Process for the production of plastic molded parts

Abstract

A method for producing plastic molded parts, each plastic molded part comprising a plurality of surface areas (11, 12) which differ from one another in terms of their color, surface structure and / or material, comprising the steps of: - inserting a mask (15) into a mold (20), - applying a release agent (16) to at least a portion of a mold surface (21) of the mold (20) which is not covered by the masking (15), - removal of the masking (15) from the mold (20), - inserting a film blank (13) into the forming tool (20), wherein a front side (13a) of the film blank (13) comes to rest on a forming surface (21) of the forming tool (20), wherein the film blank (13) covers the area of ​​the forming surface (21) which was previously covered by the masking (15), - applying a lacquer layer (14), at least to a portion of the mold surface (21) of the mold (20) and - Demoulding the plastic moulded part from the mould (20).

Description

[0001] The invention relates to a method for producing plastic parts, wherein each plastic molded part comprises several areas that differ from one another with regard to their color, surface structure and / or material.

[0002] So-called masking processes are known in the art for producing plastic components with two-tone surfaces. One such process is described, for example, in DE 694 28 377 T2. To produce an elastomeric skin comprising at least two different surface materials, two plastic materials are injected onto a mold surface of a molding tool. An area of ​​this mold surface is shielded by a mask, while a layer of a first elastomeric material is injected onto the mold surface. The mask is then removed, and a second elastomeric material is injected onto the previously masked area. This allows dashboards or other interior components for the automotive industry to be produced in two or more different colors.

[0003] Furthermore, methods are known from the prior art in which a carrier element of a multi-colored plastic component, such as the instrument panel, is first created and then a decorative panel is produced. The decorative panel is then attached to the carrier element using a clip connection.

[0004] However, the described method has the disadvantage that the separate production of the decorative panel and the carrier element, i.e. the instrument panel, and their subsequent assembly results in unnecessary costs and prolongs the process.

[0005] DE 10 2005 036 835 A1 discloses an interior trim part for a vehicle door using alternative manufacturing processes. The interior trim part comprises a cushion to which a polyurethane outer skin is molded by an injection molding process. Expanded polyurethane foam is injected over the polyurethane outer skin, and a reinforcement layer is either molded as a single piece or attached to the polyurethane foam layer.

[0006] US 2003 / 0180498 A1 shows a method for producing at least one skin forming a visible front surface of an interior trim part, wherein the front surface comprises at least one prefabricated insert with a visible back side.

[0007] The present invention aims to provide a method that overcomes the disadvantages of the prior art. Furthermore, it is the object of the invention to provide a simplified method that can be used to easily produce plastic components that have multiple regions with different properties regarding color, structure, or surface material.

[0008] This object is achieved by a method having the features of the independent claims. The dependent claims represent advantageous embodiments of the invention.

[0009] To achieve this object, the invention proposes a method for producing plastic molded parts, wherein each plastic molded part has several regions that differ from one another in terms of their color, surface structure, and / or material. The method comprises the steps of inserting a film blank into a mold, wherein a front side of the film blank comes to rest on a molding surface of the molding tool, applying a layer of lacquer to at least a portion of the molding surface of the molding tool, and demolding the plastic molded part from the molding tool.

[0010] The film blank forms a first area of ​​the surface of the plastic molded part to be produced, and the paint layer forms a second area of ​​the surface of the plastic molded part. In the plastic molded part, the first area differs from the second area in terms of its surface structure, color, and / or material. Particularly suitable film materials are coextruded films with a carrier layer, for example, made of a PC-ABS blend or pure ABS, and a decorative layer, for example, made of PMMA.

[0011] Furthermore, before inserting the film blank, the method comprises the steps of inserting a mask into the mold, applying a release agent to at least a section of the mold surface of the mold that is not covered by the mask, and removing the mask from the mold. The outer geometric shape of the mask can correspond to the outer geometric shape of the film blank. By applying the release agent, the subsequent plastic molded part can be demolded from the mold in a particularly simple manner. The mask serves as protection for the film to be inserted later, in order to protect its surface that comes into contact with the mold from damage and contamination by the release agent. This is particularly important because this surface is the visible side of the film, which must meet the requirement of a Class A surface.

[0012] In addition, after applying the lacquer layer, a polyurethane layer can be applied to at least a portion of the mold surface of the mold.

[0013] The lacquer layer and / or the polyurethane layer can be applied to at least a portion of the reverse side of the film blank, opposite the front side. The lacquer layer comes into direct contact with the areas of the mold surface that have been sprayed with release agent. Furthermore, the lacquer layer can also come into direct contact with the reverse side of the film blank. The polyurethane layer is then applied to the areas of the mold surface or the reverse side of the film blank that have previously been sprayed with the lacquer layer.

[0014] The lacquer layer comprises a mixture of base lacquer, crosslinking agent and (fully demineralized) deionized or distilled water.

[0015] Subsequently, the semi-finished product created so far, comprising the film blank and the paint layer, remains in the mold for a predetermined time to achieve physical drying before the polyurethane layer is applied. During the application of the polyurethane layer, a mixture of polyol and isocyanate is applied using a spraying device, such as a spray gun. The semi-finished product created so far, comprising the film blank, the paint layer, and the polyurethane layer, then remains in the mold for a predetermined reaction time. The plastic molded part can then be removed from the mold and trimmed to its final contour in a final process step.

[0016] Additionally, the mold surface of the molding tool can include at least one fastening element for positively securing the film blank to the molding tool. This provides the advantage that the film blank is permanently connected to the molding tool, preventing the film blank from slipping during the application of the lacquer layer and the polyurethane layer.

[0017] The fastening element can have an omega-shaped cross-section. This offers the advantage of achieving particularly good shielding of the area covered by the film blank from the outer uncovered area. This prevents the subsequently applied lacquer or polyurethane layer from penetrating the area between the film blank and the tool. Furthermore, the omega-shaped cross-section of the fastening element creates a particularly secure, positive connection between the film blank and the mold surface.

[0018] To explain the inventive method, a mold for producing a plastic molded part using a method of the type described above is described, comprising a mold surface that shapes an outer surface of the plastic part. Furthermore, at least one fastening element can be arranged on the mold surface for attaching a film blank to the mold. The film blank can be a film thermoformed in a previous process step.

[0019] Furthermore, the fastening element can form a circumferential, closed contour on the mold surface and divide the mold surface into an inner region and an outer region with respect to the fastening element.

[0020] The fastening element may preferably have an omega-shaped cross-section.

[0021] The method according to the invention makes it possible to integrate a thermoformable film directly into an in-mold coating polyurethane spraying process. This simplifies the manufacturing process for plastic components and eliminates subsequent assembly steps. The structurally defined omega-shaped cross-section of the fastening element makes it possible to integrate a pre-thermoformed film, the so-called "film blank," directly into a spray skin that encompasses the paint layer and the polyurethane layer. This not only eliminates the additional assembly step but also reduces the logistical effort involved in implementing the process.

[0022] The invention is explained in more detail below with reference to the description of the figures. The claims, the figures, and the description contain a multitude of features, which are explained below in connection with exemplary embodiments of the present invention. Those skilled in the art will also consider these features individually and in other combinations to form further embodiments adapted to corresponding applications of the invention.

[0023] They show in schematic representation: Fig. 1a - f show the individual process steps in carrying out the process according to the invention, Fig. 2 a sectional view through a fastening element and Fig. 3 a plastic molded part produced according to the invention

[0024] In Fig. Figure 1a shows the first step of the method according to the invention. A mask 15 is inserted into a mold 20. The mold 20 has a recess or cavity with a mold surface 21. The mold surface 21 shapes the plastic molded part to be produced. In other words: the negative shape of the mold surface 21 results in a positive shape for the plastic molded part. By inserting the mask 15, a central area of ​​the mold surface 21 is covered. The edge area of ​​the mold surface 21 remains free.

[0025] In a second process step, which is Fig. As shown in Figure 1b, a release agent 16 is applied to the mold 20 using a spraying device, for example, a spray gun. The areas of the mold surface 21 not covered by the masking, as well as a backside of the masking 15, are sprayed with release agent 16. After spraying the release agent, a predetermined drying time is observed until the release agent has dried. The drying time can range from 25 to 40 seconds.

[0026] The subsequent third step is Fig. 1c. In this method step, the masking 15 is removed from the molding tool 20. After the masking 15 has been removed, a film blank 13 is inserted into the molding tool 20. The film blank 13 can be made of a thermoformable material and can either have been thermoformed in a previous step or be formed upon insertion into the molding tool 20. In such an embodiment, the molding tool 20 then has thermocouples for heating the film blank 13. The film blank 13 essentially covers the area of ​​the mold surface 21 that was previously covered by the masking 15.

[0027] Fastening elements 22 are provided in the forming surface 21 of the forming tool 20, which are shown for example in Fig. 2. The fastening elements 22 have a cross-section which essentially corresponds to the shape of the Greek capital letter Ω. Such a cross-section is shown in Fig. 2. The foil blank 13 has a groove in its edge region with a cross-sectional shape that, at least in sections, has the shape of an Ω. The foil blank 13 can be releasably connected to the groove on the fastening element 22, thereby creating a positive connection that prevents the foil blank from slipping. As shown in Fig. As shown in Figure 1c, the film blank 13 has a front side 13a and a back side 13b. When the film blank 13 is inserted into the mold element 20, the front side 13a rests on the mold surface 21.

[0028] Subsequently, in a fourth step, a lacquer layer 14 is sprayed on, as in Fig. 1d. The lacquer layer 14 is composed of a mixture of base lacquer, crosslinker, and demineralized water and is sprayed onto the areas of the mold surface 21 that were previously sprayed with release agent 16. Under certain circumstances, a portion of the lacquer layer 14 can also be sprayed onto a rear side 13b of the film blank 13. The lacquer layer 14 is sprayed onto the mold 20 using a spraying device, for example, a spray gun.

[0029] After a drying time, during which the paint layer dries physically, the Fig. 1e. In this process step, a polyurethane layer (PUR) is applied to the lacquer layer 14. According to a first embodiment of the process, the polyurethane layer is sprayed only in the areas not covered by the film blank. According to a second embodiment of the invention, the polyurethane layer can also be applied to a rear side 13b of the film blank 13. The polyurethane layer 17 is applied using a spraying device, for example a spray gun. In the process, polyol and isocyanate react to form polyurethane. After a predetermined reaction time has been observed, during which the polyurethane reacts completely, the plastic molded part can then be demolded from the mold element 20, as shown in Fig. 1f. The reaction time is in the range of 65 to 80 seconds. If necessary, the molded part is then trimmed along the edges to create the final contour of the plastic molded part.

[0030] In the following, with reference to Fig. 2, the design of the fastening element 22 will be described, which is provided in one piece or integrally in the mold surface 21 of the mold 20. This fastening element 22 has a cross-sectional shape that corresponds to the Greek capital letter Ω. The fastening element 22 creates a closed circumferential contour on the mold surface 21 and consequently divides the mold surface 21 into an inner region 21a and an outer region 21b. The surface of the inner region 21a is covered by inserting the film blank 13, whereby the surface of the outer region 21b remains free. The second region 12 is created by spraying on the lacquer layer 14 and the polyurethane layer 17. The polyurethane layer 17 and the film blank 13 abut one another along an abutting edge.

[0031] In Fig.Figure 3 shows a plastic molded part produced using the method according to the invention. As can be seen therefrom, the film blank 13 forms a first region 11, and the polyurethane layer forms a second region 12. The first region 11 corresponds to a positive impression of the negative inner region 21a of the mold surface 21 of the molding tool 20. The shape of the second region 12 corresponds to the shape of the outer region of the mold surface 21b of the molding tool 20.

Claims

[1] Method for producing plastic molded parts, each plastic molded part comprising several surface areas (11, 12) that are different from each other with respect to their color, surface structure and / or material, with the steps: - Inserting a masking (15) into a mold tool (20), - Applying a separating agent (16) at least to a section of a mold surface (21) of the mold tool (20) that is not covered by the masking (15), - Removing the masking (15) from the mold tool (20), - Inserting a film section (13) into the mold tool (20), wherein a front side (13a) of the film section (13) comes to rest on a mold surface (21) of the mold tool (20), the film section (13) covering the area of the mold surface (21) that was previously covered by the masking (15), - Applying a paint layer (14), at least to a section of the mold surface (21) of the mold tool (20) and - Demolding the plastic molded part from the mold tool (20). [2] The method according to claim 1, characterized thereby , wherein - after applying the paint layer (14), - a polyurethane layer (17) is applied at least to a section of the mold surface (21) of the mold tool (20). [3] The method according to any one of the preceding claims, characterized thereby , wherein the paint layer (14) and / or the polyurethane layer (17) is applied at least to a section of one of the front side (13a) and the opposite back side (13b) of the film section (13). [4] The method according to any one of the preceding claims 1 to 3, characterized therebythat the film cutout (13) is positively connected to at least one fastening element (22), wherein the at least one fastening element (22) is formed on the surface (21) of the mold tool (20). [5] Method according to claim 4, characterized thereby that the film cutout (13) is positively connected to a fastening element (22) which has an omega-shaped cross-section. [6] Method according to one of the preceding claims 4 or 5, characterized thereby that the fastening element (22) is reproduced as a negative in the form of a groove in the plastic molded part (10).

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