Process and device for coinjection molding multilayer products

Abstract

Multilayer products, such as vehicle trim panels, provided with an external skin layer and an internal core layer are co-injection molded by injecting external material (P) through a first plurality of points of injection (3a-3c) and injecting the core material (C) through a second plurality of points of injection (4a-4g), the points and nozzles of injection of one material being physically distinct from those of the other material.

Description

[0001] The present invention relates to a process and a device for co-injection molding multi-layer elements and to the products thus obtained.[0002] In particular, the invention relates to the production of elements provided with at least one part having, an external skin which covers an internal core material. Examples of such product are trim panels and trim elements of motor vehicles.[0003] To obtain products of a type similar to those described above co-injection processes are already known which provide for the sequential injection of two or more materials from a single injector nozzle. In these processes a preset amount of skin material is initially injected into the mould, followed by one injection of core material and then another injection of skin material.[0004] The European Patent N.sup.o0579925, in the name of the applicant, describes a device for co-injection molding provided with independently heated hot channels and nozzles located in the wall of the mould. The nozzl...

AI Technical Summary

Benefits of technology

[0006] It is an aim of the invention to solve the aforementioned problems and to provide a simple and economical process for co-injection molding of two or more materials to give products having at least in part an external skin and an internal core.

[0011] The invention has several advantages over known processes. Lower injection pressures are required, therefore smaller and less expensive presses can be used. Also, the molding-cycle time is shorter than in prior art. Furthermore, junction lines between the flows of materials are avoided and the mould can have substantially constant thickness for the greater part of its extent, if this does not conflict with the design requirements. The constant thickness results in greater facility of design and less weight in the finished product.

[0012] Another advantage lies in being able to produce the fixing elements to assemble the panels onto the doors and the counter-panels or complementary panels (retainers and studs) out of core material alone, i.e. with a rigid material. Thus, very soft materials can be chosen for the skin layer, improving the `feel` of the finished product.

Problems solved by technology

However, these processes require high injection pressures, which in turn mean large presses, flash on the molding, materials that are particularly fluid, or a greater thickness of moulds, with their related costs.

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