FR3037856A1 - PROCESS FOR PRODUCING A RIGID COMPOSITE STRUCTURE OBTAINED BY WELDING PROFILES AND RIGID FRAMES OBTAINED THEREBY - Google Patents

Abstract

Process for producing a rigid structure obtained by assembling structural sections in which the structural sections are obtained by pultrusion technology and characterized in that: the matrix used for pultrusion production of said profiles is a thermoplastic resin of the family of acrylics and / or acrylates and / or polyacrylics and / or polyacrylates - the angles of connection between the profiles are assembled by welding at least one end of the profiles with another profile of the same section.

Description

The present invention relates to a method for producing a rigid structure from pultruded composite profiles, that is to say obtained by pultrusion technology. It also relates to the potential applications of such a structure in the form of frames.

Traditionally, composite profiles obtained from thermosetting resins are used in many applications for structural purposes, and in particular to replace aluminum in situations where improved thermal insulation is desirable.

This is particularly the case for applications such as solar thermal collectors or even window frames. For this last example, other extruded polymer profile solutions (such as PVC) exist and occupy the vast majority of the market. These profiles are generally obtained by the extrusion technique and have relatively low mechanical properties, especially in flexion compared to other materials such as aluminum. In certain applications requiring good resistance to flexing under load as in the case of profiles of large windows or veranda, it is therefore known to reinforce locally these plastic profiles by pultruded composite profiles commonly called "inserts" with a high resistance. traction / bending so as to stiffen the plastic profile and limit its thermal expansion. Nevertheless, the overall stiffness obtained for the profile is much lower than that of aluminum and limits its use to more restricted applications in terms of frame dimensions. Another more recent approach is to use traditional pultruded profiles obtained on the basis of thermosetting resins. In view of the great fragility of these thermosetting resins, these composite materials are generally obtained from a multidirectional arrangement of fibers; said fibers being mainly oriented in the direction of the long length of the profile to favor a good rigidity to the longitudinal bending and minority in the transverse direction to ensure a minimum transverse strength. In this configuration, the average values of longitudinal stiffness 3037856 are of the order of 30 to 40 Gpa, sometimes 45 Gpa. These values are still significantly lower than that of aluminum with 70 Gpa. Finally, the thermosetting pultruded profiles are neither hot deformable nor weldable. They therefore impose an assembly mode by screwing and / or gluing when it comes to building a rigid frame-type structure. This mode of construction is absolutely not used by the manufacturers of PVC windows mentioned above, which account for 75% of the window market.

The present invention aims to solve all these problems by proposing a method of manufacturing a rigid structure (which can take the form of a window frame) by welded assembly of several pultruded profiles. The invention thus makes it possible to produce frames with composite profiles having: - comparable stiffness in longitudinal flexion to that of aluminum, - thermal conductivity 500 times lower than that of aluminum - an assembly technique by fast and inexpensive welding, similar or even identical to that used for the assembly of PVC profiles. Precisely, the invention relates to a method for producing a rigid structure obtained by assembling structural sections in which the structural sections are obtained. by a pultrusion technology and characterized in that: - the matrix used for the pultrusion production of said profiles is a thermoplastic resin of the family of acrylics and / or acrylates and / or polyacrylics and / or polyacrylates, - the angles connection between the profiles are assembled by welding at least one end of the profiles with another profile of the same ction under the action of temperature and a pressure force. Thanks to the use of a thermoplastic resin, two sections heated and put in contact under pressure has a contact zone where the matrix and the fibers of the two sections interpenetrate and form a rigid connection zone after cooling.

The pultruded sections constituting the rigid structures that are the subject of the present invention are obtained by the thermoplastic pultrusion process. They can be obtained by impregnating the reinforcing fibers with a molten polymer and then being cooled during the calibration phase or else be obtained by the so-called reactive thermoplastic pultrusion technique. In the case of the invention, the matrix of the pultruded profile will preferably be obtained from a polymerizable syrup constituted before polymerization of a solution of at least one liquid precursor in the form of monomers and / or oligomers and and / or thermoplastic polymers solubilized and polymerizable under the action of a catalyst and / or an initiator and / or an activator so as to form, after polymerization, said thermoplastic resin of the family of acrylics and / or acrylates and and / or polyacrylics and / or polyacrylates.

In this case, and in a manner known per se, the reinforcing fibers are introduced into a first impregnation unit where at least one precursor with a very low viscosity impregnates said fibers. Before the polymerization is (too) advanced, the impregnated fibers are drawn through a curing unit through a Caterpillar type pulling system. This polymerization unit which may or may not give its final shape to the profile, has the role of activating and / or accelerate the kinetics of polymerization. In the context of the invention, traditional means of the heated tooling type or air heating tunnel and / or radiation can be used.

The precursors may preferentially be selected from the class of methacrylics and / or methacrylates and / or polymethacrylics (oligomers) and / or polymethacrylates (oligomers) so as to form, after polymerization, a polymer of the class of polymethacrylics and / or polymethacrylates. The initiators may be of the peroxide type.

By way of example, it is possible to use a precursor syrup based on acrylic copolymers and methyl methacrylates (MMA) with a viscosity of 150 mPa.s at 20 ° C., initiated with 2.0% benzoyl peroxide. The reactive approach of polymerizing the final polymer in situ in the middle of the fibers makes it possible to work with liquid precursors of very low viscosity. This choice therefore makes it possible to impregnate a very large quantity of reinforcing fibers and thus to achieve rigidities that are still unequaled for the composite profile. On the formed profiles, a 62 to 65 Gpa modulus in the fiber direction was measured for a unidirectional arrangement of glass fibers. With such a value, the specific rigidity (rigidity / density) of the pultruded section according to the invention (65 / 2.1 = 31) is greater than that of aluminum (70 / 2.7 = 26). that is, higher stiffness can be achieved than aluminum of equal mass.

Furthermore, the invention proposes a coextrusion step preferably carried out "in line", that is to say in the continuity of the pultrusion process, with a polymer of the PVC (polyvinyl chloride) family forming a covering layer deposited around the pultruded profile, said covering layer having chemical bonds with the matrix and / or the surface of the fibers of the pultruded profile so as to be perfectly integral with said pultruded profile, in the manner of a bonding. For the pultruded profile, the choice of precursors in the class of methacrylates and / or methacrylics and especially precursors containing methyl methacrylate (MMA) and leading after polymerization to the formation of a polymethyl methacrylate (PMMA) makes it possible to obtain excellent natural chemical compatibility with PVC Finally PMMA is an amorphous polymer whose glass transition temperature can be around 80-110 ° C. It begins to soften beyond this temperature to become very soft or melted around 180 to 200 ° C. This temperature is much lower than the temperature used with PVC profile welding machines, typically 230-250 ° C.

According to the invention, said PVC cover layer has many advantages. First, it provides a known and accepted aesthetic level in the building sector as well as a proven durability.

In the case of a pultruded profile composed solely of a unidirectional continuous fiber arrangement as claimed in the present invention, this covering layer makes it possible to provide a significant transverse resistance insofar as it is chemically bonded to the profile. pultruded 5 that it covers and that it has properties almost homogeneous and almost isotropic so especially in the transverse direction; direction in which the composite profile is weak. By way of example, transverse properties for the pultruded composite according to the invention are measured in the range of 5 to 8 Gpa and approximately 3 Gpa for the PVC covering layer with a much more ductile behavior. PVC can therefore represent from 40% to 60% of the transverse strength of the composite profile, at a very competitive cost compared to that of the composite. Said covering layer may therefore have a sufficient thickness, of the order of 0.5 to 3 mm, preferably 1 to 2 mm locally.

Still according to the invention, the PVC being a better thermal insulator than the composite, by favoring a PVC thickness greater than that of the composite in the zones likely to have a role of thermal bridge, one can improve the energy performances of the structure which is the subject of the invention.

Finally, said covering layer may have a sufficient thickness, of the order of 0.5 to 3 mm, preferably 1 to 2 mm, so as to contribute, after assembly by welding to the watertightness of the rigid structure thus obtained.

According to the invention it may also have a sufficient thickness, of the order of 0.5 to 3 mm, preferably 1 to 2 mm, so as to contribute, after assembly by welding the profiles to the mechanical strength of the connection between profiles. of the rigid structure thus obtained.

In this case, the thickness of the covering layer will preferably be maximum at the outer zones of the frame, inside and / or outside so as to take up the maximum stresses which are exerted in a movement of spacing or closing the corners of the frame.

In summary, said cover layer, according to the invention, can be advantageously used in the areas of the profile which: - must provide a strong mechanical connection by welding the profiles together - require increased transverse strength at lower cost, - contribute little to the rigidity in longitudinal flexion - are likely to have a role of thermal bridge - are intended to accommodate a screw - can be exposed to a fire, the PVC having a classification M2 or M.

As indicated above, the pultruded profile may advantageously consist of a unidirectional continuous fiber arrangement only or for more restrictive applications (in terms of torsion force, for example) be composed of a continuous fiber arrangement, parallel to the main direction of the profile combined with fibers forming a non-zero angle with the previous for better transverse strength. Another advantage of the invention, related to the very low viscosity of the precursors used in the manufacture of the pultruded profile, is to obtain a very large volume content of reinforcing fibers, greater than 50%, typically 60%. at 80%, and preferably from 65% to 75%, making it possible to achieve the extremely high longitudinal stiffnesses previously mentioned with economically affordable fibers. According to the invention, said pultruded profile has a longitudinal flexural modulus greater than 35 Gpa, typically from 50 Gpa to 68 Gpa, and preferably from 55 Gpa to 65 Gpa. The fibers may be continuous or discontinuous fibers, glass fiber and / or basalt fibers and / or natural fibers of flax fiber and / or hemp fibers and / or bamboo fibers. Carbon fibers, although very expensive can also be used, at least locally to enhance the rigidity. The production method which is the subject of the present invention is especially characterized in that the assembly by welding at least one end of one section to the other to form said structure is obtained by the known technique 3037856 in either the mirror heating. This technique, commonly used by window manufacturers, makes it possible to produce frames quickly and reliably. Thanks to the use of a composite profile whose glass transition temperature is greater than 80 ° and whose complete melting occurs around 180 ° -200 ° C., it is possible to offer a solution: use is stable outdoors in almost all situations of solar exposure (temperatures below 70 ° C generally) 2. that may be suitable for the current method of welding by heated mirror practiced at temperatures generally between 220 ° to 250 ° C 10 Indeed, at these temperatures, under the action of the heating mirror against which the ends of the profiles resulting from the invention are pressed under pressure, the matrix of the pultruded section is softened to a depth greater than 3 mm thus allowing the approximation and the interpenetration of the fibers of the two sections forming an angle of said frame. During the cooling of the assembly, the two sections are rigidly connected. An additional PVC-based cover layer will participate in the welding and strengthen the connection between two profiles. The invention thus allows the production of a rigid frame for the manufacture of a window, or more preferably a frame for the manufacture of a window sash. The frame combines the stiffness advantages of an aluminum frame with the thermal performance of a 100% PVC frame and the fast and reliable welding assembly technique.

Still according to the invention, said structure may be obtained by welding the profiles together by means of an insert which may for example be made of PVC and will be introduced into the profiles at the level of the connection zone so as to strengthen the latter once welded.

Without being limiting, the invention also makes it possible to advantageously address the manufacture of a frame intended to accommodate photovoltaic cells or a frame intended to manufacture the frame of a solar thermal collector. In the first case, the low thermal expansion of the pultruded profile and the electrical non-conductivity are crucial advantages over aluminum.

In the second case, the thermal insulation capacity of the frame of the invention 3037856 will contribute to improving the energy performance of the solar thermal collector. In this case, the formulation of the precursors involved in the composition of the pultruded profile is adapted so as to obtain a glass transition temperature of about 110 ° C. Without limitation, the invention may advantageously provide a solution for structures assembled outdoors bus shelter type or even verandas, glazed facades of buildings of the type "curtain wall" or any other structures, including those intended for accommodate a glazing.

The invention will be better understood, and other features and advantages thereof will become apparent with reference to the accompanying diagrammatic drawings, which show, by way of non-limiting example, possible embodiments of the present invention. .

Figure 1 shows a pultruded section (1) according to the invention. FIG. 2 represents the pultruded section (4) corresponding to the pultruded section (1) covered with a PVC covering layer (2) over its entire external surface.

FIG. 3 shows the pultruded section (4) cut at 45 ° for assembly to form by welding the angle (5) of a structure of the present invention. FIG. 4 shows such an angle (5) formed by the welded assembly of 2 pultruded sections according to the invention.

FIG. 5 shows a frame (6) which is the subject of the present invention; FIG. 6 shows an angle (5) during production by heating with a heating mirror (7). In FIG. 1, the profile is raw, it is that is, it is not covered with the covering layer (2) visible in FIG. 2. The profile has a 62 Gpa module for a unidirectional fiber arrangement. The profile has internal partitions (3) which contribute to its rigidity and thermal insulation. These partitions are generally of less thickness than those located outside the section. The overall dimensions of the profile are of the order of 75 mm.

In Figure 2, the profile (4) has a cover layer (2) covering the entire outer surface of the profile (1) so as to effectively contribute to the sealing of the assembly after welding. It will also be noted that the covering layer (2) has a greater thickness in the external (2a) and internal (2b) zones of the angle (5) formed and illustrated in FIG. 4.

FIG. 4 illustrates an angle (5) whose zone of maximum stress (8), in the case of force opening (in direction A) or closing (in direction B) of the said angle, is reinforced by the presence of an increased thickness of the covering layer (2a) and (2b) Figure 5 shows a frame (6) object of the present invention of rectangular shape in the case presented, and obtained by the welded assembly of 4 sections pultruded according to the invention. It is well understood that the frames object of the present invention are not necessarily of rectangular shape but that they can take any geometric shapes. A frame thus produced, and when it is provided with a glazing has the advantage of having a coefficient of expansion extremely close to that of the glass that composes the glazing. Unlike PVC or aluminum solutions, the glazed structure obtained according to the invention behaves as a single element from the point of view of thermal expansion and thus makes it possible to maintain, irrespective of the temperature variations, a perfect seal at the air. This is a valuable advantage when said structure is a window frame which must ensure a constant level of thermal insulation in a building. FIG. 6 shows an angle (5) in the process of being made by welding to the heating mirror (7) which is inserted between the ends of the profiles to be welded so as to soften and melt their ends about 3 to 5 mm before the contacting the profiles under pressure. The heating time in the case of the invention may last from about 30 to 60 seconds for temperatures of the order of 240 ° C depending on the thicknesses of the various sections of the profiles.

Claims (21)

REVENDICATIONS1. Process for producing a rigid structure obtained by assembling structural sections in which the structural sections are obtained by pultrusion technology and characterized in that: the matrix used for pultrusion production of said profiles (1) is a thermoplastic resin of the family of acrylics and / or acrylates and / or polyacrylics and / or polyacrylates - the angles (5) of connection between the profiles are assembled by welding at least one end of the profiles (1, 4) with another profile (1, 4) of the same section. 2. Production method according to claim 1, characterized in that said thermoplastic pultrusion process is a thermoplastic pultrusion process obtained from a polymer of the class of polymethacrylic and / or polymethacrylates, 3. Production method according to claim 1, characterized in that said thermoplastic pultrusion process is a reactive thermoplastic pultrusion process obtained from a polymerizable syrup, constituted before polymerization of a solution of at least one liquid precursor under form of monomers and / or oligomers and / or thermoplastic polymers solubilized and polymerizable under the action of a catalyst and / or an initiator and / or an activator so as to form after polymerization said thermoplastic resin of the family of acrylics and / or acrylates and / or polyacrylics and / or polyacrylates; 4. Production process according to claim 3, characterized in that one of said precursors of the syrup impregnating the reinforcing fibers is selected from the class of methacrylics and / or methacrylates and / or polymethacrylics (oligomers) and / or polymethacrylates (oligomers) so as to form after polymerization a polymer of the class of polymethacrylic and / or polymethacrylates. 3037856 12 5. Production process according to one of claims 1 to 4, characterized in that said polymer forming the matrix of the pultruded profile has a glass transition temperature between 80 ° C and 110 ° C 5 6. Production process according to one of claims 1 to 5, characterized in that it comprises a step of coextrusion of a polymer forming a covering layer (2, 2a, 2b) of the pultruded profile (1). said covering layer having chemical bonds with the matrix and / or the surface of the fibers of the pultruded profile (1) so as to be perfectly integral with said pultruded profile (1), in the manner of gluing. 7. Production method according to claim 6, characterized in that said polymer forming the covering layer (2, 2a, 2b) is of the family of PVC. 15 8. Production method according to one of claims 6 to 7, characterized in that said covering layer (2, 2a, 2b) covers either partially or in total, said pultruded profile (1). 20 9. Production method according to one of claims 1 to 8, characterized in that said pultruded section (1) is composed of a unidirectional fiber arrangement only. 10. Production process according to claim 9, characterized in that the said fibers are continuous or discontinuous fibers, of glass fiber type and / or basalt fiber and / or natural fibers of flax fiber type and / or hemp fibers and / or an arrangement of these fibers. 11. Production method according to one of claims 1 to 10 characterized in that said pultruded section (1) contains a volume ratio of reinforcing fibers greater than 50%, typically 60% to 80%, and preferably 65%. % to 75% 12.Procédé production according to claim 11 characterized in that said pultruded section (1) has a longitudinal flexural modulus greater than 30 GPA 3037856, typically from 50 Gpa to 68 Gpa, and preferably from 55 Gpa to 65 Gpa 13. Production method according to one of claims 6 to 12, characterized in that said covering layer (2, 2a, 2b) has a sufficient thickness, from 0.5 to 3 mm, preferably from 1 to 2 mm locally, so as to contribute to the transverse strength of the pultruded section. 14. Production method according to one of claims 6 to 13, characterized in that said covering layer (2, 2a, 2b) has a sufficient thickness, from 0.5 to 3 mm, preferably from 1 to 2 mm , so as to contribute after welding assembly to ensure the watertightness of the rigid structure thus obtained. 15 15. Production method according to one of claims 6 to 14, characterized in that said covering layer (2, 2a, 2b) has a sufficient thickness, 0.5 to 3 mm, preferably 1 to 2 mm, so as to contribute, after assembly by welding the profiles to the mechanical strength of the angular connection (5) between profiles of the rigid structure (6) thus obtained. Production process according to claim 15, characterized in that said cover layer (2, 2a, 2b) has a maximum thickness at the outer (2a) and / or inner (2b) regions of the angular connection (5). ) Formed by two profiles of the structure (6) thus obtained so as to form a layer of maximum thickness at the zones (8) of the angular connection (5) most mechanically stressed. 17. Production method according to one of claims 1 to 16, characterized in that the assembly by welding at least one end of a profile to the other is obtained by the known technique of either the heating mirror (7). 18. Production method according to one of claims 1 to 16, characterized in that the assembly by welding at least one end of a profile on the other comprises an insert (8) inserted at the the end of the profiles. 3037856 14 19. Rigid frame obtained from said method according to one of claims 1 to 18, characterized in that it is a frame for receiving a glazing 5 20. Rigid frame obtained from said method according to one of claims 1 to 18, characterized in that it is a frame for the manufacture of a window, and preferably a window sash, 21. Rigid frame obtained from said method according to one of claims 1 to 18, characterized in that it is a frame for accommodating photovoltaic cells or a solar thermal collector.