KR20040094835A - Method for coating fiber-reinforced plastic structural parts and structural part so produced - Google Patents

Abstract

Fiber-reinforced plastic parts are coated for the purification and coloring of surfaces, especially when used in car bodies in the automotive industry. According to the invention, a plastic film which already has the finally required properties with regard to the quality of the part surface and in some cases the coloration of the part surface and which corresponds to the shape of the part surface is inserted into a suitable mold. Preferably, a fiber reinforced plastic having a duroplastic base or a thermoplastic base is applied to a surface other than the surface of the preformed film in a manner suitable for the composition of the semifinished product, and the fiber reinforced plastic is pressed and cured or cooled. The finished product is discharged from the mold.

Description

TECHNICAL FOR COATING FIBER-REINFORCED PLASTIC STRUCTURAL PARTS AND STRUCTURAL PART SO PRODUCED}

For example, fiber-reinforced plastic parts manufactured by Resin Transfer Molding (RTM), Long Fiber Reinforced Thermoplastic (LFT), Glass Mat Reinforced Thermoplastic (GMT) or Sheet Molding Compound (SMC) techniques are particularly used as body parts in the automotive industry. If desired, the surface is coated for purification and coloring. However, such a coating is very expensive because the surface of the plastic part must be pretreated. The rationale lies in manufacturing techniques that make the surface morphology uneven. The causes of surface defects in the unrefined parts include, for example, pores, air bubbles generated during heat treatment, or released fiber ends. In general, mechanical surface treatment, such as polishing or priming, is required, so a high level of manual work is necessary to achieve the desired surface quality. Attempts have also been made to achieve surface uniformity, for example, by additionally providing surface layers such as nonwoven layers containing a large amount of resin, or by Inmould-Coating (IMC) treatment.

Achim Grefenstein's paper, "Plastic and Metallic Coatings-Using Film Back Injection Techniques Instead of Metal Surface Lacquering" (10/99, Carl Hanser, Munich, Munich). It is known. The film is inserted into the injection molding die in a preformed state. The cavity of the film is then bag injected using plastic in a known manner so that the purified surface can be produced in one work process. However, when using film bag injection technology, only relatively small plastic parts below a given dimension can be manufactured. Using crimping techniques or RTM techniques, for example, parts of relatively large dimensions can be manufactured, such as passenger car bonnets, trunk lids or commercial vehicle air deflectors, which can meet the required mechanical properties through fiber reinforcement. Let's do it. However, even with the above techniques, the surface quality required for coating cannot be achieved.

The present invention relates to a method for purifying a surface of a fiber reinforced plastic part according to the preamble of claim 1 and a part made in this way.

1-6 are process diagrams schematically illustrating the steps of a manufacturing process of a part according to the invention.

* Description of the major symbols in the drawings *

1: film 2: roll

3: forming die 5: preformed film

6: female die 7: mold

8: male die 9: semi-finished product

10: Finished Part 11: Ejector

It is an object of the present invention to reduce the costs required to purify the surface of parts made of fiber reinforced plastics.

The object is that the plastic film, which already has the required properties with respect to the surface quality and, in some cases, the coloration of the surface and which is preformed in correspondence with the shape of the part surface, is inserted into a mold corresponding to the part dimension, preferably Duro Fiber-reinforced plastics with a plastic or thermoplastic base are applied to the surface except the surface of the preformed film in a manner adapted to the composition of the semifinished product, which is completed from the mold after the fiber-reinforced plastics are pressed and cured or cooled. Is achieved by ejecting the parts.

Purification of the part surface is accomplished using film bag injection molding techniques or film-RTM techniques. In film back injection, the preformed film is placed in one of the forming dies of the press, ie a female die or a convex die, and in the counterpart of the die in the form of a mat or plastic By laying the fiber reinforced plastic of the preformed film is combined with the mat or plasticizer by a press technique suitable for the composition of the semifinished product.

The film RTM is made in a closed mold corresponding to the closed press dies of the press, ie the concave die and the convex die. A preformed film is inserted into the mold, and only a fiber mat, i.e. a fiber reinforcement, is inserted below the cavity of the film. The empty mold is filled with a mixture of resin and hardener in a known manner, wherein the mat is wet and the cavity under the film is filled. The mold remains closed until the injected resin has cured. The technique can be considered in the disclosed method as well.

Using the method according to the invention, not only the film bag injection technique but also the film RTM technique are large-size with a surface area comparable to that of a large and known film bag injection such as a trunk lid or door member, for example. Parts can be manufactured at low cost. Now, fiber-reinforced plastics and processing techniques that have previously required the high costs described above for surface refining can be used. The film may comprise a colored layer or a specially prepared coating layer. Suitable films are in particular coextruded two- or three-ply films such as those also used in film bag injection techniques. Layers comparable to the coating layer can be made by coextrusion of thin plastic layers dyed in a two- or three-ply combination. According to the process according to the invention, purification of fiber reinforced plastics, preferably with a durroplastic base or thermoplastic base, can be made in a much smaller number of working steps than the process according to the prior art without preliminary surface treatment and coating treatment. Subsequently, the coating process can be carried out at low coating cost for effect coloring.

The process sequence in film back injection is described in more detail in the process diagram according to the process steps schematically shown in FIGS. 1 to 6.

In the process step according to FIG. 1, the film 1 suitable for the film bag injection technique is ejected from the roll 2 and cut into the required size. The cut film 1 is placed on a forming die 3 having the form of the surface of the part to be manufactured in the process step according to FIG. 2, subjected to thermal action, preferably by a suitable device, denoted by the numeral "4". It is formed into a film 5 having the surface form of the part to be produced by preforming. The film 5 is placed in a concave die 6 of a press 7 schematically shown in the process step according to FIG. 3 after a burr and removal of residual material (not shown in the figure). . The contour of the convex die 8 takes into account the wall thickness of the part to be manufactured. In the process step according to FIG. 4, as the semifinished product 9 of fiber-reinforced plastic is inserted under the cavity of the film 5 in the press 7, the preformed film 5 has an outer surface, ie the outside of the material. It is placed on the part and becomes the front which can be seen from the outside. In the process step according to FIG. 5, a suitable molding technique is applied to the semifinished product 9, in which the cavity between the preformed film 5 and the convex die is filled with fiber reinforced plastic to conform to the contour of the film. Semifinished products are particularly suitable for fibrous reinforced plastics, in particular SMC, GMT and LFT, which are molded through impact extrusion and heat treatment. The molding temperature should be lower than the temperature which may damage the film 5. After the fiber reinforced plastic is cured or cooled, the press 7 can be opened and the finished part 10 can be ejected, as shown in FIG. 6, and then the convex die 8, for example, by the ejector 11. Separated from. In some cases the part may be used after removal of the burr edge of the glass fiber reinforced plastic. The component 10 has a ready-to-use surface that is no longer required for post-treatment or coating by the film 5. Additional coating processes can be carried out at low coating costs for effect coloring.

Claims (11)

A method for purifying the surface of a part made of fiber reinforced plastic that can be molded through impact extrusion or hot forming, Firstly, on a forming die having the surface shape of the part, a plastic film is placed which can have in advance the final required properties with respect to the quality of the part surface and in some cases the coloration of the part surface. Molded to correspond to the surface morphology of the part, the preformed film is inserted into a suitable mold, preferably with the exception of the surface of the film preformed with a fiber-reinforced plastic with a duroplastic matrix or thermoplastic matrix. A method of refining parts surfaces, characterized in that the cotton is applied in a manner suitable for the composition of the semifinished product and the finished product is discharged from the mold after the fiber reinforced plastic is cured or cooled. The method of claim 1, The preformed film is placed in one of the forming dies of the press, ie a concave die or a male die, and the counterpart of the die has a fiber reinforced plastic in the form of a mat or plasticized material. Wherein the preformed film is combined with the mat or plasticizer by a press technique suitable for the composition of the semifinished product. The method of claim 2, The part material and semi-finished product, characterized in that the fiber reinforced plastic produced by the Long Fiber reinforced Thermoplastic (LFT) technique, Glass Mat Reinforced Thermoplastic (GMT) technique or Sheet Molding Compound (SMC) technique is used. The method of claim 1, The preformed film is inserted into a mold, a fiber mat is placed under the cavity of the film, the mold is closed and filled with a mixture of resin and hardener, the mold closed until the injected resin is cured. Characterized in that it is maintained. The method according to any one of claims 1 to 4, A plastic film having a coating layer is used for the purification of the surface of the component. The method according to any one of claims 1 to 4, A two or three ply coextruded film with a dyed layer is used for the purification of the part surface. The method according to any one of claims 1 to 4, Wherein the film tablet surface of the part is coated with an effect coloring technique. A fiber reinforced plastic part produced by the method according to any one of claims 1 to 7, The surface of the part, preferably on top of a fiber-reinforced plastic with a duroplastic base or thermoplastic base, in advance having the final required properties with respect to the quality of the part surface and in some cases the coloration of the part surface A fiber reinforced plastic part, characterized in that it comprises a preformed plastic film corresponding to the shape. The method of claim 8, Wherein the plastic film comprises a coating layer for purification of the surface of the part. The method of claim 8, Wherein the film comprises a two- or three-ply coextrusion film with a dyed layer for purification of the surface of the part. The method of claim 8, Wherein the film tablet surface of the part is coated by effect coloring technique.