DE102015012514B4 - Process for the production of a short fiber reinforced plastic injection molded component using an injection mold - Google Patents

Abstract

Method for producing a short-fiber-reinforced plastic injection molded component (1), in which a liquid starting component of a plastic material (5) with short fibers (3) integrated therein is injected under pressure and heat into a mold cavity (27) of an injection mold and is cured therein, characterized that in order to provide the short fibers (3), a fibrous waste material (7, 9) occurring as material waste during the production of a fiber-reinforced plastic component (21) is collected as a recyclate, and that the recyclate is further processed to form the short fibers (3), that the fiber-reinforced plastic component (21) is produced in a fiber-reinforced composite production process, in which a still dry semi-finished fiber product (11) is cut to size in a cutting process step and a first waste material (7) is produced as waste material, the cut semi-finished fiber product (11 ) is preformed and placed in a factory tool cavity is inserted, in a process step a liquid starting component of a matrix material (15) is injected under pressure and heat into the tool cavity and is cured therein, and in a final processing step final contour processing takes place, in which a second waste material (9) is produced, that the semi-finished fiber product (11) embedded in the matrix material (15) of the fiber-reinforced plastic component (21) is made up of endless carbon fibers, and that the first waste material (7) produced in the cutting process step is processed into the short fibers in a short-fibre processing unit (12). (3) is further processed.

Description

The invention relates to a method for producing a short-fiber-reinforced plastic injection molded component according to the preamble of patent claim 1.

In the case of such a short-fiber-reinforced plastic injection-molded component, the use of short or long carbon fibers is usually dispensed with for reasons of cost and glass fibers are used instead, which are usually embedded in a thermoplastic polyamide. The use of polyamide is necessary with regard to favorable mechanical parameters (e.g. component rigidity). However, polyamide tends to absorb water, which means that the plastic injection molded component can warp due to length expansion/shrinkage. However, when manufacturing a tank cap hinge as such a plastic injection-molded component, this can lead to gap size problems between the tank cap and the adjacent opening edge area in the outer skin of the vehicle.

From the DE 10 2012 025 372 A1 a generic tank lid hinge is known, which is designed as a fiber-reinforced plastic component whose short fibers can be made of carbon. The use of carbon fibers results in increased mechanical stiffness characteristics compared to glass fibers. In addition, a carbon fiber reinforced plastic component can be produced with a reduced weight compared to a glass fiber reinforced plastic component. In addition, compared to a glass-reinforced plastic component, water absorption results in significantly reduced component torsion, which increases component quality. With regard to thermal linear expansion, carbon fibers are also very well suited to achieve the gap dimensions.

From the DE 10 2011 006 819 A1 a three-dimensional sandwich structure is known. From the DE 603 02 277 T2 a device for extruding plastic material is known. From the DE 20 2010 008 303 U1 a device for producing a molded part with a three-dimensionally structured surface is known.

The object of the invention is to provide a method for producing a short-fiber-reinforced plastic injection-molded component that has a high component quality with reduced production costs compared to the prior art.

The object is solved by the features of claim 1. Preferred developments of the invention are disclosed in the dependent claims.

In the process, a liquid starting component of a thermoplastic material (for example PA) with short fibers integrated therein is injected under pressure and heat into a mold cavity of an injection molding tool.

The invention is based on the fact that the short fibers for the injection molding process can be provided in a much more material-saving and cost-effective manner compared to the prior art, which means that even plastic injection-molded components with carbon fibers can be produced inexpensively in large-scale production. According to the characterizing part of patent claim 1, a fiber-containing waste material is collected as a recyclate in order to provide the short fibers, which occurs as material waste in the production of a fiber-reinforced plastic component. The recyclate is therefore not removed from the process chain, but rather further processed into short fibers (carbon fiber injection molded component). For example, a reinforcement element for a B-pillar of a motor vehicle can be produced in an RTM (Resin Transfer Molding) process. The waste material containing carbon fibers that occurs in the RTM process is no longer removed from the process chain as material waste, but rather used as recyclate in the manufacture of the plastic injection molded component.

Alternatively and/or additionally, so-called end-of-life components can also be used as recyclate.

In the above RTM process (or in an alternative fiber composite production process), a semi-finished fiber product that is still dry (i.e. not yet saturated with matrix material, such as a non-crimp fabric or knitted fabric) is cut to size in a preparatory cutting process step. A first fibrous waste material is produced as material waste. In a downstream preform process step, the cut semi-finished fiber product is preformed and placed in an RTM tool cavity. An RTM process step is then carried out, in which a liquid starting component of a mostly duroplastic matrix material is injected under pressure and heat into the RTM tool cavity and is cured therein. In a final processing step, the final contour is processed, during which a second fibrous waste material is produced.

The semi-finished fiber product used in the RTM process is made up of continuous fibres, namely continuous carbon fibres.

The first waste material produced in the above cutting process step consists of pure fiber material and is therefore further processed into short fibers in a processing unit without pre-treatment. For example, the processing unit can be a cutting station, in which the continuous fiber residues of the first waste material are diverted to the short fibers.

In contrast, the second waste material occurring during the above final contour machining does not consist of a fiber material, but rather of a fiber material embedded in a plastic matrix. Correspondingly, the second waste material must first be fed to an exposure process (for example a pyrolysis process) in which the fiber material is exposed while the plastic matrix is burned. The fiber material exposed in the pyrolysis process can then (like the above first waste material) be fed to the processing unit.

The short fibers produced in the processing unit are further processed with an injection-mouldable plastic material (e.g. PA) to form plastic granulate, which is used for the injection molding process to produce the short-fiber-reinforced plastic injection-moulded component.

In this way, for example, a tank cap hinge can be produced cost-effectively as a carbon fiber injection molded component, which is significantly more torsion-resistant than a glass fiber injection molded component in comparison to a glass fiber injection molded component when it absorbs water. In this way, the gap size between a tank cap and the adjoining edge area of the opening in the outer skin of the vehicle can be kept constant even when water is absorbed.

The invention and its advantageous training and developments and their advantages are explained in more detail below with reference to drawings.

• 1 in einer grob schematischen Schnittdarstellung ein Kunststoffspritzguss-Bauteil;
• 2 bis 4 jeweils Ansichten, die die Prozessschritte zur Herstellung des in der 1 gezeigten Kunststoffspritzguss-Bauteils veranschaulichen; und
• 5 in einer Seitenansicht ein in Einbaulage gezeigtes Tankdeckelscharnier, das als Kunststoffspritzguss-Bauteil hergestellt ist.

Show it:

• 1 in a roughly schematic sectional view, a plastic injection molded component;
• 2 until 4 each views showing the process steps for producing the in the 1 illustrated plastic injection molded component shown; and
• 5 in a side view, a tank lid hinge shown in the installed position, which is produced as a plastic injection-molded component.

The above figures are made for easy understanding of the invention. Therefore, the figures are only roughly simplified representations that do not reflect realistic process steps or components.

In the 1 a finished plastic injection molded component 1 is shown in a sectional view, in which short fibers 3 are embedded in a thermoplastic material 5 (for example PA, PP, etc.). The short fibers 3 are carbon fibers, for example, which are produced from a waste material 7, 9, which occurs as waste material in a separate RTM process.

The RTM process is described below using the 2 described: Accordingly, in a preparatory cutting process step, a semi-finished fiber product 11 that is still dry is cut to size in an indicated cutting station 13 . In the cutting station 13, a first waste material 7 occurs, which consists of pure fiber material. A preform process step then takes place, in which the cut semi-finished fiber product 11 is three-dimensionally preformed and placed in an RTM tool cavity (not shown). In a subsequent RTM process step, a liquid starting component of a duroplastic matrix material 15 is injected under pressure and heat into the RTM tool cavity and cured therein. Finally, there is a finishing step in which, for example, by means of a in the 2 indicated stamping tool 17, an assembly opening 19 is introduced into the fiber-reinforced plastic component 21. This results in a second waste material 9 which, in contrast to the first waste material 7 , does not consist of pure fiber material but rather of a fiber material embedded in the plastic matrix 15 .

The semi-finished fiber product 11 used in the manufacture of the fiber-reinforced plastic component 21 is made up of continuous carbon fibers which are interwoven, for example, to form a textile, a fleece, a knitted fabric or a woven fabric or the like.

Based on 3 the process sequence for the production of a plastic granulate 23 is described, which is suitable for the injection molding process ( 4 ) for the production of the plastic injection molded component 1 is used. Accordingly, the waste material obtained in the cutting process step 7 in the 3 processed in a processing unit 12 (e.g. another cutting station) to form the short fibers 3 and mixed with the injection-mouldable thermoplastic material 5 in a mixer unit 14, for example an extruder, and the plastic granulate 23 is produced from this as bulk material.

The plastic granulate 23 is according to the 4 an indicated injection unit 25 of a Injection mold supplied. In the injection unit 25, the plastic granules 23 are liquefied under pressure and heat and injected into an injection mold cavity 27 and cured therein.

In the 5 a tank lid hinge is shown as an example in an indicated installation position, which is manufactured as such a plastic injection-molded component 1 . The tank cap hinge is pivotally mounted at the end about a pivot axis 29 and carries a tank cap 31 which is spaced apart from the adjoining opening edge region 35 of a vehicle outer skin by a predefined gap dimension 33 .

Reference List

1

Plastic injection molded part

3

short fibers

5

thermoplastic plastic, plastic material

7.9

waste material

10

pyrolysis process

11

dry fiber semi-finished product

12

Processing step, short fiber processing unit

13

cutting station

14

mixer unit

15

thermosetting matrix material

17

stamping tool

19

mounting hole

21

Fiber-reinforced plastic component

23

plastic granules

25

injection unit

27

injection mold cavity

29

pivot axis

31

gas cap

33

gap size

35

opening edge area

Claims (3)

Method for producing a short-fiber-reinforced plastic injection molded component (1), in which a liquid starting component of a plastic material (5) with short fibers (3) integrated therein is injected under pressure and heat into a mold cavity (27) of an injection mold and is cured therein, characterized that in order to provide the short fibers (3), a fibrous waste material (7, 9) occurring as material waste during the production of a fiber-reinforced plastic component (21) is collected as a recyclate, and that the recyclate is further processed to form the short fibers (3), that the fiber-reinforced plastic component (21) is produced in a fiber-reinforced composite production process, in which a still dry semi-finished fiber product (11) is cut to size in a cutting process step and a first waste material (7) is produced as waste material, the cut semi-finished fiber product (11 ) is preformed and made into a who tool cavity is inserted, in a process step a liquid starting component of a matrix material (15) is injected under pressure and heat into the tool cavity and is cured therein, and in a final processing step final contour processing takes place, in which a second waste material (9) is produced, that the semi-finished fiber product (11) embedded in the matrix material (15) of the fiber-reinforced plastic component (21) is made up of endless carbon fibers, and that the first waste material (7) produced in the cutting process step is processed into the short fibers in a short-fibre processing unit (12). (3) is further processed. procedure after claim 1 , characterized in that the second waste material (9) occurring in the processing process step is subjected to a pyrolysis process (10), in which the fiber material is exposed while the matrix material (15) is burned, and in that the fiber material of the short fiber exposed in the pyrolysis process (10) is exposed - Processing unit (12) is supplied. procedure after claim 1 or 2 , characterized in that the short fibers (3) produced in the short fiber processing unit (12) and the injection-moldable plastic material (5) are mixed in a mixer unit (14) and further processed into plastic granules (23), which are used for the injection molding process to produce the short fiber reinforced plastic injection molded component (1) is used.

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