EP0000755A1 - Method and apparatus for making a shaped body from reinforced plastic - Google Patents

Abstract

The invention relates to a method for producing molded articles from reinforced plastic and a device for carrying out the method. A body consisting of reinforcing material (fiber strands) is covered before or after its soaking with the plastic by a liquid which forms the female or male in situ and is removed after the plastic has gelled or hardened. The device has a container (22) for the bodies (1) made of reinforcing material, which is provided with lines for supplying and removing the plastic (3) and can be placed under vacuum and / or overpressure. The end faces of the bodies (1) can be inserted into recesses in plates (24, 25), which are provided with perforations (26, 26 ') there for supplying plastic (3) to the bodies (1). The plates (24, 25) are inserted tightly into the container (22). A supply line for the coating liquid opens into the space between the plates (24, 25) and the walls of the container (22) in which the bodies (1) are located.

Description

Body from e.g. curable plastic, such as polyester, epoxy resin or the like, which with e.g. Fibers or fabric structures are reinforced either by the so-called wet process, or by the so-called dry process. In the wet process, the fibers impregnated with the hardenable plastic are e.g. in the case of fiber strands (rovings) wound on a mold core, in the case of staple fibers, sprayed on a mold wall, in the case of fabric structures placed on the mold wall and then compressed by rolling on or freed of any air bubbles. However, the compression or freedom from air bubbles that can be achieved is limited and uncontrollable, so that a constant quality cannot be achieved.

In the dry process, the fibers are first brought into the desired shape, for example wound on a mandrel, and then soaked with the plastic. To achieve a particularly good compression or. Freedom from air bubbles has become known for inserting such a fiber wrap sitting on a male part (mold core) into a female mold (mold), first evacuating it, then filling it with the plastic, which - possibly even under pressure - into the mold to press and harden. Although air-bubble-free and highly compressed moldings are largely achieved, the amount of mold required is considerable: not only does everyone have to Form vacuum- and pressure-tight, as well as with supply and discharge lines, but it is also occupied by the curing time of the plastic considerable time. As a rule, a large number of expensive molds must be purchased for industrial production.

The present invention has therefore set itself the goal of providing a method and a device with the aid of which molded articles made of e.g. fiber-reinforced plastics can be manufactured relatively cheaply and still reproducibly in the highest quality. This is achieved according to the invention in that the reinforcing material formed into a body is covered before or after its impregnation with the plastic, at least on the outside, by an in situ liquid which forms the matrix or patrix, which possibly solidifies and again after the plastic has cured or cured Will get removed.

As a result of this measure, the mold is formed from a material that can be used again and again and can - if necessary - be converted into the solid state, so that it withstands the vacuum and / or pressure to be used. The liquid inevitably and automatically attaches itself to any form of reinforcement, no matter how complicated, and envelops it completely and seamlessly. Therefore, the otherwise necessary maintenance of the very expensive, tolerance-dependent, divided impregnation molds (matrices / patrices) of a traditional type is also omitted. In the process according to the invention, the finished moldings can be removed from the mold without damage as soon as they are gelled to retain their shape.

Furthermore, the close conformity of the preferably pressurized liquid molded casing, or the solid molded casing under shrinkage stress, allows a high proportion of the reinforcing materials to be accommodated in the molded body and loaded with an arbitrarily high vacuum and / or pressure and in this way to ensure complete impregnation with which the highest strength values can be achieved.

The logical sequence of the procedure according to the invention proceedings can widely used as, methods are referred to a matter conversion pressure / vacuum inje _K ti-plastic bonding method hereinafter referred to as "MTC" and allows programmable automation first industrial-scale production of all body, whatever shaping them in detail or have among each other, with consistently reproducible top quality in a closed system, which also guarantees the guarantee of healthy working conditions because the working personnel do not come into contact with vapors that are harmful to health.

According to the essence of the invention, the bodies of any kind prepared from the reinforcing material are coated undivided with a self-forming, temperature-tight and tight mold shell which is tightly and pressure-tightly attached to each shape in a solid or liquid state of aggregation, which - if it was solid - after Gelling or hardening of the shaped body can be removed again, for example by melting, dissolving or cutting open. The material of the molded cover can be used again and again.

Although various inorganic and _"organic liquids can be used for wrapping, she Unless do not respond or do not mix with him with the plastic, low melting metal alloys have SiCN but proved to be particularly useful. Not only results from its high density a particularly good Matters of the body made of the reinforcing material and penetration into relatively inaccessible undercuts and the like, which would be particularly difficult to produce according to conventional mold construction, but such an alloy can be converted into the solid state by slightly lowering the temperature, which makes it highly pressure-resistant one-piece form and thus free of parting lines is created, whereby a high degree of compaction can be achieved.

Low-melting alloys, the melting point of which is below the temperature resistance of the hardened plastic, are preferably used as the liquid for the production of the coating described. Such an alloy pillars are mostly eutectic mixtures of volatility, lead, tin, cadmium and antimony; they can be adjusted precisely to a certain desired melting point. Among bismuth-tin-lead-cadmium-indium alloys there are those with a melting point of 47 ° C. Special bismuth-lead-cadmium alloys, for example, have a melting point of 92 ° C, bismuth-tin-zinc alloys have a melting point of 130 ° C. The melting point of tin-lead-cadmium alloys is 145 ° C; a melting point of 221 ° C can be achieved with tin-silver alloys, with cadmium-antimony alloys that of 292 ° C.

To secure the position of the body made of the reinforcing material, spacers, inserts, support structures or the like can be used (for example when pouring liquid coating material over it or when immersing it in the same). made of rigid materials that are resistant to the coating material and can withstand the relevant temperature stress.

As a reinforcing material, fiber strands, staple fibers, fabrics, wires, flakes, _w hiskers and the like can be used in a manner known per se. made of plastic, glass, textile, carbon, asbestos or metal (e.g. steel, beryllium etc.). This material is applied in a manner adapted to the respective shape on a base body which is also known per se, for example by winding, spraying, electrostatic fixing or the like.

The base body can remain as a male part in the finished molded body, i.e. form a kind of lost formwork and made of - possibly 'reinforced - plastic, a suitable liner or the like. consist.

The base body can also be removed before or after the impregnation. This can be desirable if a fiber roll is designed so that it has sufficient strength for handling during the impregnation or wrapping even without the supporting base body. In this case, it can be wound on a mandrel and immediately pulled off it. As a result, only a small number of cores is required, even with complicated mold cores.

If, on the other hand, the strength of the fiber roll alone is too low, the impregnation or covering will take place on a base body which, if it is not desired in the finished molded body, is only removed after the method according to the invention has been carried out. In this case e.g. the basic body made of thin-walled plaster or glass, made of a material such as a low-melting metal alloy, wax or the like, made of evaporable foam, or possibly made of the same material as the coating liquid, which is allowed to solidify in the course of the process. The last method in particular has proven to be advantageous because the mold core is integrated into the outer mold (formed by the solidified coating liquid) and all problems that cause different expansion coefficients with different layer materials are avoided.

According to one embodiment of the invention, the body made of reinforcing material is impregnated with the plastic after it has been coated with the liquid and, if necessary, solidified through recessed inlet and outlet openings. If the body made of the reinforcing material is large-pored, it is expedient to have it on the surface before the covering with the material forming the outer shape, with the exception of inlet and outlet openings, e.g. to be provided with a pore-sealing coating by powder coating, which reliably prevents the encapsulation material from penetrating.

According to another embodiment of the invention, the body made of reinforcing material - optionally on the base body - is immersed in a bath of plastic and soaked; the excess plastic is then displaced by the coating liquid, the soaked molded body is gelled or cured and the coating is then removed again. The bodies made of reinforcing material are preferably placed under vacuum before immersion in the bath and / or after immersion in the bath - for example for a few minutes - under a pressure which was previously higher (for example 10 bar and above), if the body used is formed utoklav as _A. For comparatively much lower pressures, very elaborate mold designs had to be chosen so far.

• Fig. 1 einen schematischen Vertikalschnitt mit erstarrtem überzugsmaterial in einem Formraum;
• Fig. 2 einen schematischen Vertikalschnitt durch einen verschließbaren Behälter mit Aufnahmeplatten als Abstandhalter, in welchen Zuführungsöffnungen für die Vakuum/Druckbeaufschlagung und Harzzu- und Harzabfuhr für beliebig viele Körper aus Verstärkungsmaterial entsprechend ihrer Form angeordnet sind,
• Fig. 3 eine Aufnahmeplatte im Teilschnitt mit zwei eingezeichneten Körpern aus Verstärkungsmaterial (Rohrbügen 90°) in Vorderansicht ungeschnitten,
• Fig. 4 einen schematischen Vertikalschnitt durch einen temperaturgeregelten verschließbaren Behälter (Autoklav)mit erfindungsgemäß zu behandelnden Körpern aus Verstärkungsmaterial in Überzugsmaterial, das in flüssiger Phase gehalten ist, und die
• Fig. 5 und 6 eine erfindungsgemäße Vorrichtung in Trommelform im Längsschnitt in Ausgangslage bzw. um 180° demgegenüber verdreht.

The method according to the invention is explained in more detail below with reference to the drawing, which illustrates exemplary embodiments of devices according to the invention for carrying out the method. It shows: the

• 1 shows a schematic vertical section with solidified coating material in a molding space;
• 2 shows a schematic vertical section through a closable container with receiving plates as a spacer, in which supply openings for the vacuum / pressurization and resin supply and resin removal for any number of bodies made of reinforcing material are arranged according to their shape,
• 3 a receiving plate in partial section with two drawn bodies made of reinforcing material (pipe bends 90 °) in the front view uncut,
• Fig. 4 is a schematic vertical section through a temperature-controlled lockable container (autoclave) with bodies to be treated according to the invention made of reinforcing material in coating material, which is kept in the liquid phase, and
• 5 and 6 a device according to the invention in drum form in longitudinal section in the starting position or rotated by 180 ° in contrast.

The procedure (explained with reference to FIGS. 4-6) is carried out by first degassing the containers 7 and 22 together with their contents via a vacuum pump (not shown); the resin 3 is then allowed to flow in via a feed line, which may be common for many bodies 1 'made of reinforcing material, until it is visible in a sight glass (not shown) on the container 7. For better impregnation, the bodies 1 'made of reinforcing material are optionally kept under positive pressure until the resin 3 gels.

FIG. 1 shows a body 1 made of reinforcing mats cast in by cooling in a metallically solidified phase rial in the form of a fitting which is provided with connecting pieces 2 (funnels) placed on the end face for the supply and discharge of the impregnating resin 3. A solid casting jacket 4 takes up the body 1, which in its interior still has the base body 5, together with its connecting pieces 2 and then the liquid cast coating material, which forms the mold shell 6 after solidification in the casting jacket 4. The base body 5 can consist of solid, liquefiable or gasifiable material.

Using a device shown in FIGS. 2 and 3, reinforced plastic bodies can be produced as follows:

The procedure is demonstrated using an elbow, for example. The body 1 consisting of the reinforcing material is first used together with the base body 5 (core) in two plates 24 and 25. These plates have feed and discharge openings 26 and 26 'which lead through the plates 24, 25 to the two end faces of the body 1 consisting of the reinforcing material. As soon as the bodies 1 made of the reinforcement material are inserted into the plates 24 and 25, the plates are inserted into the vessel 22 and this vessel is then closed with a lid 23. The wrapping material 6 is then introduced into the vessel via a valve 14. The air escapes via a line 14 '. Then the impregnation material 3 is introduced through the cover 23 via a valve 8 and passes through the openings 26 in the plate 24 to the end face of the body 1 made of reinforcing material, passes through it and exits again through openings 26 'in the plate 25 and enters a space 25 'from where it can be withdrawn via a valve 20. As soon as the impregnation material has gelled or hardened, as long as the covering material 6 has been kept in a liquid state, this material can be drawn off via the valve 21. However, if the wrapping material was in a solid state of aggregation, the now solid wrapping material 6 together with the plates 24 and 25 and the cast-in, now already soaked bodies made of reinforcement Kungsmaterial 1 removed from the container 22 and the wrapping material 6 melted or otherwise removed (such as by smashing if it is glass-like material), which then the body 1 are free.

The base body 5 can also be melted out or removed from the interior of the pipe bend by gasification, depending on the material from which it is made.

In Fig. 3, the receiving plate 24 is shown with two bodies 1 made of reinforcing material used there. However, any number of bodies made of reinforcing material can also be inserted into a receiving plate 24.

According to FIG. 4, the method proceeds as follows: The bodies 1 'made of reinforcing material are placed in a vacuum and pressure-tight container 7 on a lower grate 17 and covered with a further grate 19. After sealing the container 7, the negative pressure valve 12 is used to Ent ^g a-solution of the container contents, in particular the body of reinforcing material is opened. After reaching the defined negative pressure, the valve 12 is closed and the valve 8 is opened, after which the plastic 3 located in the reservoir 9 has been degassed via the valve 10. Bubble-free plastic mass thus pours into the container 7 via the reinforcing body 1 'up to the level of the grate 19 or the plastic drain valve 20. After the valve 8 is closed, the pressure valve 11 is opened and the impregnating liquid in the container is pressurized , which optimizes the uniform impregnation of the body from the reinforcing material. After the pressure has been maintained for about 3-5 imin, the valve 11 is closed again and the container 7 is vented, for example via the valve 20. The valve 14 is now opened and liquid metal 16 is let out of the vessel 15 into the container 7, which forces the plastic therein, unless it has already impregnated the body 1 'made of reinforcing material, via the valve 20 to the outside. The grating 19 prevents the soaked body 1 'from floating. The metal 16 will also rise to the height of the grate 19 ge to let. After closing the valves 14 and 20, the hardening of the plastic (impregnating material) remaining in the reinforcing bodies begins by the heat stored in the liquid metal 16, and optionally by a jacket heater 13 of the container 7. After the impregnating material has hardened, the liquid metal 16 becomes solid the valve 21 is drained again from the container 7, the container 7 is opened, and the now finished molded articles are removed.

In the embodiment according to FIGS. 5 and 6, the closable vessel 22 is designed as a drum. This drum is about an axis 23 at least by 180 ⁰ pivotable. There is a support grate 17 in the drum, which extends in the longitudinal direction of the drum, that is to say in the direction of its pivot axis. The bodies 1 'to be soaked from reinforcing material are placed on the support grid 17 or, if necessary, held by supports or on thorns. A low-melting alloy 16 is located under the support grid 17. A vacuum line 12, an overpressure line 11 and a line which can be shut off by a valve 8 and which lead to the storage vessel 9 open into the jacket of the drum 22 at locations which are free of the alloy 16 for the curable plastic 3 leads. A conduit 20 leads from the drum through the hollow axis, which can be closed and via which, after the drum has been turned, the plastic can be pulled off from the position shown in FIG. 6 by 180 ° and fed back to the storage vessel 9. The method according to the invention can be carried out as follows using a device as shown in FIG. 5:

Before loading, the drum 22 is brought into a position in which the coating liquid 16 is located below the rack 17 (FIG. 5). The bodies 1 'are then introduced into the interior via an opening in the drum and placed on the grate 17. After opening the drum 22, the interior of the drum 22 is connected to vacuum and the air by opening the line 12 depilated from the interior and from the bodies 1 'made of reinforcing material. After the degassing, the vacuum line 12 is closed and plastic 3 is introduced into the drum 22 from the storage vessel 9 via the opened valve 8 until the bodies 1 'are covered, ie until the level of the plastic supplied is higher than the highest point all the body 1 'deposited on the grate 17. After this state has been reached, the valve 8 is closed and excess pressure is supplied to the interior of the drum via the line 11. As a result, the reinforcing material is particularly saturated with the plastic material. The overpressure line 11 can then be closed, whereupon the drum 22 is turned through 180 ° from the position shown in FIG. 5. The bodies 1 'immediately rise up to rest against the grate 17 (FIG. 6) and the resin (impregnation material) is suddenly displaced by the liquid material 16 in the drum 22, which is of higher density than the plastic. The plastic is discharged via the line 20 and - as already mentioned - returned to the container 9 for the resin 3. The resin-impregnated body 1 'are entirely surrounded by the high-density material 16 and the plastic in the body 1' can gel or harden, if necessary with the addition of heat, namely with the addition of ultraviolet radiation, or also using microwave energy and the like . After the plastic has hardened or has reached a gel stage, the drum 22 is turned back into the position shown in FIG. 5. The material 16, which has a higher density than the plastic, is again located below the support grate 17 and the bodies 1 'which are now completely free can be removed from the grate and removed from the drum 22.

A two-function valve 21 is arranged on the drum 22 according to FIGS. 5 and 6. Able according to Fi ^g . 6 it serves to ventilate the interior of the drum during emptying, but in the position according to FIG. 5 for the removal of the liquid material 16.

Claims (14)

1. A process for the production of molded articles made of reinforced plastic, in which a prepared body made of reinforcing material is impregnated with plastic, characterized in that the body consisting of the reinforcing material before or after its impregnation with the plastic at least externally from an in situ die or The patrix-forming liquid is encased, which is allowed to solidify if necessary and is removed again after the plastic has cured or hardened. 2. The method according to claim 1, characterized in that the body is encased seamlessly from the reinforcing material. 3. The method according to claim 1 or 2, characterized in that the body of the reinforcing material is encased by a low-melting, esp. Eutectic metal alloy. 4. The method according to any one of the preceding claims, in which the body is formed from the reinforcing material on a base body (mandrel, mandrel, male), characterized in that the body is separated from the base body before the impregnation or wrapping. 5. The method according to any one of claims 1 to 3, in which the body made of reinforcing material is formed on a base body (mandrel, mandrel, male), characterized in that the composite consisting of the base body and the reinforcing material is cast with the coating liquid and thereby the the existing body is soaked. 6. The method according to claim 5, characterized in that such a base body is used, which consists of the same material as the coating liquid. 7. The method according to any one of the preceding claims, characterized in that the impregnation takes place under vacuum and / or overpressure conditions. 8. The method according to any one of the preceding claims, characterized in that the body made of reinforcing material is coated with the liquid, whereupon - if necessary after it has solidified - the plastic is impregnated through recessed inlet and outlet openings. 9. The method according to claim 8, characterized in that the body of reinforcing material is provided on its surface with the recess of inlet and outlet openings before the covering with a pore-closing coating. 10. The method according to any one of claims 1 to 7, characterized in that the body made of reinforcing material - optionally on the base body - is immersed in a bath of a plastic and soaked, and that then the excess plastic is displaced by the coating liquid and the soaked molded body during it is enclosed by the coating liquid, is gelled or cured, after which the coating liquid is removed again. ll. Apparatus for carrying out the method according to claim 10, characterized in that in a container (7) which can be placed under vacuum and / or pressure, if appropriate, one supply and discharge line (8, 20) for the plastic and one supply and discharge line each is arranged for the coating liquid (16). 12. The apparatus for carrying out the method according to claim 10, characterized in that the container (22) which can be placed under vacuum and / or pressure is designed as a vessel which can be swiveled at least by 180 ° about its longitudinal axis and in which the coating liquid (16) remains and the container (22) each having an inlet and outlet line (8, 20) for the plastic (3) (FIGS. 5, 6). 13. The apparatus according to claim 11 or 12, characterized in that in the interior of the container (7) a grid (17) od.dgi. to prevent the floating of the shaped body (1 ') is arranged. 14. Device for carrying out the method according to claim 8 or 9, characterized in that with inlet and outlet openings for the plastic on the surface of the reinforcing body (1) connected connecting pieces (2), for example funnels, connecting pieces or receiving centering plates, 0000755 are seen, which are supplied by a common supply and discharge line for the plastic or for vacuum / pressure (Fig. 1, 2).

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