FR2949125A1 - Fabricating glass fiber reinforced composite that is useful to fabricate non-woven fabric, by coating natural wire material with polymer material to form reinforced composite, cutting composite to determined length and laminating composite - Google Patents

Abstract

The process comprises coating a natural wire material with a polymer material to form a reinforced composite, cutting the composite to a determined length, and laminating the composite. The natural material is made of linen. Independent claims are included for: a non-woven fabric; and #a process of fabricating a non-woven fabric.

Description

Composite reinforcement based on natural fibers The invention relates to a composite reinforcement. More particularly, the invention relates to a composite reinforcement based on natural fibers.

Currently, glass fibers are used, for example, as reinforcement of polymeric materials, allowing optimum resistance according to their use. In particular, they make it possible to considerably reduce the weight of a structure relative to steel. To overcome ecological problems, today we replace these glass fibers from the chemical industry with natural fibers such as linen, hemp, sisal, etc. The use of these fibers still allows a weight saving compared to the use of fiberglass. The current problem is that the use of these fibers does not allow reproducibility of the characteristics during their use, in particular due to their nonuniform lengths and to the naturalness of the fiber whose mechanical characteristics are related to the culture conditions. In addition, these fibers require complicated treatments, mainly chemical, to promote their adhesions with the polymer materials used later.

The object of the invention is to provide an ecological composite reinforcement having easily reproducible mechanical characteristics. The invention also aims to provide a mechanical treatment of adhesion with the polymer materials used later. According to a first aspect of the invention, it is a method of manufacturing a composite reinforcement comprising at least the following steps: coating a yarn of natural material with a polymeric material so as to form a composite reinforcement; The cut of the reinforcement to a determined length.

The manufacturing method may also include a heating step of a natural material wire. The polymeric material may in particular be a thermoplastic material or a thermosetting material.

The fact of starting from a wire facilitates on the one hand the coating, delicate on a single fiber, and on the other hand makes it easy to obtain a good reproducibility of the mechanical characteristics not only because the diameter of the wire, in particular by through its title, is known but also because it controls the length of the reinforcement. The natural material yarn used in the process according to the invention corresponds to all products from the spinning industries, constituting an assembly of fibers having undergone a twist capable of ensuring cohesion between the fibers. It will thus be possible to use for the invention a yarn, strictly speaking, a wick, a ribbon, a retorde, a double twist, a cable, etc. Heating the wire makes it possible to bring the latter to a temperature close to the temperature of the coating materials at the extruder outlet, thus promoting the cohesion of the coating material with the wire.

The heating of the wire makes it possible in particular to reduce the hygrometry rate in the latter and thus to avoid a release of steam in contact with the hot material. This also prevents the cooling of the material in contact with the wire. Coating is defined as coating a textile with a product that protects it, modifies its appearance, etc. The sheathing of the wire is then obtained by the polymer material. In this case, the length of the cut is determined according to the diameter of the wire and its end use. The form factor is defined as the ratio of the length to the diameter of the wire. The form factor ensures a transfer of charges between the material and the wire. This ratio is based on the end use of the product. In the case of the use of the composite reinforcement reinforcement, it is recommended to have a ratio of at least 200. For example, the fiberglass used as reinforcement fiber has a factor of shape less than 100 in short fiber injection and a form factor ranging from 100 to 1000 injection long fibers. According to a particular embodiment, the manufacturing method further comprises a step of rolling the composite reinforcement.

The mechanical rolling treatment applied to the coated wire makes it possible, in particular, to increase the impregnation of the polymer material at least at the surface and at best in the core of the wire, by filling the inter-fiber porosities. A mechanical connection is then created between each fiber composing the wire, reinforcing in particular the mechanical characteristics of the latter. This changes from a surface-sheathed structure with fiber mobility internally to an impregnated structure. The latter makes it possible to obtain torsional fiber consolidation by the impregnating material and reinforcement of the wire / material connection by means of the porosities. Once the wire is cut to the desired length, it is no longer a sheathed wire, but a composite fiber or fiber-type composite reinforcement. The manufacturing process may include a cooling step that may be natural or forced. Preferably, the natural material is flax but one could equally consider using other natural fibers such as hemp, cotton, bamboo, sisal, etc. According to a particular embodiment, the composite reinforcement comprises at least one yarn of natural material comprising at least 50%, by weight, of at least one element among hemp, cotton, bamboo, sisal, etc. In another embodiment, the composite reinforcement may also include other son or filaments from chemical dies. In a preferred application, the composite reinforcement obtained by the process according to one aspect of the invention is used as a replacement for glass fiber to reinforce composite materials. The invention also relates to a nonwoven comprising in particular a plurality of composite reinforcements as obtained by the method described above and in particular a thermoplastic impregnation. Advantageously, the nonwoven comprises at least one thermoplastic substrate, compatible with the impregnating thermoplastic

wherein is embedded or agglomerated a plurality of composite reinforcements. The invention also relates to the method for manufacturing a nonwoven based on composite reinforcements, comprising at least the following steps: random distribution of composite reinforcements in a substantially homogeneous sheet; The heating of the tablecloth; Pressing the tablecloth; The cooling of the tablecloth. The distribution into a random layer of a product is well known to those skilled in the art who wishes to make a nonwoven. Composite reinforcements are placed in a hopper, for example a vibrating hopper, which makes it possible to bring the material into a continuous flow on a conveyor belt. Composite reinforcements can also be cut at the top of the conveyor belt. The flow rate of the hopper, or cut, and the speed of the conveyor belt are functions of the desired weight of the final product. By substantially homogeneous it will be understood that the distribution of the reinforcement mass per m2 does not vary by more than 30%. According to a preferred embodiment, the method of manufacturing a nonwoven based composite reinforcements comprises at least the following steps: The distribution of a substrate; Random distribution of composite reinforcements in a substantially homogeneous layer on the substrate; The adhesion of the substrate and the reinforcement by a cohesive means. If the substrate is a thermoplastic substrate, it may be possible to consider heating the latter and / or heating the composite reinforcements in order to obtain good cohesion of the assembly during the adhesion step, for example by pressing.

It is also possible to envisage another substrate and / or other means of cohesion of the assembly, for example by gluing. The adhesion of the substrate to the reinforcement is for example made by pressing, either after a heating operation or after a bonding operation, depending on the substrate used. Depending on the selected operating mode, it is possible to cut the web either before pressing or after cooling. The pressing of the web is carried out either by means of a press when the web is cut as and when it is manufactured, or by means of a calender and / or a press when the tablecloth is manufactured continuously. In a preferred application, the nonwoven is used as a TRE plate (Thermoplastic Reinforced Stampable).

We will now describe several embodiments for the manufacture of the composite reinforcement and the corresponding nonwoven. The manufacture of the composite reinforcement starts from a thread already formed from the textile industry. This yarn is preferably composed of 100% flax but other blends could be envisaged, with other natural fibers or with synthetic fibers, depending on the desired characteristics of the final product. The wire is in the form of a coil which is heated, for example by means of an infrared heater, to prepare the wire to receive the impregnating material. It is also possible to heat the wire directly, for example by passing through an infrared heating tunnel, the length of the tunnel depending in particular on the speed of travel. In the case of an impregnation with a thermoplastic material, the wire is brought to a temperature close to that of the thermoplastic at the extruder outlet.

The wire thus heated, is proceeded to the coating of the latter. In our example, we use an extruder at the head of a square, to control the thickness of the coating. This gives a uniform sheathing of our wire, forming a composite reinforcement.

The sheathed wire is rolled to impregnate the wire to the heart. This operation also reduces the thickness of the composite reinforcement. The rolling is carried out by means of two rollers whose pressure is determined as a function of the desired finished product. Other rolling operations may be considered along the production line. It is recommended to maintain a certain viscosity between the coating step and the rolling step to obtain a plastic deformation and not an elastic deformation. In order to maintain this viscosity, it is possible to continue heating the composite reinforcement, in particular by heating the rollers intended to transport the reinforcement or the rolling rolls. The coating step, and possibly the rolling step, being performed, it may be necessary to force the cooling of the reinforcement. This operation can for example be carried out by passing in water tanks, by fresh air pulsed, etc. Once cooled, it is then possible to wind the composite reinforcement to store before cutting or transport to its place of cut. The composite reinforcement is cut to a desired length depending on its end use. It is possible to treat several threads simultaneously, the important thing being to prevent them from touching and adhering to each other.

Once the composite reinforcement obtained in its final version, it is possible to use it in the manufacture of nonwoven fabric. The manufacturing process of the nonwoven begins with the composite reinforcement once cut. The latter is distributed on a conveyor belt, forming a web whose weight per m2 is determined beforehand according to the end use of the product.

This sheet is preheated before it passes through a calender. It will be possible to provide various modes of heating the web such as for example by infrared. The heating is intended to promote the plastic deformation of the coating product and thus allow the adhesion by thermo-bonding composite reinforcements between them when the sheet passes between the rolls of the calender. The rollers of the calender are also heated, it is not always necessary to preheat the web, especially when the latter is relatively thin and / or has a small coating thickness. Once the tablecloth has been pressed, a cooling operation can be carried out, for example by cold calendering, which also makes it possible to consolidate the thickness of the product. Once the nonwoven cools, it can be cut to the desired dimensions depending on its end use, or wound for subsequent cutting. According to an additional embodiment, it is possible to produce a sandwich structure in which one or more other elements are added to the nonwoven obtained beforehand. These elements can be incorporated on the hot or cold part of the line, in solid or liquid form. They can be found in the form of film, sheet, etc. For example, a sandwich structure may be made on the basis of a thermoplastic film on which the nonwoven is positioned.

The whole is hot pressed to ensure a good connection of the whole. It will also be possible for example to make a sandwich structure on the basis of a layer of felt on which points are positioned or a layer of adhesive before positioning the nonwoven.

The set is then pressed to ensure a good connection of the whole.

In a first example, it will be possible to obtain a nonwoven of 70 g / m 2 of fiber, without the impregnation material, of a 40 Nm yarn composed of 100% lin, the cutting length of the composite reinforcement is order of 35 mm.

According to another example, it will be possible to obtain a nonwoven of 160 g / m 2 from a 5 Nm yarn composed of 55% of linen and 45% of cotton, whose cutting length is of the order of 120. mm. These nonwovens can be used in a wide variety of applications, in areas as diverse as reinforcement structures or garments, both raw and assembled with other materials, whether in the form of flat products or in shape. They can for example be found in the form of panels for the interior and / or exterior arrangement or panels used in thermoforming or thermo-compression.

The advantages of the composite reinforcement result in particular from its low weight comparable to natural fibers but having better mechanical characteristics than the latter. The nonwoven construction with these composite reinforcements makes it possible to obtain structures of reduced thickness, less than or equal to the millimeter that would otherwise be impossible to obtain with natural fibers with equivalent mechanical characteristics. 20

Claims (9)

REVENDICATIONS1. A method of manufacturing a composite reinforcement comprising at least the following steps: coating a yarn of natural material with a polymeric material so as to form a composite reinforcement; The cut of the reinforcement to a determined length. 2. A method of manufacturing a composite reinforcement according to claim 1, characterized in that it further comprises a step of rolling the composite reinforcement. 3. A method of manufacturing a composite reinforcement according to one of claims 1 or 2, characterized in that the natural material is linen. 4. Use of a composite reinforcement obtained by the process according to any one of claims 1 to 3 to replace the glass fiber for reinforcing composite materials. 5. A nonwoven comprising in particular a plurality of composite reinforcements obtained by the method according to any one of claims 1 to 3. 25 6. Nonwoven according to claim 5, characterized in that it comprises in particular at least one thermoplastic substrate in which is embedded or agglomerated said plurality of composite reinforcements. 7. A method of manufacturing a nonwoven according to claim 5, comprising at least the following steps: random distribution of composite reinforcements in a substantially homogeneous layer; The heating of the tablecloth; Pressing the tablecloth; The cooling of the web. 2949125 io 8. A method of manufacturing a nonwoven according to claim 6, comprising at least the following steps: - The distribution of a substrate; Random distribution of composite reinforcements into a substantially homogeneous web on the substrate; The adhesion of the substrate and the reinforcement by a cohesive means. 9. Use of a nonwoven according to any one of claims 5 or 6, or obtained by the method according to one of claims 7 or 8 as a plate TRE (Thermoplastic Reinforced Stampable).