CN210553147U

CN210553147U - Composite product

Info

Publication number: CN210553147U
Application number: CN201821809984.8U
Authority: CN
Inventors: C.费舍; J.里昂; S.德瑞克
Original assignee: Bihuang Co Ltd
Current assignee: Biconpu Co ltd
Priority date: 2017-11-06
Filing date: 2018-11-05
Publication date: 2020-05-19
Anticipated expiration: 2028-11-05
Also published as: FR3073167B1; WO2019087141A1; FR3073167A1

Abstract

The present invention relates to a sheet-like or tape-like composite product, the product comprising a grid (1) and a polymer, -said grid being formed by interwoven wires (3) defining mesh openings, the wires (3) being based on fibers, -said grid (1) comprising an upper face (6) and a lower face (7) opposite to the upper face (6), -each wire having an upper portion located on the upper face of the grid, a lower portion located on the lower face of the grid, and an intermediate portion between the upper portion and the lower portion, -the wires of the grid being impregnated with said polymer, said impregnation being asymmetric, such that the upper portion of the wires comprises a greater amount of impregnated polymer relative to the lower portion and the intermediate portion.

Description

Composite product

Technical Field

The utility model relates to a composite product and be used for producing device of this kind of product.

Background

Composite products are typically used as reinforcing structures or frames to improve the mechanical properties of the parts.

Composite products often include a wire assembly and a matrix composed of a polymer. The wire assembly may take different forms.

Document WO2015121583 describes the manufacture of a composite material in the form of a twisted rope (meche) assembly impregnated and braided into strips. The strip typically has a width of about 100 mm. In this method, the twisted rope is immersed in a fluidized bed. The twines are then aligned in the direction in which they are compressed in a heated calender which allows the desired dimensions to be imparted to each twine.

Document WO2010034771 describes a polyamide composite article consisting of a fabric or assembly of wires, the wires being bonded to each other by a polyamide resin. The impregnation of the wire by the polyamide is carried out under pressure by means of a hydraulic press. This type of impregnation requires the installation of complex equipment, such as presses with moulds adapted to the shape and size of the fabric.

The applicant wishes to make a composite product comprising an assembly of wires impregnated with a polymer and in the form of a mesh (in other words a grid). Such impregnated grids may be used as such or, more commonly, as semi-finished products to coat resins or polymers for use as reinforcements in panels or other flexible or rigid composite elements.

In wire assemblies in the form of a mesh, the polymer particles may pass through the mesh via the mesh openings of the mesh as they are sprinkled (sprinkle) on the mesh. For this purpose, the grid is usually placed on a conveyor belt of a conveyor which displaces the grid from spraying towards heating. However, this solution is not satisfactory: in spraying, the polymer particles are deposited on the wire, but also in the mesh openings of the grid. In this case, upon heating, the impregnation of the wire is not satisfactory, since the polymer melts and tends to accumulate between the grid and the strip. Furthermore, after heating, the mesh openings become blocked with polymer, and it often happens that the mesh still sticks to the conveyor belt. Tearing off the mesh results in degradation of the mesh impregnation.

The prior art therefore does not allow to obtain composite products based on wire meshes in which the impregnation is satisfactory. The resulting composite product does not have satisfactory mechanical properties due to poor impregnation of the wire.

SUMMERY OF THE UTILITY MODEL

It is an object of the invention to provide a product which does not have or minimizes the limitations of the known products.

It is another object of the present invention to provide a composite product including a wire assembly in the form of a grid.

It is another object of the invention to provide a composite product in the form of a grid and having improved mechanical properties, such as bending strength and impact or impact resistance.

Another object of the invention is to provide a composite product comprising a wire grating based on plant fibers, in particular flax.

These objects are achieved, according to the invention, in particular by a sheet-like or tape-like composite product comprising a grid and a polymer,

-the grid is formed by interwoven wires defining mesh openings, the wires being based on fibres,

-the grid comprises an upper face and a lower face opposite to the upper face,

each wire having an upper portion located on the upper side of the grid, a lower portion located on the lower side of the grid, and an intermediate portion between the upper and lower portions,

-the wires of the grid are impregnated with the polymer, the impregnation being asymmetric such that the upper portions of the wires comprise a greater amount of impregnated polymer relative to the lower and middle portions.

This solution has in particular the advantage of an asymmetrical impregnation of the wires of the grid with respect to the prior art. For this purpose, the particles are sprinkled on the upper face of the grid, and said face is then placed facing, i.e. facing, the heating element. During heating, the heating portion remains flat facing the heating element to allow for uniform heating of the heating portion. Maintaining the planar portion allows preventing the molten polymer from shifting on one side or the other of the heated portion. Moreover, this also promotes uniform heating over the planar portion of the grid. Heating from above on the portion that remains flat and not in contact allows to obtain an asymmetric impregnation.

The heating portions also remain out of contact on the upper and lower faces while heating. In other words, the heated portion is suspended without any contact, and thus no pressure is applied to the heated portion when the polymer is impregnated into the wire. For example, no element of the heating device contacts above or below the heating portion. For example, the heated grid section is not on the conveyor belt of the conveyor. Thus, the molten polymer may be distributed around the wires of the heated portion in the complete absence of stress.

For example, if heating is ensured by an infrared oven comprising a chamber equipped with infrared lamps as heating elements: there is no contact between the upper face and the infrared lamp. There is also no contact between the lower face and the lower edge of the chamber. This allows not to disturb the distribution of the molten polymer on the strands of the heated portion.

A portion of the molten polymer impregnates the top. Another portion of the molten polymer flows by gravity around the periphery of the wire and gradually impregnates the wire as and due to the flow. Thus, a gradient or asymmetric impregnation is observed from the top down: the heated portion of the grid has a greater impregnation on the upper face than on the lower face. In other words, the cross section of the wires of the heating portion has an asymmetric impregnation: there is less molten polymer available on the lower portion of the wire than on the opposite portion, and therefore less impregnation. For example, the impregnation depth is typically 40-80% of the wire radius in the upper portion, 20-60% of the radius in the middle portion, and 10-40% in the lower portion. Or in other words, asymmetric impregnation is characterized in that 40-90% (preferably 60-90%) of the impregnating polymer is located in the upper part, 10-50% (preferably 10-30%) of the impregnating polymer is located in the middle part and 0-20% (preferably 0-10%) of the impregnating polymer is located in the lower part.

Since the composite material enhances the bending stiffness when it is used as a reinforcing grid on a base material (e.g. a mat), it is beneficial to be able to manufacture composite products with higher amounts of polymer on top. Furthermore, this allows the impact resistance to be enhanced when an impact or load occurs with an external element: the wires do not break cleanly but are loosened slowly, thereby maintaining the effect of the mesh stabilizer.

Advantageously, the product according to the invention has improved mechanical properties while remaining lightweight, because the impregnation is asymmetric, which limits the quality of the polymer. Symmetric impregnation will significantly increase the weight of the composite product without significantly increasing the mechanical properties, in particular the stiffness.

Surprisingly, therefore, the product according to the invention is generally lighter than existing composite products with comparable strength, but this allows to improve the mechanical properties, in particular the rigidity or the load or impact resistance.

According to the utility model discloses a composite product is platelike or banding shape: they can be easily associated with another component by gluing or gluing to reinforce the component. For example, in motor vehicles, the composite product sheet or belt according to the present invention may be used as a reinforcement on a door trim or instrument panel or other interior trim component of a vehicle. A sheet or tape is laminated to a base material, such as a nonwoven felt made of plant fibers and polypropylene, and the assembly is heated above the melting point of the polymer and press-formed (compression-molded) in a mold. The asymmetrically deposited impregnating polymer by the above method penetrates the wire deeper in this compression moulding step, ensuring a better impregnation quality on the wire periphery, but the impregnation remains asymmetric.

Advantageously, according to the invention, the heating of the grid section covered with polymer particles is mainly performed from above, i.e. from above. Thus, the molten polymer protects the fibers from the heating element to prevent the fibers from being degraded, e.g., burned, by the heating element. Advantageously, the polymer absorbs a portion of the heat, so that the fibers of the wire are heated less than the polymer, which allows the wire to be protected.

The cooling allows the impregnated wire or the molten polymer on the surface of the wire to change from a molten state to a solid state. Advantageously, upon cooling, in a manner similar to heating, the portion containing the molten polymer remains flat and free of contact. In other words, the cooling does not exert any pressure or stress or contact on the impregnated wire and covers the molten polymer and the grid remains flat. In this case, the distribution of the molten polymer is influenced only by gravity, without any external stress disturbing the distribution of the polymer. For example, when the grid rests on the support or when the grid is tilted and the molten polymer solidifies, the asymmetric impregnation of the grid can be altered by the tilting of the grid or the support located below the grid. Furthermore, if the grid is located on the support during cooling, the grid may remain glued to the support. Finally, any contact with the support can modify the circular geometry of the impregnated wire (which contributes to the reinforcing effect on the grid). Thus, keeping the grid flat and without contact during cooling allows to avoid these drawbacks and to maintain the asymmetric distribution of the polymer on the grid and not to change the circular geometry of the wires during cooling.

The mat may be laminated on the underside or alternatively on the upper side of a portion of the heating grid. Preferably, the mat may be laminated on the underside of the heating section. The applicant has observed that the mechanical properties are better when the mat is glued to the lower portion of the impregnated wire, opposite to the upper portion containing more polymer. It is also possible to make a stack "sandwich" with the heating section between two mats. Laminating the grid on the mattress allows to significantly increase the stiffness of the mattress and brings about a weight reduction.

Preferably, the laminating step is performed between the heating step and the cooling step. In this case, at least a portion of the polymer remains molten, which promotes adhesion between the mat and the grid. The mat is brought into contact with the molten polymer. Advantageously, the contact is achieved with very little or no pressure on the grid to minimize the effect of the lamination on the thickness (cross section) of the grid, their effect being directly related to the final thickness of the grid, since the wires of the grid act as reinforcing ribs.

For example, the mat is laminated on the underside of the grid. For example, the device for laminating includes an unwinding roller, a contact roller, and a pressure roller. The unwind roller unwinds the mat toward the touch roller, which causes the mat to face the underside of the grid. The pressure and contact rollers are located on either side of the grid, facing below and above, respectively.

Preferably, the spacing between the contact roller and the underside of the grid corresponds to the thickness of the mat or is slightly higher than the thickness of the mat, so that the contact roller does not exert pressure or exerts a minimum pressure on the underside of the grid.

Preferably, the spacing between the pressure roller and the contact roller corresponds to the thickness of the grid at the heating outlet, plus in the case of a mat the thickness of the mat. This allows to minimize the maximum pressure on the grid and its deformation.

Preferably, the pressure rollers are covered with a non-stick material, such as a silicone composition or teflon, so as not to adhere to the upper or lower face of the impregnation grid. The contact surface is also preferably soft and resilient in order to accommodate the geometry of the grid and minimize pinching of the wire.

Alternatively, the mat may be laminated on the grid after cooling. In this case, the mat may be glued to the grid by using an adhesive. Another possibility is to reheat the grid to melt at least a portion of the grid and adhere the mat. Another possibility is to heat the prepreg mat as well to melt the thermoplastic matrix, which then adheres to the grid. Alternatively, the grid and mat may be reheated simultaneously to melt the matrix of the two components and cause them to adhere.

In one embodiment, at least a portion of the grid is covered with a surface density of polymer particles that is at least the same as the surface of the non-impregnated grid. For example, 200g/m²The grid sprinkles at least 200g/m²The polymer particles of (1). The applicant has observed that this allows goodGood impregnation results.

In one embodiment, at least a portion of the grid is covered with polymer particles, the polymer mass being 40% to 60% of the total mass of the impregnated grid.

For example, in one embodiment, the spraying is performed by a particle diffuser (e.g. a vibrating screen), the ratio between the mass Ms of the sprayed particles and the mass Md of the particles deposited thereon being greater than 2, the ratio Ms/Md being greater than 3, preferably greater than 4, preferably greater than 5. In this example, the applicant found that a sufficient amount of particles could be deposited on the wire despite the mesh openings. When the spraying mass Ms is too large with respect to the deposition mass Md, in particular Ms/Md between 5 and 9, the mass Ms is sufficient to obtain a satisfactory impregnation. For example, for a mesh grid of 14 × 14mm, an Ms/Md between 5 and 6 provides advantageous results; for a mesh grid of 28x28 mm, an Ms/Md of between 7 and 9 provides advantageous results.

The purpose of the spraying device is to deposit the polymer particles on the grid. There are a number of means to perform this action: for example, the spraying apparatus comprises a drum with a comb system around the periphery, and then deposits (drops) the powder on the drum on a vibrating screen.

Alternatively, a dispenser with a dispensing control device may be used to deposit particles only on the wire and in a determined amount.

In one embodiment the grid is arranged on a support, such as the conveyor belt of a conveyor, during spraying. At the end of the sprinkling, at least a part of the sprinkled mesh leaves the support before heating, so as to cause the particles accumulated in the mesh to fall by gravity and to be recycled for sprinkling of another section of the grid.

In one embodiment, the particles are between 100 and 600 μm in size.

According to one embodiment, the grid has a polygonal mesh, for example rectangular or square. Alternatively, the grid may have a mesh comprising curved edges.

In one embodiment, the grid comprises a mesh having a mesh opening greater than or equal to 1cm, preferably between 1cm and 6cm, preferably between 1cm and 3 cm.

According to one embodiment, the wire is based on plant fibers, such as flax or from cellulose fibers. In one embodiment, the fibers are selected from flax, hemp, kenaf, nettle, jute, abaca, sisal, bamboo. The strand products based on vegetable fibres usually have some distortion introduced during spinning, which allows to improve the radial compressive strength of the strands, which will have a greater thickness after lamination onto the mat and thus improve the bending reinforcement effect of the grid. The density of the vegetable fibres is also very low, about 1.2-1.6, which allows a greater thickness of the grid for a given weight and therefore a further improvement of the reinforcing effect of the grid. The use of these fibres also reduces the ecological impact of the production of the components reinforced by the grid, due to the natural origin of the wire.

In one embodiment, the strands based on vegetable fibres consist of at least 50% by weight of short fibres from chopped or carded filler. Its short fibers have the advantage of being cheaper than long fibers extracted, for example, when breaking flax, and its use does not impair the mechanical properties of the wire once impregnated with polymer.

According to one embodiment, the wire is based on synthetic fibers, for example on polymers, carbon fibers, glass fibers, basalt fibers or mixtures of these different types of fibers.

According to another embodiment, the wire is based on animal fibres, such as silk or wool.

According to another embodiment, the wire is based on plant fibers and at least one non-plant fiber, such as synthetic fibers. In this embodiment, the wire is based on at least two different fibers.

According to one embodiment, the wires of the interwoven grid are held together by sewing, knitting or weaving very fine wires, for example coated with polyester. This way of assembling the grid has several advantages. It allows the composite product obtained to maintain good adhesion and uniformity even when the impregnating polymer is in a molten state, which is advantageous when molding composite parts by compression molding of the composite product described herein. Furthermore, such assembly with polyester wires still allows a slight sliding between the wires, which allows a large formability in 3 dimensions when molding a composite part by compression molding.

In one embodiment, the heating element is an infrared oven or a convection oven.

According to one embodiment, the melt index of the polymer is greater than or equal to 30 (g/10 min up to 2.16kg according to the standardized test).

In one embodiment, the polymer is selected from polypropylene, polyethylene, polyamide or copolyamides, polyesters or copolyesters, thermoplastic polyurethanes, copolyoxalines, thermoplastic cellulose esters (cellulose acetate propionate), polylactic acid (PLA) or derivatives or mixtures of the above.

In one embodiment, the polymer is selected from thermoplastic polymers such as polypropylene, polyethylene, polyamides or copolyamides, polyesters or copolyesters, thermoplastic polyurethanes, copolyformaldehyde, thermoplastic cellulose esters (cellulose acetate propionate), polylactic acid (PLA).

The composite product is used as a reinforcement or frame to ensure the rigidity, especially the bending rigidity, of the material. The product also allows for improved impact or impact resistance.

The utility model discloses still relate to a device for making compound product, include:

-a sprinkling apparatus comprising means for sprinkling polymer particles on a grid formed by interwoven wires, the wires being based on fibers, the grid comprising an upper face and a lower face opposite to the upper face, the means for sprinkling allowing to sprinkle the upper face of at least a part of the grid with polymer particles so as to cover said upper face with polymer particles;

-a heating device located downstream of the sprinkling device, said heating device comprising a heating element for heating a portion of the grid covered with polymer particles, the polymer particles being heated to a temperature at least equal to the melting temperature of the polymer;

characterised in that the device comprises displacement means arranged to keep said heated part of the grid flat and free of contact above and below said part during heating.

The displacement means are arranged to continuously displace said portion of the grid from the sprinkling device towards the heating device (towards the cooling device if the apparatus comprises a cooling device). In addition, the displacement means are arranged to keep said heated part of the grid flat and free of contact on the upper and lower faces of said part when heating. In other words, when the portion is displaced facing the heating element, or fixed below the heating element, the displacement means keeps it flat and without contact on the lower and upper faces of the heating portion. The displacement means holds the grid by contacting a portion other than the heating portion.

The grid operates under tension, which is tensioned between displacement devices that allow the grid to remain flat during heating and optionally during cooling and sprinkling. The displacement means hold and open the grid by contact with the grid, but outside the portion of the grid located at the location of the heating device and optionally at the location of the cooling device. In other words, it is important to avoid contacting useful parts of the grid, i.e. the heated parts, during heating and optionally cooling. For example, the displacement device comprises an unwinder, a winder and a traction unit, these three elements being positioned outside the heated portion of the grid, and optionally outside the cooled portion of the grid.

The unwinder unwinds the raw grid, i.e. the grid without polymer, in the direction of the winder. The winder exerts a traction force on the grid to put the grid in tension.

The winder winds the composite product downstream of the heating, for example, by means of a cooling unit or cooled in open air.

The unwinder and the traction unit cooperate to control the tension and unwinding speed of the grid (and then the composite product). The drawing unit for example comprises two rollers on both sides of the composite product: upper and lower rollers positioned facing the upper and lower sides of the grid, respectively. The upper and lower rollers rotate in opposite directions, one clockwise and the other counterclockwise, to advance the grid (and then the product) from the unwinder towards the winder. Alternatively, the traction unit may comprise two strips facing each other, or a strip facing the cylinder.

The displacement speed is for example between 0.5m/min and 5m/min, preferably between 1.0 and 2.0m/min, for example 1.5 m/min. The speed of displacement depends on the available heating power: the higher the speed, the greater the heating power should be to ensure melting of the polymer. In particular, the applicant has obtained good results with an infrared heater with a power of 115kW over a grid width of, for example, 1400mm and at a speed of 1.5 m/min.

The space between the upper and lower rollers is selected to control the pressure exerted on the composite product. The pressure should be sufficient to drive the composite product. The pressure should be limited not to degrade the composite product. For example, the spacing is between 0.8 and 1.5 mm.

In one embodiment the device comprises a cooling device downstream of the heating device for cooling said portions, said displacement means being for keeping said heated portions of the grid flat and free of contact above and below said portions during cooling.

The cooling device is used to cool the polymer to solidify the polymer. For example, the cooling device comprises at least one fan that stirs a gas (e.g., air or inert gas) to cool the polymer. Alternatively, the compressed air may be directed onto a grate to force cooling thereof.

In one embodiment, the heated portion remains free of contact and flat during heating, cooling, and between heating and cooling. Thus, the absence of any contact from heating to cooling will change the geometry of the impregnated wire.

In one embodiment, the apparatus comprises a laminating device for laminating the impregnation grid onto the mat, in particular under and/or over the heating section onto the mat.

Preferably, the laminating device is located downstream of the heating device.

In one embodiment, the apparatus comprises a preheating device upstream of the sprinkling device, said preheating device comprising a preheating element for preheating at least a part of the grid to be covered by the particles.

According to one embodiment, the device comprises a recirculation device located downstream of the sprinkling device. The recycling device allows to recover the polymer particles deposited in the meshes of the grid during spraying, which can be reused. The recirculation device is located downstream of the sprinkling device.

According to one embodiment, the device comprises a belt conveyor for holding the grid during spraying. A belt conveyor holding the grid is located upstream of the heating device, which maintains the tension of the grid, which determines the height of the grid below the heating device and contributes to the planar position of the grid at the inlet of the heating apparatus and during heating.

For example, when the device comprises a belt conveyor for displacing the grid during spraying, the recirculation apparatus comprises a container in which the particles flow into the mesh openings of a mesh provided on the conveyor belt.

In one embodiment, the apparatus comprises a cutting device located downstream of the heating device, preferably downstream of the cooling device. The cutting device allows to cut the composite product into strips or sheets of a size determined according to the use of the composite product.

According to the utility model discloses, composite product is sheet or banded. A sheet or strip refers to a planar object defined in a plane (x, y), and wherein the thickness along the z-axis is much smaller than the dimensions along the x-axis and the y-axis. A strip is a sheet of material that is much larger in one dimension than the other in the (x, y) plane.

In the present invention, the term grid is synonymous with mesh and refers to an assembly of wires interwoven with each other to define a mesh. To form the mesh, the wires are integrally connected to one another, for example glued or glued, or held by supporting wires.

In the present invention, the wire is formed of a fiber.

Advantageously, the impregnation grid is easier to handle. The fibers of the wire are at least partially embedded in the polymer. The wires are connected with each other into a whole, and the assembly is not broken when in operation.

The present invention also relates to the use of a grid impregnated with a polymer for manufacturing a composite product comprising said grid and a support, said polymer allowing to integrally connect the grid to said support. The use of a pre-impregnated grid with a molten polymer coating allows to facilitate the adhesion and fixation of the grid on the support. The support may be a mat or any other planar support to be reinforced.

The invention also relates to a composite product comprising, on the one hand, a grid pre-impregnated with a polymer and, on the other hand, a mat pre-impregnated with a polymer that is the same or different from the polymer of the grid. The mat and grid are pre-impregnated, which facilitates adhesion of the grid to the mat.

In the present invention, the term "mat" means a support or plate consisting of fibres organized in a random manner, in other words a sheet or a felt. The mat is a nonwoven material. The present invention preferably relates to lamination onto a mat, but the invention is not limited to this type of support. Supports composed of unidirectional, multidirectional, woven or non-woven fibers may be used.

According to the present invention, the term "composite product" or "composite material" is a product comprising at least two materials, associated, which are different and somewhat homogeneous. The association gives the component properties that the separate adopted components would not have. In the present invention, the composite product may be a grid of wires and polymer, the wires being at least partially impregnated with the polymer. The pre-impregnated wire grid may be embedded in the same or a different polymer than the polymer of the wires. The composite product may also be a pre-impregnated wire grid laminated to a mat, which may also be pre-impregnated with a polymer that is the same or different from the polymer of the wires. In this case, the use of a pre-impregnated grid laminated on a pre-impregnated or non-pre-impregnated mat facilitates the adhesion of the grid. The composite product is then a laminated composite.

The embodiments described for the method according to the invention are applicable in contrast to the device according to the invention, the composite product and the use of the composite product, and vice versa.

Drawings

Embodiments of the invention are pointed out in the description of the invention illustrated in the drawings, in which:

FIG. 1 shows an overall view of a polymer-free green grid useful in the present invention;

fig. 2 shows a block diagram of the invention according to a first embodiment;

figure 3 shows an overall view of a composite product obtained according to a first embodiment;

figure 4 shows a yarn section of the composite product according to the first embodiment;

fig. 5 shows a block diagram of the invention according to a second embodiment;

fig. 6 shows an overall view of a composite product according to a second embodiment of the invention.

List of reference numerals

1 grid

2 composite product

3 raw wire rod

4 cross point

5 mesh

6 above

7 below

10 prepreg

11 Polymer

12 production line

13 spraying device

14 recirculation device

15 heating device

16 Cooling device

17 spreader

18 traction unit

19 winder

20 upper roll

21 lower roller

22 belt conveyor

23 infrared stove

24 impregnated wire

25 upper part of impregnated wire

26 lower part of impregnated wire

27 center portion of impregnated wire

28 vibrating screen

100 laminated composite material

101 cushion

102 production line

103 spraying device

104 recirculation device

105 heating device

106 cooling device

107 spreader

108 traction unit

120 upper roll

121 lower roller

122 belt conveyor

130 laminating apparatus

131 unwinding roller

132 contact roller

133 pressure roller

134 cutting device

135 laminating the composite sheet.

Detailed Description

Fig. 1 to 6 show two embodiments of the invention, but the invention is not limited to the embodiments shown in fig. 1 to 5.

Fig. 1 shows a grid 1 that can be used in the present invention to manufacture a composite product 2. The grid 1 shown in fig. 1 is a grid before spraying and impregnation, in other words a raw grid, that is to say without polymer. The grid 1 comprises wires 3 interwoven with each other. The wires 3 are glued or sewn to each other at each crossing 4. The grid 1 has rectangular polygonal meshes 5 of dimensions 14x14mm or 28x28 mm. But a grid with a mesh of 10 to 60mm, for example polygonal, may also be used.

The grid 1 comprises an upper face 6 and a lower face 7.

The grid 3 is based on flax fibres. In this embodiment, the wire is based only on flax, but wires made of different materials may be used, or wires based on a plurality of different types of fibres, such as hemp, kenaf, nettle, jute, abaca, sisal, cotton, bamboo, polymer fibres, carbon fibres, glass, basalt, aramid.

Fig. 2 shows a device according to a first embodiment for manufacturing the composite product 2 shown in fig. 3. In this embodiment, the composite product 2 is a prepreg 10 comprising a grid 1 impregnated with a polymer 11.

The apparatus of this first embodiment shown in fig. 2 is a production line 12 comprising a spraying device 13, a recirculation device 14, a heating device 15, a cooling device 16.

In order to ensure the displacement of the grid 1 from the heating device 13 to the cooling device 16, the production line 12 comprises an unwinder 17, a drawing unit 18 and a winder 19. The spreader 17 spreads the polymer-free grid 1 made of so-called raw wires 3 toward the spraying device 13. A drawing unit 19 is positioned after the cooling device 14 and draws the grille 1 in front of each device of the production line 12. The drawing unit 18 comprises an upper roller 20 facing the upper face 6 and a lower roller 21 facing the lower face 7. The grid 1 is held between an upper roller 20 and a lower roller 21, which allows pulling said grid 1. Winder 19 winds prepreg 8 to the end of line 12. In this example, the grid is at 1.5m.min^-1Is shifted.

The production line 12 allows to pass a portion of the grid successively through a spraying device 13, a recirculation device 14, a heating device 15 and a cooling device 16. Before the spraying device 13, a portion of the grid 1 has the wires 3 in raw state; after the cooling device 16, the raw grid section has been converted into a prepreg section 10.

At the beginning of line 12, at the outlet of spreader 17, grille 1 rests on the belt of belt conveyor 22, belt conveyor 22 holding grille 1 facing spraying device 13 and guiding grille 1 towards recirculation device 14. In this line 12, the sprinkling device 13 is a vibrating screen 28 that sprinkles polymer particles on the entire surface of a portion of the grid 1, in other words on the strands 3 of the grid and in the mesh openings 5. For example, for a 14x14mm grid, the screen sprinkles 1200 to 1300 g.m^-2So as to remain on the strand 3 after the recycling device of 200 to 240 g.m. (spray mass Ms)^-2Of polymer particles (deposition mass Md), the ratio Ms/Md being between 5 and 6. Therein, theIn the examples, the polymer 11 is polypropylene. For 28X28 mm grid, the sieve sprays 1700-1900g.m^-2(Ms) to obtain 200-240 g.m^-2(Md)。

The belt of conveyor 22 allows to collect the polymer particles in mesh 5 to convey them towards recirculation unit 14.

The sprayed part of the grid then passes through a heating device 15. The heating device 15 is here an infrared oven 23. The infrared oven 23 heats the portion that has been sprinkled with polypropylene (PP) from above, i.e. from above 6, to a temperature of 200 to 220 ℃. The PP melts and protects the flax fibers of the strand 3 from infrared radiation so that the flax remains below 185-190 ℃ and does not burn.

At the heating outlet, the heated portion passes through a cooling device 16. In this embodiment the cooling device 16 comprises an air fan (not shown in the figure) positioned facing the upper side 6.

During heating and cooling, the heated portions are tensioned and do not come into contact due to the tension applied by the pulling unit 18.

At the outlet of the drawing unit 18, the prepreg 10 is wound on a winder 19.

Fig. 4 shows a section of impregnated wire 24, which shows an asymmetric impregnation of wire 24. Impregnation allows converting the raw wire 3 into an impregnated wire 24. The wires 24 of the prepreg 10 include an upper portion 25, a middle portion 27, and a lower portion 26. The upper portion 25 is the portion exposed on the upper face 6 of the grid; the lower portion 26 is the portion exposed on the underside 7 of the grille 1.

The upper portion 25 is impregnated deeper than the lower portion 26. In fact, the polymer 9 is deposited on the upper face 6 and melts starting from the upper face 6. A portion of the molten polymer impregnates the upper portion 25 of the wire 24. The polymer 11 of the upper portion 25 of the unimpregnated strands 24 flows by gravity around the strands 24 and becomes gradually impregnated. Thus, an asymmetric distribution of the polymer is obtained: in the lower part 27 of the wire, less molten polymer is available than in the opposite part, and therefore less deep impregnation occurs. The depth of impregnation is typically 40-80% of the wire radius in the upper part, 20-60% of the radius in the middle part and 10-40% in the lower part. Or in other words, asymmetric impregnation is characterized in that 40-90% of the impregnating polymer is present in the upper part, 10-50% in the middle part and 0-20% in the lower part.

The central portion 27 of the wire 22 is barely or even not impregnated, and the majority of the polymer is distributed between the upper and

lower portions

25, 26 and the sides of the intermediate portion.

The molten polymer substantially fills the voids between the fibers making up the raw wire 3 such that the impregnated wire 24 typically has a diameter about 5-20% larger than the raw wire 3. Fig. 5 shows a device according to a second embodiment for manufacturing the composite product 2 shown in fig. 6. In this embodiment the composite product 2 is a laminated product 100 comprising a prepreg 10 laminated on a support, here a mat 101.

The apparatus of this second embodiment shown in fig. 5 is a production line 102 comprising a spraying device 103, a recirculation device 104, a heating device 105, a cooling device 106. These devices are the same as those of the first embodiment of the production line 12.

As in the production line 12 according to the first embodiment, the production line according to the second embodiment includes the unwinder 107 and the drawing unit 108, and the belt conveyor, which operate as in the production line 12 according to the first embodiment.

The production line 102 according to the second embodiment allows for the manufacture of a laminated composite material 100. To this end, the production line 102 comprises a laminating device 130 located between the heating device 105 and the cooling device 106. The laminating apparatus 130 includes an unwinding roller 131, a contact roller 101, and a pressure roller 133. The mat 101 is wound on an unwinding roller 131. Contact roller 132 and pressure roller 133 are positioned to face lower face 7 and upper face 6, respectively.

The unwinding roller 131 unwinds the mat 101 toward the contact roller 132. The contact roller 132 guides the mat towards the underside 7 of the grid. The lower face 7 comprises at least a portion of a polymer 11 in the molten state, which can have an adhesive function. The mat and prepreg are sandwiched between a (sandwich) contact roll 132 and a pressure roll 133. The spacing between the contact roller 132 and the pressure roller 133 corresponds to a distance slightly less than the sum of the thickness of the mat and the thickness of the impregnated wire 22, typically 5-20% less, so that the mat 101 and the prepreg 10 are slightly pressed against each other. The distance preferably depends on the type of mat. This allows for improved adhesion of the prepreg 10 on the mat 101, thereby minimizing thickness variations of the impregnated wire 24 as much as possible.

In an embodiment not shown, lamination is performed on the upper face 6. In another embodiment, not shown, lamination is performed on the upper side 6 and the lower side 7.

Downstream of the laminating apparatus 130, a cooling apparatus 105 cools the laminated composite material 100 at the exit of the laminating apparatus 130.

The production line 102 also comprises a cutting device located downstream of the cooling device 10. The cutting apparatus 134 allows the laminated composite material 100 to be cut into sheets 135 of a predetermined size.

A laminated composite sheet 135 obtained from the production line 102 is shown in fig. 6. The sheet 135 includes the prepreg 10 and the mat 101.

Claims

1. A composite product comprising a grid and a polymer,

-the grid comprises an upper face and a lower face opposite to the upper face,

-each wire has an upper portion on the upper face of the grid, a lower portion on the lower face of the grid, and an intermediate portion between the upper and lower portions,

it is characterized in that the preparation method is characterized in that,

-the wires of the grid are impregnated with the polymer, the impregnation being asymmetric such that the upper portion of the wires comprises a greater amount of impregnated polymer relative to the lower portion and the middle portion.

2. The composite product according to claim 1, characterized in that the asymmetric impregnation is characterized by an impregnation depth of the polymer on the radius of the wires of between 40% and 80% of the radius of the wires in the upper portion, between 20% and 60% of the radius in the middle portion and between 10% and 40% of the radius in the lower portion.

3. The composite product according to claim 1, characterized in that the asymmetric impregnation is characterized in that between 40-90% of the impregnating polymer is in the upper part; 10-50% in the middle portion; and 0-20% in the lower portion.

4. The composite product according to claim 3, characterized in that between 60-90% of the impregnating polymer is in the upper part, 10-30% in the middle part and 0-10% in the lower part.

5. Composite product according to any one of claims 1 to 4, characterized in that the fibres are selected from plant fibres.

6. The composite product according to claim 5, characterized in that the fibres are selected from flax, hemp, jute, cotton, kenaf, nettle, abaca, sisal, bamboo.

7. Composite product according to claim 6, characterized in that the fibres are flax.

8. Composite product according to any one of claims 1 to 4, characterized in that the fibres are selected from animal fibres.

9. Composite product according to claim 8, characterized in that the fibres are silk or wool.

10. Composite product according to any one of claims 1 to 4, characterized in that the fibres are selected from vegetable fibres, wherein at least 50% by weight of the short fibres are derived from chopped or carded filler.

11. The composite product according to claim 10, characterized in that the fibres are selected from flax, hemp, jute, cotton, kenaf, nettle, abaca, sisal, bamboo.

12. Composite product according to claim 11, characterized in that the fibres are flax.

13. Composite product according to any one of claims 1 to 4, characterized in that the polymer is selected from polypropylene, polyethylene, polyamide or copolyamides, polyesters or copolyesters, thermoplastic polyurethanes, copolyoxymethylenes, thermoplastic cellulose esters, polylactic acid.

14. Composite product according to any one of claims 1 to 4, characterized in that the wires of the mutually interwoven grids are held together by sewing, knitting or weaving very fine wires.

15. Composite product according to claim 14, characterized in that the very fine wires are coated with polyester.

16. Composite product according to any one of claims 1 to 4, characterized in that the impregnating polymer represents between 40% and 60% of the total mass of the product.

17. The composite product according to any one of claims 1 to 4, further comprising a support on which the impregnated grid is laminated.

18. The composite product according to claim 17, wherein the support is a mat.

19. The composite product according to claim 17, characterized in that it comprises two supports for forming a sandwich stack, each support being located on either side of the grid.

20. The composite product according to claim 17, characterized in that the support is selected from woven supports, non-woven supports, supports made of unidirectional or multidirectional fibres, mats, tablecloths, felts.

21. The composite product according to claim 17, characterized in that the support is pre-impregnated with a polymer which is the same or different from the polymer of the grid.

22. The composite product according to any one of claims 1 to 4, wherein the grid comprises meshes having mesh openings greater than or equal to 1 cm.

23. The composite product according to claim 22, wherein the mesh has a mesh opening of between 1cm and 6 cm.

24. The composite product according to claim 23, wherein the mesh has a mesh opening of between 1cm and 3 cm.

25. A composite product according to claim 22, characterised in that the mesh is polygonal.

26. The composite product according to claim 25, wherein the mesh is rectangular or square.