Method for manufacturing a polyurethane-flooded plastic component

Abstract

A method for producing a polyurethane-flooded plastic component, wherein the plastic component is manufactured by back-injection of a plastic film (1), characterized in that the plastic film (1) is introduced into the mold cavity of a flooding tool (22) so that the plastic film (1) seals the chamber (11) of the mold cavity of the flooding tool in a polyurethane-tight manner, that the polyurethane (18) is introduced into the chamber (11) of the mold cavity in a shot, whereby the plastic film is flooded with polyurethane (18), and that the flooded plastic film (1) is inserted as an intermediate product (12) into a back-injection tool (15) and is back-injected with a plastic (16) on the non-flooded side.

Description

The invention relates to a method for producing a polyurethane-flooded plastic component, wherein the plastic component is manufactured by back-injection of a plastic film. It is known to coat plastic components, such as a plastic film back-injected with a plastic, with polyurethane. However, according to the current state of plastics technology, sealing over metal surfaces within injection molds is not possible because the coating material is very low viscosity and therefore flows into even the finest gaps. This results in burrs on the edges of the plastic components, which must be removed in an additional processing step. A generic process is known from publication WO 2005 / 070 647 A1. This document discloses a process for producing decorative plastic composites with a decorative layer, a substrate layer, and a clear outer layer that offers high image depth. Decorative or protective applications with decorative patterns can be formed by injection molding a substrate layer and a clear outer layer onto the top surface of a thin foil, film, fabric, or veneer. In the process described in WO 2005 / 070 647 A1, the application of the carrier layer and the outer layer takes place in the same tool, with the tool walls being shifted relative to each other between these steps. When coating the decorative layer with a low-viscosity polyurethane, the aforementioned sealing problems are to be expected. Document CH 705 064 A1 describes a method for manufacturing a multifunctional unit with a rigid support structure, in which operating elements and / or display elements are arranged behind a transparent surface layer that extends substantially over the entire unit. The method comprises punching a positioning hole in a transparent plastic film; positioning the film in an injection mold using the positioning hole; back-injecting the film to form a plastic support on the first side, the injection mold being designed such that the plastic film is not back-injected at the operating and / or display elements; and flooding with a transparent, curing potting compound to form a continuous transparent surface layer on the second side. The task therefore arose to create a process that offers the possibility of flooding a plastic film while simultaneously solving the aforementioned sealing problem. This problem is solved according to the invention by a method for producing a polyurethane-flooded plastic component according to claim 1. According to the invention, it is provided that plastic components are produced as flooded and back-injected plastic film, which is flooded with polyurethane in one process step and back-injected with a thermoplastic plastic in a further process step. For the first process step, the flooding tool has a mold cavity that is covered by a polyurethane-tight plastic film. In a subsequent process step, the flooded plastic film is placed as an intermediate product into an injection mold and back-injected with a thermoplastic material. Details of this process are outlined and explained in more detail below with reference to the drawing. Figure 1 shows a plastic film 1, which is manufactured in one piece and preferably die-cut from a film web (not shown). The plastic film 1 is intended to later form the surface of a plastic component, preferably a control element. The plastic film 1 has been pre-printed with a design 20 that identifies the function of the control element to be manufactured. To protect this design 20 and to create a high-quality look and feel, this surface is coated with polyurethane. Figure 1 shows an example of a possible configuration of the plastic film 1, with edge sections 4 and end sections 2 and 3 of the plastic film 1 shown as black areas. This coloring is only intended to clarify the aforementioned areas of the plastic film 1; in reality, the entire plastic film 1, apart from the printing 20 mentioned, consists of a uniform film material. Figures 2, 3, 4, 5 to 6 each show a sketchy cross-sectional view of a possible flooding tool 22 for flooding a plastic film 1 with polyurethane. Visible are a lower tool part 9, an upper tool part 8, sealing areas 10 in which a particularly pressure-resistant sealing element made of metal, plastic or silicone is located, and a cross-section of a connecting channel 5 in a wall 21 within the chamber 11 of the flooding tool 22. The plastic film 1 is either inserted into the upper part of the tool 8 as shown in Fig. 2 or placed on the lower part of the tool 9, whereby the plastic film 1 shown in Fig. 1 seals the opening of the chamber 11 in a polyurethane-tight manner. By joining the upper tool part 8 and the lower tool part 9 (Fig. 3), the flooding tool 22 closes, thereby also bringing the sealing areas 10 into contact with the edge sections 4 of the plastic film 1. The upper tool part 8 can have molded-on fine wedge structures (not shown here) that are pressed into the plastic film 1, thus creating a positive fit. This seals the chamber 11 to such an extent that even low-viscosity fluids can no longer escape. Only the material injection and overflow openings, which are not shown in the figures, remain open. Fig. 4 shows a longitudinal section B - B of Fig. 1 through the flooding tool 22 along the connecting channels 5 to injection and overflow chambers 6, 7. The polyurethane 18, intended as flooding material, is injected into chamber 11 in one shot and hardens there after a predetermined residence time (Fig. 5). After opening the flooding tool 22, shown in Fig. 6, the flooded plastic film 1 can be removed as an intermediate product 12. In the next process step, which is illustrated in Fig. 7, the flooded plastic film 12 is placed into an injection mold 15, consisting of a cavity mold 13 and a hollow mold 23. The hollow mold 23 can, in particular, have recesses 14 for forming, especially guide elements, holders, connections, or the like. These serve for the subsequent attachment of the operating element to be manufactured, for example, to an electrical switch. Once the back-injection tool 15 is closed, as shown in Fig. 8, a plastic 16 is injected into the cavity 19 via a gating system (not shown) (Fig. 9). When this process step is complete, the flooded and back-injected plastic component, designed as a film composite part 17, can be removed (Fig. 10). Reference sign 1 Plastic film 2 End section 3 End section 4 Edge sections 5 Connecting channels 6 Injection chamber 7 Overflow chamber 8 Upper mold part 9 Lower mold part 10 Sealing areas 11 Chamber 12 Flooded plastic film (intermediate product) 13 Cavity shape 14 Recesses 15 Back injection mold 16 Plastic 17 Film composite part 18 Polyurethane 19 Cavity 20 Printing 21 Wall 22 Flooding mold 23 Hollow shape

Claims

A method for producing a polyurethane-flooded plastic component, wherein the plastic component is manufactured by back-injection of a plastic film (1), characterized in that the plastic film (1) is introduced into the mold cavity of a flooding tool (22) so that the plastic film (1) seals the chamber (11) of the mold cavity of the flooding tool in a polyurethane-tight manner, that the polyurethane (18) is introduced into the chamber (11) of the mold cavity in a shot, whereby the plastic film is flooded with polyurethane (18), and that the flooded plastic film (1) is inserted as an intermediate product (12) into a back-injection tool (15) and is back-injected with a plastic (16) on the non-flooded side. Method according to claim 1, characterized in that the plastic film (1) is provided with a print (20) before being flooded.

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