The invention relates to an apparatus for the impregnation of fibre bundles by passing them through a, preferably thermoplastic, polymer melt. The apparatus comprises a receptacle for the polymer melt and in this receptacle there are means for spreading the fibres as they are passed through. The invention also relates to a method for the impregnation of fibre bundles by means of the apparatus.

Such a combination of apparatus and method is known from European patent specification EP-A-0 320 653. It describes an apparatus for the impregnation of fibre bundles in which the fibres are spread with the aid of means consisting of a series of interacting rolls having a convex and concave outer surface. By guiding the fibre bundles to be impregnated over the rolls under a certain tensile stress, they will be spread, which facilitates the wetting'of the fibre bundles by the polymer melt and the complete encapsulation with polymer melt of the individual filaments of the fibre bundles.

In order to obtain a good impregnation of the fibre bundles using the known apparatus as described in EP-A-0 320 653 it is essential that the convex and concave rolls are positioned relative to each other such that a narrow slit is formed between

their outer surfaces, through which the fibre bundles to be impregnated are squeezed out as it were. As a consequence of the high friction forces that are generated, this treatment entails considerable damage to the fibre bundles, in particular at average to high throughput speeds. Rupture of filaments at the slit results in accumulations of shreds of fibre bundles on the rolls, which accumulations cannot be removed. These interfere seriously with the impregnation process, may end up in the final product and so have an adverse effect on the final product's mechanical properties. In some cases the forces exerted on the fibre bundles during the operation of the state-of-the-art apparatus are so high that even rupture of entire fibre bundles occurs.

The aim of the invention is to provide an apparatus for the impregnation of fibre bundles with a polymer melt which is capable of ensuring a good impregnation and this in particular also at average to high throughput speeds, with virtually no occurrence of fibre bundle rupture and with either virtually no formation of accumulated shreds of fibre bundles or with automatic removal of any such accumulated shreds.

The apparatus according to the invention is to that end characterized in that the means for spreading the fibre bundles consist of a number of rolls, positioned virtually transverse to the direction of throughput and having a cone-shaped outer surface, the top part of which is suspended free in the receptacle.

When the means for spreading the fibre bundles are designed in accordance with the invention a much better impregnation is achieved, surprisingly, than with the state-of-the-art apparatus at average to high throughput rates. Moreover, during operation any accumulations of shreds of fibre bundles will be removed along the cone-shaped outer surface via the top section to the polymer melt present in the receptacle.

The rolls in the apparatus according to the invention may be suspended in the receptacle in such a way that they are immobile, freely rotating or can be driven. The apparatus according to the invention preferably comprises means for controlling the speed of rotation of the rolls, preferably independently of the throughput speed of the fibre bundles. Optionally it is possible to drive only part of the rolls and/or each of the rolls separately with its own speed of rotation. By driving the rolls in a direction of rotation which corresponds to the direction of throughput of the fibre bundles, the viscous frictional forces which the fibre bundles are subjected to at the contact surface with the rolls are significantly reduced, the viscous frictional forces becoming lower as the difference between the speed of rotation of the roll and the throughput speed of the fibre bundle becomes smaller.

The apparatus according to the invention offers the additional advantage that it is possible to choose the speed of rotation of the rolls to be virtually equal to the throughput speed of the fibre bundles at average to high throughput speeds. This is impossible with the

state-of-the-art apparatus according to EP-A-0 320 653 because rupture of filaments results in accumulations of shreds of fibre bundles on the rolls which rotate along with the rolls ("move round") and soon block the impregnation process. Since according to the invention it is now possible to choose the speed of rotation of the rolls to be virtually equal to the speed of throughput of the fibre bundles, the fibre bundle tension is reduced and the impregnation quality is improved.

By an average throughput speed in the context of the invention is understood a throughput speed of 20 to 50 m/min, and by a high throughput speed a throughput speed of at least 50 m/min.

The advantages of the apparatus according to the invention are particularly manifest when the outer surface of at least one roll has the shape of a rounded cone.

The process and method according to the invention can be used for the impregnation of an unrestricted range of fibrous materials. Examples of suitable fibrous materials are glass, carbon, aramid, silicon carbide, jute, coir, wood, cellulose, aluminium oxide, asbestos, ceramic, graphite, metal and/or a stretched polymer, such as for instance stretched ultrahigh molecular weight polyethylene, and/or combinations thereof. Preferably the fibrous material consists of glass, carbon, aramid and/or ultrahigh molecular weight polyethylene. Most preferably, glass fibre bundles are used

Where in this patent application the term fibre bundle'is used, a bundle consisting of in any case a plurality of filaments and mostly of one or more rovings is meant. A roving consists of a number of strands, which are composed of continuous, parallel filaments. Suitable glass fibre bundles preferably consist of 500 to 10,000 filaments with a diameter of 5 to 25 pm. The weight of the glass fibre bundle is usually expressed in the tex number, i. e. the weight of the bundle per running kilometre. Most commercially available glass fibre bundles have a tex number of between 480 and 4800 g/km, but tex number values outside these limits can also be used in the process and the apparatus according to the invention. The glass fibre bundles are optionally provided with a sizing consisting of a bonding agent-usually a silane compound-which is to promote for instance the bonding with the thermoplastic polymer, and a film former, which among other things is to improve the processing characteristics of the fibre.

The method and apparatus according to the invention can be used for the impregnation of fibre bundles with any type of polymer. It is possible for instance to use the method and apparatus according to the invention for the impregnation of thermosetting polymers, such as for instance unsaturated polyester resins, epoxy resins, melamine and/or phenolformaldehyde resins, vinyl ester urethane resins, etc. The polymer preferably is a thermoplastic because thermoplastics have a high melt viscosity and are

consequently poorly capable of wetting fibre bundles.

This means that these polymers in particular bring out the advantages of the apparatus and method according to the invention. All thermoplastic (co) polymers are suitable, such as polyamides (PA), for instance nylon 6, nylon 6.6, nylon 4.6, nylon 8, nylon 6.10, nylon 11, nylon 12, etc., polyolefins, for instance polypropylene ( (PP), polyethylene (PE), polytetrafluoroethylene (PFTE), polyphenylene ether (PPE or PPO), etc., amorphous and/or crystalline polyesters such as polyalkylene terephthalates, for instance polyethylene terephthalate (PETP or PET), polybutylene terephthalate (PBT), etc., or polyimides such as for instance polyether imide (PEI), polyamide imide (PAI), or polymethyl (meth) acrylate (PMMA), polyether methacrylate (PEMA). Also suitable are polyphenylene sulphide (PPS), polyvinyls such as polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), ethylene vinyl acetate (EVA), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), copolymers of vinyl chloride and vinylidene chloride or polyvinylidene fluoride (PVDF), polyethylene glycol (PETG), styrene-containing copolymers, such as polystyrene (PS) with or without rubber, styrene- acrylonitrile copolymers (SAN), acrylonitrile- butadiene-styrene polymers (ABS), styrene maleic anhydride (SMA), polyacrylonitrile (PAN), polyarylene sulphide ketone, polyoxymethylene (POM), polycarbonate (PC), polyethers (PEth), polyether ketone (PEK), polyether ketone ketone (PEKK), polyether ether ketone (PEEK), polyacetals, polyacrylic acid, polyurethanes

(PUR), polyarylic acid (PAA), cellulose esters, polybenzimidazole (PBI) and blends of these thermoplastics. The foregoing enumeration of thermoplastic polymers is given by way of example. It will be clear that the method according to the invention is not restricted to the enumerated thermoplastics.

Moreover, it will also be clear that the term polymer melt as used in the context of this patent application also comprises despersions, solutions and the like which can suitably be used for impregnating fibre bundles using the apparatus and method of the invention.

The apparatus and method of the invention are preferably used for the impregnation of fibre bundles with thermoplastics of a high melt viscosity.

By a high melt viscosity in the context of this patent application is understood a melt viscosity corresponding to a MFI (Melt Flow Index, measured according to ISO 1133) of at most 30 dg/min. More preferably, the MFI is at most 25 dg/min., most preferably at most 20 dg/min.

The impregnated fibre bundles obtained by application of the apparatus and method according to the invention can be used for the manufacture of fibre- reinforced (semi-finished) products. It is possible for instance to obtain bar-shaped and/or plate-shaped product by cooling the thermoplastic polymer after impregnation with the thermoplastic polymer. It is also possible for instance to wrap the impregnated fibre

bundles of the invention around a relatively cool mandrel, with the optional use of press-down rolls to consolidate the impregnated fibre bundles. The wrapping can be effected immediately upon the impregnation, so that the thermoplastic polymer is still in the molten state, but it is also possible to heat up the impregnated fibre bundles separately to the melting point of the thermoplastic polymer prior to wrapping.

Another possibility is to produce bar-shaped granules by means of the method and apparatus of the invention.

Such granules comprise a thermoplastic polymer and reinforcement fibres, preferably glass fibres, which reinforcement fibres extend longitudinally through the granules and are of the same length as the granules and are produced by impregnating fibre bundles with application of a method according to any one of the Claims 5-9 and then cooling the strand of fibres and thermoplastic polymer thus obtained, for instance by passing it through a water bath, and subsequently comminuting the cooled strand to obtain the granules, for instance by cutting it to the desired length by means of a granulator.

The desired length is preferably between 5 and 15 mm if the polymer granules are to be processed to an object by injection moulding. In case of processing with application of other techniques, for instance by compression moulding, a greater length can be chosen, for instance up to 100 mm. A restricting factor for the length of the polymer granule in the case of processing by injection moulding is for

instance the circumstance that feeding of the granulate to an injection-moulding machine becomes more difficult with increasing granule length.

It has been found that with the apparatus and method according to the invention well impregnated granules can be produced, with very high rates of production being achievable, so that production of the granules on an industrial scale is possible.

The granules preferably contain 10-70 wt. % of glass fibres and a total of 90-30 wt. % of polymer, more preferably 30-50 wt. % of glass fibres and a total of 50-70 wt. % of polymer.

The granules according to the invention can be processed in the customary ways to parts, such as for instance by compression moulding, injection moulding and extrusion moulding. Examples of such moulded parts are housings of electronic and eletromechanical equipment, machine components and automobile components, such as for instance bumper bars, dashboard carriers, parcel shelves, fascias and chair frames.

The apparatus and method according to the invention offer the additional advantage that the moulded parts made from the granules produced according to the invention can possess good mechanical properties.

For the purpose of further elucidation a preferred, non-restrictive embodiment of the apparatus and method according to the invention will be discussed with reference to the figures.

Figure 1 presents a schematic top view of a horizontal section of the preferred embodiment.

Figure 2 presents a schematic side view of a vertical section of the preferred embodiment.

The apparatus consists of a receptacle 1 with cover 2 in which the polymer melt 3 is contained.

The receptacle 1 is provided with an inlet 4 for the fibre bundle 6 to be impregnated and an outlet 5 through which the impregnated fibre bundle 6 leaves the receptacle 1. An inlet 7 for the polymer melt 3 can be made at the place (on the inlet side face) indicated in Figure 2. It is also possible, however, to make the inlet 7 on the front or the back face of the receptacle 1. The inlet 7 is connected to an extruder (not shown in Figs. 1 and 2) for melting the polymer to be extruded. The extruder supplies polymer melt 3 to the receptacle 1 via inlet 7, continuously and with the desired flow rate. The flow rate of the extruder is generally controlled such that-taking into account the speed of throughput of the fibre bundle 6-during operation the receptacle 1 is and remains virtually completely filled with polymer melt 3.

As indicated in Figs. 1 and 2 a fibre bundle 6 to be impregnated is passed over a number of rounded conical rolls on which the bundle 6 is spread.

The rolls 8 are positioned virtually transverse to the throughput direction x and have a rounded conical outer surface 8a, the top part 8b of which is suspended free in the receptacle 1. During operation any accumulated shreds of fibre bundles are automatically carried off

to the polymer melt 3 via this top part 8b.

The rolls 8 are driven by a connecting-rod and chain mechanism 9 connected to a motor (not shown in Figs. 1 and 2). The receptacle 1 is optionally provided with guide pins 10 which can help to set the path of the fibre bundle. The guide pins 10 are provided with screw holes, enabling the cover 2 of the receptacle 1 to be fastened onto the guide pins 10 by means of bolts 11. In the cover 2 of the receptacle 1 two removable guide pins 12 are included. Due to these guide pins the fibre bundle 6 is passed over a larger section of the outer surface 8a of rolls 8. The rolls 8 are placed in pairs one behind the other in such a way that the base 8c of each role is adjacent to the top section 8a of the preceding role, so that they interlock as it were. Figure 1 shows an embodiment in which, seen from the left, the first and the second roll interlock with each other in this way. The third and the fourth roll also form an interlocking pair.

The path along which the fibre bundle is guided is in principle arbitrary and depends on a large number of factors, such as for instance the type of fibre bundle that is being impregnated, the throughput speed of the fibre bundle, the fibre/polymer ratio, the speed of rotation of the rolls 8 (if they are driven), the melt viscosity of the polymer, etc. Figure 5 shows a possible fibre bundle path.

For further elucidation, a photo of the preferred embodiment of the apparatus is presented as Figure 3.

In Figure 4, finally, the same embodiment is shown, but with the front side removed.

It will be clear that the above-described preferred embodiment can be adapted in several respects by the person skilled in the art, without deviating from the inventive conception. It is possible for instance to have the inlet 4 for the fibre bundle coincide with the inlet 7 for the polymer melt or the other way round. It is also possible to use more rolls than the four rolls 8 indicated, with the option of having each roll driven separately. It is evident that the apparatus of the invention can comprise means of heating to keep the polymer melt in the receptacle above the melting point of the polymer for a prolonged period of time. The walls of the receptacle 1 can for instance comprise heating elements. It is also possible, however, to heat the rolls 8. Further it will be clear that the apparatus of the invention can comprise a feed-through and, optionally, winding mechanism with which the (impregnated) fibre bundle can be pulled through the receptacle. Preferably, an impregnated fibre bundle 6, upon exit via outlet 5, is cooled to below the melting point of the (thermoplastic) polymer, for instance by passing the fibre bundle 6 through a water trough.

The invention will be further elucidated by means of the following non-restrictive examples.

Example I A glass fibre bundle (Vetrotex P319,2400

tex, from Vetrotex, France) was pulled through the preferred apparatus as described above, with throughput speeds of 10,25,50,75 and 90 m/min. Using a Schwabenthan'"single-screw extruder, connected to the inlet of the receptacle, a thermoplastic polymer (Stamylan 112MN40, a polypropylene homopolymer from DSM, The Netherlands, with a MFI of 20 dg/min according to ISO 1133) was supplied continuously to the receptacle. The temperature profile set across the extruder (from hopper to head) was: 240-240-250-260°C.

The head temperature was 270°C. The speed of rotation of the extruder screw was set at 4,6,16,23 and 32 rpm (revolutions per minute), respectively. The fibre bundle was passed over the rounded conical rolls in a straight line from inlet to outlet. The rounded conical rolls were driven such that the speed of rotation at their outer surface was about equal to the speed of throughput of the fibre bundle. The impregnated fibre bundle (the strand') was passed through a water bath at room temperature for cooling. The glass content of the strand was virtually independent of the speed of throughput and amounted to an average of 20 vol. %. The average tensile force on the strand during its passage through the receptacle was between 60 and 95 N. With all the specified throughput speeds it was found to be possible to produce a well impregnated strand, without any significant fibre rupture occurring. Any shreds of fibre bundle gathering on the rolls were automatically carried off to the polymer melt, so that fibre rupture hardly occurred. Shreds of fibre bundle caught in the

polymer melt were occasionally carried off by the strand in the form of small shreds which did not affect the mechanical properties.

Comparative expriment A In the same way as described above, a glass fibre bundle (Vetrotex P319,2400 tex, from Vetrotex, France) was pulled through the preferred apparatus.

However, in the receptacle of the apparatus the rounded conical rolls according to the invention were replaced by non-driven, but free rotating cylindrical rolls.

Driving the cylindrical rolls appeared not to be possible, because fibre bundles shreds got stuck on the rotating rolls, which after a few minutes resulted in fibre bundle rupture. Using a Schwabenthan"single- screw extruder, connected to the inlet of the receptacle, a thermoplastic polymer (StamylanTM 112MN40, a polypropylene homopolymer from DSM, The Netherlands, with a MFI of 20 dg/min according to ISO 1133) was supplied continuously to the receptacle. The temperature profile set across the extruder (from hopper to head) was: 240-240-250-260°C. The head temperature was 270°C. The speed of rotation of the extruder screw was set at 4,6,16,23 and 32 rpm (revolutions per minute), respectively. The fibre bundle was passed over the cylindrical rolls in a straight line from inlet to outlet. The impregnated fibre bundle (the strand') was passed through a water bath for cooling. The glass content of the strand was 20 vol. % on average. The average tensile force on the

strand during its passage through the receptacle was between 120 and 150 N at the lower throughput speeds, much higher than in the method according to the invention. After a few minutes the apparatus was stopped and the receptacle was opened. The four cylindrical rolls all appeared to be covered with shreds of broken filaments. At a throughput speed of 50 m/min. fibre bundle rupture occurred within a few minutes after the start, so that the process had to be stopped. At 75 and 90 m/min., fibre bundle rupture occurred almost immediately after the start, so that it was not possible to make an impregnated strand.