FR2877955A1 - AERIAL REINFORCEMENT PRODUCT AND METHOD FOR PRODUCING THE SAME - Google Patents

Abstract

The reinforcement product, used for the production of composite materials, is a web containing first sections of filaments (1a) made of a first type of synthetic material, oriented, having received prior to their forming in the form of a web a treatment giving them a permanent crimp, second sections of filaments (2a) made of a second type of synthetic material of thermoplastic nature, as well as sections of filaments of reinforcing fibers (20a). The second sections of filaments (2a) made of a second type of synthetic material with a thermoplastic character have a lower melting point than that of the first sections of filaments (1a) made of a first type of synthetic material. The sections of filaments partially adhere to each other by the second sections of filaments (2a) made of a second type of synthetic material of thermoplastic nature.

Description

The present invention relates to an improvement made to the reinforcement

  textiles used for the production of composite materials, that is, articles made from resin (polyester or other) with a textile web of

enhancement.

  To date, depending on the desired applications and characteristics, the reinforcing structures used in the field of composites are, for example, fabrics, textile grids, nonwovens, or combinations of such elements.

  A necessary characteristic of these textile frames, when it is desired to make elements such as vehicle bodies, pleasure boats, tanks, is to give composite materials a high rigidity thanks in particular to their high thickness.

  Thus, the French patent FR 2,646,442 describes a textile reinforcement constituted by at least two textile reinforcement layers themselves, arranged on either side of a central layer giving the thickness to said material, and characterized by the fact that that said central layer is a web made by carding synthetic fibers, for example polyester, of high unitary title, and which have received prior to their tabletting a treatment imparting to them a corrugation or permanent crimp, the different layers being linked together by sewing / knitting.

  However, one of the drawbacks of the product obtained lies in the fact that the bonding seams of the various layers between them limit the production of structures of complex shape obtained by molding, for example according to the techniques known as "injection molding with injection molding. "or" vacuum molding ". Indeed, the connection seams of the different layers between them introduce irregularities in the deformation capacities, limit the deformation capacities of the textile reinforcement before molding, and can lead to defects in surface appearance of the composite material after molding .

  To remedy these risks of surface appearance defects, patent EP 0 659 922 proposes an improvement consisting in covering at least one of the textile reinforcing layers with a fibrous web based on chemical fibers, and in ensuring the cohesion of the different layers by needling.

  The document EP 0 694 643 proposes to improve the surface condition of the composite material comprising a reinforcement such as that described in patent FR 2,646,442, and furthermore proposes to adapt certain technical characteristics such as the dimensional stability of the product. or the possibility of deformation, depending on the applications into which such a material enters. To do this, to the textile reinforcement which is the subject of patent FR 2,646,442, is added at least against one of the outer faces of the complex, a veil of synthetic fiber, the connection of the veil being made either by bonding to the outside of the textile reinforcement, either through the seams linking the different layers of the textile reinforcement between them.

  The multilayer nature of the above reinforcements, as well as the irregularities of their deformation capacity before molding, are substantial disadvantages. Indeed, the fact that the frame has several layers requires to provide suitable means to ensure the cohesion between them of different layers. And whatever these connecting means, they always lead to limit and / or disturb the deformation capacity of the armature, thus making it poorly suited to use in injection molding techniques or by molding under empty, since leading to defects of the composite material after molding.

  In addition, the intermediate layer of the above reinforcements is free of reinforcing fibers, so that the resin is not reinforced in this intermediate layer, and is a zone of lower mechanical strength and may contain bubbles, to crack.

  The problem proposed by the present invention is to obtain a textile reinforcement having a sufficient thickness and giving the composite material satisfactory properties of rigidity after molding, having a capacity of deformation by regular flexion, having great flexibility to be deformed and placed effectively in a mold before injection, and having a satisfactory coherence for necessary manipulations before molding.

  The invention also aims to design such a frame that can be manufactured economically by industrial processes.

  To achieve these and other aims, the invention proposes an aerated reinforcing product that can be used for producing composite materials, comprising a ply based on first sections of filaments in a first type of synthetic material, oriented, having previously received to their tabletting a treatment imparting a permanent crimp; according to the invention: - said sheet further comprises at least second sections of filaments in a second type of thermoplastic material oriented oriented, having a melting temperature lower than that of the first sections of filaments in a first type of material synthetic, - said sheet further comprises sections of filaments of reinforcing fibers, - the sections of filaments partially adhere to each other by the second sections of filaments in a second type of synthetic material of thermoplastic nature.

  Thus, the reinforcing product consists substantially homogeneously in a single layer, and has an internal cohesion that does not require additional processes, needling, gluing with an added material, or sewing / knitting.

  At least some of the first sections of permanently crimped filaments within the reinforcing product may advantageously have a state of partial compression giving them elastic deformation or prestressing.

  The first sections of permanently crimped filaments can advantageously have a linear density of 1 to 5 dTex.

  The material of the second sections of filaments into a second type of synthetic material of thermoplastic nature can be chosen from the group comprising polyester, polyolefins, polyamides, polyacrylonitriles, polyethylene, polyethylene terephthalate and polybutylene terephthalate.

  According to an advantageous embodiment, the sections of filaments of reinforcing fibers may comprise sections of glass filaments.

  Alternatively or in addition, the sections of reinforcing fiber filaments may comprise sections of natural filaments such as linen, hemp, sisal, jute, or wool.

  It may be advantageous to introduce in the mixture sections of mixed fiber filaments which serve as both sections of reinforcing fiber filaments and second sections of filaments of a second type of synthetic material of thermoplastic nature. The stitches of mixed fiber filaments are derived from composite comminuted yarns composed of glass filaments and filaments of an organic thermoplastic material having a lower melting temperature than the first sections of filaments of the first type of synthetic material. This reduces the number of fibers that must be assembled in the mixture at the base of the product, and this simplifies the development.

  In an advantageous embodiment, at least one external reinforcing layer may be affixed to at least one of the faces of the reinforcing product.

  For example, the outer reinforcing layer may be a web of continuous and parallel son.

  It is also conceivable that the outer reinforcing layer is a fiber grid oriented in at least two directions.

  According to another aspect, the invention proposes a process for producing a reinforcing product as defined above; the process comprises the following steps: a) preparing a homogeneous mixture of first sections of filaments in a first type of synthetic material, second sections of filaments in a second type of synthetic material of thermoplastic nature and with a lower melting temperature than first sections of filaments of a first type of synthetic material, and sections of filaments of reinforcing fibers, b) treating this mixture of sections of filaments in a card to produce an orientation of the sections of filaments and thus forming an oriented sheet, c) heating the oriented web obtained to make the second filament sections adhesive to a second type of thermoplastic material of lower melting temperature, d) cooling the web.

  Preferably, the process may comprise an intermediate step of compressing the constituents by reducing the thickness of the sheet and maintaining this reduction in thickness, during or following the heating step c), and this up to in step d) of cooling. Thus, by this partial compression, the approximation of the sections of filaments against each other, and thus the adhesion of the sections of filaments to each other.

  It is possible, between steps b) of carding and c) of heating, to provide an intermediate step during which at least one external reinforcing layer is applied to at least one of the faces of the sheet.

  Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments, made with reference to the appended figures, in which: FIG. 1 is a schematic perspective view illustrating a product structure of reinforcement according to a first embodiment of the present invention; - Figure 2 schematically illustrates an embodiment of manufacturing plant of the reinforcing product according to Figure 1; FIG. 3 is a sectional side view partially illustrating the reinforcing product manufacturing facility according to the embodiment of FIG. 2; - Figure 4 is a sectional side view partially illustrating the manufacturing facility during manufacture of the reinforcing product according to Figure 5; and FIG. 5 is a schematic perspective view illustrating a reinforcement product structure according to a second embodiment of the present invention.

  Referring first to Figure 2, which schematically illustrates a manufacturing facility of a reinforcing product according to an embodiment of the present invention.

  This installation firstly comprises a reserve 1 of first sections of filaments la in a first type of synthetic material, as well as a reserve 2 of second sections of filaments 2a in a second type of synthetic material having a thermoplastic nature having a temperature of less melting than that of the first sections of filaments 1a first type of synthetic material. The installation further comprises a reserve 20 of sections of reinforcing fiber filaments 20a.

  The first sections of filaments the first type of synthetic material received a prior treatment giving them a permanent crimp. The linear density of these first filament sections 1a may advantageously be between 1 and 5 dTex.

  The three reserves 1, 2 and 20 of sections of filaments then suitably feed a card 3.

  A mechanical card 3 such as those conventionally used in the textile industry can be used, comprising a rotating cylinder equipped with teeth or needles that rotate in front of workers to drive the filament sections while painting them, thereby producing an output. continuous ply 4 in which the sections of filaments 1a, 2a and 20a are preferably oriented in the longitudinal direction 11 of the web 4.

  Alternatively, a pneumatic card can be used, generating a flow of air which directs the sections of filaments by painting them.

  In the embodiment of FIG. 2, the ply 4 is then heated by a heating device 6. The heating temperature is sufficient to give adhesive properties to the second filament sections 2a in a second type of synthetic material of thermoplastic nature contained in FIG. the ply 4 of fibers. The temperature is advantageously chosen only slightly lower than the melting temperature of the second filament sections 2a in a second type of synthetic material of thermoplastic nature, whose melting temperature is lower than that of the first sections of filaments the first type of synthetic material. For example, for polyethylene, a temperature of about 120 C-140 C will be chosen.

  At the outlet of the heating device 6, a coherent sheet 5 is collected, the internal cohesion of which is ensured by the adhesion of the second sections of filaments 2a to a second type of synthetic material of a thermoplastic nature.

  The constituents of the coherent web can then be allowed to cool to ambient air.

  Preferably, downstream of the heating device 6, there is provided a cooling device 7 for cooling the constituents and immobilizing the second sections of filaments 2a in a second type of synthetic material of a thermoplastic nature, thereby freezing the dimensional characteristics of finished textile reinforcement 8.

  The melting temperatures of the first sections of filaments 1a in a first type of synthetic material and sections of filaments of reinforcing fibers 20a being higher than that of the second sections of filaments 2a in a second type of synthetic material of thermoplastic nature, the first sections of filaments la in a first type of synthetic material and the sections of filaments of reinforcing fibers 20a do not undergo any transformation during the heating of the sheet 4 at a temperature slightly lower than the melting temperature of the second filament sections 2a in a second type of thermoplastic synthetic material.

  Thus, the first sections of filaments la in a first type of synthetic material retain all their properties (shape, elasticity, ...) and give the coherent web 5 an airy and elastic structure, resulting from their permanent crimp. The sections of reinforcing fiber filaments also retain all their properties (shape, strength, etc.) and give the coherent web a certain endurance.

  This elastic structure is advantageous in a molding process where large deformation capacities are required of the reinforcing product. In addition, the aerated structure of the textile reinforcement allows an easier and more homogeneous distribution of an injected resin for example during the molding of the finished textile reinforcement 8 to obtain a reinforced composite.

  By this process, a textile reinforcement having a sufficient thickness and a suitable distribution of reinforcing fibers is also obtained to give the composite material satisfactory rigidity properties after molding.

  The textile reinforcement has a capacity of deformation by regular bending, a great flexibility to be deformed and placed efficiently in a mold before injection, and has a satisfactory coherence for the necessary manipulations before molding.

  Reference can be made to FIG. 1, which illustrates in perspective on a larger scale the structure of the finished textile reinforcement 8, formed of sections of filaments 1a, 2a and 20a that are carded, preferably oriented in the longitudinal direction 11.

  In the embodiment illustrated in FIG. 2, the material of the second sections of filaments 2a in a second type of synthetic material of thermoplastic nature is chosen from the group comprising polyester, polyolefins, polyamides, polyacrylonitriles and polyethylene. polyethylene terephthalate, or polybutylene terephthalate.

  In this same embodiment illustrated in Figure 2, it can further be provided that the sections of reinforcing fiber filaments 20a comprise sections of glass filaments.

  It may be advantageous to provide that the sections of reinforcing fiber filaments 20a comprise sections of natural filaments such as linen, hemp, sisal, jute, or wool, in addition to or instead of the sections of glass filaments.

  In the embodiment illustrated in FIG. 3, compression means 9a and 9b located after the heating device 6 and located just before the cooling device 7 are provided. Thus, the sheet 4 coming from the card 3 is heated, then is subjected by pressing means 9a and 9b a partial compression of the constituents by reducing the thickness of the sheet, followed by cooling. The pressing of the constituents once heated within the ply 4 allows better adhesion of the filament sections la, 2a and 20a to each other, while maintaining an airy or porous character.

  The sections of filaments 1a, 2a and 20a may thus have a partial compression state resulting from the reduction in thickness of the sheet 4 by pressing means 9a and 9b. The partial compression of the permanently crimped filament sections confers them elastic deformation or elastic prestress whose existence can be observed in the finished reinforcement product.

  FIG. 4 schematically illustrates a variant of the embodiment of FIG. 3, in which an outer reinforcing layer 10 is applied on the upper face of the ply 4, which is then adhered to the ply 4 by heating and cooling. compression.

  In the embodiment of FIG. 4, the outer reinforcing layer 10 may advantageously be a sheet of continuous and parallel threads.

  Alternatively, the outer reinforcing layer 10 may be a fiber grid oriented in at least two directions.

  FIG. 5, which illustrates in perspective on a larger scale the structure of the finished textile reinforcement 8, formed of sections of filaments 1a, 2a and 20a that are carded, preferably oriented in the longitudinal direction 11, and comprising on its upper face the outer reinforcing layer 10.

  In the embodiments illustrated in FIGS. 3 and 4, the pressing means 9a and 9b provide a compression of the constituents by reducing the thickness of the sheet 4 and maintaining this reduction in thickness up to the cooling device 7. In the more particular context of the embodiment illustrated in FIG. 4, the pressing means 9a and 9b also ensure the plating of the outer reinforcing layer 10 against the ply 4. They may also be heated to ensure the heating of the together to a temperature ensuring sufficient softening and adhesion of the second sections of filaments 2a to a second type of synthetic material of thermoplastic nature contained in the composite fibers constituting the sheet 4. Alternatively, the heating may be provided by hot sources such as infrared radiation sources upstream of the rollers, and the rollers 9a and 9b compress the constituents without the heat up.

  At the outlet of the cooling device 7, by the effect of the sufficient softening of the second filament sections 2a into a second type of synthetic material of thermoplastic nature, then by the cooling effect which freezes them, the external reinforcing layer 10 adheres to the coherent web 5, and the filament sections la, 2a and 20a also adhere to each other.

  In the products and processes described above, it may be advantageous to introduce into the mixture sections of mixed fiber filaments which serve as both sections of reinforcing fiber filaments 20a and second sections of filaments 2a. a second type of thermoplastic synthetic material. The mixed fiber sections come from co-mixed mixed yarns composed of glass filaments and filaments of another organic thermoplastic material having a lower melting temperature than the first sections of filaments 1a in a first type of synthetic material.

  In this case, the card 3 is powered by only two reserves of wire sections.

  The reinforcement product thus obtained is sufficiently homogeneous and coherent to allow control of its handling and its deformations when used in injection molding techniques or by vacuum molding, and to avoid defects in the composite material. after molding.

  The present invention is not limited to the embodiments which have been explicitly described, but includes the various variants and generalizations thereof within the scope of the claims below.

Claims (10)

  1 aerated reinforcement product usable for the production of composite materials, comprising a web (4) based on first sections of filaments (la) in a first type of synthetic material, oriented, having received prior to their tableting a treatment communicating them a permanent crimp, characterized in that: - said ply further comprises at least second sections of filaments (2a) in a second type of thermoplastic material, oriented, having a melting temperature lower than that of first sections of filaments (1a) of a first type of synthetic material, said sheet further comprises sections of reinforcing fiber filaments (20a), - the sections of filaments (1a, 2a, 20a) partially adhere to one another by the second sections of filaments (2a) into a second type of synthetic material of a thermoplastic nature.   2 reinforcement product according to claim 1, characterized in that at least some first sections of filaments (la) permanently crimped have a partial compression state conferring elastic deformation or prestressing.   Reinforcing product according to one of claims 1 or 2, characterized in that the material of the second sections of filaments (2a) into a second type of synthetic material of thermoplastic nature is chosen from the group comprising polyester, polyolefins, polyamides, polyacrylonitriles, polyethylene, polyethylene terephthalate, polybutylene terephthalate.   Reinforcing product according to any one of Claims 1 to 3, characterized in that the sections of filaments of reinforcing fibers (20a) comprise sections of glass filaments.     Reinforcement product according to any one of claims 1 to 4, characterized in that the sections of reinforcing fiber filaments (20a) comprise sections of natural filaments such as linen, hemp, sisal, jute, wool.   6 reinforcement product according to any one of claims 1 to 5, characterized in that it comprises sections of mixed fiber filaments from mixed yarns mixed compound glass filaments and filaments of an organic thermoplastic material having a lower melting temperature than the first sections of filaments into a first type of thermoplastic material.   7 reinforcement product according to any one of claims 1 to 6, characterized in that on at least one of its faces is affixed at least one outer reinforcing layer (10).   8 reinforcement product according to any one of claims 1 to 7, characterized in that the outer reinforcing layer (10) is a web of continuous son and parallel.   9 reinforcement product according to any one of claims 1 to 8, characterized in that the outer reinforcing layer (10) is a fiber grid oriented in at least two directions.     Process for the production of a reinforcement product according to any one of Claims 1 to 9, characterized in that it comprises the following steps: a) a homogeneous mixture of first sections of filaments (la) is prepared in a first type of synthetic material, second sections of filaments (2a) into a second type of thermoplastic material with a lower melting temperature than the first sections of filaments (1a) into a first type of synthetic material, and sections of reinforcing fiber filaments (20a), b) this mixture of filament sections is treated in a card (3) to produce an orientation of the filament sections and thus forming an oriented web (4), c) the web is heated up (4) Orientation obtained in order to make adhesive the second sections of filaments (2a) in a second type of thermoplastic material with a lower melting temperature, d) cooling the n call (4).   11 Process according to claim 10, characterized in that it comprises, during or following the heating step c), a compression of the constituents by reduction of the thickness of the sheet (4) and a maintenance of this reduction in thickness until step d) of cooling.   12 Method according to one of claims 10 or 11, characterized in that, between the steps b) carding and c) heating, is integrated a step of applying at least one outer layer of reinforcement (10) on at least one of the faces of the web (4).