Interconnector for electrochemical device comprising sealing grooves

Abstract

High temperature electrolyzer comprising interconnectors (4) forming seal retaining grooves (44, 46). Manufacturing and assembly methods relating thereto. Figure for abstract: Fig. 5

Description

Title of the invention: Interconnector for electrochemical device comprising sealing grooves Technical field

[0001] The present invention relates to the field of electrochemical devices and finds applications in particular in the sectors of the production of renewable energies, in particular dihydrogen.

[0002] The invention is of particular interest, in no way limiting, in solid oxide electrochemical devices, in particular high-temperature electrolysers. State of the art

[0003] The electrochemical devices known in the prior art generally comprise stacks of electrochemical cells which are connected to each other by interconnectors.

[0004] In a high temperature electrolyzer, the interconnectors are exposed for prolonged periods to high temperatures which are typically between 600°C and 850°C.

[0005] Sealing against fluids produced by such an electrolyzer is typically ensured by seals interposed between the interconnectors and the electrochemical cells.

[0006] Under the action of the thermal and mechanical stresses to which they are subjected, such sealing joints can deform and / or slide, creating permeable zones. Statement of the invention

[0007] The invention aims to improve the sealing of electrochemical devices known in the state of the prior art.

[0008] To this end, the invention relates to an interconnector for an electrochemical device, comprising a first surface and a second surface, at least one of the first surface and the second surface being intended to be arranged opposite an electrochemical cell, the interconnector comprising: - a central portion in which the first surface is configured to delimit first fluid channels and the second surface is configured to delimit second fluid channels, - a peripheral part intended to receive one or more sealing members.

[0009] According to the invention: - the first surface of the interconnector forms at least one first groove configured to receive at least one first of said sealing members, and / or - the second surface of the interconnector forms at least one second groove configured to receive at least one second of said sealing members.

[0010] Such grooves, also called "sealing grooves", make it possible to improve the positioning of the sealing members, also called "sealing joints", in particular by preventing them from slipping.

[0011] The invention thus makes it possible to improve the sealing of an electrochemical device.

[0012] In an embodiment in which the interconnector comprises said first groove, the first groove forms a closed circuit.

[0013] In an embodiment in which the interconnector comprises said second groove, the second groove forms a closed circuit.

[0014] Of course, when the interconnector comprises said first groove and said second groove, each of them can form a closed circuit.

[0015] In an embodiment in which the interconnector comprises said first groove, the latter extends parallel to an edge of the interconnector.

[0016] In an embodiment in which the interconnector comprises said second groove, the latter extends parallel to said edge of the interconnector.

[0017] Of course, when the interconnector comprises said first groove and said second groove, each of which may extend parallel to said edge of the interconnector.

[0018] In an embodiment in which the interconnector comprises said first groove and said second groove, these extend parallel to each other.

[0019] In one embodiment, the interconnector comprises one or more openings for receiving connecting elements of the electrochemical device.

[0020] In a non-limiting manner, said connecting elements may be rods or bars of a compression system of the electrochemical device.

[0021] For example, the openings may be circular orifices made in the interconnector.

[0022] The first surface and / or the second surface of the interconnector may form one or more third grooves extending respectively around said openings.

[0023] Such third grooves may be configured to receive one or more third of said sealing members.

[0024] In one embodiment, the interconnector comprises one or more plates forming said first surface and said second surface.

[0025] In one variant, the interconnector comprises a single plate.

[0026] In another, non-limiting variant, the interconnector comprises three stacked plates.

[0027] In one embodiment, the interconnector - that is to say in particular the plates which it may include where appropriate - includes metallic material.

[0028] The material of the interconnector may in particular comprise a ferritic steel.

[0029] In one embodiment, the material of the interconnector comprises chromium or a chromium alloy.

[0030] Alternatively, the interconnector material may comprise nickel or a nickel alloy.

[0031] In one embodiment, the interconnector comprises a coating.

[0032] Such a coating may comprise a metallic material, preferably nickel or a nickel alloy.

[0033] Such a material of the interconnector and / or its possible coating makes it possible to increase the conductivity.

[0034] The invention also relates to an electrochemical device.

[0035] According to a first variant, the electrochemical device is a high-temperature electrolyser.

[0036] According to a second variant, the electrochemical device is a high-temperature fuel cell.

[0037] The device of the invention comprises at least one interconnector as defined above, one or more electrochemical cells and one or more sealing members.

[0038] The sealing member(s) are each received in a respective one of said first groove and said second groove of the interconnector so as to be clamped between the interconnector and a respective one of said electrochemical cells.

[0039] Of course, if the at least one interconnector comprises only said first groove, one or more first of said sealing members may be received in said first groove of the interconnector.

[0040] Similarly, if the at least one interconnector comprises only said second groove, one or more second of said sealing members may be received in said second groove of the interconnector.

[0041] When the at least one interconnector comprises said first groove and said second groove, one or more first of said sealing members may be received in said first groove of the interconnector and one or more second said sealing members can be received in said second groove of the interconnector.

[0042] In one embodiment, the sealing members comprise an inorganic material.

[0043] Preferably, the sealing members may comprise a material chosen from glasses, glass-ceramics, glasses reinforced with ceramic particles, and a mixture thereof.

[0044] By way of non-limiting examples, mention may be made of the vitroceramics marketed by the company Schott, in particular from the “G018” range.

[0045] The material of the sealing members preferably has a coefficient of thermal expansion ranging from approximately 5 x 106 K 1 to 15 x 106 K 1 (20°C, 800°C).

[0046] The material of the sealing members may have a glass transition temperature less than or equal to the operating temperature of the electrochemical device.

[0047] In one embodiment, the device comprises one or more reinforcing pieces.

[0048] Each of these reinforcing pieces may be configured to be sandwiched between one of the electrochemical cells and a portion of the interconnector forming a respective one of the first groove and the second groove.

[0049] For example, one of the reinforcing pieces may be sandwiched between one of the electrochemical cells and a part of the interconnector forming the first groove, so as to reinforce this part of the interconnector and thus improve the sealing provided by the sealing member(s) received in the first groove.

[0050] Similarly, another of said reinforcing pieces may be sandwiched between one of the electrochemical cells and a part of the interconnector forming the second groove, so as to reinforce this part of the interconnector and thus improve the sealing achieved by the sealing member(s) received in the second groove.

[0051] According to another aspect, the invention relates to a method of manufacturing an interconnector as defined above.

[0052] In one embodiment, this method comprises a step of shaping the interconnector so as to form the first groove and / or the second groove.

[0053] This shaping step is preferably carried out by hydroforming and / or stamping the interconnector.

[0054] According to another aspect, the invention relates to a method of assembling an electrochemical device as defined above.

[0055] In one embodiment, the assembly method comprises a step of arranging said sealing members on one or more surfaces of the at least one interconnector and / or one or more of said electrochemical cells.

[0056] In one embodiment, the assembly method comprises a step of expanding the sealing members thus arranged by heating.

[0057] Such an expansion step is preferably carried out so that a first of said sealing members extends into said first groove and / or a second of said sealing members extends into said second groove of the at least one interconnector.

[0058] In one embodiment, the assembly method comprises a tape casting step.

[0059] During such a casting step, a composition is preferably cast onto a support in the form of one or more strips.

[0060] In one embodiment, said arranging step comprises arranging one or more of these strips to form said sealing members.

[0061] Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows. Brief description of the figures

[0062] The following detailed description refers to the attached drawings in which: - [Fig.l] is a schematic view of an electrochemical device comprising stacks of electrochemical cells and interconnectors; - [Fig.2] is a schematic view of part of a stack of an electrochemical device, showing an electrochemical cell sandwiched between two interconnectors, the cell comprising two electrodes and an electrolyte disposed between the electrodes; - [Fig.3] is a schematic view of an interconnector comprising a plate having a central portion forming fluid channels and a peripheral portion forming fluid sealing grooves; - [Fig.4] is a schematic sectional view of part of an interconnector similar to that of [Fig.3]; - [Fig. 5] is a schematic sectional view of a part of a stack of an electrochemical device according to the invention, this part of the stack comprising six electrochemical cells, five interconnectors, as well as reinforcing parts and sealing joints arranged between the interconnectors and the cells.

[0063] Common references are used in the various figures to designate identical or similar elements. Detailed description of embodiments

[0064] Figures 1 to 5 include a reference frame defining orthogonal directions D1, D2 and D3.

[0065] An electrochemical device 1 according to the invention is shown in a simplified manner in [Fig.l].

[0066] In this non-limiting example, the device 1 is a solid oxide electrolyzer configured to produce dihydrogen by gas-phase electrolysis, i.e. a high-temperature electrolyzer.

[0067] As an indication, electrolysis can be carried out at a temperature between 700°C and 850°C.

[0068] In the simplified example of [Fig.l], the device 1 comprises two stacks 2 which each comprise electrochemical cells, in this case electrolysis cells, between which interconnectors are interposed.

[0069] In each of the stacks 2, the electrochemical cells and the interconnectors are stacked alternately in the direction D3 which is here vertical.

[0070] [Fig.2] schematically shows a part of a stack 2 including an electrochemical cell 3 and two interconnectors 4 which are stacked in the direction D3. The cells and the interconnectors of the stacks 2 of the device 1 of [Fig.l] can be configured in the manner described below with reference to [Fig.2].

[0071] In a manner known per se, the cell 3 comprises two electrodes 6 and 7, respectively forming an anode and a cathode, as well as an electrolyte 8 arranged between the electrodes 6 and 7. The cell 3 is configured to dissociate water molecules into dihydrogen and dioxygen by redox. To do this, water vapor 10 is introduced at the cathode 7 which ensures the electrochemical reduction reaction resulting in a production of dihydrogen 11 in gaseous form and superoxide ions 12. A potential difference is imposed between the anode 6 and the cathode 7, creating an electric field which causes a migration of the superoxide ions 12 from the cathode 7 to the anode 6 through the electrolyte 8. At the anode 6, the superoxide ions 12 are oxidized resulting in a production of dioxygen 13 in gaseous form.

[0072] The interconnector 4 arranged on the anode 6, that is to say the one located towards the bottom of [Fig. 2], comprises channels (not shown in [Fig. 2]), called “first channels”, which open opposite the anode 6 so as to evacuate the flow of dioxygen 13 thus produced. The interconnector 4 arranged on the cathode 7, that is to say the one located towards the top of [Fig. 2], comprises channels (not shown in [Fig. 2]), called “second channels”, which open opposite the cathode 7 so as to evacuate the flow of dihydrogen 11 thus produced. In this example, these different channels extend along the direction DL

[0073] Of course, the interconnector 4 arranged on the cathode 7 of the cell 3 of [Fig. 2] can also comprise first channels (not shown in [Fig. 2]) which open opposite the anode of another electrochemical cell (not shown in [Fig. 2]) of the stack 2, in order to evacuate a flow of dioxygen produced by this other cell. Similarly, the interconnector 4 arranged on the anode 6 of the cell 3 of [Fig. 2] can also comprise second channels (not shown in [Fig. 2]) which open opposite the cathode of another electrochemical cell (not shown in [Fig. 2]) of the stack 2, in order to evacuate a flow of dihydrogen produced by this other cell.

[0074] The invention relates more specifically to an interconnector 4 for such a stack 2.

[0075] Figures 3 and 4 illustrate a non-limiting embodiment of an interconnector 4 according to the invention.

[0076] In this example, the interconnector 4 is in the form of a plate or sheet having a first surface 21, which in this example is intended to come into contact with an anode of an electrochemical cell, and a second surface 22, opposite the surface 21 along D3, this second surface 22 being in this example intended to come into contact with a cathode of another electrochemical cell.

[0077] For example, the plate of the interconnector 4 can be made of chrome or a chrome alloy.

[0078] The plate forming the interconnector 4 of figures 3 and 4 has been shaped so as to have a central part 25 configured to channel fluids and a peripheral part 26, that is to say a part extending around the central part 25, configured to provide a fluid sealing function (see further below).

[0079] In this non-limiting example, the peripheral part 26 of the interconnector 4 comprises four fluidic openings 27, visible in [Fig.3].

[0080] The central part 25 of this interconnector 4 is corrugated, that is to say that it comprises an alternation, in this case along the direction D2, of concave and convex parts.

[0081] More precisely, with reference to [Fig. 4], the surfaces 21 and 22 of the central part 25 of the interconnector 4 each have an alternation of concave parts 21A / 22A and convex parts 21B / 22B, so that the concave parts 21A of the surface 21 correspond to the convex parts 22B of the surface 22 and, conversely, the convex parts 21B of the first surface 21 correspond to the concave parts 22A of the second surface 22.

[0082] In this example, the concave parts 21A / 22A of the first, respectively of the second, surface thus define hollows along D3.

[0083] With reference to [Fig. 4], the concave portions 21A of the interconnector 4 each form surface elements 21S, also called “bearing surfaces”, and the convex portions 22B of the interconnector 4 each form surface elements 22S, also called “bearing surfaces”. In a non-limiting manner, the bearing surfaces 21S and 22S are in this example planar and extend parallel to the directions DI and D2.

[0084] Still with reference to [Fig. 4], the peripheral part 26 of the interconnector 4 successively comprises, in this non-limiting example from the central part 25 to an edge 28 of the interconnector 4, a connecting part 101, two parts 102 and 103 called sealing parts and an end part 104 forming the edge 28 of the interconnector 4.

[0085] The sealing portion 102 comprises a central portion 102A and two lateral portions 102B and 102C. Similarly, the sealing portion 103 comprises a central portion 103A and two lateral portions 103B and 103C.

[0086] In this non-limiting example, parts of the surface 21 which are formed by the connecting part 101 and by the lateral portions 103B and 103C of the sealing part 103 extend in a first fictitious plane parallel to the directions D1 and D2 which passes through parts of the surface 21 formed by the convex parts 21B of the central part 25 of the interconnector 4. Parts of the surface 22 which are formed by the terminal part 104 and by the lateral portions 102B and 102C of the sealing part 102 extend in a second fictitious plane parallel to said first plane and passing through the bearing surfaces 22S of the central part 25 of the interconnector 4.

[0087] With reference to the sealing portion 102, the central portion 102A is offset along D3 relative to the lateral portions 102B and 102C, defining a groove 110 which has a bottom surface 102S corresponding to a part of the surface 22 formed by this central portion 102A. Laterally, the groove 110 is delimited by parts of the interconnector 4 connecting the central portion 102A respectively to the portions 102B and 102C of the sealing portion 102.

[0088] Similarly, the central portion 103A of the sealing part 103 is offset along D3 relative to the lateral portions 103B and 103C, defining a groove 112 which has a bottom surface 103S corresponding to a part of the surface 21 formed by this central portion 103A. Laterally, the groove 112 is delimited laterally by parts of the interconnector 4 connecting the central portion 103A respectively to the portions 103B and 103C of the sealing part 103.

[0089] With reference to Figures 3 and 4, each of the grooves 110 and 112 forms in this example a closed circuit extending around the central part 25 of the interconnector 4.

[0090] In this embodiment, each of the grooves 110 and 112 extends parallel to the edge 28 of the interconnector 4 which has a rounded rectangular geometry, the grooves 110 and 112 thus extending parallel to each other.

[0091] [Fig.5] shows a part of a stack 2 forming an electrochemical device according to the invention, such as that of [Fig.l], in an assembled configuration which allows this device to be put into service.

[0092] In the configuration of [Fig.5], the stack 2 is subjected to a pressing force of its different components which is exerted globally in the direction D3 and which can be exerted in a manner known per se by a conventional compression system (not shown) of the electrochemical device 1.

[0093] In this non-limiting example, the stack 2 of [Fig. 5] comprises electrochemical cells 3 as described above, interconnectors 4 similar to those of FIGS. 3 and 4, metal force transmission bars 30, reinforcing pieces 40 and 42, sealing members 44 and 46, also called “seals”, as well as grids forming so-called contact elements 50.

[0094] In the configuration of [Fig. 5] and with reference to figures 4 and 5, each of the bars 30 extends into a respective one of the concave parts 21A of the interconnectors 4 so as to come to bear on the one hand on a respective one of the bearing surfaces 21S and on the other hand on one of the electrochemical cells 3, in this example with the anode of this cell 3. Such bars 30, which are optional, make it possible to optimize the distribution of the mechanical loads in the stack 2.

[0095] The stack 2 thus forms fluid channels 60 delimited by the concave parts 22A of the interconnectors 4, the channels 60 corresponding to said second channels intended to convey dihydrogen, as well as fluid channels 62 delimited in this example by the convex parts 21B of the interconnectors 4 and laterally by the bars 30, the channels 62 corresponding to said first channels intended to convey dioxygen.

[0096] The fluidic sealing of the stack 2 is ensured by the sealing joints 44 and 46.

[0097] Still with reference to Figures 4 and 5, each of the sealing joints 44 is interposed between the surface 22 of a respective one of the interconnectors 4 and a respective one of the cells 3, so as to extend into the groove 110 formed by this interconnector 4.

[0098] More precisely, in this non-limiting example, each of the sealing joints 44 is thus in contact, on one side along D3, on a surface of a respective one of the cells 3, in this case on its cathode and, on the other side along D3, on the bottom surface 102S of the groove 110 of a respective one of the interconnectors 4 as well as on parts of the surface 22 forming the portions 102B and 102C of the corresponding sealing part 102.

[0099] In this example, the seals 44 thus make it possible to ensure the sealing of the stack 2 with respect to the flows of dihydrogen produced by the device.

[0100] Similarly, each of the sealing joints 46 is interposed between the surface 21 of a respective one of the interconnectors 4 and a respective one of the cells 3, so as to extend into the groove 112 formed by this interconnector 4 (see figures 4 and 5).

[0101] More precisely, in this non-limiting example, each of the sealing joints 46 is thus in contact, on one side along D3, on a surface of a respective one of the cells 3, in this case on its anode and, on the other side along D3, on the bottom surface 103S of the groove 112 of a respective one of the interconnectors 4 as well as on parts of the surface 21 forming the portions 103B and 103C of the corresponding sealing part 103.

[0102] In this example, the seals 46 thus make it possible to ensure the sealing of the stack 2 with respect to the flows of oxygen produced by the device.

[0103] In this embodiment, each of the reinforcing pieces 40 is interposed between a part of the surface 21 formed by the portion 102A of the sealing part 102 of a respective one of the interconnectors 4 and a respective one of the cells 3, in order to hold this interconnector 4 against the sealing gasket 44 received in the groove 110 formed by this sealing part 102.

[0104] The reinforcing pieces 40 thus make it possible to stiffen the interconnector 4 so as to optimize the sealing provided by the seals 44.

[0105] Similarly, each of the reinforcing pieces 42 is interposed between a part of the surface 22 formed by the portion 103A of the sealing part 103 of a respective one of the interconnectors 4 and a respective one of the cells 3, in order to hold this interconnector 4 against the sealing joint 46 received in the groove 112 formed by this sealing part 103.

[0106] The reinforcing pieces 42 thus make it possible to stiffen the interconnector 4 so as to optimize the sealing provided by the seals 46.

[0107] The grooves 110 and 112 of the interconnectors 4 make it possible to retain the seals 44 and 46 when the device 1 is in operation, in particular preventing them from sliding laterally.

[0108] In this non-limiting example, the sealing joints 44 and 46 comprise a vitroceramic glass from the “G018” range marketed by the company Schott.

[0109] To obtain an assembly as illustrated in [Fig.5], the sealing gaskets 44 and 46 can be arranged in the form of strips on the cells 3.

[0110] To do this, in a manner known per se, the composition forming the joints 44 and 46 can be placed in a casting tank, then cast onto a support, for example a polyester “Mylar” type support, so as to form strips. The composition is typically left to air dry to remove the solvents.

[0111] The strips thus obtained can be directly placed on the cells 3.

[0112] After arranging the joints 44 and 46 and stacking the cells 3 and the interconnectors 4, the stack 2 is heated so as to expand the seals 44 and 46 to make them penetrate into the grooves 110 and 112, according to the configuration illustrated in [Fig.5],

[0113] Many variations may be made to the foregoing description, particularly with respect to the geometry and / or material of the various components described above. For example, the seals 44 and 46 may comprise another type of glass and / or another material, such as glass reinforced with ceramic particles.

[0114] In a variant not shown of the embodiment of [Fig.5], each of the joints 44 may comprise a lateral part sandwiched between the cell 3 and the corresponding reinforcement piece 42. Similarly, each of the joints 46 may comprise a lateral part sandwiched between the cell 3 and the corresponding reinforcement piece 40.

[0115] In an embodiment not shown, the stack may be devoid of the reinforcing pieces 40 and / or 42 illustrated in [Fig.5], the geometry of the interconnectors can of course be adapted accordingly.

[0116] The interconnector of the invention may generally comprise one or more grooves configured to receive one or more seals on a first side of the interconnector intended to face an electrochemical cell and / or one or more other grooves configured to receive one or more other seals on a second side of the interconnector intended to face another electrochemical cell.

[0117] In particular, in one embodiment, the interconnector 4 of [Fig. 3] may comprise sealing grooves (not shown) around each of the openings 27, in addition to the grooves 110 and 112 illustrated in [Fig. 4], in order to optimize the sealing achieved by seals (not shown) arranged, for each of the openings 27, on each of the surfaces 21 and 22 of the interconnector 4. The preceding description applies by analogy to this embodiment.

[0118] The interconnector of the invention, in particular that of figures 3 and 4, can be manufactured from a plate which can have a thickness of between 0.2 mm and 5 mm. The grooves (in particular 110 and 112) and the concave and convex parts of the central part 25 of the interconnector 4 can be formed by stamping or hydroforming such a plate.

[0119] Of course, the interconnector of the invention may comprise an assembly of several plates and / or be shaped using any other technique.

[0120] For another example of a variant, the stack 2 may be devoid of the force transmission bars 30 illustrated in [Fig.5] and, more generally, the channels formed by the central part 25 of the interconnector 4 may have any other geometry and / or be provided with a gas-permeable material such as a foam.

[0121] More generally, the invention can be implemented to form an electrochemical device different from that described above, for example a high-temperature fuel cell.

Claims

Claims

1. Interconnector (4) for an electrochemical device (1), comprising a first surface (21) and a second surface (22), at least one of the first surface (21) and the second surface (22) being intended to be arranged opposite an electrochemical cell (3), the interconnector (4) comprising: a central portion (25) in which the first surface (21) is configured to delimit first fluid channels (62) and the second surface (22) is configured to delimit second fluid channels (60), a peripheral portion (26) intended to receive one or more sealing members (44, 46), characterized in that: the first surface (21) of the interconnector (4) forms at least one first groove (112) configured to receive at least one first of said sealing members (46),and / or the second surface (22) of the interconnector (4) forms at least one second groove (110) configured to receive at least one second of said sealing members (44).,

2. An interconnector (4) according to claim 1, wherein the first groove (112) and / or the second groove (110) each form a closed circuit and / or extend parallel to each other and / or to an edge (28) of the interconnector (4).

3. An interconnector (4) according to claim 1 or 2, comprising one or more openings (27) for receiving connecting elements of the electrochemical device (1), the first surface (21) and / or the second surface (22) of the interconnector (4) forming one or more third grooves extending respectively around said openings (27) and being configured to receive one or more third of said sealing members.

4. Interconnector (4) according to any one of claims 1 to 3, comprising one or more plates, preferably metallic, forming said first surface (21) and said second surface (22).

5. Electrochemical device (1), for example high temperature electrolyzer or high temperature fuel cell, comprising at least one interconnector (4) according to any one of claims 1 to 4, one or more electrochemical cells (3) and one or more sealing members (44, 46) which are each received in a respective one of said first groove (112) and said second groove (110) of the interconnector (4) so ​​as to be sandwiched between the interconnector (4) and a respective one of said electrochemical cells (3).

6. Device (1) according to claim 5, in which the sealing members (44, 46) comprise an inorganic material chosen from glasses, glass-ceramics, glasses reinforced by ceramic particles, and a mixture thereof.

7. Device (1) according to claim 5 or 6, comprising one or more reinforcing pieces (40, 42), each of these reinforcing pieces (40, 42) being configured to be sandwiched between one of the electrochemical cells (3) and a part (102, 103) of the interconnector (4) forming a respective one of the first groove (112) and the second groove (110).

8. A method of manufacturing an interconnector (4) according to any one of claims 1 to 4, comprising a step of shaping the interconnector (4), preferably by hydroforming and / or stamping, so as to form the first groove (112) and the second groove (110).

9. A method of assembling an electrochemical device (1) according to any one of claims 5 to 7, comprising: a step of arranging said sealing members (44, 46) on one or more surfaces of the at least one interconnector (4) and / or one or more of said electrochemical cells (3), a step of expanding the sealing members (44, 46) thus arranged by heating, so that a first of said sealing members (46) extends into said first groove (112) and a second of said sealing members (44) extends into said second groove (110) of the at least one interconnector (4).

10. A method according to claim 9, comprising a strip casting step in which a composition is cast onto a support in the form of one or more strips, said arranging step comprising arranging one or more of these strips to form said sealing members (44, 46).

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