Method for the manufacture of a composite of continuous fibres and plastic

The invention relates to a method for the manufacture of a composite of continuous fibers ( 11 ) and plastic. The fibers are present as a unidirectional fiber arrangement ( 1 ) or in the form of strand-like, multi-fibrous threads ( 1 ), with these threads forming a textile thread arrangement ( 10 ), in particular a fabric or braided fabric. The fibers are embedded into a plastic matrix, wherein a polymer or different polymers are provided for the manufacture of the matrix. The fiber arrangement or thread arrangement ( 1, 10 ) is draw off from a supply point, in particular a supply reel ( 100 ), and impregnated with particles of plastic, with subsequently at least a part of the particles being converted by melting into the matrix. A mean diameter of the particles is not substantially larger than the diameter of the fibers ( 11 ). The fiber arrangement or thread arrangement ( 1, 10 ) is transported without deflecting elements and guided in one plane. The particles are sprayed onto the fiber arrangement or thread arrangement suspended in a liquid and the liquid of the sprayed suspension ( 30 ) is removed by means of evaporation in a drying step ( 51 ) prior to conversion melting ( 52 ).

The fabric 10 shown in FIG. 1 consists of threads 1 which are strands of unidirectionally arranged continuous threads 11 . This fabric 10 , a different textile thread arrangement or an unwoven fibre arrangement 1 can be treated in an apparatus 2 of FIG. 2 in accordance with the method in accordance with the invention. The fibre arrangement or thread arrangement 1 , 10 is drawn off from a supply reel 100 (or supply point) and treated in the apparatus 2 while using diverse process steps. The transportation, in which the fibre arrangement or thread arrangement 1 , 10 is guided in one plane, takes place without deflecting elements so that no irregular displacements of the threads result during the treatment of a textile arrangement. The impregnation is no longer carried out in a bath, but in a spray device 3 by means of nozzles 31 , 32 , with which a suspension 30 containing the plastic particles is sprayed onto the fibre arrangement or thread arrangement 1 , 10 . The fibre arrangement or thread arrangement 1 , 10 is transported horizontally in the example shown, with the suspension 30 being sprayed from the top by nozzles 31 and from the bottom by nozzles 32 . It is also possible, but less advantageous, to spray only from the top or only from the bottom. Suspension 30 , which is not picked up or held by the fibre arrangement or thread arrangement 1 , 10 , is collected in a tank 33 and fed into a reservoir 6 from there. A pump 60 continuously transports suspension 30 from this reservoir 6 into the nozzles 31 and 32 . The upper rims 34 of the tank 33 can be formed as guide members for the fibre arrangement or thread arrangement 1 , 10 . The treatment is continued subsequent to the spraying on in a part device 5 using known process steps. The liquid of the sprayed suspension—as a rule water—is removed by evaporation in a drying step carried out in a first stove 51 , a tunnel stove. At least a part of the plastic particles taken up is converted my melting into the matrix of the composite to be manufactured in a second stove 52 . The fibre arrangement or thread arrangement 1 , 10 is drawn through the apparatus 2 by means of a transportation device 50 . In this method in accordance with the invention and in contrast to the previously known methods, it can be accurately determined how much plastic is applied when the quantity of suspension 30 sprayed and held on the fibre arrangement or thread arrangement 1 , 10 is measured. Therefore no regulation is provided and no special operating state has to be observed either. The fibre arrangement or thread arrangement 1 , 10 is advantageously heated in a tunnel stove 4 prior to the spraying on of the suspension 30 . The capability of the thread arrangement 1 to accept the suspension 30 is improved in this process step. A first reason for this improvement is the fact that—see FIG. 3 —the air located in spaces 13 of the thread arrangement 1 is cooled during spraying on (arrows 30 ′), with the air pressure reducing there, which effects a suction (arrows 14 ) of the suspension 30 into the spaces 13 . For this effect to actually take place, the fibre arrangement or thread arrangement 1 , 10 must be sprayed from both sides. There can be a second reason for the improvement in the receiving capability which is even more effective when favourable circumstances prevail. This reason consists, for example, of the fact that water is adsorbed on or in the fibres 11 of the fibre arrangement or thread arrangement 1 , 10 . The water is desorbed during the heating in the stove 4 and thereby displaces—see FIG. 3 —air from the spaces 13 of the fibre arrangement 1 . During the spraying on 30′ of the suspension 30 and the cooling associated therewith, the desorbed water condenses again which results in a suction of the suspension 30 into the spaces 13 . Adsorbed water can be contained in a size 12 with which the fibres 11 are coated. Fibres coated with sizes 12 are often used to improve the wettability with the plastic melt during the forming of the matrix. The fibres 11 are heated by means of the stove 4 during heating to a temperature at which the size 12 remains intact or largely intact. (Depending on the size, heating can be up to 120° C. or also higher, up to 300° C.). As a rule, hydrophilic components are contained in the sizes 12 , thanks to which water is also actually contained in the fibres 11 . The coating formed with the size 12 is usually not so wettable for water so that the dispersion 30 sprayed on does not penetrate the fibre arrangement 1 due to capillary forces alone. The fibres 11 of the fibre arrangement or thread arrangement 1 , 10 can be in a state during the drawing off from the supply point in which the substance which is used as the liquid for the suspension is present in adsorbed form. The fibres can naturally also only be brought into such a state by wetting after the drawing off from the supply point 100 , with also a relatively high amount of the liquid being applied to the fibre arrangement or thread arrangement 1 , 10 so that the fibres 1 carry liquid films on their surfaces. Powder-like thermoplasts are used as polymers for the plastic matrix. These can have powders of thermosetting plastics and/or anorganic materials added to them in small quantities. The process steps of heating, spraying on and drying can be repeated after the drying step in the stove 51 in order to increase the quantity of plastic taken up. This can also be repeated manifold times before the method is completed with the melting of the plastic in the stove 52 .