Heater for thermoplastic resin

Abstract

Heater for thermoplastic resin. The invention relates to a heater (10) comprising at least one outer element (32) and one inner element (31), at least one of the inner and outer elements being a heating element, an inlet (21) and an outlet (22), the axis between the inlet and the outlet defining the main axis (XX) of the heater, the heater further comprising a chamber (34) extending between the inlet and the outlet, the heater being characterized in that the chamber has an annular shape around the main axis of the heater, the chamber being defined between a wall of the inner element and a wall of the outer element, the heater being further characterized in that the cross-section of the chamber increases between the inlet and an intermediate point and then decreases between the intermediate point and the outlet. Figure for abstract: Fig. 1

Description

Title of the invention: Heater for thermoplastic resin Technical field

[0001] The invention relates to the field of the preparation of composite materials and in particular the step of preparing a resin intended to form the matrix of such a composite material. Prior art

[0002] Composite material parts consist of a fiber preform, reinforced by a matrix. The final properties of a composite material depend on the one hand on the fiber preform, in particular the nature of the fibers and the properties of the weave, and on the other hand on the nature of the matrix in this fiber preform.

[0003] There are many ways of impregnating a fiber preform with a matrix to obtain a final part, the impregnation method generally being a function of the chemical nature of the matrix chosen and the specifications for the final part.

[0004] In the particular case of composite materials with organic matrices, the matrix can be formed by a thermosetting resin comprising a polymer, a hardener and optionally a catalyst.

[0005] The process of impregnating the preform is then preceded by a step of heating the mixture intended to form the matrix, this mixture comprising the thermosetting resin and the hardener. This heating step then makes it possible to activate the hardener and to promote its dissolution in the resin.

[0006] In order to speed up industrial processes for manufacturing composite material parts, it is desirable to increase the flow rate of the heaters to allow faster impregnation of the parts. However, the temperature that the mixture of resin and hardener must have remains unchanged. In the current geometry of heaters, particularly plate heaters, increasing the flow rate implies a shorter residence time, and it is not possible to reach the same temperature at the heater outlet without having to enlarge the heater. Unfortunately, enlarging the heater implies that it includes a larger quantity of resin in residence, which is not desirable. Indeed, at the end of the preform impregnation process, when the flow of resin coming from the heater must be stopped, the resin remaining in the heater is not reusable and must be eliminated, because it has already been mixed with the hardener.

[0007] Increasing the size of the heaters is therefore not desirable on the scale of the industrial process, and there remains a need for a heater that can increase the flow rate of heated resin, without reproducing the disadvantages described above. Statement of the invention

[0008] The invention aims precisely to respond to the above problem.

[0009] For this, according to a first aspect, the invention relates to a heater comprising an external element and an internal element, at least one of the internal and external elements being a heating element, an inlet and an outlet, the axis between the inlet and the outlet defining the main axis of the heater, the heater further comprising a chamber extending between the inlet and the outlet, the heater being characterized in that the chamber has an annular shape around the main axis of the heater, the chamber being defined between a wall of the internal element and a wall of the external element, the heater being further characterized in that the section of the chamber increases between the inlet and an intermediate point then decreases between the intermediate point and the outlet.

[0010] Such a heater, and more precisely the particular geometry of its chamber, offers many advantages.

[0011] First, the fact that the chamber extends between an internal element and an external element, at least one of the two being heated, makes it possible to have a maximized contact surface between the fluid inside the heater chamber and the at least one heating element, which promotes heat exchanges and reduces the residence time of a fluid necessary to reach the target temperature. In one embodiment, both the internal and external elements are heated, which further increases the contact surface allowing the heating of a fluid inside the chamber, as well as the homogeneity of said heating.

[0012] In one embodiment, the inner element and the outer element are heating elements.

[0013] In the remainder of this application, an internal heating element and an external heating element will be described, but it should be understood that it is necessary that only one of the two elements be heated and that it is only preferable that both be heated.

[0014] The geometry of the heater is also suitable for a high flow rate.

[0015] Indeed, generally speaking, at constant flow rate, when the section of the chamber increases, the speed of the fluid decreases. Thus, the speed of the fluid in the heater decreases in the vicinity of the intermediate point, where the surface area of ​​the chamber in contact with the heating elements is at its maximum. This makes it possible to maximize the heat transfer on the one hand, and to reduce the residence time necessary to achieve the target temperature on the other hand. In particular, the residence time can be adjusted to the desired flow rate.

[0016] Since the required residence time is a function of the heater cross-section, and the cross-section variation of the present heater is precisely optimized to allow optimal heating in a shorter residence time than in prior art heaters, the heater of the invention can operate with a higher flow rate than prior art heaters while maintaining an acceptable internal volume.

[0017] The heater described therefore makes it possible to increase the flow rate compared to the heaters of the prior art, without increasing the total volume of the chamber, and therefore without requiring a larger volume of fluid in residence. This contributes to minimizing resin losses in a process for manufacturing a part made of composite material.

[0018] Finally, the geometry of the heater chamber allows for automated cleaning thereof, which is not possible with the plate heaters usually used.

[0019] In the application, it is understood that the terms quantifying a variation must be assessed in the flow direction of the mixture, i.e. from the inlet to the outlet.

[0020] For the purposes of the invention, the intermediate point is intended only to characterize a particular point of the heater defined by a geometric criterion, i.e. a point where the section of the chamber is maximum. This designation should not be understood as restricting the positioning of the intermediate point in the heater.

[0021] In particular, it is not at all necessary for the intermediate point to be halfway between the input and the output.

[0022] In one embodiment, the distance between the inlet and the intermediate point may be between 25% and 75% of the total distance between the inlet and the outlet.

[0023] This embodiment avoids abrupt changes in chamber geometry and thus ensures laminar flow of the mixture in the heater.

[0024] For the purposes of the invention, the “section of the chamber” must be understood as being represented by the projection of the chamber in a section plane perpendicular to the main axis of the heater.

[0025] For the purposes of the invention, the "annular shape" of the chamber describes that the chamber extends in the shape of a ring between a wall of the internal heating element and a wall of the external heating element.

[0026] If we speak of a specific point of the heater, the "annular shape" of the heater is understood to mean that the chamber has a ring shape in a section plane of the heater perpendicular to the main axis of the heater.

[0027] Furthermore, the "annular shape around the main axis of the heater" means that the main axis of the heater is at the center of the annular shape described by the chamber.

[0028] For the purposes of the invention, the “surface area of ​​the chamber” is understood as the sum of the surface area of ​​the internal heating element and the external heating element together defining the internal and external walls of the chamber respectively.

[0029] If we are talking about a specific point in the heater, the "chamber surface" becomes the perimeter of the projection of the chamber in a section plane perpendicular to the main axis of the heater.

[0030] In one embodiment, the surface area of ​​the chamber increases between the inlet and the intermediate point where it is maximum, then decreases between the intermediate point and the outlet of the heater.

[0031] In one embodiment, the internal heating element is movable within the heater between an inlet-closing position and an outlet-closing position.

[0032] The movement of the internal heating element therefore makes it possible to stop the power supply to the heater.

[0033] For example, the heating element may be movable in translation along the main axis of the heater. The inlet closure position may correspond to a position in which the surface of the internal heating element comes into contact with the surface of the external heating element near the inlet, so that the path between the inlet and the outlet is cut as close as possible to the inlet of the heater.

[0034] Similarly, the outlet closure position may correspond to a position in which the surface of the internal heating element contacts the surface of the external heating element near the outlet, so that the path between the inlet and the outlet is cut off as close as possible to the outlet.

[0035] In one embodiment, the internal and external heating elements can be decomposed into a plurality of independent complementary elements, each capable of receiving a different set temperature.

[0036] As already described, it is also possible that only the internal or external element is heated, and therefore broken down into a plurality of independent complementary elements. To simplify the description and understanding, the case where the two elements are heated simultaneously is described below.

[0037] In one embodiment, the internal heating element may include an independent upstream element and a downstream element each capable of being heated to different temperatures from one another.

[0038] This embodiment makes it possible to adjust the temperature more finely, and to optimize the heating of the resin and hardener mixture in the heater.

[0039] Also, it makes the construction of the heater simpler which can then be composed of several connected elements rather than formed as a single unit.

[0040] In one embodiment, the external heating element may include an independent upstream element and a downstream element each capable of being heated to different temperatures from one another.

[0041] This embodiment allows the temperature in the heater to be adjusted more finely. It also makes the construction of the heater simpler, which can then be composed of several connected elements rather than formed from a single piece.

[0042] In one embodiment, the internal heating element and / or the external heating element comprises an independent upstream element and a downstream element each capable of being heated to different temperatures from one another.

[0043] In one embodiment, the cross-section of the heater outlet may be smaller than the cross-section of the heater inlet.

[0044] In one embodiment, the chamber has a symmetry around the main axis of the heater, for example a central symmetry or a symmetry of revolution.

[0045] For example, the chamber may have an elliptical shape about the main axis, or a circular shape.

[0046] In one embodiment, at any point, the projection of the chamber into a plane perpendicular to the main axis of the heater is a topologically connected space.

[0047] A “topologically connected space” must be understood with its mathematical definition.

[0048] A topologically connected space is a space in which all points can be connected by a path belonging itself to the space. In other words, it is possible to connect all points of the space without leaving the space. It should be understood that in this embodiment, the chamber is not separated between several disjoint channels.

[0049] This embodiment further facilitates the cleaning of the heater. It is no longer necessary to ensure before the cleaning operation that all paths are accessible to the cleaning product. In addition, even if an element, for example a resin clot, is blocked in the chamber due to the reduction in section, the latter will be reached by the cleaning product passing around in the chamber, which will allow it to be cleaned.

[0050] According to another of its aspects, the invention also relates to a method for reheating a mixture comprising a resin and a hardener comprising at least the following steps:

[0051] - introducing the mixture into the chamber of a heater according to one of the modes of implementation described, and

[0052] - heating the mixture, achieved by heating the heating elements internal and / or external of said heater.

[0053] This method advantageously makes it possible to have at the outlet of the heater a mixture of resin and hardener capable of impregnating a fibrous preform to form the matrix of an organic matrix composite material, while minimizing the quantity of mixture present in the heater to reduce losses at the end of the process.

[0054] Furthermore, the flow rate permitted by the heater is much higher than that available via prior art plate heaters.

[0055] In one embodiment, the temperature of the mixture at the heater outlet is greater than or equal to 150°C.

[0056] This temperature is in fact easily accessible thanks to a heater of the invention, and allows suitable activation and dissolution of the hardener in the mixture.

[0057] In one embodiment, the resin may be an epoxy resin, for example available under the trademark PR520, which already includes a heat-activated hardener.

[0058] In one embodiment, the flow rate of the mixture at the heater outlet is between 1000 cc.min 1 and 2000 cc.min *.

[0059] This mixing flow rate, higher than that offered by the plate heaters of the prior art, is enabled by the heater described above and makes it possible to reduce the time required for impregnating the fiber preforms.

[0060] The mixture of resin and hardener leaving the heater can be used in many impregnation processes, including liquid composite molding, also known as "LCM" for the English acronym "Liquid Composite Molding", resin transfer molding, also known as "RTM" for the English acronym "Resin Transfer Molding", high-pressure resin transfer molding, also known as "HP-RTM" for the English acronym "High-Pressure Resin Transfer Molding", compression resin transfer molding, also known as "C-RTM" for the English acronym "Compression Resin Transfer Molding". Brief description of the drawings

[0061] [Fig.l] [Fig.l] schematically represents a heater according to the invention, seen in section, and in an operating position.

[0062] [Fig.2a] [Fig.2a] schematically represents a section of a heater according to the invention in a plane perpendicular to the main axis of the heater.

[0063] [Fig.2b] [Fig.2b] schematically represents a section of a heater according to the invention in a plane perpendicular to the main axis of the heater.

[0064] [Fig.2c] [Fig.2c] schematically represents a section of a heater according to the invention in a plane perpendicular to the main axis of the heater.

[0065] [Fig.2d] [Fig.2d] schematically represents a section of a heater according to the invention in a plane perpendicular to the main axis of the heater.

[0066] [Fig.3] [Fig.3] schematically represents a heater according to the invention, seen in section, and in a position of closing the entrance.

[0067] [Fig.4] [Fig.4] schematically represents a heater according to the invention, seen in section, and in a position of closing the outlet.

[0068] [Fig.5] [Fig.5] schematically represents the variation of different variables of the process in the heater. Description of the embodiments

[0069] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0070] [Fig.l] represents a heater 10 according to one embodiment of the invention.

[0071] In the embodiment shown, the chamber 34 of the heater 10 extends between an entrance 21 and an exit 22.

[0072] The arrows in [Fig.l] mark the path of a fluid introduced into the heater 10 between the inlet 21 and the outlet 22.

[0073] The chamber 34 is defined between an internal heating element 31 and an external heating element 32.

[0074] The internal heating element 31 is held in place, for example by arms connected to the external heating element 32, which arms are not shown in [Fig.l].

[0075] In the embodiment which is described, the chamber 34 has an annular or revolution geometry around the main axis of the heater XX. The axis XX being defined as that joining the inlet 21 and the outlet 22.

[0076] [Fig.l] also marks Do, the section of the inlet 21, Di the section at the intermediate point, and Ds, the section of the outlet 22.

[0077] It must be clearly understood that [Fig.l] represents a chamber 34 of annular or revolution geometry.

[0078] In other words, the surface Sint of the internal heating element 31 defines, in a plane perpendicular to the main axis XX of the heater 10, a curve called the internal curve, around the projection of the main axis XX in said plane.

[0079] Preferably, the internal curve does not have an angular point, a point of the curve being said to be angular when the tangent to the right and the tangent to the left are not parallel.

[0080] In one embodiment, the internal curve may be a curve devoid of angular points, having as its center of symmetry the projection of the main axis XX in the plane considered.

[0081] For example, the internal curve may be an ellipse or a circle, as in the embodiment shown.

[0082] These two embodiments allow simplified manufacturing of the internal heating element 31.

[0083] Similarly, the wall Sext of the external heating element 32 defines, in a plane perpendicular to the main axis XX of the heater 10, a curve called the external curve, around the projection of the main axis XX in said plane.

[0084] In one embodiment, for the same reasons as the internal curve Sint, the external curve Sext does not have an angular point.

[0085] In one embodiment, the outer curve is an ellipse or a circle, as in the illustrated embodiment.

[0086] Figures 2a, 2b, 2c, 2d represent sections, made at different points of the heater 10, namely at the inlet 21 ([Fig.2a], section oo), at any point between the inlet and the intermediate point ([Fig.2b], section bb), at the intermediate point ([Fig.2c], section ii), and at the outlet 22 ([Fig.2d], section ss).

[0087] In the embodiment shown, the internal curve Sint and the external curve Sext are circles, but this is not necessary for the invention.

[0088] It can be seen in Figures 2a, 2b, 2c that the section of the chamber 34, that is to say the hatched surface between the internal curve Sint and the external curve Sext increases between the entrance and the intermediate point, as illustrated between Figures 2a, 2b and 2c.

[0089] The section of the chamber 34 then decreases between the intermediate point and the exit of the chamber, as illustrated between figures 2c and 2d.

[0090] As described, the chamber 34 extends between the internal heating element 31 and the external heating element 32.

[0091] In the embodiment shown, both the internal curve Sint and the external curve Sext vary to achieve the variation in the section of the chamber 34.

[0092] In one embodiment, which is the one shown, the variation in the section of the chamber 34 is produced by a reduction in the distance between the internal heating element 31 and the external heating element 32 and an increase in the thickness, here the diameter, of the internal heating element 31.

[0093] However, it does not go beyond the scope of the invention when only one of the two internal and external curves varies, provided that the variation in the section of the chamber 34 is in accordance with what has been described.

[0094] Furthermore, it can be seen in Figures 2a to 2d that the increase in the section Di of the chamber 34 at the intermediate point is accompanied by an increase in the contact surface between the chamber 34 and the internal 31 and external 32 heating elements.

[0095] This increase in the contact surface ensures excellent transfer thermal between the mixture of resin and hardener introduced into the chamber 34 and the internal 31 and external 32 heating elements.

[0096] In one embodiment, the section of the chamber at the inlet Do, also called the inlet section, can be between 1 mm and 50 mm, or even between 8 and 40 mm.

[0097] In one embodiment, the section of the chamber at the outlet Ds, also called the outlet section, can be between 1 mm and 10 mm, or even between 8 and 40 mm.

[0098] The values ​​proposed for the sections of the chamber at the inlet and outlet make it possible in particular to avoid pressure losses or excessive shearing of the material.

[0099] As shown in [Fig.l], in one embodiment, the internal heating element 31 can be made in two separate parts, an upstream part 31a and a downstream part 31b.

[0100] However, the invention is not limited to an embodiment where the internal heating element 31 is decomposed into two elements. This is also true for the decomposition of the external heating element 32 which will be detailed later.

[0101] In this embodiment, the two upstream 31a and downstream 31b parts of the internal heating element 31 may be independent. In particular, the set temperature of each of the two parts 31a, 31b may be different.

[0102] Such an embodiment allows better control of the heating of the resin.

[0103] For example, in one embodiment, it is possible to envisage heating a mixture of resin and hardener to the target temperature between the inlet 21 and the intermediate point using the upstream part 31a, then maintaining the mixture at the target temperature between the intermediate point and the outlet 22.

[0104] This embodiment makes it possible to obtain at the outlet 22 of the heater 10 a resin at the target temperature which also has excellent thermal homogeneity.

[0105] Alternatively, in one embodiment the resin may be heated gradually between the inlet 21 and the outlet 22, by applying a first temperature to the upstream internal heating element 31a, and a second temperature higher than the first temperature to the downstream heating element 31b.

[0106] As shown in [Fig.l], in one embodiment, the external heating element 32 may comprise a separate upstream element 32a and downstream element 32b, which may receive different setpoint temperatures.

[0107] The upstream 32a and downstream 32b external heating elements make it possible to obtain technical advantages similar to those presented above for the upstream 31a and downstream 31b internal heating elements.

[0108] Furthermore, the manufacture of the heating elements is simplified by the decomposition into an upstream element 31a, 32a and a downstream element 31b, 32b.

[0109] In the embodiment shown in [Fig.l] and in which each element heating element 31, 32 is broken down into an upstream element 31a, 32a and a downstream element 31b, 32b; it is possible to have for each elementary element a shape that is more easily shaped than the overall shape of the internal heating element 31 or external heating element 32.

[0110] For example, in the illustrated embodiment, the upstream external heating element 32a has an elliptical or cylindrical shape around the main axis XX of the heater 10 which widens between the inlet 21 and the intermediate point, and the same for the upstream internal heating element 31a.

[0111] Conversely, the downstream external heating element 32b has an elliptical or cylindrical shape around the main axis XX of the heater 10 which narrows between the intermediate point and the outlet 22, and the same for the downstream internal heating element 31b.

[0112] Each of the elementary elements thus presents a monotonous variation in its thickness and is thus easier to produce than an internal 31 or external 32 heating element which would have the same shape made from a single piece.

[0113] In one embodiment, the internal 31 and external 32 heating elements may be made of stainless steel, copper or aluminum, or an alloy of such elements.

[0114] In one embodiment, the internal 31 and external 32 heating elements are resistive heating elements, in which the heat is provided by applying an electric current not shown.

[0115] In an alternative embodiment, the internal 31 and external 32 heating elements are inductive heating elements. In this embodiment, the heating elements shown 31, 32 are then in reality the susceptors which must be coupled to inductors to allow their temperature rise.

[0116] As indicated above, the internal heating element 31 may be movable.

[0117] In one embodiment, the internal heating element 31 is movable in translation along the main axis XX of the heater 10.

[0118] [Fig. 3] shows the same heater 10 as shown in connection with [Fig. 1], in which the internal heating element 31 is moved to a position for closing the inlet 21.

[0119] Indeed, in [Fig. 3], the wall of the internal heating element 31 is brought into contact with the wall of the external heating element 32 so that the chamber no longer connects the inlet 21 to the outlet 22, the contact between the internal heating element 31 and the wall of the external heating element 32 being closer to the inlet 21 than to the outlet 22.

[0120] This embodiment makes it possible to stop the supply of the heater 10, for example at the end of the process, and this without requiring any obstructing element other than elements already present in the heater 10.

[0121] Similarly, [Fig.4] shows a heater 10 in which the internal heating element 31 is in a position for closing the outlet.

[0122] Indeed, in [Fig.4], the wall of the internal heating element 31 is brought into contact with the wall of the external heating element 32 so that the chamber no longer connects the inlet 21 to the outlet 22, the contact between the internal heating element 31 and the wall of the external heating element 32 being closer to the outlet 22 than to the inlet 21.

[0123] Furthermore, having a movable internal heating element 31 makes it possible to precisely adjust the position of the intermediate point and in particular to choose whether the latter is opposite the upstream heating elements 31a, 32a or downstream 31b, 32b.

[0124] In particular, this allows a more precise choice of temperature and flow conditions, particularly at the intermediate point, which make it possible to refine the process to the particular choice of a resin and a hardener.

[0125] [Fig. 5] represents very schematically the evolution of several characteristic values ​​in a heater 10 as it has just been described in connection with figures 1 to 4.

[0126] The horizontal axis 100 represents the movement in the heater 10 between the inlet 21, represented at point 101, the intermediate point, represented at point 102 and the outlet 22, represented at point 103.

[0127] In [Fig.5], and as may have been described previously, the intermediate point is slightly closer to the exit 22 than to the entrance 21, without this having to be interpreted restrictively.

[0128] The vertical axis 200 of the ordinates is used here without unit to visualize the evolution of the quantity studied.

[0129] Curve 300 represents the evolution in the heater 10 of the speed of the mixture of resin and a hardener in the chamber.

[0130] The speed at the inlet of the heater 301 is greater than at the intermediate point 302 where it passes through a minimum. At this point, the speed is minimal which allows excellent heat transfer between the heating elements 31, 32 and the mixture. The speed of the mixture 300 then increases between the intermediate point 302 and the outlet 303 of the heater.

[0131] In the embodiment shown, since the section of the chamber 34 at the outlet Ds is slightly smaller than the section of the chamber 34 at the inlet Do, as can be seen in Figures 1 to 4, the speed of the mixture is greater at the outlet 303 than at the inlet 301.

[0132] This embodiment should not be considered restrictive, and in another embodiment, the speed at the output 303 may be less than or equal to the speed at the input 301.

[0133] Curve 400 represents the evolution of the temperature of a mixture of resin and a hardener introduced into the heater, in one embodiment.

[0134] As illustrated, the temperature of the mixture 400 increases between the temperature initial 401 up to a target value 402 reached at the intermediate point.

[0135] The temperature then increases more slightly between the intermediate point and the outlet temperature 403, which ensures that the mixture is at a temperature suitable for impregnating a fiber preform.

[0136] The embodiment illustrated for the evolution of the temperature 400 is made possible by the decomposition of the internal 31 and external 32 heating elements into upstream 31a, 32a and downstream 31b, 32b elements.

[0137] Curve 500 illustrates the evolution of the section of the chamber 34 of the heater 10.

[0138] The section of the chamber at the inlet of the heater 501 is smaller than at the intermediate point 502 where it passes through a maximum. The section of the chamber 500 then increases between the intermediate point 502 and the section at the outlet of the chamber 503, as already described, in particular in connection with FIGS. 2a, 2b, 2c, 2d.

[0139] Curve 600 illustrates the evolution of the surface area of ​​the chamber 34. The surface area of ​​the chamber follows variations similar to the section of the chamber 500.

[0140] The surface area of ​​the chamber increases between the inlet 601 and the intermediate point 602, then decreases between the intermediate point 602 and the outlet 603.

Claims

Claims

1. A heater (10) comprising at least one external element (32) and one internal element (31), at least one of the internal and external elements being a heating element, an inlet (21) and an outlet (22), the axis between the inlet and the outlet defining the main axis (XX) of the heater, the heater further comprising a chamber (34) extending between the inlet and the outlet, the heater being characterized in that the chamber has an annular shape around the main axis of the heater, the chamber being defined between a wall of the internal element and a wall of the external element, the heater being further characterized in that the cross-section of the chamber increases between the inlet and an intermediate point and then decreases between the intermediate point and the outlet.

2. A heater (10) according to claim 1, wherein the inner member (31) and the outer member (32) are heating elements.

3. A heater (10) according to claim 1 or 2, wherein the internal heating element (31) is movable within the heater between an inlet-closing position and an outlet-closing position.

4. A heater (10) according to any one of claims 1 to 3, wherein the internal heating element (31) and / or the external heating element (32) comprises an independent upstream element (31a, 32a) and a downstream element (31b, 32b) each capable of being heated to temperatures different from each other.

5. Heater (10) according to any one of claims 1 to 4, wherein the section (Ds) of the outlet (22) of the heater is smaller than the section (Do) of the inlet (21) of the heater.

6. A heater (10) according to any one of claims 1 to 5, wherein the chamber (34) has symmetry about the main axis of the heater (XX).

7. A heater (10) according to any one of claims 1 to 6, wherein, at any point, the projection of the chamber (34) in a plane perpendicular to the main axis (XX) of the heater is a topologically connected space.

8. A method of heating a mixture comprising a resin and a hardener comprising at least the following steps: - introducing the mixture into the chamber (34) of a heater (10) according to any one of claims 1 to 7, and - heating the mixture, carried out by heating the internal (31) and / or external (32) heating elements of said heater.

9. A method of heating a mixture comprising a resin and a hardener according to claim 8 wherein the temperature of the mixture at the outlet of the heater (10) is greater than or equal to 150°C.

10. Method for heating a mixture comprising a resin and a hardener according to one of claims 8 or 9, in which the flow rate of the mixture at the outlet of the heater (10) is between 1000 cc.min 1 and 2000 cc.min *.

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