PROCESS FOR PRODUCING REINFORCED THERMOPLASTIC SHEETS AND RELATED APPARATUS

Abstract: The subject of the invention is a process for producing reinforced thermoplastic sheets wherein series of individual plastic-coated threads of reinforcement material are produced and deposited in a disorderly way in mass on a movable means, then the layer of threads (10') thus obtained is pressed or calendered. The apparatus for producing thermoplastic sheets (12) according to the above-mentioned process comprises a group of die-plates (6) that produce individual coated threads (10), a movable means (1) for receiving and transversally moving said coated threads (10) and a pressing and/or rolling means (2, 3) set downstream of said movable means (1). The disorderly arrangement takes place for at least one of the following reasons: the outlet holes of the die-plate are eccentric with respect to the axis of the single threads, water jets (1) are provided which influence the outgoing threads (10), the die-plate and/or the movable means (1) have an oscillatory movement.

Description: "PROCESS FOR PRODUCING REINFORCED THERMOPLASTIC SHEETS AND RELATED APPARATUS" The invention concerns a process for producing reinforced thermoplastic sheets, particularly sheets reinforced with long or continuous fibres. At present to produce reinforced thermoplastic sheets both sides of 5. a mat or fabric of more or less orientated or even partially woven fibres are impregnated with a polymer film, then rolled or pressed. In the most widely used plants a continuous press simultaneously melts the polymer, makes the polymer penetrate the mat, sizes the sheet and smoothes its surface. In this type of production, however, 10. problems of mat or fabric permeation by the polymer arise. In order to obtain a sheet with good characteristics the following conditions must be achieved: - the polymer must soak the fibres; - the polymer must penetrate between each fibre; 15. - the percentage of micro-gaps due to trapped air must be in the order of a few units; - high levels of fibre-polymer adhesion must be achieved; - the mat or fabric must be evenly distributed in the sheet; - it must be possible to achieve high levels of fibre content in the 20. composite (about 40%); - the fibres must be able to slide freely during the sheet forming ooerations. From US-A-3 993 726 the production of a reinforced strip is known, made of a plurality of threads impregnated with a polymer which pass through a couple of cooling rollers. The strip produced with such process has an anisotropy. 5. The object of the invention is to provide a process and an apparatus for producing, in less time than s required by traditional processes, reinforced thermoplastic sheets having good characteristics of resistance in every direction The above object has been achieved with a process m which a series 10. of individual threads of plastic-coated reinforcement material is continuously produced, said threads then being deposited in a disorderly way on a movable means thus forming a layer which will then be calendered or pressed thus obtaining a sheet of reinforced plastic material. The disorderly arrangement takes place for at 15. least one of the following reasons: the outlet holes of the die plate are eccentric with respect to the axis of the single threads; air jets are provided which influence the outgoing threads; the die plate or the movable means have an oscillatory movement. 20. If required by the composition of the sheet, provision may be made to add molten plastics at the pressing or calendering stage. Sheets of coating material can also be added. The plastics-coated threads of reinforcement material are prepared by passing the threads of reinforcement material (for example glass fibres) in die plates through which molten plastics is injected and thus surrounds said threads, embedding them in the plastics. The apparatus for producing reinforced plastic sheets with the process according to the invention comprises a group of die-plates 5. for the production of the individual coated threads, said group being disposed upstream of a movable means for receiving and removing said coated threads, while a pressing and/or sizing means is provided downstream of said movable means. A blower is placed at the exit of at least some of the d e plates, in order to ensure that 10. the threads are arranged at random on the movable means. The disorderly arrangement of the threads can be eased by the fact that the die plate has eccentric outlets with respect to the axis of the single threads produced. The movable means may be a thermostated rotating roller. In this 15. case the same roller can then cooperate with another thermostated roller forming a calendering arrangement. Preferably the die plate and/or movable means have an oscillatory movement. The proposed invention provides a material which has a uniform 20. resistance in all directions and which can therefore be pressed like a metallic sheet. The process and apparatus according to the invention will now be described on the basis of the attached drawings, in which: Fig. 1 shows a schematic side view of an apparatus for producing reinforced thermoplastic sheets, Fig. 2 shows a sectional view of an enlarged detail of the apparatus in figure 1. 5. Figure 1 shows an apparatus comprising a group 5 of die-plates that are connected to an extruder 4. Beneath the group 5 a rotating roller 1 is disposed which is in such a position as to receive, and then transversally move, the mass of plastic-coated threads 10. The roller 1 is adjacent to a second counter-rotating roller 2, which in 10. turn is also adjacent, in a substantially diametrically opposite area, to a third roller 3 rotating in the same direction as roller 1. The group 5 is made up of a series of die-plates 6 of the type illustrated in figure 2. Each die-plate comprises a tubular member 7 15. having a passage 7' that can accommodate a bare thread 9. The tubular member 7 forms a pin 7' that is surrounded by the plastics coming from a frustoconical duct 8. The plastics adhering under pressure to the thread 9 will carry it along with it creating a coated thread 10. The passage 7 ' is slightly eccentric with respect 20. to the outlet hole of the die plate. In the drawing this misalignment between the thread being produced and the outgoing thread cannot be seen, as it is very small. The group 5 produces a whole series of coated threads 10 that are deposited at random on the roller 1 (figure 1). The disorderly 25. arrangement of the coated threads 10 going out of the die-plates 6 is assisted by the presence of blower means 11, set at the exit of said die-plates 6, in order to make the paths of said threads cross. Possibly, in order to emphasize the irregular arrangement of the threads 10 an oscillatory movement of the group 5 and/or the roller 1 can be provided in the plane perpendicular to the sheet. The layer 10' composed of a plurality of threads 10 is pressed and calendered through the pairs of cooperating rollers 1 and 2 and subsequently 2 and 3. By means of this process a reinforced thermoplastic sheet 12 is produced ready for subsequent pressing into the desired shape.

Claims: CLAIMS 1. A process for producing reinforced thermoplastic sheets, in which series of individual threads (9) are individually coated, so as to produce coated threads (10), to deposit said coated threads (10) on a movable means (1), so as to form a layer (10') composed of 5. coated threads (10), and then press and/or calender the layer (10') of threads to form a sheet (12), characterized in that the arrangement of the threads takes place in a disorderly way. 2. A process according to claim 1, characterized in that the coated threads of reinforcement material (10) are obtained by 10. passing the threads (10) through a die-plate (6). 3. A process according to claim 1 or 2, characterized m that molten plastics is added at the pressing and/or calendering stage. 4. A process according to any one of claims 1 or 3, characterized in that provision is also made for adding sheet material on one or 15. both outside surfaces of the sheet (12). 5. An apparatus for producing reinforced thermoplastic sheets, comprising a group (5) of die-plates (6) for producing coated threads (10), a movable means (1), for example a rotating roller, to receive said threads (10) and move them transversally and a pressing 20. and/or sizing means (2, 3) downstream of said movable means (1), characterized in that it comprises means to cause a disorderly arrangement of the coated threads. 6. An apparatus according to claim 5, characterized in that the outlets of at least some die plates are eccentric with respect to the axis of the individual threads produced. 7. An apparatus according to claim 5 or 6, characterized in that 5. a blower (11) is placed at the exit of at least some of the die-plates (6) . 8. An apparatus according to any of claims from 5 to 7, characterized in that the die plate and/or the mobile means (1) have an oscillatory movement. 10. 9. An apparatus according to any of claims from 5 to 8, characterized in that the rotating roller (1) collaborates with at least another roller (2) to carry out a calendering operation. 10. An apparatus according to any one of the claims from 5 to 8, characterized in that the rollers (1, 2, 3) are heated and provided 15. with a thermostat.

Inventors: PESSINA AMELIA, PESSINA, AMELIA
Applicants: PESSINA AMELIA, PESSINA, AMELIA
Application year: 1988
Main classification: B29C67
IPC codes: B29B15, B29C47, B29C70