METHOD AND APPARATUS FOR TREATING ASSEMBLIES OF CONTINUOUS FILAMENTS

Abstract: The invention relates to a method of treating compositions formed from filaments with a treating agent, comprising the steps of: introducing the compositions into a treatment space and simultaneously supplying a fluid, expanding the fluid and spreading the filaments within the composition, supplying the agent, mixing the agent with the filaments, and bringing the treated filaments together, characterized in that, after spreading the filaments, a part of the at least partially expanded fluid is discharged in a controlled manner. Such a method provides a very good spreading of the filaments and a very good distribution of treating agent on the filaments. The products obtained by this method therefore show a very good distribution of the treating agent over the filaments. Moreover, only very little agent-loaded fluid is discharged.

Description: METHOD AND APPARATUS FOR TREATING ASSEMBLIES OF CONTINUOUS FILAMENTS The invention relates to a method of treating composites formed from continuous filaments with a treating agent, comprising the successive steps of: introducing the composites into a treatment space and simultaneously supplying a fluid, expanding the fluid and spreading the filaments within the composite, supplying the treating agent, mixing the treating agent with the filaments, and - bringing the treated filaments together Such a method is known from Dutch patent application No. 7001623. According to said method, composites, in this case yarns consisting of a large number of filaments, are introduced into a treatment space through a venturi together with air as the fluid. The spreading of the filaments is in that case carried out through expansion of the air upon exiting the venturi. Then the treating agent is mixed with the spread filaments, after which the spread filaments are brought together. The products being obtained are impregnated filaments. In practice such a method has appeared to effect an acceptable spreading of the filaments. Because of the large amount of fluid being introduced into the treatment space together with the composites, however, it is not very well possible to achieve a satisfactory mixture of the spread filaments with the treating agent. Consequently, the desired excellent mixture of the spread filaments with the treating agent hardly takes place, or at least to an insufficient degree. In particular if powdery materials are supplied as the treating agent, homogeneous mixture of the treating agent with the filaments hardly takes place, or only to a limited extent. The consequence of this is that the finished products, filaments impregnated with treating agent, are unreliable and/or do not possess the desired properties. Another drawback of this known method is the fact that the entire amount of fluid being supplied must pass through the entire device. Because of the fact that, in addition, a substantial part of the treating agent does not mix with the filaments, a large amount of treating agent and a large discharge flow of fluid will subsequently have to be separated in filtering plants. The object of the invention is to provide a method by which filaments of composites can be spread in a very satisfactory and very simple manner. Another object of the invention is to provide a method by which filaments can be mixed with a treating agent in a very satisfactory and homogeneous manner. A final object of the invention is to provide a method wherein only little agent-loaded fluid is obtained. The advantage of this is that only little agent-loaded fluid will have to be purified. The above objectives are accomplished with a method of the kind referred to above, which is characterized in that, after spreading of the filaments, part of the at least partially expanded fluid is discharged in a controlled manner. An unexpected advantage of the method according to the invention is the fact that it is possible to use very low tensions on the filament composites. Probably, this is caused by the fact that the flow of fluid, which is introduced into the device simultaneously with the composites, draws the composites along into the inside, as it were. In particular, the composites may be carried along as a result of the expansion of the fluid. As a result of this, it is not necessary, or only to a limited extent, to exert a tension on the composites at the end of the device. This results in an improved spreading of the filaments in 3 the treatment space, as well as in a reduced tendency of the filaments to return to their original position after spreading. With the method according to the invention, wherein part of the at least partially expanded fluid is discharged in a controlled manner, the filaments are spread, and remain in that condition, to a position near the walls of the treatment chamber. As a result of this, the treating agent only needs to travel a very short distance upon being supplied from means which are disposed in the walls of the treatment space. Thus, a quick and homogeneous distribution of the treating agent over the filaments is obtained. Another surprising advantage is the fact that it has appeared to be possible with the method according to the invention to use very high filament velocities. A very good spreading of the monofilaments is even obtained at very high velocities (even above 300 m/min) of the filament composites. It is possible to use velocities of up to 500 m/min. It has become apparent that the use of highly viscous treating agents in the method according to the invention has less influence on the treatment time than is the case with the method according to the prior art. This is made possible by the very homogeneous distribution of the treating agent over the filaments. In the event that powdery thermoplastics are used, powders having relatively large grain dimensions can be processed. The maximum grain dimension that is possible depends on the viscosity. This leads to a considerable saving, because powders (for example powders which have been directly obtained from a polymerisation reaction) do not need to be ground to a smaller dimension, or only to a small extent. Although this is not necessary, it is possible to provide for the pre-spreading of composites, using one or more air knives, when composites are used wherein the filaments stick together, for example as a result of excessive sizing in the case of glass filament composites. Said pre-spreading can be carried out very suitably in a separate space. According to a preferred embodiment, the device is therefore provided with a pre-compartment provided with means for pre-spreading the composites. The composites can then be supplied to the device according to the invention. According to the invention, the composites are introduced into the treatment space whilst a fluid is supplied simultaneously therewith. This can for example be done by passing the composites and the fluid through one or more controlled fluid flow accelerators. A venturi can be very suitably used as a fluid flow accelerator. The fluid and the composites are passed through the fluid flow accelerator in substantially the same direction. As a result, the filaments are drawn along with the fluid. The direction of the force that occurs thereby corresponds to the direction of movement of the filament composites. During the passage through the treatment space, the tension on the filament composite is gradually built up again after the treatment space. As a result of this, the spread filaments will be brought together again to form a closed bundle, which is impregnated with the treating agent. Due to the use of this method, hardly any fracture of filaments will occur. In this case it is preferred to use a conical space for bringing together the spread filaments. This will have an accelerating effect on the fluid, as a result of which the filaments will be drawn along towards the discharge means. This contributes towards minimising the tension which is to be imposed on the filaments for discharging the filaments from the device. It is possible to use gases, for example inert gases or air, or liquids or mixtures thereof as said fluid. The invention furthermore relates to a device for carrying out such a method, which device comprises a treatment space provided with supply means for supplying said composites and with discharge means for discharging the treated composites, wherein said supply means are provided over at least part of their circumference with one or more continuous or interrupted fluid supply means for passing the composites through the supply means in the treatment space, wherein the cross-sectional area of the treatment space increases from said supply means, seen in the direction of transport, wherein the treatment space is provided over at least part of its circumference with fluid discharge means and wherein the treatment space is provided over at least part of its circumference after said fluid discharge means, seen in the direction of transport, with means for supplying treating agent. The supply means for supplying the composites may be provided with said fluid supply means on their circumference or on the inside. It is also possible to use both forms. The method and the device according to the invention are suitable for fabricating composite semi- finished products in the form of strands and the like, or in the form of chopped granulated material. The impregnated filament composites are for example suitable for filament winding. The granulated material is very suitable for use in extrusion, pressing and injection-moulding processes, for example. The treated filaments which have been fabricated by means of the method according to the invention can be used for manufacturing materials having varying properties, such as thermoplastic or thermosetting polymer composites, ceramic and carbon matrix composites (CMC's and CCMC's), metal matrix composites (MMC's) and anorganic materials such as fibre-reinforced cement, wherein continuous and long filaments function as a reinforcing material. Suitable filament composites which can be treated with the method according to the invention are for example aramid, boron, carbon, ceramic material, glass, graphite, metal, silicate and a great many synthetic fibres. The filament composites which can be treated with the method according to the invention especially include filaments which are well-known for their great mechanical strength and/or stiffness. Suitable composites are especially those composites that comprise the following materials: aluminium, aluminium nitride, aluminium oxide, aramid, asbestos, beryllium, boron, boron oxide, boron nitride, glass, carbon, cobalt, copper, high silica and quartz, lithium aluminium silicate, single crystal sapphire, magnesium, magnesium oxide, mullite, molybdenum, nickel, polyalkene, such as polyester, polyethylene and polypropylene, silicon dioxide, silicon, silicon carbide, silicon carbon nitride, silicon nitride, steel and stainless steel, synthetic diamond, titanium, tungsten, zinc, zirconium, zirconia and threads consisting of any suitable combination of two or more of the above materials. It is preferred to used filament composites which comprise aramid, glass, ceramic material, carbon or graphite, possibly coated with a protective material. Polyester, polyethylene and en polypropylene are preferred most. It is also possible to use coated threads. The treating agent may for example be a powdery or gaseous vlere or materials present in the form of a melt, such as thermoplastic or thermosetting polymers, ceramic material and metals. Also combinations of two or more of the above materials are possible. Furthermore it is possible to combine said materials with a binder. Said binder may be a temporary binder or a permanent binder. Suitable temporary binders are natural or synthetic polymers and synthetic waxes having a low melting point, or mixtures thereof, which can be removed after the treatment by heating, for example. A great many materials may be used as a powdery treating agent. A large number of suitable materials are listed in WO-A-87/00563. In addition to the said materials, 7 also rubber powder and mixtures of several materials, such as a mixture of ceramic material, carbon and/or metal with a polymer powder are used. Important in this connection is the fact that the treating material being used must be capable of being fixated by elevated temperature, adhesion or by chemical action. If desired, a binder is used to effect said fixation. The binder may be a temporary binder, which is removed after further moulding of the treated composite, or a precursor binder, which undergoes pyrolysis after moulding. Binders are used in particular in combination with ceramic, carbon or metal impregnating agents. In order to prevent degradation of reactive treating agents when reactive materials such as aluminium or magnesium are used, said treating agents may be provided with a coating comprising a binder. Impregnating agents which are in particular suitable include one or more of the following materials: synthetic materials such as: rubber, polyacetal, polyamide 12, polyamide 6.6, polyamide 6, polyaryl sulfone, polybutene terephtalate, polycarbonate, polyethylene terephtalate, polyether-ester, polyether ether ketone, polyether sulfone, polyether imide, polyimide, polypropylene, modified polyphenylene oxide, polyphenylene sulphide, polyketone, polysulfone, PS/ABS/SAN, polyurethane and polyvinylidene fluoride; ceramic materials such as: aluminium oxide, silicon, silicon-dioxide, silicon carbide, silicon nitride, titanium oxide, tungsten, zirconium oxide, zirconium, carbon or graphite; metals such as: aluminium, cobalt, copper, lead, nickel, steel, titanium, tungsten, zinc- binders such as: polymethyl methacrylate, polyalkylene carbonate, polypropylene carbonate or an olefin polymer, preferably polyethylene or polypropylene, or a water-soluble binder, e.g. methyl cellulose, which are "clean combustion" binders, which can be removed after moulding of the impregnated semi-finished product, or organo-metallic compounds with a base of silicon, a polysilane or polysilazane, which are precursors; and polymer, metallo-organic mixtures. The best materials to be used in combination with carbon are precursor polymer binders, which leave behind a considerable amount of carbon after pyrolysis, such as: bulk mesophase/pitch, epoxy, furane, furfuryl alcohol, furfuryl ester, polyaryl acetylene (PAA), polyamide (PA), polybenzimid azole (PBI), polyphenylene sulphide (PPS) or phenolic polymer or mixtures thereof. Furthermore it is possible to add fillers, such as grains, platelets and/or needles and flakes to the treating agent . Further additives, such as antistatic agents, blowing agents, colouring agents, concrete or cement, linking agents, fillers, flame retarding agents, washing mixtures, foaming materials, heat stabilizers, hollow fillers, lubricants, mineral plasticizers, auxiliary processing materials, silicones, stabilizers, superalloys, UV absorbers, water-soluble plastics and "whiskers", can be added to the treating agent. No strict rules apply as regards the particle size of the powdery treating material to be used. It is possible to use powders having varying particle size distributions in the method according to the invention. At least part of the powder particles must be small enough to be incorporated between the filaments of the spread threads. Good results have been achieved in particular with a particle size distribution of the powdery polymer treating agent such that at least 90 % by weight of the particles has a diameter ranging between 5 μm and 250 μm, preferably between 20 μm and 200 μm. Examples of particle sizes with mixtures wherein a binder is used are: Aluminium/magnesium alloy (Al-Mg) having a particle size of 5 - 8 μm, SiC particles (1 μm) , and powdery polypropylene binder (15 - 20 μm) ; Aluminium/magnesium alloy (Al-Mg) having a particle size of 5 - 8 μm, SiC particles (0.5 μm) , and powdery polypropylene binder (15 - 20 μm) ; SiC powder (3.5 μm) and polysilane precursor-polymer binder (10 - 20 μm) ; graphite powder (3.5 μm) and polyamide (PA) precursor- polymer binder. The invention will be described in more detail hereafter with reference to the drawings, which show embodiments of the device according to the invention. Fig. 1 is a longitudinal sectional view of a device according to the invention. Fig. 2 is a view, in the direction indicated by arrows II-II in Fig. 1, of a multiple treatment line for filament bundles. Fig. 1 shows a longitudinal section of a device for treating composites consisting of continuous filaments. The continuous filaments are unwound from a bobbin 1 and supplied to the device, in this case via guide rollers comprising a floater arm 4, by means of which a low tension of a few grammes is imposed on the filament composites. The device comprises a supply opening 3, in this case in the form of a venturi 6. In this embodiment, the narrowest part of the venturi 6 is circumferentially provided with supply means 5 for a fluid. Said supply means may be in the form of a narrow, annular slot, for example. Very high fluid velocities are reached thereby, with a theoretic acceleration factor of 40 - 60 being possible. Energy is furthermore transmitted to the filament bundles. The cross- sectional area of the treatment space increases from the venturi, seen in the direction of transport. In this embodiment, the venturi is conical. The expanding fluid will impart a force on the composites entering the treatment 10 spaces 7 through venturi 6, such that the filaments will be spread at 8. In the illustrated embodiment, means for discharging at least part of the expanded fluid in a controlled manner are provided in the wall of the treatment space, at the end of the conical part. Said means are configured such that the amount of fluid to be discharged can be adjusted over a wide range. The velocity of the fluid which is not discharged is such that the spread filament composites 8 will remain spread. After part of the fluid has been discharged in a controlled manner, treating agent is supplied to the treatment space via supply means 10 provided in the wall, under a pressure which is slightly larger than the pressure that prevails in the treatment space. The treating agent is mixed with the spread filaments at 11. The filaments are then discharged from the treatment space through outlet opening 14 via guide means 12. Treating agent not being mixed with the filaments is withdrawn from the device, together with the remaining fluid, via means 13. Finally, the threads are transported further at 16, via guide means 15. Preferably, the treatment space has a conical shape. The fluid accelerating means will preferably consist of a venturi in that case. The treatment space may also have a rectangular or trapezoidal shape, however, and be flared, or possibly tapered. In that case, continuous or interrupted gaps and/or nozzles will for example be used as fluid accelerating means. The device may be disposed horizontally, vertically or at an angle. The walls of the part of the treatment space whose cross-sectional area increases, seen from the supply opening, preferably extend at an angle of maximally 30°, more preferably 5 - 10°, with respect to the central axis of the device. Discharge means 9, through which part of the at least partially expanded fluid is discharged, may be made up 11 of openings provided in the surface of the wall of the treatment space. According to another possibility, however, a continuous discharge opening in the form of a slot is provided on the circumference of the wall. The means 10 for supplying treating agents may be provided in the surface of the wall of the treatment space. Said means may also be made up of an element projecting from said wall, however, which opens in the centre of the space and through which the treating agent is introduced into said space. The treating agent can be supplied upstream or downstream relative to the direction of movement of the threads. Fig. 2 is a rear view of the device of Fig. 1. Like numerals relate to the same parts as in Fig. 1. Four devices are placed in parallel in this case. The invention is not limited to the above-described embodiment as shown in the figures, which can be varied in several ways within the scope of the invention. The method according to the invention may for example be carried out in separate, successive treatment spaces. Furthermore, additional treatments may be carried out, such as roughening the individual filaments with a powdery or suspended abrasive medium; for example; coating the individual filaments with a finishing or sizing agent or the like (for example steam) , in order to enhance the adhesion of the treating agent in a next step. Furthermore, the device may be provided with a control arrangement by means of which it is possible to control the pressure at which the fluid is supplied as a function of the tension on the composites supplied to the device. The tension can be determined by means of the floater arm 4 which is shown in Fig. 1

Claims: 12 CLAIMS 1. A method of treating composites formed from continuous filaments with a treating agent, comprising the successive steps of: introducing the composites into a treatment space and simultaneously supplying a fluid, expanding the fluid and spreading the filaments within the composite, supplying the agent, mixing the agent with the filaments, and - bringing the treated filaments together, characterized in that, after spreading of the filaments, part of the at least partially expanded fluid is discharged in a controlled manner. 2. A method according to claim 1, wherein said composites are introduced into the treatment space via fluid accelerating means. 3. A method according to claim 2, wherein said fluid accelerating means comprise a venturi. 4. A method according to any one of the preceding claims, wherein said treating agent is supplied by supply means which are disposed in the walls of said treatment space. 5. A method according to any one of the claims 1 - 4, wherein said treating agent is a thermoplastic having a particle size distribution such that at least 90 % by weight of the particles has a diameter of less than 50x, preferably less than 25x, the filament diameter. 6. A method according to any one of the claims 1 - 4, wherein said treating agent is a powdery glass, a glass-ceramic, a ceramic or a carbon material having a particle size distribution such that at least 90 % by weight of the particles has a diameter ranging between 0.01 μm and 10 μm, preferably between 0.1 μm and 5 μm. 13 7. A method according to any one of the claims 1 - 4, wherein said treating agent is a powdery metal having a particle size distribution such that at least 90 % by weight of the particles has a diameter ranging between 0.1 μm and 20 μm, preferably between 1 μm and 10 μm. 8. A method according to any one of the preceding claims, wherein said treating agent is a powdery binder having a particle size distribution such that at least 90 % by weight of the particles has a diameter ranging between 0.1 μm and 100 μm, preferably between 1 μm and 20 μm.A method according to any one of the preceding claims, wherein the spread filaments are passed through said treatment space at a velocity of 5 - 500 m/min, preferably 30 - 300 m/min, more preferably 60 - 200 m/min. 9. A fibre-reinforced composite product fabricated from a fila ent-reinformed composite material produced in accordance with the method according to any one of the preceding claims. 10. A device for treating composites consisting of continuous filaments in accordance with the method according to any one or more of the claims 1 - 9, which device comprises a treatment space (7) provided with supply means (3) for supplying said composites (2) and with discharge means (14) for discharging the treated composites, wherein said supply means (3) are provided over at least part of their circumference with one or more continuous or interrupted fluid supply means (5) for passing the composites (2) through the supply means (3) in the treatment space (7), wherein the cross-sectional area of the treatment space (7) increases from said supply means, seen in the direction of transport, wherein the treatment space (7) is provided over at least part of its circumference with fluid discharge means (9) and wherein the treatment space (7) is provided over at least part of its circumference after said fluid discharge means (9), seen in the direction of transport, with means (10) for supplying treating agent. 14 11. A device according to claim 11, wherein controllable fluid discharge means (9) are provided in the wall of the treatment space (7). 12. A device according to claim 12, wherein said fluid discharge means are perforations. 13. A device according to any one of the claims 10 - 13, wherein said device is provided with a pre- compartment, wherein means are present for pre-opening said composites . 14. A device according to any one of the claims 10 - 14, wherein the part of said treatment space (11) between the supply means (10) for the treating agent and the discharge means (14) has a conical shape. 15. A device according to any one of the claims 10 - 14, wherein the part of said treatment space (11) between the supply means (10) for the treating agent and the discharge means (14) has a conical shape.

Inventors: DE JAGER GUI GERARD, DE JAGER, GUI, GERARD
Applicants: FLEX PATENT S A, JAGER GUI GERARD DE, DE JAGER, GUI, GERARD, FLEX PATENT S.A.
Application year: 1999
Main classification: B29B15
IPC codes: B29B15, D06B1