Method for manufacturing parts made of composite materials using thin-walled molds

Abstract

The present invention relates to a method for producing a thin-walled mold and a part made of a composite material comprising reinforcing fibers and a polymer matrix, the method comprising the following successive steps: placing a closed thin-walled mold, inside which reinforcing fibers are arranged, in a matrix mounted on a press; closing the press; injecting a reactive composition comprising a polymer, or at least one prepolymer, at least one monomer, or a mixture thereof, in a molten state into the closed thin-walled mold; if a reactive composition is used, maintaining the press closed during all or part of the polymerization of the polymer matrix; opening the press and removing the thin-walled mold from the press while maintaining a residual pressure in the mold between 0.7 and 10 bar, preferably between 0.7 and 5 bar; and cooling the mold under said residual pressure.

Description

[Technical field]

[0001] The present invention relates to a method for producing a part made of a reinforced composite material comprising moulding fibres from a reactive composition, the method being carried out in a thin-walled mould. The present invention also relates to a thin-walled mould and its use for producing a composite material. [Background technology]

[0002] The manufacture of composite products by molding is known. The resin transfer molding method known as RTM or "resin transfer molding", and the compression resin transfer molding method known as CRTM and also called ICM (injection compression molding) are commonly used. These methods use temperature-controlled presses. In general, this type of molding is isothermal. This is particularly true in the case of thermosetting resins. However, in the case of thermoplastic resins, it may be advantageous to use non-isothermal methods to promote impregnation of the fibers by reducing the viscosity of the reactive composition or the polymer used to impregnate the fibers. In the case of reactive methods, non-isothermal cycles are also useful to accelerate the reaction rate of polymerization by increasing the temperature of the molding method. The reinforcing fibers are then aligned in the mold of the press. This mold is closed and, if not preheated, the temperature is then increased. A reactive composition based on a polymer or precursor(s) of this polymer is injected in the molten state into the mold. The temperature of the mold is then reduced by cooling. The part obtained is then removed from the mold. The press is therefore equipped with a heating system, typically using resistors or a hot fluid system, and a cooling system, typically using cold water or compressed air circuits.

[0003] It is possible to inject compositions of monomers or even prepolymers. It may be advantageous to use reactive compositions based on one or several prepolymers with sufficient weight. By sufficient weight we mean those weights that make it possible to shorten the polymerization time necessary to obtain the weight of the final polymer, or to reduce the amount of polymerization by-products if the chain extension chemistry used releases them. The prepolymers may be semi-crystalline and, if their molar mass is high enough, their melting point is higher than the crystallization temperature of the final polymer. The prepolymers may be amorphous and, if their molar mass is high enough, their implementation temperature is higher than the glass transition temperature of the final polymer. In these particular cases, it is necessary to carry out a thermal cycle to cool the composite below the injection temperature of the polymer or reactive composition to make it possible to remove it from the mold. For example, in the case of polyamides, the polymerization can be carried out by polycondensation. The reaction rate of this polymerization is relatively slow, with polymerization times approaching one minute only being encountered at temperatures above 250°C.

[0004] It is therefore necessary, optionally, to carry out a non-isothermal moulding cycle in order to allow the precursor(s) of the reactive mixture to polymerise rapidly, in particular at temperatures above 250°C, at least above their melting point, represented by Tm, if they are semi-crystalline, or above their glass transition temperature, represented by Tg, if they are amorphous, and then to cool the mould in order to allow the part to be removed from the mould at a temperature below the crystallisation temperature, represented by Tc for semi-crystalline polymers or Tg for amorphous polymers.

[0005] There is a real need to reduce the duration of these molding processes in order to increase production rates. Thus, one of the intended objectives is to reduce the duration of the mold heating step and to reduce the duration of the mold cooling step. Molding cycles of around one minute are especially in demand.

[0006] Therefore, there is also a real need to reduce the energy costs of this type of process.

[0007] It is possible to solve this problem by increasing the number of heating circuits and the number of cooling channels in the press. However, replacing the old press with a new, more sophisticated press implies high costs. Moreover, this solution does not solve the problem of the high energy costs of the process.

[0008] Additionally, it is important to obtain good quality molded parts having a composition that is uniform. Summary of the Invention

[0009] This technical problem is solved by using a removable mold containing a thin wall. A method for manufacturing a part made of a composite material containing reinforcing fibers and a polymer matrix is ​​provided, the method comprising the following successive steps: - placing a closed thin-walled mold, inside which the reinforcing fibers are arranged, into a matrix mounted on a press; - closing the press; - injecting a polymer or a reactive composition comprising at least one prepolymer, at least one monomer, or a mixture thereof, in a molten state into a closed thin-walled mold; - if a reactive composition is used, maintaining the press closed during all or part of the polymerization of the polymer matrix; - The process of opening the press; - removing the thin-walled mould from the press whilst maintaining a residual pressure in said mould of between 0.7 and 10 bar, preferably between 0.7 and 5 bar; - cooling the mold under the residual pressure. Includes.

[0010] The method according to the invention has the advantage of reducing the energy costs of production. The matrix attached to the press can be maintained at a constant temperature, since the cooling process takes place outside the press. The press used according to the method according to the invention is no longer heated and cooled. Furthermore, the production cycle time can be significantly reduced, which corresponds to the time spent in the press as part of the polymerization, and then cooling takes place outside the press in a latent time. Furthermore, the parts produced by this method show a composition, and in particular a degree of crystallinity, which is the same throughout the part.

[0011] The invention also relates to a thin-walled mould implemented with the method according to the invention and to its use for the production of composite materials. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic representation of certain steps of a method according to the invention. [Diagram 2] FIG. 2 is a cross-sectional view of a thin-walled mold according to the present invention. [Diagram 3] FIG. 2 is a perspective view of a molded part according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Other characteristics, features, objects and advantages of the present invention will become even more apparent after reading the following description.

[0014] It is further indicated that the expressions "between" and "to" used in the description of the present invention must be understood as including each of the limits indicated.

[0015] The invention will now be explained in more detail, in a non-limiting manner, in the following description.

[0016] The method according to the invention is carried out with a thin-walled mold. By thin-walled mold is understood in the context of the present invention a mold comprising two complementary shapes. The thickness of the walls is such that the mold withstands a residual molding pressure higher than the saturated vapor pressure of water at the injection temperature of the reactive composition.

[0017] Method steps The method according to the invention comprises the steps of placing a thin-walled mould in the closed position, in which the reinforcing fibres are arranged, in a matrix mounted on a press. The press is then closed over the mould. The press is maintained in the closed position for a sufficient time to heat the mould to the temperature of the matrix mounted on the press. In general, the duration of the temperature rise of the mould is short, as the mould is designed such that contact with the matrix mounted on the press quickly brings the thin wall of the mould to its temperature. The reactive composition or polymer is then injected into the mould. The press is maintained in the closed position to allow the polymer matrix to impregnate the reinforcing fibres. If a reactive composition is used, all or part of the polymerization may take place during the time that the thin-walled mould is maintained in the press. In this case, the duration of this step depends on the reactive composition used. The press is then opened to allow removal of the mould. After removal from the press, the mould is allowed to cool before the demolding step.

[0018] Each of the method steps will be disclosed in detail below.

[0019] Reinforced fiber insert The reinforcing fibers can be aligned in a thin walled mold by a simple laying operation or can be aligned in the form of a preform.

[0020] According to a particular embodiment of the invention, the reinforcing fibers can be made in the form of a preform. They are then mixed with an adhesive resin, otherwise known as a preform binder, and then optionally molded by compression directly in a suitable mold or even in a thin-walled mold according to the invention to produce a preform. This latter has the advantage of being easily handled. This preform can then be easily aligned in the thin-walled mold if it is not already in the thin-walled mold.

[0021] Depending on the reinforcing fibers used and on the nature of the polymer or reactive composition used for molding, the preforming step can be carried out at temperatures between 80° C. and 320° C. The preform binder is selected to withstand the injection temperatures applied.

[0022] This optional preforming step can be carried out in a circular device arranged on an axis of rotation. Preferably, the axis of rotation of the circular device is parallel to the axis of rotation of the press. The circular device can be arranged close to the press. For example, a carousel can be used.

[0023] According to certain embodiments of the invention, a robotic arm can be used to align the preforms within the thin wall mold as would be done in a separate mold.

[0024] The thin walled mold is maintained in a closed position throughout the entire molding process, from placement of the mold in the press to demolding.

[0025] This closed position may be maintained by a vacuum filling system or by a conventional mechanical closure system.

[0026] Preferably, the thin-walled mould is equipped with a vacuum filling system providing a residual pressure between 0.7 and 10 bar, preferably between 0.7 and 5 bar. Advantageously, said residual pressure is between 0.7 and 0.9 bar.

[0027] Advantageously, when the residual pressure is between 0.7 and 0.9 bar, the polymerization is carried out by polyaddition or by radical polymerization or by nucleophilic substitution.

[0028] Advantageously, when the thin-walled mould comprises a mechanical closing system, said residual pressure is between 0.9 and 10 bar, preferentially between 0.9 and 5 bar.

[0029] Optional preliminary degassing step before installing the die in the press The method according to the invention may also comprise a degassing step in the thin-walled mold before the step of placing the mold in the press. This makes it possible to maintain the closure of the thin-walled mold during its movement under the press. This also makes it possible to exclude in the thin-walled mold all or part of the air and / or any other substance, the presence of which may have a detrimental effect on the manufacture of the composite part. In fact, the degassing of the fibres in the closed thin-walled mold is carried out before starting the injection of the polymer or reactive composition, making it possible to reduce the porosity associated with air bubbles.

[0030] According to a particular embodiment of the invention, the thin-walled mold is provided with a degassing system, which is a gas extraction system present in the housing of the mold, including at least one pump and one or several vents. When using a polymerization chemistry by polycondensation, the vacuum filling system is closed to allow the polymer or reactive composition to be injected under conditions that limit polymerization. This also applies if the polymer or reactive composition is sufficiently fluid at the injection temperature that it is introduced into the vent of the mold used for degassing, risking blocking the vent.

[0031] The degassing may be carried out at a vacuum ranging from 0.010 to 0.950 bar, preferably from 0.700 to 0.900 bar relative to atmospheric pressure.

[0032] Installation of thin-walled dies in a press The method involves placing a closed thin-walled die, within which reinforcing fibers are arranged, into a matrix mounted on a press.

[0033] According to another particular embodiment of the invention, a robotic arm can be used to place the thin wall molds in the matrix of the molding press. A combination of carousel and robotic arm is also possible.

[0034] Press closure The thin wall mold is then placed into the matrix of the press and the press is closed. The press is maintained in the closed position for a sufficient time such that the matrix of the press gives its temperature to the walls of the mold. The thickness of the thin wall of the mold is such that there is high thermal conduction between the matrix of the press and the walls of the mold.

[0035] Optional preliminary degassing step after installation of the die in the press The method according to the invention may also comprise a degassing step in the thin-walled mould before the injection step. The application of this degassing makes it possible to eliminate in the thin-walled mould all or part of the air and / or any other substances, the presence of which may have a detrimental effect on the manufacture of the composite part. In fact, the degassing of the fibres in the closed thin-walled mould is carried out before starting the injection of the polymer or reactive composition, making it possible to reduce the porosity associated with the air bubbles. The thin-walled mould is preferably equipped with a vacuum filling system making it possible to carry out this degassing. After the degassing of the mould, the vacuum filling system is closed to allow the polymer or reactive composition to be injected.

[0036] Injection of polymer or reactive composition The method according to the invention then comprises a step of injecting, in the molten state, a reactive composition comprising a polymer or at least one prepolymer, at least one monomer, or a mixture thereof, into the closed thin-walled mould. Advantageously, the duration of the injection step is less than 15 seconds. Preferably, the duration of this step is between 1 and 10 seconds. When using a reactive composition, a short injection time makes it possible to limit the simultaneous or subsequent polymerization of the reactive composition during this step, which improves the impregnation of the fibres.

[0037] In a particular embodiment corresponding to RTM, the injection of the polymer or reactive composition into the closed mold and the impregnation of the reinforcing fibers are simultaneous. In this embodiment, after an optional initial degassing, the injection and impregnation are carried out without degassing, i.e. no vacuum is applied at the degassing hole of the degassing system.

[0038] According to another embodiment corresponding to CRTM, after an optional initial degassing, preferably without degassing during injection, the polymer or reactive composition is injected into a mold comprising an open compression chamber, and then, during the compression caused by closing the compression chamber, without degassing during said compression, a pressure of preferably between 10 and 70 bar, and even more preferentially between 40 and 60 bar, is applied to the mold to carry out impregnation of the reinforcing fibers with the reactive composition, which pressure improves the impregnation of the fibers with the reactive composition.

[0039] According to a particular embodiment using a reactive composition, the temperature applied to the mold during the polymerization step is above the melting point Tm of the prepolymer, preferably at least 5°C above.

[0040] According to another embodiment using a reactive composition, the polymerization temperature is above the melting point of the prepolymer with the highest melting point, preferably at least 5°C above.

[0041] Preferably, the matrix of the press is maintained at a constant temperature between 200 and 350°C, in particular between 230 and 320°C, more particularly between 250 and 320°C.

[0042] Process for keeping the mold closed Depending on the reactive composition used, the duration of this step for keeping the press closed will depend on the conversion of prepolymer to polymer or monomer to prepolymer and then to polymer. Preferably, the duration of this step corresponds to the time required to double the molecular weight of the prepolymer.

[0043] Depending on the reactive composition used, it is possible to envisage the fact that polymerization starts during injection, in the case of RTM, or during injection compression, in the case of CRTM of the composition, and then continues during cooling. This embodiment reduces the time spent on the press, and therefore makes it possible to significantly increase the production rate of parts, without significantly increasing costs.

[0044] During the maintaining step, degassing may be performed, preferably by maintaining a pressure of less than 5 bar. This degassing may be performed by applying a vacuum in the range of 0.010 to 0.950 bar, preferably 0.700 to 0.900 bar, relative to atmospheric pressure. The vent holes of the system placed in the mould have a sufficiently small diameter and the reactive composition is sufficiently viscous at the vent holes to create a pressure loss that prevents the reactive composition from passing through the vent holes and exiting the mould.

[0045] Removal of the mold from the press The press is then opened. The thin walled die is then removed from the press. During these two steps, the thin walled die is kept in a closed position by a vacuum facilitating a pressure of 0.700-0.900 bar.

[0046] The process of keeping the die closed and cooling outside the press The method then includes a step of maintaining the closure of the mold outside the press, optionally to complete the polymerization of the polymer matrix from the reactive composition. This pressure is also called "holding pressure". Advantageously, this pressure is lower than the pressure applied during the impregnation step. In a particularly preferred manner, this pressure is higher than the saturated vapour pressure of water in the case of polycondensation. By "saturated vapour pressure of water" is understood the saturated vapour pressure of dissolved water in the matrix of the composite obtained after the polymerization of the reactive composition at the temperature at which said polymerization is carried out. The application of a holding pressure higher than the saturated vapour pressure of water prevents the water produced as a by-product during the polymerization from forming bubbles, which would deteriorate the quality of the composite. Preferably, the pressure applied during the step of maintaining closure is between 3 and 7 bar, even more preferentially between 4 and 6 bar.

[0047] According to a particular embodiment, the degassing is applied for substantially the entire duration of the step of keeping the mold closed outside the press, but the pressure applied during the polymerization step must be low enough so that the reactive composition does not pass through the degassing holes during the application of the degassing.

[0048] The duration of the step of maintaining the closure of the mould outside the press depends on the reaction rate of the polymerization of the reactive composition, this duration is preferably less than 15 minutes, preferably less than 10 minutes and more preferentially less than 5 minutes.

[0049] cooling By heat conduction with the surrounding air through the thin wall, by heat conduction with the cold environment in a cold room, or even in a cold molding apparatus, the thin wall mold is allowed to cool and the ambient temperature can reach a temperature below the crystallization temperature (Tc) of the polymer being formed.

[0050] According to another embodiment, the cooling consists of placing the thin-walled mold in a so-called cold forming apparatus, which is regulated at a temperature below the crystallization temperature Tc of the polymer being formed, under a residual pressure between 0.7 and 10 bar, preferably between 0.7 and 5 bar.

[0051] Advantageously, the cooling step is carried out in a cold forming apparatus.

[0052] Removal from the mold The composite part is then removed from the thin wall mold.

[0053] Installation and removal According to a preferred embodiment of the invention, the steps of mounting and removing from the thin-walled mould may be carried out using a robotic arm, before and / or after the step of injecting the polymer or reactive composition. In fact, the use of a robotic arm in the method according to the invention makes it possible to maintain the matrix of the press at a relatively high and constant temperature, avoiding endangering the operators handling these devices.

[0054] As regards the steps prior to placing the mould in the press, it is possible to use a circular device arranged on the axis of rotation, which makes it possible to move the mould from the press, for example to a cold forming apparatus, for the cooling step.

[0055] According to a particular embodiment of the invention, it is possible to envisage one circular device in which the mould containing only the reinforcing fibres (before moulding) and the mould containing the composite material to be cooled (after moulding) will be placed.

[0056] Polymer Matrix Composite materials include reinforcing fibers and a polymer matrix.

[0057] According to one embodiment, the polymer matrix comprises: - polymers and copolymers from the family of aliphatic, cycloaliphatic or semi-aromatic polyamides (PA), also called polyphthalamides (PPA); - polyureas, in particular aromatic polyureas; - polyacrylates, more particularly polymers and copolymers from the acrylic family, such as polymethyl methacrylate (PMMA) or its derivatives; - polymers and copolymers derived from the family of polyaryletherketones (PAEK), such as poly(etheretherketones) (PEEK) or poly(aryletherketoneketones) (PAEKK), such as poly(etherketoneketones) (PEKK), or derivatives thereof; - aromatic polyetherimide (PEI), - polyarylsulfides, in particular polyphenylsulfide (PPS), - polyarylsulfides, in particular polyphenylene sulfone (PPSU), - polyolefins, especially polypropylene (PP); - Polylactic acid (PLA), - Polyvinyl alcohol (PVA), fluorinated polymers, in particular polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or polychlorotrifluoroethylene (PCTFE), and mixtures thereof You can choose from.

[0058] Preferably, the polymer matrix is ​​selected from polyamide, polyester, polyamideimide, polyamide-ether, polyacrylic, polyolefin, phenylene polysulfide, polyether-imide matrices.

[0059] According to one advantageous embodiment, the polymer matrix is ​​a polyamide matrix.

[0060] According to one embodiment, the polymer matrix is ​​a thermoplastic matrix.

[0061] According to certain embodiments, the polymer matrix is ​​a semi-crystalline matrix, which provides the composite with significantly improved mechanical performance, such as creep and fatigue resistance, especially at elevated temperatures, compared to amorphous polymers.

[0062] Advantageously, the polymer matrix has a glass transition temperature Tg of at least 80° C., preferably at least 90° C., more preferentially at least 100° C. and even more preferably at least 120° C. A glass transition temperature of 80° C. or higher ensures good mechanical properties of the composite throughout the entire temperature range of use, for example up to 90° C. for wind, up to 100° C. for automotive and up to 120° C. for aeronautics.

[0063] According to an even more advantageous embodiment, the polymer matrix is ​​semi-crystalline and has a melting point Tm above 200°C, preferably above 220°C. A melting point above 200°C provides compatibility with electrophoretic processing, particularly in the automotive industry. Preferably, the melting point Tm is equal to or lower than 320°C, even more preferentially below 290°C. A melting point above 320°C requires the use of the composite at higher temperatures, which imposes constraints on the moulding material and the associated heating system, leading to excessive energy consumption. The use of such high temperatures increases the risk of thermal degradation of the polymer, leading to a deterioration of the properties of the final matrix and therefore of the composite and the properties of the final composite part.

[0064] According to one embodiment, the polymer matrix has a crystallization temperature Tc such that the difference Tm-Tc between the melting point Tm and the crystallization temperature Tc of the matrix does not exceed 60°C, preferably does not exceed 50°C, more particularly does not exceed 40°C.

[0065] According to one variant, the enthalpy of crystallization of the polymer matrix is ​​between 10 and 55 J / g.

[0066] According to a particular variant, the enthalpy of crystallization of the polymer matrix is ​​between 40 J / g and 55 J / g, preferably between 20 and 35 J / g.

[0067] The mechanical performance or high temperature mechanical strength of a composite material may be evaluated by the change in bending stress at break in the direction of the fibers (or "maximum strength at 0°") between room temperature (23°C) and 100°C, with good high temperature mechanical strength corresponding to maintaining at least 75% of the mechanical performance in terms of stress at break relative to room temperature (23°C).

[0068] According to one embodiment of the present invention, the polymer matrix is ​​prepared by bulk polymerization of a reactive composition comprising at least one prepolymer, at least one monomer, or a mixture thereof in the molten state.

[0069] Advantageously, the polymer matrix has a number average molar mass of more than 10 000 g / mol, preferably between 10 000 and 40 000 g / mol and even more preferentially between 12 000 and 30 000 g / mol.

[0070] According to one embodiment, the polymer matrix is ​​a polyamide matrix comprising units derived from the following monomers: terephthalic diacid, isophthalic diacid, adipic acid, sebacic acid, dodecanoic acid, 1,10-decamethylenediamine, 1,6-hexamethylenediamine, 2-methylpentamethylenediamine (MPMD), a mixture of 2,2,4 and 2,4,4-trimethylhexanediamine (TMD), 2-methyloctanediamine (8M), nonanediamine, 4,4'-diaminodicyclohexylmethane (PACM) m-xylylenediamine (MXD), 1,3-bis(aminomethyl)cyclohexane (1,3 BAC), 1,4-bis(aminomethyl)cyclohexane (1,4 BAC), caprolactam, 11-aminoundecanoic acid, 12-aminolauric acid, and / or lauryllactam.

[0071] According to an advantageous embodiment, the polymer matrix is ​​a polyamide matrix selected from PA 11 / 10T, PA5T / 10T, PA 11 / 5T / 10T, PA 6T / 10T, PA 11 / 6T / 10T, PA MPMDT / 10T, PA MDXT / 10T, PA BACT / 10T, PA 11 / BACT, PA 11 / BACT / 10T, PA 6 / 6T, PA 66 / 6T, PA 6I / 6T, PA MPMDT / 6T, PA 6T / 10T, PA 8MT / 9T, PA TMDT / 10T, PA PACM12, PA BACT / 6T, PA 11 / BACT / 6T, PA BACT / 10T / 6T, PA MXD6 and PA MXD10, the BAC being advantageously 1,3 BAC.

[0072] Reactive Composition The reactive composition comprises one or several monomers that are susceptible to react alone or with other monomers, or one or several prepolymers that are susceptible to react together during the polymerization process, so as to obtain the matrix disclosed above.

[0073] In an advantageous embodiment, the prepolymer(s) is a polyamide prepolymer.

[0074] Each prepolymer is itself a polymer (homopolymer or copolymer) and exhibits a number-average molar mass smaller than that of the matrix. According to one embodiment, the prepolymers contained in the reactive composition have a number-average molar mass between 500 and 10 000 g / mol, preferably between 750 and 6000 g / mol and more preferentially between 750 and 3000 g / mol.

[0075] According to one embodiment, when at least two prepolymers are used, they exhibit substantially the same number-average molar mass, "substantially the same number-average molar mass" meaning that the difference between the two masses is less than 30%.

[0076] According to a first embodiment, the composition comprises at least a first polyamide prepolymer A1 having two amine functional groups and at least a second polyamide prepolymer A2 having two carboxyl functional groups that are co-reactive with the amine functional groups of the first polyamide prepolymer. The backbones of the prepolymers A1 and A2 may be of the same nature (i.e. have the same composition in the repeating units) or of different nature. Preferably, they are of the same nature.

[0077] According to a second embodiment, the composition comprises at least one polyamide prepolymer A3 having one amine and one carboxyl functional group which are mutually co-reactive. In this embodiment, the composition can comprise one polyamide prepolymer having one amine and one carboxyl functional group which are mutually co-reactive, or even several different prepolymers each having one amine and one carboxyl functional group. In this latter case, the skeletons of the different prepolymers A3 can be of the same nature (so that the different prepolymers A3 are only distinguished by their distinct number-average molar masses) or of different nature.

[0078] According to a third embodiment, the composition comprises at least one prepolymer A1 (as disclosed above) having two amine functional groups, and at least one polyamide prepolymer A2 (as disclosed above) having two carboxyl functional groups.

[0079] According to a fourth embodiment, the composition comprises at least one prepolymer A1 having two amine functional groups (as disclosed above) or at least one polyamide prepolymer A2 having two carboxyl functional groups (as disclosed above), and at least one chain extender of formula Y-A'-Y, in which Y is a group carrying a functional group capable of reacting with at least one functional group of said prepolymers A1 and / or A2 by polyaddition or polycondensation; - A' is a hydrocarbon biradical.

[0080] If the prepolymer has two NH2 functional groups (amine functional groups): - Chain extender Y-A'-Y is Y is selected from the group of maleimides, optionally blocked isocyanates, oxazinones and oxazolinones, preferably from oxazinones and oxazolinones, -- A', ---- a covalent bond between two functional groups Y when Y is an oxazinone or oxazolinone group, or ---- an aliphatic hydrocarbon chain, or an aromatic and / or alicyclic hydrocarbon chain, the latter two of which contain at least one ring having 5 or 6 carbon atoms, which may be substituted, and optionally the aliphatic hydrocarbon chain has a molecular weight of 14 to 200 g.mol -1 an aliphatic hydrocarbon chain, or an aromatic and / or alicyclic hydrocarbon chain, having a molecular weight of is a carbon spacer or carbon group selected from Such a chain extender is or the chain extender Y-A'-Y is a chain extender in which Y is a caprolactam group and A' may be a carbonyl group, such as carbonyl biscaprolactam, or A' may be a terephthaloyl or isophthaloyl, or a diepoxide selected from optionally substituted aliphatic, cycloaliphatic, or aromatic diepoxides.

[0081] Examples of aliphatic diepoxides include diglycidyl ethers of aliphatic diols, aromatic diepoxides include diglycidyl ethers of bisphenol A, such as bisphenol A diglycidyl ether (BADGE), and cycloaliphatic diepoxides include diglycidyl ethers of cycloaliphatic diols or hydrogenated bisphenol A. More generally, suitable examples of diepoxides according to the invention include bisphenol A diglycidyl ether (BADGE) and its hydrogenated derivatives (cycloaliphatic), bisphenol F diglycidyl ether, tetrabromobisphenol A diglycidyl ether or hydroquinone diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ethers of Mn<500. diglycidyl ether, polypropylene glycol diglycidyl ether of Mn<500, polytetramethylene glycol diglycidyl ether of Mn<500, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A polyethylene glycol diglycidyl ether of Mn<500, bisphenol A polypropylene glycol diglycidyl ether of Mn<500, diglycidyl esters of dicarboxylic acids such as terephthalic acid or the glycidyl esters of epoxidized diolefins (dienes) or fatty acids with double epoxidized ethylenic unsaturation, diglycidyl 1,2 cyclohexanedicarboxylate, and mixtures of the aforementioned diepoxides. or said chain extender Y-A'-Y has a cyclic anhydride group Y, preferably this extender is chosen from cycloaliphatic and / or aromatic dianhydrides of carboxylic acids, more preferentially ethylene tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, hexa fluoroisopropylidenebisphthalic dianhydride, 9,9-bis(trifluoromethyl)xanthenetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 3,3',4,4'-diphenylethertetracarboxylic dianhydride, or a mixture, where A' is a carbon spacer (radical) as defined above.

[0082] When the prepolymer has two COOH functional groups (carboxy functional groups), the chain extender Y-A'-Y is: - Y is a chain extender selected from the group of diepoxides selected from oxazolines, oxazines, imidazolines or aziridines such as 1,1'-iso- or terephthaloyl-bis(2-methylaziridine) or optionally substituted aliphatic, cycloaliphatic or aromatic diepoxides. Examples of aliphatic diepoxides include diglycidyl ethers of aliphatic diols, aromatic diepoxides include diglycidyl ethers of bisphenol A such as bisphenol A diglycidyl ether (BADGE) and cycloaliphatic diepoxides include diglycidyl ethers of cycloaliphatic diols or hydrogenated bisphenol A. More generally, suitable examples of diepoxides according to the invention are bisphenol A diglycidyl ether (BADGE) and its hydrogenated derivatives (alicyclic), bisphenol F diglycidyl ether, tetrabromobisphenol A diglycidyl ether or hydroquinone diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ethers with Mn<500. diglycidyl ether, polypropylene glycol diglycidyl ether of Mn<500, polytetramethylene glycol diglycidyl ether of Mn<500, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A polyethylene glycol diglycidyl ether of Mn<500, bisphenol A polypropylene glycol diglycidyl ether of Mn<500, diglycidyl esters of dicarboxylic acids such as terephthalic acid or the glycidyl esters of epoxidized diolefins (dienes) or fatty acids with double epoxidized ethylenic unsaturation, diglycidyl 1,2 cyclohexanedicarboxylate, and mixtures of the aforementioned diepoxides. - A' is a carbon spacer (radical) as defined above.

[0083] In all of the above descriptions, A' is in particular an alkylene biradical, such as -(CH2) where m ranges from 1 to 14, preferably from 2 to 10. m -, or substituted or unsubstituted cycloalkylene and / or arylene biradicals such as benzenearylenes, for example o-, m-, p-phenylene or naphthalene-based arylenes, and the like.

[0084] According to one embodiment, the reactive composition is prepared by mixing at least two prepolymers.

[0085] Preferably, the method comprises a step of preheating the prepolymer(s) to a temperature above the melting point of the prepolymer. Preferably, the applied heating temperature is between 200 and 350°C, in particular between 230 and 320°C, more particularly between 250 and 320°C.

[0086] Preferably, at least two prepolymers are used, in which case the process includes mixing the prepolymers in the molten state, for example by a static mixer, a dynamic mixer, or a RIM ("reaction injection molding") type mixer, to form a composition intended to be injected into a mold.

[0087] The prepolymers (especially polyamides) may be prepared by polymerization from the respective monomers in a manner known to those skilled in the art, and the polymerization may be interrupted once the desired molar mass has been obtained, for example by checking the hydraulic pressure (progress of the reaction) and / or the amount of monomers. For example, an excess of diamine monomer or an excess of dibasic acid monomer may be used to obtain prepolymers A1 and A2 with two amine functions or two carboxyl terminal functions.

[0088] The preparation of such reactive prepolymers is disclosed, for example, in WO 2014 / 064375.

[0089] Preferably, the prepolymer contained in the reactive composition and the polymer matrix obtained by polymerization of said reactive composition have the same composition in units derived from monomers a), b) and optionally c).

[0090] According to a particular embodiment, the prepolymers A1 and / or A2 or the prepolymers A3 comprise units deriving from the monomers: a) terephthalic acid, b1) 1,10-decamethylenediamine, and b2) MPMD or MXD.

[0091] According to another particular embodiment, the prepolymers A1 and / or A2 or the prepolymers A3 comprise units deriving from the monomers: a) terephthalic acid, b1) 1,10-decamethylenediamine and b2) 1,3-bis(aminomethyl)cyclohexane (1,3 BAC), 1,4-bis(aminomethyl)cyclohexane (1,4 BAC) or mixtures thereof, in particular 1,3-bis(aminomethyl)cyclohexane (1,3 BAC).

[0092] According to another particular embodiment, the prepolymers A1 and / or A2 or the prepolymers A3 comprise units deriving from monomers c), this latter being chosen from 11-aminoundecanoic acid, 12-aminolauric acid and lauryllactam.

[0093] According to another more specific embodiment, the prepolymers A1 and / or A2 or the prepolymers A3 comprise units derived from the monomers: a) terephthalic acid, b1) 1,10-decamethylenediamine, b2) 1,6-hexamethylenediamine, or MPMD, or MXD, or 1,3 BAC, or 1,4 BAC, and c) 11-aminoundecanoic acid, or 12-aminolauric acid, or lauryllactam.

[0094] According to an even more specific embodiment, the prepolymers A1 and / or A2 or the prepolymers A3 comprise units derived from the monomers: a) terephthalic acid, b1) 1,10-decamethylenediamine, b2) 1,6-hexamethylenediamine, or MPMD, or MXD, or 1,3 BAC, or 1,4 BAC, and c) 11-aminoundecanoic acid.

[0095] According to even more specific embodiments, the prepolymers A1 and / or A2 or the prepolymers A3 comprise units derived from the monomers: a) terephthalic acid, b1) 1,6-hexamethylenediamine, b2) MPMD, or MXD, or 1,3 BAC, or 1,4 BAC, and c) 11-aminoundecanoic acid.

[0096] According to an even more specific embodiment, prepolymer A1 and / or A2 or prepolymer A3 comprises units derived from the monomers: a) terephthalic acid, b1) 1,10-decamethylenediamine, b2) 1,6-hexamethylenediamine, and c) 11-aminoundecanoic acid.

[0097] According to another particular embodiment, the prepolymers A1 and / or A2 or the prepolymers A3 comprise units deriving from the monomers a) terephthalic acid, b1) 1,10-decamethylenediamine, b2) 1,6-hexamethylenediamine, and c) lauryllactam.

[0098] According to an even more specific embodiment, the prepolymers A1 and / or A2 or the prepolymers A3 comprise units derived from the monomers: a) terephthalic acid, b1) 1,6-hexamethylenediamine, b2) MPMD, or MXD, or 1,3 BAC, or 1,4 BAC, and c) lauryllactam.

[0099] The reactive composition may also include a monomer, said monomer being a precursor to said prepolymer as described above.

[0100] The reactive composition may comprise at least one carbon nanofiller. Preferably, the nanofiller is selected from carbon black, graphene, carbon nanofibrils, and carbon nanotubes.

[0101] The reactive composition may also contain one or more other additives.

[0102] The additive may be an additive that absorbs UV, infrared (IR), microwave, or induced radiation. Such additives can be used, for example, to reheat the composite or preform or composite part prior to a complementary deformation operation, in particular thermostamping or overmolding.

[0103] The additives may also be specific additives such as thermal stabilizers, in particular these stabilizers are antioxidants against thermo-oxidation and / or photo-oxidation of the polymer in the thermoplastic matrix, and are organic or inorganic stabilizers.

[0104] The expression "organic stabilizer" or more generally "combination of organic stabilizers" refers to primary antioxidants of the phenolic type, secondary antioxidants of the phosphite type, for example liquid phosphites of the doverphos® type, and also optionally other stabilizers, such as HALS, which stands for hindered amine light stabilizers (for example Ciba's Tinuvin 770), UV inhibitors (for example Ciba's Tinuvin 312), phenolic stabilizers or phosphorus stabilizers. Aminic antioxidants, such as Crompton's Naugard 445, or even multifunctional stabilizers, such as Clariant's Nylostab S-EED, may also be used.

[0105] The organic stabilizers present are not limited to this list: - Phenolic antioxidants, such as Ciba's Irganox 245, Irganox 1010, Irganox 1098, Ciba's Irganox MD1024, Great Lakes' Lowinox 44B25, Adeka Palmarole's ADK Stab AO-80, - phosphorus stabilizers, such as phosphites, e.g. Ciba's Irgafos 168; - UV absorbers, such as Ciba's Tinuvin 312 or titanium dioxide TiO2, - As mentioned above, HALS, - amine type stabilizers, such as Crompton's Naugard 445, or even hindered amine type, such as Ciba's Tinuvin 770, - Multifunctional stabilizers, such as Clariant's Nylostab S-EED You can choose from.

[0106] Mixtures of two or more of these organic stabilizers may of course be envisaged.

[0107] The expression "inorganic stabilizer" refers to stabilizers containing copper or metal oxides, as disclosed in the document US 2008 / 0146717. Examples of inorganic stabilizers include copper halides and copper acetate, or iron oxides, such as FeO, Fe2O3, Fe3O4, etc., or mixtures thereof. Secondly, other metals such as silver can be considered in some cases, but they are known to be less effective.

[0108] These inorganic stabilizers are more particularly employed when the structure must have improved long-term heat resistance in hot air, especially at temperatures above 100° C., or even above 120° C., since they tend to prevent the breakage of the polymer chains.

[0109] More particularly, "copper-containing stabilizer" is understood to mean a compound which contains at least one copper atom, in particular ionizable or in ionic form, for example in the form of a complex.

[0110] Copper-containing stabilizers can be selected from copper chloride, cuprous chloride, copper bromide, copper bromide, copper iodide, copper iodide, copper acetate, and copper (I) acetate. In combination with copper-containing stabilizers, halides, acetates of other metals, such as silver, can be mentioned. These copper-based compounds are typically used in combination with alkali metal halides, especially potassium. A well-known example is a mixture of CuI and KI, with the CuI:KI ratio typically between 1:5 and 1:15. An example of such a stabilizer is Ciba's Polyadd P201.

[0111] Further details regarding copper-containing stabilizers can be found in U.S. Patent No. 2,705,227.More recently, copper-containing stabilizers have appeared, such as copper complexes, for example Brueggemann's Brueggolen H3336, H3337, H3373, and the like.

[0112] Advantageously, the copper-based stabilizer is selected from copper halides, copper acetate, copper halides or copper acetate in a mixture with at least one alkali metal halide, and mixtures thereof, preferably a mixture of copper iodide and potassium iodide (CuI / KI).

[0113] The additive may also be an impact modifier consisting of a polymer having a flexural modulus of less than 100 MPa, measured according to the ISO 178 standard, and a glass transition temperature Tg (measured near the inflection point of the DSC thermogram according to the standard 11357-2:2013) of less than 0° C., in particular a polyolefin, with or without bonded Peba (polyether block amide), having a flexural modulus of <200 MPa.

[0114] The polyolefins of the impact modifier may be functionalized or non-functionalized, or may be a mixture of at least one functionalized polyolefin and / or at least one non-functionalized polyolefin.

[0115] The additives may also be halogen-free flame retardants, such as those disclosed in US 2008 / 0274355, in particular metal salts selected from metal salts of phosphinic acids and metal salts of diphosphinic acids, polymers containing at least one metal salt of phosphinic acids, polymers containing at least one metal salt of diphosphinic acids, or red phosphorus, antimony oxide, zinc oxide, iron oxide, magnesium oxide, or metal borates, such as zinc borate, or melamine pyrophosphate and melamine cyanurate. They may also be halogenated flame retardants, such as brominated or polybrominated polystyrene, brominated polycarbonate, or brominated phenols.

[0116] Advantageously, the additives are selected from antioxidants, heat stabilizers, UV absorbers, light stabilizers, impact modifiers, lubricants, inorganic fillers, flame retardants, nucleating agents, in particular inorganic fillers such as talc, and colorants.

[0117] The nanofillers and additives can be added to the polymer(s) or prepolymer(s) in the molten state to obtain the polymer or reactive composition before injection into the mold.

[0118] Reinforced Fiber The reinforcing fibres used in the process according to the invention can be chosen from inorganic fibres, preferably glass, carbon or basalt fibres, in particular glass or carbon fibres, or from synthetic fibres, preferably aramid fibres or polyaryletherketone fibres, or mixtures thereof.

[0119] Advantageously, the fibres have a length such that the L / D ratio is greater than 1,000, preferably greater than 2,000, L being the average length of the fibres and D being their average diameter, measured by methods well known to those skilled in the art, in particular by microscopy.

[0120] The fibres may represent 45-80% by volume of the composite material, preferably 50-70%.

[0121] Thin wall mold The subject of the invention is also a mould comprising two parts, preferably of complementary shape, intended to be assembled, a first member including a groove around an edge of the member; a second member including a protruding rib around an edge of the member; and It consists of the locations of the grooves and ribs are selected to mate with one another when the mold is in a closed position; - at least one of the members includes at least one opening having an axis perpendicular to a surface of the member; a sealant is disposed in the groove of the first member; - the part has a thickness that withstands a residual molding pressure that is greater than the saturated vapor pressure of water at the injection temperature of the reactive composition; - The material has thermal conductivity It is characterized by:

[0122] Preferably, the part can withstand a residual moulding pressure of between 0.7 and 5 bar.

[0123] The mold comprises openings with an axis perpendicular to the surface of the part. These openings are generally called injection points. They allow the injection of the polymer or reactive composition in the molten state into the mold. The number of openings in the part(s) of the mold depends on the surface area of ​​the part(s). The two parts of the mold, the lower part and the upper part, are provided with at least one injection point.

[0124] The mould may be equipped with a vacuum filling system making it possible to maintain the mould in a closed position when not in the press. Preferably, the vacuum filling system allows a pressure of 0.7 bar to 0.9 bar.

[0125] The mould may be equipped with a mechanical system making it possible to maintain it in a closed position when not in the press, said mechanical system making it possible to withstand an internal pressure between 0.7 and 10 bar, preferably between 0.7 and 5 bar.

[0126] According to one particular embodiment of the invention, the thin-walled mold is provided with a degassing system, which is a gas extraction system present in the mold housing, comprising at least one pump and one or several degassing holes opening towards the outside on the mold housing.

[0127] According to one particular embodiment of the invention, the first part including the groove and the seal is provided with cooling channels making it possible to cool the seal, said cooling channels may contain a cold liquid or may even be connected to a cooling system using cold water or compressed air.

[0128] Preferably, the thin walled mold is made of a thermally conductive material that allows maximum heat transfer from the press to the reactive composition injected into the mold in a molten state.

[0129] Preferably, the thermal conductivity of the wall (λ) is 10 W.m -1 .K -1 Less than or equal to 0.1 and preferably 10 W.m -1 .K -1 Between 0.3 and 1 W.m -1 .K -1 It is between.

[0130] The thermal conductivity measurements of the materials are carried out according to the hot disk method, such as that described in the ISO 22007-2 standard.

[0131] According to a particular embodiment of the invention, the thin walled mold is made of steel.

[0132] The mould may also include one or more means for gripping or grasping which facilitates easy handling of the mould.

[0133] Preferably, the mould according to the invention comprises: a first member including a groove extending along an edge of the member, a seal disposed in the groove, and a cooling channel that allows cooling of the seal disposed in the groove of the first member; a second member including a protruding rib around an edge of the member; and Including, the locations of the grooves and ribs are selected to mate with one another when the mold is in a closed position; - at least one of the members includes at least one opening having an axis perpendicular to a surface of the member; - the part has a thickness that withstands a residual molding pressure that is greater than the saturated vapor pressure of water at the injection temperature of the reactive composition; - The member has thermal conductivity; For molds - a degassing system; - With vacuum filling system or mechanical closing system is provided.

[0134] Other objects, advantages and features will become apparent from the following description given purely by way of illustrative example and made with reference to the accompanying drawings, in which:

[0135] Figure 1 is a schematic representation of certain steps of the method according to the invention. The steps of injecting the polymer or reactive composition: step 1A, and cooling the thin-walled mould: step 1B are illustrated here.

[0136] According to the method according to the invention, a thin-walled mould containing reinforcing fibres is placed in a matrix attached to a press. Step 1A illustrates a press 12 comprising a heating circuit 14 and a means 13 for injecting the reactive composition. The thin-walled mould 11 receives the reactive composition in the molten state. The press is maintained in a closed position during all or part of the polymerization of the polymer matrix. The press is then opened. The thin-walled mould is removed. In step 1B, the thin-walled mould is placed in a cold moulding device 15 comprising a cooling circuit 16 to allow it to cool. The thin-walled mould is then removed.

[0137] Figure 2 shows an embodiment of a thin-walled mould according to the invention. Mould 1 is made up of part 2 constituting the upper part of mould 1 and part 3 constituting the lower part of mould 1. Part 2 comprises a protruding rib 4 which runs over the whole edge of the part. Part 2 also comprises two injection points 5 and 6, through which the polymer or reactive composition is injected. Part 3 comprises a groove 7 which runs over the whole edge of part 3. A sealant 8 is placed in groove 7. The purpose of this sealant is to ensure the sealing of mould 1. Part 3 also comprises a cooling system close to sealant 8 placed in groove 7. The cooling system is used to extend the service life of the sealant. A tube indicated by an opening 9 makes it possible to ensure the circulation of cold water or compressed air.

[0138] The present invention also relates to the use of a thin-walled mold as disclosed above for the manufacture of composite materials.

[0139] The invention finally relates to a circular device arranged on an axis of rotation comprising several storage zones of identical shape, said shape being complementary to the shape of a part of a mould.

[0140] Other objects and advantages of this invention will become apparent from the following examples, which are not intended to be limiting. EXAMPLES

[0141] Example 1 (Comparative): The fibrous preform is introduced into a CRTM mold placed on a press, allowing a pressure of 50 bar to be applied to the mold.

[0142] The reactive composition used is a mixture of acid-terminated prepolymer PA 11 / 10T / 6T and amine-terminated PA 11 / 10T / 6T in a 50 / 50 ratio, with a molar mass of 2,500 g / mol and a viscosity of 1 Pa.s at 300° C. The melting point of the prepolymer is 265° C. and the crystallization temperature of the final polymer is 230° C.

[0143] The thermal cycle used in the molding goes from 220°C to 300°C, so the temperature amplitude of the cycle is 80°C. A 1 minute plateau is performed at 300°C. The prepolymer injection is performed at 300°C at the beginning of the 1 minute plateau. The desired cycle time is 2 minutes, which means that every 2 minutes the part is removed from the mold and a new preform is inserted into the mold.

[0144] In other words, the prepolymer is injected at 300°C, the temperature is held at 300°C for 1 minute, then the temperature of the press is reduced to 220°C over 30 seconds. The part is removed from the mold. The temperature of the press is then increased again to 300°C over 30 seconds for another cycle.

[0145] The part, the geometry of which is shown in FIG. 3, is designed in a press including a heating and cooling system that allows forming in 2 minutes, the cycle having a temperature amplitude of 80° C.

[0146] To carry out this cycle, 250 kW of power is required for heating and 160 kW for cooling.

[0147] Furthermore, molding tests using preforms equipped with thermocouples showed that temperature control from one point in the mold to another was very poor, with differences of over 20°C observed from one point in the mold to the other during thermal cycling. Thus, thermal steady state is never reached in the mold. Furthermore, the thermal cycling is too rapid to reach thermal equilibrium.

[0148] Additionally, samples were taken at different locations of the molded composite parts and molar mass measurements were performed by NMR (see Table 1).

[0149] Figure 3 illustrates a perspective view of a molded part 30 according to Example 1. Positions 31, 32, and 33 represent the positions where analytical samples were taken. The results show that the molar masses are different at these different positions. Thus, the temperature variations experienced from one point of the mold to another lead to differences in the progress of the in situ polymerization reaction.

[0150] Finally, it was observed that the crystallization of the resin in the composite was not complete, which resulted in an average enthalpy of crystallization of 17 kJ / mol, compared to 32 kJ / mol for this type of polymer when fully crystallized, measured by DSC. This difference in the values ​​of the crystallization enthalpy can be explained by the too fast cooling speed applied in the mold, which allows to emphasize the cycle time of 2 minutes. Furthermore, temperature variations from one point of the mold to another result in variations in the crystallization of the resin (see Table 1).

[0151] Example 2 according to the invention: The fibers are introduced into a thin-walled steel CRTM mold, 3 mm thick, placed outside the press. This mold is then closed and kept closed by a vacuum-filling system consisting of a pump and a pipe connected to several vent holes located throughout the preform. The thin-walled mold is then transferred to a matrix placed on the press and preheated to 300° C. After a holding time of 30 seconds, the temperature of the thin-walled mold reaches that of the heated matrix. The reactive composition used is the same as that disclosed in Example 1. The reactive composition is then injected in 5 seconds into the compression chamber of the thin-walled mold. Using the press, a pressure of 50 bar is applied to the mold, which in 5 seconds makes it possible to close said compression chamber and impregnate the fibrous preform.

[0152] After the compression stage, the temperature is maintained at 300°C for 1 minute, then the pressure is reduced to 5 bar and the vacuum re-established. The press opens and the thin-walled molds are removed from the heated matrix by a robotic arm and then placed on a carousel, which rotates until a second thin-walled mold containing only the glass fiber preform is placed near the press and in place of the first mold in the heated matrix to receive the reactive composition. The carousel has five locations for the molds.

[0153] The cycle time is 2 minutes, ie 30 seconds heating of the thin wall mold + 1 minute hold for polymerization of the press and impregnation of the glass fibers + 30 seconds handling time to load and unload the mold.

[0154] The first thin-walled mould is then removed from the carousel by a robotic arm and placed in a cold forming apparatus. This latter is maintained at a temperature of 220°C, which allows the thin-walled mould to cool. This forming apparatus allows a residual pressure of 5 bar to be applied throughout the cooling phase of the thin-walled mould. After a cooling time of 10 minutes, when the thin-walled mould has reached a temperature of 220°C, it is removed from the cold forming apparatus, then opened and the composite part is removed from the mould.

[0155] For the cycle disclosed in Example 1, the energy cost of this molding cycle is divided by ten.

[0156] The crystallization time of the resin during cooling is significantly increased while maintaining a similar cycle time, which results in better polymerization and better crystallization of the resin (see Table 1).

[0157] The temperatures recorded from one point on the mold to another and the thermal calculations show a variation of + / - 2°C, which is very close to the variation obtained in a purely isothermal mold.

[0158] The composite samples prepared in zones 31, 32 and 33 shown in FIG. 3 make it possible to observe a similar progression of the polymerization reaction at any point of the mold: similar molar masses as well as good homogeneity of crystallization (see Table 1). TIFF0007652754000001.tif50170[Table 1]: Molar mass measurements by NMR and crystallization by DSC in zones 1, 2 and 3 of the parts for two different molding cycles.

Claims

1. A method for manufacturing a part made of a composite material comprising reinforcing fibers and a polymer matrix, comprising the following successive steps: - placing a closed thin-walled mould (11) inside which the reinforcing fibres are arranged, into a matrix mounted on a press (12); - closing the press (12), - injecting a polymer or a reactive composition comprising at least one prepolymer, at least one monomer, or a mixture thereof, in the molten state into a closed thin-walled mould (11); - maintaining the press (12) closed during all or part of the polymerization of the polymer matrix when the reactive composition is injected; - opening the press (12), - removing the thin-walled mould (11) from the press (12) while maintaining a residual pressure in said mould (11) of between 0.7 and 10 bar, preferably between 0.7 and 5 bar; - cooling the mould (11) under said residual pressure. Including, After the cooling step, a step of releasing the composite material from the thin-walled mold (11) is included. method.

2. The method according to claim 1, characterized in that the thin-walled mould (11) is provided with a vacuum filling system facilitating a pressure of 0.7 bar to 0.9 bar.

3. 3. A method according to claim 1 or 2, characterized in that the matrix of the press (12) is maintained at a constant temperature between 250°C and 320°C.

4. 4. The method according to any one of claims 1 to 3, characterized in that the cooling step consists in cooling the mould (11) by heat conduction with the surrounding air through its thin wall, under a residual pressure of between 0.7 and 10 bar, preferably between 0.7 and 5 bar, to a temperature below the crystallization temperature (Tc) of the polymer being formed.

5. 4. The method according to any one of claims 1 to 3, characterized in that the cooling step consists in placing the thin-walled mould (11) in a so-called cold moulding device (15) adjusted at a temperature below the crystallisation temperature of the polymer to be formed, under a residual pressure between 0.7 and 10 bar, preferably between 0.7 and 5 bar.

6. 6. The method according to any one of claims 1 to 5, characterized in that, when the injection step is carried out with a reactive composition, the polymerization of the reactive composition is carried out in the presence of degassing, preferably the degassing is carried out by applying a vacuum ranging from 0.010 to 0.950 bar, preferably from 0.700 to 0.900 bar, relative to atmospheric pressure.

7. 7. The method according to any one of claims 1 to 6, characterized in that the step for keeping the press (12) closed during all or part of the polymerization is carried out by compression of the mold (11), preferably at a pressure ranging from 10 to 70 bar, and even more preferentially from 40 to 60 bar.

8. 8. The method according to any one of claims 1 to 7, characterized in that the polymer matrix is ​​selected from polyamide, polyester, polyamide-imide, polyamide-ether, polyacrylic, polyolefin, phenylene polysulfide, polyether-imide matrices, preferably polyamide matrices.

9. 9. The method according to any one of claims 1 to 8, characterized in that the reinforcing fibres are chosen from inorganic fibres, preferably glass, carbon or basalt fibres, in particular glass or carbon fibres, or from synthetic fibres, preferably aramid fibres or polyaryletherketone fibres, or from mixtures thereof; and / or the reinforcing fibres have an L / D ratio of more than 1,000, preferably more than 2,000, L being the average length of the fibres and D being their average diameter.

10. A mould comprising two parts intended to be assembled, the mould comprising: a first member including a groove over the edge of the member; a second member including a protruding rib over the edge of the member; and It consists of the locations of the grooves and ribs are selected to mate with one another when the mold is in a closed position; a seal is disposed in the groove of the first member; the part is of a thickness that allows it to withstand a residual molding pressure that is greater than the saturated vapor pressure of water at the injection temperature of the reactive composition; - The material has thermal conductivity It is characterized by: It comprises a mechanical closing system which makes it possible to apply a residual pressure between 0.7 and 10 bar, Mold.

11. 11. Mould according to claim 10, characterised in that the residual moulding pressure is less than or equal to 5 bar, preferably between 0.7 and 5 bar.

12. Mould according to claim 10 or 11, characterized in that it is equipped with a vacuum filling system making it possible to maintain the mould in a closed position.

13. A mold as described in claim 10 or 11, characterized in that it includes a mechanical closing system making it possible to apply a residual pressure of between 0.7 bar and 5 bar.

14. Mold according to any one of claims 10 to 13, characterized in that it comprises cooling channels making it possible to cool a seal arranged in a groove in the first part.

15. Use of a mould according to any one of claims 10 to 14 for the production of a composite material.

Images