EP1692334A1

EP1692334A1 - Fibre-based reinforcing product and production method thereof

Info

Publication number: EP1692334A1
Application number: EP04805463A
Authority: EP
Inventors: Gilbert Chomarat
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-11-17
Filing date: 2004-11-16
Publication date: 2006-08-23
Also published as: FR2862316A1; FR2862316B1; WO2005049906A1

Abstract

The invention relates to a reinforcing product which is made from yarns (2) comprising blended filaments of glass and thermoplastic materials, said yarns being cut such as to form fibres (6) which are then treated in a card (8) in order to form a thin coherent web (9). The web (9) is subsequently assembled with a suitable support (15) using a hot press gluing device (16). In this way, reinforcing products based on glass fibres and other reinforcing fibres can be produced continuously and inexpensively.

Description

FIBER-BASED REINFORCEMENT PRODUCT AND METHOD FOR THE PRODUCTION THEREOF

TECHNICAL FIELD OF THE INVENTION The present invention relates to reinforcing products used in the field of composite materials and intended to enter into the composition of parts or products to give them improved mechanical properties. The invention relates more specifically to reinforcing products intended to constitute flat or shaped structural elements, which can be incorporated into a matrix during the manufacture of a shaped part. The invention is based on the use of staple fibers, which will be designated by the expression "sections of filaments", of equal or unequal lengths and obtained from glass filaments mixed with filaments of thermoplastic material. The documents EP-A-0 599 695 and EP-A-0 616 055 describe methods for producing such mixed mixed yarns composed of glass filaments and filaments of an organic thermoplastic material. In all of the applications described, the composite wires themselves constitute the essential reinforcement structure, and the mechanical properties obtained are determined by the orientation of the wires themselves. Reinforcement products based on yarns already constituted by a combination of glass filaments and filaments of thermoplastic material are already known. For example, document FR 2 797 892 uses such wires to form two plies of perpendicular wires which are hot pressed against each other to ensure their bonding and constitute a plate. Document FR 2 784 931 uses these same threads to form a composite tape, the threads being placed longitudinally side by side in a sheet and hot pressed to form the tape. Document FR 2 779 988 uses these same threads by arranging them in the form of sheets which can be incorporated into a mold to be embedded in a matrix during the manufacture of a part by molding. A drawback is that these stranded structures lack flexibility in implementation, in particular by the fact that the strands must be placed in the form of plies, which can be relatively easy in the longitudinal direction during production. continuous, but which is then more delicate when you want to arrange the wires in the transverse direction. Also, these applications are limited to the use of glass as a mechanical reinforcing element. Document EP 0 815 307 describes the use of plies of wires mixed with glass and a thermoplastic material. The use of a carding step is not described. The fibers are formed into a plate 3 millimeters thick, constituting in itself a reinforcing product in which the thermoplastic material acts as a matrix. The document EP 1 093 900 describes the manufacture of a composite ribbon based on glass fibers and fibers of thermoplastic material. The fibers are continuous. Document JP 1 207 458 A describes the manufacture of a molded composite product having a basis weight of 150 to 300 grams per square meter, composed of a mixture of glass fibers and fibers of thermoplastic resin. The method includes a carding step. The composite product obtained is ready to be molded, and constitutes in itself a reinforcing element in which the thermoplastic material constitutes the matrix. Furthermore, it is known that the carding technique of glass fibers is not industrially applicable for the production of a card web of low grammage. Indeed, when the fibers to be carded have a diameter greater than 8 or

10 μm approximately, thick sheets are obtained, used mainly as insulating materials. However, it is industrially very difficult to obtain a card web having a grammage as low as about 20 to 100 grams per square meter. PRESENTATION OF THE INVENTION The object of the invention is to design new reinforcing structures based on fibers which can both be produced economically by industrial processes, and be implemented in a particularly flexible manner for adapt to the majority of applications. The invention therefore seeks to take advantage of the advantageous properties of mixtures of glass filaments and filaments of thermoplastic material, which can be assembled by simple heating under pressure producing adhesion. The invention aims to have such a mixture of glass filaments and filaments of thermoplastic material in a form which is economical to produce, and which is especially available in very small thickness to control the quantities of thermoplastic material and allow compatibility in applications requiring minimization of the presence of the thermoplastic material. For this, the invention results from the surprising observation according to which staple fibers, of equal or unequal lengths, are cardable and allow the formation of a thin web of bond and a weight of the order of 20 to 40 g / m ² , when they are obtained from son made of continuous filaments of glass mixed with continuous filaments of thermoplastic material, or are obtained by an appropriate homogeneous mixture of sections of precut glass filaments and sections of precut filaments of thermoplastic material. To achieve these and other aims, the invention provides a reinforcement product comprising a coherent bonding web, consisting of a homogeneous mixture of sections of oriented glass filaments and sections of oriented filaments of thermoplastic material. The sections of filaments of thermoplastic material ensure a certain attachment in the card, and protect the sections of glass filaments against their tendency to break. It is thus possible to card traditional glass fibers whatever the diameter of the unitary filaments. Carding gives the veil its coherence, by an ordered tangle of sections of filaments which ensures their connection, and preferably directs the sections of filaments in the direction of movement of the card. In the reinforcement product, the bonding veil is made to adhere to a support based on reinforcing fibers. The connecting veil can thus connect together by adhesion of the reinforcing fibers, and constitutes a resistant connecting element. The connecting veil may advantageously have a weight of approximately 15 g / m ² to approximately 100 g / m ² , advantageously approximately 20 g / m ² . In the present description and in the appended claims, the expression "co-mixed" is used to denote yarns composed of glass filaments and filaments of thermoplastic material which are mixed within the yarns, these yarns being generally obtained by assembly filaments directly during their manufacture, for example, and without limitation, according to the methods described in documents EP-A-0 599 695 or EP-A-0 616 055. The filaments of the two types of material are intimately mixed , preferably homogeneously in the wire. From such co-mixed filaments, it is possible to obtain sections of co-mixed filaments which have both good properties for carding and a composition which is satisfactory for subsequent operations of assembly, bonding and applications requiring a small proportion of thermoplastic material. Alternatively, it is also possible to prepare a suitable homogeneous mixture of sections of glass filaments and sections of material filaments. thermoplastic by cutting separate filaments of glass and thermoplastic material, and ensuring sufficient mixing, that is to say in which there is substantially an alternation of sections of glass filaments and sections of filaments of thermoplastic material. Preferably, in the mixture, the sections of glass filaments are present in a proportion of between 50 and 80% by weight approximately, and the sections of filaments of thermoplastic material are present in a proportion of between 50 and 20% by weight approximately. In the mixture, the sections of glass filaments may have a diameter of between 10 and 24 μm approximately, and the sections of filaments of thermoplastic material may have a diameter of between 10 and 30 μm approximately. These dimensions are compatible with the economic requirements of industrial production, with a diameter of glass filaments sufficiently large for economic production, the presence of filaments of thermoplastic material ensuring the efficiency of the carding operation for the formation of the web. . To ensure carding with traditional cards, it is advantageous to provide that, in the mixture, the sections of filaments have a length of between approximately 30 mm and 60 mm. The thermoplastic material can be chosen from the group comprising polyester, polyolefins, polyamides, polyacrylonitriles, polyethylene terephthalate, polybutylene terephthalate. In the connecting web, the sections of filaments can advantageously partially adhere to each other by the thermoplastic material. This adhesion is ensured by appropriate static or dynamic heating after carding, then by cooling. According to a first application, the connecting veil can be continuous and monolayer. In this case, the fibers are oriented essentially in the longitudinal direction, producing a reinforcing structure with preferential longitudinal action. Alternatively, if a greater thickness is desired, the connecting veil can be zigzag-coated, and the adjacent sections of connecting veil can adhere to one another by the thermoplastic material. This produces a connecting web whose fibers are preferably oriented in oblique directions, constituting a reinforcing structure with transverse action without having to weave or sew transverse fibers. The connecting veil according to the invention finds important applications in the production of composite reinforcing structures. A first possibility consists in making the bonding web adhere by the thermoplastic material to a support based on reinforcing fibers such as glass fibers, carbon fibers, aramid fibers. For example, the support may be a sheet of parallel continuous wires, oriented longitudinally, or possibly oriented transversely. In both cases, the connecting veil can adhere to one face of the web of continuous wires. According to another example, the successive continuous son of the ply adhere alternately on either side of the connecting veil. Another possibility is to adhere the connecting veil to a support in the form of a grid of fibers oriented in at least two directions. A thicker product can be produced by providing a stack of layers of continuous glass, carbon or aramid yarns, having a connecting veil inserted between each pair of successive layers and adhering to one and the other of said successive layers. . As an alternative or in addition, provision may be made for several layers of bonding web to be needled by jets of water or possibly to adhere to a support based on reinforcing fibers such as glass fibers, carbon fibers, aramids. It is also possible to add to the mixture sections of filaments made of another material such as flax, hemp, sisal, jute, wool. According to an advantageous embodiment, the mixture can also contain sections of filaments obtained from single-strand crimped thermoplastic material whose melting temperature is higher than that of the thermoplastic material of the sections of filaments, constituting an elastic assembly. It is also possible to add to the composite structure thus formed at least one non-woven veil of glass, of polyester, which can adhere to the coherent bonding veil. .In an advantageous embodiment, the homogeneous mixture can contain sections of oriented glass filaments, sections of oriented polyester filaments, and sections of oriented polypropylene or polyethylene filaments. The quantity of thermoplastic filaments (polyester, polypropylene, polyethylene) is sufficient to allow carding without breaking the glass filaments. And the quantity of material useful for the adhesion of the bonding web can be reduced by an appropriate selective softening of only the sections of polypropylene or polyethylene filaments. The connecting veil then adheres to reinforcing fibers by the only sections of oriented filaments of polypropylene or polyethylene. The same effect can be sought in the absence of polyester, by simultaneous use of sections of polypropylene filaments and sections of polyethylene filaments, and by carrying out a selective softening of the polyethylene. ^• According to another aspect, the invention proposes a method for producing the reinforcement product with a coherent bonding veil consisting of a mixture of sections of oriented filaments containing sections of glass filaments; the process comprises the steps: a) preparing a homogeneous mixture of sections of glass filaments and sections of filaments of thermoplastic material, of a length suitable for a carding operation, the sections of glass filaments being homogeneously mixed with sections of filaments of thermoplastic material, b) treating this mixture of sections of filaments in a card to produce a coherent veil of sections of oriented filaments. The homogeneous mixture of sections of filaments can advantageously be obtained by cutting off son made up of glass filaments co-mixed with filaments of thermoplastic material. Alternatively, the mixing can result from cutting glass filaments and thermoplastic filaments which are then mixed until the appropriate homogeneity is achieved. By the fact that the card orientates the sections of glass filaments longitudinally, a connecting veil with preferential longitudinal reinforcement action is produced. According to another possibility, the method can comprise an additional step c) according to which, at the outlet of the card, the connecting web passes through a lapper which folds it in a zigzag. This produces a connecting web having transverse reinforcing properties, which are a function of the angle at which the sections of the web are folded. Then, according to a step d), it is possible optionally to apply the bonding veil on a support based on fibers. And there is provision for a subsequent step e) of membership, during which:

the constituents of the reinforcement product are heated to a temperature sufficient to give the thermoplastic material adhesive properties,

- the components are pressed against each other, - The assembly is cooled, and the pressure is released to release the reinforcement product. SUMMARY DESCRIPTION OF THE DRAWINGS Other objects, characteristics and advantages of the present invention will emerge from the following description of particular embodiments, made in relation to the attached figures, among which:

- Figure 1 is a schematic perspective view illustrating a connecting web structure according to a first embodiment of the present invention;

- Figure 2 illustrates in perspective a connecting web structure according to a second embodiment of the present invention;

- Figure 3 is a cross section of a reinforcing structure connecting web and sheet of longitudinal fibers according to the invention;

- Figure 4 is a cross section of another reinforcement structure with connecting web and longitudinal fibers according to the invention; - Figure 5 is a cross section of another reinforcement structure with connecting web, longitudinal fibers and additional layer according to the invention;

- Figure 6 schematically illustrates the cross section of a composite wire with glass filaments and filaments of thermoplastic material which can be used according to the invention; - Figure 7 is a schematic view of an installation for manufacturing reinforcement products according to one embodiment of the invention;

- Figure 8 is a schematic perspective view partially illustrating the installation for manufacturing reinforcing products of Figure 7;

- Figure 9 is a perspective view partially illustrating the installation of reinforcing products of Figure 7, according to another embodiment;

- Figure 10 schematically illustrates, in cross section, another reinforcing structure according to the invention stacking several layers of continuous son bonded to each other by connecting webs;

- Figure 1 1 schematically illustrates, in cross section, a thick veil according to the invention, based on glass fibers and plastic fibers including monofilaments crimped in thermoplastic material at higher melting temperature;

- Figure 12 illustrates in cross section a reinforcement product according to another embodiment, comprising several layers of veil needled by water jets and glued to a support; and - Figure 13 schematically illustrates in cross section another reinforcement structure according to the invention, including partially melted hot melt fibers. DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will first be made to FIG. 7, which schematically illustrates an installation for manufacturing reinforcement products according to one embodiment of the invention. This installation firstly comprises a wire reserve 1, containing a wire 2 formed from glass filaments co-mingled with filaments of a thermoplastic material. A possible structure of such a composite yarn is illustrated in cross section in FIG. 6, in which a distinction is made between the glass filaments 3 shown in dark and the thermoplastic filaments 4 shown in clear. It can be seen that the distribution of the glass filaments 3 and the filaments of thermoplastic material 4 is relatively uniform in the cross section of the wire 2. In FIG. 7, the reserve of wire 1 is for example a coil from which the wire 2 is unwound. to bring it to a cutting device 5 which cuts the wire into sections of suitable length to then allow the carding of the fibers. The cutting length can advantageously be between approximately 30 mm and 60 mm, although different lengths can be chosen depending on the structure of the card which is then used. The cut fibers 6, or sections of filaments, which exit from the cutting device 5 are collected in a reserve of fibers 7, which then feeds them in an appropriate manner in a carding machine 8. A mechanical carding machine 8 such as those which are traditionally used in the textile industry, comprising a rotary cylinder equipped with teeth or needles which rotate in front of workers to drive the sections of filaments by painting them, thereby producing a continuous, thin web 9 in which the sections of filaments 9a are preferably oriented in the longitudinal direction 10 of travel of the web 9. Alternatively, a pneumatic card can be used, generating an air flow which orients the sections of filaments by painting them. We can refer to Figure 1, which illustrates in perspective on a larger scale the structure of the connecting web 9, formed of sections of carded filaments 9a preferably oriented in the longitudinal direction. In the embodiment of Figure 7, the web 9 is then treated by a lapper 1 1 which performs a cross transverse folding. At the outlet of the lapper 1 1, a lapped connecting veil 12 is collected, the structure of which is more clearly illustrated in FIG. 2: by successive folds crossed in zigzag, a continuous strip is produced which travels in the longitudinal direction 13, formed of '' a succession of sail sections such as the adjacent sections 12a and 12b, which are oriented transversely obliquely to the longitudinal direction 13. Thus, the section 12a makes with the longitudinal direction 13 an angle A, while the section 12b makes with the same longitudinal direction 13 an angle B. The angles A and B can be equal and opposite, and are less than 90 ° and greater than 45 °. Depending on the angle chosen, a more or less complete covering of the successive sections 12a and 12b is carried out on each other, which allows the thickness of the coated web 12 thus obtained to be adjusted to a certain extent. In the embodiment illustrated in FIG. 7, the coated web 12 is then treated by an assembly device 14 which assembles the coated web 12 by adhesion with a support 15 based on reinforcing fibers such as glass, carbon fibers, aramid fibers. A support 15 is illustrated, consisting of a sheet of wicks of parallel fibers. We can for example use with advantage roving wicks in glass from 160 Tex to 4,800 Tex, or glass strands from 34 Tex to 544 Tex. The assembly device 14 ensures the heating of the constituents to a temperature sufficient to give the thermoplastic material of the bonding web adhesive properties, and presses the constituents against each other. The temperature is advantageously chosen only slightly below the melting temperature of the thermoplastic material considered. For example, for polyethylene, about 120 ° C - 140 ° C will be chosen. The components can then be allowed to cool in the ambient air. Preferably, downstream of the assembly device, a cooling device 16 is provided which cold presses the constituents between two or more rollers to cool them and to freeze the thermoplastic material. At the outlet of the assembly device 14 or the cooling device 16, the reinforcing product 17 is collected, either in a continuous strip which can be packaged in coils, or in cut plates. An example of an assembly device 14 is illustrated diagrammatically in FIG. 8. In this case, the assembly device 14 processes a lapped connecting web 12 emerging from the lapper 1 1. The assembly device 14 comprises in particular two pressing means 14a and 14b in opposition to each other, between which is passed both the coated web 12 and a support 15 from a reserve of support 18. In the illustrated embodiment, the support 15 is a sheet of wicks of parallel fibers, which may be made of carbon, aramids or the like. Alternatively, the support 15 can be a grid of fibers oriented in at least two directions, preformed and packaged in the reserve of support 18. The pressing means 14a and 14b ensure both the plating of the coated connecting web 12 and the support 15 one on the other, and the maintenance of a satisfactory pressure. They can also be heated to ensure heating of the assembly up to a temperature ensuring sufficient softening and adhesion of the thermoplastic material contained in the composite fibers constituting the lapped bonding web 12. Alternatively, heating can be provided by hot sources such as infrared radiation sources upstream of the rollers, and the rollers 14a and 14b can press the components without heating them. At the outlet of the assembly device 14, by the effect of sufficient softening of the thermoplastic material, then by the effect of the cooling which freezes the thermoplastic material, the coated bonding web 12 adheres to the support 15, the composite fibers of the coated web 12 partially adhere to each other, and adjacent sections such as sections 12a and 12b of web coated 12 also adhere to each other. FIG. 3 illustrates, in cross section, the structure of the reinforcement product obtainable by using such an assembly device 14 and a monolayer support 15, in an application in which the assembly device 14 treats a house veil 9 which has not been coated. We distinguish the connecting web 9, forming the upper layer, and we distinguish the support 15 forming the lower layer and consisting of a sheet of longitudinal fibers such as fiber 15d. FIG. 9 illustrates a variant of the assembly device 14, in an installation in which the assembly device 14 directly processes a connecting web 9 coming out of the card 8. In this variant, the support 15 is formed of two partial supports , namely a lower support 15a coming from a lower reserve of support 18a, and an upper support 15b coming from an upper reserve of support 18b. The lower support 15a is pressed against the underside of the connecting veil 9, while the upper support 15b is pressed against the upper face of the connecting veil 9, the assembly being compressed by the pressing means 14a and 14b. At the outlet, a reinforcing product is obtained as illustrated in the cross section in FIG. 4, in which a distinction is made between the connecting web 9 which takes on a wavy shape, the fibers of the lower support 15a being located under the underside of the connecting web 9, the fibers of the upper support 15b being on the upper face of the connecting web 9. In the case of supports 15a and 15b in the form of sheets of continuous threads, the strands of successive fibers, when we consider the reinforcement product in cross section, adhere alternately on either side of the connecting veil 9. Naturally, this arrangement also applies to a lapped connecting veil 12. In all cases, the pressing means 14a and 14b which ensure the compression and heating of the materials can be associated, downstream, with cooling means which ensure rapid setting of the thermoplastic material. For clarity, in Figures 8 and 9, the pressing means 14a and

14b have been schematically illustrated by rollers. In reality, it is advantageously possible to use pressing belts, for example as described in the document US Pat. No. 4,997,507. Two opposite pressing belts can provide heating and compression upstream in the assembly device 14, two other opposite pressing belts providing cooling downstream with pressure maintenance in the cooling device 16. In the embodiment illustrated in the figure 5, we find the structure of reinforcement product illustrated in FIG. 3, with a carded connecting veil 9 and a lower reinforcement 15, with in addition at least one nonwoven veil 19 of glass, of polyester, adhering to the connecting veil 9 carded. Considering again the installation illustrated in FIG. 7, it will be understood that this installation can be simplified in the case where it is desired to produce reinforcing products as illustrated in FIGS. 3, 4 or 5. Indeed, in this case, a lapper 11 is not used. Also, the installation of FIG. 7 as illustrated uses cut fibers 6 coming only from the reserve of threads 1 containing a composite thread 2 comprising co-mixed filaments glass and thermoplastic material. Alternatively, the wire reserve 1 can separately deliver continuous filaments of glass and continuous filaments of thermopiastic material, which the cutting device 5 cuts. The sections of filaments are mixed in the cutting device 5 and / or the fiber reserve 7 to produce a homogeneous mixture where the glass and the thermoplastic material are found in generally constant proportions. In addition, it is also possible to add to the reserve of fibers 7, by mixing them, sections of filaments of different nature, for example sections of filaments of flax, hemp, sisal, jute, wool. These fibers are then found in the connecting web 9. The thermoplastic material used will be chosen according to the intended uses of the reinforcing product. For example, thermoplastic materials compatible with the other materials in which the reinforcing product is to be incorporated will be used. Depending on the uses, the thermoplastic material may be chosen from the group comprising polyester, polyolefins including polypropylene, polyamides, polyacrylonitriles, polyethylene terephthalate, polybutylene terephthalate. Polyethylene or polypropylene may be of interest due to their low melting temperature. The support 15 based on reinforcing fibers may consist of glass fibers, carbon fibers, aramid fibers. It may be advantageous to use plies of wicks of parallel fibers. In the wire 2 used to make the connecting web 9 by carding, it may advantageously be provided that the glass filaments will have a diameter of between 10 and 24 μm approximately, the filaments of thermoplastic material having a diameter of between 10 and 30 μm approximately , the glass filaments being present in a proportion of between 50 and 80% by weight approximately, and the filaments of thermoplastic material being present in a proportion of between 50 and 20% by weight approximately. In the support 15, the wicks of fibers can be longitudinal, or can be oriented transversely or obliquely, depending on the desired mechanical properties of the reinforcing product. It is also possible to produce circular disc-shaped parts, by depositing on the veil a disc-shaped support consisting for example of strands of wire wound in a spiral. The same technology can be used to produce parts having other contours, for example rectangular, triangular, polygonal contours, with a flat or left surface. In the embodiment illustrated in FIG. 10, the reinforcement product according to the invention comprises a stack of several plies of continuous wires 15a, 15b, 15c and 15d, each of which may be made of glass, carbon or aramids. These materials can be identical or different for each layer, depending on the overall properties sought for the reinforcement product. A veil 9a, 9b or 9c is inserted between each pair of successive layers, respectively 15a and 15b, 15b and 15c, 15c and 15d. The sails 9a, 9b and 9c adhere to the successive layers, and connect them to each other. In the embodiment illustrated in Figure 1 1, to achieve the connecting veil according to the invention, one starts from a mixture which, in addition to the sections of glass filaments and the sections of filaments of thermoplastic material, also contains sections of filaments obtained from single strands of thermoplastic material whose melting temperature is higher than that of the thermoplastic material of the sections of filaments. Thus, in the connecting veil 9 thus formed, there are for example the sections of filaments of glass fibers 3 co-mingled with the sections of filaments of thermoplastic material 4, with in addition the sections of crimped filaments 20 made of thermoplastic material with higher melting temperature. For example, the sections of filaments of thermoplastic material 4 can be made of polyethylene, while the sections of crimped filaments made of thermoplastic material can be made of polypropylene having previously received a texturing treatment, for example by stuffing, giving them permanent crimping. After formation of the bonding web, the heat treatments soften the polyethylene forming the sections of filaments of thermoplastic material 4 to ensure adhesion, but the temperature remains significantly lower than the melting temperature of the polypropylene single strands, which do not melt and do not not soften, and which retain their elastic properties conferred by texturing. The assembly thus retains an elasticity given by the sections of crimped filaments made of thermoplastic material at high melting temperature, and can be calendered to fix the thickness thereof. This produces an elastic material, without having to resort to a sewing knitting procedure. In the embodiment of FIG. 12, several layers of veil 9a, 9b and 9c are provided which are needled by jets of water and which optionally adhere to a support 15 based on reinforcing fibers such as glass fibers, carbon fibers, aramid fibers. Needling by water jet consists in pushing veil fibers in the thickness direction, and the sections of filaments 21, 22 and 23 are shown diagrammatically, by way of example, which connect two successive layers of veil 9a, 9b or 9c. A thick veil is thus produced, capable of being used for example as a sealing reinforcement. In the embodiment of Figure 13, there is provided for example a layer of bonding web 9 which adheres to a support 15 based on reinforcing fibers. The coherent connecting web 9 is made up of a homogeneous mixture of sections of oriented glass filaments 3, of sections of oriented polyester filaments 4a, and of sections of oriented polypropylene filaments or of polyethylene 4b. For the adhesion of the connecting web 9 on the support 15, selective softening is ensured only of the sections of polypropylene or polyethylene filaments 4b, which melt at a temperature below the melting temperature of the sections of polyester filaments 4a. In this way, it is possible to limit the quantity of material which ensures adhesion, while retaining an overall quantity of thermoplastic material sufficient to allow carding in good conditions without breaking the sections of glass filaments. In practice, it will be possible to choose a total quantity of sections of thermoplastic material sufficient to allow carding under good conditions, and a quantity of sections of oriented filaments of polypropylene or polyethylene 4b sufficiently small so that, during softening, the haze of connection 9 remains in the state of a discontinuous wall, comprising interstices which favor the subsequent passage of a matrix during the incorporation of the reinforcing element for the manufacture of a part. The sections of polypropylene or polyethylene 4b filaments are in a quantity just sufficient to ensure adhesion of the fibers of the support 15. An example of reinforcing product is the following: a sheet of continuous glass son of 720 g / m ² , composed six threads to the centimeter of a roving of 1200 Tex, laminated on a card web of 40 g / m ² (two layers), the sections of filaments of which are oriented mainly obliquely after passing through a lapper, which allows, with a mixture by weight of 75% glass and 25% thermoplastic material, to obtain a reinforcement with transverse components (weft), the final weight being 760 g / m ² . Such a reinforcement product can be used in the manufacture of skis. This avoids the presence of binding threads by sewing knitting, which are present in the current reinforcements of roving ply and non-directional glass veil. These sewing knitting yarns constitute surface irregularities which remain apparent after manufacture of the ski, and detract from the appearance of the product. The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field of claims below.

Claims

1 - Reinforcement product comprising a coherent connecting veil (9) consisting of a homogeneous mixture of sections of oriented glass filaments (3) and sections of oriented filaments of thermoplastic material (4). 2 - Reinforcement product according to claim 1, characterized in that the connecting web (9) has a weight of about 15 g / m ² to about 100 g / m ² , advantageously about 20 g / m ² . 3 - Reinforcement product according to one of claims 1 or 2, characterized in that, in the mixture, the sections of glass filaments (3) are present in a proportion of between 50 and 80% by weight approximately, and the sections filaments of thermoplastic material (4) are present in a proportion of between 50 and 20% by weight approximately. 4 - Reinforcement product according to any one of claims 1 to 3, characterized in that, in the mixture, the sections of glass filaments (3) have a diameter of between 10 and 24 μm approximately, and the sections of filaments of thermoplastic material (4) have a diameter of between 10 and 30 μm approximately. 5 - Reinforcement product according to any one of claims 1 to 4, characterized in that, in the mixture, the sections of filaments (3, 4) have a length of between 30 mm and 60 mm approximately. 6 - Reinforcement product according to any one of claims 1 to 5, characterized in that the thermoplastic material is chosen from the group comprising polyester, polyolefins, polyamides, polyacrylonitriles, polyethylene terephthalate, polybutylene terephthalate. 7 - Reinforcement product according to any one of claims 1 to 6, characterized in that, in the connecting web (9), the sections of filaments partially adhere to each other by the thermoplastic material. 8 - Reinforcement product according to any one of claims 1 to 7, characterized in that the connecting web (9) is continuous and monolayer. 9 - Reinforcement product according to any one of claims 1 to 7, characterized in that the connecting veil (12) is coated in a zigzag, and the adjacent sections (12a, 12b) of connecting veil adhere to each other by the thermoplastic material. 10 - Reinforcement product according to any one of claims 1 to 9, characterized in that the connecting web (9, 12) adheres by the thermoplastic material to a support (15) based on reinforcing fibers such as fibers glass, carbon fibers, aramid fibers. 1 1 - Reinforcement product according to claim 10, characterized in that the support (15) is a sheet of parallel continuous son. 12 - Reinforcement product according to claim 1 1, characterized in that the connecting web (9, 12) adheres to one face of the ply (15) of continuous son. 13 - Reinforcement product according to claim 11, characterized in that the successive continuous son (15a, 15b) of the sheet (15) adhere alternately on either side of the connecting web (9, 12). 14 - Reinforcement product according to claim 10, characterized in that the support (15) is a fiber grid oriented in at least two directions. 15 - Reinforcement product according to any one of claims 1 to 14, characterized in that the mixture also contains sections of filaments made of another material such as linen, hemp, sisal, jute, wool. 16 - Reinforcement product according to any one of claims

1 to 14, characterized in that the mixture also contains sections of filaments obtained from crimped single strands (20) of thermoplastic material whose melting temperature is higher than that of the thermoplastic material of the sections of filaments, constituting a elastic assembly. 17 - Reinforcement product according to any one of claims

1 to 16, characterized in that it further comprises at least one non-woven veil (19) of glass, of polyester, adhering to the coherent connecting veil (9, 12). 18 - Reinforcement product according to any one of claims 1 to 9, characterized in that it comprises a stack of layers of continuous son (15a - 15d) made of glass, carbon or aramids, having a bonding web ( 9a - 9c) inserted between each pair of successive layers and adhering to one and the other of said successive layers (15a - 15d). 19 - Reinforcement product according to any one of claims 1 to 9, characterized in that several layers of connecting veil are needled by water jets or optionally adhere to a support (15) based on reinforcing fibers such as glass fibers, carbon fibers, aramid fibers. 20 - Reinforcement product according to any one of claims 1 to 19, characterized in that the homogeneous mixture contains sections of oriented glass filaments (3), sections of oriented polyester filaments (4a), and sections of oriented filaments of polypropylene or polyethylene (4b). 21 - Reinforcement product according to claim 20, characterized in that the connecting web (9) adheres to reinforcing fibers (15) by the only sections of oriented filaments of polypropylene or polyethylene (4b). 22 - Method for producing a coherent veil reinforcement product (9, 12) consisting of a mixture of sections of oriented filaments containing sections of glass filaments (3), comprising the steps: a) preparing a homogeneous mixture of sections of glass filaments (3) and sections of filaments of thermoplastic material (4), of a length suitable for a carding operation, the sections of glass filaments (3) being homogeneously mixed with sections of filaments of thermoplastic material (4), b) treating this mixture of sections of filaments in a card (8) to produce a coherent connecting web (9) of sections of oriented filaments. 23 - A production method according to claim 22, characterized in that: c) at the outlet of the card (8), the connecting web (9) passes through a lapper (1 1) which folds it in a zigzag. 24 - Production method according to one of claims 22 or 23, characterized in that it comprises the step according to which: d) the connecting web (9, 12) is applied to a support (15) based on fibers. 25 - production method according to any one of claims

22 to 24, characterized in that it comprises a subsequent step e) of membership during which:

the components of the reinforcing product are heated to a temperature sufficient to give the thermoplastic adhesive properties, the components are pressed against each other,

- The assembly is cooled, and the pressure is released to release the reinforcement product.