance, high mechanical stress resistance, and excellent properties for a long time without deterioration.

The organic binder, resin or plastic material or similar material used ensures that the inorganic powder can be subjected to a compression or injection moulding operation and has sufficient viscosity to enable injection into the mould, while also having sufficient resistance to deformation.

The mixer according to the invention for performing the mixing process disclosed below has versatility and these examples of powder metallurgy do not limit its possible uses. For example, "MIM" (metal injection molding) may also be implemented.

The purpose of mixing is to coat the powder particles with one or more binders to enable a homogeneous slurry to be obtained.

After mixing, the homogeneous slurry is cooled to form a compact mass. This compact mass is then broken up to obtain pellets called feed, which have a consistent composition and nominal size and are ready for injection into, for example, an injection molding press.

In one particular non-limiting version of the invention, the mixer 1 is used for manufacturing ceramic type feed pellets, said pellets comprising: in one aspect, at least one of the above inorganic powders; in another aspect, at least one organic binder; the mixer 1 comprises at least one container 2. At least one mixing device 3 is movable in the mixer 1, extending into the respective container 2 or from the bottom of the container 2, as shown.

The mixer 1 comprises a heat exchange device 4, which heat exchange device 4 may comprise at least one circuit in which a fluid circulates in the double wall of the vessel 2, or in coils housed in the vessel 2, or otherwise.

The mixer 1 advantageously comprises a control device 5 connected to a measuring device 6 and to a device 7 for storing in a memory temperature parameters according to the type of material to be formed.

The control device 5 is arranged to regulate the temperature of the container 2 and the heat exchange between the container 2 and at least one medium outside the container 2 by means of the heat exchange device 4.

In the simplest version, the control device 5 is controlled manually and comprises means for controlling the rotation speed of each mixing device 3 and the temperature and/or flow rate of each heat exchange circuit in dependence on information displayed by a measuring device 6, said measuring device 6 being for example a temperature probe in each heat exchange circuit located in the vessel 2 or a thermometer immersed in the slurry manually or automatically.

In a more automated production, the control device 5 comprises at least one programmable automatic control system capable of performing corresponding operations according to a stored production program for each type of inorganic material to be produced, called "ceramic".

These control devices 5 can control, in particular, the heat exchange device 4 according to the degree of automation of the installation and this control is linked to: a measure of the shaft speed and/or flow rate of the compact mass, a measure of the temperature of the compact mass and/or the vessel, and a threshold value, in particular a threshold value of the temperature, which is specified for the manufacture of a given product. All parameters for a given product are stored in the memory device 7, which advantageously enables control of the entire production cycle, including all desired timings.

According to the invention, the heat exchange means 4 comprise heating means 41 for heating the container 2 and/or its contents to a temperature comprised between a lower limit temperature TINF, above which the mixture corresponding to a given type of ceramic is slurried, and an upper limit temperature TSUP, below which the mixture corresponding to a given type of ceramic must be maintained to avoid degradation of the binder.

In the storage device 7, the lower temperature TINF and the upper temperature TSUP are stored in a memory for the mixture corresponding to a given type of ceramic. In the case of a manual control of the mixer, the memory device consists of a summary sheet (summary sheet) containing the recipes of the ingredients to be loaded into the mixer, including the corresponding tolerances, as well as the temperature limits for each phase and the time range for which each phase lasts.

Said heat exchange device 41 exchanges energy in a first connection with the first heat exchange and mixing temperature maintenance circuit 8 outside the container 2. And the thermal inertia of the first circuit 8 is higher than that of the container 2 filled with mixture. Preferably, the former is higher than the latter by a factor K1 greater than 2.

This thermal inertia characteristic of the heating circuit is an essential feature of the invention, since it makes it possible to obtain very short cycle times.

Heating the container 2 and its contents is contrary to the prior art concept. Heating enables less variation from the average temperature and full control of the temperature gradient. Thus, it is no longer necessary to rotate the mixing shaft at high speed to allow the components to reach the melting temperature by friction therebetween. The product output obtained is more uniform, which is very important in powder metallurgy, since it means perfect control of the shrinkage factor during sintering, which depends on the mixing quality. For example, for powders based on raw materials such as zirconia, ZrO₂The prior art for producing ceramics, which can be realized by producing 5 batches of 20kg each per day, achieves a coefficient of shrinkage of between 1.2850 and 1.2920, which coefficient, however, is in all cases unchanged, and can be returned to 1 with the mixer according to the invention and the corresponding mixing process.In the range of 2875 to 1.2895, or 1.2880 to 1.2890, the relative deviation is 1.6 thousandths, or 0.8 thousandths, which is a significant improvement over the prior art of 5.4 thousandths, i.e., a factor of about 3.5 or 7. The production is thus reproducible.

In one particular embodiment of the invention, as shown in figures 3 and 8, the heat exchange device 4 comprises a cooling device 42 for cooling the vessel 2 and/or its contents. These cooling devices 42 are distinguished from the heating device 41, as shown in fig. 3 and 8. In this variant, the cooling device 42 exchanges energy in the second connection with the second circuit 9 at ambient temperature outside the container 2, and the thermal inertia of this second circuit 9 is much higher than that of the container 2 filled with the mixture, preferably the former by a second factor K2 greater than 2. Like the heating circuit, this thermal inertia characteristic of the cooling circuit is an important feature of the invention, since it enables very short cycle times to be obtained.

The unique application of the heating circuit and the cooling circuit, each of which has a thermal inertia much higher than that of the container and its contents, allows on the one hand to control the cycle time, which can be significantly shortened with respect to the prior art, and on the other hand to control the thermal gradient: the temperature stability ensured by the heat exchange with the external circuit avoids the uncontrollable gradients in the melting of the binder by friction of the prior art, which are generally more than 10 ℃ per second or higher.

The invention enables product control at high temperatures.

The invention also enables control of shrinkage to be ensured, since any degradation of the ingredients is avoided. The problem of degradation is complicated by the fact that typical binders have melting temperatures ranging from 50 ℃ for wax to 165-180 ℃ for paraffin wax or the like. It can be appreciated that the temperature point of degradation and loss of properties of many ingredients is very close to the melting point. Thus, a paraffin wax having a melting temperature of about 180 ℃ is completely degraded at about 200 ℃ and is only 20 ℃ higher than its melting point, which is clearly difficult to control for a gradient of about 10 ℃ per second. The same phenomenon also occurs with acrylic compounds. At high temperatures (i.e. between 150 ℃ and 200 ℃ for the ceramic feedstock for which the invention is particularly useful), this control is therefore very important for obtaining high-quality products in a reproducible manner.

In a particular embodiment of the invention, the control device 5 controls the heat exchange device 4 so as to initiate heat exchange with the container 2 at a given time, using only the cooling device 42 or only the heating device 41.

The desired temperature profile may be obtained by alternating the heat exchange of a single heat exchange circuit in the vessel with either a heat source or a cooling source. The second embodiment uses two distinct circuits, one of which can be directly connected to the vessel, allowing the vessel 2 to be in instantaneous contact with a circuit with a much higher thermal inertia, enabling the vessel 2 to overcome the effects of the thermal inertia and thus rapidly stabilize the vessel within a temperature range that is conducive to a smooth implementation of the process, thus significantly reducing the overall cycle time.

The mixing device 3 preferably, but in a non-limiting manner, comprises a rotating shaft 30 carrying blades 33 and/or blades inside the container 2. Each hybrid shaft 30 is preferably driven by a motor 31 via a belt or the like, which motor 31 is equipped with a continuously variable transmission connected to a control device 5, which control device 5 controls the variable transmission. The shaft 30 is preferably equipped with a tachometric motor (tachometric motor) 63, which transmits the actual rotational speed of the shaft 30 to the control device 5. Fig. 2 shows the mixing shaft 30 in a cantilevered arrangement and driven under the container 2, the shaft 30 traversing this container 2, said shaft 30 being equipped with a pulley 310 of a diameter greater than that of a pulley motor 311, both connected by a belt 312 or the like, in order to obtain a greater torque, given that it is less necessary to obtain a high rotation speed with respect to the prior art.

Fig. 1 to 3 show the role of the control device 5 to control the rotation speed of the motor 31 driving the mixing shaft 30 directly or indirectly, and in particular the heat exchange speed by means of the first pump 81 in the first circuit 8 of the heating device 41, on the basis of at least one piece of information about the speed of the mixing device 3 or the quantity of product undergoing the transition in the mixer 1, and at least one piece of information about the temperature of the container 2 or the quantity of product measured by the sensor in the measuring device 6.

In a particular manner in the second embodiment, the control device 5 also acts on the second pump 91 in the second circuit 9 of the cooling device 42 when the cooling device 42 exchanges energy with the second circuit 9 in the second connection.

The control device 5 comprises a clock 51 so as to be able to follow the process parameters entered in the memory device 7.

The measuring device 6 may particularly (but not exclusively) comprise all or part of the following sensors:

a temperature sensor 61, which is located in the first circuit 8 of the heating device 41, preferably in the container 2 or as close to the container as possible. In the case of the first variant, which comprises only the heating device 41, one sensor is preferably placed at the outlet of the heating system; another sensor is placed at the inlet of the same circuit.

In the case of the second variant, the temperature sensor 62 in the second circuit 9 of the cooling device 42 is preferably in the container 2 or as close to the container as possible,

a tachometer motor 63 for measuring the rotational speed of the mixing shaft 30,

a motion sensor 64 for characterizing the motion of the slurry in the vessel, in particular a rotational speed sensor, for a worm or gear freely mounted on a wheel axle at the bottom of the vessel or similar,

a temperature sensor 65, located inside the mixture or slurry, in particular connected to the above-mentioned motion sensor 64,

at least one (preferably two) temperature probe 66, located on one inner surface of the vessel 2, preferably just flush with the inner surface of the vessel 2, and preferably close to the bottom of the vessel,

a temperature sensor 67 of the mixing shaft 30, preferably towards the end of the mixing shaft close to the bottom of the container 2,

a temperature sensor 68, which is located in one of the large containers of the first exchange circuit 8,

a temperature sensor 69, which is located in one of the large containers of the second exchange circuit 9.

The control device 5 may also act on a first regulator 82, the first regulator 82 being intended to increase (or remove) the heat of the first circuit 8, and/or on a second regulator 92, the second regulator 92 being intended to remove (or increase) the heat of the second circuit 9, the first and second regulators 82, 92 possibly comprising heating elements and/or cooling units. Preferably, the first circuit 8 delivers oil, while the second circuit 9 delivers a mixture of water and antifreeze or the like.

In one embodiment, the mixer 1 comprises several containers 2 equipped in this way, which are connected to one another starting from an upstream container, into which the raw materials are fed by a feeder 21, such as a hopper or the like, and ending in a downstream container, which is used in particular for the final breaking up of the intimately mixed agglomerates. The downstream vessel also provides the dual function of a mixing vessel and a crushing vessel: the raw materials to be mixed are loaded into the mixing vessel from an upstream vessel, at least one mixing shaft stirs the pulp in the mixing vessel with suitably shaped paddles and/or blades, and cuts and separates it, as the case may be, a final crushing step can be performed by this type of mixing shaft 30, or by at least one crushing shaft equipped with blades 22, which blades 22 are more suitable for separating the compact solidified mass. If necessary, another disruptor may be used downstream to achieve the desired particle size.

A non-limiting example of a single container 2 is shown in the attached drawings, in which single container 2 a mixing process is performed, from the introduction of raw material to the breaking up of cooled mixed lumps called "cakes" to obtain feed pellets or fines.

More particularly, as shown in fig. 2, the shaft 30 is vertical and comprises in particular blades 33, which blades 33 are preferably distributed in several parallel planes.

The arrangement of the blades and/or paddles is preferably adjustable so as to be effective for both small and large loads: the whole mixing shaft 30 can be modified at the coupling 32, or the mixing shaft 30 can comprise a series of spigot-carrying paddles or blades which bear against each other and are separated, if necessary, by spacers 35 to obtain a particular configuration, as shown in figures 3 and 4, in which the shaft 30 is thus equipped with three sets of low paddles 33A, 33B and 33C, topped by high paddles 34. Although the arrangement of blades or vanes in a substantially planar level is most common, blades or vanes 34 having a substantially conical envelope (envelope) with respect to the axis of the mixing shaft may equally well be used, in particular for the top level, which is suitable for high loads. The term "paddles" essentially means radial blades, which have a shape that allows a specific movement, initially for mixing the raw materials and then for mixing the slurry. The term "blades" means similarly shaped blades having a slimmer cross-section, sharp leading edges, particularly for cutting and moving the mass of pulp, however, the sharp edges have proven to be counterproductive in that they are more prone to wear than the drive paddles for the pulp, which wear results in contamination, spoiling the accuracy of the feed composition and, as a result, any sharp edge requires increased monitoring of production. Advantageously, the "low" paddle or blade closest to the bottom of the vessel has a shape similar to the vessel, or inscribes a conical, toroidal or spherical surface, and serves to perform the function of scraping the slurry at the bottom of the vessel.

Each set of paddles and blades is preferably offset from an adjacent set by an angle; different sets may include a different number of blades or blades and have varying angular positions, in particular to avoid any resonance and noise problems.

In the case of a single blade having two arms, the two adjacent bushings are offset by approximately 90 °.

In a known manner, the blades and/or vanes 33 preferably have a slight angle of incidence with respect to a plane perpendicular to the axis of the shaft 30. The angle of incidence can be adjusted as follows: this is done very simply by exchanging a blade set mounted on the socket as shown above, or in larger installations by using a return mechanism (return mechanism), which, however, is more prone to wear due to the movement of the pulp. Depending on the case, the angle of incidence can be adjusted depending on the direction of rotation of the shaft, either pushing the compact mass towards the bottom of the container, or conversely lifting the mass: an embodiment of mixing will of course consume more energy, however, a higher set of blades tending to lift the slurry from the bottom of the vessel will facilitate mixing, while a lower set of blades tending to push the slurry towards the bottom of the vessel will be beneficial, particularly in the final step of the process, which is used to subdivide the cake obtained after cooling the slurry-like compact mass into several portions (fragmenting).

After the mixing shaft 30 has been removed vertically, the cake can also be broken up by the combined action of a worm 37 embedded in a groove 39 in the bottom of the container 2 and a blade 36 hinged about a vertical axis, the broken up feed pellets then being removed by reversing the direction of the worm and transferred to a supply station 38.

In another variant, the crushing is continued until a powder is obtained. The powder is converted in an additional downstream granulation device, in which it is first pressed to form an extrudate and then cut into pellets during the course of travel.

Each container 2 is preferably equipped with a closing device comprising at least one valve or one overpressure discharge orifice.

The heat exchange in the container in which the mixing is performed makes it possible to:

-softening of a portion of the adhesive occurs below a maximum softening temperature threshold by increasing the temperature,

very good homogeneity of the slurry, with a temperature deviation in the slurry of about +/-2 to 3c,

by keeping the first heat exchange and mixing temperature maintenance circuit 8 at a constant temperature (the thermal inertia of this circuit 8 is much higher than that of a fully loaded container), controlling the thermal gradient of the compact mass in the container to be less than 3 ℃ per second or 3 ℃ per minute with friction of the mixture components, such low thermal gradient obtained by the embodiment of the invention allows lower mixing speeds with respect to the gradient of about 10 ℃ per second obtained with a mixer of the prior art equipped only with cooling devices,

by lowering the temperature, the slurry temperature is kept below a maximum threshold value specific to the mixture, defined to avoid any deterioration of its performance, in particular when an exothermic reaction occurs between certain binder ingredients, and/or when the mixing speed is too high, and/or when the friction in the mixture is too high, either with the blades/blades or with the container.

The previously mixed compact mass cools and solidifies by rapidly lowering the temperature after the heat exchange and mixing temperature maintenance circuit is disengaged. A rapid temperature reduction can be achieved by connecting the heat exchange device 4 to a second ambient temperature circuit 9, the thermal inertia of this circuit 9 being much higher than that of a fully loaded container.

Controlling the rotational speed of at least one mixing shaft makes it possible to:

-reducing the friction mentioned above by reducing the speed,

gradually solidifying the compact mass by reducing the speed of the final stage until it solidifies to form a "cake" form,

improving the cohesion of the binder component around the inorganic powder by increasing the speed, the inorganic powder containing at least one component of oxide or cermet or metal or nitride type, or at least one compound containing at least one of the above components,

-splitting the compact mass previously solidified into cake form by increasing the speed to produce feed pellets.

Thus, in addition to the parameters specific to the intermediate product (in particular its viscosity), the behavior of the heat exchange device over time and the mixing speed determine the quality of the final product. The correct management of these actions naturally determines the cycle time of the compounder and therefore the production costs and depreciation of the equipment.

In general, efforts have been made to maintain both temperature and mixing speed at the limit thresholds specific to each mixture.

The mixer 1 can also be equipped with a device for measuring the speed of movement of the compact mass inside the vessel, for example placed on a moving part 60, for example a worm or idler gear immersed in the mass inside the vessel, the speed of rotation of which is measured by a slurry movement sensor 64, advantageously the temperature inside the compact slurry mass is measured by a slurry temperature sensor 65.

The means for measuring the temperature of the compact mass may be placed on said moving part 60 and/or be formed by temperature sensors 66 on the inner surface of the container 2 at the bottom of the container 2 and/or by temperature sensors 67 at the periphery of the mixing shaft 30, preferably at the lower part of the mixing shaft, near the bottom of the container 2.

The invention also relates to a specific binder for injection molding compositions comprising:

-35-54 vol% of a polymer matrix,

-40-55 vol% of a mixture of waxes,

-about 10 vol% of a surfactant,

wherein the polymer matrix comprises a copolymer of ethylene and methacrylic acid or acrylic acid, or a copolymer of ethylene and vinyl acetate, or a copolymer of ethylene comprising maleic anhydride, or a mixture of these copolymers, and polyethylene, polypropylene and acrylic resin.

Preferably, the binder of the present invention comprises 2 to 7 vol% of one of said copolymers or mixtures thereof, about 25 vol% of polyethylene, 2 to 15 vol% of polypropylene and 6 to 15 vol% of acrylic resin.

According to a preferred method, the copolymer of ethylene and methacrylic acid comprises from 3 to 10% by weight of methacrylic acid or acrylic acid comonomer, the copolymer of ethylene and vinyl acetate comprises from 7 to 18% by weight of vinyl acetate comonomer, the copolymer of ethylene and anhydride is a random copolymer of ethylene and maleic anhydride with a melting point of 100-110 ℃ or the copolymer of high density polyethylene and modified anhydride with a melting point of 130-134 ℃.

Preferably, the acrylic resin has a molecular weight of 50000-220000 and a viscosity of 0.21-0.83, and is selected from the group consisting of: polymers of isobutyl methacrylate, methyl methacrylate, ethyl methacrylate and N-butyl methacrylate (N-butyl methacrylate), and copolymers of isobutyl methacrylate and N-butyl methacrylate and methyl methacrylate, or mixtures of these polymers and/or copolymers.

Advantageously, the wax is Carnauba (Carnauba) wax or paraffin, or palm oil, or a mixture of these ingredients.

According to another preferred feature, the surfactant is N, N' ethylene distearamide or a mixture of stearic acid and palmitic acid (stearic acid), or a mixture of these ingredients.

The invention also relates to an injection moulding composition (feedstock) for the manufacture of metal or ceramic shaped parts, comprising 76 to 96 wt% of an inorganic powder and 4 to 24 wt% of a binder, said binder comprising:

-35-54 vol% of a polymer matrix,

-40-55 vol% of a mixture of waxes,

-about 10 vol% of a surfactant,

wherein the polymer matrix comprises a copolymer of ethylene and methacrylic acid or acrylic acid, or a copolymer of ethylene and vinyl acetate, or a copolymer of ethylene comprising maleic anhydride, or a mixture of these copolymers, and polyethylene, polypropylene and acrylic resin.

According to a particular feature, the inorganic powder of the injection moulding composition may be selected from the group comprising oxide, nitride, carbide or metal powders or mixtures of said powders, preferably said inorganic powder is selected from the group comprising: alumina powder, zirconia powder, chromium carbide powder, titanium carbide powder or tungsten carbide powder, metal tungsten or silicon nitride powder, stainless steel powder, metal titanium powder or a mixture of the powders.

According to a preferred embodiment of the injection molding composition, the composition comprises (in weight percent):

76 to 88% of alumina and 12 to 24% of the above-mentioned binder according to the invention, or

76-88% of aluminum oxide and 0.1-0.6% of magnesium oxide and 12-24% of the binder according to the invention, or

58-86.5% zirconium oxide, and 3.9-4.6% yttrium oxide, and 0.18-18.5% aluminum oxide, and 9-22% of the binder of the invention, or

61.5-84% zirconium oxide, and 3.9-4.6% yttrium oxide, and 0.2-9% aluminum oxide, and 2-5.5% of an inorganic pigment selected from the list comprising iron oxide, cobalt oxide, chromium oxide, titanium dioxide, manganese oxide, zinc oxide or mixtures of said oxides, and 9-22% of a binder according to the invention, or

88 to 91% of chromium carbide or titanium carbide and 9 to 12% of a binder according to the invention, or

93-96% of tungsten carbide or metallic tungsten, and 4-7% of a binder according to the invention, or

78-85% of silicon nitride, and 15-22% of the binder according to the invention.

The invention will be described in more detail below by way of non-limiting examples.

Example 1：

The polymer portion of the binder is mixed with Black zirconia powder (e.g., st. gobain zer Black) at a temperature of about 150 ℃ to make a premix. The wax and surfactant are added to the premix and the temperature is further raised to about 180 ℃ to form a homogeneous slurry which is then cooled and granulated/granulated until solidification and then held to form a charge which can be used to manufacture shaped parts by injection according to known techniques.

In this example 1, more specifically, 17.2kg of zirconium powder (86 wt%) and 2.8kg of binder (about 14 wt%) were used in the following volume composition:

-24% of high density polyethylene

10% of polypropylene

4% of a copolymer of ethylene and of methacrylic acid (containing 6.5% by weight of methacrylic acid, for example of the type "Nucrel (TM)" from DuPont)

10% of an isobutyl methacrylate copolymer resin having a molecular weight of 195,000 (for example of the type "Elvacite (TM) 2045" from Lucite International)

1% of an isobutyl methacrylate and N-butyl copolymer resin having a molecular weight of 165,000 (for example of the type "Elvacite (TM) 2046" from Lucite International)

11% of carnauba wax

31% Paraffin (e.g. "Carisma 54T (TM)" type from Alpha Wax BV)

6% of N, N' -ethylene distearamide

3% of a mixture of stearic acid and palmitic acid (for example of St é arine Dubois type).

Example 2：

The same type of raw material as in example 1 was prepared, but with white zirconia instead of black zirconia, using a binder with slightly different amounts of different components, more specifically:

26% of high-density polyethylene

10% of polypropylene

4% of a copolymer of ethylene and of methacrylic acid

11% of "Elvacite 2045" resin

1% of "Elvacite 2046" resin

11% of carnauba wax

-29% paraffin wax

-8% of N, N' -ethylene distearamide

Example 3：

Again using the same organic binder formulation ingredients, with slight variations in volume ratio, other raw materials can be prepared from various ceramic or metal powders, more specifically from alumina (with a shrinkage index of 1.19 or 1.30 (translucent)), or chromium carbide, or titanium carbide, tungsten carbide (of different quality) and metallic tungsten, and according to the following table:

the execution of the method of mixing raw materials for powder metallurgy according to the invention, in particular the production of feed pellets of a given type of ceramic from a mixture comprising at least the following steps: in one aspect, at least one inorganic powder comprising at least one oxide or cermet or metal or nitride type component, or at least one compound comprising at least one of the foregoing components; and, in another aspect, at least one organic binder:

adding the mixture to a vessel 2 of a mixer 1, which vessel 2 comprises at least one mixing device 3,

stabilizing the temperature of the vessel 2 and its contents at a temperature close to the mixing temperature, between a lower temperature TINF specific to the mixture concerned and an upper temperature TSUP specific to the mixture concerned, above which the mixture becomes pasty and below which the mixture must be kept to prevent binder degradation, by connecting the heat exchange device 4 to the first heat exchange and mixing temperature maintenance circuit 8,

-setting the mixing device 3 in motion at a speed lower than or equal to 700 revolutions per minute,

-mixing said mixture until a compact, homogeneous mass is obtained,

-stopping the high temperature stabilizing effect on the container 2 and its contents, which container 2 and its contents have been allowed to cool, at a temperature T5, wherein this temperature T5 is higher than or equal to the temperature which is characteristic of the mixture concerned and which is characteristic of a compact homogeneous mass.

In a variant, as shown in fig. 2 and 6, the heat exchange device 4 comprises a single heating circuit comprising a heating device 41 and connected to the first heat exchange and mixing temperature maintenance circuit 8. The heating device 41 comprises, for example, at least one thermostat, for example of the "HB Therm" type or similar, using oil, temperature-controlled at a pressure of up to 5 bar, so that a positive temperature gradient, or a negative temperature gradient, can be obtained. The temperature regulator may be used to control the temperature drop of the vessel 2.

According to a particular embodiment of the invention, when the high temperature stabilizing effect of the container 2 and its contents is higher than or equal to the specific temperature of the relative mixture and the temperature characteristic of a compact homogeneous mass ceases, the temperature of the container 2 and its contents is lowered by natural means or by a second ambient temperature circuit connecting the heat exchange device to about 20 ℃.

In particular, when the mixer 1 is equipped with a second cooling circuit 9, the heat exchange device 4 may be connected to the second circuit 9 to reduce the temperature, wherein the second circuit 9 is at an ambient temperature of about 20 ℃.

The container 2 is preferably equipped with a sealing cap 39 to prevent any contamination of the mixture and to ensure that the proportions of the different ingredients in the mixture remain stable.

According to another particular embodiment of the invention, the compact agglomerates are crushed during or after the temperature reduction, said crushing being carried out in the container 2 at a temperature lower than 100 ℃ and at a speed of the mixing device 3 higher than or equal to 700 revolutions per minute, or in a crushing device attached to the mixer 1.

In order to implement the latter embodiment involving a higher rotational speed, the interior of the container 2 is advantageously coated with a wear-resistant coating, such as diamond or glass or the like.

The specific sequence of using the mixer 1 is given below, taking as an example the mass production of zirconia-based ceramics of a mass of about 5kg (i.e. of a volume of about 10 litres), with the following steps, and in particular specifying the meaning of low speed, high speed and high temperature:

-a step 100: directly in the container 2 or in the feeder 21, a first portion of powder and constituent (structures) charges, comprising in particular powder and polymer plastic, is filled, the temperature regulator of the container being activated at a maximum temperature T0, T0, between 125 ℃ and 180 ℃, preferably close to 125 ℃, by activating the heating means 41 and deactivating the cooling means 42, the mixing shaft 30 being set in rotation at a speed V0 of 150-.

-a step 110: after reaching a temperature T1-150 ℃ and a speed V1-300 rpm, a second portion is filled, which includes the remaining binder matrix, in particular a wax-based component.

In one variant, step 110 is performed at a speed V1 of 300-700 rpm. In another variation, the rotational speed is restarted at about 700rpm after the second portion of filler is loaded in step 115.

-a step 120: after reaching a temperature T2 ═ 160 ℃, the rotation of the shaft 30 is stopped, the container 2 is opened for inspection, the walls of the container and the paddles/blades are wiped if necessary (this inspection phase can be assisted by a camera, however contamination protection is very difficult, the best inspection method for breakages in the container 2 and the paddles 33 and 34 can be by measuring the torque or energy absorbed by the motor 31, with reference to the setpoint values for the reference production stored in the storage device 7).

-a step 130: the rotation is restarted, after the temperature T3-168 deg.c and the speed V3-700 rpm, the shaft 30 stops rotating, the vessel is opened, a check step 135 is performed, and the vessel wall and the blades/blades are wiped according to step 136 as required.

-a step 140: the rotation is restarted and mixing continues for a predetermined duration D4 after the temperature reaches TINF 4-170 deg.c and the speed V4-700 rpm.

-a step 150: the temperature of the compact mass is measured, which must be between T5 and TSUP-T6-190 ℃ (test step 155), T5 being between 178-185 ℃, in particular close to 180 ℃, mixing being continued until the above temperature range is reached.

-a step 160: the shaft 30 stops rotating and cooling is achieved by deactivating the heating device 41 and activating the cooling device 42.

-step 170: after reaching a temperature between T7 ═ 150 ℃ and T8 ═ 180 ℃ (test step 175), preferably a temperature lower than or equal to 160 ℃, the compact mass is set in rotation to clear the blades/blades of the obstacle and/or to improve the shearing effect, requiring a check for thermal inertia, since this would cause a significant difference between the temperature indicated by the sensors on the vessel and the temperature of the mixed mass, up to 20 ℃, where the temperature of the mixed mass is higher. The time interval between phases 160 and 170 is relatively long with respect to the overall cycle time, in particular about 10 minutes.

-step 180: temporarily rotated at a speed V9 of between 300 and 700rpm to form a "cake", the speed V9 preferably being close to 700rpm and cooled to a temperature between T9 and 95 ℃ and T10 and 110 ℃. In a first variant, this cooling can be performed by switching the temperature regulation system to a cooling mode, in which the negative gradient is about-2 ℃ per minute, or in a second variant, the cooling is performed by deactivating the heating device 41 and activating the cooling device 42.

-step 190: checking ensures that there is no contamination, stopping rotation altogether if contamination is found, and then proceeding to step 195: the cutting of the 'cake' is manually completed.

In one variant, a batch production of zirconia-based ceramic of mass about 10kg (i.e. of volume about 20 litres) is carried out, the parameters being varied to obtain an optimum yield:

-a step 100: the temperature T0 is preferably close to 180 ℃ and the speed V0 is approximately 150 and 189 rpm.

Steps 110 and 115: wherein the rotational speed V1 is less than 350rpm, preferably less than 300 rpm.

-a step 130: the speed V3 is approximately 300 rpm.

-a step 140: the speed V4 is approximately 300 and 350 rpm.

-step 180: the speed V9 is approximately 300 rpm.

The following steps depend on the equipment of the mixer 1, i.e. the equipment for cutting the "cake", the equipment for crushing, and the equipment for protecting the container 2 from wear.

If no special equipment is provided, the pieces cut from the cake are removed by hand and the crushing is performed in another equipment.

In case the container 2 is equipped with an inner coating to protect it from abrasion, the following steps can be carried out directly in the mixing container.

-a step 200: the disruption is carried out at a V11 of more than 700rpm, in particular more than 1000 rpm. This speed is only limited by the equipment and can in particular reach 10000 rpm.

-a step 210: the rotation of the shaft 30 is stopped.

-step 220: discharging is carried out below V12-2000 rpm and below T12-85 ℃, speeds above 100rpm generally resulting in the product being ground into a powder, such product facilitating reprocessing, in particular by screw extrusion or discharging, in order to make pellets or the like, in particular by cutting a billet formed by screw extrusion of said powder.

Advantageously, at the outlet of the extruder or pellet cutter, pellets of different sizes are made, further downstream, when they are used to feed the injection press, the different volumes are advantageous because they are more easily stacked tile-like in the injection press. This saves a lot of time, for example 18 seconds instead of 25 seconds for a ceramic mixture for the middle part of a watch.

In this example of 5kg packing, the total motor cycle time is 20-30 minutes, the total cooling time is 15-30 minutes, and the total drain time is 5-15 minutes.

In a particular way, this process is carried out on an injection-moulding composition (feedstock) containing 76 to 96% by weight of an inorganic powder and 4 to 24% by weight of a binder containing:

-35-54 vol% of a polymer matrix,

-40-55 vol% of a mixture of waxes,

-about 10 vol% of a surfactant,

wherein the polymer matrix comprises a copolymer of ethylene and methacrylic acid or acrylic acid, or a copolymer of ethylene and vinyl acetate, or a copolymer of ethylene comprising maleic anhydride, or a mixture of these copolymers, and polyethylene, polypropylene and acrylic resin.

This sequence is particularly applicable to a raw mixture comprising 14% (mass percent) binder, wherein the binder comprises 50 vol% of the material forming the structural matrix, 42% of the material forming the fluidizing matrix, and 8% of the material forming the surfactant matrix.

In a particular way, the method is carried out using an adhesive of one of the above-mentioned types according to the invention, which comprises in particular:

-35-54 vol% of a polymer matrix,

-40-55 vol% of a mixture of waxes,

-about 10 vol% of a surfactant,

wherein the polymer matrix comprises a copolymer of ethylene and methacrylic acid or acrylic acid, or a copolymer of ethylene and vinyl acetate, or a copolymer of ethylene comprising maleic anhydride, or a mixture of these copolymers, and polyethylene, polypropylene and acrylic resin.

This working range for use with the mixer 1 as defined above makes it possible to avoid many of the problems encountered in the prior art:

all temperature gradients are controllable, precise.

The temperature increase of the mixture and of the compact mass is strictly limited to a predetermined maximum threshold, here equal to TSUP T6-190 ℃.

The cooling time is reduced because the heat exchange device cools the compact mass.

When the rotation of the shaft stops, the temperature of the compact mass can be maintained at a given value, since the heat exchange device can heat or cool the compact mass via the container.

The temperature of the container is suitably close to that of the compact mass, but the temperature of the compact mass is preferably determined by means of immersed sensors, either manually or by means of sensors operated by a robot arm.

The powder in the mixture no longer sticks to the walls of the vessel during heating, because of the low speed control of the blade rotation speed during cold premixing of the ingredients.

The execution of the adjustments makes it possible to limit the wear of the walls of the container and of the blades/vanes, the contamination being therefore greatly reduced and the speed of wear of the equipment being greatly reduced.

The process can be carried out with the vessel closed, and in particular the optical monitoring performed by the camera can determine whether wiping of the vessel wall is required, theoretically less prone to clogging than the prior art, due to the gradual increase in temperature and the control of the rotation speed of the slurry.

The compact agglomerates obtain a satisfactory homogeneous mixing, and subsequently the fed pellets exhibit the same reproducible behaviour during injection moulding.

Reduction of energy consumed for driving, heating and cooling.

Claims (24)

1. A mixer (1) for manufacturing ceramic type pellets, called feed, from a mixture comprising: in one aspect, at least one inorganic powder comprising at least one oxide or cermet or metal or nitride type component, or at least one compound comprising at least one of the foregoing components; in another aspect, at least one organic binder; -said mixer (1) comprises at least one container (2) in which at least one mixing device (3) is movable, and-said mixer (1) further comprises a heat exchange device (4), characterized in that said heat exchange device (4) comprises a heating device (41) for heating said container (2) and/or the contents thereof; in a first connection, the heating device (41) exchanges energy with a first heat exchange and mixing temperature maintenance circuit (8) located outside the container (2), wherein the thermal inertia of the first heat exchange and mixing temperature maintenance circuit (8) is higher than the thermal inertia of the container (2) filled with the mixture.

2. A mixer (1) according to claim 1, wherein the thermal inertia of the first heat exchange and mixing temperature maintenance circuit (8) is higher than the thermal inertia of the container (2) filled with the mixture by a first factor K1 greater than 2.

3. A mixer (1) according to claim 1, characterised in that the heat exchange device (4) comprises a cooling device (42), in a second connection the cooling device (42) exchanging energy with a second circuit (9) at ambient temperature outside the container (2), the second circuit (9) being distinct from the first heat exchange and mixing temperature maintenance circuit (8), and the thermal inertia of the second circuit (9) being much higher than the thermal inertia of the container (2) filled with the mixture by a second factor K2 greater than 2.

4. A mixer (1) according to claim 1, characterized in that the mixer (1) comprises a control device (5), the control device (5) being connected to a measuring device (6) and a storage device (7), the storage device (7) being adapted to store temperature parameters depending on the type of material to be manufactured; the control device (5) controls the heat exchange device (4); -said heating device (41) is intended to heat said container (2) and/or its contents to a temperature comprised between a lower temperature TINF, above which the mixture for a given type of ceramic becomes pasty, and an upper temperature TSUP, below which the mixture for said given type of ceramic must be kept, said lower temperature TINF and said upper temperature TSUP being stored in a storage for the mixture for the given type of ceramic, said lower temperature TINF and said upper temperature TSUP being stored in said storage device (7) for the mixture for the given type of ceramic; the control device (5) controls the heat exchange device (4) so as to initiate, at a given time, a heat exchange with the container (2) using only the cooling device (42) or only the heating device (41).

5. A blender (1) as claimed in claim 4, characterized in that, on the basis of at least one piece of information about the speed of the mixing device (3) or the speed of the product mass undergoing the transition caused by the blender (1), and at least one piece of information about the temperature of the container (2) or the product mass measured by a sensor in the measuring device (6), on the one hand, the control device (5) controls the rotational speed of a motor (31), which motor (31) directly or indirectly drives a mixing shaft (30) comprised in the mixing device (3), and on the other hand, the control device (5) controls the rate of heat exchange by means of a first pump (81) in the first heat exchange and mixing temperature maintenance circuit (8) of the heating device (41).

6. Mixer (1) according to claim 4, characterized in that the heat exchange device (4) comprises a cooling device (42), which cooling device (42) in a second connection exchanges energy with a second circuit (9) at ambient temperature outside the container (2), which second circuit (9) is distinct from the first heat exchange and mixing temperature maintenance circuit (8), the thermal inertia of the second circuit (9) being much higher than the thermal inertia of the container (2) filled with the mixture by a second factor K2 which is greater than 2; in the second connection, the control device (5) controls the rate of heat exchange by means of a second pump (91) in the second circuit (9) of the cooling device (42) when the cooling device (42) exchanges energy with the second circuit (9).

7. Mixer (1) according to claim 4, characterized in that the heat exchange device (4) comprises a cooling device (42), which cooling device (42) in a second connection exchanges energy with a second circuit (9) at ambient temperature outside the container (2), which second circuit (9) is distinct from the first heat exchange and mixing temperature maintenance circuit (8), the thermal inertia of the second circuit (9) being much higher than the thermal inertia of the container (2) filled with the mixture by a second factor K2 which is greater than 2; the control device (5) is arranged to control a first regulator (82) or/and a second regulator (92), the first regulator (82) being arranged to add or remove heat to the first heat exchange and mixing temperature maintenance circuit (8), the second regulator (92) being arranged to remove or add heat to the second circuit (9).

8. A mixer (1) according to claim 4, wherein the measuring device (6) comprises a motion sensor (64) characterizing the movement of the slurry in the vessel (2), the motion sensor (64) being in the form of a rotational speed sensor for a moving part (60) freely mounted at the bottom of the vessel, the measuring device (6) further comprising a temperature sensor (65) inside the mixture or slurry coupled to the motion sensor (64).

9. A mixer (1) according to claim 4, wherein the measuring device (6) comprises a temperature sensor (67) on a mixing shaft (30) included in the mixing device (3), and the temperature sensor (67) is close to the bottom of the container (2).

10. Use of the mixer (1) according to claim 1 for manufacturing ceramic type feed pellets, the feed pellets comprising: in one aspect, at least one inorganic powder comprising at least one oxide or cermet or metal or nitride type component, or at least one compound comprising at least one of the foregoing components; -at least one organic binder, on the other hand, characterized in that the heating device (41) is arranged to heat the container (2) or/and the content thereof to a temperature between a lower temperature TINF, above which the mixture for a given type of ceramic becomes pasty, and an upper temperature TSUP, below which the mixture for a given type of ceramic must be kept, the lower temperature TINF and the upper temperature TSUP being stored in a reservoir for the mixture for a given type of ceramic.

11. Use of a mixer (1) according to claim 1 for manufacturing ceramic type feed pellets from a raw material mixture comprising 14% by mass of a binder, which in turn comprises 50% by mass of a material forming a structural matrix, 42% by mass of a material forming a fluidizing matrix, and 8% by mass of a material forming a surfactant matrix.

12. A method for mixing raw materials for powder metallurgy, i.e. a method for manufacturing ceramic feed pellets of a given type from a specific mixture comprising: in one aspect, at least one inorganic powder comprising at least one oxide or cermet or metal or nitride type component, or at least one compound comprising at least one of the foregoing components; and, in another aspect, at least one binder, according to which:

-adding the mixture to a vessel (2) of a mixer (1) comprising at least one mixing device (3),

-keeping the temperature of the vessel (2) and its contents stable and close to the mixing temperature, which is comprised between a lower limit temperature TINF and an upper limit temperature TSUP above which the specific mixture becomes pasty, by connecting the heat exchange device (4) to a first heat exchange and mixing temperature maintenance circuit (8), the lower limit temperature TINF and the upper limit temperature TSUP storing energy for the specific mixture of a given type of ceramic, the heat exchange device (4) comprising a heating device (41) for heating the vessel (2) or/and its contents being controlled to exchange energy with the first heat exchange and mixing temperature maintenance circuit (8) outside the vessel (2) in a first connection depending on the temperature comprised between the lower limit temperature TINF and the upper limit temperature TSUP -in storage, and wherein the thermal inertia of said first heat exchange and mixing temperature maintenance circuit (8) is higher than the thermal inertia of said container (2) loaded with said specific mixture;

-setting the mixing device (3) to move at a speed lower than or equal to 700 revolutions per minute,

-mixing said mixture until a compact homogeneous mass is obtained;

-stopping the high temperature stabilizing effect on said container (2) and its contents, which has been allowed to cool, at a temperature equal to or higher than the temperature T5, which temperature T5 is the temperature characteristic of the relevant mixture and of the compact homogeneous mass.

13. Method of mixing raw materials for powder metallurgy according to claim 12, characterized in that the thermal inertia of the first heat exchange and mixing temperature maintenance circuit (8) is higher than the thermal inertia of the container (2) filled with the mixture by a first factor K1 greater than 2.

14. Method for mixing raw materials for powder metallurgy according to claim 12, characterized in that, in order to limit or reduce the temperature of the specific mixture, or/and when the high temperature stabilizing effect on the container and its contents is stopped at a temperature higher than or equal to the temperature specific to the relevant mixture and characteristic of a compact homogeneous mass, the temperature of the container and its contents is reduced, and a negative temperature gradient controls the heat exchange device (4), which heat exchange device (4) comprises a cooling device (42), which cooling device (42) exchanges energy in a second connection with a second circuit (9) external to the container (2) at an ambient temperature close to 20 ℃, which second circuit (9) is separated from the first heat exchange and mixing temperature maintenance circuit (8), wherein the thermal inertia of the second circuit (9) is much higher than the full load of the mixture by a second factor K2 greater than 2 The thermal inertia of the container (2).

15. Method of mixing raw materials for powder metallurgy according to claim 12, characterized in that the compact homogeneous mass is crushed in the container at a temperature lower than 100 ℃ and at a speed of the mixing device higher than or equal to 700 revolutions per minute during or after the temperature reduction.

16. Method of mixing raw materials for powder metallurgy according to claim 12, characterized in that it is applied to the production of specific mixtures of zirconia-based ceramics with volumes of several litres and with the following steps:

-100: -charging a first portion of a charge of powder and structure directly into said container (2) or into a feeder (21) upstream of said container (2), wherein said first portion comprises powder and polymer plastic, -activating a temperature regulator of the container by activating said heating means (41) at a maximum temperature T0-180 ℃, activating a mixing shaft (30) of said container (2) to rotate at a speed V0-300 rpm;

-110: once the temperature T1 ═ 145 ℃ and the speed of rotation V1 of the mixing shaft (30) of 300rpm are reached, a second portion forming the remaining binder charge is added;

-120: -upon reaching a temperature T2 ═ 160 ℃, the mixing shaft (30) stops rotating;

-checking the content of the container (2) and the mixing shaft (30), if necessary wiping paddles or/and blades comprised in the mixing shaft (30);

-130: -resetting the mixing shaft (30) into motion;

-the mixing shaft (30) stops rotating once the temperature T3 ═ 168 ℃ and the speed V3 ═ 700rpm have been reached;

-135: -checking the contents of the container (2) and the mixing shaft (30);

-136: if necessary, wiping a paddle or/and a blade included in the mixing shaft (30);

-140: -rotating again said mixing shaft (30) and mixing the mixture for a predetermined duration D4 specific to the specific mixture once the temperature TINF 170 ℃ and the rotation V4 700rpm have been reached;

-150: measuring the temperature of the resulting compact mass, which must be between T5-180 ℃ and TSUP-T6-190 ℃, and mixing is continued until this temperature range is reached;

-160: stopping rotation of the mixing shaft (30), cooling the compact agglomerates by deactivating the heating device (41);

-170: once a temperature between T7-150 ℃ and T8-180 ℃ is reached, the compact mass is set into rotation to clear the blades/blades of the mixing shaft (30) of obstructions and/or increase shear;

-180: controlling the temporary rotation of the mixing shaft (30) at V9-300 rpm to form a "cake" which is cooled to a temperature between T9-95 ℃ and T10-110 ℃, by switching the temperature regulation system to a cooling mode with a negative gradient of about-2 ℃ per minute, or by deactivating the heating device (41).

17. Method of mixing raw materials for powder metallurgy according to claim 16, characterized in that the specific cooling is performed in the following steps:

-100: -opening the thermostat of the container at a maximum temperature T0 ═ 180 ℃, by activating the heating device (41) and deactivating the cooling device (42);

-160: cooling the compact agglomerates by deactivating the heating device (41) and activating the cooling device (42);

-180: cooling the "cake" to a temperature between T9-95 ℃ and T10-110 ℃, by switching the thermoregulation system to a cooling mode with a negative gradient of about-2 ℃ per minute, or by deactivating the heating device (41) and activating the cooling device (42).

18. The method for mixing raw materials for powder metallurgy according to claim 16, characterized in that, for the blender (1) used, the inside of the container (2) is equipped with crushing equipment and the container (2) is equipped with an internal wear-resistant coating; after cooling the "cake", directly in the container (2) the following steps are performed:

-200: crushing at 700rpm V11;

-210: stopping rotation of the mixing shaft (30);

-220: the product obtained was discharged at a temperature below T12-85 ℃ at a speed less than V12-2000 rpm.

19. Method of mixing raw materials for powder metallurgy according to claim 18, characterized in that the crushing is performed at a speed higher than 100rpm in order to obtain fine powder from the product in powder form, to achieve discharge by screw extrusion by screws and to form pellets.

20. The method of mixing raw materials for powder metallurgy according to claim 12, wherein the method uses a binder comprising:

-35-54 vol% of a polymer matrix,

-40-55 vol% of a mixture of waxes,

-about 10 vol% of a surfactant,

wherein the polymer matrix comprises a copolymer of ethylene and methacrylic acid or acrylic acid, or a copolymer of ethylene and vinyl acetate, or a copolymer of ethylene comprising maleic anhydride, or a mixture of these copolymers, and polyethylene, polypropylene and acrylic resin.

21. The method of mixing raw materials for powder metallurgy according to claim 20, characterized in that the method uses an injection molding composition, i.e. a feedstock, for manufacturing shaped metal or ceramic parts, the injection molding composition comprising 76 to 96 wt% of an inorganic powder and 4 to 24 wt% of the binder, wherein the inorganic powder of the injection molding composition is selected from: oxide, nitride, carbide or metal powders or mixtures of these powders.

22. The method for mixing raw materials for powder metallurgy according to claim 21, wherein the inorganic powder is selected from the group consisting of: alumina powder, zirconia powder, chromium carbide powder, titanium carbide powder or tungsten carbide powder, metal tungsten powder or silicon nitride powder, stainless steel powder, metal titanium powder or a mixture of these powders.

23. The method for mixing raw materials for powder metallurgy according to claim 21, wherein the injection molding composition is selected to include the following components in weight percent:

76-88% of alumina and 12-24% of said binder, or

76-88% of alumina and 0.1-0.6% of magnesium oxide and 12-24% of said binder, or

58-86.5% zirconium oxide, and 3.9-4.6% yttrium oxide, and 0.18-18.5% aluminum oxide, and 9-22% of said binder, or

61.5-84% zirconia, and 3.9-4.6% yttria, and 0.2-9% alumina, and 2-5.5% inorganic pigments, and 9-22% of said binder, wherein the inorganic pigments are selected from the following list: iron oxide, cobalt oxide, chromium oxide, titanium dioxide, manganese oxide, zinc oxide or mixtures of these oxides, or

88-91% of chromium carbide or titanium carbide, and 9-12% of said binder, or

93-96% of tungsten carbide or metallic tungsten, and 4-7% of said binder, or

78-85% silicon nitride, and 15-22% of the binder.

24. Method of mixing raw materials for powder metallurgy according to claim 12, characterized in that it is applied to a raw material mixture comprising 14% by mass of a binder, in turn comprising 50% by mass of a material forming a structural matrix, 42% by mass of a material forming a fluidization matrix, 8% by mass of a material forming a surfactant matrix.