Capsule manufacturing process and capsule obtained by this process.

Abstract

The invention relates to a method for manufacturing capsules, each capsule preferably having a volume of at least 0.2 ml and comprising: - a fluid core - a membrane surrounding the fluid core. The method comprises, for the manufacture of each capsule, the extrusion of a droplet through an extrusion nozzle into an outlet fluid, said droplet comprising at least the fluid core, said nozzle being provided with a grid at its outlet opening onto the outlet fluid. The extrusions are carried out discontinuously between the different capsules. Figure for the abstract: Fig. 6

Description

Title of the invention: Process for manufacturing capsules and capsule obtained by this process. technical field

[0001] The present invention relates to a method for manufacturing fluid-core capsules. It also relates to capsules obtained by said method.

[0002] Such a device allows a user to manufacture large fluid-filled capsules. The field of the invention is more particularly, but not exclusively, that of encapsulation for the food, cosmetics, household product (e.g., laundry detergent, dishwashing liquid, etc.), biotechnology, etc. Prior art

[0003] Documents WO202384233_Al, WO202384239_Al, and WO2018172781_Al [1] [2] [3] describe single-use packaging or liquid encapsulations.

[0004] Methods for producing fluid-core capsules with a hydrogel membrane via liquid flow are known, particularly by co-extrusion in air, but the size is limited to a few millimeters when the droplet formation regime, which forms the capsule precursors, is a drop-by-drop regime, i.e., one in which gravity drives the formation of said droplets. It is possible to describe the evolution of droplet size and volume as a function of nozzle diameter [4]. This limitation is imposed by gravity, which makes co-extrusion unstable with centimeter-sized nozzles.Indeed, beyond a critical diameter of the extrusion nozzle and below a limiting volumetric flow rate of the liquid for which the so-called drip-feed regime is operational, the liquid flows under the effect of its own weight and thus does not form a volume of liquid gathered in a spherical or spheroidal shape, but a jet that thins and fragments into multiple droplets. Similarly, without flow, the interface separating the two fluids at the nozzle outlet is unstable beyond a critical nozzle diameter, which depends on the properties of the fluids, and at which point the fluid initially in the nozzle flows out of the nozzle while allowing the outlet fluid to enter the nozzle.

[0005] An existing alternative involves forming an alginate hydrogel film, wrapping the liquid product to be encapsulated in it, and then sealing the film. This allows for the creation of a hydrogel sachet, potentially with a larger volume. This process does not appear easy to industrialize, and the resulting product does not seem to have excellent aesthetic or ergonomic characteristics, particularly useful for the cosmetics market.

[0006] The object of the present invention is to solve at least one of these problems posed by the prior art, namely to allow encapsulation: - with better stability, and / or - with a larger volume per capsule, and / or - with better industrialization possibilities, in particular potentially better production rates and / or better manufacturing reproducibility, and / or - allowing for shapes that are more suitable or practical for a user, particularly in terms of ergonomics and / or aesthetics. Description of the invention

[0007] This objective is achieved with a method for manufacturing capsules, each capsule preferably having a volume of at least 0.2 ml (or even at least 0.5 ml), and comprising: - a fluid core - a membrane surrounding the fluid core

[0008] The process comprising, for the manufacture of each capsule, extruding a drop through an extrusion nozzle into an outlet fluid, said drop comprising at least the fluid core, said nozzle being provided with a grid at its outlet opening onto the outlet fluid

[0009] the extrusions being carried out discontinuously between the different capsules.

[0010] The extruded droplet may comprise:

[0011] - the fluid core without shell fluid surrounding the fluid core (preferably including only the fluid core) or without the membrane, or

[0012] - the fluid core and a shell fluid surrounding the fluid core, the extrusion including a co-extrusion of the fluid core and the shell fluid.

[0013] In a first embodiment, the outlet fluid may comprise or consist of a liquid. The outlet fluid may comprise or consist of an oil.

[0014] In this first variant:

[0015] - the extruded droplet may comprise a polymer solution and the outlet fluid may include an agent or means arranged to gel or crosslink the polymer, or

[0016] - the outlet fluid may comprise a polymer solution and the extruded droplet may include an agent designed to gel or crosslink the polymer.

[0017] In a second variant, the outlet fluid may comprise or consist of gas, preferably air.

[0018] In this second embodiment, the droplet extruded in the outlet fluid can fall, after passing through the outlet fluid, into a liquid bath. The liquid bath may comprise an aqueous solution.

[0019] In this second variant:

[0020] - the extruded droplet may comprise a polymer solution and the liquid bath may include an agent or means arranged to gel or crosslink the polymer, or

[0021] - the liquid bath may comprise a polymer solution and the extruded droplet may include an agent designed to gel or crosslink the polymer.

[0022] A density of the fluid of the extruded droplet is preferably greater than a density P2 of the outlet fluid.

[0023] The grid may only include holes or fluid passages whose largest dimension di is less than: - 10 mm, preferably less than 5 mm, and / or - 7rlc where , _ / r \1 / 2 with s the gravitational constant, 'P a mass c “ l / volumetric density of the extruded droplet fluid, P2 a density of the outlet fluid, V the surface or interfacial tension between the extruded droplet fluid and the outlet fluid.

[0024] The grid may only include holes or fluid passages with a gap of less than 2 mm, preferably less than 1 mm and preferably less than 0.8 mm.

[0025] The grid can be made of plastic, bioplastic, wood, glass, metal, and / or a material coated with a fluorinated polymer.

[0026] The grid can be, with respect to the Earth's gravitational force or gravitational field, horizontal or substantially horizontal at an angle less than or equal to , with ac defined such that • _ U , with the constant StlW - gravitational, ^1 a density of the extruded droplet fluid, P2 a density of the outlet fluid, P the surface or interfacial tension between the extruded droplet fluid and the outlet fluid, D the outlet diameter of the extrusion nozzle, and di which is the largest dimension of the hole or grid passage and which is preferably less than P.

[0027] For the extrusion of each drop, the number of Froude pr — ...JL.... can be greater than 0.5, preferably greater than 1, with Fr defined as the ratio of the average velocity U of the fluid in the extruded droplet at the extrusion nozzle outlet to the fall velocity / pM of the extruded droplet over a distance, along of the force of Earth's gravitation and below a center of the grid, equal to the radius of the nozzle DU, and with the gravitational constant.

[0028] According to yet another aspect of the invention, a capsule obtained by the process according to the invention is proposed, preferably having a volume of at least 0.2 ml (or even at least 0.5 ml), and comprising: - a fluid core - a membrane surrounding the fluid core. Description of the figures and methods of implementation

[0029] Other advantages and features of the invention will become apparent from the detailed description of implementations and embodiments, which are by no means limiting, and from the following accompanying drawings:

[0030] [Fig-1] [Fig.1] illustrates the stability conditions of an interface between two fluids 1, 2 which is perpendicular to the gravitational field g,

[0031] [Fig.2] [Fig.2] illustrates two variants of a first embodiment of the process according to the invention, which is the preferred embodiment of the invention,

[0032] [Fig.3] [Fig.3] illustrates possible configurations of grids 6 used in the first embodiment of the process according to the invention,

[0033] [Fig.4] [Fig.4] illustrates another possible grid configuration 6 used in the first embodiment of the process according to the invention,

[0034] [Fig.5] Figure 5 illustrates the stability limit as a function of the inclination angle a of the grid 6 in the first embodiment of the method according to the invention,

[0035] [Fig.6] [Fig.6] illustrates the Froude number beyond which the extruded volume of fluid 1 is not deformed during the extrusion step of the first embodiment of the process according to the invention,

[0036] [Fig.7] Fig.7 illustrates a second embodiment of the process according to the invention,

[0037] [Fig.8] [Fig.8] illustrates experimental data of the maximum lateral size normalized by the internal diameter of the nozzle 7 obtained for different extrusion speeds and therefore of the Froude number for water, of viscosity 1 mPa.s, and an alginate solution of a viscosity of 1200 mPa.s for two different grids 6: - Case of [Fig.8](a): a sieve with di=1 mm and d2=0.35 mm and D = 20 mm; - Case of [Fig.8](b): a perforated plate with circular holes arranged according to a hexagonal grid where di=1 mm and d2=l mm and h = 2mm and D = 19.5 mm,

[0038] [Fig.9] Fig.9 illustrates, in profile view, the use of a cup 11 which can be rotation (around a rotation axis 12) in order to cut the fluid filament or liquid connecting drop 4 to nozzle 7 in any of the embodiments described with reference to the preceding figures,

[0039] [Fig. 10] [Fig. 10] illustrates, from a top view, this use of a cup 11 of [Fig. 9], and

[0040] [Fig. 11] [Fig. 11] illustrates different positions of inclination of the fluid 1: a. On its part a), without grid 6 (comparative test), b. On its part b), with grid 6 (invention).

[0041] These embodiments being in no way limiting, variants of the invention may be considered, in particular, comprising only a selection of features described or illustrated hereafter, isolated from the other described or illustrated features (even if this selection is isolated within a sentence including these other features), if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art. This selection includes at least one preferably functional feature without structural details, and / or with only a portion of the structural details if this portion alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0042] Fig. 1 illustrates the stability conditions of an interface 3 between two fluids 1, 2, this interface 3 being perpendicular to the gravitational field g.

[0043] As illustrated in part b of Figure 1, the interface 3 is unstable when the density of an extruded fluid 1 is greater than that P2 of the fluid 2 into which the extruded fluid 1 flows, if the diameter Æ of the container or the extrusion nozzle 7 is greater than the critical length where , / y \1 / 2 where F is the lc “ ( (p^ J surface or interfacial tension between the two fluids 1, 2 [5].

[0044] is commonly called capillary length, and is a characteristic length below which the capillary force, due to surface tension, becomes greater than the gravitational force. The maximum size ® of the nozzle without a grid beyond which the interface becomes unstable, i.e. the fluid or liquid flows under the effect of its own weight, is equal to 2ttIc [6]

[0045] As illustrated in part (a) of Figure 1, interface 3 is stable for D < 2jilc.

[0046] As illustrated in part (c) of Figure 1, interface 3 is stabilized for D > 2jtIc if a grid 6 having holes with a maximum lateral size < ttIc is arranged at interface 3.

[0047] Figure 2 illustrates two variants of a first embodiment of process 10 according to the invention, which is the preferred embodiment of the invention.

[0048] The first embodiment relates to a method for manufacturing fluid-core capsules 5 41 further having a membrane 51 preferably made of hydrogel polymers, capsule with a volume of at least 0.2 ml (or even at least 0.5 ml), which corresponds to a size D greater than 0.7 centimeter (or even at least 1 cm). The manufacturing process is based on the extrusion of the core fluid 41 into an outlet fluid 2, possibly with co-extrusion of a shell fluid 42, consisting of a polymer solution.

[0049] As described below: - the fluid core 41 comprises or consists of at least one of the fluids of the extruded fluid 1 or, if this extruded fluid 1 comprises only one liquid, comprises or consists of the extruded fluid 1. The membrane 51 is formed following a reaction between a polymer and means for gelling or crosslinking the polymer. The polymer and the means for gelling or crosslinking the polymer are distributed separately in two different media: fluid 1 (and therefore the necessarily present core 41 and / or the optional shell 42), fluid 2, and an optional bath 8. The means for gelling or crosslinking the polymer typically include either a chemical gelling or crosslinking agent or means for imposing a physical parameter for gelling or crosslinking, such as a specific gelling or crosslinking temperature.

[0050] The fluid core 41 and / or the extruded fluid 1 and / or the hull fluid 2 does not consist of a gas.

[0051] The fluid core 41 and / or the extruded fluid 1 and / or the hull fluid 2 comprises (preferably at least 70%, preferably at least 90% by mass) or consists of each individually of: - A liquid, and / or - a non-Newtonian fluid, that is to say, one whose viscosity depends on the stress to which it is subjected, and / or - a yield stress fluid, set in flow beyond a yield stress, and / or - a complex fluid, preferably a binary mixture exhibiting a coexistence between two phases: solid-liquid (suspensions or solutions containing macromolecules such as polymers or giant micelles), liquid-gas (foams) and / or liquid-liquid (emulsions), and / or - a viscoelastic fluid.

[0052] The fluid core 41 and / or the extruded fluid 1 and / or the shell fluid 2 may, for example, comprise a viscous food product possibly including solid pieces, a cosmetic or pharmaceutical cream or gel, a dispersion of particles or biological cells (mammalian, plant or microorganism cells, unicellular or multicellular, etc.), an oil-in-water emulsion, or multiple emulsions, or a water-in-oil emulsion, or an oil which may contain a molecule of interest, etc. The possibilities are endless, provided that this fluid can flow. In the case of coextrusion (not illustrated in [Fig. 2], but visible in Figure 6c), this coextrusion results, for example, in the formation of a droplet 4, composed of a fluid core 41 coated by a layer 42 of the polymer solution. The gelation or crosslinking of the outer layer 42 is obtained, for example, by immersing the droplet 4 in a gelling or crosslinking bath 8.

[0053] Obtaining capsules 5 with a size of centimetre is made possible:

[0054] - by adding a grid 6, having a millimeter mesh size, at the output of coextrusion nozzle 7

[0055] - as well as by discontinuous extrusion of the fluid 1, i.e. by jerks.

[0056] The addition of a grid 6 and the operating method of making the liquid(s) of the extruded fluid 1 flow makes it possible to overcome the problem of instability and thus form capsules 5 of centimeter size.

[0057] Thus, this process 10 is a process for manufacturing capsules, each capsule 5 having a volume of at least 0.2 ml (or even at least 0.5 ml) and comprising: - a fluid heart 41 - a membrane 51 (preferably in gel and / or solid form) surrounding the fluid core

[0058] the process comprising, for the manufacture of each capsule, an extrusion of a droplet 4 of extruded fluid 1 through an extrusion nozzle 7 into an outlet fluid 2, said extruded droplet 4 comprising at least the fluid core 41, said nozzle 7 being provided with a grid 6 at the outlet of the nozzle 7 opening onto the outlet fluid 2, the extrusions being carried out discontinuously between the different extruded drops 4 or capsules 5 manufactured.

[0059] The extruded fluid 1 is preferably a liquid. The fluid 1 may comprise a mixture of several liquids.

[0060] The outlet fluid 2 is preferably liquid and / or gaseous, but may more generally comprise or consist of a liquid, and / or a non-Newtonian fluid, and / or a yield stress fluid and / or a complex fluid and / or a viscoelastic fluid as previously described for the extruded fluid 1.

[0061] By discontinuous extrusion, it is understood that the flow rate Q of extruded fluid 1 is not constant during the extrusion of each droplet 4. In particular, the flow rate of extruded fluid 1 varies temporally (preferably oscillates, with an oscillation (preferably periodic) per extrusion of droplet 4) for each droplet between: - a maximum flow rate, and - a minimum flow rate.

[0062] Preferably, the minimum flow rate is less than or equal to 50%, preferably less than or equal to 20%, of the maximum flow rate. This minimum flow rate may be zero.

[0063] Preferably, the extruded fluid flow rate 1 is periodic with an extrusion period corresponding to the extrusion of a single droplet 4.

[0064] Preferably, each variation of the flow rate Q of the extruded fluid 1:

[0065] - between the maximum flow rate and the minimum flow rate, and

[0066] - between the minimum flow rate and the maximum flow rate,

[0067] is rapid, that is to say, preferably lasting less than 10% of the total extrusion time (i.e., the oscillation or extrusion period in the periodic case) of each drop 4 and / or has a duration of less than 1 second, preferably less than 0.5 seconds. This preferably results in a variation of the extrusion flow rate Q in notches.

[0068] The flow rate Q is controlled by at least one controllable valve 9 located upstream of the nozzle outlet 7 (typically by one valve 9 per fluid or liquid if the fluid 1 is a co-extrusion of several fluids or liquids).

[0069] The extruded droplet 4 comprises the fluid core 41 without the membrane 51.

[0070] In the first embodiment, the outlet fluid 2 comprises or consists of gas, and is preferably air.

[0071] The extruded droplet 4 in the fluid 2 falls, after passing through the fluid 2, into a liquid bath 8 (which can more generally be a "simple" liquid bath, and / or a non-Newtonian fluid, and / or a yield stress fluid and / or a complex fluid and / or a viscoelastic fluid, as previously described for the extruded fluid 1).

[0072] The liquid bath 8 preferably comprises an aqueous solution.

[0073] Thus, [Fig.2] relates to the implementation of the first embodiment (with nozzle 7 and grid 6) in a discontinuous extrusion mode to form capsules 5 with a fluid core 41 and a membrane 51 of gel or hydrogel once the drops 4 have been received in a liquid bath 8.

[0074] We note that:

[0075] - in the case of part a) of [Fig.2] corresponding to a first variant In the first embodiment 10, the extruded droplet 4 comprises a polymer solution and the liquid bath 8 comprises means (for example, a gelling or crosslinking agent, or means for heating the bath 8, or means for cooling the bath 8, or means for maintaining the bath 8 at a gelling or crosslinking temperature) arranged for gelling or crosslinking the polymer; thus, typically, the polymer that can be gelled or crosslinked is solubilized in the extruded fluid 1 and the bath 8 contains a gelling or crosslinking agent, or

[0076] - in the case of part b) of [Fig.2] corresponding to a second variant of the first embodiment 10, the liquid bath 8 comprises a polymer solution and the extruded droplet 4 comprises an agent arranged to gel or crosslink the polymer; thus typically the gelling or crosslinking agent is solubilized in the extruded fluid 1 and the bath 8 contains the polymer which can be gelled or crosslinked.

[0077] so that the membrane takes the form of a polymer hydrogel.

[0078] The table below gives examples of polymers, preferably natural, and of gelling or crosslinking agents or means usable within the framework of the present invention: General family of polymer and particular example of polymer General family of gelling or crosslinking agents or means and particular example of gelling or crosslinking agents or means adapted to the particular example of polymer Anionic polysaccharide: e.g. alginate Multivalent cation, e.g. Ca2+, or a cationic polyelectrolyte, e.g. chitosan Anionic polysaccharide: e.g. carrageenan Temperature change (lowering), preferably in the presence of a cation, e.g. K+ Cationic polysaccharide: e.g. chitosan Cation, e.g. citrate, or an anionic polyelectrolyte, e.g. alginate Non-ionic polysaccharide: e.g. agarose Temperature change (lowering)

[0079] The polymer used in the context of the invention may be:

[0080] - a polysaccharide or, more generally, a bio-based polymer, biodegradable, or a biopolymer, particularly for applications in the food industry.

[0081] - a synthetic or hybrid polymer, particularly for other applications

[0082] Any other type of polymer and gelling or crosslinking agent or means known and conceivable by a person skilled in the art is conceivable for the implementation of the present invention.

[0083] Thus, for example, in addition to the examples given in the table above, crosslinking using ultraviolet radiation can be considered as a means of gelation or crosslinking within the framework of the present invention, for example with a synthetic polymer and / or with a natural polymer functionalized using a chemical group necessary for crosslinking.

[0084] For example, the first embodiment of the process according to the invention can extradite, in air 2, the following fluid 1: - sodium alginate solution, viscosity q=1.4 Pa.s, surface tension y=70nN / m, drop volume Vg=5ml, D=20 mm, di=1mm, d2=0.35mm (the solidifying bath 8 is then a 100m calcium chloride solution, viscosity Hb=103 Pa.s), or - liquid shampoo with a concentration of 100M of calcium chloride, viscosity h=5.9 Pa.s surface tension y=30nN / m drop volume Vg=5ml D=20 mm di=1mm d2=0.35mm (bath 8 is then a sodium alginate solution, viscosity Hb=0.15 Pa.s).

[0085] Fig. 3 illustrates possible grid configurations used in the first embodiment 10 of the process according to the invention.

[0086] The density of the fluid 1 of the extruded droplet 4 is greater than the density P^ of the outlet fluid 2.

[0087] In the case where the droplet 4 or extruded fluid 1 comprises several unmixed fluids or liquids (for example in the case of co-extrusion), the density P is:

[0088] - preferably the density of the densest phase (preferably liquid) of droplet 4 in contact with fluid 2 at the nozzle outlet 7,

[0089] - otherwise the density of the densest phase (preferably liquid) of the drop 4.

[0090] In the case where the outlet fluid 2 comprises several unmixed fluids or liquids (for example in the case of an emulsion), the density P^ is:

[0091] - preferably the density of the least dense phase of the fluid 2 in contact of droplet 4, currently being formed at the nozzle outlet 7,

[0092] - otherwise the density of the least dense phase of fluid 2.

[0093] We denote D the diameter or the largest dimension of the outlet orifice, occupied by the grid 6, of the nozzle 7 through which the drop 4 is formed in the outlet fluid 2.

[0094] D is preferably greater than 10 mm.

[0095] The size D imposes a size of the drop, so D is chosen according to the desired volume V of the drop 4 and therefore of the capsule 5 (with typically a volume V of drop 4 equal to y — £)3).

[0096] The grid 6 comprises only holes or fluid passages 1 whose largest dimension di (perpendicular to the direction of fluid flow through these holes and / or parallel to the outlet surface of the grid 6 towards the outlet fluid) is less than z / y \1 / 2 (or even in some cases less than 4) with the gravitational constant, the volumetric mass of the fluid 1 of the extruded droplet 4, ^2 the density of the outlet fluid 2, the surface or interfacial tension between the fluid 1 of the extruded droplet 4 and the outlet fluid 2.

[0097] di is preferably greater than 0.5 mm, preferably 1 mm.

[0098] D is greater than ~ 1 — y 1 122

[0099] D is greater than twice dH, preferably greater than 3 or 4 times dH

[0100] For an aqueous extruded solution 1 whose density is close to that of water, which is extruded into air as the outlet fluid 2 through a horizontal grid 6, with a surface tension reduced to 30 mN / m (in the presence of surfactants), the critical size of di is 5.5 mm, without surfactants, for a surface tension of water equal to 72 mN / m at 20°C, the critical size of di is equal to 8.5 mm.

[0101] Thus the grid 6 typically comprises only holes or fluid passages 1 whose largest dimension di (visible from the outlet fluid 2) is less than 8 mm, preferably less than 5 mm.

[0102] The grid 6 may include other holes of other dimensions d3 less than dh

[0103] The grid 6 comprises only holes or fluid passages 1 whose gap (visible from outlet fluid 2) d2, d4 between these holes or passages is less than 2 mm, preferably less than 1 mm or 0.8 mm.

[0104] Preferably, the grid 6 is generally made of any rigid material that makes it possible to obtain a grid, typically made of plastic, bioplastic, wood, glass, metal (preferably stainless steel) or a material consisting of or coated with a polymer, for example a fluorinated polymer, for example such as polytetrafluoroethylene.

[0105] Figure 3 therefore shows different possible variants or configurations of grids 6 obtained from a solid plate of thickness h (defined as parallel to the extrusion direction of the droplet 4 through the grid 6) having: - holes (for example circular) arranged: • on its part a), according to a square grid, • on its part b), according to a hexagonal network, • on its part c), according to a double square grid of holes of two distinct diameters di and d3 in order to reduce the surface area occupied by the solid elements of grid 6, - on its part d) a square network (but which could also be hexagonal, double square, etc.) of square-shaped holes (but could also be rectangular, triangular, ...); here the transverse size di to be considered is the diagonal of the square holes with side d7 (or the maximum distance between two sides or edges in the case of holes of different shape).

[0106] Figure [Fig.3] also shows different shapes of the holes depending on the thickness of the plate: - hole of constant diameter on its part e), - a beveled hole on its part f) or g); the beveled shape (with Potentially, within the total thickness h of the grid 6, a residual thickness d6 (not beveled) is useful for limiting pressure losses (pressure variation) during the passage of fluid 1 through the holes. In this case, the formulas or considerations stated in this description take di, the largest dimension visible from the outlet fluid 2, of the holes or passages in the grid 6, into account. d5, the largest dimension visible from inside the nozzle 7, of the holes or passages in the grid 6, is not taken into consideration.

[0107] Figure 4 illustrates another possible configuration of grid 6 used in the first embodiment 10 of the process according to the invention, obtained from a braiding of wires (typically metallic) forming a network (typically square, but which could also be hexagonal, double square, etc.) of holes or passages (typically square with side d7) for the fluid 1. This grid 6 is similar to that of part d) of Figure 3, and the size di to be considered is the diagonal of the square holes with side d7. In a more complex variant than that illustrated in Figure 4, the spacing between the holes can have different values, in particular if different kinds of wires of different thicknesses are used, for example respectively for the horizontal mesh and for the vertical mesh.

[0108] In a coordinate system with three orthogonal axes x, y and z: - The upper left part of [Fig.4] illustrates this grid 6 perpendicular to the plane of [Fig.2], that is, in the plane of the x and y axes - the part on the right of [Fig.4] illustrates this grid 6 in the plane of y and z axes - the part at the bottom of [Fig.4] illustrates this grid 6 in the plane of x and z axes.

[0109] Figure 5 illustrates the stability limit as a function of the angle of inclination a of the grid 6 with respect to the horizontal (perpendicular to g) in the first embodiment of the method according to the invention, forming a network of holes.

[0110] The grid 6 is, with respect to the Earth's gravitational force or gravitational field î, horizontal or substantially horizontal at an angle less than or equal to ac (i.e., inclined at an angle “ with respect to the horizontal with a <ac ) , avec qui peut éventuellement être défini de sorte que lorsque smac - with $ the gravitational constant, P^ the density of fluid 1 of the extruded droplet 4, P^ the density of the outlet fluid 2, F the surface tension or interfacial between the fluid 1 of the extruded droplet 4 and the outlet fluid 2, D the outlet diameter of the extrusion nozzle 7, and di which is the largest dimension of the hole or passage of the grid 6 and which is preferably less than L.

[0111] a is in most variants preferably less than or equal to 45°, but it should be noted however that depending on the parameters used, the above formula can give a functional value of equal to 90°.

[0112] On [Fig. 5]: - Part a) of this figure illustrates the case a < - Part b) of this figure illustrates the case a > a«.

[0113] Figure 11 illustrates the improvement of the invention with respect to this angle a: a. In part a) of this figure, according to a comparative test to the invention, the extruded fluid 1 is water, the diameter D is 13 mm, and the valve 9 is closed (no flow expected). It is observed that the fluid 1 is stable up to Δt = 10⁻⁰, at which point the fluid 1 begins to flow on its own due to instability. b. In part b) according to the first embodiment of the invention in this figure, the extruded fluid 1 is water, the diameter D is 13 mm, the valve 9 is closed (no flow expected), and the polymer grid 6 (obtained by 3D printing) with circular holes in a hexagonal pattern and di = 4 mm and d2 = 0.5 mm is added. It is noted that the fluid 1 is stable up to -55°C, below which the fluid 1 begins to flow on its own due to instability.

[0114] Figure 6 illustrates the Froude number beyond which the extruded volume of droplet 4 is not deformed during the extrusion step of the first embodiment of the process according to the invention.

[0115] For the extrusion of each drop 4, the number of Froude pr — -.½....... is greater than Æ^ / 2 extruded droplet 4 has a distance, along the force at 0.5, preferably greater than 1, with Fr defined as the ratio of the average velocity L of the fluid 1 of the extruded droplet 4 at the outlet of the extrusion nozzle 7 and the falling velocity ^gj)'a of terrestrial gravitation (and below a center of the grid (preferably defined as the center of gravity of the surface delimiting the outlet of grid 6 where fluid 1 meets fluid 2) and in a simple case (a = 0° and grid 6 flat) any point of the outlet surface of grid 6), equal to the radius of the nozzle D / 2, and with 8 the gravitational constant.

[0116] By average speed, we mean r? _ where Q is the extrusion flow rate of fluid 1. nD1

[0117] In other words, the volume Vex of fluid 1 extruded from the nozzle 7 must be preferably equal to y = for a drop 4 to be extruded in a time , preferably equal to -212, short compared to the time of fall, _ / 2D \1 / 2 of the drop in fluid 2 defined as the time required for h “ V s J that fluid 1 moves a distance D when subjected only to the force of gravity. It is therefore preferable that

[0118] tex< tg and therefore pr _ .....U......> 2 ÆS7 3

[0119] On [Fig.6]: - Part a) of this figure illustrates the case Fr < 1, - Part b) of this figure illustrates the case Fr > 1.

[0120] Q is the critical flow rate beyond which the extruded volume 4 is not deformed or only slightly deformed, i.e., the width or lateral dimension l of the extruded fluid is greater than 0.6 D, preferably greater than 0.8 D, or substantially equal to D, during the extrusion step (part b of Figure 6) or the co-extrusion step (part c of Figure 6). This is an average flow rate Q established from the characteristic extrusion time and the extruded volume Vex, i.e., Q - vex / Vex. Below this critical flow rate, The fluid or liquid begins to flow under the effect of gravity when it is set in motion within the nozzle. An observable feature that distinguishes these two regimes is the lateral dimension 1 occupied by the fluid or liquid 1 at the nozzle outlet 7 (part a of Figure 6). According to experiments, the lateral dimension 1 becomes on the order of D when Fr is greater than 1.

[0121] The specific case of part c) of [Fig. 6] concerns the case of coextrusion within the framework of the first embodiment 10 of the process according to the invention. In this case, the extruded droplet 4 comprises:

[0122] - a hull fluid 42 (intended to become the membrane 51 following the reaction between the polymer and means for gelling or crosslinking the polymer) surrounding the fluid core 41; preferably this shell fluid 42 is obtained from a first part 71 of the nozzle 7 extruding a first fluid or liquid of the fluid 1 with a flow rate Qb and

[0123] - the fluid core 41; preferably this core 41 is derived from a second part 72 of the nozzle 7 extruding a second fluid or liquid from fluid 1 with a flow rate Q2,

[0124] the extrusion thus comprising a co-extrusion of the fluid core 41 and the shell fluid 42 (so that Q= Q1+Q2).

[0125] It is advantageous to leave a distance d8 of a few millimeters between the inner tube 72 which brings the core fluid and the grid 6, which can be advantageously chosen to be greater than 1 millimeter and / or less than 10 millimeters.

[0126] It should be noted that:

[0127] - in the case of part a) of [Fig. 2], in the case of a simple extrusion, without shell fluid 42 in the extruded droplet 4, the polymer solution is preferably found in the fluid 1 (in the single fluid or liquid of fluid 1) and therefore in the fluid core 41; the membrane 51 is formed only on a surface part of the core 41 following the reaction between the polymer of the core 41 and the means for gelling or crosslinking the polymer of the bath 8

[0128] - In the case of a coextrusion, similar to Figure 6c, adapted to the variant in part a) of [Fig. 2], the polymer solution is preferably found in the shell fluid 42, preferably only in the shell fluid 42 and / or not in the core fluid 41; the membrane 51 is formed only in the shell 42 following the reaction between the polymer of the shell 42 and the means for gelling or crosslinking the polymer of the bath 8; in this case, there is typically, in the fluid 1, a fluid or liquid extruded for the core 41 and which is preferably free of polymer and gelling or crosslinking agent, and a fluid or liquid extruded for the shell 42 and which includes the polymer

[0129] - in the case of part b) of [Fig. 2], in the case of a simple extrusion, without shell fluid 42 in the extruded droplet 4, the gelling or crosslinking agent is preferably found in the fluid 1 (in the single fluid or liquid of fluid 1) and therefore in the fluid core 41; the membrane 51 is formed only on a surface part of the core 41 following the reaction between the gelling or crosslinking agent of the core 41 and the polymer of the bath 8

[0130] -in the case of a coextrusion, similar to Figure 6c, adapted to the variant of part b) of [Fig.2], the gelling or crosslinking agent is preferably found in the shell fluid 42, preferably only in the shell fluid 42 and / or not in the core fluid 41; the membrane 51 is formed only in the shell 42 following the reaction between the gelling or crosslinking agent of the shell 42 and the polymer of the bath 8; in this case there is typically, in the fluid 1, a fluid or liquid extruded for the core 41 and which is preferably devoid of polymer and gelling or crosslinking agent, and a fluid or liquid extruded for the shell 42 and which includes the gelling or crosslinking agent.

[0131] so that the membrane 51 takes the form of a polymer hydrogel by reaction in the polymer and means for gelling or crosslinking the polymer.

[0132] The variants with coextrusion therefore have the advantage of allowing a purer core 41 or one with fewer additives, in particular devoid of each member of the pair formed by the polymer and the gelling or crosslinking agent, which is particularly advantageous in the food or cosmetics industries.

[0133] Thus, a variant (with nozzle 7 and grid 6) is provided with a discontinuous co-extrusion method for forming capsules 5 with a fluid core 41 and a membrane 51 of gel and / or hydrogel once the drops 4 (or double drops 4, since they comprise two layers 41, 42) have been received in the liquid bath 8. Here, the polymer that can be gelled or crosslinked is, for example, contained in the fluid 42 composing the fluid or liquid envelope of the double drop 4, and the bath 8 contains the gelling or crosslinking agent. It should be noted that the solution of certain polymers, such as agarose (heteropolysaccharides), becomes a gel when the temperature is lowered, below 8°C–42°C for agarose, depending on the species of red algae from which it is extracted. In this case, the gelling or crosslinking bath 8 can be maintained at a lower temperature than that of the sol-gel transition of the agarose solution, this temperature maintenance serving as a means of gelling or crosslinking.

[0134] Figure 7 illustrates a second embodiment of the method according to the invention.

[0135] In this second embodiment of the process according to the invention, which will only be described for its differences from the first embodiment previously described, and which, like the first embodiment, is compatible with both simple extrusion and co-extrusion, the outlet fluid 2 comprises or consists of a liquid.

[0136] Preferably, the outlet fluid 2 comprises an oil. This oil is less dense than the aqueous solution(s) included in the fluid 1 and therefore in the droplet 4.

[0137] Thus, preferably: - the extruded droplet 4 comprises a polymer solution and the outlet fluid 2 comprises arranged means for gelling or crosslinking the polymer: • In the case of a simple extrusion, without shell fluid 42 in the extruded droplet 4, this polymer solution is preferably found in fluid 1 (in the single fluid or liquid of fluid 1) and therefore in the fluid core 41; the membrane 51 is formed only on a surface part of the core 41 following the reaction between the polymer of the core 41 and the means for gelling or crosslinking the polymer of the fluid 2 • In the case of coextrusion, this polymer solution is preferably found in the shell fluid 42, preferably only in the shell fluid 42 and / or not in the core fluid 41); the membrane 51 is formed only in the shell 42 following the reaction between the polymer of the shell 42 and the means for gelling or crosslinking the polymer in the fluid 2; in this case, fluid 1 typically contains a fluid or liquid extruded for the core 41, which is preferably free of polymer and gelling agent or crosslinking, and an extruded fluid or liquid for the shell 42 and which comprises the polymer

[0138] or - the outlet fluid 2 comprises a polymer solution and the extruded droplet 4 comprises an agent arranged as in the first embodiment for gelling or crosslinking the polymer: • In the case of a simple extrusion, without shell fluid 42 in the extruded droplet 4, this agent is preferably found in fluid 1 (in the single fluid or liquid of fluid 1) and therefore in the fluid core 41; the membrane 51 is formed only on a surface part of the core 41 following the reaction between the gelling or crosslinking agent of the core 41 and the polymer of the fluid 2 • In the case of coextrusion, this agent is preferably found in the shell fluid 42, preferably only in the shell fluid 42 and / or not in the core fluid 41; the membrane 51 is formed only in the shell 42 following the reaction between the gelling or crosslinking agent of the shell 42 and the polymer of the fluid 2; in this case, we typically have, in the fluid 1, a fluid or liquid extruded for the core 41 which is preferably devoid of polymer and gelling or crosslinking agent, and a fluid or liquid extruded for the shell 42 which includes the gelling or crosslinking agent

[0139] so that the membrane 51 takes the form of a polymer hydrogel by reaction in the polymer and means for gelling or crosslinking the polymer.

[0140] This gives us an implementation (with nozzle 7 + grid 6) in a discontinuous extrusion mode in an oil bath 8 having a lower density than the extruded fluid or liquid 1 and containing for example a chemical species that can initiate the gelation or crosslinking of the extruded fluid or liquid 1, and that can be deployed on a coextrusion system.

[0141] Figure 8 illustrates experimental data for the maximum lateral size normalized by the internal diameter D of the nozzle 7, obtained for different extrusion speeds of the fluid 1 and therefore of the Froude number Fr, with the outlet fluid 2 being air at 20°C and 1 atmosphere and: - A fluid 1 consisting of water, with a viscosity of 1 mPa.s, and - a fluid 1 consisting of a sodium alginate solution of a viscosity of 1200 mPa.s

[0142] and for two different grids:

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153] - Case of [Fig.8](a): a sieve conforming to [Fig.4] and with di=1 mm and d2 =0.35 mm, h= d2 and D = 20 mm; - Case of [Fig.8](b): a perforated plate with circular holes arranged in a hexagonal pattern conforming to part b of [Fig.3] and where di=1 mm and d2=1 mm and h = 2mm and D = 19.5 mm, Figures 9 and 10 illustrate the use of a cutting plate or blade 11, also called a cup 11, which can typically be rotated (around its axis of rotation 12) to cut the fluid or liquid filament connecting the drop 4 to the nozzle 7 in any of the embodiments described with reference to the previous figures. [Fig.9] is a profile view in the x and z axis plane. [Fig. 10] is a top view in the x and y axis plane. Figures 9a and 10a correspond to the same moment. Figures 9b and 10b correspond to the same moment. Figures 9c and 10c correspond to the same moment. Any embodiment of the process according to the invention may include cutting, by the cup 11, at least one filament of fluid or liquid 1 connecting the drop 4 to the nozzle 7. This can be achieved by rotating the cup 11 around a rotation axis 12. A horizontal translational movement of the cup 11 can also be considered. This cut is optional, as at least one filament will eventually break on its own. This cut can also be achieved, in variations, by other means such as a diaphragm or two cups arranged like scissors. In general, the simplest method for implementing the invention is as follows: If we consider that the extruded fluid and the outlet fluid are constraints arising from the capsule whose manufacture is desired, we start by choosing di greater than its lower limit (0.5 mm, preferably 1 mm) previously defined and less than its upper limit ( » _ / r \1 / 2 , preferably L and / or 10 mm, J preferably 5 mm) as previously defined, and Fr greater than its lower limit (0.5, preferably 1) as previously defined. Then, d2 is chosen to be as small as possible, not only less than its upper limit (2 mm, preferably 1 mm and preferably 0.8 mm) as previously defined, but preferably as small as the manufacturing of the grid allows.

[0154] These embodiments also relate to each capsule 5 obtained by the process described above, having a volume preferably of at least 0.2 ml and comprising: - a fluid heart 41 - a membrane 51 surrounding the fluid core 41.

[0155] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.

[0156] For example, coextrusion may include more than two co-extruded fluids or liquids and therefore droplets 4 of more than two fluid or liquid layers.

[0157] Of course, the various features, forms, variants, and embodiments of the invention can be combined with one another in various ways, provided they are not incompatible or mutually exclusive. In particular, all the variants and embodiments described above are combinable.

[0158] Bibliographical references

[0159] [1] WO202384233_Al,

[0160] [2] WO202384239_Al,

[0161] [3] WO2018172781_Al

[0162] [4] Yildirim, OE, Xu, Q., & Basaran, OA (2005). Analysis of the drop weight method. Physics of Fluids, 17(6).

[0163] [5] Guyon, E., Hulin, JP, Petit, L., & de Gennes, PG (2001). Hydrodynamics Physics. Les Ulis: EDP Sciences

[0164] [6] Sharp, DH (1984). An overview of Rayleigh-Taylor instability. Physics D: Nonlinear Phenomena, 3-18.

Claims

Demands

1. Method for manufacturing capsules (5), each capsule comprising: - a fluid core (41) - a membrane (51) surrounding the fluid core the method comprising, for the manufacture of each capsule, an extrusion of a droplet (4) through an extrusion nozzle (7) into an outlet fluid (2), said droplet comprising at least the fluid core, said nozzle being provided with a grid (6) at its outlet opening onto the outlet fluid the extrusions being carried out discontinuously between the different capsules.

2. The method according to claim 1, characterized in that the extruded droplet comprises the fluid core without the membrane.

3. The method according to claim 1, characterized in that the extruded droplet comprises the fluid core and a shell fluid (42) surrounding the fluid core, the extrusion comprising a coextrusion of the fluid core and the shell fluid.

4. A method according to claim 1 to 3, characterized in that the outlet fluid comprises or consists of gas, preferably air.

5. Method according to claim 4, characterized in that the drop extruded in the outlet fluid falls, after passing through the outlet fluid, into a bath (8).

6. Method according to claim 5, characterized in that the bath comprises an aqueous solution.

7. A method according to claim 4 or 5, characterized in that: - the extruded droplet comprises a polymer solution and the bath comprises an agent or means arranged for gelling or crosslinking the polymer, or - the bath comprises a polymer solution and the extruded droplet comprises an agent arranged for gelling or crosslinking the polymer.

8. A method according to any one of claims 1 to 3, characterized in that the outlet fluid comprises or consists of a liquid.

9. The method according to claim 8, characterized in that the outlet fluid comprises an oil.

10. A method according to claim 8 or 9, characterized in that: - the extradated droplet comprises a polymer solution and the output fluid comprises an agent or means arranged to gel or crosslink the polymer, or - the output fluid comprises a polymer solution and the extruded droplet comprises an agent arranged to gel or crosslink the polymer.

11. A method according to any one of the preceding claims, characterized in that a density (^1) of the fluid in the extruded drop is greater than a density of the outlet fluid.

12. A method according to any one of the preceding claims, characterized in that the grid comprises only holes or fluid passages whose largest dimension dl is less than: - 10 mm, preferably less than 5 mm, and / or - ttIc where. / r \1 / 2 with (g) the gravitational constant, (Pi) a density of the fluid of the extruded droplet, ( / ¾ a density of the outlet fluid, ? the surface or interfacial tension between the fluid of the extruded droplet and the outlet fluid.

13. A method according to any one of the preceding claims, characterized in that the grid comprises only holes or fluid passages whose spacing is less than 2 mm, preferably less than 1 mm and preferably less than 0.8 mm.

14. A method according to any one of the preceding claims, characterized in that the grid is made of plastic, bioplastic, wood, glass, metal, and / or a material coated with a fluorinated polymer.

15. A method according to any one of the preceding claims, characterized in that the grid is, with respect to the force of Earth's gravity, horizontal or substantially horizontal at an angle less than or equal to ac, with ac defined such that • „ _ 4y . with (a) the gravitational constant, a Sm«c - (PçP^D the density of the extruded droplet fluid, (p / p) a density of the outlet fluid, P the surface or interfacial tension between the extruded droplet fluid and the outlet fluid, D the extrusion nozzle outlet diameter, and dl which is the largest dimension of the hole or grid passage and which is less than lc.

16. A method according to any one of the preceding claims, characterized in that, for the extrusion of each drop, the Froude number _ ......V........is greater than 0.5, preferably greater than 1, with Fr being defined as the ratio of the average velocity U of the fluid of the extruded drop at the exit of the extrusion nozzle and the fall velocity of the extruded drop at a distance, along the force of Earth's gravitation and below a center of the grid, equal to the radius of the nozzle D / 2, and with the gravitational constant.

17. Capsule (5) obtained by the process according to any one of the preceding claims, comprising: - a fluid core (41) - a membrane (42) surrounding the fluid core.

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