Method for producing an inorganic filtration medium by means of an intermeshing and retained membrane

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a porous monolithic inorganic support, which can in particular be used to obtain a filtration membrane, and in particular a tangential filtration membrane. More specifically, the porous support is prepared by a technique proceeding by addition of material. Prior art

[0002] The filtration membrane constitutes a selective barrier and allows, under the action of a transfer force, the passage or the stopping of certain components of the liquid medium to be treated. The passage or the stopping of the components can result from their size in relation to the size of the pores of the membrane which then behaves like a filter. Depending on the size of the pores, these techniques are called microfiltration, ultrafiltration or nanofiltration.

[0003] A membrane consists of a porous support on which one or more separating layers are deposited. Conventionally, the support is first shaped by extrusion. The support then undergoes sintering to obtain the required strength, while maintaining an open and interconnected porous texture. This process requires the production of rectilinear channels inside which the separating layer(s) are then deposited and sintered. The membrane thus produced therefore undergoes at least two sintering operations. The organic binders added during the preparation of the paste, before its extrusion, burn completely during the sintering of the support.

[0004] The Applicant described in application FR 3 006 606 the preparation of a filtration membrane whose porous support is produced by an additive technique, by repeated deposition of a continuous bed of powder followed by localized consolidation according to a predetermined pattern. This technique makes it possible to prepare filtration membranes that are mechanically resistant and suitable for use in tangential filtration. However, this technique has the disadvantage of requiring adjustment of the fluidity of the powder to allow it to flow perfectly during deposition of the powder bed. In addition, this technique requires removal of the unconsolidated powder, possibly also for recycling, which can be tricky, long and expensive, particularly when said unconsolidated powder is present in non-rectilinear channels of the porous support.

[0005] The applicant has also proposed by patent applications WO2020 / 109715 and WO2020 / 109716, the latter disclosing a method for manufacturing at least one porous monolithic inorganic support according to the preamble of claim 1, new methods for preparing a porous support which do not have the drawbacks of the prior art, and in particular which are rapid, easy to implement, which make it possible to obtain a mechanically resistant porous support and whose shape, and in particular that of the non-rectilinear channels, is easily varied. The porous support obtained is homogeneous, mechanically resistant and has a porosity suitable for use in filtration, i.e. a porosity of between 10 and 60% and which is open and interconnected with an average pore diameter ranging from 0.5 µm to 50 µm.

[0006] To achieve this, the processes use a 3D printing machine comprising an extrusion head mounted so as to move in space relative to and above a fixed horizontal plate. An inorganic composition emerges from the extrusion head in the form of a ribbon of material or cord making it possible to build, from a digital 3D model, a raw, manipulable three-dimensional structure intended to form the monolithic porous inorganic support(s). The raw, manipulable three-dimensional structure is then subjected to a sintering step.

[0007] As explained in these patent applications, the manipulable raw three-dimensional structure is obtained from the superposition of layers, each corresponding to a set of continuous or discontinuous cords, juxtaposed or not juxtaposed, which are extruded at the same altitude following the digital 3D model. The different layers can be stacked along the vertical axis in different ways.

[0008] In the state of the art, it is also known from patent application WO 2020 / 109716, a method for manufacturing a 3D object by means of modeling, by depositing a molten wire in which an overlapping path is made. Similarly, patent application US 2017 / 165917 describes a method for manufacturing a 3D object by means of modeling, implementing two controlled material deposition nozzles to create in particular a crossing between the two beads of material.

[0009] The applicant thus considered producing the layers by vertical stacks of deposits of contiguous cords of material c as illustrated in the figure 1A . The applicant noted that after the sintering operation ( figure 1B ), such a structure contained voids of material v which were capable of having a size greater than that of the pores, and which were capable of reducing the mechanical resistance of the porous support.

[0010] The applicant also considered producing the layers by depositing cords of material c arranged in a staggered pattern as illustrated in figure 1C . This solution does nothing to eliminate the residual empty spaces v between the material beads. After the sintering operation ( figure 1D ), the structure still has internal voids of material v. In addition, this solution deteriorates the quality of the lateral surfaces since one in two layers has a gap leading to the collapse of the material deposit of the upper layer. Statement of the invention

[0011] The object of the invention is precisely to remedy the drawbacks of the state of the art, by proposing a new method for manufacturing a porous monolithic inorganic support, designed to avoid creating empty spaces of material likely to reduce the mechanical resistance of the porous support.

[0012] Another object of the invention is to propose a method for manufacturing a three-dimensional structure, designed to be able to control the dimensions of this three-dimensional structure and in particular the profile of the walls of this three-dimensional structure.

[0013] Another object of the invention is to propose a method for manufacturing a three-dimensional structure provided with at least one circulation channel for a fluid medium to be treated, having a wall suitable for the deposition of separation layers.

[0014] Another object of the invention is to propose a method for manufacturing a three-dimensional structure provided with at least one channel for the circulation of a fluid medium to be treated, having a wall presenting an uninterrupted succession of rounded reliefs generating variations in the passage section of the channel, while avoiding the appearance of prohibitive pressure losses.

[0015] To achieve these objectives, the invention relates to a method for manufacturing at least one porous monolithic inorganic support having at least one channel for the circulation of the fluid to be treated and having a porosity of between 10% and 60% and an average pore diameter belonging to the range from 0.5 µm to 50 µm, using a 3D printing machine comprising at least one extrusion head mounted movably in space above a fixed horizontal plate, being moved successively with a nominal height along a predefined digital trajectory to carry out superimposed material deposits each having a nominal width and a thickness defined between a lower surface and an upper surface, said 3D printing machine allowing the deposition of material in the form of a bead with rounded edges so as to create rounded perimeter reliefs on the wall of at least one circulation channel, participating in the generation of turbulence, of a composition for building, on said horizontal plate, from the predefined digital trajectory, walls of a manipulable raw three-dimensional structure intended to form the monolithic porous inorganic support(s), the method consisting of: For a wall whose width is greater than the nominal width of the material deposit, breaking down the digital trajectory exclusively into paths with overlap and into paths with crossing; Feeding the extrusion head of the 3D printing machine with a composition, Controlling the extrusion head according to the digital trajectory so that: * for a path with overlap, the material being deposited partially overlaps at least one edge of a previously deposited material deposit,by a portion of overlapping material presented in its thickness and having a thickness strictly less than the nominal height so as to avoid in the internal part of the raw three-dimensional structure that can be manipulated, spaces between the rounded edges of the deposit of material in progress and those of the deposit of material previously deposited, * for a path with crossing, the material being deposited crosses at least one deposit of material previously deposited with a complete overlap of said deposit of material previously deposited, by a portion of overlapping material presented in its thickness and having a thickness strictly less than the nominal height so as to avoid in the internal part of the raw three-dimensional structure that can be manipulated, spaces between the rounded edges of the deposit of material in progress and those of the deposit of material previously deposited.

[0016] According to an advantageous embodiment characteristic, the extrusion head is mounted to move along the predefined digital trajectory to perform a succession of turns, each corresponding to the path traveled to find the same position in the horizontal plane with an elevation corresponding to a nominal height.

[0017] According to another advantageous embodiment characteristic, the extrusion head is controlled so that over at least one revolution, the extrusion head rises at least once by an intermediate height which is a fraction of the nominal height.

[0018] According to another characteristic of the invention, the extrusion head is controlled so that over at least one revolution, the extrusion head is positioned at different points along the path, rising at each point by a height increment, the sum of which corresponds to the nominal height.

[0019] Advantageously, the extrusion head is controlled so that through a succession of turns, the extrusion head rises to build the raw manipulable three-dimensional structure conforming to the digital 3D model, following a trajectory with uninterrupted material deposition from the beginning to the end of the construction of the raw manipulable three-dimensional structure.

[0020] According to an advantageous characteristic, the extrusion head is controlled so that during each revolution, the extrusion head is offset in the horizontal plane so that the material being deposited partially overlaps an edge of a previously deposited material deposit.

[0021] For a path with crossing, the extrusion head is controlled to reduce the quantity of material deposited to produce the overlapping part of material having a thickness strictly less than the nominal height.

[0022] For a path with the same overlap, the extrusion head is controlled to keep the flow rate of deposited material constant.

[0023] For an overlapping path, the extrusion head is controlled to adjust its position in the plane to define the degree of overlap of the overlapping material portion on the previously deposited material deposit.

[0024] For an overlapping path, the flow rate of the extrusion head is adjusted according to the degree of overlap of the overlapping part of the material on the previously deposited material.

[0025] Typically, the extrusion head is mounted to move along the predefined digital trajectory to carry out material deposits in superposition by layers each rising by a nominal height.

[0026] According to another characteristic of the invention, the extrusion head is controlled in order to provide in the manipulable raw three-dimensional structure, at least one circulation channel for a fluid medium to be treated, having a wall presenting a succession of rounded reliefs generating variations in the passage section of the channel, these rounded reliefs being formed by the part of material located opposite the overlapping part of material.

[0027] According to another feature, the extrusion parameters are adjusted and the extrusion head is configured so that the material portion located opposite the overlapping material portion has a rounded edge.

[0028] Conventionally, the raw, manipulable three-dimensional structure is placed in a heat treatment furnace in order to carry out a sintering operation.

[0029] Another object of the invention is to propose a method for preparing a tangential filtration membrane comprising the manufacture of a porous monolithic inorganic support in which at least one channel for circulation of the fluid medium to be treated is provided, followed, after sintering of said support, by a step of creating at least one separating layer on the walls of the channel(s).

[0030] Another object of the invention is to provide a porous monolithic inorganic support manufactured according to the method according to the invention and having an external surface presenting a succession of rounded perimeter reliefs and a circulation channel whose wall presents rounded perimeter reliefs participating in the generation of turbulence.

[0031] Another object of the invention is to propose a tangential filtration membrane comprising a porous monolithic inorganic support provided with at least one channel for circulation of the fluid medium to be treated, the wall of which with rounded perimeter reliefs is coated with at least one separating layer. Brief description of the drawings

[0032] [ Fig. 1A ] There figure 1A is a sectional view of a wall made by the vertical stacking of deposits of cords of material revealing empty spaces. Fig. 1B ] There figure 1B is a view of the wall illustrated in the figure 1A showing the persistence of empty spaces. Fig. 1C ] There figure 1C is a sectional view of a wall made by the vertical stacking in staggered rows of deposits of cords of material revealing empty spaces. Fig. 1D ] There figure 1D is a view of the wall illustrated in the figure 1C after the sintering operation and showing the persistence of empty spaces. Fig. 2A ] There figure 2A is a schematic view of a 3D printing machine enabling the implementation of the invention. Fig. 2B ] There figure 2B is a perspective view of an example of the realization of a manipulable three-dimensional raw structure. Fig. 3 ] There figure 3 is a schematic top view showing the deposition of material in conventional mode to produce a tubular wall of width equal to the nominal width of a material deposition. Fig. 3A ] There figure 3A is a sectional view taken substantially along lines AA of the figure 3 showing the successive material deposits in conventional mode to produce a tubular wall. Fig. 4 ] There figure 4 is a schematic top view showing the deposition of material in vase mode to produce a tubular wall of width equal to the nominal width of a material deposition. Fig. 4A ] There figure 4A is a sectional view taken substantially along lines AA of the figure 4 showing the successive deposits of material in vase mode to create a tubular wall. Fig. 5 ] There figure 5 is a schematic top view showing the principle according to the invention of material deposits for a path with overlapping of the extrusion head. Fig. 5A ] There figure 5A is a sectional view taken substantially along lines AA of the figure 5 showing the overlap of material deposits for a path with extrusion head overlap. [ Fig. 6 ] There figure 6 is a schematic top view showing material deposits for a path with extrusion head crossing. Fig. 6A ] There figure 6A is a sectional view taken substantially along lines AA of the figure 6 showing the overlap in accordance with the invention, of the material deposits for a path with crossing of the extrusion head. [ Fig. 6B ] There figure 6B is a sectional view taken substantially along lines BB of the figure 6 showing the overlap in accordance with the invention, of the material deposits for a path with crossing of the extrusion head. [ Fig. 7 ] There figure 7 is a schematic top view showing a step of the principle of material deposition in sequential vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 7A ] There figure 7A is a sectional view taken substantially along lines AA of the figure 7 showing a step of the principle of material deposition in sequential vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 7B ] There figure 7B is a schematic top view showing the path of the material deposition in sequential vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 8 ] There figure 8 is a schematic top view showing another step of the principle of material deposition in sequential vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 8A ] There figure 8A is a sectional view taken substantially along lines AA of the figure 8 showing another step of the principle of material deposition in sequential vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 8B ] There figure 8B is a schematic top view showing the path of the material deposition in sequential vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 8C ] There figure 8C is a view showing another step of the principle of material deposition in sequential vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 9 ] There figure 9 is a schematic top view showing a step in the principle of continuous vessel material deposition to produce a tubular wall with a width greater than the nominal width of a material deposition. Fig. 9A ] There figure 9A is a sectional view taken substantially along lines AA of the figure 9 showing a step of the principle of material deposition in continuous vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 9B ] There figure 9B is a schematic top view showing the path of the material deposition in continuous vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 10 ] There figure 10 is a schematic top view showing another step of the principle of material deposition in continuous vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 10A ] There figure 10A is a sectional view taken substantially along lines AA of the figure 10 showing another step of the principle of material deposition in continuous vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 10B ] There figure 10B is a schematic top view showing the path of the material deposition in continuous vase mode to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 10C ] There figure 10C is a view showing another step of the principle of continuous vase material deposition to produce a tubular wall of width greater than the nominal width of a material deposition. Fig. 11 ] There figure 11 is a diagram illustrating an example of an extrusion head path for the process called "sequential vase mode" and for the process called "continuous vase mode". [ Fig. 12A ] There figure 12A is a top view showing another example of the embodiment of a wall delimiting two contiguous channels and having a width greater than twice the nominal width of a material deposit. Fig. 12B ] There figure 12B is a sectional view taken substantially along lines BB of the figure 12A . [ Fig. 13A ] There figure 13A is a sectional view showing the deposition of material carried out according to a prior art method, for a path with a crossing, before crossing the crossing. Fig. 13B ] There figure 13B is a sectional view showing the deposition of material produced according to a prior art method, for a path with a crossing, when crossing the crossing. Fig. 13C ] There figure 13C is a sectional view showing the deposition of material carried out according to a method of the prior art, for a path with a crossing, after crossing the crossing. Fig. 13D ] There figure 13D is a sectional view showing the deposition of material made according to a method of the prior art, for a path with a crossing, and superimposing the deposition of material previously made. Fig. 13E ] There figure 13E is a sectional view showing the deposition of material made according to a method of the prior art, for a path with a crossing, superimposing the deposition of material previously made and showing the creation of empty spaces at the intersection of the depositions of material. Fig. 14 ] There figure 14 is a sectional view showing an example of an embodiment according to the invention with deposits of material made in superposition by layers in accordance with the principle of the invention. Fig. 15 ] There figure 15 is an oblique cross-sectional image of an eight-channel porous monolithic inorganic filtration medium showing the absence of void spaces. Fig. 16 ] There figure 16 is a cross-sectional image of a tangential filtration membrane comprising a porous monolithic inorganic support with eight channels, the wall of the channels with rounded perimeter reliefs of which is coated with a separating layer. Description of the embodiments

[0033] The subject of the invention relates to the manufacture of a porous monolithic inorganic support 1 ( figure 2B ) intended to constitute a tangential flow separation element of a liquid medium to be treated into a filtrate (or permeate) and a retentate, commonly called a tangential filtration membrane.

[0034] In many applications, such porous media have a tubular geometry and comprise at least one channel or circulation path for the fluid to be filtered, provided with at least one separating layer. These circulation channels have an inlet and an outlet. In general, the inlet of the circulation channels is positioned at one end of the porous media, this end acting as an inlet zone for the fluid medium to be treated and their outlet is positioned at another end of the porous media acting as an outlet zone for the retentate. The inlet zone and the outlet zone are connected by a continuous peripheral zone at which the permeate is recovered.

[0035] In other applications, the porous supports may be in the form of a block, for example a parallelepiped in shape, in which at least one channel or circulation path for the fluid to be filtered is arranged, provided with at least one separating layer. The permeate is recovered at the periphery of the block or using a collection circuit arranged in the block. In the examples illustrated, the porous support has a tubular geometry, but it is clear that the subject of the invention can be applied to porous supports of all shapes.

[0036] When the porosity (the average pore diameter) of the sintered support is adapted to the fluid medium to be treated (filtration threshold), said sintered support can be used directly in filtration and is designated as self-membrane or homogeneous membrane.

[0037] When the porosity of the sintered support is not adapted to the fluid medium to be treated (pores too large compared to the necessary filtration threshold), the walls of the circulation channel(s) are then continuously covered by at least one separating layer which ensures the filtration of the fluid medium to be treated. The separating layer(s) are porous and have an average pore diameter smaller than that of the support. The separating layer can either be deposited directly on the porous support (case of a single-layer separating layer), or on an intermediate layer of smaller average pore diameter, itself deposited directly on the porous support (case of a multi-layer separating layer). Thus, a portion of the fluid medium to be filtered passes through the separating layer(s) and the porous support, so that this treated portion of the fluid, called permeate, flows through the outer peripheral surface of the porous support.The separating layers delimit the surface of the filtration membrane intended to be in contact with the fluid to be treated and in contact with which the fluid to be treated circulates.

[0038] The porosity of the monolithic inorganic support 1 is open, that is, it forms a network of pores interconnected in three dimensions, which allows the fluid filtered by the separating layer(s) to pass through the porous support and be recovered at the periphery. The permeate is therefore recovered on the peripheral surface of the porous support.

[0039] The porous monolithic inorganic support 1 has an average pore diameter in the range of 0.5 µm to 50 µm. The porosity of the porous monolithic inorganic support 1 is between 10 and 60%, preferably between 20 and 50%.

[0040] The average pore diameter is the value d50 of a volume distribution for which 50% of the total pore volume corresponds to the volume of pores with a diameter smaller than this d50. The volume distribution is the curve (analytical function) representing the frequencies of the pore volumes as a function of their diameter. The d50 corresponds to the median separating the area under the frequency curve obtained by mercury penetration into two equal parts. In particular, the technique described in ISO 15901-1:2005 can be used for the mercury penetration measurement technique.

[0041] The porosity of the support, which corresponds to the total volume of interconnected voids (pores) present in the material considered, is a physical quantity between 0 and 1 or between 0% and 100%. It conditions the flow and retention capacities of said porous body. For the material to be used in filtration, the total interconnected open porosity must be at least 10% for a satisfactory flow of filtrate through the support, and at most 60% to guarantee suitable mechanical resistance of the porous support.

[0042] The porosity of a porous body can be measured by determining the volume of a liquid contained in said porous body by weighing said material before and after a prolonged stay in said liquid (water or other solvent). Knowing the respective densities of the material considered and the liquid used, the mass difference, converted into volume, is directly representative of the volume of the pores and therefore of the total open porosity of the porous body.

[0043] Other techniques allow the total open porosity of a porous body to be measured precisely, including: mercury intrusion porosimetry (ISO 15901-1 standard cited above): injected under pressure, the mercury fills the pores accessible at the pressures used, and the volume of mercury injected then corresponds to the volume of the pores, small angle scattering: this technique, which uses either neutron radiation or X-rays, gives access to physical quantities averaged over the entire sample. The measurement consists of the analysis of the angular distribution of the intensity scattered by the sample, the analysis of 2D images obtained by microscopy, the analysis of 3D images obtained by X-ray tomography.

[0044] In addition, the porous monolithic inorganic support 1 has a mechanical strength suitable for use in tangential filtration. More specifically, the porous monolithic inorganic support 1 withstands an internal pressure of at least 10 bars without bursting, and preferably at least 30 bars without bursting and advantageously at least 50 bars without bursting. A burst pressure corresponds, according to the invention, to the pressure at which a support whose porosity has been previously obstructed (with a thermo-fusible material such as paraffin) bursts under the effect of an internal overpressure relative to the pressure external to the support, this overpressure being applied in the channels with water, the pressure external to the support being atmospheric pressure.

[0045] As more precisely shown in the figure 2A , the porous monolithic inorganic support 1 according to the invention is prepared by sintering a manipulable raw three-dimensional structure 2, which is constructed in accordance with a digital 3D model M by superimposing material deposits 3 relating to a composition 4 in the general sense. Material deposits are produced using a three-dimensional printing machine comprising in particular a horizontal plate 5, possibly removable, above which at least one extrusion head 6 is arranged.

[0046] By “raw three-dimensional structure” 2 is meant a three-dimensional structure obtained from the superposition of deposits of a composition 4 and not yet having undergone sintering. The shape and dimensions of this raw structure are determined level by level, by the digital 3D model M, as will be explained in detail in the remainder of the description. The digital 3D model M is determined by computer design software, in order to construct the raw three-dimensional structure 2.

[0047] This raw three-dimensional structure 2 is described as “manipulable” because it does not deform under its own weight, and can even have slopes, thanks to accelerated consolidation which gives it stable mechanical rigidity over time, as will be explained later. This raw three-dimensional structure 2 can thus be detached from the horizontal plate 5 to be moved without deformation or breakage, in particular to subsequently undergo a heat treatment operation necessary to obtain a monolithic porous support in accordance with the invention.

[0048] The extrusion head 6 of the three-dimensional printing machine is supported by a displacement mechanism (not shown in the figures), such as a robot, allowing its displacement along at least three axes (x, y and z). Thus, the extrusion head 6 can be moved along a horizontal plane (x and y axes) and vertically (z axis), thanks to the displacement mechanism which is controlled by a computer R of any type known per se. This computer R controls the movements of the displacement system and consequently of the extrusion head 6, along a predetermined trajectory as a function of the digital 3D model M from which the raw three-dimensional structure 2 is produced which makes it possible to obtain the porous monolithic inorganic support 1 after a heat treatment operation.

[0049] The extrusion head 6 comprises an inlet for the composition 4 (not shown in the figures). As shown in the figures, the extrusion head 6 also comprises an extrusion nozzle comprising a calibrated flow orifice 8, from which the composition 4 emerges. The extrusion head 6 and consequently also the extrusion nozzle with its flow orifice 8 which is integral with the extrusion head 6 are movable according to said digital 3D model M. According to the method of the invention, the composition 4 is introduced into the extrusion head 6 of the machine via an inlet in order to feed the flow orifice 8. A mechanical action can be applied to introduce the composition 4 into the head 6 via this inlet.

[0050] In the context of the invention, "mechanical action" means the application of pressure by any known technical means, such as for example a piston, a pump or an extrusion screw. This step can be carried out in the usual manner by those skilled in the art and will not be detailed here. The material leaves the flow orifice 8 thanks to a certain pressure greater than atmospheric pressure. This results in a force which is exerted vertically on the material from top to bottom at the time of extrusion and which contributes to the crushing of the material between the extrusion nozzle and the underlying hardened material.

[0051] The flow orifice 8 is placed opposite and close to the horizontal plate 5. The flow orifice 8 is movable, vertically (i.e. along the z axis) and horizontally (i.e. along the x and y axes), relative to the horizontal plate 5 which is fixed. The vertical and / or horizontal displacement of the flow orifice 8 relative to the fixed horizontal plate 5 allows the construction according to the digital 3D model M of the manipulable raw three-dimensional structure 2 resting on the horizontal plate 5 following the extrusion of a bead of material through the flow orifice 8.

[0052] According to the embodiment illustrated in the figures, the extrusion head 6 is provided with a flow orifice 8 of circular section. When the flow orifice 8 is of circular section, its diameter advantageously ranges from 0.1 mm to 10 mm, preferably from 0.1 mm to 1 mm and preferentially from 0.2 to 0.8 mm.

[0053] It is recalled that at a predefined extrusion flow rate E (determined for example by the rotational speed of the extrusion screw), a predefined displacement speed F of the extrusion head 6 and a nominal displacement height e of the extrusion head 6 corresponds to a deposit of material 3 with a nominal width L such that L=f(E, F, e). The deposit of material 3 has a cross-section with a nominal height e defined between a substantially planar upper surface 3s and a substantially planar lower surface 3i connected to each other on either side by two edges 3b of rounded shape ( figures 3 et 3A ). The nominal width L of the material deposit 3 can therefore be adjusted or modified depending on the displacement speed F and / or the extrusion flow rate of the extrusion head 6.

[0054] The extrusion head 6 is supplied with a composition 4 in the form of a paste, for example, as described in document PCT / FR2019 / 052807, or in the form of a filament or granules, as described in document PCT / FR2019 / 052808. Advantageously, the composition 4 is an inorganic composition, typically of a ceramic and / or metallic nature.

[0055] The ceramic composition is composed of a powdery solid inorganic phase and a matrix.

[0056] The powdered solid inorganic phase of the ceramic composition comprises one or more solid inorganic materials, each in the form of particles with an average diameter of between 0.1 µm and 150 µm.

[0057] The concept of mean diameter is associated with that of particle distribution. Indeed, the particles of a powder are rarely of a single size or monodisperse and a powder is therefore most often characterized by a distribution of its particle sizes. The mean diameter then corresponds to the average of a distribution of particle sizes. The distribution can be represented in different ways, such as a frequency or cumulative distribution. Some measurement techniques directly give a distribution based on number (microscopy) or mass (sieving). The mean diameter is a measure of central tendency.

[0058] Among the most commonly used central tendencies are the mode, the median, and the mean. The mode is the most frequent diameter in a distribution: it corresponds to the maximum of the frequency curve. The median represents the value at which the total frequency of values ​​above and below is identical (in other words, the same number or total volume of particles are found below the median as above). The mean must be calculated and determines the point at which the moments of the distribution are equal. For a normal distribution, the mode, the mean, and the median coincide, while they differ in the case of a non-normal distribution.

[0059] The average diameter of the constituent particles of an inorganic powder can be measured in particular by: laser light diffraction for particles ranging from 3 mm to about 0.1 µm; sedimentation / centrifugation; dynamic light scattering (DLS) for particles ranging from 0.5 µm to 2 nm; microscopy image analysis; small-angle X-ray diffraction.

[0060] Granularity of the powdery solid inorganic phase refers to the dimensions of the particles composing the powdery solid inorganic phase. Granularity is characterized by the concept of average diameter which is described above.

[0061] Most often, the ceramic composition comprises, as powdered ceramic material(s), alone or as a mixture, an oxide and / or a nitride and / or a carbide. Examples of oxides that may be suitable in the context of the invention include metal oxides, and in particular titanium oxide, zirconium oxide, aluminum oxide and magnesium oxide, titanium oxide being preferred. Examples of carbides include metal carbides, and in particular silicon carbide. Examples of nitrides that may be used include titanium nitride, aluminum nitride and boron nitride. According to a preferred embodiment, the ceramic composition comprises at least one metal oxide as powdered inorganic material, and preferably titanium oxide.

[0062] In the context of the invention, the ceramic composition has a rheology adapted in terms of plasticity for its extrusion through the extrusion head 6.

[0063] According to a first embodiment, the matrix of the ceramic composition comprises one or more solvents. The solvent(s) may be aqueous or organic. Examples include water, ethanol or acetone.

[0064] In addition, the matrix of the ceramic composition comprises one or more organic additives. Advantageously, these organic additives are soluble in the solvent(s) of the matrix. The organic additive(s) suitable in the context of the invention may be chosen, as non-limiting examples, from: binders, and for example among cellulose ethers such as hydroxyethylcellulose which is a polymer, gum arabic which is a polysaccharide, or polyethylene glycol (PEG); lubricants and plasticizers, and for example among glycerol or stearic acid; thickeners and gelling agents, and for example among xanthan gum or agar-agar which is a galactose polymer.

[0065] The mass content of powdered inorganic material(s) in the ceramic composition can range from 50 to 90%, preferably between 80 and 85% by weight, relative to the total weight of the ceramic composition.

[0066] The mass content of matrix in the ceramic composition can range from 10% to 50% by weight, preferably from 15 to 20% by weight, relative to the total weight of the ceramic composition.

[0067] This ceramic composition is not a powder but a paste. It is possible to adjust the rheology of this ceramic composition thanks to the granularity of the solid inorganic powder phase, and / or thanks to the nature of the organic additives when they are present and / or thanks to their respective proportions. Indeed, for example, the use of a matrix comprising one or more organic additives soluble in one or more solvents included in the matrix makes it possible to modify the rheology of the ceramic composition.

[0068] According to a second embodiment, the ceramic composition comprises a matrix consisting of one or more thermofusible polymers. The matrix is ​​organic in nature and solid at room temperature.

[0069] A "hot melt polymer" means a polymer that softens when heated.

[0070] Examples of hot-melt polymers that may be suitable within the scope of the invention include, used alone or as a mixture in the matrix, the following polymers or families of polymers, optionally functionalized: polylactic acid (PLA), polyvinyl alcohol (PVA), acrylonitrile butadiene styrene (ABS), polyprolylene (PP), polyethylene, polyethylene terephthalate (PET), thermoplastic polyurethane (TPU), polyolefins, thermoplastic elastomers (TPE), polyolefin-based elastomers (TPE-O) and polycarbonate.

[0071] The mass content of powdered inorganic material(s) in the ceramic composition can range from 40 to 95%, preferably between 70 and 90% by weight, relative to the total weight of the ceramic composition.

[0072] In the context of the invention, the ceramic composition, preferably in the form of granules, is preheated upstream so that the hot-melt polymer(s) soften so that the ceramic composition can be pressurized upstream of the flow orifice 8. In the usual manner, the extrusion head 6 is heated to soften the hot-melt polymer(s) thus allowing the extrusion of the ceramic composition. The temperature of the extrusion head 6 and of the flow orifice 8 can be adjusted according to the hot-melt polymer(s) present in the ceramic composition.

[0073] Furthermore, within the scope of the invention, it is possible to adjust the rheology of the ceramic composition thanks to its temperature in the extrusion head and / or the granularity of the solid powdery inorganic phase, and / or thanks to the nature of the hot-melt polymer(s) and / or thanks to their proportions.

[0074] In accordance with the invention, the method according to the invention aims to decompose the digital trajectory into paths so as to avoid, in the internal part of the raw three-dimensional structure that can be manipulated, the creation of spaces between the rounded edges of the current material deposit and those of the previously deposited material deposit. As explained in figures 1A et 1C , the deposition of cords of material carried out contiguously according to the state of the art, leads to the creation of voids of material persisting after sintering and likely to reduce the mechanical resistance of the porous monolithic inorganic support.

[0075] The method according to the invention aims to determine whether the manipulable raw three-dimensional structure comprises a wall whose width is equal to or greater than the nominal width L of the material deposit. Indeed, for a wall whose width is equal to the nominal width L of the material deposit, this wall is constructed using only superimposed material deposits without creating material voids. For this type of wall, it should be noted that the superimposed deposition of material beads does not lead to the creation of material voids except in the case where the trajectory comprises a path with a crossing as appears in relation to figures 6 And 13A à 13E .

[0076] As it emerges from the figure 6 , a path with a crossing appears for a figure-eight-shaped structure. A crossing appears when the trajectory, looping back on itself, returns to point I with coordinates Xi, Yi where a material deposit (of order n-1) has already been deposited. Crossing a material deposit (order n-1) is done by touching the material deposit previously made ( figure 13A ). The extrusion of the material is then stopped ( figure 13B ) by sliding at the same altitude and resuming extrusion after the downstream edge of the deposit of material of order n-1 ( figure 13C ). The deposit of matter of order n+1 comes in superposition of the deposit of matter of order n-1 and the crossing of this new deposit of matter is carried out as described above ( figures 13D et 13E ). As clearly shown in the figures, the juxtaposition or joining of two deposits of material when completely crossing a previously deposited deposit of material leads to the creation of voids.

[0077] THE figures 3 et 3A illustrate a first variant embodiment called conventional mode for producing a wall 10 whose width is equal to the nominal width L of the material deposit. For example, this wall 10 is part of a manipulable raw three-dimensional structure in the form of a support of circular section having a single central channel 11. The trajectory of the extrusion head 6 is broken down into circular paths of average diameter D, each of a length nD and with an elevation of the extrusion head along the vertical axis by increments e at each revolution. The extrusion head 6 performs a first revolution t while being positioned at an elevation e relative to the level of the plate 5, so that it extrudes a constant quantity of material to produce a material deposit of constant thickness e. For example, the arrow F indicates the counterclockwise direction of movement of the extrusion head 6.Once the first turn t has been completed, the extrusion head 6 rises by a value equal to the thickness e of the material deposit to perform a second turn by extruding a constant quantity of material to continuously deposit the material. The material deposits 3 are carried out in this way until the desired height is obtained.

[0078] THE figures 4 et 4A illustrate a second variant embodiment called vase mode for producing a wall 10 in the case, for example, of a manipulable raw three-dimensional structure in the form of a support of circular section having a single central channel 11. The trajectory of the extrusion head 6 is broken down into circular paths of average diameter D, each of a length equal to nD, with an elevation of the extrusion head along the vertical axis by a succession of increments so that at the end of each revolution, the sum of these increments makes it possible to obtain, at each revolution, a deposit of material of thickness e.

[0079] During the first revolution t, the extrusion head extrudes an increasing quantity of material proportional to its position on the ramp with an average slope e / nD. Once the first revolution t has been completed, the extrusion head 6 makes its second revolution following the same average slope e / nD and extruding a constant quantity of material to continuously deposit the material at an elevation corresponding to the thickness e. The material deposits 3 are carried out in this way until the desired height is obtained.

[0080] In the case where the raw manipulable three-dimensional structure comprises a wall whose width is greater than the nominal width L of the material deposit, then the material deposits must be produced in accordance with the invention since it is no longer possible to construct this wall using only superimposed material deposits. In accordance with the invention, the method provides for an entanglement of the material deposits 3 as a result of an imbrication by overlapping(s) and / or crossing(s) of said material deposits 3 to avoid the creation of spaces or voids of material between the material deposits. Entanglement within the meaning of the invention, independently of the definition given by quantum mechanics, is understood to mean the state of the material deposits entangled due to the overlaps and / or crossings.

[0081] Also, for a wall 10 whose width is greater than the nominal width L of the material deposit 3, the method according to the invention aims to decompose the digital trajectory of the extrusion head 6 exclusively into paths with overlap and / or into paths with crossing. It must be understood that the extrusion head 6 (or more precisely its carrier carriage) follows point after point, a trajectory completely defined from the beginning to the end of the manufacturing process of the manipulable raw three-dimensional structure 2, by a succession of points. Each of these points is spatially predefined by its Cartesian coordinates Xi, Yi, Zi. Xi and Yi define exactly the position of the center of the circular orifice 8 of the extrusion nozzle.The extrusion head 6 thus moves from a point A (Xa, Ya, Za) to a point B (Xb, Yb, Zb) following a vector AB, then from point B to a point C following the vector AC, and so on, conforming to a succession of lines of instructions called G-code instructions of the intermediate software between the 3D digital model and the printing machine. It should be noted that in addition to the determination of the trajectory at each of its points determined by the Cartesian coordinates Xi, Yi, Zi, all the parameters are defined for each of these points, namely in particular the extrusion flow rate E and the displacement speed F of the extrusion head 6.

[0082] It should be understood that the digital trajectory of the extrusion head 6 is decomposed into overlapping paths and / or crossing paths. An overlapping path corresponds as illustrated in figures 5 et 5A , to a part of trajectory for which a deposit of material 3 (of order n) partially overlaps at least one edge 3b of a deposit of material 3 (of order n-1) previously deposited so as to avoid in the internal part of the raw three-dimensional structure that can be manipulated, spaces between the rounded edges of the deposit of material in progress and those of the deposit of material previously deposited. As this emerges more precisely from the figure 5A , the material being deposited (of order n) partially overlaps at least one edge 3b of a previously deposited material deposit (of order n-1), by a part of overlapping material 3c presented in its thickness, that is to say between the upper face 3s and the lower face 3i of said deposit in progress. In addition, this part of overlapping material 3c has a thickness strictly less than the nominal height e.

[0083] According to a characteristic of the method according to the invention, for a path with overlap, the extrusion head 6 is controlled to adjust the extrusion flow rate as a function of the degree of overlap of the overlapping part of material on the previously deposited material deposit.

[0084] A path with a crossing corresponds as illustrated in figures 6A et 6B , to a part of trajectory for which a deposit of material in the process of being deposited (of order n) crosses at least one deposit of material previously deposited (of order n-1), with a complete overlap of said deposit of material previously déposé deso as to avoid in the internal part of the manipulable raw three-dimensional structure, spaces between the rounded edges of the current material deposit and those of the previously deposited material deposit. In a path with crossing, the material being deposited (order n) completely overlaps, by an overlapping part of material 3c, the previously deposited material deposit (order n-1), that is to say by extending at least from one edge 3b to the other of the previously deposited material deposit. This crossing between these two material deposits can occur according to all possible angulations between the directions of these two material deposits. The overlapping part of material 3c is considered in the thickness of the current material deposit, that is to say between the upper face and the lower face of said current deposit. In addition, this overlapping part of material 3c has a thickness strictly less than the nominal height e.

[0085] The preceding description results in an interweaving of the deposits of matter 3 between them. Such an interweaving exists from the moment when there is in a turn, at least one path with overlap and / or one path with crossing. Each of the following turns which necessarily comes to “cover” the preceding overlap(s) and / or crossing(s) creates an entanglement of the deposits of matter 3. The entanglement of the deposits of matter is thus the result of multiple turns for each of which there is at least one path with overlap and / or one path with crossing.

[0086] According to a characteristic of the method according to the invention, for a path with crossing, the extrusion head 6 is controlled to reduce the quantity of material deposited to produce the overlapping part of material having a thickness strictly less than the nominal height e. Thus, as clearly appears in Figures 6A and 6B, each material deposit has a nominal height e except at or when passing over a material deposit already made.

[0087] Thus, in the example illustrated in Figures 6A and 6B , a first deposit of material n is made with a thickness less than the nominal height e, for example equal to e / 2. For a deposit of material n which crosses the deposit of material n-1 previously made, this deposit of material n is made with a nominal thickness e except when it overlaps the previous deposit of material n-1. When the extrusion head is overhanging the deposit of material, the extrusion flow rate is reduced so that the overlapping part 3d of the deposit has a thickness less than the nominal thickness e, equal to e / 2 in the illustrated example. In this way, the crossing paths made according to the principle of the invention do not have material voids unlike the prior art as illustrated in Figures 13C to 13E .

[0088] According to a preferred embodiment of the invention, the extrusion head 6 is mounted to move along the predefined digital trajectory T to perform a succession of turns t, each corresponding to the path taken to return to the same position in the horizontal plane with an elevation corresponding to a nominal height e. In other words, the digital trajectory of the extrusion head 6 is broken down into turns, considering that for each turn, the extrusion head rises by the nominal height e. Of course, the number of turns t is chosen in order to obtain the desired height for the raw manipulable three-dimensional structure 2.

[0089] In each of these turns t, the path of the extrusion head 6 is one or more paths with overlap and / or one or more paths with crossing. For each of these turns, the extrusion head 6 follows a path formed by a succession of points with coordinates Xi, Yi, Zi as explained previously, with the possibility of elevation along the vertical axis, on one or more of these points.

[0090] According to a first example of implementation described more precisely in relation to the Figures 7 to 7B And 8 à 8C , the method provides for controlling the extrusion head 6 so that over at least one revolution, the extrusion head rises at least once by an intermediate height which is a fraction of the nominal height e.

[0091] According to a second example of implementation described more precisely in relation to the Figures 9 to 9B And 10 à 10C, the method provides for controlling the extrusion head 6 so that over at least one revolution, the extrusion head is positioned at different points of the path, rising at each point by a height increment whose sum corresponds to the nominal height e.

[0092] The following description in relation to the Figures 7 to 7B And 8 à 8C , describes the first example of implementation of the method called "sequential vase mode" consisting of building a part of the path at the same altitude a (for example a=e / 2) then incrementing in elevation by a value a in order to complete the tour and overlap the previous deposit of a part of overlapping material of value a. According to this method, the nominal height e is an integer multiple of a.

[0093] There Figure 7B shows the first half of the path to be traveled by the extrusion head corresponding to a circle of diameter D1. As illustrated in the Figures 7 and 7A, a first bead of material 3 is deposited on the horizontal plate 5 with an elevation equal to e / 2 continuous along the entire path of the circle of diameter D1. For the purposes of the invention, this path, which covers a circumference of 360°, corresponds to a half-turn. Once this half-turn has been completed at the same altitude e / 2, the extrusion head 6 and therefore the center of the flow orifice 8 shifts radially towards the center of the circle by a distance equal to d = (D2-D1) / 2 and rises by an increment equal to e / 2 following a circle of diameter D2 ( Figures 8A , 8B). This results in a deposit of material which partially overlaps the inner edge 3b of the previously deposited material deposit, by an overlapping part of material 3c presented in its thickness. It should be noted that the overlapping part of material 3c has a thickness strictly less than the nominal height e. The extrusion head 6 has thus traveled a revolution t in the sense of the invention corresponding to the path with the circle of diameter D1 followed by the circle of diameter D2 ( Figure 8B ).

[0094] In the position shown in the Figure 8A, the extrusion head 6 (and therefore the center of the flow orifice 8) is offset radially outward from the circle D2 by a distance equal to d and rises again by an increment e / 2 so as to partially overlap the previous material deposit along the circle D1. This results in a material deposit which partially overlaps the outer edge 3b of the previously deposited material deposit, by an overlapping part of material 3d presented in its thickness. The overlapping part of material 3d has a thickness strictly less than the nominal height e. The extrusion head 6 is offset radially inward from the circle D1 by a distance equal to d and rises again by an increment e / 2 so as to partially overlap the previous material deposit along the circle D2.This results in a deposit of material which partially overlaps the inner edge 3b of the previously deposited deposit of material, by a portion of overlapping material 3c presented in its thickness. The extrusion head 6 has thus completed a second revolution t in the sense of the invention corresponding to the path with the circle of diameter D1 followed by the circle of diameter D2 (. Figure 8C ).

[0095] The extrusion head 6 is then controlled according to a number of turns allowing the construction according to the desired height for the raw manipulable three-dimensional structure 2. It should be noted that in the illustrated example, the paths according to the first turn and the second turn are identical. Of course, it can be envisaged that the paths of the different turns are different from each other. Similarly, the nominal height e for each of the turns which is identical in the illustrated example, can be different for the different turns.

[0096] The following description in relation to the Figures 9 to 9B And 10 à 10C , describes the second example of implementation of the process called “continuous vase mode” for which the extrusion head 6 extrudes an increasing quantity of material proportional to its position.

[0097] There Figure 9B shows the first half of the path to be traveled by the extrusion head corresponding to a circle of diameter D1. As illustrated in the Figures 9 and 9A, a first bead of material is deposited on the horizontal plate 5 with a continuous progressive elevation along the entire path of the circle of diameter D1 to reach at the end of the path of circle D1, a height equal to e / 2. For the purposes of the invention, this path corresponds to a half-turn and it should be noted that at the quarter turn, the thickness of the deposit of material is equal to e / 4. Once this half-turn has been made to reach the altitude e / 2, the extrusion head 6 shifts radially towards the center of the circle by a distance equal to d= (D2-D1) / 2 and rises progressively continuously following a circle of diameter D1 to reach the altitude e at the end of the path traveled along this diameter D1 ( figures 10, 10A, 10B). This results in a deposit of material which partially overlaps the inner edge 3b of the previously deposited material deposit, by an overlapping part of material 3d presented in its thickness. It should be noted that the overlapping part of material has a thickness strictly less than the nominal height e. The extrusion head 6 has thus traveled a revolution t in the sense of the invention corresponding to the path with the circle of diameter D1 followed by the circle of diameter D2.

[0098] In the position illustrated in Figures 10A, the extrusion head 6 is offset radially towards the outside of the circle D2 by a distance equal to d and rises progressively by an increment e / 2 so as to partially overlap the previous material deposit according to the circle D1. This results in a material deposit which partially overlaps the outer edge 3b of the previously deposited material deposit, by an overlapping part of material 3d presented in its thickness. The overlapping part of material has a thickness strictly less than the nominal height e. The extrusion head 6 is offset radially towards the inside of the circle D1 by a distance equal to d and rises progressively again by an increment e / 2 so as to partially overlap the previous material deposit according to the circle D2. This results in a material deposit which partially overlaps the inner edge of the previously deposited material deposit, by an overlapping part of material presented in its thickness.The extrusion head has thus completed a second turn t in the sense of the invention corresponding to the path with the circle of diameter D1 followed by the circle of diameter D2 (. Figure 10C ).

[0099] The extrusion head 6 is controlled in this way according to a number of turns allowing the construction according to the desired height for the raw three-dimensional structure that can be manipulated. It should be noted that in the illustrated example, the paths according to the first turn and the second turn are identical. Of course, it can be envisaged that the paths of the different turns are different from each other. Similarly, the nominal height for each of the turns, which is identical in the illustrated example, can be different for the different turns.

[0100] There figure 11 allows to illustrate by way of example, by curve A, the path of the extrusion head 6 for the process called “sequential vase mode” described in relation to Figures 7 to 7B And 8 à 8C. The path is traveled for example from point to point by two stages of increments e / 2. According to this example, the extrusion head 6 is controlled so that on at least one revolution t, the extrusion head rises at least once by an intermediate height which is a fraction of the nominal height.

[0101] Curve B describes the path of the extrusion head 6 for the process called “continuous vase mode” illustrated by the Figures 9 to 9B And 10 à 10C. In the example illustrated, each path (one turn t) is traveled according to fifteen points (with coordinates in X, Y) that is to say with fifteen increments or height steps dZ proportional to the distance which separates two successive points, that is to say fifteen increments of equal height dZ=e / 15. The method thus aims to control the extrusion head 6 so that over at least one turn, the extrusion head is positioned at different points of the path, rising at each point by a height increment whose sum corresponds to the nominal height e. It should be noted that the figure 11 displays the continuous progressive elevation curve C corresponding to the progressive elevation along the Z axis of the extrusion head.

[0102] It is clear from the above description that the extrusion head 6 is controlled so that, through a succession of revolutions, the extrusion head rises to build the raw manipulable three-dimensional structure 2 in accordance with the digital 3D model M, following a trajectory with an uninterrupted deposition of material 3 from the beginning to the end of the construction of the raw manipulable three-dimensional structure 2.

[0103] Furthermore, the extrusion head 6 is controlled so that during each revolution t, the extrusion head is offset in the horizontal plane X, Y so that the material being deposited partially overlaps an edge of a previously deposited material deposit. Advantageously, for a path with overlap, the extrusion head 6 is controlled to adjust its position in the horizontal plane X, Y to define the degree of overlap of the overlapping material portion 3d on the previously deposited material deposit. As described previously, the offset d in the horizontal plane X, Y between the consecutive paths makes it possible to choose the degree of overlap between the material deposits.

[0104] In the exemplary embodiments illustrating the principle of the invention, it should be noted that the wall to be constructed has a width that can be constructed from two partially overlapping deposits of material. Of course, the principle of the invention can be implemented to construct a wall whose width requires a greater number of deposits of material as illustrated by way of example in Figures 12A and 12Bwith three deposits. According to this embodiment, the wall to be constructed delimits two contiguous channels and has a width with overlaps of three deposits. The construction of this wall is obtained in vase mode by following the path a1+b1+c1+d1+e1+f1+g1 then the path a2+b2+c2+d2+e2+f2+g2 then a3+b3+... The flow rate of the extrusion head 6 has dropped to zero when the extrusion head 6, ending fi, joins ei until the bifurcation (following gi) to join ai+1. The thicknesses of the material deposits of the first turn are in proportion to the path traveled while the thicknesses of the material deposits from the second turn are equal to the nominal thickness.

[0105] According to an implementation characteristic of the invention, it should be noted that for a path with overlap, the extrusion head 6 is controlled to keep the flow rate of deposited material constant while the flow rate of the extrusion head 6 is reduced for a path with crossing.

[0106] The method according to the invention thus makes it possible to construct a manipulable raw three-dimensional structure 2 without creating empty material spaces, whatever the shape or dimensions of the walls. figure 15 illustrates an example of a manipulable raw three-dimensional structure 2 which, after sintering, has no empty space of material in the walls produced. The examples described above explain a first advantageous variant of production called conventional mode or vase mode for which the extrusion head follows a trajectory with an uninterrupted deposition of material 3 from the beginning to the end of the construction of the manipulable raw three-dimensional structure 2.

[0107] There figure 14illustrates a second embodiment variant for which the extrusion head 6 is mounted to move along the predefined digital trajectory T to carry out deposits of material in superposition by layers each rising by a nominal height e. The deposition of material by layers is described in particular by patent applications WO 2020 / 109715 and WO2020 / 109716. This method consists of forming a first layer 3 1 and 3 2 , according to the digital 3D model M predetermined by the computer design software, thanks to the horizontal displacement of the flow orifice 8 above the horizontal plate 5.

[0108] The extrusion head 6 moves horizontally, and therefore parallel to the horizontal plate 5, along a predetermined path based on the digital 3D model M, to form the first layer. After the first layer has been deposited, the extrusion head 6 moves so that the deposited bead forms the second layer 3 3 in accordance with the digital 3D model M. For this, the extrusion head 6 moves vertically (i.e. along the Z axis) and horizontally (i.e. along the X and / or Y axes) to the desired position. The extrusion of the inorganic composition 4 through the extrusion head 6 may be continuous or discontinuous. Thus, the second layer is deposited on the first layer by superimposing the deposit of material on the previously deposited layer, in accordance with the digital 3D model M.

[0109] Of course, the material deposition is carried out to ensure an overlap (partial or complete) as described above to avoid the creation of voids between the material deposits. Thus, in the example illustrated in figure 14 , the material deposit 3 3 of the second layer partially overlaps, from its two opposite edges, the neighboring edges of two previously deposited material deposits 3 1 and 3 2 , making it possible to avoid the creation of empty spaces.

[0110] The method according to the invention makes it possible to construct manipulable raw three-dimensional structures 2 intended to form monolithic porous inorganic supports 1, having the mechanical resistance characteristics adapted to their use in tangential filtration. Advantageously, the extrusion head 6 is controlled in order to provide in the manipulable raw three-dimensional structure 2, at least one channel 11 for circulation of a fluid medium to be treated. The wall of this channel 11 is produced by the rounded edges 3b of the material deposits located opposite the overlapping part of material. As illustrated in the drawings, the extrusion head 6 is configured so that the material deposits have rounded edges 3b. Thus, a channel 11 has a wall having rounded reliefs each extending over the entire periphery of the channel while being defined by the rounded edge 3b of the material deposits.These rounded perimeter reliefs extend in a superimposed manner along the length of the canal as illustrated in . figures 15 And 16 . On the scale of the thickness of the material deposits e, these rounded perimeter reliefs participate at their level, in this channel, in tangential filtration, in the generation of turbulence all along the channel. figure 16 allows us to see that these rounded perimeter reliefs are present even when the internal wall of the channels 11 is coated with separating layers whose profile appears in the form of a white line on the figure 16. The separating layer(s) thus conform to the rounded perimeter reliefs whose rounded profile persists to participate in the creation of turbulence in the channel 11. It should be noted that the porous monolithic inorganic support 1 manufactured according to the method according to the invention has an external surface also having a succession of rounded perimeter reliefs St which extend in a superimposed manner along the support, as illustrated in Figures 2B , 15 And 16 .

Claims

1. A method for the production of at least one porous monolithic inorganic support (1) having at least one channel for circulating the fluid to be treated and having a porosity comprised between 10% and 60% and a mean pore diameter ranging from 0.5 µm to 50 µm, by means of a 3D printing machine (I) comprising at least one extrusion head (6) mounted moveably in space above a fixed horizontal plate (5), by being successively moved with a nominal height (e) along a predefined numerical trajectory (T) to effect superimposed material depositions each having a nominal width and a defined thickness between a lower surface and an upper surface, said 3D printing machine allowing depositing material in the form of: - a bead with rounded edges so as to create rounded perimeter reliefs participating in the generation of turbulence on the wall of at least one circulation channel, - a composition (4) to build, on said horizontal plate (5), from the predefined numerical trajectory (T), walls of a manipulable three-dimensional green structure (2) to form the monolithic porous inorganic support(s) (1), characterized in that the method consists of: - For a wall whose width is greater than the nominal width (L) of the material deposition, to break down the numerical trajectory exclusively into overlapping paths and crossing paths; - To supply the extrusion head (6) of the 3D printing machine (I) with a composition (4), - To drive the extrusion head according to the numerical trajectory so that: * for an overlapping path, the material being deposited partially overlaps at least one edge of a previously deposited material deposition, by an overlapping material part presented in its thickness and having a thickness strictly less than the nominal height (e) so as to avoid, in the inner part of the manipulable three-dimensional green structure, spaces between the rounded edges of the material deposition being deposited and those of the material deposition previously deposited, * for a crossing path, the material being deposited intersects at least one previously deposited material deposition with a complete overlap of said previously deposited material deposition, by an overlapping material part presented in its thickness and having a thickness strictly less than the nominal height (e) so as to avoid, in the inner part of the manipulable three-dimensional green structure, spaces between the rounded edges of the material deposition being deposited and those of the material deposition previously deposited.

2. The method according to claim 1, according to which the extrusion head (6) is mounted moveably along the predefined numerical trajectory (T) in order to carry out a succession of turns each corresponding to the path travelled in order to find the same position in the horizontal plane with an elevation corresponding to a nominal height (eN).

3. The method according to claim 2, according to which the extrusion head is driven so that, over at least one turn, the extrusion head rises at least once by an intermediate height which is a fraction of the nominal height.

4. The method according to claim 2, according to which the extrusion head is driven so that, over at least one turn, the extrusion head is positioned at different points of the path, rising at each point by a height increment, the sum of which corresponds to the nominal height.

5. The method to one of claims 2 to 4, according to which the extrusion head is driven so that by the succession of turns, the extrusion head rises to build the manipulable three-dimensional green structure (2) in accordance with the 3D digital model (M), following a trajectory with an uninterrupted material deposition (3) from the beginning to the end of the construction of the manipulable three-dimensional green structure (2).

6. The method according to any one of claims 2 to 5, according to which the extrusion head is driven so that, during each turn, the extrusion head is offset in the horizontal plane so that the material being deposited partially overlaps an edge of a deposition of previously deposited material.

7. The method according to one of the preceding claims, according to which, for a crossing path, the extrusion head is driven to reduce the quantity of material deposited to produce the overlapping material part having a thickness strictly less than the nominal height (eN).

8. The method according to one of the preceding claims, according to which, for a path with the same overlap, the extrusion head is driven to keep the flow rate of deposited material constant.

9. The method according to one of the preceding claims, according to which, for an overlapping path, the extrusion head is driven to adjust its position in the plane to define the degree of overlap of the overlapping material part on the previously deposited material deposition.

10. The method according to one of the preceding claims, according to which, for an overlapping path, the flow rate of the extrusion head is adjusted according to the degree of overlap of the overlapping material part on the previously deposited material deposition.

11. The method according to claim 1, according to which the extrusion head (6) is mounted moveably along the predefined numerical trajectory (T) in order to carry out superimposed material depositions in strata each rising by a nominal height (e).

12. The method according to one of the preceding claims, according to which the extrusion head is driven so as to provide in the manipulable three-dimensional green structure (2), at least one channel for circulating a fluid medium to be treated, possessing a wall having a succession of rounded reliefs generating variations in the passage section of the channel, these rounded reliefs being formed by the part of material situated opposite the overlapping material part.

13. The method according to one of the preceding claims, according to which the extrusion head is configured so that the part of the material located opposite the overlapping material part has a rounded edge.

14. The method according to one of the preceding claims, according to which the manipulable three-dimensional green structure (2) is placed in a heat treatment furnace in order to carry out a sintering operation.

15. A method for the preparation of a tangential filtration membrane comprising the manufacture according to any of the preceding claims of a porous monolithic inorganic support (1) in which is provided at least one channel (11) for circulating the fluid medium to be treated, followed, after the sintering of said support, by a step of creating at least one separating layer on the walls of the channel or channels (11).

16. A porous monolithic inorganic support (1), having a porosity comprised between 10% and 60% and a mean pore diameter ranging from 0.5 µm to 50 µm, said porous monolithic inorganic support possessing an outer surface having a succession of rounded perimeter reliefs (st) and at least one channel for circulating the fluid to be treated whose wall has rounded perimeter reliefs participating in the generation of turbulence, characterized in that said porous monolithic inorganic support (1) is manufactured according to any one of claims 1 to 14.

17. A tangential filtration membrane comprising a porous monolithic inorganic support (1) according to the preceding claim, provided with at least one channel (11) for circulating the fluid medium to be treated, whose wall with rounded perimeter reliefs is coated with at least one separating layer.

18. A tangential filtration membrane according to the preceding claim, wherein the rounded profile of the perimetric reliefs of the inner wall of the channels (11) remains to participate in the creation of turbulence in the channel (11) after the deposit of one or more separating layer(s).