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

Abstract

The present invention relates to the implementation of co-casting and / or co-extrusion processes coupled with phase inversion. More specifically, the present invention relates to a co-casting and / or co-extrusion process 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 gelled water, and - a phase inversion step, the casting or extrusion and phase inversion steps being carried out simultaneously. The present invention also relates to a strip, preferably ceramic strip or metallic ceramic strip, obtained by the process as defined above. The present invention also relates to a tube, preferably ceramic tube, obtained by the process as defined above.The present invention also relates to the use of the method as defined above for the manufacture of strips, preferably ceramic strips and / or metal ceramic strips or tubes, preferably ceramic tubes. The present invention also relates to the use of the method as defined above or the strip, preferably the ceramic strip, as defined above, or the tube, preferably the ceramic tube as defined above, 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.

Description

Title of the invention: CO-CASTING AND / OR COEXTRUSION METHOD BY PHASE INVERSION USING A WATER GEL WITH ADAPTED VISCOSITY FIELD OF THE INVENTION

[0001] The field of the invention relates to the implementation of co-casting and / or co-extrusion processes coupled with phase inversion. TECHNICAL BACKGROUND

[0002] 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"). 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.

[0003] Phase inversion processes using co-casting to prepare planar membranes or microtubes, such as ceramic membranes or ceramic microtubes, include either a tape casting step or an extrusion step.

[0004] The principle of the phase inversion tape casting process is to perform conventional tape casting and then to bring the resulting tape into contact with a non-solvent, generally water. The phase inversion takes place during a second step when the cast tape comes into contact with the non-solvent. At the interface between the solvent (contained in the cast tape) and the non-solvent, a diffusion mechanism is triggered and leads to a thermodynamically unstable system which causes phase separation and precipitation of the polymer solution in which the ceramic powder is dispersed, corresponding to the cast tape. The solvent migrates into the non-solvent bath while the non-solvent migrates into the ceramic suspension. After the phase separation of the system, the diffusion of the solvent and the non-solvent continues and the pores formed in the membrane will continue to grow in accordance with the diffusion front (=interface).It is the solidification of the polymer, linked to the interdiffusion between the solvent and the non-solvent, which fixes the final microstructure of the strip. An asymmetric microstructure is commonly observed, with a layer of pores in the form of long channels directed to the . perpendicular to the diffusion front (closest to the interface of the initial stack) and another layer with a more homogeneous porosity (called the spongy porosity layer). In other words, the phase inversion strip casting process consists of casting a polymer solution loaded with ceramic powder, transferring it into a non-solvent bath (usually water), and finally cutting the solidified strips to produce the final object.

[0005] The principle of the phase inversion extrusion process is based on the same foundation as that of phase inversion strip casting. In fact, it involves carrying out an extrusion and then placing the resulting extrudate in contact with a non-solvent, generally water. The mechanisms taking place during the phase inversion process are identical to those described previously with the phase inversion strip casting process.

[0006] Current processes do not allow the shaping of ceramic suspensions and the phase inversion mechanism to be carried out simultaneously. The various stages of current processes, described below, require the handling of the extrusion strips or profiles, which will have the effect of generating stresses in the environment, which are detrimental to the subsequent production of the final part.

[0007] Current methods include the following steps: - step 1: Casting the ceramic suspension or extrusion of the ceramic paste, - step 2: Transfer of the strip (or micro tube) into a basin of non-solvent polymer solution loaded with cast (or extruded) ceramic powder, - step 3: Phase inversion step in the non-solvent bath

[0008] Indeed, at present, 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 diffuses into the non-solvent basin, thus contaminating the non-solvent in the basin, during the phase inversion step.

[0009] The present invention aims to remedy all or part of the drawbacks of the state of the art cited above.

[0010] Surprisingly and unexpectedly, the present inventors have developed a phase inversion co-casting (or co-extrusion) process in which only one step is necessary, while avoiding the use of a non-solvent pool. In particular, the present inventors have developed a phase inversion co-casting or co-extrusion process in which a polymer solution loaded with ceramic powder is cast or extruded simultaneously with a gelled water layer (by co-casting or by co-extrusion) to achieve phase inversion in a single step. Summary of the invention

[0011] A first object of the present invention relates to a co-casting and / or co-extrusion process by phase inversion comprising the following steps: - 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.

[0012] The present invention also relates to a strip, preferably a ceramic strip or a metallic ceramic strip, obtained by the method as defined above.

[0013] The present invention also relates to a tube, preferably a ceramic tube, obtained by the method as defined above.

[0014] 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.

[0015] 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, 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

[0016] A first object of the present invention relates to a co-casting and / or co-extrusion process by phase inversion comprising the following steps: - 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.

[0017] Advantageously, the present invention relates to a co-casting and / or co-extrusion process by phase inversion based on an exchange between precursors (liquid and pasty in this context), at the interface between two media of different compositions, when they are brought into contact.

[0018] 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.

[0019] Advantageously, a first object of the invention consists in simultaneously carrying out the shaping of ceramic suspensions (of variable viscosity) and the chemical process of phase inversion, by co-casting and / or co-extruding two suspensions of adapted and variable viscosity depending on the geometry and the intended application. Advantageously, this process of co-casting and / or co-extrusion by phase inversion makes it possible to carry out the following steps and reactions in a single step: - 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 between the solvent, in which the ceramic powder is suspended (in a polymer-rich medium), and the 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 water gel (non-solvent).

[0020] 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.

[0021] By "ceramic powder-filled polymer solution" or "ceramic suspension" is preferably meant a heterogeneous mixture in which ceramic powder particles are dispersed. In the present invention, the ceramic powder is dispersed in the polymer solution.

[0022] By "co-casting" is preferably meant processes for shaping ceramic suspensions such as tape casting. Preferably, casting is used for low-viscosity ceramic suspensions. The term "co" preferably denotes the simultaneous casting of different layers.

[0023] By "co-extrusion" is preferably meant processes for shaping ceramic suspensions such as micro-extrusion. Preferably, extrusion is used for high-viscosity ceramic suspensions. The term "co" preferably denotes the simultaneous extrusion of different layers.

[0024] Advantageously, the process of the present invention is characterized by the use of gelled water (or water with a gelling agent added) 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.

[0025] In the method of the present invention, the casting or extrusion and phase inversion steps are carried out simultaneously. Advantageously, the phase inversion mechanism begins as soon as the polymer solution loaded with ceramic powder (also called ceramic suspension) and the water gelled water (also called pseudo-gel) come into contact. In the present invention, the polymer solution loaded with ceramic powder (also called ceramic suspension) and the gelled water are cast or extruded simultaneously, and brought into contact during the casting or extrusion step, which triggers the phase inversion.

[0026] The co-casting step can be automated.

[0027] The co-extrusion step can be automated.

[0028] 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.

[0029] Advantageously, the present invention makes it possible to carry out the extrusion, preferably the extrusion of the ceramic suspension and the phase inversion, in just one step, and to manufacture tubes with a microstructure whose porosity is textured and / or oriented.

[0030] 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.

[0031] By "oriented porosity" is preferably meant a porosity, generally highly anisotropic, which is oriented in a preferred direction in space, in the case of the invention, perpendicular to the casting or extrusion plane.

[0032] Reducing the number of steps makes it possible to better control the phase inversion, and therefore to improve the efficiency of the process, its reproducibility, its repeatability and to limit the constraints which can be generated in the object obtained by the process of the invention.

[0033] In particular, the replacement of the manual step of transferring / transporting the strips in a non-solvent bath by 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.

[0034] In addition, the absence of a non-solvent bath makes it possible to reduce the consumption of non-solvent necessary for the operation of conventional processes and to limit the quantity of chemical waste. Advantageously, the use of gelled water in the process of the present invention makes it possible to use a relatively small quantity of water, thus generating a lower proportion of chemical waste.

[0035] Advantageously, the method of the present invention is simple and practical to implement.

[0036] Advantageously, the method of the present invention can be transposed to an industrial scale, automated and / or implemented continuously, thus facilitating industrialization.

[0037] 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.

[0038] Examples of polymers include, but are not limited to, 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 mixtures thereof.

[0039] Examples of solvents include, but are not limited to, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyllacetamide (DMAc), triethylphosphate (TEP), dimethylsulfoxide (DMSO), and mixtures thereof.

[0040] 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.

[0041] Advantageously, the gelling agent makes it possible to increase the viscosity of the water.

[0042] The water is preferably distilled water.

[0043] 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.

[0044] Depending on the percentage of gelling agent, the viscosity of the gelled water can be adjusted and adapted to the co-casting and / or co-extrusion process.

[0045] Advantageously, the gelled water has rheological properties suitable for co-casting and / or co-extrusion processes, which are adjusted with the addition of the gelling agent.

[0046] Preferably, when step (1) is a co-extrusion shaping step, the viscosity of the gelled water as defined above is between 1 and 20 Pa.s*, preferably between 1 and 3 Pa.s*.

[0047] Preferably, when step (1) is a co-casting shaping step, the viscosity of gelled water as defined above is between 0.5 and 20 Pa.s, preferably between 1 and 3 Pa.s

[0048] Preferably, the gelled water as defined above comprises between 80 and 99.5% 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 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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).

[0053] 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.

[0054] Examples of ceramic powder include, but are not limited to, alumina (A12O3), yttria-stabilized zirconia (YSZ), 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).

[0055] Advantageously, the ceramic suspension comprising the constituents such as previously defined and in the proportions as previously defined makes it possible to obtain a strip or an extrusion profile whose microstructure presents a textured and / or oriented porosity throughout the thickness of the object.

[0056] 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.

[0057] Preferably, the ceramic suspension as defined above is prepared by adding a ceramic powder as defined above to the polymer solution as defined above.

[0058] The ceramic suspension as defined above can be prepared using any device allowing the different constituents of said ceramic suspension to be mixed.

[0059] 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.

[0060] 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 100 and 15 hours, preferably for approximately 12 hours with a rotation speed of between 100 rpm and 160 rpm, preferably approximately 130 rpm.

[0061] 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).

[0062] By "casting bench" is preferably meant a device consisting of a shoe, preferably made of stainless steel, and a flat support for carrying out the casting. PET (polyethylene terephthalate) 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 well as the speed of movement of the shoe which allows to control the thickness of the cast layers. Advantageously, by moving at 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.

[0063] By "extruder" we preferably mean a system allowing a liquid or a paste, under the action of pressure, to flow into a nozzle or die whose geometry allows the desired object to be shaped, in our case a cylinder, a tube or a micro-tube.

[0064] By "phase inversion step" is preferably meant a step during which the diffusion mechanism between the solvent and the non-solvent takes place, 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.

[0065] 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.

[0066] Advantageously, during the phase inversion step, the strips are left in the casting bench.

[0067] 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.

[0068] 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.

[0069] Another object of the present invention relates to a tube, preferably a ceramic tube, obtained by the method as defined above.

[0070] 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.

[0071] Advantageously, the strips, preferably the ceramic strips thus obtained, have a textured porosity and / or porosity oriented in a spatial direction.

[0072] Advantageously, the tubes, preferably the ceramic tubes thus obtained, have a textured porosity and / or porosity oriented in a spatial direction.

[0073] 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 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 and more preferably the manufacture of solid oxide electrochemical cells such as solid oxide fuel cells and the manufacture of solid oxide electrolysers.

[0074] Examples of fuel cells include, but are not limited to, solid oxide fuel cell (SOFC) cells.

[0075] Examples of electrolyzers include, but are not limited to, high temperature electrolyzers (Solide Oxide Electrolysis Cell - SOEC).

[0076] The membranes, preferably ceramic membranes (preferably made of zirconia, or yttria-containing zirconia, or alumina A12O3), 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 or reprocessing processes for fumes or fluids such as water).

[0077] The filters, preferably ceramic filters, thus manufactured can be used in the field of metallurgy, for example to remove slag or impurities during casting.

[0078] The membranes and electrochemical cells, such as fuel cells and electrolysers, thus manufactured can be used in the energy field, for example for the manufacture of solid oxide fuel cell (SOFC) cells, high temperature electrolysers (HTE) but also oxygen-separating ceramic membranes. DESCRIPTION OF FIGURES

[0079] [Fig.l] Plan in sectional view of the shoe allowing the co-casting of example 1 and example 2.

[0080] [Fig.2] Micrograph of a ceramic strip obtained by the phase inversion co-casting process of Example 1.

[0081] [Fig.3] Micrograph of a ceramic strip obtained by the phase inversion co-casting process of Example 2.

[0082] [Fig.4] Plan in sectional view of the co-extrusion principle of example 3.

[0083] [Fig.5] Micrograph of a ceramic micro-tube obtained by the phase inversion coextrusion process of Example 3.

[0084] [Fig.6] Micrograph of the microstructure of a ceramic micro-tube obtained by the phase inversion co-extrusion process of Example 3.

[0085] EXAMPLE 1: PHASE INVERSION IN THE FRAMEWORK OF LOW-VISCOSITY SUSPENSIONS (BAND CASTING OF YTTRIATED ZIRCONIA POWDER)

[0086] This example is given for illustration purposes only and does not constitute in any way case a limitation of the present invention.

[0087] This example targets applications such as water filtration. Step 1: Preparation of the gelled water

[0088] 5% by mass of Karaya gum (Sigma-Aldrich) is added to distilled water (95% by mass of distilled water) with 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. Step 2: Preparation of the ceramic suspension

[0089] 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 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.

[0090] 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.

[0091] The mass quantities of each compound are presented in the table below. Density % by weight (relative to the total weight of said polymer solution) Ceramic powder Yttrium-stabilized zirconia (8%mol) ZrO2 - 8%mol Y2O3 5.76 48.67% Solvent N-methyl-2-pyrrolidone 1.03 42.63% Additive Polyvinylpyrrolidone 1.2 0.97% Polymer Polyethersulfone 1.37 7.73%

[0092] Table 1: Example of a formulation for preparing a ceramic suspension with yttrium-stabilized zirconia powder (8% mol) Step 3: Co-casting: strip casting

[0093] 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 [Fig.l]) and a flat support for carrying out the casting. PET (polyethylene terephthalate) plates are used as support. The shoe consists of two tanks (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.

[0094] The ceramic suspension and the gelled water prepared in steps 1 and 2 are poured respectively into the tanks (1) and (2).

[0095] The height of the knife (3) is adjusted to 400 pm and the height of the knife (4) is adjusted to 800 pm. The speed of movement of the shoe is set to 2.40 m.min '.

[0096] By moving at a constant speed of 2.40 m.min ', 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.

[0097] The strips thus obtained are then left for 20 min in the casting bench for the phase inversion step.

[0098] The strips are then washed with distilled water.

[0099] The strips are then dried in an oven at 50°C for 10 min on paper Mylar

[0100] (silicone paper).

[0101] The strips thus obtained have a microstructure with textured porosity throughout the thickness of the strip (see [Fig.2]).

[0102] EXAMPLE 2: PHASE INVERSION IN THE FRAMEWORK OF LOW-VISCOSITY SUSPENSIONS (BAND CASTING OF A [NiO-YSZ] CERMET)

[0103] This example is given for illustration purposes only and does not constitute a limitation of the present invention in any way.

[0104] This example targets applications such as SOFC and / or SOEC electrochemical cells. Step 1: Preparation of the gelled water

[0105] 5% by mass of Karaya gum (Sigma-Aldrich) is added to distilled water (95% by mass of distilled water) with 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. Step 2: Preparation of the ceramic suspension

[0106] 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 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.

[0107] In the planetary mill, 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 12h at 130 rpm to obtain the ceramic suspension.

[0108] The mass quantities of each compound are presented in the table below. Density % by weight (relative to the total weight of said polymer solution) Ceramic powder Yttrium-stabilized zirconia (8%mol) ZrO2 - 8%mol Y2O3 5.76 29.7 Metal powder Nickel oxide NiO 6.78 29.7 Solvent N-methyl-2-pyrrolidone 1.03 34.4% Additive Polyvinylpyrrolidone 1.2 1.2% Polymer Polyethersulfone 1.37 5.1%

[0109] Table 2: Example of a formulation for preparing a ceramic suspension with yttrium-stabilized zirconia powder (8 mol%) and nickel oxide powder Step 3: Co-casting: strip casting

[0110] 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 [Fig.l]) and a flat support for carrying out 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.

[0111] The ceramic suspension and the gelled water prepared in steps 1 and 2 are poured respectively into the tanks (1) and (2).

[0112] The height of the knife (3) is adjusted to 400 pm and the height of the knife (4) is adjusted to 1000 pm. The speed of movement of the shoe is set to 2.40 m.min '.

[0113] By moving at a constant speed of 2.40 m.min ', 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.

[0114] The strips thus obtained are then left for 40 min in the bench of casting for the phase inversion step.

[0115] The strips are then washed with distilled water.

[0116] The strips are then dried in an oven at 50°C for 10 min on the support in PET.

[0117] The strips thus obtained have a microstructure with textured porosity throughout the thickness of the strip (see [Fig.3]).

[0118] EXAMPLE 3: PHASE INVERSION IN THE CONTEXT OF HIGH-VISCOSITY SUSPENSIONS (EXTRUSION)

[0119] This example is given for illustration purposes only and does not constitute a limitation of the present invention in any way.

[0120] The steps to follow are the same as those described in Example 1.

[0121] The consistency of the water gel is pasty in this example. Its viscosity is high.

[0122] The water gel is infiltrated into areas (1) and (3) of [Fig.4] while the suspension ceramic is infiltrated into area (2) of [Fig.4]. Area (4) corresponds to the extruder partitions.

[0123] The tubes thus obtained have a micro structure with textured porosity (see [Fig.5] and [Fig.6]).

Claims

Claims

1. A method of 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 gelled water, and - a phase inversion step, the casting or extrusion and phase inversion steps being carried out simultaneously.

2. A method of co-casting by phase inversion comprising the following steps: - a step of shaping 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. The method of claim 3, wherein the polymer is selected 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 mixtures thereof.

5. A method according to claim 3 or 4, wherein the solvent is selected from N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyllacetamide (DMAc), triethylphosphate (TEP), dimethyl sulfoxide (DMSO) and mixtures thereof.

6. A method according to any one of claims 3 to 5, wherein the additive is selected from polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polymethyl methacrylate (PMMA), lithium chloride (LiCl), or their derivatives, and mixtures thereof.

7. A method according to any one of claims 1 to 6, wherein 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. A method according to claim 7, wherein the gelling agent is selected from cellulose binders, Karaya gum, Guar gum, cellulose gum, Tara gum, Tamarind gum, agar-agar, pectins, alginates, or their derivatives, and mixtures thereof.

9. A method according to any one of claims 1 to 8, wherein 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 (A12O3), yttria-stabilized zirconia, scandia-stabilized zirconia, gadolinium-doped cerium oxide, samarium-doped cerium oxide, strontium- and magnesium-doped lanthanum gallate, rare earth silicates such as apatite phases, or mixtures thereof with metal oxides such as nickel oxide (NiO).

10. Use of the method 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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