Manufacturing process of a tubular profile by pultrusion and resulting profile.

Abstract

According to a process for manufacturing a tubular profile (7) by reactive thermoplastic pultrusion, a hollow body (70) of the tubular profile (7) is formed by passing a first reinforcing material made of fibers through a pultrusion tool (4), and impregnating the first reinforcing material with a reactive mixture to generate a matrix of a first thermoplastic material, the hollow body (70) delimiting at least one central cavity (72). An inner layer (71) is further deposited by extrusion of a second thermoplastic material onto the hollow body (70) on the side of the cavity (72). Profile obtained by the process. Figure for the abbreviation: Fig. 1

Description

Title of the invention: Method for manufacturing a tubular profile by pultrusion and profile obtained. technical field

[0001] The invention relates to a method for manufacturing a tubular profile by reactive thermoplastic pultrusion. It also relates to a tubular profile obtained by this method. Previous technique

[0002] For the manufacture of composite profiles, the well-known pultrusion technique is widely used. It allows for the production of profiles with constant cross-sections, high mechanical properties, and, moreover, a good performance-to-weight ratio compared to traditional materials. Pultrusion involves continuously or semi-continuously drawing a bundle of unidirectional and / or multidirectional fibers through a die. This process impregnates the fibers with a polymerizable resin, and the resin polymerizes within the die to form a composite profile at the die's exit, with a matrix incorporating the fibers. This technique is generally implemented with thermosetting resins. The profile is fully formed and perfectly straight as it exits the die.

[0003] The fiber bundle is typically a grouping of rovings, each roving being composed of a multitude of fibers, for example glass fibers, placed side-by-side without crossing. A roving is also called a stratifil in the case of glass or designated by the English term "roving".

[0004] Certain thermoplastic resins can be processed in the same way as a thermosetting resin, that is, by reactive means. The polymerization of the thermoplastic monomers then takes place in situ within the pultrusion tooling. In this case, the profile generally emerges in the final shape of the pultrusion die, which, within its length generally ranging from 700 to 1000 mm, incorporates an impregnation zone followed by a polymerization zone in the shape of the desired profile, so that the profile emerges in its final form, generally in a solid state, that is, at a temperature below the melting point of the matrix from which it is composed. The polymerization zone therefore also serves as a calibration zone.

[0005] The advantage of this technology lies in the use of precursors such as very low viscosity monomers, which allows for very high reinforcement ratios while achieving excellent and very homogeneous fiber impregnation. Existing reactive systems for pultrusion are mainly based on anionic polymerization mechanisms of monomers, as for the polyamide-6, from e-caprolactam, polyamide 12, from lauryllactam, or radical polymerizations such as with PMMA, from methyl methacrylate.

[0006] Although the mechanical and processing properties of polyamide are interesting, this material has the drawback of being sensitive to humidity, which limits its use in humid environments.

[0007] Document EP 3 529 062-Al shows the manufacture of a profile by thermoplastic reactive pultrusion in polyamide, with the deposition of an outer layer of PVC. The profile is thus protected from moisture from the outside. However, the profile is hollow and the central cavity can, under certain circumstances, be exposed to moisture, such that the polyamide can absorb moisture.

[0008] US patent 4,202,718 A shows an installation and a method for manufacturing a conduit comprising a reinforcement with longitudinal wires and two windings embedded in a matrix of elastomeric synthetic material. The synthetic material is deposited by extrusion over and under the reinforcement. In one version, a central tube is pre-formed and the reinforcement is deposited over the tube with adhesive. Extruding a synthetic material onto the reinforcement does not allow for a high fiber density due to the limited wettability of the reinforcement under these conditions. Description of the invention

[0009] It is therefore an objective of the invention to provide a process for manufacturing profiles in reactive thermoplastic pultrusion which allow better protection of the profile.

[0010] With these objectives in view, the invention relates to a method for manufacturing a tubular profile by reactive thermoplastic pultrusion, according to which a hollow body of the tubular profile is formed by passing a first reinforcing material made of fibers through a pultrusion tool, and by impregnating the first reinforcing material with a reactive mixture to generate a matrix of a first thermoplastic material, the hollow body delimiting at least one central cavity, the method being characterized in that an internal layer is deposited by extrusion of a second thermoplastic material on the hollow body on the side of the cavity.

[0011] By incorporating an internal layer on the hollow body, specific properties can be imparted to the internal surface of the profile. The layer is deposited in the same way as an external layer by co-extrusion, but with the application originating from the central cavity. The use of a reactive mixture to generate the initial thermoplastic material allows for fine impregnation of the fibers and results in a high density of reinforcing material. Compared to a process using a material With thermosetting materials, it is easier to find first and second material combinations within the thermoplastic range that allow for good adhesion of the inner layer to the hollow body. Compared to US patent 4,202,718 A, the reactive thermoplastic pultrusion process allows for a higher fiber density. Compared to the embodiment with a pre-extruded central tube, which must be sufficiently tough to withstand winding, it is possible to use a second thermoplastic material with a very thin profile and a relatively low melting point, such as polypropylene.

[0012] According to one embodiment, the first thermoplastic material is selected from a group comprising polyamide-6, polyamide-12 and polymethyl methacrylate. All these materials can be obtained by reactive mixing of precursors.

[0013] According to an improvement, an outer layer of a third thermoplastic material is deposited onto the profile by co-extrusion. Thus, the hollow body is protected both internally and externally.

[0014] According to one technical arrangement, a hollow mandrel passing through the pultrusion tooling and terminating in an extrusion head is used to deposit the inner layer. The inside of the mandrel serves as a conduit to supply the extrusion head with the second molten thermoplastic material. The mandrel forms a rod that is supported upstream of the worm assembly in the form of the hollow body. The mandrel may also include heating elements to keep the second thermoplastic material molten.

[0015] According to an improvement, a calibration unit is used opposite the extrusion head. The calibration unit contains the profile and prevents its expansion under the pressure of the extrusion on the inner side. The calibration unit can be placed upstream or downstream of the outer layer deposition point when the outer layer is deposited. Alternatively, the extrusion head is placed opposite the point where the outer layer is co-extruded, so that the extrusion pressures are balanced, with the calibration unit, if any, being placed downstream.

[0016] According to an improvement, the first reinforcing material is dry-formed by creating a base layer with unidirectional fibers in the longitudinal direction or with a textile around the mandrel, and at least one winding or braiding of fibers is deposited on the base layer. The base layer ensures that the reinforcing material can be conveyed through the installation, in addition to providing the profile's tensile and flexural strength. The windings or braidings introduce fibers in a transverse direction and provide additional strength, particularly to torsion and internal pressure within the cavity. This contrasts with a pultrusion process using thermosetting material, which requires coating the fiber strands with the liquid reactive material and conveying The fibers are impregnated before the strands are joined together to form the body. If a high fiber density is desired, here the reinforcing material is worked dry, which is simpler and cleaner.

[0017] The invention also relates to a tubular profile comprising a hollow body comprising a first reinforcing material formed of fibers in a matrix of a first thermoplastic material, the hollow body delimiting a cavity, the profile being characterized in that it comprises an internal layer covering the hollow body from the inside and in that it is obtained by a process as described above.

[0018] According to one improvement, the reinforcing material comprises a base layer formed of unidirectional fibers in the longitudinal direction or a textile and at least one winding or braiding of fibers around the base layer.

[0019] The thickness of the inner layer is, for example, between 0.2 mm and 3 mm. Such a thickness is generally sufficient to provide the desired properties of the inner layer.

[0020] According to an improvement, the hollow body is coated with an outer layer of a third thermoplastic material. Thus, the hollow body can be completely encapsulated between the inner and outer layers.

[0021] According to a feature of the profile, the reinforcing material of the hollow body represents at least 60% of the volume of the hollow body, preferably at least 65%. The mechanical characteristics of such a profile are very advantageous.

[0022] According to an improvement, the first thermoplastic material and the second thermoplastic material are chosen to obtain good adhesion of the inner layer to the hollow body.

[0023] According to one embodiment, the first thermoplastic material is based on polyamide-6 and the second thermoplastic material is selected from a group comprising polypropylene, polyethylene, and polyvinylidene fluoride, the second thermoplastic material being modified by the grafting of maleic acid. The addition of maleic acid to the second thermoplastic material gives it adhesion properties to polyamide-6.

[0024] According to another embodiment, the second thermoplastic material is of the same nature as the first thermoplastic material or is a mixture with at least one material of the same nature as the first thermoplastic material. The same nature of the thermoplastic materials allows for excellent bonding between them. Although of the same nature, the properties of the inner layer may differ from those of the first thermoplastic material. It may contain specific additives or simply be free of additives that are used to catalyze the polymerization of the first thermoplastic material. Depositing the second Extrusion of thermoplastic material allows it to have a different structure, for example by being crystalline or semi-crystalline.

[0025] The profile is, for example, a fluid conduit. The quality of the inner layer can be freely chosen, independently of the first thermoplastic material, and according to its compatibility with the fluid to be conveyed. The fluid is, for example, hydrogen gas. In this application, the second thermoplastic material can be polyamide with a thickness between 1 and 3 mm. The fluid can be drinking water, and in this case, the second thermoplastic material can be food-grade polyethylene.

[0026] The profile is, for example, a winding drum for floating elements suitable for immersion in a swimming pool. Such a drum is used to deploy a cover or lines of floats to separate lanes as needed. The second and third thermoplastic materials can be chosen to be moisture-resistant, thus protecting the hollow body from both the inside and outside. In such an application, although moisture-sensitive, the first thermoplastic material can be polyamide. The thickness of the inner and outer layers does not need to be significant, for example, between 0.2 and 0.5 mm, which is sufficient to create a moisture barrier. Brief description of the figures

[0027] The invention will be better understood and other features and advantages will become apparent upon reading the following description, the description referring to the accompanying drawings, among which:

[0028] - [Fig. 1] is a cross-sectional view of a profile conforming to an embodiment of the invention; - [Fig.2] is a schematic view of a pultrusion installation for manufacturing the profile of [Fig.1]; - [Fig.3] is a cross-sectional view of the pultrusion tool from [Fig.2]. Detailed description

[0029] A profile according to a first embodiment of the invention is shown in cross-section in [Fig. 1]. The profile 7 comprises a hollow body 70 of tubular shape, so as to delimit a cavity 72. The profile 7 further comprises an inner layer 71 lining the hollow body 70 in the cavity 72 and an outer layer 73 lining the hollow body 70 from the outside.

[0030] The hollow body 70 is a composite material formed by a reinforcing material composed of unidirectional fibers in a matrix of a first thermoplastic material. The volume of the fibers represents, for example, between 60% and 70% of the volume of the hollow body 70. The fibers can be of any type used Typically used for the formation of composite materials, for example glass, carbon, basalt, aramid fibers, or natural fibers such as hemp or flax. In this example, the first thermoplastic material is polyamide-6.

[0031] The reinforcing material is formed of several superimposed layers, with the following in order from the inside out: • a first layer of unidirectional longitudinal fibers; • a second layer of fibers wound in one direction; • a third layer of unidirectional longitudinal fibers; • a fourth layer of fibers wound in a second direction opposite to the first meaning; • a fifth layer of unidirectional longitudinal fibers.

[0032] The inner and outer layers 71, 73 are for example made of polypropylene with an addition of maleic acid in order to obtain good adhesion to the hollow body 70. The layers 71, 73 are used essentially for their moisture barrier function.

[0033] A pultrusion manufacturing installation for profile 7 is described with reference to Figures 2 and 3. The pultrusion installation comprises successively: • a reeling unit 1 for reeling rovings M of fibers forming the reinforcing material, also called "rovings" in English, part of the rovings forming the first layer of unidirectional longitudinal fibers; • a first winding unit 31 unwinding spools of wicks to form the second layer of wound fibers; • a first preheating unit 32 of the first and second layers and of a second part of the strands which allows the reinforcing material to be dried and brought to a temperature favorable to polymerization; the strands M which pass through the first preheating unit 32 form the third layer of unidirectional longitudinal fibers; • a second winding unit 33 unwinding spools of wicks to form the fourth layer of wound fibers; • a second preheating unit 34 which allows the reinforcing material to be dried and brought to a temperature favorable to polymerization; the strands which pass through the second preheating unit 34 form the fifth layer of unidirectional longitudinal fibers; • a pultrusion tooling 4 consisting of an impregnation unit 41 for impregnating the reinforcing material exiting the second preheating unit 34 with a reactive mixture and a polymerization unit 42 from which the hollow body 70 exits; • a first coextrusion unit 2 which feeds a mandrel 20 to deposit the inner layer 71 into the hollow body 70; • a mixing unit 5 to mix precursors and provide a reactive mixture in liquid state to the impregnation unit 41; • a second coextrusion unit 6 to deposit the outer layer 73 onto the hollow body 70 of the profile 7; • and a drawing unit 8 to draw the profile 7 out of the second coextrusion unit 6, drawing the reinforcing material through the installation from the unwinding of the strands.

[0034] Each winding is characterized by a helix angle between the fiber direction and a radial plane, that is, a plane perpendicular to the mandrel axis. This angle can be almost zero or reach up to 60°. The resulting mechanical properties vary. When the helix angle is significant, it is preferable to use an even number of winding layers, with alternating right- and left-handed windings, in order to obtain homogeneous strength properties.

[0035] In the mixing unit 5, precursors are stored in liquid form in tanks A, B, C. The precursors are conveyed to the mixing unit 5 at a controlled flow rate and mixed to form the liquid reactive mixture. The reactive mixture is injected into the impregnation unit 41 to wet the reinforcing material and form an intermediate composite material 7a.

[0036] In the polymerization unit 42, the intermediate composite material 7a is mounted and maintained at temperature. The reactive mixture reacts under the effect of temperature and polymerizes at least partially to form the first thermoplastic material.

[0037] The mandrel 20 defines the cavity 72 during the polymerization phase. It extends to the outlet of the polymerization unit and supports an extrusion head 21. The inside of the mandrel contains an insulated, temperature-controlled conduit 201 to supply the extrusion head 21 with the second molten thermoplastic material. The body 70 exits the polymerization unit 42 and, sufficiently hardened, enters a calibration unit 23 opposite the extrusion head 21. The first coextrusion unit 2 includes a first extruder 22 capable of melting and supplying the second molten thermoplastic material under pressure to the extrusion head 21 via the mandrel 20. The extrusion head 21 then deposits the inner layer 71 inside the hollow body 70 onto the wall.

[0038] The body 70 exits the calibration unit 23 and enters the co-extrusion die 60, which is part of the second co-extrusion unit 6. The second co-extrusion unit 6 includes a second extruder 61 capable of melting and supplying the third molten thermoplastic material under pressure to the co-extrusion die 60. The co-extrusion die 60 then deposits the outer layer 73 around the body 70 of the profile 7.

[0039] The pulling unit 8 draws the profile 7 and the fibers through the installation by exerting traction. A cutting unit, not shown, cuts the profile 7 into sections, also not shown. The pulling unit 8 includes, for example, a pair of tracks that grip the profile 7 during pulling.

[0040] The invention is not limited to the embodiment described by way of example only. The cross-section of the profile 7 is not necessarily circular, but could have any other tubular shape. The second and third thermoplastic materials may be different. The installation may include additional winding units to form multiple wound layers. The winding units may be replaced by braiding units.

Claims

Demands

1. A method for manufacturing a tubular profile (7) by reactive thermoplastic pultrusion, in which a hollow body (70) of the tubular profile (7) is formed by passing a first reinforcing material made of fibers through a pultrusion tool (4), and by impregnating the first reinforcing material with a reactive mixture to generate a matrix of a first thermoplastic material, the hollow body (70) delimiting at least one central cavity (72), the method being characterized in that an internal layer (71) is deposited by extrusion of a second thermoplastic material onto the hollow body (70) on the side of the cavity (72).

2. A method according to claim 1, wherein the first thermoplastic material is selected from a group comprising polyamide-6, polyamide-12 and polymethyl methacrylate.

3. A method according to any one of the preceding claims, characterized in that an external layer (73) is deposited by co-extrusion of a third thermoplastic material onto the profile (7).

4. A method according to any one of the preceding claims, characterized in that a hollow mandrel (20) passing through the pultrusion tooling and terminated by an extrusion head (21) is used to deposit the inner layer (71), the inside of the mandrel (20) serving as a conduit (201) to supply the extrusion head (21) with the second molten thermoplastic material.

5. Method according to claim 4, characterized in that a calibration unit (23) is used in relation to the extrusion head (21).

6. A method according to any one of claims 4 or 5, wherein the first reinforcing material is dry-formed by forming a base layer with unidirectional fibers in the longitudinal direction or with a textile around the mandrel (20) and at least one winding or braiding of fibers is deposited on the base layer.

7. Tubular profile comprising a hollow body (70) comprising a first reinforcing material formed of fibers in a matrix of a first thermoplastic material, the hollow body (70) delimiting a cavity (72), the profile (7) being characterized in that it comprises an internal layer (71) coating the hollow body (70) from the inside and in that it is obtained by a process according to any one of claims 1 to 6.

8. Profile according to claim 7, wherein the reinforcing material comprises a base layer formed of unidirectional fibers in the longitudinal direction or of a textile and at least one winding or braiding of fibers around the base layer.

9. Profile according to any one of claims 7 or 8, wherein the thickness of the inner layer (71) is between 0.2 mm and 3 mm.

10. Profile according to any one of claims 7 to 9, wherein the hollow body (70) is coated with an outer layer (73) of a third thermoplastic material.

11. Profile according to any one of claims 7 to 10, wherein the hollow body reinforcement material (70) represents at least 60% of the volume of the hollow body, preferably at least 65%.

12. Profile according to any one of claims 7 to 11, wherein the first thermoplastic material and the second thermoplastic material are chosen to obtain good adhesion of the inner layer (71) to the hollow body (70).

13. Profile according to claim 12, wherein the first thermoplastic material is based on polyamide-6 and the second thermoplastic material is selected from a group comprising polypropylene, polyethylene and polyvinylidene fluoride, the second thermoplastic material being modified by grafting maleic acid.

14. Profile according to claim 12, wherein the second thermoplastic material is of the same nature as the first thermoplastic material or is a mixture with at least one material of the same nature as the first thermoplastic material.

15. Fluid pipeline, characterized in that it is formed by a profile (7) according to claim 7 to 14.

16. Floating element winding drum suitable for immersion in a swimming pool, characterized in that it is formed by a profile (7) according to claim 7 to 14 in combination with claim 10.

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