Process for co-casting and / or co-extrusion by phase inversion using a water gel with adapted viscosity

Abstract

The present invention relates to the implementation of processes for co-casting and / or co-extrusion coupled with phase inversion. More precisely, the present invention relates to a process for co-casting and / or co-extrusion by phase inversion comprising the following steps: - a step of shaping by co-casting and / or co-extrusion of a polymer solution loaded with ceramic powder and a gelled water; and - a step of phase inversion, the steps of casting or extrusion and phase inversion being carried out simultaneously. The present invention also relates to a strip, preferably a ceramic strip or ceramic-metal strip, obtained by the process as defined hereinbefore. The present invention also relates to a tube, preferably a ceramic tube, obtained by the process as defined hereinbefore. The present invention also relates to the use of the process as defined hereinbefore for the manufacture of strips, preferably ceramic strips and / or ceramic-metal strips or tubes, preferably ceramic tubes. The present invention also relates to the use of the process as defined hereinbefore or of the strip, preferably of the ceramic strip, as defined hereinbefore, or of the tube, preferably of the ceramic tube as defined hereinbefore, for the manufacture of membranes, preferably ceramic membranes such as ceramic-metal (cermet) membranes, the manufacture of filters, preferably ceramic filters and / or the manufacture of electrochemical cells, preferably the manufacture of fuel cells and the manufacture of electrolysers.

Description

[0001] CO-CASTING AND / OR CO-EXTRUSION PROCESS BY PHASE INVERSION USING A WATER GEL WITH ADAPTED VISCOSITY

[0002] FIELD OF THE INVENTION

[0003] The field of the invention relates to the implementation of co-casting and / or co-extrusion processes coupled with phase inversion.

[0004] TECHNICAL BACKGROUND

[0005] Conventionally used phase inversion techniques generally require the use of three major compounds: a polymer, a solvent, and a non-solvent (also called a "non-solvent bath" or "non-solvent basin" or "coagulant" or "coagulation bath"). To implement these techniques, the solvent must be able to dissolve the polymer, unlike the non-solvent. The common name for the latter (non-solvent) comes from its opposite effect to the solvent: it must not dissolve the polymer and causes its precipitation, consequently trapping the ceramic powder contained in the polymer solution. For chemical exchanges to take place, the solvent and the non-solvent must be soluble in each other.

[0006] Phase inversion processes using co-casting to prepare planar membranes or co-extrusion to prepare tubes, preferably micro-tubes, such as ceramic membranes or ceramic tubes, preferably ceramic membranes or ceramic micro-tubes, comprise either a tape casting step or an extrusion step.

[0007] The principle of the phase inversion tape casting process is to first perform conventional tape casting and then, in a second step, to bring the resulting cast tape into contact with a non-solvent, usually water. The so-called phase inversion process takes place during the second step when the solvent contained in the cast tape comes into contact with the non-solvent contained in the bath. At the interface between the solvent and the non-solvent, a diffusion mechanism is triggered and leads to a thermodynamically unstable system, which causes phase separation and the precipitation of a polymer network in the ceramic cast tape. The solvent migrates into the coagulation bath while the non-solvent migrates into the ceramic tape. As long as thermodynamic equilibrium is not reached, the diffusion of the solvent and the non-solvent continues and the pores formed in the membrane will grow in accordance with the diffusion front (interface).The solidification of the polymer is related to the difference in solubility and the kinetics of the diffusion interplay between the solvent and the non-solvent, which sets the final microstructure of the strip. The ceramic powder must also be distributed homogeneously in the polymer network of the strip. An asymmetric microstructure is commonly observed, with a layer of pores in the form of long channels directed perpendicular to the diffusion front (closest to the interface of the starting stack) and another layer with a more homogeneous porosity (called the spongy porosity layer). In other words, the prior art phase inversion strip casting processes include the steps listed below in the following order: - Step 1: Preparation of a polymer solution consisting of a polymer dissolved in a solvent;

[0008] - Step 2: Dispersion of a ceramic powder in the polymer solution to obtain a homogeneous ceramic suspension;

[0009] - Step 3: Forming by casting the ceramic suspension into a strip, called a ceramic strip;

[0010] - Step 4: Transfer of the ceramic strip into a non-solvent bath by immersion, which has the effect of triggering the phase inversion process and solidifying the ceramic strip by exchange between the non-solvent and the solvent. The immersion time of the strip depends on the kinetics of the phase inversion mechanism (interdiffusion);

[0011] - Step 5: Phase inversion in the non-solvent bath;

[0012] - Optional step 6: Cutting the solidified ceramic strip, also called “membrane”, to the desired dimensions, in order to create the final object;

[0013] - Optional step 7: Drying of the final object and evaporation of the non-solvent and the solvent, thus creating the porosity network; and

[0014] - Optional step 8: Debinding and sintering of the membranes, with a view to consolidating the ceramic network.

[0015] The principle of the phase inversion extrusion process is based on the same foundation and the same steps as for phase inversion tape casting. Indeed, it involves replacing the tape casting shaping step (step 3) with an extrusion shaping step, then placing the resulting extrudate in a non-solvent bath (step 4), generally water. The mechanisms occurring during the phase inversion process are identical to those described previously with the phase inversion tape casting process. This change in process may require an adjustment of the viscosity of the ceramic suspension, before the shaping step, by modifying the loading rate of the ceramic powder (step 2) and / or the polymer concentration in the solution (step 1). The term ceramic paste is then preferred to that of ceramic suspension (step 2).

[0016] However, current processes do not allow the shaping step by strip casting or extrusion of the ceramic suspension (step 3) and the triggering of the consolidation mechanism by phase inversion of the ceramic membrane (step 4) to be carried out simultaneously. Two separate steps (steps 3 then 4) are necessary and require the handling of the extrusion strips or profiles, which will have the effect of generating stresses in the membrane, which will be detrimental to the further development of the final part.

[0017] Indeed, currently, the transfer into a non-solvent basin is often carried out manually and constitutes a separate step. In addition, the use of a non-solvent basin generates a large quantity of chemical waste. The solvent contained in the polymer solution loaded with ceramic powder (ceramic suspension) diffuses into the non-solvent basin, thus contaminating the entire basin, during the phase inversion step.

[0018] The present invention aims to remedy all or part of the drawbacks of the state of the art cited above.

[0019] Surprisingly and unexpectedly, the present inventors have developed a co-casting (or co-extrusion) process by phase inversion in which a single step, combining the aforementioned steps 3 and 4, is necessary, while eliminating the use of a non-solvent pool. In particular, the present inventors have developed a co-casting and / or co-extrusion process coupled with phase inversion, in which a ceramic suspension or paste (also called a polymer solution loaded with ceramic powder) is cast or extruded simultaneously with a non-solvent gel (gelled water). Advantageously, the layer of non-solvent gel (preferably less than 1 mm thick) then directly covers the ceramic strip or extrudate in a single co-casting and / or co-extrusion step.Advantageously, the phase inversion is thus triggered during the shaping step, at the interface between the ceramic suspension and the non-solvent gel. Advantageously, the intermediate step of immersing the ceramic strip in the non-solvent bath is eliminated. Advantageously, the use of a water gel, replacing the non-solvent bath (generally water), makes it possible to drastically reduce the quantity of chemical waste produced.

[0020] The present invention thus makes it possible to obtain ceramic membranes or metallic ceramic membranes (CERMET) of variable geometries.

[0021] SUMMARY OF THE INVENTION

[0022] A first subject of the present invention relates to a co-casting and / or co-extrusion process by phase inversion comprising the following steps

[0023] - a shaping step by co-casting and / or co-extrusion of a polymer solution loaded with ceramic powder and gelled water, and a phase inversion step, the casting or extrusion and phase inversion steps being carried out simultaneously.

[0024] The present invention also relates to a strip, preferably a ceramic strip or a metallic ceramic strip, obtained by the method as defined above.

[0025] The present invention also relates to a tube, preferably a ceramic tube, obtained by the method as defined above.

[0026] The present invention also relates to the use of the method as defined above for the manufacture of strips, preferably ceramic strips and / or metallic ceramic strips or tubes, preferably ceramic tubes.

[0027] The present invention also relates to the use of the method as defined above or of the strip, preferably of the ceramic strip, as defined above, or of the tube, preferably of the ceramic tube as defined above, for the manufacture of membranes, preferably of ceramic membranes such as metallic ceramic membranes (CERMET), the manufacture of filters, preferably of ceramic filters and / or the manufacture of electrochemical cells, preferably the manufacture of fuel cells and the manufacture of electrolysers. DETAILED DESCRIPTION

[0028] A first subject of the present invention relates to a co-casting and / or co-extrusion process by phase inversion comprising the following steps

[0029] - a shaping step by co-casting and / or co-extrusion of a polymer solution loaded with ceramic powder and gelled water, and a phase inversion step, the casting or extrusion and phase inversion steps being carried out simultaneously.

[0030] Thus, advantageously, a first object of the present invention relates to a co-casting and / or co-extrusion process by phase inversion which makes it possible to group together in a single step the following two steps:

[0031] - a shaping step by co-casting and / or co-extrusion of a non-solvent gel (gelled water) cast or extruded at the same time as a polymer solution loaded with ceramic powder (also called ceramic suspension or paste), and

[0032] - a phase inversion step, as soon as the ceramic strip or extrudate comes into contact with the non-solvent gel which covers it.

[0033] Preferably, the term "co" associated with the casting (or extrusion) steps means that the casting (or extrusion) of the non-solvent gel (gelled water) is carried out at the same time and covers the ceramic suspension (or paste) (also called polymer solution loaded with ceramic powder). Advantageously, the simultaneous shaping of the ceramic suspension or paste with the non-solvent gel makes it possible to instantly initiate the phase inversion process, eliminating the handling of the strips or extrudates and the non-solvent bath.

[0034] Advantageously, the present invention relates to a co-casting and / or co-extrusion process coupled with phase inversion (also called co-casting and / or co-extrusion process by phase inversion) based on an exchange between precursors (of variable viscosity such as liquid and pasty precursors), at the interface between two media of different compositions, when they are brought into contact.

[0035] Advantageously, the present invention makes it possible to couple the steps of shaping these precursors to the actual “phase inversion” step, not carried out until now.

[0036] Advantageously, a first object of the invention consists in simultaneously operating the shaping of ceramic suspensions (of variable viscosity) and the chemical process of phase inversion, by co-casting or co-extruding two suspensions of adapted and variable viscosity according to the geometry and the envisaged application. Advantageously, this co-casting and / or co-extrusion process coupled with phase inversion (also called co-casting and / or co-extrusion process by phase inversion) makes it possible to operate the following steps and reactions (or following mechanisms) in a single step:

[0037] - the shaping step by co-casting and / or co-extrusion of a polymer solution loaded with ceramic powder (also called ceramic suspension) and gelled water (also called pseudo-gel), and - the phase inversion reaction (or the phase inversion mechanism) between the solvent, in which the ceramic powder is suspended (in a polymer-rich medium), and the non-solvent gel (water gel). This step allows the instantaneous precipitation of the polymer, trapping the ceramic powder in a rigid matrix, and the creation of textured porosity by exchanges between the solvent and the non-solvent gel (water gel).

[0038] By "polymeric solution" is preferably meant a homogeneous mixture between two substances: a solvent and a solute. The solvent is the most abundant component of the system while the solute is the substance that is dissolved in the solution. In the present invention, the solute is a polymer or a mixture of polymers.

[0039] By "ceramic powder-filled polymer solution" or "ceramic suspension" is preferably meant a heterogeneous mixture (or heterogeneous system) in which ceramic powder particles are dispersed. In the present invention, the ceramic powder or the metallic ceramic powder (CERMET) is dispersed in the polymer solution.

[0040] Co-casting is preferably understood to mean processes for shaping ceramic suspensions such as tape casting. Casting is preferably used for low-viscosity ceramic suspensions. The term "co" preferably refers to the simultaneous casting of different layers.

[0041] Preferably, by "co-casting shaping" is meant the shaping of the ceramic suspension, i.e. casting it in the form of a strip. In particular, by "co-casting shaping" is preferably meant the simultaneous shaping of the water gel on the ceramic suspension, i.e. casting in the form of two strips of distinct precursors, superimposed and in intimate contact.

[0042] The term "co-extrusion" preferably refers to processes for shaping ceramic suspensions, such as micro-extrusion. Extrusion is preferably used for high-viscosity ceramic suspensions. The term "co" preferably refers to the simultaneous extrusion of different layers, preferably different profiles.

[0043] Preferably, by "co-extrusion shaping" is meant the shaping of the ceramic suspension, i.e. its extrusion in the form of a micro-tube. In particular, by "co-extrusion shaping" is preferably meant the simultaneous shaping of the ceramic suspension and the water gel, i.e. the extrusion of coaxial tubes, of distinct precursors and intimately in contact.

[0044] Preferably, by "phase inversion step" is meant the interdiffusion between the solvent in the ceramic suspension and the non-solvent corresponding to the gelled water.

[0045] Advantageously, the method of the present invention is characterized by the use of gelled water (or water with a gelling agent) to adjust the rheological properties of the water, in particular the viscosity and the yield stress, to the co-casting and / or co-extrusion process. In the method of the present invention, the casting (or extrusion) and phase inversion steps are carried out simultaneously (i.e. advantageously eliminating the water bath and the associated transfer of the strips). Advantageously, the phase inversion mechanism begins from the moment the polymer solution loaded with ceramic powder (also called ceramic suspension) and the gelled water (also called pseudo-gel) come into contact.In the present invention, the ceramic powder-filled polymer solution and the gelled water are cast (or extruded) simultaneously, and brought into contact during the casting (or extrusion) step, which triggers the phase inversion.

[0046] Preferably, by "casting (or extrusion) and phase inversion steps carried out simultaneously" it is preferably understood that the forming by strip casting (or by extrusion) and the species interdiffusion mechanism otherwise called "phase inversion" are triggered at the same time. Indeed, advantageously, the phase inversion mechanism is triggered when the gelled water is brought into contact with the polymer solution loaded with ceramic powder. Advantageously, with co-casting, the strips are cast at the same time (i.e. simultaneously) on top of each other. Similarly, advantageously, with co-extrusion, the extrusion of the ceramic suspension is carried out at the same time (i.e. simultaneously) as that of the gelled water inside and outside the ceramic tube being formed.

[0047] The co-casting step can be automated.

[0048] The co-extrusion step can be automated.

[0049] Advantageously, the present invention makes it possible to carry out in only one step the casting, preferably the strip casting, of the ceramic suspension and the phase inversion, and to manufacture strips with a microstructure whose porosity is textured and / or oriented, preferably textured and / or oriented according to the direction of the interdiffusion mechanism between the solvent and the non-solvent.

[0050] Advantageously, with co-casting, the geometry of the product obtained will be planar.

[0051] Advantageously, the present invention makes it possible to carry out the extrusion, preferably the extrusion of the ceramic suspension and the phase inversion, in only one step, and to manufacture membranes and / or tubes, preferably solid or hollow membranes and / or tubes, with a microstructure whose porosity is textured and / or oriented, preferably textured and / or oriented according to the direction of the interdiffusion mechanism between the solvent and the non-solvent.

[0052] Advantageously, with co-extrusion, the geometry of the product obtained will be tubular.

[0053] By "textured porosity" is preferably meant a porosity which has an anisotropic shape, or whose distribution has a porosity gradient over the thickness of the membrane or tube.

[0054] By "oriented porosity" is preferably meant a porosity, generally highly anisotropic, which is oriented in a preferred direction of space, preferably in a preferred direction of the volume of the sample. In the case of the invention, it is preferably meant an orientation perpendicular to the casting or extrusion plane. The microstructure may be in the form of channels or in the form of fibrous porosity. In particular, the porosity network associated with the microstructure of the membrane may be in the form of continuous channels (relatively rectilinear) or in the form of a more fragmented porosity (fibrous / spongy type).

[0055] Advantageously, in the method of the present invention, the non-solvent bath is replaced by a layer of non-solvent gel (gelled water).

[0056] Reducing the number of steps allows for better control of the phase inversion, and therefore improves the efficiency of the process, its reproducibility, its repeatability and limits the constraints which can be generated in the object obtained by the process of the invention.

[0057] In particular, replacing the manual step of transferring / transporting the strips in a non-solvent bath with the step of co-casting the ceramic suspension and gelled water, which can be automated, makes it possible to reduce the margin of error linked to the reproducibility of the transfer step and to the rigor of the operator during this same step and therefore to improve the reproducibility, repeatability and efficiency of the process.

[0058] In addition, the absence of a non-solvent bath makes it possible to reduce the consumption of non-solvent required for the operation of conventional processes and to limit the quantity of chemical waste. Advantageously, the use of a non-solvent gel (i.e., gelled water) in the process of the present invention makes it possible to use a relatively small quantity of non-solvent, thus generating a lower proportion of chemical waste.

[0059] Advantageously, the method of the present invention is simple and practical to implement.

[0060] Advantageously, the method of the present invention can be transposed to an industrial scale, automated and / or implemented continuously, thus facilitating industrialization.

[0061] Preferably, the polymer solution as defined above comprises between 2 and 20% by mass of polymer, preferably between 2 and 10% by mass of polymer, between 25 and 55% by mass of solvent, preferably between 35 and 50% by mass of solvent and between 0 and 10% by mass of additives, preferably between 0.5 and 5% by mass of additives. These values ​​are calculated relative to the total mass of said polymer solution.

[0062] Examples of polymers include, but are not limited to, polyethersulfones (PES or PESU), cellulose acetates (CA), polyamides, polysulfones (PSf), polyvinylidene fluorides (PVDF), polyacrylonitriles (PAN), polytetrafluoroethylenes (PTFE), polypropylenes (PP), polyethylenes (PE), polyvinyl alcohols (PVA), polyimides, polyetheretherketones (PEEK), polydimethylsiloxanes (PDMS), polycarbonates (PC), polyvinyl chlorides (PVC), or their derivatives, and mixtures thereof, preferably polyethersulfones (PES).

[0063] Examples of solvents include, but are not limited to, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), triethylphosphate (TEP), dimethylsulfoxide (DMSO), cyrene, and mixtures thereof, preferably N-methyl-2-pyrrolidone (NMP) and cyrene. Examples of solvents include, but are not limited to, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), triethylphosphate (TEP), dimethylsulfoxide (DMSO), and mixtures thereof, preferably N-methyl-2-pyrrolidone (NMP).

[0064] Advantageously, when the polymer is chosen from polyethersulfones (PES), the solvent will preferably be chosen from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), and mixtures thereof.

[0065] Advantageously, when the polymer is chosen from cellulose acetates (CA), the solvent will preferably be chosen from dimethylformamide (DMF), dimethylacetamide (DMAc), triethylphosphate (TEP), dimethylsulfoxide (DMSO), and mixtures thereof.

[0066] Advantageously, when the polymer is chosen from polysulfones (PSf), the solvent will preferably be chosen from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), and mixtures thereof.

[0067] Advantageously, when the polymer is chosen from polyvinylidene fluorides (PVDF), the solvent will preferably be chosen from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), triethylphosphate (TEP), dimethylsulfoxide (DMSO), and mixtures thereof.

[0068] Advantageously, when the polymer is chosen from polyacrylonitriles (PAN), the solvent will preferably be chosen from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), and mixtures thereof.

[0069] Advantageously, when the polymer is chosen from polyvinyl alcohols (PVA), the solvent will preferably be chosen from N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), and their mixtures.

[0070] Advantageously, when the polymer is chosen from polyetheretherketones (PEEK), the solvent will preferably be chosen from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylsulfoxide (DMSO), and mixtures thereof.

[0071] Advantageously, when the polymer is chosen from polycarbonates (PC), the solvent will preferably be chosen from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and their mixtures.

[0072] Advantageously, when the polymer is chosen from polyvinyl chlorides (PVC), the solvent will preferably be chosen from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), and mixtures thereof.

[0073] Examples of additives include, but are not limited to, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polymethyl methacrylate (PMMA), lithium chloride (LiCl), or derivatives thereof, and mixtures thereof, preferably polyvinylpyrrolidone (PVP). Advantageously, the gelling agent increases the viscosity of the water.

[0074] The non-solvent water is preferably distilled water.

[0075] Thus, advantageously, the gelled water comprises water, preferably distilled water, and a gelling agent.

[0076] Examples of gelling agents include, but are not limited to, cellulose binders, Karaya gum, Guar gum, cellulose gum such as cellulose derivatives and in particular methylcellulose, Tara gum, Tamarind gum, agar-agar, pectins, alginates, psyllium, or derivatives thereof, and mixtures thereof, preferably Karaya gum, Tara gum, Guar gum, Psyllium, methylcellulose, or mixtures thereof.

[0077] Preferably, examples of gelling agents include, but are not limited to, cellulose binders, Karaya gum, Guar gum, cellulose gum, Tara gum, Tamarind gum, agar-agar, pectins, alginates, or derivatives thereof, and mixtures thereof, preferably Karaya gum, Tara gum, Guar gum, methylcellulose, or mixtures thereof.

[0078] Depending on the percentage of gelling agent, the viscosity of the gelled water can be adjusted and adapted to the co-casting and co-extrusion process.

[0079] Advantageously, gelled water has rheological properties suitable for co-casting and co-extrusion processes, which are adjusted with the addition of the gelling agent.

[0080] Preferably, when the shaping step is carried out by co-extrusion, the viscosity of the gelled water as defined above is between 1 and 20 Pa.s -1 , preferably between 1 and 3 Pa.s- 1 .

[0081] Preferably, when the shaping step is carried out by co-casting, the viscosity of the gelled water as defined above is between 0.5 and 20 Pa.s' 1 , preferably between 1 and 3 Pa.s' 1 .

[0082] Preferably, the gelled water as defined above comprises between 80 and 99.5% by mass, preferably between 90 and 99% by mass, preferably between 90 and 98% by mass, and even more preferably between 94 and 96% by mass of water, preferably distilled water, and between 0.5 and 20% by mass, preferably between 1 and 10% by mass, preferably between 2 and 10% by mass, and even more preferably between 4 and 6% by mass of a gelling agent. These values ​​are calculated relative to the total mass of said gelled water.

[0083] Preferably, the gelled water is prepared by adding the gelling agent as defined above to water, preferably distilled water, with stirring, preferably with magnetic stirring or with a mixer.

[0084] The gelled water thus prepared can be stored at room temperature (between 15 and 25°C) or in a refrigerator. Preferably, the gelled water thus prepared is stored in a refrigerator, at a temperature between 4 and 8°C, and even more preferably at approximately 6°C, for preferably at least 24 hours before being used for the phase inversion step.

[0085] Advantageously, the gelled water thus prepared can be stored for several months at a temperature between 4 and 25°C, preferably between 4 and 8°C, and even more preferably at approximately 6°C.

[0086] Advantageously, the ceramic powder is dispersed in the polymer solution. The composition and properties of the ceramic suspension can be adapted according to the intended application (for filtration and the manufacture of electrochemical devices, metallic ceramic mixtures called CERMET are produced). The rheological properties of these suspensions are optimized according to the geometry (flat strips or tubes) and the shaping method chosen (casting or extrusion).

[0087] Preferably, the polymer solution loaded with ceramic powder comprises between 1 and 80% by mass, preferably between 35 and 70% by mass of ceramic powder. These values ​​are calculated relative to the total mass of the polymer solution loaded with ceramic powder.

[0088] Examples of ceramic powder include, but are not limited to, alumina (AI2O3), yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ) (also referred to as scandia-stabilized zirconia (ScSZ)), gadolinium-doped ceria (GDC), samarium-doped ceria (SDC), strontium-magnesium-doped lanthanum gallate (LSGM), rare-earth silicates such as apatite phases, or mixtures thereof with metal oxides such as nickel oxide (NiO), and in particular: NiO / YSZ, NiO / ScSZ, NiO / GDC, NiO / SDC, NiO / LSGM (these oxides are preferably used for SOFC and SOEC applications), preferably zirconia stabilized with yttrium oxide (YSZ), nickel oxide (NiO) or their mixtures (YSZ and NiO).

[0089] Preferably, the polymer is selected from polyethersulfones (PES), the solvent is selected from N-methyl-2-pyrrolidone (NMP), cyrene or mixtures thereof, the additive is polyvinylpyrrolidone (PVP) and the ceramic powder is yttrium oxide stabilized zirconia (YSZ), nickel oxide (NiO) or mixtures thereof (YSZ and NiO).

[0090] Advantageously, the ceramic suspension comprising the constituents as defined previously and in the proportions as defined previously makes it possible to obtain a strip or an extrusion profile whose microstructure has a textured and / or oriented porosity throughout the thickness of the object.

[0091] Preferably, the polymer solution as defined above is prepared by dissolving, preferably completely, the polymer as defined above in the solvent as defined above in the presence of the additive as defined above.

[0092] Preferably, the ceramic suspension as defined above is prepared by adding a ceramic powder as defined above to the polymer solution as defined above. The ceramic suspension as defined above can be prepared using any device for mixing the different constituents of said ceramic suspension.

[0093] For example, the ceramic suspension as defined above can be prepared in a planetary mill or mixer with blades or rotor which promotes tangential shear forces during mixing of the solution.

[0094] According to a particular embodiment, the polymer solution as defined above is prepared in a planetary mill (preferably with zirconia grinding balls of 10 mm diameter) by dissolving the polymer as defined above in the solvent as defined above in the presence of an additive as defined above, preferably in a planetary mill for a time interval of between 30 min and 90 min, preferably for approximately 60 min with a rotation speed of between 200 rpm and 300 rpm, preferably approximately 260 rpm, until a homogeneous polymer solution is obtained to which the ceramic powder is then added to obtain a ceramic suspension.According to this same embodiment, a step of homogenization of the components is then carried out for a time interval of between 10h and 15h, preferably for approximately 12h with a rotation speed of between 100 rpm and 160 rpm, preferably approximately 130 rpm.

[0095] Preferably, the phase inversion co-casting process is carried out using a double-tank shoe.

[0096] By "double tank shoe" we preferably mean a device composed of two separate tanks, separated by a wall, into which suspensions of different types are poured. Advantageously, this device allows the simultaneous pouring of two materials with different properties.

[0097] The step of simultaneous casting of the ceramic suspension and the gelled water, also called the “co-casting” step, can be carried out with a casting bench or with an extruder (“co-extrusion” step).

[0098] By "casting bench" is preferably meant a device consisting of a shoe, preferably made of stainless steel, and a flat support for performing the casting. PET (polyethylene terephthalate) plates and / or aluminum plates can be used as a flat support. The shoe can consist of two tanks into which the ceramic suspension and the gelled water as defined above can be poured as well as two knives. Advantageously, the height of the knives is adjustable as is the speed of movement of the shoe, which makes it possible to control the thickness of the cast layers. Advantageously, by moving at a constant speed, the shoe spreads the ceramic suspension on the support and the layer of gelled water on top, thus forming layers with a homogeneous thickness and microstructure.

[0099] By "extruder" is preferably meant a system allowing a liquid, preferably a high viscosity liquid (paste), under the action of pressure, to flow into a nozzle or die whose geometry makes it possible to obtain the shape of the desired object, in our case a cylinder, a tube or a micro-tube. By "phase inversion step" is preferably meant a step during which the diffusion mechanism, preferably interdiffusion, between the solvent and the non-solvent operates, leading to the formation of textured and / or oriented porosity. In practice, this step preferably corresponds to the time during which the gelled water layer is in contact with the strip, preferably the ceramic strip.

[0100] The phase inversion step can be carried out for a duration of between 1 min and 10 h, preferably between 10 min and 1 h, and even more preferably for approximately 20 min.

[0101] Advantageously, during the phase inversion step, the strips are left in the casting bench.

[0102] The method according to the present invention may further comprise a step of washing the strips obtained at the end of the phase inversion step, preferably with water, and even more preferably with distilled water.

[0103] The method according to the present invention may further comprise separate steps of drying, debinding, pre-sintering and / or sintering to remove all or part of the organic materials present in the membrane.

[0104] Preferably, the drying step is carried out for a period of between 1 and 30 minutes, preferably between 5 and 25 minutes and even more preferably approximately 10 minutes at a temperature of between 20 and 100°C, preferably between 40 and 60°C and even more preferably approximately 50°C.

[0105] Preferably, the debinding step is carried out with a temperature rise ramp of between 0.1°C / min and 3°C / min, preferably between 0.2°C / min and 1°C / min and even more preferably of approximately 0.3°C up to a temperature of between 100°C and 800°C, preferably between 400°C and 650°C and even more preferably of approximately 550°C.

[0106] Preferably, the pre-sintering step is carried out following the debinding step with a temperature rise ramp of between 3°C / min and 10°C / min, preferably between 4°C / min and 7°C / min and even more preferably of approximately 5°C / min, up to a temperature of between 800°C and 1300°C, preferably between 1000 and 1200°C and even more preferably of approximately 1100°C, for a duration of between 10 and 120 minutes, preferably between 30 and 90 minutes and even more preferably of approximately 60 minutes.

[0107] Preferably, the sintering step is carried out with a temperature rise ramp of between 3°C / min and 10°C / min, preferably between 4°C / min and 7°C / min and even more preferably of approximately 5°C / min, up to a temperature of between 1200°C and 1600°C, preferably between 1300°C and 1500°C and even more preferably of approximately 1400°C, for a duration of between 30 and 340 minutes, preferably between 60 and 180 minutes and even more preferably of approximately 120 minutes.

[0108] Another object of the present invention relates to a strip, preferably a ceramic strip or a metallic ceramic strip, obtained by the method as defined above. Another object of the present invention relates to a tube, preferably a ceramic tube, obtained by the method as defined above.

[0109] Another object of the present invention relates to the use of the method as defined above for the manufacture of strips, preferably ceramic strips and / or metallic ceramic strips or tubes, preferably ceramic tubes.

[0110] Advantageously, the strips, preferably the ceramic strips thus obtained, have a textured porosity and / or porosity oriented in a spatial direction, preferably in a preferred direction of the volume of the sample.

[0111] Advantageously, the tubes, preferably the ceramic tubes thus obtained, have a textured porosity and / or porosity oriented in a spatial direction, preferably in a preferred direction of the volume of the sample.

[0112] The present invention also relates to the use of the method as defined above or of the ceramic strip as defined above or of the tube, preferably of the ceramic tube as defined above, for the manufacture of membranes, preferably of ceramic membranes such as metallic ceramic membranes (CERMET), the manufacture of filters, preferably of ceramic filters, and / or the manufacture of electrochemical cells, preferably the manufacture of fuel cells and the manufacture of electrolysers and more preferably the manufacture of solid oxide electrochemical cells such as solid oxide fuel cells and the manufacture of solid oxide electrolysers.

[0113] Preferably, the present invention also relates to the use of the method as defined above for the manufacture of flat membranes, preferably flat ceramic membranes, having a microstructure with oriented porosity in the form of microchannels.

[0114] Examples of fuel cells include, but are not limited to, solid oxide fuel cell (SOFC) cells.

[0115] Examples of electrolyzers include, but are not limited to, high temperature electrolyzers (Solide Oxide Electrolysis Cell - SOEC).

[0116] The membranes, preferably ceramic membranes (preferably zirconia, or yttria zirconia, or alumina AI2O3), thus manufactured can be used in the environmental field, for example for the filtration of gases or water (eg in the context of pollution control processes or the reprocessing of fumes or fluids such as water).

[0117] Filters, preferably ceramic filters, thus produced can be used in the field of metallurgy, for example to remove slag or impurities during casting.

[0118] The membranes and electrochemical cells, such as fuel cells and electrolysers, thus manufactured can be used in the energy sector, for example for the manufacture of solid oxide fuel cell (SOFC) cells, high temperature electrolysers (HTE) but also oxygen-separating ceramic membranes.

[0119] DESCRIPTION OF FIGURES

[0120] [Figure 1] Cross-sectional view of the shoe allowing co-casting of example 1 and example 2.

[0121] [Figure 2] Micrograph of a ceramic strip obtained by the phase inversion co-casting process of Example 1.

[0122] [Figure 3] Micrograph of a ceramic strip obtained by the phase inversion co-casting process of Example 2.

[0123] [Figure 4] Sectional view of the co-extrusion principle of example 3.

[0124] [Figure 5] Micrograph of a ceramic microtube obtained by the phase inversion co-extrusion process of Example 3.

[0125] [Figure 6] Micrograph of the microstructure of a ceramic microtube obtained by the phase inversion co-extrusion process of Example 3.

[0126] [Figure 7] SEM micrograph of membranes made by phase inversion co-casting using different solvents: a. Cyrene (example 4) and b. NMP (example 1).

[0127] [Figure 8] Micrograph of a ceramic strip (3YSZ-NiO) obtained by the phase inversion co-bonding process of Example 5.

[0128] [Figure 9] Rheogram of the gels from Example 6.

[0129] [Figure 10]: SEM micrographs of ceramic membranes of Example 7 obtained by co-coating according to different PVP contents: a. 0wt% PVP, b. 1wt% PVP, c. 3wt% PVP and d. 5wt% PVP.

[0130] EXAMPLE 1: PHASE INVERSION IN LOW-VISCOSITY SUSPENSIONS (BAND CASTING OF YTTRIATED ZIRCONIA POWDER)

[0131] This example is given for illustration purposes only and does not constitute a limitation of the present invention.

[0132] This example targets applications such as water filtration. Step 1: Preparation of the gelled water

[0133] 5% by mass of Karaya gum (Sigma-Aldrich) is added to distilled water (95% by mass of distilled water) under magnetic stirring. Once the Karaya gum is dissolved in the distilled water, the preparation is placed in the refrigerator at 6°C for at least 24 hours.

[0134] Step 2: Preparation of the ceramic suspension

[0135] The polymer (Polyethersulfone, Ultrason E 2020P, BASF), the solvent (N-methyl-2-pyrrolidone, Aldrich) and the additive (polyvinylpyrrolidone, Sigma-Aldrich) are introduced into a planetary mill which is rotated for 1 h at a rotation speed of 260 rpm. The polymer is thus completely dissolved in the solvent. The polymer, the solvent and the additive thus form a polymer solution.

[0136] In the planetary mill, the ceramic powder (yttrium-stabilized zirconia [8%mol], Tosoh), is added to the polymer solution thus prepared and a step of homogenization of the components is carried out for 12 hours at 130 rpm to obtain the ceramic suspension.

[0137] The mass quantities of each compound are presented in the table below.

[0138] Table 1: Example of a formulation for preparing a ceramic suspension with yttrium-stabilized zirconia powder (8 mol%)

[0139] Step 3: Co-casting: strip casting

[0140] The co-casting of the ceramic suspension and the gelled water is carried out with a "casting bench" consisting of a stainless steel shoe (shown in Figure 1) and a flat support for performing the casting. PET (polyethylene terephthalate) plates are used as support. The shoe consists of two reservoirs (1) and (2) as well as two knives (3) and (4). The partition (5) corresponds to the front of the shoe. The partitions (6) and (7) allow the height of the knives (3) and (4) to be adjusted, respectively, and their alignment to be maintained.

[0141] The ceramic suspension and gelled water prepared in steps 1 and 2 are poured into tanks (1) and (2) respectively.

[0142] The height of the knife (3) is adjusted to 400 pm and the height of the knife (4) is adjusted to 800 pm. The moving speed of the shoe is set to 2.40 m.min' 1 . Moving at a constant speed of 2.40 m.min' 1, the shoe spreads the ceramic suspension on the support and the layer of gelled water on top, forming layers with a homogeneous thickness and microstructure.

[0143] The strips thus obtained are then left for 20 min in the casting bench for the phase inversion step.

[0144] The strips are then washed with distilled water.

[0145] The strips are then dried in an oven at 50°C for 10 minutes on Mylar paper (silicone paper).

[0146] The strips thus obtained have a microstructure with textured porosity throughout the thickness of the strip (see figure 2).

[0147] EXAMPLE 2: PHASE INVERSION IN LOW-VISCOSITY SUSPENSIONS (BAND CASTING OF A CERMET [NiO-YSZ])

[0148] This example is given for illustration purposes only and does not constitute a limitation of the present invention.

[0149] This example targets applications such as SOFC and / or SOEC electrochemical cells.

[0150] Step 1: Preparation of the gelled water

[0151] 5% by mass of Karaya gum (Sigma-Aldrich) is added to distilled water (95% by mass of distilled water) under magnetic stirring. Once the Karaya gum is dissolved in the distilled water, the preparation is placed in the refrigerator at 6°C for at least 24 hours.

[0152] Step 2: Preparation of the ceramic suspension

[0153] The polymer (Polyethersulfone, Ultrason E 2020P, BASF), the solvent (N-methyl-2-pyrrolidone, Aldrich) and the additive (polyvinylpyrrolidone, Sigma-Aldrich) are introduced into a planetary mill which is rotated for 1 h at a rotation speed of 260 rpm. The polymer is thus completely dissolved in the solvent. The polymer, the solvent and the additive thus form a polymer solution.

[0154] In the planetary mill, the ceramic powders (yttrium-stabilized zirconia [8%mol], Tosoh, and nickel oxide, Inframat advanced materials), are added to the polymer solution thus prepared and a step of homogenization of the components is carried out for 12 hours at 130 rpm to obtain the ceramic suspension.

[0155] The mass quantities of each compound are presented in the table below.

[0156] Table 2: Example of a formulation for preparing a ceramic suspension with yttrium-stabilized zirconia powder (8 mol%) and nickel oxide powder

[0157] Step 3: Co-casting: strip casting

[0158] The co-casting of the ceramic suspension and the gelled water is carried out with a "casting bench" consisting of a stainless steel shoe (shown in Figure 1) and a flat support for performing the casting. PET (polyethylene terephthalate) plates are used as support. The shoe consists of two reservoirs (1) and (2) as well as two knives (3) and (4). The partition (5) corresponds to the front of the shoe. The partitions (6) and (7) allow the height of the knives (3) and (4) to be adjusted, respectively, and their alignment to be maintained.

[0159] The ceramic suspension and gelled water prepared in steps 1 and 2 are poured into tanks (1) and (2) respectively.

[0160] The height of the knife (3) is adjusted to 400 pm and the height of the knife (4) is adjusted to 1000 pm. The moving speed of the shoe is set to 2.40 m.min' 1 .

[0161] Moving at a constant speed of 2.40 m.min'1 , the shoe spreads the ceramic suspension on the support and the layer of gelled water on top, forming layers with a homogeneous thickness and microstructure.

[0162] The strips thus obtained are then left for 40 min in the casting bench for the phase inversion step.

[0163] The strips are then washed with distilled water.

[0164] The strips are then dried in an oven at 50°C for 10 minutes on the PET support.

[0165] The strips are then debinded at 550°C (via a temperature increase of 0.3°C / min until a temperature of 550°C is reached), pre-sintered at 1100°C for 1 hour (via a temperature increase of 5°C / min until 1100°C, then the temperature is maintained at 1100°C for 1 hour), and finally sintered at 1400°C for 2 hours.

[0166] The strips thus obtained have a microstructure with textured porosity throughout the thickness of the strip (see figure 3).

[0167] EXAMPLE 3: PHASE INVERSION IN THE CONTEXT OF HIGH-VISCOSITY SUSPENSIONS (EXTRUSION)

[0168] This example is given for illustration purposes only and does not constitute a limitation of the present invention.

[0169] The steps to follow are the same as those described in Example 1.

[0170] The consistency of the water gel is pasty in this example. Its viscosity is high.

[0171] The water gel is infiltrated into areas (1) and (3) of Figure 4 while the ceramic suspension is infiltrated into area (2) of Figure 4. Area (4) corresponds to the extruder partitions.

[0172] The tubes thus obtained, after drying (at 50°C for 10 minutes), debinding (at 550°C via a temperature increase of 0.3°C / min until reaching a temperature of 550°C), pre-sintering (at 1100°C for 1 h via a temperature increase of 5°C / min until reaching 1100°C, then maintaining the temperature at 1100°C for 1 hour) and sintering (at 1400°C for 2 h), have a microstructure with textured porosity (see Figure 5 and Figure 6).

[0173] EXAMPLE 4: PHASE INVERSION CO-CASTING USING CYRENE AS SOLVENT

[0174] This example is given for illustration purposes only and does not constitute a limitation of the present invention.

[0175] The steps to follow are the same as those described in Example 1, where N-methyl-2-pyrrolidone (NMP) was replaced by Cyrene (Sigma-Aldrich).

[0176] The microstructure of the membrane thus obtained, after drying (at 50°C), is presented in Figure 7a and compared to the microstructure obtained in Figure 7b.

[0177] As demonstrated in Figure 7a, it is possible to fabricate ceramic membranes by co-casting coupled with phase inversion using cyrene as a solvent instead of N-methyl-2-pyrrolidone (NMP).

[0178] N-methyl-2-pyrrolidone (NMP) allows to obtain a microstructure in the form of channels (see Figure 7b).

[0179] Cyrene allows to obtain a microstructure whose porosity is called "fibrous" (see Figure 7a). The solvent therefore plays a preponderant role in the optimization or adjustment of the microstructure (i.e. the porosity network). The choice of solvent depends on the choice of the polymer and the non-solvent used linked to the envisaged application.

[0180] EXAMPLE 5: PHASE INVERSION BAND CO-CASTING COMPRISING A MIXTURE OF YTTRIUM-STABILIZED ZIRCONIA (3% MOL) AND NICKEL OXIDE (NiO) [3YSZ-NIO]

[0181] This example is given for illustration purposes only and does not constitute a limitation of the present invention.

[0182] The steps to be followed are the same as those described in Example 2 where the ceramic powder comprising a mixture of yttrium-stabilized zirconia (8 mol%) and nickel oxide (NiO) was replaced by a ceramic powder comprising a mixture of yttrium-stabilized zirconia (3 mol%) (Tosoh) and nickel oxide (NiO) (Inframat advanced materials).

[0183] The strip is then debinded at 550°C (via a temperature increase of 0.3°C / min until a temperature of 550°C is reached), pre-sintered at 1100°C for 1 hour (via a temperature increase of 5°C / min until 1100°C, then the temperature is maintained at 1100°C for 1 hour), and finally sintered at 1400°C for 2 hours.

[0184] The microstructure of the ceramic strip thus obtained is presented in Figure 8.

[0185] EXAMPLE 6: WATER GELS OF ADAPTED VISCOSITY FOR CO-CASTING BY PHASE INVERSION

[0186] This example is given for illustration purposes only and does not constitute a limitation of the present invention.

[0187] Step 1: Preparing the water gels

[0188] The process of preparing gels from the gelling agents listed below:

[0189] - Tara gum

[0190] - Guar Gum

[0191] - Psyllium, is detailed below.

[0192] The gelling agent was added to water and mixed using a high shear mixer at speeds of around 7000 rpm at room temperature. After obtaining a homogeneous mixture, the gels were conditioned in a refrigerator for 24 hours before use.

[0193] For the preparation of gels containing methylcellulose as a gelling agent, the mixing was carried out at room temperature. The water was first heated to 60°C in a beaker covered with parafilm. Then, the methylcellulose was added to the hot water under magnetic stirring. Once the mixture was homogeneous, the beaker was removed from the heating plate until it returned to room temperature. The gel was also conditioned in a refrigerator for 24 hours before use.

[0194] Step 2: Rheological measurements (measurement of viscosity as a function of shear stress)

[0195] A casting speed set at 2.4 m.min' 1 and a knife height fixed at 400 pm, implies shear stresses of the order of 100 s -1 during casting.

[0196] Rheological measurements, more specifically of viscosity as a function of shear stress, were recorded on these gels thus prepared. The results obtained are presented in Figure 9.

[0197] With a shear rate of 100 s' 1 , the viscosity of the tested gels has the same order of magnitude, namely between 1.5.10' 1 Pa.s and 8.10' 1 Pa.s (see Figure 9).

[0198] These measurements show that it is possible to manufacture water gels, with a viscosity suitable for tape casting, i.e. also for co-casting, using gelling agents other than Karaya gum and in particular using Tara gum, Guar gum, Psyllium and methylcellulose as gelling agents.

[0199] EXAMPLE 7: VARIATION OF THE CONCENTRATION OF POLYVINYLPYRROLIDONE (PVP) ADDITIVE

[0200] This example is given for illustration purposes only and does not constitute a limitation of the present invention.

[0201] The process of Example 1 was reproduced varying the concentration of additive (Polyvinylpyrrolidone (PVP)) namely 0wt% PVP, 1 wt% PVP, 3wt% PVP and 5wt% PVP.

[0202] The microstructures of the ceramic strips thus obtained are presented in Figure 10.

[0203] Figure 10a, corresponding to a ceramic suspension (YSZ) without additive shaped by phase inversion, shows the growth of relatively fine microchannels, not crossing the entire thickness of the membrane. On the contrary, Figures 10b, 10c and 10d show that the presence of the PVP additive allows the formation of microchannels that can grow through the thickness of the membrane.

[0204] The presence of the PVP additive therefore has an influence on the growth and formation of the channels.

[0205] The choice of additive concentration depends on the intended application.

Claims

CLAIMS 1. Phase inversion co-casting or co-extrusion process comprising the following steps: - a shaping step by co-casting or co-extrusion of a polymer solution loaded with ceramic powder and gelled water, and - a phase inversion step, the casting or extrusion and phase inversion steps being carried out simultaneously.

2. Phase inversion co-casting method according to claim 1 characterized in that it comprises the following steps: - a shaping step by co-casting a polymer solution loaded with ceramic powder and gelled water, and - a phase inversion step, the casting and phase inversion steps being carried out simultaneously.

3. Method according to claim 1 or 2, in which the polymer solution loaded with ceramic powder comprises between 2 and 20% by mass of polymer, 25 and 55% by mass of solvent and between 0 and 10% by mass of additives, relative to the total mass of said polymer solution.

4. Method according to claim 3, in which the polymer is chosen from polyether sulfones (PES), cellulose acetate (CA), polyamides, polysulfones (PSf), polyvinylidene fluorides (PVDF), polyacrylonitriles (PAN), polytetrafluoroethylenes (PTFE), polypropylenes (PP), polyethylenes (PE), polyvinyl alcohols (PVA), polyimides, polyetheretherketones (PEEK), polydimethylsiloxanes (PDMS), polycarbonates (PC), polyvinyl chlorides (PVC), or their derivatives, and their mixtures.

5. Method according to claim 3, in which the solvent is chosen from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), triethylphosphate (TEP), dimethylsulfoxide (DMSO), cyrene and mixtures thereof.

6. Method according to any one of claims 3 to 5, in which the additive is chosen from polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polymethyl methacrylate (PMMA), lithium chloride (LiCl), or their derivatives, and their mixtures.

7. Method according to any one of claims 1 to 6, in which the gelled water comprises between 80 and 99.5% by mass of water, preferably distilled water, and between 0.5 and 20% by mass of a gelling agent.

8. Method according to claim 7, in which the gelling agent is chosen from cellulose binders, Karaya gum, Guar gum, cellulose gum such as cellulose derivatives and in particular methylcellulose, Tara gum, Tamarind gum, agar-agar, pectins, alginates, psyllium, or their derivatives, and their mixtures.

9. Method according to any one of claims 1 to 8, in which the polymer solution loaded with ceramic powder comprises between 1 and 80% by mass of ceramic powder relative to the total weight of the polymer solution loaded with ceramic powder, preferably chosen from alumina (AI2O3), zirconia stabilized with yttrium oxide, zirconia stabilized with scandium oxide, cerium oxide doped with gadolinium, cerium oxide doped with samarium oxide, lanthanum gallate doped with strontium and magnesium, rare earth silicates such as apatite phases, or their mixtures with metal oxides such as nickel oxide (NiO). 10.Use of the process as defined according to any one of claims 1 to 9 for the manufacture of membranes, preferably ceramic membranes, the manufacture of filters, preferably ceramic filters and / or the manufacture of electrochemical cells, preferably the manufacture of fuel cells and the manufacture of electrolysers.

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