EP1855859A1

EP1855859A1 - Concentrated reinforcing bars and method for making same

Info

Publication number: EP1855859A1
Application number: EP06709433A
Authority: EP
Inventors: Philippe Pardo; Christophe Ducret; Guy Zanella
Original assignee: Saint Gobain Vetrotex France SA
Current assignee: Saint Gobain Adfors SAS
Priority date: 2005-03-09
Filing date: 2006-01-24
Publication date: 2007-11-21
Also published as: FR2882958A1; FR2882958B1; RU2404052C2; US20080171200A1; BRPI0607814A2; CN101137476B; JP5153612B2; KR20070108235A; MX2007010777A; RU2007137114A; JP2008532799A; CN101137476A; WO2006095101A1

Abstract

The invention concerns a method for making concentrated reinforcing bars wherein at least one bundle of wires having more than 70 wt. % of reinforcing material and at least 0.1 % of moisture, is heated and shaped before being cut into bars. The invention also concerns a device for implementing the method and the resulting products.

Description

CONCENTRATED REINFORCING STICKS AND THEIR MANUFACTURE

The present invention relates to a method of manufacturing rods of concentrated reinforcements used in particular for manufacturing composite products by molding (in particular by injection, extrusion compression, comoulage, etc.) and also relates to the products obtained.

In the aforementioned molding processes (in particular by injection or extrusion-compression), mixtures of organic material, fibrous reinforcements (such as glass strands) and additive (s) are used (for example to color or bring particular functions). Mixing can be done directly in an extruder or in an injection molding machine from reinforcing threads, which may or may not already be coated with organic material, and which are generally already cut to facilitate dosing and mixing, the other possible components being if necessary added in the extruder or in the press.

The inventors have sought to develop a product based reinforcements that can be used with advantages in these molding processes, the desired benefits can be one and / or the other of the following advantages: cost savings, better preservation of reinforcements (for example the length of the reinforcement threads) for better mechanical properties, better dispersion during molding, ease of adaptation according to the desired products, easier implementation, etc.

In this research, the inventors have put forward the interest of developing products in the form of rods (or pellets or "pellets") concentrated in reinforcements, these products being able to bring various advantages as explained in particular subsequently, and have thus sought a method making it easy to manufacture these products, obtaining such concentrated products in a simple manner and performance from traditional reinforcements is not possible so far, the increase in the rate of reinforcement may in particular cause problems of lack of integrity of the products made or poor dispersion of these products in the molding dies.

The present invention therefore relates in the first place to a method for manufacturing concentrated rods in which at least one bundle of yarns having more than 70% by weight of reinforcement material (s) and at least 0.1% by weight of moisture, is heated and shaped before being cut into sticks.

The rods obtained comprise a reinforcing material essentially in the form of son or filaments (cut to the length of the stick) advantageously linked together by at least one organic material as explained later.

The present invention also relates to the reinforcing rods (or rod-shaped reinforcing threads) developed and obtained in particular by the above method. These rods have a level of material (s) of reinforcement greater than 65% and preferably greater than 70% (or even at least 80%) by weight. These reinforcements are bonded together or embedded in at least a first organic material, and if necessary are sheathed with at least a second material, generally at least one organic material, as explained later, the two organic materials may be identical or different .

The yarn bundle mentioned according to the invention comprises at least one reinforcing material (glass, carbon, aramid, etc., this material preferably being glass) in the form of at least a part of said yarns or in the form of filaments (generally obtained in a known manner by stretching this material under a spinneret, these filaments being then combined into threads) forming at least a portion of said threads, the amount of reinforcing material (s) within the bundle being more than 70% by weight in accordance with to the invention, and preferably ranging from 75 to 99% by weight, or even 80 to 95% by weight.

Preferably, at least part of the yarns used also comprise at least one thermoplastic organic material, this material being for example chosen from polyolefins, in particular polyethylene (PE), polypropylene (PP), polyesters, especially polyterephthalate. ethylene (PET), polybutylene terephthalate (PBT), elastomers, especially a polymer ethylene propylene (EPDM), or polyvinyl chloride (PVC), or polyamides, etc. Advantageously, this material is also in the beam in the form of son or filaments.

In particular, and preferably, at least a portion of the yarns used in the process according to the invention are composite (or co-mixed) yarns formed of reinforcing filaments (preferably glass) and filaments of at least one thermoplastic organic material, these filaments being advantageously intimately mixed, the intimate structure of these son facilitating the impregnation of the glass fibers by the thermoplastic material and, in the method according to the invention, to form, despite the high rate of reinforcements, a consolidated structure (that is to say having a cohesion and integrity that allows handling without damage) well impregnated and homogeneous. Advantageous composite yarns (such as those marketed under the trademark TWINTEX® by the company SAINT-GOBAIN VETROTEX FRANCE) may be obtained according to a direct process such as that described in patents EP 0 367 661, WO 98/01751 or EP 0 These yarns having an excellent co-blending index inducing an excellent distribution of the glass yarns in the thermoplastic material as explained in the patent application WO00 / 24566.

In a particularly preferred manner, the method according to the invention uses as son forming the beam only composite son. However, it is not excluded in particular to combine composite son and reinforcing son to further increase the concentration of reinforcement rods.

In combination with the high rate of reinforcement, favored in particular by the preferential use of composite yarns as mentioned above, the inventors have also demonstrated, as it appears in the definition of the invention, the advantage of using a bundle having a humidity (water content measured for example by evaporation in an oven) of at least 0.1%, preferably at least 0.5% and particularly preferably at least 3% by weight; the presence of a certain humidity, far from impeding the implementation and the properties of the products obtained, indeed makes it possible to handle the yarns well in the rod manufacturing process according to the invention, while at the same time making it possible to obtain products with mechanical properties at least as good or better than those obtained from previously dried, and while providing an economic advantage (it is possible in particular to directly use son obtained or collected under the die without expensive intermediate step of drying). Preferably, the humidity is also chosen less than 8%, advantageously less than 5% by weight, in particular to allow good consolidation of the son and the beam in the process according to the invention.

The son can be formed beforehand or extracted individually or in groups, at least one winding. According to a preferred embodiment of the invention, they are extracted from at least one winding, such as a roving or roving, and driven at a speed of at least 10 m / min, preferably several tens of m / min, in particular of the order of 40 to 100 m / min, in particular of the order of 50 m / min, using for example a traction device (which can be in particular a traction bench).

Advantageously, a step of regulating the tension of the threads may be provided (for example during their gathering in bundle (x) or before gathering them) and / or the threads may be rid of any static electricity, for example before the passage of the beam in the heating zone.

The son are gathered in the form of at least one beam as mentioned in the process according to the invention. It goes without saying that it is also possible to form several disjoint beams undergoing the same or different treatment in parallel, of which at least one undergoing the steps indicated in the process according to the invention to obtain the concentrated rods.

According to the invention, at least one beam is heated (generally by passing through at least one heating device, such as an infra-red radiation oven) at a temperature enabling it to be shaped and / or consolidated, and permitting, where appropriate, the impregnation of the reinforcement filaments or filaments with the organic material, in particular at a temperature reaching at least that of melting the thermoplastic material present within the bundle of threads and preferably greater than at least 20 ° C at said melting point of the thermoplastic material, this temperature nevertheless remaining below the decomposition temperature of said material and at the melting temperature of the reinforcing material.

Generally, the bundle of heated wires is maintained approximately in temperature until its conformation (or calibration), the conformation taking place advantageously by passing through one and preferably several calibration channels until the desired section is obtained. Within the process according to the invention and in order to allow a satisfactory yield of the production line, in combination in particular with the aforementioned drive speeds, the dies chosen are advantageously of simple profile (s) in the direction of the production line and descending section (s).

During and / or at the heating outlet, and beforehand and / or in conjunction with the abovementioned conformation, the beam may also optionally undergo a step promoting the impregnation of the reinforcing threads or filaments with the organic material present, by passing through a device such as one or more bars. Several of these devices can be used, a first being placed for example between two heating devices in the heating step according to the invention and the other being placed just before the shaping die or channels.

The aforementioned step or steps of conformation and impregnation favor the obtaining of a consolidated bundle (or impregnated or integrated, that is to say in which the son are linked together, this consolidated bundle being also designated by the term rod or wick according to the present invention, or strand, cable or rope).

According to a particularly preferred embodiment of the invention, following or during the conformation, the wire bundle is further subjected to a step of sheathing by passing through a die also fed with at least one organic material in the molten state, this material may be identical or different from the organic material forming the son. The cladding material may also be composite, formed of several materials, in particular at least one organic material and additive (s) (for example an additive improving resistance to ultraviolet radiation, a coupling agent to increase the performance mechanical, thermal or chemical stabilizer, dye or pigment, flame retardant, etc.) and / or filler (s) (talc, glass fibers, short or long, etc.). The cladding material may thus advantageously make it possible to confer additional properties on the rods obtained and the composites molded from these rods (anti-UV properties, improvement of the mechanical performances, etc.). Having already functionalized products also makes it possible during molding to use only inexpensive standard dilution materials, which simplifies and reduces the cost of molding. The cladding also prevents the formation of fibrils or fines (fibers detached from the stick) during cutting into sticks, these fibrils may cause problems conveying or congestion of the injection members during molding (and damage the systems of conveying or said injection members), and may adversely affect the mechanical properties of the products obtained. The sheathed sticks are also perfectly manipulable, dosable and transportable in the supply pipes because smoothed by the sheath, the sheath also acting as a protection, and do not lose their integrity until use to form composites by molding. The sheathing finally makes it possible to adjust the reinforcement ratio to the control by varying the quantity of cladding material delivered during the manufacture in line and thus makes it possible to obtain rods with various concentrations of reinforcements from a product. departure which can advantageously not vary.

Preferably, the cladding material comprises at least one thermoplastic organic material, for example a polyolefin (especially polyethylene or polypropylene) or polyvinyl chloride, or an elastomer, for example a modified polypropylene SEBS (styrene ethylene butadiene styrene), etc. If appropriate, this material is advantageously chosen to be identical or similar or chemically compatible with the organic material of the yarns (so that there is a good adhesion or even continuity between the two materials), this material possibly being loaded with additives as mentioned previously.

The cladding material introduced into the die can come for example from an extrusion device. The beam may also be coated with several identical or different materials supplying the die (or if necessary several dies in series or in parallel), this mode further widening the range of products obtained. When several beams are processed in parallel, the cladding material may vary from one beam to another as appropriate. The thickness of the sheath may be variable; as an example for a rod of the order of 3 mm thick, the sheath may be of the order of 0.1 mm or one tenth of the thickness of the stick, or more.

After conformation and possible sheathing, the resulting beam is generally cooled (by passage for example in a water tank or a cold die), if necessary dried (by blowing or suction), then cut or sectioned (for example using a milling cutter or granulator with rotating blades) in rods, of length generally between 1 and 40 mm, preferably between 5 and 30 mm, for example of the order of 12 mm.

As explained above, the method and the products according to the invention have the advantage of being adaptable without changing the starting materials. In addition, the method according to the invention is easy and quick to implement, and is economical.

The rods according to the invention have a high level of reinforcement as previously defined, while being intact and if necessary well impregnated, and may have a sheath as mentioned above. Advantageously, these rods (in particular sheathed) have a fibril level of less than 60, preferably 30, and particularly preferably 20 mg per kg of rods (this rate being measured by vibrating rods on a carpet and sucking the fibrils using a vacuum cleaner equipped with a filter). They are easy to handle and dose and disperse well in an organic matrix during molding despite the high rate of reinforcements. The rods according to the invention generally have a reinforcing son length of between 1 and 40 mm, preferably between 5 and 30 mm, for example of the order of 12 mm.

The present invention also relates to a device for implementing an advantageous embodiment of the aforementioned method. This device comprises one or more means for providing at least one bundle of wires, at least one means for heating said bundle, at least one shaping device, at least one sheathing die, fed by at least one molten material and having to receive simultaneously the bundle of wires and the molten material in contact with said bundle, and at least one cutting device, for cutting the sheathed bundle into rods.

The device may also comprise (in combination or in addition to the preceding means) one or more of the following means, in particular:

at least one roller guiding the wires;

one or more means for driving the wires;

one or more means for assembling the wires in the form of at least one bundle of parallel wires (for example of plate type (s) with eyelets and / or roller (s) and / or grooves (s));

one or more means for regulating the tension of the threads, for example upstream aforementioned gathering means;

- One or more means for maintaining the beam or the wick in temperature if necessary at least up to the die.

one or more additional impregnation devices, especially before the shaping device;

one or more means for positioning the beam; etc.

Most of these devices have already been mentioned previously.

In particular, the son may be from windings, these windings can be placed on a creel from which the son are unwound.

The heating means or means generally comprise one or more ovens, for example of the infrared type, preferably operating with lamps regulated in power as a function of the temperature of the beam, this kind of oven having the advantage of being at the energy efficient and easy to regulate.

As an impregnation device, it is possible, for example, to use a device comprising three members arranged in a triangle and between which the beam travels, the height of separation of the members being adapted to establish an appropriate pressure on the surface of the bundle, these members possibly being cylinders or bars.

The conformation devices strictly speaking may for example comprise a heating die, and / or rollers between which the wire bundle circulates, etc. As indicated above, the dies used advantageously have a simple profile with a section, for example varying gradually (for example decreasing) and then constant according to the locations, around an axis parallel to the direction of the production line.

The cladding die may also comprise one or more means for supplying the cladding material by applying an overpressure thereto. Said material can come into contact with the rod by different channels in the die. Depending on the section of the die and / or the presence of different channels and / or the application of overpressure (s) and / or the positioning of the beam in the die, the quantity of material (s) delivered (s) may be different at different points of the beam section.

The sheath melt generally comes from at least one extruder. The cutting device may in particular be a granulator or a bur, as mentioned above.

The various elements of the device according to the invention may be fixed or possibly mobile (in translation and / or in rotation).

The invention also relates to a composite product obtained by molding from the rods according to the invention. The rods according to the invention make it possible to obtain, at high rates, complex parts (possibly comprising ribs, bosses, etc.) having a satisfactory distribution of the reinforcing material, the composites obtained from these rods further having good mechanical properties.

The composites obtained from the rods according to the invention can be, for example, automobile body parts such as front faces, dashboards, door modules, engine screens, tailgate linings, etc.

Claims

A method of manufacturing concentrated reinforcing rods in which at least one wire bundle having more than 70% by weight of reinforcing material and at least 0.1% moisture is heated and shaped before being cut into sticks.

2. Method according to claim 1, characterized in that at least a portion of the son are composite son formed of reinforcing filaments, preferably glass, and filaments of at least one thermoplastic organic material.

3. Method according to any one of the preceding claims, characterized in that the wire bundle is further subjected to a cladding step by passing through a die fed with at least one organic material, and optionally at least one additive.

4. Device for implementing the method according to claim 3, characterized in that it comprises one or more means for supplying at least one bundle of wires, at least one heating means of said bundle, at least one shaping device, at least one cladding die and at least one cutting device.

5. Concentrated reinforcing stick having a reinforcing ratio greater than 65% by weight, these reinforcements being bonded or embedded in at least a first organic material and, where appropriate, sheathed with at least one second material.

6. Stick according to claim 5, characterized in that it has a fibril level of less than 60 mg / kg.

7. Composite obtained by molding from rods according to one of claims 5 or 6.