Method and apparatus for producing composites made from multifilament fibers

Abstract

A process for the continuous manufacture of elongated composite elements comprising bundles (20) of multifilament fibers embedded in a composition based on a polymeric material, the steps of which are: - arranging the bundle of multifilament fibers in the form of a plurality of individual strands, each comprising a plurality of multifilament fibers, such that a first strand is located at the center of the bundle and the other strands are positioned around the first strand; - feeding an array of multifilament fibers in a forward direction; Including, The forward feeding step is: - degassing the array of fibers by the action of a vacuum; - impregnating the arrangement of fibers with the composition so as to obtain an impregnated strand; - passing the first impregnated strand through a first die which causes partial polymerization of the composition; - passing all strands through a final die to combine them into a single strand; - exposing the single strand to a radiation source to carry out addition polymerization so as to obtain a long composite element; The following should be imposed.

Description

[Technical Field]

[0001] The present invention relates to a process for the continuous manufacture of elongated composite materials produced by impregnating multifilament fibers with a polymerizable composition, and more particularly to a process for producing composites in single strand form, such as the GRC (glass-resin composite) type, comprising continuous unidirectional multifilament glass fibers embedded in a polymerizable resin. [Background technology]

[0002] EP 1 174 250 describes a process and installation for the continuous impregnation of very long fibers with resin to produce very long and elongated composite elements, the composites comprising reinforcing fibers embedded in a cured resin matrix. The process described comprises the steps of feeding a bundle of reinforcing fibers in a forward direction from a fiber storage reel, passing it through a vacuum enclosure and then through an impregnation chamber in which the fibers are impregnated with resin, followed by a step in which the impregnated fibers pass through a calibration mold after pre-stabilizing the shape of the prepreg by polymerization of at least a portion of the resin in the prepreg. Calibration molds of predetermined shape and predetermined dimensions are also present at the entrance to the vacuum enclosure and before the impregnation chamber. The installation comprises a pull roll for feeding the fibers in a forward direction from the fiber storage reel and a reel for receiving the prepreg.

[0003] Although functionally satisfactory, it has proven difficult to increase the diameter of composites produced on this equipment beyond a certain limit. Thus, there is a need to produce larger diameter composites.

[0004] One solution to this problem would be to subject the resin-impregnated fiber bundles obtained in the facilities for continuous fiber production of the above type to an oven in order to obtain polymerization in the center of the fiber bundle, but such a process would be time- and energy-consuming.

[0005] European Publication No. 1506085 and US Publication No. 2015 / 318080 describe different processes for producing composite materials in cord form.

[0006] Another solution to this problem is described in EP 0290849. According to this document, a resin-impregnated fiber bundle is produced by pultrusion, by passing the fiber bundle through a bath of resin and then through a mold and exposing it to ultraviolet light. Polymerization of the fiber bundle occurs gradually from the outside to the inside of the fiber bundle as the fiber bundle travels the length of a transparent mold or through a liquid medium separated by two leak-tight nozzles while being exposed to ultraviolet light. While this does allow for better polymerization in the center of the fiber bundle, the process is very slow and not suitable for the production speeds of industrial processes. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent No. 1174250 [Patent Document 2] European Publication No. 1506085 [Patent Document 3] US Publication No. 2015 / 318080 [Patent Document 4] European Patent No. 0290849 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to overcome the drawbacks of the above-mentioned documents and to provide an original solution for a process and a device for polymerizing multifilament fibers for installations for the continuous production of elongated composite materials, making it possible to obtain composites with large cross-section dimensions at high productivity. [Means for solving the problem]

[0009] This object is achieved by the invention by providing a process for the continuous production of elongated composite elements comprising a bundle of multifilament fibres embedded in a composition based on polymeric material, the steps of which are: - arranging the bundle of multifilament fibers in the form of a plurality of individual strands, each comprising a plurality of multifilament fibers, such that a first strand is located at the center of the bundle and the other strands are positioned around the first strand; - feeding an array of multifilament fibers in a forward direction; Including, The forward feeding step is: - degassing the array of multifilament fibers by the action of a vacuum; - impregnating an array of multifilament fibers with the composition to obtain an impregnated strand; - passing the first impregnated strand through a first die which causes partial polymerization of the composition; - passing all strands through a final die to combine them into a single strand; - exposing the single strands to a radiation source to carry out addition polymerization so as to obtain long composite elements; The following should be imposed.

[0010] An elongated composite element comprising a bundle of multifilament fibers embedded in a composition based on a polymeric substance means a very long composite element produced continuously from one or more reels of multifilament fibers feeding to form a bundle, the bundle being fed so as to successively impregnate the fibers with a polymeric organic substance and polymerize the substance as it passes through.

[0011] In other words, the process of the present invention involves assembling a bundle to be impregnated from several strands of multifilament fibers and carrying out selective and sequential polymerization of the different strands, with the polymerization of the impregnated multifilament fibers starting at the center of the bundle and completing at its periphery. This allows obtaining elongated composite elements based on multifilament fibers, the shape and dimensions of which are well controlled and whose mechanical properties are uniform over their entire length. Preferably, an addition polymerization results in the final polymerization of the composition.

[0012] The process of the invention therefore makes it possible to obtain composite elements with large cross-section dimensions, and this is done at high production speeds. By way of example, in the case of GRC (glass-resin composite) composites, it is possible to obtain cross-sections with a diameter of between about 10 and 30 mm at speeds of about 50 m / min using the process of the invention.

[0013] The process of the invention can also be used to manufacture composite elements with cross sections between 0.5 and 10 mm in diameter, with the aim of achieving a higher geometric accuracy than the same cross sections manufactured in one operation according to the process described in the above-mentioned EP 1 174 250.

[0014] It has therefore been found that by creating a partially polymerized core in the center of the bundle, the subsequent layers adhere better to this core, thereby making it possible to obtain a final composite with a well-controlled cross-section and a high production rate. This is because, during tests carried out in the laboratory, it was found that the resin no longer flows through the impregnated fibers of the bundle under the influence of gravity, as in conventional equipment; in fact, the different successive layers of fiber adhere well to the pre-polymerized core until the composite passes through the final mold, where its shape finally stabilizes after final polymerization. By way of example, in the case of GRC (glass-resin composite) composites, the process of the present invention makes it possible to obtain large (or continuous) lengths of elongated composite elements with a circular cross-section and a diameter between 0.5 and 2.5 mm, with a dimensional tolerance of 0.05 mm, and at speeds between 100 and 200 m / min.

[0015] Partially polymerized or prepolymerized core is understood to mean a composite core of multifilament fibers embedded in a composition based on polymerizable substances, the degree of polymerization of which is terminated when it reaches a maximum of a few percent of complete polymerization, typically between 0.5 and 5%. The degree of polymerization can be evaluated using a DSC (differential scanning calorimetry) type instrument.

[0016] Full polymerization of the composite is achieved when the degree of polymerization of the resin approaches 100%, typically greater than 95%, when the composite is measured with a DSC type device.

[0017] The strands are aligned and passed successively through at least the first and last dies in such a way that they converge, starting from the impregnation chamber at the exit of which the alignment is most expanded, towards the last die, where they contract to form a single strand. This makes it possible to divide the bundle into multiple strands at the beginning of the process and pass at least the central strand through a die capable of acting on the center of the bundle. Thus, a stepwise polymerization of the bundle is carried out, with the first polymerization stage taking place in the center of the bundle and the last stage aimed at subjecting the bundle to addition polymerization when all the strands are combined into a final single strand.

[0018] The array of multifilament fibers can comprise a central strand, a plurality of intermediate strands positioned to form at least one intermediate layer surrounding the central strand, and at least one outer layer of peripheral strands, where each intermediate layer of intermediate strands passes through an intermediate mold that partially polymerizes the composition.

[0019] This allows for multi-stage polymerization, resulting in the creation of composites with larger cross sections.

[0020] The cross section of the composite element can be circular, however, this cross section can also have any other shape such as polygonal, oval, elliptical, tubular, etc., in particular by appropriate selection of the shape of the mold.

[0021] A multifilament fibre is understood to mean a fibre comprising a plurality of elementary fibres arranged side by side to form a bundle, said elementary fibres being unidirectional and substantially parallel to one another.

[0022] The multifilament fibers may be selected from the group consisting of glass fibers, carbon fibers, silica fibers, ceramic fibers and mixtures of such fibers, preferably from the group consisting of glass fibers, carbon fibers and mixtures of such fibers, and even more preferentially the multifilament fibers may be glass fibers, which are used to manufacture elongated composites produced by impregnating the multifilament fibers with a polymerizable composition.

[0023] The polymerizable material can be thermosetting, preferably thermally crosslinkable, and even more preferentially vinyl ester-based. Polymerizable material is understood to mean a material containing more than 50%, preferably more than 75%, and even more preferentially more than 90% organic material by weight. Thus, the material can be, for example, a thermally polymerizable polymeric material based on unsaturated polyesters, polyepoxides, phenol derivatives, or aminoplasts. Preferably, the polymerizable material is crosslinked. It is, for example, a resin that can be crosslinked by ionizing radiation, and the final polymerization can be easily induced and controlled by ionizing treatment, for example, of the ultraviolet or ultraviolet-visible type. As crosslinkable polymerizable materials, polyester resins (based on unsaturated polyesters) and even more preferentially vinyl ester resins are used.

[0024] The object of the present invention is achieved by a device for the continuous production of elongated composite elements comprising bundles of multifilament fibers embedded in a composition based on polymerizable organic material, said device comprising means capable of producing an arrangement of bundles of multifilament fibers in the form of a plurality of individual strands, each strand comprising a plurality of fibers, with the initial strand being located at the center of the bundle, means for degassing the arrangement, means for impregnating the arrangement with a composition based on polymerizable material, a first mold capable of receiving the initial strands for their partial polymerization, at least one final mold capable of receiving all the strands to form single strands, and means for polymerizing the single strands by means of an irradiation device to obtain elongated composite elements.

[0025] The device according to the invention may comprise at least one intermediate mould located between the initial mould and the final mould.

[0026] The first and intermediate dies may be provided in their central portions with an annular ultraviolet lamp containing guide tubes for the strands.

[0027] The annular lamp may comprise a circular plate for supporting a plurality of light-emitting diodes (LEDs) with a central opening through which a guide tube passes, a reflector capable of directing radiation emitted by the light-emitting diodes (LEDs) towards the exit of the guide tube, means for cooling the lamp, and means for supplying power to the lamp.

[0028] The cooling means can include a water-cooling circuit and / or a device for generating an air or nitrogen flow. The water-cooling circuit ensures fast and efficient cooling of the lamp. Cooling with air or nitrogen is easy to implement, since it does not require sealing elements, as is the case with water-cooling circuits. In addition, the presence of nitrogen promotes the surface polymerization of organic substances surrounding the fibers, since the presence of atmospheric oxygen acts as a polymerization inhibitor.

[0029] The internal cross section of each guide tube can gradually increase from upstream to downstream between the first and last dies, allowing the various layers of impregnated fiber surrounding the central strand to be gradually layered starting from the center of the bundle.

[0030] A better understanding of the present invention can be obtained by continuing the description based on the following figures. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a perspective view showing components of a device for manufacturing elongated composite elements according to a preferred embodiment of the present invention; FIG. [Figure 2] FIG. 10 is a perspective view showing the main components of another embodiment of the device of the present invention. [Figure 3] FIG. 3 is an enlarged cross-sectional view of feature A in FIG. 2. [Figure 4] FIG. 2 is an enlarged perspective view of the device of FIG. 1. [Figure 5] FIG. 5 is an enlarged view of the right side of the device in FIG. 4. [Figure 6] 1 is a cross-sectional view of a mold-formed portion of a device of the present invention; [Figure 7] 7 is an enlarged perspective view of a component forming part of the cooling circuit of a lamp forming part of the mold of FIG. 6; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0032] In the various figures, identical or similar elements have the same reference numbers and therefore their description will not be repeated systematically.

[0033] FIG. 1 shows a schematic diagram of a device 1 for producing very long and elongated composite elements. In the illustrated example, the composite is a GRC single strand comprising a glass filament embedded in a thermosetting resin. The single strand can have any known shape, for example, a cylindrical single strand with a large diameter, for example, 10 to 30 mm, and therefore a circular cross section. The device of the invention also allows the production of single strands with rectangular, oval, or other cross sections. The glass filaments are present in the form of essentially unidirectional multifilament fibers, each formed from a plurality of single glass filaments, each having an average diameter of approximately 5 to 30 μm. The resin being of the thermosetting or crosslinkable type is understood to mean that the resin is polymerizable or curable (photocurable and / or thermosetting) by virtue of being based on a thermosetting polymer. The glass transition temperature Tg of the resin is preferably higher than 160°C, more preferentially higher than 170°C, and in particular higher than 180°C.

[0034] In Figure 1, a bundle 20 of multifilament fibers entering the device 1 is observed, this bundle being represented diagrammatically in other figures by arrow E, the direction of the arrow indicating the direction of advance of the bundle relative to the device 1, which itself is fixed. The bundle 20 enters the vacuum chamber 2 through the inlet plate 4 in the form of multiple strands of multifilament fibers successively unwound from different reels 9 of the supply device 8. Generally, the fibers are delivered in roving form, i.e. as a group of fibers wound parallel to one another on the reels and identified by their text code. The bundle originating from the supply device 8 passes through the device 1 by advancing in the direction of arrow E, driven by a drive device located at the outlet of the device 1 (which, as will be explained later, will be understood to be in fact further in the direction of arrow S after the outlet of the irradiation device 50). The drive device (not shown) is, for example, of the type comprising an electrically driven traction drum that makes it possible to wind the composite element on its axis, or of the type comprising two electrically driven drums facing each other and spaced apart by a distance at least equal to the thickness of the composite element, which rotate in opposite directions to carry the composite element in translation by friction through the space located between the two drums. The device 1 comprises, in succession, a vacuum chamber 2, an impregnation chamber 3, two molds 10a and 10b called polymerization molds, a final mold 10f called calibration mold through which the finally obtained single strand 20f passes, and an irradiation device 50 for the final strand. The irradiation device 50 is understood to mean an ultraviolet and / or infrared device that performs an additional, preferably final, polymerization of the single strand leaving the final mold 10f.

[0035] In Figure 2, the main components of a device 1 according to another embodiment of the invention can be seen, comprising a vacuum chamber 2, an impregnation chamber 3, and several molds 10a to 10e, called polymerization molds, arranged in succession. A final mold 10f, called the calibration mold, and an irradiation device 50, positioned before the outlet of the device, can also be seen in Figure 4. The vacuum chamber 2 is axially separated by a rigid inlet plate 4 with through-holes and a rigid separator plate 5, also with through-holes axially opposite the through-holes in plate 4. Fibers, separated into multiple strands, are introduced into the vacuum chamber by passing them through various orifices in plate 4 and exit the vacuum chamber through orifices in plate 5, so that the strands travel from one plate to the other in a straight, parallel path, parallel to each other but parallel to the longitudinal axis X-X' of the device. The vacuum chamber is connected to a vacuum pump (not shown), which maintains a pressure level of approximately 0.1 bar in the vacuum chamber 2, despite the fibers passing through openings with a diameter larger than that of the strands. The impregnation chamber 3 is a sealed enclosure bounded by an intermediate plate 5 and a rigid outlet plate 6, and also has through-holes 7 located axially opposite the through-holes in the intermediate plate 5. The number of orifices 7 corresponds to the number of strands constituting the bundle 20. The impregnation chamber is supplied with resin originating from an external tank (not shown) through an inlet pipe (not shown) at the top, and also has a resin discharge pipe (not shown) at the bottom. Since the impregnation chamber 3 is completely filled with resin, the fibers leaving the vacuum chamber 2 pass through it following straight, parallel paths and are completely impregnated with resin.

[0036] Naturally, before operating the device 1 of the invention, it is necessary to pass all the strands of the bundle to be impregnated, starting from the storage reel 9, passing through the orifices of the plates 4, 5 and 6, past all the dies and irradiation devices 50, up to the drive means that ensure tensioning of all the strands of the bundle according to the pre-established arrangement of the multifilament fibres.

[0037] By way of example, if it is desired to obtain a cylindrical composite element with an outer diameter of 19 mm using the device shown in Figures 1, 4 and 5, an arrangement of about 80 elementary bundles of multifilament fibres is used, each of these 80 elementary bundles arriving into the device from a reel 9 of 4800 Tex roving. The arrangement of the 80 elementary bundles is made as follows: a central strand having a diameter of 5.6 mm, which is itself composed of an assembly of 8 elementary bundles of multifilament fibers derived from 8 reels of 4800 Tex; and two additional rows concentric with the first strand, each having a radial thickness of approximately 3 mm and each row comprising a number of concentric strands, the first consisting of 3 strands of 8 elementary bundles derived from 8 reels of 4800 Tex, and the second consisting of 6 strands of 8 elementary bundles derived from 8 reels of 4800 Tex, the whole obviously amounting to 8 + 3 × 8 + 6 × 8 = 80 reels of 4800 Tex.

[0038] Downstream of the impregnation chamber 3 are the polymerization molds 10a to 10e and the final calibration mold 10f, all positioned along one and the same axis, the longitudinal axis X-X' of the device. The bundle 20 is composed of several strands originating from the reel 9, forming an array of strands intended to pass successively through the various molds of the device. The array of strands is organized so that a central strand passes through the first mold 10a, positioned substantially on the axis of the device, while the various intermediate strands are arranged in successive rows around the central strand, coaxial with its axis, gradually converging as they pass through the molds 10b to 10e until all strands are joined, passing through the final mold 10f (Figure 4) to form a single strand 20f.

[0039] FIG. 4 shows a preferred embodiment of the device, comprising an initial mold 10a, an intermediate mold 10b, and a final calibration mold 10f. Referring to FIG. 5, it can be better seen that the bundle of multifilament fibers 20 comprises a central strand 20a and peripheral strands positioned concentrically therewith. The central strand 20a is intended to pass through the initial mold 10a, which ensures its partial polymerization. The strand emerging from it and the peripheral strands 20ae pass together through the intermediate mold 10b, which ensures partial polymerization of the resulting new strand 20b. The strand 20b emerging from the intermediate mold 10b and the remaining peripheral strands 20be pass together through the calibration mold 10f, which shapes them to form the final strand, after which the final polymerization of the final strand 20f takes place in the irradiation device 50. The calibration mold 10f is a tube with a clearly defined shape and dimensions. Alternatively, the calibration mold is of the polymerization mold type.

[0040] The structure of the polymerization mold 10a will be described with reference to Figures 3 and 6. This mold has an elongated shape with a longitudinal axis A-A' and includes an annular lamp 30 and a guide tube 40 for the fiber strands entering the mold. The lamp and guide tube are held together in a mold body 45 in two parts 45a, 45b with fins 46 for attachment to the device 1. At its outlet end, the mold body is extended by a tube 41 that guides the bundles exiting the mold toward the next mold. The annular lamp 30 is an assembly comprising several LEDs 31 with ultraviolet light, connected to each other via a printed circuit on a common support 32 of annular shape centered on the axis A-A'. The annular lamp 30 includes a reflector 33 capable of directing the radiation emitted by the LEDs toward the outlet of the guide tube 40. Exemplarily, the annular lamp 30 includes several high-power LEDs emitting light at wavelengths between 365 and 410 nm, preferentially 385 nm, has a maximum power consumption of between 100 and 500 W, and requires cooling during its operation. The mold shown in FIG. 3 is equipped with a liquid cooling circuit (e.g., water), while the mold shown in FIG. 6 is equipped with an air or nitrogen cooling circuit. For this purpose, the mold shown in FIG. 6 is equipped with a cooling circuit 35 including an inlet 34 connecting the mold to an air or nitrogen supply and a distribution plate 36 (FIG. 7) in thermal contact with the support 32. The distribution plate 36 has a distribution chamber 38 with inner walls forming a baffle for the cooling gas; the path of the cooling gas through the chamber and the mold is represented by lines with arrows in FIGS. 6 and 7. The plate 36 further has a central orifice 37 through which a guide tube 40 passes and an orifice 39 for receiving the electrical connections of the lamp 30. The gas used to cool the distribution plate 36 then leaves this plate via a conduit 47 and is distributed into an annular chamber 48, then continues into the space provided for this purpose between parts 40 and 45a, and finally exits concentrically along the direction indicated by arrow G into the space created in part 45b. This gas flow therefore has the dual purpose of firstly cooling the distribution plate 36 and secondly intermittently purging the resin solvent or resin micro-projections in suspension from the internal volume of the part 45b, more specifically ensuring the cleanliness of the reflector 33.The polymerisation mould 10a is positioned in the device 1 so that its longitudinal axis AA' is coaxial with the axis XX' of the device 1.

[0041] The mould, part of which is shown in Figure 3, has two available inlets 34 for gas, air or nitrogen, which lead to an annular conduit 48 and then to the interior space of the body 45 along the direction of the arrow G, for the same reason of guaranteeing the cleanliness of the reflector 33. The mould shown in Figure 3, in addition to the mould shown in Figure 6, is equipped with a supply 49 of cooling liquid, which leads to a distribution plate (not shown) and then to a line 51 that returns to the system for circulating and maintaining the temperature of the cooling circuit.

[0042] The first step in the process of the present invention is to create an arrangement of multifilament fibers in a plurality of individual strands that, upon reaching the device 1, form a bundle 20, each strand comprising one or more multifilament fibers. This arrangement is created so that the initial strand is positioned at the center of the device, along the device's axis X-X', and multiple peripheral strands are positioned around the initial strand. For this purpose, an entrance plate 4 of the vacuum chamber 2 is used, which is equipped with multiple orifices through which the strands pass, including a central orifice and multiple peripheral orifices. The arrangement then passes through a separation plate 5 and an exit plate 6 of the impregnation chamber 3. The strands exiting the impregnation chambers subsequently pass through various molds 10a, 10b (and indeed 10c, 10d, and even 10e in the device of FIG. 2), which ensure partial polymerization of each passing strand. The final central strand exiting the final mold 10e passes through final mold 10f. The final die 10f simply brings all the strands together in its center so that the single strand 20f thus obtained can be passed through an irradiation device 50 which ensures the final polymerization of the single strand. Alternatively, the final die 10f is of the same type as the intermediate die and performs the final polymerization of the single strand 20f passing through it.

[0043] Other alternative forms and embodiments of the invention can be envisaged within the scope of the invention as defined in the claims. The process of the invention can use other types of multifilament fibres (even indeed different types of fibres) in one and the same bundle.

[0044] Additionally, it is possible to envision using the splicing process and device of the present invention with thermally polymerizable organic materials.

[0045] It may also be possible for a single reel to feed the bundle into the inlet of the device and separate it into multiple individual strands. [Explanation of symbols]

[0046] 1 device 2. Vacuum chamber 3 Impregnation chamber 4 Entrance Plate 5 Separation plate / intermediate plate 6 Exit Plate 8 Supply Device 9 reels 10a First mold 10b Intermediate mold 10f Final mold / calibration mold 20 multifilament fiber bundles 20f single strand 50 Irradiation Device

Claims

1. 1. A process for continuously manufacturing an elongated composite element comprising a plurality of strands of multifilament fibers embedded in a composition of polymeric material, the process comprising: arranging the plurality of strands such that a central strand (20a) is located at the center of the plurality of strands and other strands are positioned around the central strand; feeding the plurality of strands in a forward direction; Including, The step of feeding in the forward direction includes: degassing the plurality of strands by the action of a vacuum; impregnating said plurality of strands with said composition to obtain impregnated strands; passing the impregnated strand through a first die (10a) where partial polymerization of the composition occurs; passing all of said plurality of strands through a final die (10f) to combine them into a single strand (20f); exposing said single strand (20f) to a radiation source to effect addition polymerization to obtain said elongated composite element; A process that imposes

2. 2. The process of claim 1, wherein the passage of the strands through at least the initial die and the final die is performed in such a way that the strands converge from the impregnation chamber (3), at the exit of which the strands are most spread out, towards the final die where the strands form the single strand (20f).

3. 3. The process of claim 1 or 2, wherein the other strands comprise a plurality of intermediate strands positioned to surround the central strand, the intermediate strands passing through an intermediate mold disposed between the initial mold and the final mold to effect partial polymerization of the composition.

4. The process of claim 1 , wherein the cross section of the composite element is circular.

5. 5. The process of claim 1, wherein the multifilament fibers are selected from the group consisting of glass fibers, carbon fibers, silica fibers, and ceramic fibers.

6. 6. The process of claim 1, wherein the polymerizable material is thermoset.

7. 1. A device (1) for continuously producing elongated composite elements comprising a plurality of strands of multifilament fibers embedded in a composition comprising a polymerizable substance, the device comprising: means for arranging the plurality of strands so that a central strand (20a) is located at the center of the plurality of strands; means for degassing the plurality of strands; means for impregnating the plurality of strands with a composition comprising a polymerizable substance; an initial mold for receiving the impregnated central strand (20a) and for partial polymerization of the composition; at least one final mold (10f) for receiving all of the plurality of strands to form a single strand (20f); and means for polymerizing the composition using an irradiation device (50) to obtain the elongated composite elements.

8. The device according to claim 7, comprising at least one intermediate mould (10b-10e) located between said initial mould (10a) and said final mould (10f).

9. 9. The device according to claim 8, wherein the first mould (10a) and the intermediate moulds (10b-10e) are provided in their centre with an annular ultraviolet lamp (30) containing a guide tube (40) for the strands.

10. 10. The device according to claim 9, wherein the annular ultraviolet lamp (30) comprises a disk (32) for supporting a plurality of light-emitting diodes, the disk having a central opening through which the guide tube (40) passes, a reflector (33) capable of directing radiation emitted by the light-emitting diodes in the direction of the exit of the guide tube, cooling means for cooling the annular ultraviolet lamp, and means for supplying power to the annular ultraviolet lamp.

11. 11. The device according to claim 10, wherein the cooling means comprises a water cooling circuit and / or a device for generating a flow of air or nitrogen.

12. 12. A device according to any one of claims 9 to 11, wherein the internal cross section of each of the guide tubes (40) gradually increases from the upstream side to the downstream side between the initial die (10a) and the final die (10f).

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