FR3053915B1 - METHOD AND INSTALLATION FOR OBTAINING A PROFILE OF A SECTION VARIATED BY PULTRUSION - Google Patents

Abstract

According to a pultrusion method, a profiled piece (10) of thermoplastic composite material is obtained, with the steps of: passing a reinforcing material through an impregnation unit (3) in a pulling direction and impregnating said reinforcing material with a reactive resin; > carrying out polymerization of the resin in a passage tunnel-shaped polymerization unit (4) whose section is wider than the final section of the profiled piece (10) downstream of the impregnation unit; obtaining a partially or fully polymerized fiber-embedding matrix to form a thermoplastic intermediate composite material with the fibers; > pass the intermediate material (9) into a calibration unit (5) and calibrate it by cooling to a specific end section of the desired profile piece.

Description

METHOD AND INSTALLATION FOR OBTAINING A PROFILE OF A VARIED SECTION BY PULTRUSION

FIELD OF THE INVENTION

The present invention relates to a process for obtaining a profiled piece made of composite and / or synthetic material by pultrusion, and a device for implementing this method.

PRIOR ART

For the manufacture of profiles of composite materials, the known pultrusion technique is widely used. It makes it possible to obtain profiles of constant sections with high mechanical properties and in addition having a good performance / weight ratio compared to traditional materials. It involves pultrusion pulling a bundle of unidirectional fibers and / or multidirectional through a die for impregnating said fibers with a polymerizable resin and polymerizing the resin in the die to form a composite profile at the output of said die, consisting of reinforcing fibers and a matrix incorporating the fibers.

This technique is generally implemented with thermosetting resins. The profile is completely formed when it leaves the die. In the case of thermosetting resins, the geometry of the profiled part can not be modified. Each new development requires a new and very expensive sector.

The bundle of fibers is typically a grouping of locks, each lock being composed of a multitude of fibers, for example glass fibers, placed side by side without intersecting. A wick is also called roving in the case of glass or designated by the term "roving".

There are also similar developments in pultrusion with resins of the family of thermoplastics. Indeed, some thermoplastic resins can be worked in the manner of a thermosetting resin, that is to say reactively. The polymerization of the thermoplastic precursors (monomers and oligomers) takes place in situ in the pultrusion tooling. The advantage of this technology lies in the use of low viscosity precursors which leads to the use of very high levels of reinforcement while having excellent and very homogeneous fiber impregnation. The existing reagent systems for pultrusion are mainly based on anionic polymerization mechanisms of monomers such as for polyamide 6, from ε-caprolactam, polyamide 12, from lauryl lactam, radical polymerizations as with PMMA, from methyl methacrylate or polycondensations as with polybutylene terephthalate (PBT) or polyethylene terephthalate (PET) from aromatic polybutylene terephthalate or aromatic polyethylene terephthalate respectively. In the rest of the document, the resin will be called the mixture of precursors which will form the polymer and the matrix after the polymerization reaction.

In this case again, the profile exits in its final form from the pultrusion die which, because of its dimensions (generally from 700 to 1000 mm in length) incorporates an impregnation zone followed by the zone of polymerization also acting as a zone. as it imparts the desired shape to the profile so that the profile exits in its final form, generally in the solid state that is to say at a temperature below the melting point of the resin which the compound. These tools like those for thermosetting resins are extremely expensive.

Finally, it is in principle also possible to impregnate the fibers with a non-reactive melt matrix. This approach opens the possibility of producing a non-definitive form which may be reworked in a subsequent calibration step to form the desired final profile. Nevertheless, the high viscosity of thermoplastics in the molten state leads to an impregnation of the fibers of very average quality. The composite profiles obtained are heterogeneous and the fiber content remains limited to about 50% by volume.

Furthermore, the hot calibration of this type of composite poses the following problems:> the viscosity of the melt generates very high pressure levels at the inlet of the calibration tool which leads to untimely breaks in the fibers > the poor homogeneity of the composite (matrix-rich zones and fiber-rich zones) leads to the creation of privileged leak paths of the melt during the passage in the sizer and does not make it possible to improve the impregnation of the zones initially poor in matter.

OBJECTIVES OF THE INVENTION

To solve these problems the invention aims to provide a method and a device for producing profiled part with a thermoplastic matrix by pultrusion with inexpensive tooling and high productivity.

DESCRIPTION OF THE INVENTION

With these objectives in view, the subject of the invention is a pultrusion method for obtaining a profiled piece of thermoplastic composite material, comprising the steps of:> passing a reinforcing material through an impregnation unit according to a direction of pulling and impregnating said reinforcing material with a reactive resin; polymerizing the resin in a polymerization unit downstream of the impregnation unit so as to obtain a matrix coating the reinforcing material, partially or totally polymerized, to form with the reinforcing material an intermediate composite material thermoplastic; > imparting to the intermediate material a shape by hardening to a specific end section of the desired profile piece; characterized in that said polymerization unit is a heated passage tunnel whose section is larger than the final section of the profiled part, and is followed by a calibration unit in which the intermediate material is shaped and calibrated with cooling to take the specific final section.

As the section of the tunnel is larger than that of the profiled part, the shape of the intermediate material is not determined in the polymerization unit, but only by the calibration unit. The invention therefore proposes a method for producing thermoplastic composite profiles obtained by reactive thermoplastic pultrusion technologies which provides part of the generic tooling (usable for several profiles) and part (the calibration) specific to each profile. This results in a real saving in the development costs of the new profiles obtained according to the invention. In addition, the space between the intermediate material and the walls of the tunnel allows the evacuation of gases that would be generated during the polymerization. Since the tunnel is simpler and less expensive to manufacture, since it is not adapted to the geometry of the profile to be produced, it makes it possible to manage longer polymerization times and / or higher production speeds. The shape of the intermediate material does not have a direct link with that of the final section, they can deform as desired during this phase without causing problems. The length of said tunnel is such that it allows for a given speed a residence time of the composite during polymerization of the order of 0.1 to 10 min, typically 0.1 to 5 min and preferably 0.1 at 3 min.

The fibers of the composite material are chosen from a group comprising mineral fibers, glass fibers, basalt fibers, organic fibers, carbon fibers, aramid fibers, either in the form of unidirectional locks or under form of multiaxial reinforcements, metal fibers, and mixtures of the aforementioned fibers.

According to an improvement, the intermediate material is subdivided into a plurality of intermediate inserts passing through the polymerization unit to form the final profile by grouping in the calibration unit.

Throughout the document, the term "generic pultrusion die" includes a system, intended to produce intermediate composite inserts, having at least one impregnation unit and a polymerization unit. The idea of producing a multitude of intermediate inserts by reactive thermoplastic pultrusion is based on the following two observations: the use of a reactive thermoplastic pultrusion technology makes it possible to perfectly impregnate a very high fiber content with a very small amount of resin. During the calibration step when the molten inserts are grouped and compacted during the passage in the calibration die, there is virtually no backflow of material, or dripping that might freeze and block the passage, as this occurs with the melt approaches. In addition, each fiber unitarily being perfectly impregnated, there is no need to look for significant consolidation pressures as is the case with initially poorly impregnated profiles since there is no need to circulate the matter between the fibers. The contact with a low pressure between the melt inserts is sufficient to group them homogeneously. The risks of breaking the fibers as a result of the pressure applied to the sizing inlet are significantly reduced.

Finally, in the case of chemical systems with high reactivity, it is necessary to impregnate the fibers at high speed so as to have a residence time of the activated resin in the impregnation unit as low as possible. The fact of producing, initially, a multitude of intermediate inserts smaller than the final profile, facilitates and accelerates the impregnation of the fibers and thus to take advantage of high production rates.

According to one embodiment, at least one of the inserts is in the form of a continuous web. It is thus possible to easily produce profiles having thin walls but following any contours. Several plies can be stacked to give the profiled piece sufficient thickness. The reinforcing material may be continuous fibers in the pultrusion direction, or multiaxial, as with a fabric in which the fibers are intertwined. The choice of the sheet is a choice that also simplifies the machining of the impregnation unit.

According to preferred features, said ply has a thickness of 0.1 mm to 5 mm, typically 0.1 to 3 mm, and preferably less than 1.5 mm. It can thus be easily impregnated while being able to impart satisfactory mechanical characteristics to the profiled part.

According to another embodiment, said inserts are in the form of small sections whose section has a maximum dimension of 0.1 mm to 5 mm, typically 0.1 to 3 mm, and preferably less than or equal to 2 mm. This approach offers more positioning flexibility so as to be freer in the shapes to be made for the final profile. They can then be round, square or of another form, it being understood that this form is temporary since once melted, said inserts are caused to deform and to regroup in a homogeneous manner making their initial shape disappear. The shape of the inserts is chosen so as to allow simple and economical machining of the generic pultrusion die. An insert contains from one to a few dozen "rovings", according to the grammages used. The said generic die may contain several tens or even hundreds of these inserts depending on the type of profiles to produce. The sum of the section of the set of inserts representing more or less the maximum section possible for the final section. In the case of small inserts, the fibers are generally oriented only in the direction of pultrusion.

According to an improvement, the reinforcing material is subdivided into a plurality of beams passing through the impregnation unit to form the plurality of inserts after impregnation with the reactive resin. Alternatively, one could impregnate the reinforcing material in a single section and subdivide the material so impregnated during its passage through the tunnel.

Preferably, an inert gas is circulated in the tunnel around the intermediate composite material in the polymerization unit. This allows in particular to evacuate the gases generated by the polymerization and to homogenize the temperature in the tunnel, without providing gas that could be detrimental to the polymerization.

Said neutral gas in the passage tunnel is, for example, nitrogen. This neutral gas avoids the supply of oxygen which could affect the quality of the polymerization.

According to an improvement of the process, the inserts are subjected to ultraviolet, infrared or microwave radiation in the passage tunnel. This radiation is able to promote the polymerization either by direct effect when the precursors are activated to receive such radiation, or by the rise in temperature it causes. The polymerization rate determines the length of the tunnel and the productivity of the process.

According to another improvement, the inserts are heated in said passage tunnel. The rise in temperature can be achieved by circulating the previously heated neutral gas, subjecting the inserts to radiation as indicated above, or by a combination of these techniques.

Thanks to the reactive pultrusion technology, the inserts and thus the final profile contain a fiber content greater than 50% by volume, typically between 55 and 75% and preferably of the order of 60%.

The precursors impregnating the fibers are chosen so as to have viscosities less than 100 Pa.s, preferably less than 50 Pa.s and generally less than 10 Pa.s. The invention applies in particular to resins polymerizable anionically, such as PA6 and PA12, by a radical route, such as PMMA, by polycondensation from di-acid and / or di-amine, such as certain polyamides, or by the action of a chain extender on a di-acid and / or a di-amine. amine. The invention also relates to a pultrusion installation for obtaining a profiled piece of thermoplastic composite material, comprising:> an impregnation unit for passing a reinforcing material therethrough in a direction of pulling and impregnating said reinforcing material with a reactive resin; a polymerization unit downstream of the impregnating unit for polymerizing the resin so as to obtain a partially or fully polymerized matrix coating the fibers to form a thermoplastic intermediate composite material with the fibers; > curing means receiving the intermediate material to harden it by cooling to a specific end section of the desired profile piece; characterized in that said polymerization unit is a heated passage tunnel whose section is larger than the final section of the profiled piece, the installation comprising a calibration unit following the polymerization unit to conform the material calibrated intermediate with cooling to take the specific final section, the calibration unit comprising the curing means, the installation implementing the method as described above.

According to an improvement, the installation comprises ventilation means for circulating an inert gas in the tunnel around the intermediate composite material in the polymerization unit.

Advantageously, the calibration unit is removable relative to the polymerization unit. The calibration unit only defines the final shape of the profile. To adapt the tooling to the profiled part to be produced, only this part has to be changed, which reduces the costs for a new part.

According to another improvement, the installation comprises means for drawing the profile from the calibration unit for simultaneously drawing the inserts through the impregnating units and polymerization. They can for example be Caterpillar type widely used in pultrusion or extrusion techniques. The drawing means of the profile from the calibration unit are used simultaneously to draw the intermediate inserts. The invention also relates to composite profiles manufactured by the method as described above, characterized in that they constitute parts of road vehicles, parts of aircraft, trains or any other means of transport, reinforcements electrical cables, guy wires, oil platform inking cables, hot stamping plates, building profiles, window profiles, leaf springs, small diameter rods for recutting to make long fiber granules used in injection and / or plastic extrusion, so-called "tape" thin strips to be deposited and heat-bonded to form more complex parts or even any other section subjected to mechanical stresses.

BRIEF DESCRIPTION OF THE FIGURES The invention will be better understood, and other features and advantages thereof will appear, with reference to the accompanying diagrammatic drawings, which represent, by way of non-limiting examples, a possible embodiment of the device concerned. . FIG. 1 represents an installation according to a first embodiment of the invention. > Figure 2 illustrates the manufacture of a U-shaped profile consisting of a plurality of inserts 9a of round initial shape. > Figure 3 illustrates the manufacture of a U-shaped profile consisting of a plurality of inserts forming webs at the output of the impregnation unit. > Figure 4 shows a variable section impregnation unit. FIG. 5 illustrates the manufacture of a U-shaped profile from a reinforcing material of round initial section. Figure 6 illustrates the manufacture of a square section profile from a round section initial reinforcing material.

DETAILED DESCRIPTION

FIG. 1 shows an installation 1 successively comprising a preheating unit 2 for the fibers, forming a reinforcing material, which makes it possible to bring the fibers to a temperature close to the melting temperature of the reactive precursors; a generic die (3 + 4) composed of an impregnation unit 3 and a polymerization unit 4. In the example illustrated in FIG. 1, the polymerization unit 4 is a tunnel heated under nitrogen. Its length is 3 m long so that for a speed of 1m / min, there is 3 minutes of polymerization time. The installation 1 further comprises an injection unit 3 of the reactive precursors. Advantageously, as illustrated, the reactive precursors are metered separately and mixed just at the inlet of the impregnation unit 3, for example in a static mixer 7. The mixing equipment 6 may be, depending on the viscosity precursors and their reactivity, single or twin-screw extruders, or else dosing machines known per se, generally equipped with gear pumps. The installation also comprises a chilled specific calibration unit 5 which determines the final shape, with or without shrinkage, of the composite section 10 obtained according to the invention, and a drawing unit 8 which in the illustrated case makes it possible to advance simultaneously the inserts 9 and the final profile calibrated 10 in the calibration unit 5.

The inserts illustrated in Figure 2 are 24 (3x8). Each insert is formed by the impregnation of a bundle of fibers. Each insert has a diameter of 3 mm, that is to say a section of about 7 mm 2. The shape of the profile U of the calibration unit has the following geometrical dimensions: L = 30 mm; H = 20 mm; ep = 2.6 mm The section of the profile U is therefore: 168.48 mm; equivalent to the section represented by the sum of the sections of the inserts.

The inserts illustrated in FIG. 3 are grouped into 3 plies with a width of 65 mm and a respective thickness of 0.86 mm, ie an overall section of 0.86 × 3 × 65 = 167.7 mm 2 equivalent to the section of the section U.

In Figures 2 and 3, the polymerization tunnel 4 is not shown for more visibility. Likewise, the calibration unit 5 comprises upstream guiding means enabling each insert to be positioned correctly and systematically at the input of the calibration tool. This guidance system is not shown. It precedes the calibration unit over a guiding distance greater than 20 mm, typically 75 mm and preferably greater than 100 mm.

In the example of FIG. 4, an impregnation unit 3c has two parts, a first part 31 having a groove 310, and a second part 32 having a post 320. The post 320 is fitted in the groove 310. spacing between the first and the second portion 31, 32 is adjusted so that the free section in the groove and limited by the pin 320 is determined. The spacing is adjusted for example by shims 33. Thus, the impregnating unit 3c makes it possible to provide a section of intermediate material 9 adjusted to the quantity necessary and sufficient to form the part, even if the part does not have the same shape in section as that of the impregnation unit 3c. The example of FIG. 5 shows that from an impregnation unit 3d supplying an intermediate material 9d under a round section, it can be passed to a U-shaped section in the calibration unit. 5.

Similarly, the example of Figure 6 shows that from an impregnating unit 3e providing an intermediate material 9e under a round section, we can pass it to a section of the same value but in the form of square in the 5th calibration unit. The invention has been described above with reference to an exemplary embodiment. It goes without saying that it is not limited to this embodiment but that it extends to all the embodiments covered by the appended claims.

Claims (18)

claims A pultrusion method for obtaining a profiled piece (10) of thermoplastic composite material, comprising the steps of: passing a reinforcing material through an impregnating unit (3) in a pulling direction and impregnating said material with reinforcement with a reactive resin; polymerizing the resin in a polymerization unit (4) downstream of the impregnation unit so as to obtain a coating matrix, the reinforcing material, partially or totally polymerized, to form with the reinforcing a thermopiastic intermediate composite material; > imparting to the intermediate material (9) a form by curing a specific end section of the desired profiled part; characterized in that said polymerization unit (4) is a heated passage tunnel whose section is larger than the final section of the profiled piece (10), and is followed by a calibration unit (5) in which the material intermediate is shaped and calibrated with cooling to take the specific final section, The method according to claim 1, wherein the intermediate material (9) is subdivided into a plurality of intermediate inserts (9a) passing through the polymerization unit to form the final profile by grouping in the sizing unit (5). ). 3. Method according to claim 2, characterized in that at least one of the inserts has the form of a continuous web (9b). 4. Method according to claim 3, characterized in that said web (9b) have a thickness of 0.1 mm to 5 mm, typically from 0.1 to 3 mm, and preferably less than 1.5 mm, 5. Method according to claim 2, characterized in that said inserts are in the form of small sections (9a) whose section has a maximum dimension of 0.1 mm to 5 mm, typically from 0.1 to 3 mm, and preferably less than or equal to 2 mm, 6. Method according to one of claims 2 to 5, wherein the reinforcing material is subdivided into a plurality of beams passing through the impregnation unit (3a) to form the plurality of inserts (9a) after impregnation with 1a reactive resin, 7. Method according to one of claims 2 to 6, characterized in that the inserts are subjected to ultraviolet radiation, infrared or microwaves in the tunnel passage. 8. Process according to one of Claims 2 to 7, characterized in that the inserts are heated in said passage tunnel. 9. Method according to one of claims 2 to 8, characterized in that the fiber content of the composite inserts (9) is greater than 50% by volume, typically between 55 and 75% and preferably of the order of 60 %. 10. Method according to one of claims 1 to 9, characterized in that circulates an inert gas in the tunnel around the intermediate composite material in the polymerization unit (4). 11. The method of claim 10, characterized in that said inert gas in the passage tunnel is nitrogen. 12. Method according to one of claims 1 to 11, characterized in that the viscosity of the thermoplastic precursors used forming the reactive resin is less than 100 Pa.s, preferably less than 50 Pa.s and generally less than 10 Pa.s. . 13. Method according to one of claims 1 to 12, characterized in that the thermoplastic precursors used forming the reactive resin are anionically polymerizable such as PAO and PA12, radica-larly as PMMA, by polycondensation as some polyamides or by the action of a chain extender on a di-acid and / or a di-amine. 14. A pultrusion installation for obtaining a profiled piece (7) made of a thermoplastic composite material, comprising: an impregnation unit (3) for passing a reinforcing material therethrough in a pulling direction and impregnating said material with reinforcement with a reactive resin; t> a polymerization unit (4) downstream of the impregnation unit to carry out a polymerization of the resin so as to obtain a matrix coating the reinforcement material, partially or totally polymerized, to form with the reinforcing material a thermopiastic intermediate composite material; curing means (5) receiving the intermediate material (10) for curing it by cooling to a specific end section of the desired shaped part; characterized in that said polymerization unit (4) is a heated passage tunnel whose section is larger than the final section of the profiled piece (10), the installation comprising a calibration unit (5) following the polymerization unit for forming the calibrated intermediate material with cooling to take the specific final section, the calibration unit comprising the curing means, the plant implementing the method according to one of claims 1 to 13. 15. Installation according to claim 14, characterized in that it comprises ventilation means for circulating an inert gas in the tunnel around the intermediate composite material in the polymerization unit (4) 16. Installation according to one of claims 14 to 15, characterized in that the calibration unit is removable relative to the polymerization unit. 17. Installation according to one of claims 14 to 16, characterized in that it comprises pulling means (8) of the profile (10) from the calibration unit (5) simultaneously serving to draw the inserts (9) at through impregnation and polymerization units. 18. Profiled parts (10) produced by the method according to one of claims 1 to 13, characterized in that they constitute parts of road vehicles, parts of aircraft, trains or any other means of transport, reinforcements of electrical cables, guy wires, oil platform anchor cables, hot stamping plates, building profiles, window profiles, leaf springs, small diameter rods intended for to be cut to make long fiber granules usable in injection and / or plastic extrusion, so-called "tape" thin strips to be deposited and heat-bonded to form more complex parts or even any other section subjected to mechanical stresses .