FR2504449A1 - Fibre reinforced thermoplastic profiles made by pultrusion - to produce long profiles which can later be modified - Google Patents

Abstract

Profiles of fibre-reinforced thermoplastic materials are made by pultrusion through a die having a chilled zone following the hot zone. Esp. for mfr. of vehicle bumper bars or similar structural profiles, straight or curved. Ther thermoplastic matrix allows complementary profiles to subsequently be joined together by fusion or solvent welding, e.g. to fit overrider or corner profiles to a continuous curved profile, more readily than for profiles with a thermoset matrix. Parts of the profile can readily subsequently be reshaped, e.g. to provide sharply curved ends on a length of gently curving profile. The prods. may be coloured in bulk or subsequently coloured by painting, electroplating etc..

Description

Production by pultrusion of profiles from thermoplastic polymers
The present invention relates to a process for producing, by pultrusion, straight or curved profiles, from fibers impregnated with thermoplastic polymers. Its application is particularly advantageous in the field of motor vehicles, in particular for the manufacture of bumpers or structural elements.

We already know the manufacturing process by pultrusion of profiles from fibers such as glass fibers impregnated with polyester resins, by drawing through a heated die, as well as various applications which have been carried out. However, the use of thermosetting resins constitutes a limitation for the subsequent ability of the profile to be partially thermoformed, or welded to a thermoplastic, or else bonded by local dissolution.

On the contrary, the profiles produced according to the invention by pultrusion from thermoplastic polymers, reinforced with fibers, have multiple advantages, in particular the following possibilities which will be detailed later - a subsequent forming of the profiles, from the semi-finished product
obtained by pultrusion - an overmolding with local welding - assembly by local dissolution or welding - decoration by processes specific to thermo materials
plastics
The materials used according to the invention can be chosen from those mentioned below, without limitation - for reinforcements, mineral fibers such as glass, because
bone, etc are suitable and are used in a looped state
or not, with or without the addition of mat or strip fabric.
vegetable fibers such as jute, sisal, hemp, may be suitable,
as well as certain organic fibers, provided, in this latter
deny that their softening point is at a temperature
at least 300 higher than that of the impregnation polymer.

All these fibers are also preferably used in the form
wicks drawn from spools
impregnation - For resins / thermoplastics, preferably use
low viscosity polymers in the melt, such as poly
amides, because they present facilities for impregnation.

However, the methods according to the invention are compatible with
the use of various known thermoplastic polymers: poly
olefins and their derivatives copolymerized or modified by elas
tomers, polystyrenics and ABS copolymers, polycarbonates,
polyacetals, thermoplastic polyesters, polyoxymethylene, etc.

Special mention must be made for PVC which, in the form
of plastisols, lends itself particularly well to the process by impregn
bathing.

The principle of the method according to the invention consists in drawing through a die made to the desired shape, a certain quantity of threads or rovings, for example based on glass, associated or not with mats or fabrics, the first part of the die being designed so as to allow the impregnation of these fibers with a molten thermoplastic polymer, the second part being cooled so that the product is frozen in shape at the outlet of the die.

Various arrangements of the invention will now be described by way of non-limiting examples; they are particularly aimed at solving the impregnation difficulties inherent in the high viscosity of polymers in the molten state, and will be illustrated by the attached figures i to 9 which relate respectively - FIG. 1, to a view in longitudinal section of a provision of
injection pultrusion - Figure 2, a similar view of a first variant by mixing
of fibers - Figure 3, a similar view of a second variant by saupou
drage - Figure 4, a similar view of a third variant by impré
gnation - Figure 5, a similar view of a detail showing more particu
an example of the die and the drawing device in the
case of the manufacture of a curved profile - FIG. 6, in a plan view of a bumper obtained according to the
vention - Figure 7, a similar view of another bumper using
the possibilities offered by the invention; - Figure 8, a cross section of a bumper using a
another possibility of the invention - Figure 9, to a cross section of a product obtained according to
the invention.

Let us consider the embodiment illustrated in FIG. 1, which relates to a pultrusion process by injection of thermoplastic material.

Wicks of fibers 2 unwound from the reels 1 are assembled in a conventional manner by jigs 3 to enter the die 4 where there is arranged an orifice 5 for feeding molten thermoplastic polymer, under pressure, opening into a chamber 6, regulated in temperature by resistors or hot fluid circuits 7.

An insulator 8 separates this part of the die from the second part which is cooled by cold fluid circuits 9 and the profile is driven at its exit by conventional means such as tracks 10, or any other traction process.

The continuous semi-finished product thus obtained can then be cut, stored and possibly re-processed, taking into account its thermoplastic properties.

The embodiment illustrated in Figure 2 uses the mixture of reinforcing fibers and resin.

According to this arrangement, the injection device for molten thermoplastic polymer is eliminated by using the ability of these polymers to be in the form of threads, films of fibrils or strips, which we will call "threads" below.

According to this new arrangement, the wicks brought into the template 23 are formed from coils 21 containing for example glass fibers and coils 22 containing son of thermoplastic polymers. The mixture of reinforcing fibers and son of the polymer is brought into the die 24 constituted in a similar manner to the previous one, with the heating circuits 27, the insulation 28, the cooling circuits 29 and, optionally, a conical inlet 25 with rounding 26.

 By heating, the wires of thermoplastic polymers, entrained by the reinforcing wicks, are melted, permeate the latter, and the whole is then cooled in shape and drawn by means 20.

According to one of the advantages of this process, the relative rates of reinforcement and impregnating resin can be precisely determined by acting on the relative quantities of the yarns and fibers by the number of coils of each constituent, the title of the yarns, etc.
According to another advantage, it is possible to use a charged polymer in the form of a wire supplying the die, hence the possibility of impregnating the mass of reinforcing fibers with resin and fillers, which is more difficult in the case of the impregnation by injection because of the phenomena of filtering of the charges due to the high density of the reinforcing fibers.

It is naturally possible, by combination of the above elements, to impregnate the reinforcements with mixtures of polymers, optionally containing different fillers, or to preferentially locate the local impregnation with such or such polymer specially chosen for its characteristics. intrinsic.

In the device of FIG. 3, the thermoplastic polymer is brought in the form of powder upstream of the die, using ap or fibers or fibers titrating fibreg, organic electrostatically, which facilitates the temporary fixing of particles on their surface. .

According to this method, the reinforcing fibers, for example of glass, are unwound from the coils 31 and are electrostatically charged by friction against rods 32 or on a template such as 33 They are then either sprinkled with the polymer powder using a machine for distributing and dosing powder by shaking or vibration, or brought through a chamber 35 comprising a loose peripheral seal 36 where the polymer powder is stirred by blowing compressed air with cannulas 37 for create the equivalent of a fluidized bed according to a known technique, or by any other means such as a stirring fan 38. The polymer powder fixed on the reinforcing fibers is entrained towards the inlet of the die 39 similar to that described above.

A particular advantage of this process lies in the possibility of using low-cost polymers such as coming out of bulk reactors, by eliminating all the granulation, bagging operations, etc.
FIG. 4 shows a device for implementing the invention by impregnation
As certain polymers are likely to be readily available in liquid form, either in solution in a solvent, or in emulsion or by pasting in a plasticizer (in the case of polyvinyl chloride for example), the impregnation of the reinforcing fibers can be carried out by immersion , possibly followed by spinning between rollers, before entering the die.

The wicks 42 unwound from the coils 41 are brought together by a template 43 then driven by rollers 44, 45, 46, 47 inside a tank 48 containing the plastisol or the solution 49 then between wiping rollers 40. A pre-drying for the evaporation of the solvent before the entry of the product obtained in the sector will be carried out by infrared panels in particular in the case of polymers in solution.

The same device is applicable in the case of monomers polymerizable in situ: the reinforcing fibers are then impregnated with the monomer comprising its crosslinking adjuvants, for example a caprolactam, then the passage through the first part of the die determines the formation of the polyamide " 6 "in the polymerized and molten state, the second part of the die allowing, as before, the cooling to form.

The die used for the implementation according to this process is made of polished steel, possibly chromed, and has straight sections to produce straight profiles, or a straight or curved section corresponding to the heating zone followed imperatively by a section curve at the desired radius for the cooling zone, when a curved profile is desired. In the latter case, a pulling device along the same radius of curvature is adopted, as shown diagrammatically in FIG. 5 or the rectilinear heating part 51 is connected to the cooled curved part 52, supplemented by curved drive tracks 43 and 44
The profiles obtained according to the methods described above have many advantages, especially in the automotive field.
Indeed, by the choice of reinforcements, in particular with glass fibers at a high rate of the order of 40 to 70%, it is possible to obtain rigid profiles of good impact resistance, colored in the mass. the presence of a thermoplastic polymer used as a binder also allows possibilities which are not offered by the use of thermosetting polymers
Thus the bumper 60 of Figure 6 is obtained by subsequent thermoforming of the ends 61-62, which have a radius of curvature different from that of the semi-finished product from the pultrusion operation.

FIGS. 7 and 8 illustrate the capacity for overmolding with local welding of a piece of thermoplastic polymer on a semi-finished product of the same material, come by pultrusion.

Indeed, it is known that real "autogenous welds" can be obtained by overmolding a polymer on a part already molded with this same polymer, the contribution of heat from the injected material partly recasting the surface of the object already molded.

This ability can be used, for example according to FIG. 7 in the case of a bumper, for molding lateral flanges such as 72 and 73 on a curved or straight section 71, or locally fitting bosses therein such as 74 and 75 or again, a skirt such as 82 on the section 81 of FIG. 8.

FIG. 9 shows another type of assembly that can be produced according to the invention by local dissolution and / or welding.

The addition of a solvent for the polymer at a determined location on the profile can make it possible to dissolve it locally and to stick another part to it. Likewise, all operations usually carried out for the assembly of thermoplastic parts are made possible by ultrasonic welding, by rotation, by heating, by dielectric losses, etc. Thus, in the case of a round profile, it is possible to weld a part such as 92 by rotation or by ultrasound on profile 91, then to practice in 93 a mirror weld to fix a part such as 94. These means therefore allow in general to assemble various types of profiles together, or to other parts.

 Another advantage according to the invention lies in the possibility of carrying out on the parts obtained a decoration by the methods suitable for thermoplastics. The presence of the thermoplastic polymer makes possible commonly used decoration methods such as decorative film fixed by hot transfer, vacuum metallization, ion spraying, various applications of primers, lacquers, coatings by electrolytic deposits, etc.

Claims (10)

1. Method for producing profiles by pultrusion, in particular for or '.'lémntsd structure the production of bumpers for motor vehicles iescarac erise by the fact that reinforcing fibers are intimately mixed with a thermoplastic synthetic material, the product thus obtained then being pulled through a die made up of two temperature-controlled zones, hot and cold respectively. 2. Method according to claim 1, characterized in that the thermoplastic material is mixed with the reinforcing fibers by injection into the hot zone of the die. 3. Method according to claim i, characterized in that the thermoplastic material is mixed with the reinforcing fibers constituting a wick from the start of the operation, in the form of possibly loaded son, distributed in the wick where they are dosed and located in function of the resistance zones to be obtained in the final profile. 4. Method according to claim 1 characterized in that the thermoplastic material is supplied in the form of powder, distributed using a distributor and metering device known per se and located upstream of the die, on the reinforcing fibers electrostatically loaded. 5. Method according to claim 1, characterized in that the powdered thermoplastic material constitutes a fluidized bed which is crossed by the reinforcing fibers 6. Method according to claim 1, characterized in that the thermoplastic material permeates the reinforcing fibers by immersion in a container containing it, located upstream of the die, followed by a pre-drying by means of infrared panels. 7. Bumpers or structural elements produced by pultrusion, characterized in that they are produced by pultrusion of reinforcing fibers mixed with a thermoplastic synthetic material.  8. Bumper according to claim 7, characterized in that its  ends, whose radius of curvature is different from that of the pro  basic yarn obtained by pultrusion, are obtained during a  subsequent thermoforming operation.  9. Bumper according to claim 7, characterized in that  additional parts, such as side plates, bos  wise men or skirts, are added by overmolding, with welding  local, on a semi-finished product obtained by pultrusion.  lytics and coating of lacquers.  10. Bumper according to claim 7, characterized in that its surface is treated by means of decoration methods specific to thermoplastic synthetic materials, of the vacuum metallization type, hot transfer, ion spraying, electro deposits