DE102005024175A1 - Molded plastics body with an inner porous core, for motor vehicle interior fittings, is molded from a co-extruded mass with an inner layer containing a foaming agent to expand the core after extrusion and before mold closing - Google Patents

Abstract

To produce a molded plastics body with a porous core, the mass is co-extruded intermittently with a tubular outer skin and an inner layer containing a foaming agent. The mass is passed into a multi-part mold (10) with cavities of a different cross section profile. The foaming agent expands the core after extrusion and before mold closing so that the outer skin is pressed against the mold surfaces. The inner core is expanded by inflation and/or spread across its longitudinal axis.

Description

The The invention relates to a method for producing a porous Core area having plastic molding, in particular a trunk floor or an underbody paneling of a motor vehicle.

From the DE 100 01 932 A1 is a cladding element, namely a Unterbodenabdeckplatte for a motor vehicle known. The cladding element is produced as a double-walled hollow body with a plurality of cassette-like cavities communicating with each other via channels by extrusion blow molding. The cavities are filled with a closed-cell foam in the form of so-called polypropylene mini-beads. To produce the trim part, an extruded preform is inflated after closing the blow molding tool. After this expansion process is completed, the pressure in the hollow body is lowered to inject the plastic beads into the cassette-shaped cavities. The supply of the plastic beads via a hose which terminates within the cavity of the blow mold and whose end is formed so that the interior of the hollow body to be produced from the preform can be connected to the hose. The blow molding tool is also provided with hollow needles, which protrude beyond the boundary of the cavity in this, so that no later than the expansion of the preform whose wall in the region of the cassette-like cavities is pierced by the hollow needles. Each of the hollow needles is connected with the interposition of a valve with a vacuum source.

From the DE 196 00 847 A1 a method for producing a molded part made of thermoplastic material is known, in which produced by a discontinuous extrusion process, a tubular preform having a formed of different layers, of which at least one layer of a foamable plastic wall, formed in a split mold and after the Close the same is brought to the wall to the concern. This known method is characterized in that the preform is fed without pressure to the mold and that the foaming process of the foamable layer of the wall of the preform takes place substantially in the closed mold. For this purpose, a foam delay is added to the foamable plastic.

Of the The present invention is based on the object, a method specify with the plastic moldings, which each have a porous Core area and a changing, i. non-uniform cross-sectional profile have, in particular trunk floors or underbody panels a motor vehicle, inexpensive can be produced.

These The object is achieved by a method having the features of the claim 1 solved.

at the method according to the invention become intermittently a non-foamed, tubular outer layer and a propellant, tubular inner layer coextruded, wherein the co-extruded, touching ones Layers as plastic molding compound in a multi-part mold, its cavity a non-uniform Cross-sectional profile has to be introduced, the mold is closed and introduced into the mold layers from the extrusion die emerging plastic molding compound to be separated. According to the invention Propellant chosen so and / or set that the inner layer already after its extrusion and before closing of the mold expands, the plastically deformable outer layer through the expanding inner layer against the inner wall of the cavity of the closed Mold is pressed and the material of the expanded porous Inner layer of the outer layer substantially completely fills the limited cavity. The tubular layers be there before closing of the mold widened by inflation and / or by spreading transverse to its longitudinal axis stretched. After curing the Plastic molding compound, the mold is then opened and taken from the plastic molding.

With the method according to the invention can be in an effective and cost-effective way plastic moldings as foamed Sandwich structures with porous core area and changing cross-sectional profile produce. The layers of plastic molded parts (sandwich structures) are each in "one Shot "coextruded. It is a one-shot process, with the porous material of the expanding inner layer finally the of the unfoamed, tubular outer layer Completed limited cavity of the molding completely.

in the Contrary to the methods mentioned above The prior art is in the inventive method a piercing or inflation of the extruded preform within the closed mold is not required and not intended.

at the method according to the invention is preferably the plastic of the expanding inner layer no foaming retarder added. The foaming process rather begins after the extrusion and before the closing of the Mold. By dispensing with a foam delay and the early Start of the foaming process result in lower material costs and shorter production times.

Regarding the production of relatively large area, plate-shaped Components such as e.g. Trunk loading floors, it is advantageous that the coextruded, tubular ones Layers according to the invention before Shut down of the mold widened by inflation and / or by spreading transverse to its longitudinal axis be stretched. By inflating or stretching can be the unfoamed outer layer with relatively thinner Wall thickness achieve.

The according to the inventive method manufactured automotive components, such as e.g. Underbody panels for reducing the flow resistance and trunk loading floors, draw opposite usual Sandwich structures whose layers are interposed by means of Adhesive layers are connected by a higher stability or inherent rigidity at the same or even lower weight.

A preferred embodiment of the method according to the invention consists in that the tubular ones Laying layers in the inflated state introduced into the mold become.

Further preferred and advantageous embodiments of the method according to the invention are in the subclaims specified.

following the invention will be described with reference to a several embodiments illustrative drawing explained in more detail. It show schematically:

1 a plant for the production of plastic moldings, which have a porous core area and a different cross-sectional profile;

2 a perspective view of a trunk loading floor of a motor vehicle in a sectional view;

3 a cross-sectional view of a molded part produced by the process according to the invention; and

4 a cross-sectional view of another molded article produced by the process according to the invention.

In the 1 schematically illustrated plant has a coextrusion head 1 on where a first extruder 2 and a second extruder 3 are connected. As is well known, the filling zone of the respective extruder via a hopper 4 . 5 Plastic granules fed in a plasticizing and homogenizing zone of the extruder 2 . 3 is melted.

Inside the hollow coextrusion head 1 is a vertically adjustable mandrel 6 arranged. The coextrusion head 1 includes a conical ejection zone, wherein the mandrel 6 is also conical at its lower end. By a vertical adjustment of the thorn 6 relative to the ejection zone of the coextrusion head 1 can be the gap of the annular extrusion die 7 change or continuously adjust.

The melt streams of the two extruders 2 . 3 be in the coextrusion head 1 merged so that at the extrusion die 7 a two-layer preform 8th exit. The outer layer of the tubular preform 8th forming melt stream is produced from thermoplastic without blowing agent, so that an unfoamed outer tube 8.1 results. The the inner layer of the preform 8th forming melt stream is also produced from thermoplastic material, however, a blowing agent is added to this melt stream, so that there is a foam structure having an inner tube 8.2 results. The addition of the blowing agent takes place in the extrusion head 1 and / or in the extruder 3 ,

The two layers 8.1 and 8.2 of the tubular preform 8th are preferably made of similar types of plastics. The plastic moldings produced by the process according to the invention can then be recycled in a simple way sorted. Both layers 8.1 . 8.2 of the preform 8th are preferably made of polypropylene. If necessary, the plastic used can also contain glass fibers for reinforcement.

The tubular preform 8th is thus made of a non-foamed outer layer 8.1 and an expanding inner layer 8.2 built, with the inside of the outer layer 8.1 full surface on the outside of the inner layer 8.2 is present in order to produce a cohesive composite so far.

Below the coextrusion head 1 is arranged a multi-part mold whose cavity (mold cavity) has an alternating cross-sectional profile. The mold consists eg of two mold halves 9 . 10 movable or movable on a tool carrier 11 are arranged.

The extrusion of tubular preforms 8th occurs discontinuously, ie intermittently. The extruders 2 . 3 as well as the coextrusion head 1 are with heating elements 12 provided to assist the melting of the plastic granules and maintain the melting or plasticizing state of the plastic during the cyclical interruption of the extrusion process. It will each be a two-layer preform 8th extruded whose free-hanging length depends on the dimensions of the plastic molding to be produced.

The extrusion head 1 is with a pipeline 13 provided, where a blower 14 or a pressure source is connected. The pipeline 13 runs essentially along the longitudinal central axis of the coextrusion head 1 and flows into its discharge zone. About the pipeline 13 for a supporting air in the tubular preform 8th blown. In addition, the pipeline is used 13 an expansion of the preform 8th , For this purpose is below the extrusion head 1 a clamping device 15 arranged with which the open end of the tubular preform 8th compressed and thus can be closed. The means of the clamping device 15 closed preform 8th is inflated by inflation. This expansion takes place before closing the mold 9 . 10 , Alternatively or additionally, the tubular preform 8th before closing the mold 9 . 10 be stretched by spreading transverse to its longitudinal axis. For this example, gripping or clamping elements (not shown) may be used, which on the outside of the tubular preform 8th can attack and after grasping / pinching the preform 8th be moved away from each other.

The so expanded or stretched preform 8th gets into the open mold 9 . 10 introduced and the mold by moving together the tool halves 9 . 10 closed. The introduced into the mold plastic molding material is thereby from the extrusion die 7 detached plastic molding compound. This is done for example by the mold 9 provided cutting or crushing edges 16 ,

The propellant, which is the inner tube 8.2 plastic mass is added is selected and / or adjusted so that the unfoamed, plastically deformable outer layer 8.1 through the expanding inner layer 8.2 against the inner wall of the cavity of the closed mold 9 . 10 is pressed, wherein the material of the porous inner layer 8.2 that of the outer layer 8.1 substantially completely fills the limited cavity. The added blowing agent is preferably such that the expansion of the inner layer 8.2 immediately after exiting the extrusion die 7 starts.

It can be seen that in the left half of the tool a variety of depressions 17 are formed, which serve the generation of elevations on the plastic molded part to be produced (see. 3 and 4 ). Instead of several separate wells 17 can in the tool half 9 Also be formed a zuhängende grid-like depression.

It can also be seen that the two tool halves 9 . 10 each with a channel system 18 . 19 are provided, which opens on the inner wall of the cavity and a suction fan 20 . 21 connected. By means of the suction fan 20 . 21 and the associated channel system 18 respectively. 19 In the cavity of the closed mold, a negative pressure is generated and thus the molding of a plastic molded part from the coextruded layers 8.1 . 8.2 supported.

The application of the expanded by inflation and / or stretched by spreading preform 8th To the wall of the mold cavity thus takes place by the closing operation when closing the mold 9 . 10 , by the foam expansion and optionally by the blower by means of suction 20 . 21 caused negative pressure effect (suction effect). An inflation of the preform 8th in the closed mold 9 . 10 is not scheduled.

In the right half 10 The mold is also a hydraulically or pneumatically actuated embossing or notching element 22 integrated, which serves to produce a groove-like notch, in particular the impression of a film hinge on the plastic molding (see. 2 and 4 ).

After curing of the plastic molding compound, the mold is opened and removed the plastic molding. These are in the left half 9 of the mold, which the plurality of wells 17 has, pneumatically actuated ejection elements 23 integrated.

In 2 is a produced by the process according to the invention plastic molding 24 shown. It is in this embodiment, a trunk loading floor, the one in the floor panel 25 of a motor vehicle embossed trough 26 for receiving a spare tire 27 covers. First, it can be seen that the plastic molding 24 Transverse to the longitudinal direction L of the motor vehicle has different transverse dimensions and thus different cross-sectional profiles. Further, by the dashed lines 28 indicated that the plastic molding has two film hinges, which allow the molding section 24.1 opposite the molding section 24.2 fold up or the two molding sections 24.1 and 24.2 together with respect to the molding section 24.3 fold up. The molding sections 24.1 and 24.2 are for this purpose with grip bottles 29 Mistake.

In 3 is a produced by the process according to the invention plastic molding 24 ' illustrated in cross-section. The molding 24 ' , on the underside of a large number of surveys 30 or depressions 31 are formed, corresponds to a foamed sandwich construction. The top of the molding 24 ' is essentially smooth and well formed. It has a non-foamed cladding layer, which passes through the unfoamed outer layer 8.1 is formed. The foamed inner layer 8.2 forms the porous core region of the molding 24 ' , wherein the material of the inner layer 8.2 that of the outer layer 8.1 substantially completely fills the limited cavity.

This in 4 illustrated plastic molding 24 '' is different from the one in 3 shown plastic molding 24 ' essentially only by a film hinge 28 , which was produced by a notched in the closed mold notch.

The inventive method is not limited in its application to the production of trunk loading floors. As well can herewith also other plate-shaped Plastic moldings produced with relatively low weight and high stability be such. Underbody panels, hat racks, interior door panels and headliner of motor vehicles.

Claims (6)

Process for producing a plastic core part having a porous core region ( 24 ; 24 '; 24 '' ), in which intermittently a non-foamed, tubular outer layer ( 8.1 ) and a propellant, tubular inner layer ( 8.2 ) are coextruded, the coextruded, contacting layers ( 8.1 ; 8.2 ) as a plastic molding compound in a multi-part mold ( 9 . 10 ), whose cavity has a non-uniform cross-sectional profile, are introduced, the mold is closed and the layers introduced into the mold (FIG. 8.1 . 8.2 ) from the extrusion die ( 7 ) are separated plastic molding compound, characterized in that the blowing agent is selected and / or adjusted so that the inner layer ( 8.2 ) already expanded after its extrusion and before closing the mold, the plastically deformable outer layer ( 8.1 ) through the expanding inner layer ( 8.2 ) against the inner wall of the cavity of the closed mold ( 9 . 10 ) and the material of the expanded porous inner layer ( 8.2 ) of the outer layer ( 8.1 ) substantially completely fills the limited cavity, and that the tubular layers ( 8.1 . 8.2 ) before closing the mold ( 9 . 10 ) are expanded by inflation and / or stretched by spreading transverse to their longitudinal axis. A method according to claim 1, characterized in that by adjusting a negative pressure in the cavity of the closed mold ( 9 . 10 ) molding the plastic molding from the coextruded layers ( 8.1 ; 8.2 ) is supported. Method according to claim 1 or 2, characterized in that the molding tool ( 9 . 10 ) in the region of the cavity a plurality of depressions ( 17 ) and / or has a lattice-like depression that facilitates the creation of surveys ( 30 ) on the plastic molding ( 24 '; 24 '' serve / serve. Method according to one of claims 1 to 3, characterized in that on the plastic molded part ( 24 ; 24 '' ) at least one film hinge ( 28 ) by means of the molding tool ( 9 . 10 ) is formed. Method according to one of claims 1 to 4, characterized in that the tubular layers ( 8.1 . 8.2 ) in the inflated state in the mold ( 9 . 10 ) are introduced. Method according to one of claims 1 to 4, characterized in that the plastic molded part ( 24 ; 24 '; 24 '' ) is designed as trunk loading floor, underbody paneling or parcel shelf for a motor vehicle.