Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
  • B01J13/02—Making microcapsules or microballoons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
  • B01J13/02—Making microcapsules or microballoons
  • B01J13/06—Making microcapsules or microballoons by phase separation
  • B01J13/14—Polymerisation; cross-linking
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
  • B01J13/02—Making microcapsules or microballoons
  • B01J13/20—After-treatment of capsule walls, e.g. hardening
  • B01J13/22—Coating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/26—Nozzle-type reactors, i.e. the distribution of the initial reactants within the reactor is effected by their introduction or injection through nozzles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
  • B01J3/008—Processes carried out under supercritical conditions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00002—Chemical plants
  • B01J2219/00004—Scale aspects
  • B01J2219/00006—Large-scale industrial plants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00002—Chemical plants
  • B01J2219/00027—Process aspects
  • B01J2219/0004—Processes in series
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00761—Details of the reactor
  • B01J2219/00763—Baffles
  • B01J2219/00765—Baffles attached to the reactor wall
  • B01J2219/00768—Baffles attached to the reactor wall vertical

Definitions

• the present invention relates to a method for the synthesis "in-situ" in pressurized CO 2 medium, for example supercritical, organic particles or inorganic coated.
• the particles to be coated are synthesized and then coated using a single method, in a single device, hence the expression "in situ".
• the synthesis and the coating of particles can be carried out in a single operation.
• the process of the present invention allows the manufacture of the coated particles continuously, semi-continuously or discontinuously.
• the particles to be coated are generally in the form of a powder.
• the present invention finds many industrial applications, for example in the manufacture of ion conductors, catalysts, ceramics, coatings, cosmetics, pharmaceuticals, etc. These applications will be described in more detail below.
• the process of the present invention allows the synthesis of nanophase oxides and their coating by different coating agents.
• the references between square brackets ([•]) refer to the list of references after the examples.
• sol-gel process In the case of ceramic particles, one of the main ceramic oxide synthesis processes currently used is the sol-gel process.
• Subramanian et al. in 2001 [1] describes the yttrium oxide synthesis by sol-gel route.
• Znaidi et al. [2] describes a semi-continuous process for the synthesis of sol-gel magnesium oxide powders.
• Adshiri et al. [3] have described a hydrothermal crystallization process for the rapid and continuous synthesis of metal oxide particles in supercritical water. This is a continuous synthesis process using a hydrothermal process.
• a homogeneous oxidizing or reducing atmosphere can be created by introducing gases or additives
• hydrothermal synthesis such as the continuous reaction in supercritical water for the synthesis of La 2 CuO 4 described in 2000 [5] or the synthesis of nanocrystalline zirconia and titanium oxide particles described in 2002 by Kolen'ko et al. [6].
• Viswanathan et al. have described the continuous formation, in a tubular reactor, of zinc oxide nanoparticles by oxidation of zinc acetate in supercritical water medium [7].
• An aqueous solution of preheated hydrogen peroxide is used as oxidizing agent.
• the supercritical solvents in particular the alcohols and the CO 2 , were used for the sol-gel process, initially, at the time of the gel drying step, for the removal of the residual solvent after the reaction.
• a semi-continuous process has been developed for the synthesis of nanoscale metal oxide powders (chromium oxide, magnesium oxide, barium titanate).
• the synthesis of titanium dioxide nanopowders by such a process has been described in 2001 by Znaidi et al. [12].
• Reverchon et al. [17] have proposed a system for the continuous synthesis of titanium hydroxide particles by a hydrolysis reaction of titanium tetraisopropoxide in supercritical CO 2 medium.
• Examples of chemical methods include interfacial polycondensation processes, emulsion polymerization and dispersed polymerization which are part of the chemical processes commonly used for polymer coating.
• SDS sodium dodecyl sulphate
• MMA methyl methacrylate
• SDS sodium dodecyl sulphate
• a synthesis of zinc oxide and PMMA composite microspheres by suspension polymerization has been described by Shim et al. [19] in 2002.
• supercritical CO 2 coating processes include the methods described by J. Richard et al. [20] and by Jung et al. [21].
• supercritical atomization processes (RESS for Rapid Expansion of Supercritical Solutions) as described by J-H. Kim et al. [22] or derivative methods such as those described by Y. Wang et al.
• the RESS coating is based on the atomization of supercritical solutions containing the coating agent and the particles to be coated. This method has been used in particular by Kim et al. [22] for the microencapsulation of Naproxen. Another method uses the RESS process to spray the coating agent (dissolved in CO2) on the particles. This method has been used for example by Chernyak et al. [32] for the formation of a perfluoroether coating for porous materials (applications in civilian infrastructure and monuments) and by Wang et al. [23] for coating glass beads with polyvinyl chloride-co-vinyl acetate (PVCVA) and hydroxypropyl cellulose (HPC).
• PVCVA polyvinyl chloride-co-vinyl acetate
• HPC hydroxypropyl cellulose
• the RESS process with a non-solvent is a modified RESS process: it allows the encapsulation of poorly soluble particles in supercritical CO2, with a coating agent insoluble in supercritical CO2.
• the coating agent is solubilized in a CC 2 / organic solvent mixture, the particles to be coated are dispersed in this medium. The depressurization of this dispersion causes the precipitation of the coating agent on the particles.
• This method has been used for the formation of drug microcapsules [24], the microencapsulation of protein particles [25] and the coating of oxide particles (TiO 2 and SiO 2 ) with polymers [33, 34].
• the particles to be coated are fluidized by a supercritical gas or fluid, the supercritical CO 2 solubilized coating agent is precipitated on the surface of the fluidized particles [26]. , 27, 35].
• the particles and the coating agent are dissolved or suspended in an organic solvent and then sprayed, together or separately, in the anti-solvent consisting of by the supercritical CO 2 .
• Multi-pass nozzles are used to allow spraying of different components especially for the ASES process and the SEDS process.
• Juppo et al. [36] described the incorporation of active substances (particles to be coated) into a matrix (coating agent) using supercritical antisolvent processes.
• the semi-continuous SAS process was used by Elvassore et al. [28] for the production of protein filled polymer microcapsules.
• the ASES process used for the preparation of microparticles containing active ingredients has been described by Bleich et al. [29].
• microspheres by the PGSS method by saturating, with supercritical CO 2 , a solution of the particles in the coating agent before atomizing it.
• the advantage of this process is that it is not necessary for the particles and the coating agent to be soluble in supercritical CO 2 [21].
• Shine and GeIb have described a liquefaction of a polymer using supercritical solvation for the formation of microcapsules [37].
• phase separation coating technique is well suited for discontinuous equipment [30]. This method has been described for the polymer coating of proteins by Ribeiros Dos Santos et al. [30] in 2002. A slightly different method was used by Glebov et al. [38] in 2001 for the coating of metal particles. Two units are used: the first containing the embedding agent (it allows its solubilization in supercritical CO 2 ) and the second the metal particles. The two units are interconnected by a valve to allow the transfer of the solubilized coating agent.
• the process by polymerization in a dispersed medium consists in carrying out the polymerization in supercritical CO2 medium, on the surface of the particles to be coated.
• the principle is the same as for the conventional polymerization coating.
• the use of a surfactant adapted to supercritical CO2 is essential, in order to allow the dispersion of the particles to be coated and the adhesion of the polymer to the surface of the particles. Enclosure descriptions by this method are beginning to appear in the literature. Yue et al. [31] thus achieved the coating of micrometric organic particles with PMMA and PVP.
• the present invention provides a method for synthesizing "in situ" coated oxide particles.
• the present invention allows the synthesis and coating of particles according to a standardized production, which facilitates its industrialization.
• the present invention also allows a real improvement from the point of view of the manipulation of nanometric powders, their stabilization for storage and possible shaping, for example by dispersion, pressing and sintering, compared to the processes of the prior art.
• the present invention may also make it possible to obtain functionalized powders, thanks to the nature of their coating, which may have particular properties different from those of the powders.
• the process for manufacturing coated particles with a coating material of the present invention comprises the following steps: (a) synthesis of particles in a pressurized CO2 medium,
• step (d) recovering the coated particles, the steps (a) and (b) being coupled in such a way that the particles synthesized in step (a) remain dispersed in pressurized CO 2 medium at least until step (c) ).
• the difference between the methods of the prior art and that of the present invention is in particular this coupling.
• This coupling was not easy to implement given the specificity of each of the processes used, the desired quality of the coated particles, and the pressurized medium.
• the inventors of the present invention are the first to have achieved such a coupling which both functions and gives very good quantitative and qualitative results for the manufacture of coated particles.
• the method of the present invention further has the advantage that it allows discontinuous, semi-continuous or continuous production of coated particles as illustrated by the examples below.
• coated particle is meant, in the present invention, any chemical particle coated on its surface with a layer of a material different from that constituting the particle.
• coated particles may constitute a powder, optionally in suspension or forming a deposit (for example in the form of a thin film or an impregnation). They can be used in different applications. They are found, for example, in ionic conductors; catalysts; ceramics; surface coatings, eg corrosion protection, wear protection coatings, coatings, coatings that support friction; cosmetic products; pharmaceutical products; etc.
• Pressurized CO2 medium means a gaseous CO2 medium placed at a pressure greater than atmospheric pressure, for example at a pressure ranging from 2 to 74 bar, the CO 2 being in the form of a gas.
• This pressurized CO 2 medium can advantageously be a supercritical CO2 medium, when the pressure is greater than 74 bar and the temperature is higher than 31 ° C.
• the particles which can be coated according to the invention can be chosen from metal particles; particles of metal oxide (s); ceramic particles; particles of a catalyst or a mixture of catalysts; of the particles of a cosmetic product or a mixture of cosmetic products; particles of a pharmaceutical product or a mixture of pharmaceuticals.
• the particles may be chosen from particles of titanium dioxide, silica, doped or non-doped zirconia, doped or non-doped ceria, alumina, doped or non-doped lanthanum oxides, magnesium oxide.
• the particles to be coated may be of any size. It may be a mixture of particles of the same or different size and / or identical or different chemical nature.
• the size of the particles depends essentially on their manufacturing process.
• the particles may have a diameter ranging from 30 nm to 3 ⁇ m. These particles can be agglomerated and form clusters of several microns.
• the step (b) of bringing the synthesized particles into contact with the coating material or its precursors is carried out on the synthesized particles which are dispersed in a pressurized CO 2 medium.
• the step (a) of synthesis of the particles and the step (b) of bringing said particles into contact with the coating material or its precursors are carried out in the same reactor, hereinafter referred to as "synthesis and contact reactor".
• This embodiment is suitable for semi-continuous or discontinuous manufacture.
• the step (a) of synthesis of the particles being carried out in a first reactor the synthesized particles are transferred, in a pressurized CO2 medium, into a second reactor, the step ( b) contacting said synthesized particles and the coating material or its precursors being made in said second reactor.
• This transfer can be carried out for example continuously or semi-continuously.
• the step (a) of synthesis of the particles may be followed by a step of scanning the particles synthesized with pressurized CO 2 before implementing the step (b) of contacting said particles with the coating material or its precursors.
• This sweeping step makes it possible to remove particles from the possible excesses and derivatives of the chemicals which participated in the manufacture of said particles.
• This scanning makes it possible to further improve the quality of the coated particles obtained according to the process of the present invention.
• this step of scanning the synthesized particles can be carried out in the reactor in which they have been synthesized. In the second embodiment, it can also be carried out during the transfer of the synthesized particles from the first to the second reactor or into the second reactor.
• the step (b) of bringing said synthesized particles into contact with the coating material or its precursors is carried out in said second reactor, this second reactor being a tubular reactor comprising a first end provided with an inlet and a second end provided with an outlet; in which the particles synthesized in the first reactor are injected into said second reactor, via the inlet, on the one hand, in a pressurized CO 2 medium, and on the other hand, at the same time as said particles, the material of coating or its precursors, so that the contacting of the synthesized particles and the coating material or its precursors is carried out in said second reactor; and wherein said coated particles or a mixture of particles and encapsulating material or precursors thereof are recovered via said outlet.
• the above-mentioned tubular reactor is a removable reactor, in order to be able to change the coils and thus benefit from a reactor of variable diameter and length and thus be able to vary the residence time of the reactants in this reactor .
• the second embodiment of the present invention corresponds to an advantageous method for a continuous or semi-continuous production. It uses two coupled systems: the first system is dedicated to the synthesis of particles, the second system to the coating of synthesized particles.
• the coating material may be any of the coating materials known to those skilled in the art. It may be for example a material chosen from a sintering agent, a friction agent, a wear-resistant agent, a plasticizer, a dispersing agent, a crosslinking agent, a metallizing agent, a metal binder, a corrosion resistance agent, an abrasion resistance agent, a coating of a pharmaceutical product, a cosmetic product coating.
• the coating material may be chosen from an organic polymer, a sugar, a polysaccharide, a metal, a metal alloy or a metal oxide.
• the coating material may be a polymer chosen from polymethyl methacrylate and polyethylene glycol; a metal selected from copper, palladium, platinum; or a metal oxide selected from magnesium oxide, alumina, doped zirconia or not, ceria doped or not.
• the "precursors of the coating material” generally consist of chemicals for obtaining the coating material.
• the coating material when the coating material is a polymer, its precursors may be a monomer, a prepolymer of said polymer or a monomer / prepolymer mixture.
• the precursors may also be a monomer, a prepolymer, an acetate, an alkoxide, and in addition to these products, additives, such as surfactants, polymerization initiators, reaction catalysts, acids.
• Documents [22] to [39] describe precursor materials of the coating material useful in the present invention.
• the method of the invention may further comprise a step (x) for preparing the coating material or its precursors before the step (b) of contacting.
• step (x) can be chosen for example from a sol-gel process, a polymerization process, a prepolymerization process, a thermal decomposition process, an organic synthesis process or inorganic.
• step (x) may consist in solubilizing the coating material in a solvent, which may be organic or inorganic (for example when an anti-solvent process is used (SAS )), or in a pressurized CO2 medium, such as a supercritical CO2 medium (for example when implementing a RESS process).
• a solvent which may be organic or inorganic (for example when an anti-solvent process is used (SAS )
• SAS anti-solvent process
• step (x) may consist in solubilizing the coating material in a solvent, which may be organic or inorganic (for example when an anti-solvent process is used (SAS )), or in a pressurized CO2 medium, such as a supercritical CO2 medium (for example when implementing a RESS process).
• SAS anti-solv
• the process may be chosen from a polymerization, the precursors of the coating material being monomers and / or a prepolymer of the coating material in the presence of additives (such as surfactant and polymerization initiators); a sol-gel synthesis; a thermal decomposition process, and an inorganic synthesis process.
• additives such as surfactant and polymerization initiators
• sol-gel synthesis a thermal decomposition process
• inorganic synthesis process an inorganic synthesis process.
• the chemical transformation can be triggered by contacting the precursor of the coating material with the particles as indicated above.
• the coating step (c) can be carried out in the second reactor, following the contacting of the particles in pressurized CO2 medium and the coating material or its precursors.
• the step (c) of coating the particles can also be carried out at the outlet of said second reactor.
• This is the case for example for a coating produced by precipitation using a RESS process, in particular when the second reactor is a nozzle.
• the depressurization is at the outlet of the nozzle and causes the precipitation of the coating material on the particles.
• the coated particles remain in pressurized CO2 medium until all the layers of coating material are deposited.
• a sweeping of the coated particles can be carried out before each new step (b) and (c), for example by means of pressurized CO 2 , in order to clean the coated particles.
• the method of the present invention thus advantageously makes it possible to be adapted to all possible configurations of the desired coated particles.
• the coating of the particles may have all the thicknesses necessary for obtaining the desired coated particles.
• the thickness of the coating material can be up to a micrometer, but generally ranges from 0.1 to 5 nm.
• this recovery step may comprise a sweep of the particles coated with pressurized CO 2 . Indeed, such a sweep can remove coated particles obtained, the products and solvent in excess or unreacted. This "cleans" the coated particles obtained. This Scavenging the coated particles can be done by simply injecting pure pressurized CO2 into the reactor where they are recovered.
• the step (d) of recovery of the coated particles may comprise an expansion of the pressurized CO2. This is the case for example when the coating has been carried out in a pressurized CO2 medium. This relaxation can in certain cases cause the coating of the particles as indicated above.
• the particles coated in a solvent or in a surfactant solution can be recovered. This is the case, for example, when it is not desired for the coated particles to agglomerate with each other for use in a subsequent process, for example sintering or coating a surface.
• the solvent or surfactant solution used depends on the chemical nature of the coated particles, as well as the use of these particles.
• the solvent can be organic or inorganic.
• the surfactant solution may be a solution of a surfactant chosen, for example, from dextran or Triton X. These particles, thus suspended, may subsequently be sprayed onto a support, for example a metal, glass or ceramic carrier, in order to to form a coating.
• first device comprising: a reactor for synthesizing particles and for contacting the particles, in a pressurized CO2 medium, with the coating material or its precursors, a means for supplying said precursor reactor with particles, means for injecting the coating material or its precursors into said reactor, and means for supplying said reactor with pressurized CO 2 medium, valves arranged between the reactor and the reactor means, supply, injection and supply, wherein the means for injecting the coating material or its precursors is coupled to the reactor so that the injection of the coating material or its precursors into said The reactor does not suppress the pressurized CO 2 medium present in the reactor after synthesis of the particles.
• the synthesis reactor may be any of the reactors known to those skilled in the art for performing syntheses in a pressurized medium. It can be provided with a stirring mobile, and possibly baffles. These baffles break the vortex created by the mechanical stirrer and improve the homogenization of the reaction medium for the synthesis of particles and / or the coating of the particles.
• the means for injecting the coating material thus makes it possible to avoid any contact of the synthesized particles with the air, in particular during the introduction of the coating material or its precursors into the reactor.
• the injection means is preferably temperature controlled (thermoregulated), preferably also in pressure, this in particular in order to have all the parameters for controlling and maintaining a pressurized CO2 medium in the reactor during injection. Possible temperature and pressure ranges may be 100 to 700 ° C. and 10 to 500 bars, respectively.
• the means for injecting the coating material may be connected to a means for supplying a pressurized CO 2 medium.
• a means for supplying a pressurized CO 2 medium may be connected to a means for supplying a pressurized CO 2 medium.
• pressurized CO 2 it is possible, by means of pressurized CO 2 , to maintain the pressurized medium in the injection means, and possibly clean or purge the injection means.
• This means of supply makes it possible, for example, to implement the RESS methods in the device of the invention.
• the means for injecting the coating material or its precursors may comprise a reactor for preparing the coating material or its precursors, said preparation reactor being connected to said injection means.
• a tube can sealingly connect the preparation reactor for the coating material and the reactor for synthesizing and bringing the particles into contact.
• a pump can allow injection.
• two injection tubes can be used, one permitting injecting into the reactor the synthesis products of the particles (for example water, pressurized CO2 and precursors of the particles to be synthesized), the other the coating material or its precursor.
• FIG. 2 illustrates a device with two injection tubes discussed in the "Examples" section below.
• a second device comprising: a first reactor for the synthesis of particles in a pressurized CO2 medium, a second reactor for contacting the particles synthesized with the coating material or its precursors, means for transferring the synthesized particles from the first reactor to the second reactor, means for injecting the coating material or precursors thereof in said second reactor, means for supplying the device, in particular the first and second reactors, in a pressurized CO2 medium, valves disposed between said reactors and said means, wherein the means for transferring the synthesized particles makes it possible to maintain the synthesized particles dispersed in a pressurized CO2 medium during their transfer from the first to the second reactor, and wherein the means for injecting the material coating is coupled to said second reactor so that injection of the coating material or its precursors into said second reactor does not suppress the pressurized CO 2 dispersion of the particles in said second reactor.
• the inventors advantageously couple a synthesis reactor in a pressurized CO 2 medium to a coating reactor in a pressurized CO 2 medium that allows the coating material to be injected, thus avoiding any contact of the synthesized particles with the moisture. air and therefore the agglomeration of particles. Indeed, this agglomeration makes it difficult or impossible to coat the individualized particles, even if the powder is resuspended in CO 2 .
• the reactors of this second device may be chosen independently from any one of the reactors known to those skilled in the art for carrying out syntheses in a supercritical medium.
• Each reactor may be provided with a stirring device, and possibly with baffles.
• the role of mobile and baffles is explained above.
• at least one of the first and second reactors is thermoregulated, generally, the two reactors.
• the thermoregulation means may be those known to those skilled in the art, especially those commonly used in synthesis devices in a pressurized medium.
• This second device is generally provided with means for supplying said first reactor with pressurized CO2, water or organic solvent, and pure precursor products or in solution of said particles so as to allow the synthesis of the particles in said first reactor.
• These means may comprise the same characteristics as those of the first device described above.
• At least one of the first and second reactors of this second device may be a tubular reactor comprising at one of its ends an inlet and at the other end an outlet.
• the particles can be synthesized continuously by injecting via the first end the precursors of said particles and the pressurized CO2 and continuously extracting, in pressurized CO2 medium, via the second end, the synthesized particles.
• the first and second reactors are tubular.
• the first and second reactors are tubular and mounted in series, so that the output of the first reactor is connected to the inlet of the second reactor via the particle transfer means from the first reactor to the second reactor.
• the tubular reactor (s) are preferably removable (s). This advantageously makes it possible to replace the reactors, for example to choose their diameter, their shape or their length in order to vary the residence time of the reagents in the reactor, and thus to play on the rate of progress of the reaction and or the size of the synthesized and / or coated particles.
• the tubular reactor is of cylindrical shape, although any elongate shape and promoting contact between the particles and the coating material or its precursor is suitable.
• the tubular reactor may for example be rectilinear or serpentine. The length will be chosen according to the desired residence time.
• the second reactor may also be in the form of a nozzle, preferably a coaxial nozzle, allowing the particles to come into contact with the coating material or its precursors, said nozzle comprising first and second injection inlets, as well as an outlet, said first injection inlet being connected to the particle transfer means so as to be able to inject, into said nozzle, in a pressurized CO2 medium, the transferred particles, and said second injection inlet being connected to the injection means; coating material or its precursors, so as to inject into said nozzle, the coating material or its precursors.
• the nozzle usable in this second device can be defined as a venturi system, in which the particles and the coating material or its precursors are mixed, and possibly in which the particles are coated. The examples given below illustrate this second variant.
• a nozzle diameter is preferably chosen such that it is prevented from being clogged by the particles and the coating material during the implementation of the invention. process.
• This diameter is chosen according to the amount of material that passes through the nozzle, and depending on the size of the particles.
• a nozzle having an internal diameter ranging from several hundred microns to a few nanometers will be chosen.
• a nozzle having a length of a few centimeters to a few tens of centimeters is sufficient to implement the method of the invention.
• the nozzle may be of any form, provided that it fulfills its function of contacting the particles and the coating material or its precursors, and, where appropriate, the particle coating reactor.
• it may have a cylindrical, cylindroconic, frustoconical shape.
• the first pass may allow the introduction of pressurized CO2 and particles to be coated, the second pass being used to inject the coating material, alone, in solution or with pressurized CO2.
• the second reactor may be a reactor for contacting, coating and recovery of the coated particles.
• the device of the invention comprises one or more reactor (s) for recovering the coated particles.
• the second device may further comprise at least one recovery reactor connected to said second reactor so as to recover the coated particles.
• the recovery reactor may be connected to the outlet of the second reactor, whether it be tubular, in the form of a nozzle or in any other form, so as to be able to recover either the coated particles or the mixture of particles and particles. coating material or precursors thereof.
• said recovery reactor is connected to the outlet of said nozzle.
• the second device of the present invention may comprise at least two recovery reactors connected to said second reactor (for example, a nozzle) so as to be able to recover alternatively or successively in each of the recovery reactors the coated particles, or the mixture of particles and coating material or its precursors.
• the recovery reactors for example by means of valves, is switched into the second recovery reactor.
• This tilting can be controlled automatically by means of a level detector (optical or mechanical) placed in the recovery reactor and connected to a control of valves placed between the second reactor and the recovery reactors.
• a device comprising several recovery reactors also makes it possible to purge the device in a recovery reactor, for example at the beginning and at the end of the process, and to recover the particles coated in one or more other recovery reactors than the one used for the purge.
• the use of several recovery reactors is particularly suitable for the implementation of a continuous process for manufacturing coated particles.
• the second device may further comprise a third reactor which is a reactor for preparing the coating material or its precursors connected to the injection means via a material transfer means. coating or precursors thereof of said third reactor to said second reactor.
• This means may comprise a tube and a pump as indicated above.
• This third reactor makes it possible to implement the above-mentioned step (x) of the process of the invention. It may be for example a solubilization reactor of the coating material in a solvent or synthesis of the coating material.
• This third reactor may comprise for example means for its supply of solvent, and means for its supply of coating material or its precursors. These means may be simple openings, for example to introduce into the reactor a solvent, or injection devices, for example media pressurized.
• This third reactor may be, for example, a conventional solubilization reactor for the coating material or its precursors in a solvent, for example pressurized CO2, the means allowing its supply of solvent then being a means of supplying pressurized CO2.
• the means for transferring the coating material or its precursors from said third reactor to the second reactor preferably makes it possible to maintain the coating material solubilized in the pressurized CO 2 during its transfer and injection into said second reactor.
• This third reactor may also be a conventional reactor, for example a preparation reactor
• This third reactor can be in any form of reactor known to those skilled in the art, provided that it can perform its function in the device of the present invention.
• a third reactor in the form of a tubular reactor for example such as those mentioned above, will be preferred.
• the device for implementing the method of the invention may be provided with one or connected to a line of expansion provided with one or more separators and possibly one or several activated carbon filters.
• a line of expansion provided with one or more separators and possibly one or several activated carbon filters.
• the line of relaxation allows to return to the atmospheric pressure in the reactor.
• a single line of expansion and separator may be sufficient for a device comprising several reactors. It is generally connected to a reactor, for example to the coated particle recovery reactor.
• the device may further comprise at least one automatic expansion valve coupled to a pressure sensor and a regulator and pressure programmer.
• a pressure sensor Preferably he will understand several.
• This expansion valve, this sensor and this regulator make it possible to ensure and control the safety of the device when it is used to implement the method of the invention.
• These valves, sensors and regulators may be those commonly used in devices for implementing processes in a pressurized medium.
• the synthesis reactor may furthermore comprise at least one temperature sensor connected to a temperature regulator and controller as well as an automatic expansion valve and a pressure sensor connected to a regulator and pressure programmer.
• a temperature regulator and controller As well as an automatic expansion valve and a pressure sensor connected to a regulator and pressure programmer.
• a pressure sensor connected to a regulator and pressure programmer.
• the synthesis reactor may furthermore comprise at least one temperature sensor connected to a temperature regulator and controller as well as an automatic expansion valve and a pressure sensor connected to a regulator and pressure programmer.
• a pressure sensor connected to a regulator and pressure programmer.
• the synthesis reactor may furthermore comprise at least one temperature sensor connected to a temperature regulator and controller as well as an automatic expansion valve and a pressure sensor connected to a regulator and pressure programmer.
• a pressure sensor connected to a regulator and pressure programmer.
• the synthesis reactor may furthermore comprise at least one temperature sensor connected to a temperature regulator and controller as well as an automatic expansion valve and a pressure sensor connected to a regulator and pressure programme
• this system preferably comprises one or more of the following elements, preferably all: a variable or adjustable flow injection system allowing the rapid introduction of precursors and / or coating materials (for example to implement the semi-continuous or continuous process); - A thermoregulated and removable tubular reactor for the development of inorganic or organic particles (eg continuous or semi-continuous process);
• a system for recovering dry or wet powders for example recovering powders in the form of dispersion solution in an appropriate aqueous or organic medium, for example an alcoholic medium;
• Possibility of direct coating by synthesis by adding a reactor in series (for example continuous or semi-continuous process).
• the present invention associating one or more of the aforementioned elements, preferably all, allows the synthesis and coating of particles according to a standardized protocol. This protocol is defined to obtain uniform sizes and distribution of coated particles.
• the synthesis may relate to inorganic or organic particles.
• the coating material which allows the coating of these particles can be in the same manner of inorganic or organic nature. It may be a coating material, also called coating agent, which may be chosen from the examples given below. It can be for example:
• a dispersing agent for example an organic deflocculating polymer or polyelectrolyte, acting on electrostatic repulsion or on steric stabilization.
• a crosslinking agent for example chosen from
• N, N'-methylenebisacrylamide, N, N'-bisacrylylcystamine, N, N'-diallyltartradiamide, etc. to obtain polyacrylamide gels crosslinked in a three-dimensional network for the insertion of different cations.
• a metallizing agent chosen for example from Ag, Pd, Pt, etc., used for its electrical conduction properties.
• the present invention makes it possible to implement a manufacturing of coated particles on an industrial scale. It allows synthesis in large amount of coated oxide powders, in particular nanophase powders of at least one oxide.
• FIG. 5 Diagram of a nozzle usable as a second reactor in the device shown in Figure 3 attached.
• the device presented in this example makes it possible to implement the method of the invention according to the first embodiment described above.
• This device is shown schematically in Figure 1 attached. It is based on a conventional supercritical CO2 synthesis reactor (R) connected to a supercritical CO2 supply means comprising a reserve of liquid CO2 (CO2), a condenser (cd), a pump (po) and a means heating (ch) of the CO2 injected into the reactor.
• a supercritical CO2 supply means comprising a reserve of liquid CO2 (CO2), a condenser (cd), a pump (po) and a means heating (ch) of the CO2 injected into the reactor.
• This reactor (R) serves as a reactor for synthesizing particles in supercritical CO2 medium and as a reactor for coating the synthesized particles. It is equipped with a stirring machine (ma) and baffles (pf). It may also be provided with a means for heating and regulating the temperature of the reagents present inside the reactor (not shown).
• the reactor is also connected to an injection system (I) which can be used, depending on the process implemented for the injection into the reactor of precursor materials particles and / or for the injection of the coating material or precursors thereof.
• the injection system is thermoregulated. It is also connected to the aforementioned CO2 reserve via a line (L ') provided with a control valve (Vr) (useful for example for applications using the RESS process).
• the injection system (I) comprises a pressure multiplier (mp) and a reactor (r) for containing or injecting the precursors (pr) of the coating material or the coating material, and before that, optionally, the precursor material of the particles.
• This injection system is also provided with a purge valve (Vp).
• Another type of injection system could be used, such as a metering pump or a syringe pump.
• This device also comprises a relaxation line (L) provided with a separator (S) and a pressure sensor (P), and a regulator and pressure programmer (RPP).
• L relaxation line
• S separator
• P pressure sensor
• RPP regulator and pressure programmer
• FIG. 2 appended shows a diagram (seen from above in section) of connection between the reactor (R) and the injection system (I) making it possible to overcome the problem of clogging of the injection tube after the step of particle synthesis, and facilitate the intermediate cleaning of the system.
• Two injection tubes are provided for injection into the reactor (R): The first tube (tl) is used to inject the synthesis materials of the particles. The second tube (t2) is used to inject the coating material or its precursors.
• An injection system (I) as indicated above is provided.
• the first type of process consists of pre-filling the reactor (R) with a precursor solution (sp) of the particles to be synthesized and then raising the temperature and pressure of CO2 to the system so as to reach the operating conditions selected for the synthesis of particles in said reactor.
• the second type of synthesis process consists of injecting a solution of precursor (sp) with the injection system (I) into the reactor previously charged with CO2 at the temperatures and synthesis pressures.
• the coating is carried out after cleaning the introduction line of the injection system (I).
• An important step is between the step of synthesis of the particles and the coating step, so that the reactor (R) is found after injection under conditions favorable to the coating (temperature, pressure, etc.).
• Examples 4 and 5 below are examples of use of the device described in this example for the manufacture of coated particles.
• Example 2 Device According to the Invention for Use in the Continuous Manufacture of Coated Particles According to the Process of the Invention
• the device presented in this example can be used for continuous synthesis of coated particles. It is shown schematically in Figure 3 attached. This device is described below in four parts.
• a first part (1) of this device is used for the synthesis of oxide particle powders. It consists of a tubular reactor
• thermoregulated and removable in order to be able to modify the geometry (coil of different sizes) and adjust the residence time.
• This tubular reactor is connected to a reserve of liquid CO2 (CO2), to a reserve (re) of precursor solution (sp) in the form of a tank - possibly provided with a mechanical or magnetic stirring means (ma) and a reserve of reagents (water, alcohols, gases, etc.) referenced “H2O” in the figure. Pumps (in) to continuously supply the reactor (rtl) with CO2, precursor solutions and reagents.
• Pipes (t) connect these different elements.
• Flow control valves (vr) and on / off valves (vo) respectively regulate material flows in the device and depressurize the device.
• a second part (2) is dedicated to the coating (coating zone). It comprises a second reactor (rt2) for contacting the synthesized particles with the coating material or its precursor.
• This second reactor is a nozzle (B) such as that represented in FIG. 5, comprising an inlet (eps) for the synthesized particles, an inlet (eme) for the coating material or its precursors, and an outlet (so) for the coated particles or a mixture of the particles and the coating material or its precursors.
• This nozzle makes it possible, for example, to implement RESS or SAS processes for coating the particles.
• a third part (3) of the device allows the preparation of the coating material or its precursors.
• two means of preparation (srl) and (sr2) (each constituting a "third reactor") are mounted. According to the process for manufacturing the coated particles used, the most appropriate means is chosen.
• the means (srl) or (sr2) which is not used can of course be absent from the device.
• the means “srl” comprises a tubular reactor for continuous preparation of the coating material or its precursors.
• the means “sr2” comprises a conventional reactor for the precipitation or solubilization of the coating material or its precursors.
• RESS an extraction unit in the form of the tubular reactor (rt3) is used for the solubilization of the CO 2 coating agent (srl).
• This extraction unit is connected to the reserve of liquid CO 2 (CO 2).
• a conventional reactor (rc) may contain an organic or inorganic solution for solubilizing the coating agent or its precursors.
• This conventional reactor (rc) may be provided with a mechanical or magnetic stirring means (ma).
• This device also comprises automatic flow valves (VDA), lines of relaxation (L) provided with a separator (S) and a pressure sensor
• This montage is versatile. It can be used independently, for example, for the synthesis of oxide particles by chemical reaction, for shaping of different materials by RESS or SAS processes and for a synthesis of coated oxide particles, for example by RESS or SAS reaction.
• Examples 6 and 7 below are examples of use of the device described in this example for the manufacture of coated particles.
• the first and second reactors are tubular and mounted in series, so that the output of the first reactor (rtl) is connected to the inlet of the second reactor (rt2) via a transfer means which is here a tube (t) for transporting the synthesized oxide particles from the first to the second reactor in a supercritical medium.
• the reagents are those useful for the manufacture of particles oxide.
• the reagents are those constituting the coating material or its precursor.
• this device also comprises, as the device shown in Figure 3, several recovery baskets.
• the oxide particles manufactured continuously in the first reactor (rtl) are injected continuously into the second reactor (rt2) at the same time as the coating material or its precursors.
• the coated particles are recovered continuously from the second reactor (rt2) alternately in the recovery baskets.
• Example 8 below is an example of use of this device for the manufacture of coated particles.
• the crystallization temperature is 200-250 ° C. at 300 bars of CO 2 .
• a gel is formed in the solution after 20 minutes of aging, before treatment with CO 2 , which makes it impossible to inject the precursor solution. Only the batch process (where the solution undergoes a temperature rise and pressure and then a plateau at the crystallization temperature of between 15 minutes and 4 hours) is envisaged for this type of solution.
• the crystallization temperature is from 350 ° C. to 300 bars of CO 2 .
• the solution obtained is transparent and fluid. Both processes (batch or injection) can be envisaged.
• the precursors used are a monomer
• the synthesis temperature is between 60 and 150 0 C and the pressure between 100 and 300 bar. A plateau of 3 to 5 hours at the synthesis temperature is necessary for the reaction. A 15-minute CO2 sweep followed by a shutdown of the reactor thermoregulation followed by a readjustment of the pressure in order to reach the conditions necessary for the coating constitute the different phases of the intermediate step between the synthesis. and the coating.
• the characteristics of the particles depend on the solvent used.
• coated particles made in this example are titanium dioxide particles coated with polymethyl methacrylate or another polymer (such as polyethylene glycol (PEG)).
• PEG polyethylene glycol
• the synthetic precursor used to prepare the titanium dioxide is titanium tetraisopropoxide.
• This precursor is an alkoxide relatively soluble in CO2. It can be used pure or in solution in isopropanol, it can be either put directly into the reactor or injected. Water is then injected into the reactor at the synthesis temperature (> 250 ° C.) to allow the hydrolysis of the precursor. The reaction can also be carried out without water, the titanium dioxide being then obtained by thermal decomposition of the precursor.
• Particles ranging from 50 to 600 nm and crystallite sizes between 10 and 30 nm can be obtained.
• the coating step is equivalent to that described in Example 4 with the same polymer or a polyethylene glycol.
• Another coating technique consists in injecting a solubilized polymer into carbon dioxide (for example, fluoropolymer, polysiloxane, polyethylene glycol) in the reactor charged with carbon dioxide (at a temperature and pressure sufficiently high for the polymer to be solubilized) then let the temperature and the pressure of the reactor down until precipitation of the polymer on the particles.
• a final coating technique consists in injecting a polymer solubilized in carbon dioxide (for example, fluoropolymer, polysiloxane or polyethylene glycol) into the reactor with a low carbon dioxide charge (at a temperature and a pressure sufficiently low to that the polymer precipitates).
• Example 6 First Example of Manufacture of Coated Particles According to the Process of the Invention Using the Device Described in Example 2 in Which the Second Reactor Is a Nozzle
• coated particles made in this example are ceramic oxide particles coated by a RESS process. The process is carried out so as to obtain continuous manufacture.
• the particles may be, for example, gadolinium-doped ceria or yttrium-doped zirconia (injection synthesis described in Example 4).
• a solution prepared for example from cerium and gadolinium acetates in isopropanol and nitric acid is injected into the first reactor simultaneously with carbon dioxide.
• the reactor 1 must be thermostated at a temperature above 150 0 C to obtain a crystallized powder.
• the powder is transferred to the rt2 nozzle.
• gadolinium doped ceria was synthesized in batch mode. with different solvents. Different morphologies have been obtained: platelets, rods, fibers, porous spheres. Specific surfaces greater than 100 m 2 / g could be measured. The synthesis of these powders by injection has not been realized. By adequacy with the results obtained for the doped zirconia, the use of suitable operating conditions, with this injection method, should make it possible to obtain monodisperse spherical particles of nanometric sizes (30 to 300 nm).
• a coating agent soluble in CO 2 must be used. It may be for example paraffin.
• the solubilization is done in the reactor rt3.
• the CO 2 loaded with coating agent is transported to the nozzle rt 2 .
• the recovery basket is at atmospheric pressure and ambient temperature (or low CO 2 pressure and low temperature), so at the exit of the nozzle, the coating agent (solids at ambient conditions) precipitates on the particles.
• Example 7 Second Example of Manufacture of Coated Particles According to the Method of the Invention Using the Device Described in Example 2 in Which the Second Reactor (Rt2) Is a Tubular Reactor
• the coated particles made in this example are ceramic oxide particles coated by an SAS method.
• the process is carried out so as to obtain continuous manufacture.
• the particles may for example be TiO 2 titanium dioxide.
• the precursor of the oxide, titanium tetraisopropoxide is injected into the first reactor simultaneously with CO2 and water (3 arrivals).
• the reactor 1 must be thermostated at a temperature above 250 0 C to obtain a crystallized powder.
• the powder is transferred to the rt2 nozzle.
• the characteristics of the titanium powders obtained are identical to those of Example 5.
• a coating agent insoluble in CO2 must be used.
• a solution of the precursor must be prepared. It may be, for example, a polymer solubilized in a suitable organic solvent.
• the coating agent solution is in (rc) and then transported to the nozzle (rt2).
• the nozzle (rc) allows the coating agent to come into contact with the CO2, the coating agent precipitates on the particles.
• Example 8 Example of Manufacture of Coated Particles According to the Method of the Invention Using the Device Described in Example 3
• the silica synthesis is equivalent to the synthesis described above in Example 7.
• the synthesized particles are transferred to a second tubular synthesis reactor rt2.
• the characteristics of the silica powders obtained by this process are not known, but amorphous silica powders were obtained by the batch process at 100 ° C., the particles obtained are submicron and porous and the powders have high specific surfaces (> 700 m 2 / g).
• the precursor solution is prepared beforehand (re2 in FIG. 4); it may be a solution of polymerization precursors as in Example 4 (monomer, surfactant, initiator, solvent), an oxide precursor solution as for the synthesis (cerium acetate in isopropanol) or a noble metal precursor solution (platinum precursor in water).
• the solution is injected into rt2 simultaneously with the particles.
• the reaction of the coating agent precursors occurs in rt2 around the particles synthesized in rt1. It can be a polymerization reaction (60 to 150 ° C.), a sol-gel reaction or a precipitation (150 to 500 ° C.) or a thermal decomposition (150 to 500 ° C. ).
• the coating therefore occurs in RT2 and then the recovery of the coated particles is at the outlet of this second reactor.
• the particles prepared are particles of yttriated zirconia.
• a solution of precursors (zirconium hydroxyacetate and yttrium acetate placed in proportions so as to obtain, finally, 3 mol% of Y2O3 relative to ZrC> 2) is injected at a low speed (0.19 m / s ) in the reactor of FIG. 1, stirred at 400 rpm under a CO2 pressure of 230 bars and a temperature of 350 ° C.
• the pressure in the reactor after injection is 300 bars.
• the supercritical treatment was maintained 1 hour before depressurization of the reactor and return to ambient temperature.

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