DE102010063751A1 - Process for the production of surface-processed lightweight components with high natural fiber content and integrated fasteners - Google Patents

Abstract

A method for producing a lightweight component is described, the lightweight component having a visible side and a fastening side, and wherein after inserting a natural fiber semi-finished product into an injection molding tool, this natural fiber semi-finished product is pressed and / or shaped and consolidated. The result is a molded part in the injection mold. The injection molding of fastening elements and / or reinforcing structures onto the molded part is then carried out on the fastening side of the lightweight component. This injection molding takes place in free spaces in the injection molding tool, fastening elements and / or reinforcing structures being injection molded onto only part of the surface of the fastening side. Finally, the surface component is applied in a predetermined area of the visible side of the molded part.

Description

A process for the production of lightweight components is presented, which have a high natural fiber content and a finished surface. Furthermore, an apparatus for carrying out said method will be described. Such components are preferably used in the automotive industry.

Natural fiber-reinforced plastic components (NFK components) of automotive interiors are mostly produced on the basis of flat semi-finished products, mainly by pressing. In this case, natural fiber content of over 80 wt .-%, a low material density and high structural characteristics can be achieved. Compared to the injection molding process, the design freedom of the press components with regard to local structural stiffening, z. B. by reinforcing ribs, as well as implementation of fasteners, such as retainers, very limited. In addition, the implementation of soft surfaces requires subsequent component lamination. Although the injection molding technology allows a virtually unlimited molding geometry and a surface lamination in a one-step process, however, has in the processing of natural fiber reinforced plastics significant restrictions on recoverable natural fiber content, highly dynamic structural properties and temperature-related odor emissions. Furthermore, the material density is significantly higher than that of the NFK press components.

The DE 103 27 725 A1 describes a method in which a composite component is produced by applying to the component side of a decorative layer a flowable plastic compound which is loaded with an expandable gas. The plastic mass is introduced into a mold space and the gas begins, initiated by a pressure reduction, to expand and to expand the originally single-phase plastic mass into a porous plastic foam, which completely fills the mold space.

The DE 103 41 855 A1 discloses a method of producing a component which may comprise fibers, in particular natural fibers, in an amount of up to 70% by weight. The component consists of a plastic foam, which is coated with a decorative film. The preparation takes place by using a gas-permeable decorative layer and the plastic in the mold, is foamed behind the decorative film. Excess gas can advantageously pass through the decorative film and leave the process room. The foaming of the plastic is preferably carried out by chemical foaming based on a gas-forming reaction.

In the DE 20 2007 007 498 U1 a decorative or trim part for a vehicle interior is described, which has a ductile insert. To produce the decorative layer and the ductile deposits are introduced into a mold and filled the space between the decorative layer and ductile layer with a plastic. The ductile layer should preferably consist of textile or prepreg material.

The cited prior art shows that in the automotive industry in the field of trim parts, the weight is reduced by chemical or physical foaming. However, foamed components have a more complex process control and usually lower impact resistance. A combination of advantages of the pressing, injection molding and coating technologies compared to the exclusive use of any of these technologies thus appears advantageous.

It is therefore the object of specifying a method for the efficient production of lightweight components, which makes it possible to produce a lightweight NFK component with a high degree of design freedom, an arbitrarily pronounced surface and a significantly reduced reworking effort.

The object is achieved by the method according to claim 1. Advantageous embodiments of the method are shown in the dependent claims.

The invention utilizes the advantages of the press, injection molding and coating technology by a combination of processes. The individual procedures are brought together in one process. As is particularly advantageous. to see that both standard semi-finished (natural fiber semi-finished) and with standard equipment, injection molding machine with insert, can be worked.

• a) Einlegen eines Naturfaserhalbzeugs (Halbzeug) in ein Spritzgießwerkzeug
• b) Verpressen und/oder Umformen sowie Konsolidieren des Naturfaserhalbzeugs zu einem Formteil im Spritzgießwerkzeug.
• c) Anspritzen von Befestigungselementen und/oder Verstärkungsstrukturen an das Formteil auf der Befestigungsseite des Leichtbauteils in Freiräume im Spritzgießwerkzeugs, wobei nur auf einem Teil der Fläche der Befestigungsseite Befestigungselemente und/oder Verstärkungsstrukturen angespritzt werden.
• d) Aufbringen der Oberflächenkomponente in einem vorgegebenen Bereich der Sichtseite des Formteils.

The procedure involves the following steps:

• a) inserting a natural fiber semi-finished product (semifinished product) in an injection mold
• b) pressing and / or forming and consolidating the natural fiber semi-finished product to a molded part in the injection mold.
• c) injection molding of fastening elements and / or reinforcing structures to the molded part on the mounting side of the lightweight component in free spaces in the injection mold, wherein only a portion of the surface of the fastening side fastening elements and / or reinforcing structures are molded.
• d) applying the surface component in a predetermined region of the visible side of the molding.

• – verbreitete Halbzeugausführung mit Thermoplastmatrix (Schmelzfasern) und 50 Gew.-%. Naturfaseranteil
• – Halbzeugvariante mit 100 Gew.-%. Naturfaseranteil, wobei das reaktive Matrixharz (Duroplast) erst unmittelbar vor dem Umformen auf die Matte aufgetragen (aufgesprüht) wird.

As a natural semi-finished fiber product, a textile material with a natural fiber content, which is usually mat-like, is preferably between 30% by weight and 100% by weight, particularly preferably between 40% by weight and 90% by weight. The remaining percentage is formed by fillers, such as. Granules or synthetic fibers and melt fibers. Particularly preferred here are two semifinished product variants:

• - widespread semi-finished product with thermoplastic matrix (melt fibers) and 50 wt .-%. Natural fiber content
• Semifinished product variant with 100% by weight. Natural fiber content, wherein the reactive matrix resin (thermoset) is applied (sprayed) only immediately before forming on the mat.

The method is preferably carried out in an injection molding machine, particularly preferably in a insert injection molding machine.

It is according to the invention a pretreated natural fiber semi-finished; also component 1 called, placed in a tool (injection mold) and pressed by the closing force to a molding and / or reshaped and consolidated. The molded part forms a pressed component carrier with a high degree of lightweight construction.

Subsequently, partially fasteners, such as retainers, and / or reinforcing structures, such. B. ribs, molded (also component 2 called). In a preferred embodiment, the injection molding takes place parallel to the pressing or is already started after a certain press-holding time in the tool. Pressing to a molding and injection molding then take place parallel or partially parallel.

In the next step, a surface component is applied to the composite component (also component 3 called), which receives on the visible side by an appropriate preparation of the forming tool surface any predetermined structuring (eg, leather look) and the component surface gives the desired feel (soft-touch effect) and / or high scratch resistance.

This advantageously produces a three-dimensionally shaped, surface-finished composite component with very low residual stresses and a high dimensional stability.

As natural fibers in natural semi-finished fiber materials such as wood, hemp, flax, coconut, sisal fibers, etc. or mixtures of natural fibers are preferably used. The natural fiber semi-finished product preferably has a defined melt fiber content. This melt fiber content is preferably in the range of 10 wt% to 70 wt%, and more preferably in the range of 30 wt% to 50 wt%. The melt fibers preferably have polypropylene as the melt component. In a preferred embodiment, the semi-finished product is tempered prior to insertion into the tool. For this purpose, a contact heater or a radiant heater device is preferably used. The temperature used here and the heating time depend on the composition of the natural fiber semi-finished product and, in particular, on the type and proportion of the melt component. The aim of tempering is to transfer the melt component from the solid to the liquid or semi-liquid state. This melt component is distributed evenly under pressure in the composite structure and encloses and bonds the reinforcing fibers. Upon consolidation by cooling, this melt component becomes the matrix of the composite.

In a preferred embodiment, the natural fiber semi-finished product is assembled (separated) to the required extent prior to insertion. This separation is preferably carried out by punching or trimming. In a further preferred embodiment, the tool is combined with a punching device, so that the blank of the natural fiber semi-finished product is integrated into the pressing process.

In a further preferred embodiment, thermoset-bonded natural fiber semi-finished products are used. For this purpose, the natural semi-finished fiber products are sprayed with a reaction resin (matrix resin) (preferably polyurethane) or impregnated with a curable matrix resin (polyacrylate resin) in a dipping bath (eg in the padding process) before being placed in the mold.

With the closing of the tool and application of the closing force, the natural fiber semi-finished product is shaped and pressed. The process can be accelerated by the tool preferably has additional tempering. These tempering elements are designed for processing heat-releasing matrix materials as heating elements. On the other hand, when using melt fibers of PP or other materials softening in the molten state or a surface component (TPE) consolidating by cooling, an embodiment of the tempering elements is to be provided which effect cooling.

In this way, the necessary pressing time and thus the cycle time is advantageously shortened.

The fastening elements (retainers) and reinforcing structures are molded by injecting or expanding the material of these components in free spaces in the tool. The free spaces in the tool are filled up. in the Contrary to the prior art, thus the natural fiber semi-finished product is not back-injected over the entire surface, whereby the required closing force is advantageously significantly reduced. The free spaces in the tool are already present in a preferred embodiment when forming and pressing the natural fiber semi-finished product. As a result, the region of the semifinished product to which attachment elements and / or reinforcement structures are to be fastened is advantageously not exposed to a pressing force, so that the surface of the natural fiber semifinished product remains open-pored and advantageously rough. This advantageously ensures a firm connection of the material of the retainers and / or reinforcing structures with the natural fiber semi-finished product. Due to the injection / holding pressure, the natural fiber semi-finished product is also compressed at these points. An optimal connection and low component distortion are achieved by injecting the plastic during the consolidation of natural semi-finished fiber.

In a further preferred embodiment, the free spaces in the tool are created by processing corresponding tool parts (eg a tool half or a slide). A particularly close connection of the retainers, and / or reinforcing structures with the natural semi-finished fiber is achieved here, if the material of the retainer, and / or reinforcing structures with the material of the melt fiber content in the natural semi-finished fiber is identical or can form a very close connection with this.

Depending on the requirements, a thermoplastic, an elastomer, a thermoplastic elastomer (TPE) or even a duroplastic may be used as the material for retainers and / or reinforcing structures.

The time of injection of the component 2 After closing force build-up is variable and will be advantageous depending on the state of the component 1 established. The criterion here is the already achieved degree of hardening or consolidation of the natural fiber semi-finished product.

The for the application of the surface component (component 3 ) required clearance in the mold cavity is preferably created by the approach of a dipping edge tool or by a replaceable mold half or a replaceable tool insert. This free space is so large that the coating in the intended area of the visible side of the component can arise in the required strength. This is thus dependent on the thickness of the intended material layer and is preferred for thin lacquer layer between. 0.1 mm and 1 mm, more preferably 0.4, mm to 0.6 mm. For thicker layers are preferably 1 mm to 20 mm, more preferably about 2-10 mm provided. A dipping edge tool is a tool with the so-called. Diving edge, drive over the punch and die into each other and the shape is already circumferentially closed, the depth adjustment of the cavity is still possible.

In a further preferred embodiment, the free space for the component arises 3 by opening the tool and transferring the component to another cavity (eg insert or sliding table technology).

As a component 3 Preferably, a flowable mass is used, which is dimensionally stable either when cooling or by the crosslinking of reactive components. component 3 is preferably a polyurethane layer with soft-touch effect or a PU lacquer layer.

The introduction of the surface component achieves a predetermined look and feel after curing.

As a component 3 TPE (thermoplastic elastomer) is furthermore preferably injected or, alternatively, polyurethane or a similar material, such as, for example, expandable polypropylene, is introduced. The reaction time of the surface component depends on the material used for the surface component and is preferably between about 40 and 180 s for PU systems.

The surface component is applied in a predetermined region of the visible side of the molding. This predetermined area may be the entire visual page or just one or more parts thereof.

It is possible to advantageously shorten the cycle time by additional heating elements when introducing the surface component.

As a significant advantage of the method according to the invention is to be considered that a post-processing is omitted or only the sprue system must be removed and a near-net shape component is achieved.

In a further preferred embodiment, the cutting of the component, including the natural fiber semi-finished, takes place only after the application of the surface component, ie after the coating with, for example, TPE / PU and thus outside of the injection mold that is used for this purpose.

In a further preferred embodiment of the method, a decorative film is incorporated into the surface of the natural fiber semi-finished product, which faces the visible surface of the component, and connected to the mat in the pressing process. in the Process step of the formation of the surface component is in step d. the process advantageously flooded with a polyurethane paint system.

A further preferred embodiment provides for using more than three components and, for example, for printing or contouring the surface component after curing. Preference is given to a plurality of superimposed layers of surface components in the procedure of step d. educated.

The apparatus for carrying out the method has a first mold half and a second mold half, which form a closed cavity and predetermine the shape of the desired lightweight component. The first tool half has free spaces which are suitable for receiving the material of the fastening elements and / or reinforcing structures. The free spaces may be connected to one or more material reservoirs for the material of the fasteners and / or reinforcing structures, which material may be injected under pressure. In a preferred embodiment, one or both of the mold halves can be tempered. For this purpose, an integrated in the tool halves electrical resistance heater is preferably used. In a preferred embodiment, a part of the first mold half is movable, so that the free spaces are formed only during or after the pressing process. In the case of a dipping edge tool, the second tool half is movable in its entirety in relation to the first tool half and the inserted semi-finished product or, in the case of a reversing plate, sliding table or turntable tool, exchangeable, so that a free space is created which covers the entire visible side of the Release molding so far that the necessary amount of surface component can be introduced into this space. Preferably, a insert injection molding machine is used, the tool has gripping elements for holding the natural fiber semi-finished mat.

The two tool halves can be pressed together with pressure, wherein the pressure is generated by a unit according to the prior art. For example, hydraulic drives of the injection molding machine are used for this purpose.

characters

1 illustrates the general process scheme as recited in claim 1. Step 1 shows the provision of the semifinished product ( 1 ) between the first tool half (left of the semi-finished product) and the second tool half (right of the semi-finished product). In step 2 the pressing of the natural fiber semi-finished product takes place in the injection mold (consisting of first and second mold half). step 3 includes back-injection of the natural fiber semi-finished material at the locations where retainers and / or reinforcing structures are provided. The material ( 2 ) for retainers, and / or reinforcing structures fills the cavities of the first mold half. In step 4 the second mold half is slightly withdrawn or exchanged for another mold half with a matched cavity to allow clearance in the given areas for the surface component ( 3 ) to accomplish. Subsequently, in this free space, the surface component ( 3 ).

2 illustrates the following embodiment. It is illustrated the process flow explained on a insert injection molding machine.

A semi-finished natural fiber semi-finished mat (flax / polypropylene 50/50) preheated to approx. 200-230 ° C is protected by handling ( 11 ) from the heating station ( 12 ) (here a hot press) and into the tool ( 14 ). Thereafter, the pressing of the semifinished product by closing the tool ( 14 ). After a defined delay time of 10 s, the formed natural fiber semi-finished mat is conveyed via the injection unit ( 15 ) partially back-injected with plastic compound (polypropylene). In parallel, the handling ( 11 ) a next semi-finished product from the semi-finished stack ( 13 ) in the heating station ( 12 ). After expiry of the reaction time of the surface component (this is also observed in the entry step of the system present here, since the surface component will already be introduced in the next pass on the other side of the insert), the tool ( 14 ) and the insert ( 16 ) with the pressing member rotated by 180 °. In the next step, the handling ( 19 ) the release agent in the mold half ( 17 ) and simultaneously from the handling ( 11 ) the tempered semi-finished mat from the heating station ( 12 ) and into the mold half ( 14 ). After closing the tool in the tool half ( 17 ) the flooding of the pressed component with a polyurethane system (surface component) (here PU system: Elalstolit R 8919/100 / WE35 with Iso 134/7 ) by means of the mixing head ( 18 ) and at the same time the pressing and injection molding of the semi-finished mat in the tool housing ( 14 ). In parallel, a next semi-finished product is placed in the heating station ( 12 ). After expiry of the reaction time of the polyurethane system used of 45 s, the tool is opened and the finished component of the handling ( 19 ). Then the insert ( 16 ) rotated 180 ° again and into the tool half ( 17 ) entered the release agent. This process is repeated as often as desired.

LIST OF REFERENCE NUMBERS

1

Natural fiber semis

2

Material for retainers, and / or reinforcement structures

3

surface component

4

second tool half, withdrawn

11

Handling Handling Robot

12

heating station

13

Natural fiber semi-finished stack

14

first tool half

15

injection unit

16

insert

17

second tool half

18

mixing head

19

Handling Handling Robot

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10327725 A1 [0003]
• DE 10341855 A1 [0004]
• DE 202007007498 U1 [0005]

Cited non-patent literature

• Iso 134/7 [0041]

Claims (14)

Method for producing a lightweight component, which has a visible side and a fastening side, characterized by the following production steps: a) inserting a natural semi-finished fiber into an injection mold, b) pressing and / or forming and consolidating the natural semi-finished fiber product (semifinished product) into a molded part in the injection molding tool, c) injection-molding of fastening elements and / or reinforcing structures to the molded part on the fastening side of the lightweight component in free spaces in the injection mold, wherein fastening elements and / or reinforcing structures are molded on only a part of the surface of the fastening side, d) applying the surface component in a predetermined region of the visible side of the molding. Method according to one of the preceding claims, characterized in that the natural fiber semi-finished product has a defined melt fiber content. A method according to claim 2, characterized in that the natural fiber semi-finished product from step a. prior to insertion, in particular with a contact heater or a heater, preheated, is when it is semi-finished with a melt fiber content. A method according to claim 1, characterized in that the natural fiber semi-finished product before step a. impregnated in a dipping bath with matrix resin or provided by spraying with matrix resin, if the natural fiber semi-finished product has no melt fibers. A method according to claim 1, characterized in that the natural semi-finished fiber is thermoset bonded. Method according to one of the preceding claims, characterized in that the steps b. and c. parallel or partially parallel. Method according to one of the preceding claims, characterized in that step b. is accelerated by additional heating or by cooling depending on the composition of the natural fiber semi-finished product. Method according to one of the preceding claims, characterized in that step b. is combined with a separating, in particular a punching operation. Method according to one of the preceding claims, characterized in that in step c. the free spaces are formed in the injection mold by after step b. Parts of the injection mold are moved and thus release the free space. Method according to one of the preceding claims, characterized in that for step d. the lightweight component is moved into a second cavity. Method according to one of claims 1 to 9, characterized in that for step d. a part of the injection mold is moved and thus releases a free space on the visible side of the lightweight component, in which the surface component can be registered. Method according to one of the preceding claims, characterized in that step d. is accelerated depending on the composition of the surface component by additional heating or by cooling. Method according to one of the preceding claims, characterized in that the natural fiber semi-finished product is provided with a decorative film facing the visible side of the lightweight component and that the surface component in step d. a paint system is. Method according to one of the preceding claims, characterized in that the natural fiber semi-finished product is provided on the visible side with a plurality of layers of the same or different surface components.

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