DE10053050A1 - Molding process for fluid diffusion resistant plastic component involves injecting plastic melt onto a barrier layer prelocated in a molding tool - Google Patents

Abstract

A diffusion barrier layer(22) is located on at least one of the tool surfaces(14,16) facing the molding cavity of a tool(10,12). Plastic melt is injected into the cavity and after solidifying forms an integral component with the barrier layer. An Independent claim is also included for a plastic component, in particular a plastic fuel tank, comprising a part or whole shell construction molded by the claimed process.

Description

The invention relates to a plastic molded part and to a method for its production the preambles of independent claims 1 and 10.

It is known to use differently shaped plastic parts with different designs Processes such as injection molding, deep drawing, compression molding, foaming and blowing, manufacture. Here, a flowable plastic mass is placed in a mold space Tool introduced where it takes its shape. The tool usually includes two tool halves that can be detachably connected to one another and that together form the mold space form. A distinction is made between the respective tool halves according to the procedure for example as a closing and nozzle side or as a matrix / patrix. After the Plastic mold in the mold space, the tool is opened and the molded part is removed from the mold.

There are also various methods for producing diffusion barrier layers Surfaces of molded plastic parts are known, which have a permeability of the molded part for certain gases or liquids. Next to the subsequent application of the diffusion barrier layer by painting or laminating chemical aftertreatment processes known. A chemical process that is used for Creation of a diffusion barrier layer in plastic fuel tanks for motor vehicles fluorination has prevailed. The surface of the plastic is covered with a fluorine-containing gas brought into contact, with some hydrogen atoms of the plastic be substituted by fluorine. The surface of the molded plastic part that has been hydrophilized in this way leads to a reduced tendency of hydrophobic fluids, for example fuels, to Adsorption and diffusion through the plastic. This is based on a similar principle Sulfonation process in which polar SO functionalities in the to be treated Surface. Diffusion barrier layers can also be used Apply plasma polymerization. A suitable monomer in one Low pressure plasma excited and on the plastic surface to be treated deposited. Through a suitable choice of material, hydrophilic or hydrophobic layers are generated. In contrast, fluorination or sulfonation gives basically hydrophilic barrier layers, which are permeable to hydrophobic fluids Reduce. All of the methods mentioned are additional treatment steps, the additional costs  and require additional process effort. They also deliver on complex Surface designs or in hollow bodies sometimes unsatisfactory results.

The invention is therefore based on the object, with little process effort Associated method for producing a molded plastic part with a To provide a diffusion barrier layer. Furthermore, through the procedure manufactured plastic molded parts are made available.

This object is achieved by a method having the features of claim 1 and a Plastic molding according to claim 10 solved.

The method according to the invention provides that before the plastic mass is introduced in the molding space at least one diffusion barrier layer on at least one of the two the mold surfaces of the tool halves which delimit the mold space are applied and the diffusion barrier layer with the subsequently introduced plastic mass combines.

In this way, the plastic molded part already receives its actual Manufacturing process a diffusion barrier layer. Conventional post-processing steps such as offline fluorination, plasma polymerization or lamination are no longer necessary. This will make it Process simplified and less expensive. In addition, the use of common tools possible, so that the inventive method in already existing Manufacturing processes can be integrated using already made tools can. A suitable choice of a material for the diffusion barrier layer allows one wide range of blocking effects, for example against polar or non-polar Generate fluids.

According to an advantageous embodiment of the method, the diffusion barrier layer applied in particular by spraying onto the tool surface / s. This can particularly advantageous in the form of a drying lacquer, a dispersion lacquer or a curing powder. Here, silicate paints or polyamide powder paints have become emphasized particularly suitable.

According to an alternative embodiment of the method, the diffusion barrier layer is treated as one Already largely intrinsic layer applied to the tool surface. there can be laid on as an already preformed body (preform) or as one not preformed film is placed on the tool surface, deep drawn or pressed.  

The preform or the film can also be a composite material consisting of several Include layers of the same and / or different materials. Eligible Materials are all kinds of plastics, especially with metallocene catalysts manufactured polyethylene (PE-Me), plastics with metallic components, for example metallized plastic films and / or completely metallic materials. Between the individual layers and / or on the plastic introduced facing side of the diffusion barrier layer can be adhesion-promoting layers be provided.

The molded plastic part according to the invention is characterized by at least one in front the introduction of the plastic mass into the mold space on at least one of the two Tool surfaces of the mold halves that define the mold space and are applied with the introduced plastic mass connected diffusion barrier layer.

The molded plastic part according to the invention can be particularly advantageous as a fuel tank or be formed as part of a fuel tank, the fuel tank in the so-called partial shell or full shell construction can be carried out.

Other advantageous embodiments of the invention are the subject of the rest Dependent claims.

The invention is described below in exemplary embodiments on the basis of the associated Drawings explained in more detail. Show it:

Fig. 1 is a schematic sectional view of a tool, the method steps for producing a plastic molded part according to an embodiment of the invention using the example of an injection mold for producing tank half-shells and

Fig. 2 shows a process step according to another embodiment of the invention.

Fig. 1 shows in a schematic representation of four process steps for producing a plastic molding, wherein in accordance with a diffusion barrier layer is applied as a sprayed layer on a tool surface of a first advantageous embodiment of the invention. In step A, the injection mold, which consists of two mold halves, the mold-side mold half 10 and the injection-side mold half 12 , is in an open state. The two inner tool surfaces 14 , 16 are designed such that they represent a negative shape of the plastic molded part 32 to be produced in the closed state. The injection-side tool half 12 is also equipped with an injection opening 18 . By means of a retractable between the tool halves 10, 12 spray device 20 of the form-locking mold half 10 is sprayed, a diffusion barrier layer 22 on the tool surface fourteenth For this purpose, the spray device 20 is equipped with appropriately distributed openings from which the layer material exits in the form of a paint and / or powder aerosol 24 and is deposited on the tool surface 14 . In a modification of the variant shown, the surface 16 of the injection-side tool half 12 or both tool surfaces 14 , 16 can also be coated. In addition, a successive application of a plurality of identical or different layers is conceivable, it being possible in particular for an adhesion-promoting layer to be applied to the side of the diffusion barrier layer 22 facing the injected plastic compound 30 . Various areas of the tool surfaces 14 , 16 , in particular edge areas, can be shaded by stenciling particularly advantageously during the spraying process, so that there is no deposition of the paint or powder 24 on these areas. After the spraying process has ended, the spraying device 20 is moved out of the tool 10 , 12 and the tool is closed.

FIG. 1B shows the subsequent injection process, with the mold closed 10, 12. A mold space 26 can be seen here, which is delimited by the surfaces 14 , 16 of the two tool halves 10 , 12 . A nozzle 28 of a treatment facility, not shown further for plastic molding materials is mounted on the injection port 18 of the tool half 12, and a flowable plastic mass 30, in particular a melt of a thermoplastic resin, is injected through the injection opening 18 into the mold space 26th FIG. 1B shows the partially filled with the plastic mass 30 form chamber 26. The plastic compound 30 is preferably injected after the diffusion barrier layer 22 has completely dried or cured. In certain cases, however, it may also make sense to inject before the barrier layer 22 has completely set, for example to increase the adhesive strength between the barrier layer 22 and the plastic 30 . The tool 10 , 12 is repaired in the area where the mass emerges from the nozzle in such a way that the barrier layer is not damaged during the filling. After the mold space 26 ( FIG. 1C) has been completely filled, the plastic mass 30 solidifies (cools), which bonds with the diffusion barrier layer 22 . After the plastic compound 30 has solidified, the tool 10 , 12 is opened and the finished plastic molded part 32 - consisting of the plastic carrier body 34 and the diffusion barrier layer 22 connected to it - is demolded ( FIG. 1D). For this purpose, a removal device 36 can be moved into the opened tool 10 , 12 and the plastic molded part 32 can be captured and removed with suction or gripping attachments 38 of the removal device 36 . The tool 10 , 12 is now available - optionally after cleaning - for a further process cycle.

Fig. 2 shows an alternative embodiment of the method, wherein the diffusion barrier layer 22 as an already preformed layer (preform) inserted into the tool 10, 12. The preformed diffusion barrier layer 22 can also be formed from a film made of a suitable plastic material, but also as a purely metallic body. It is also conceivable to use multilayer films, so-called composite films, with layers of the same or different materials. Suitable materials are plastics, possibly with metallic components, for example metallized plastic foils. The diffusion barrier layer 22 can be preformed, for example, in pressing or deep drawing tools. As shown, it can then be gripped with the aid of an insertion device 40 equipped with gripping or suction attachments 42 and inserted into the opened tool 10 , 12 . According to a variant of the method that deviates from the illustration, a diffusion barrier layer 22 , which is designed as a thin film and is not preformed, can also be inserted into the mold halves 10 , 12 and, if necessary, deep-drawn or pressed there. On the side facing the plastic compound 30 to be injected, the preformed or non-preformed film for the diffusion barrier layer 22 can have an adhesion-promoting layer to improve the connection with the plastic compound 30 . The process step shown in FIG. 2 is followed in a conventional manner by the injection of the plastic melt 30 , the solidification and the removal of the plastic molded part 32 in accordance with the process steps shown in FIGS. 1B to D.

The process sequence shown in FIGS. 1 and 2 has been described using the injection molding process. Analogously, the method according to the invention can also be applied to other manufacturing methods, for example deep drawing, compression molding, foaming or blowing.

The layer thickness of the diffusion barrier layer 22 is typically in the μm to mm range and is therefore generally less than the layer thickness of the carrier layer 34 . Basically, the selection of the material for the diffusion barrier layer 22 is to be matched to the barrier behavior to be achieved and to a connectivity with the carrier material, that is to say with the injected plastic compound 30 . In contrast, the material for the plastic carrier body 34 is to be designed with regard to the desired material properties of the finished plastic product, such as hardness, bursting behavior, tensile modulus, impact resistance, density, etc. For example, compliance with the approval conditions for plastic tanks for motor vehicles must be checked in standardized drop and burst tests.

LIST OF REFERENCE NUMBERS

10

mold-side mold half

12

injection side mold half

14

tool surface

16

tool surface

18

Injection port

20

sprayer

22

Diffusion barrier layer

24

Aerosol paint or powder

26

cavity

28

jet

30

Plastic compound

32

Plastics molding

34

Plastic carrier body

36

removal device

38

Griffin approaches

40

loading device

42

Gripping or suction attachments

Claims (11)

1. A method for producing a plastic molded part, wherein a flowable plastic mass is introduced into a mold space formed by two mold halves and, after the plastic mass has solidified, the tool is opened and the molded part is removed from the mold, characterized in that before the plastic mass ( 30 ) is introduced the molding space ( 26 ) at least one diffusion barrier layer ( 22 ) is applied to at least one of the two tool surfaces ( 14 , 16 ) of the tool halves ( 10 , 12 ) delimiting the molding space ( 26 ) and the diffusion barrier layer ( 22 ) with the plastic material ( 30 ) connects. 2. The method according to claim 1, characterized in that the diffusion barrier layer ( 22 ) is sprayed onto the at least one of the two tool surfaces ( 14 , 16 ). 3. The method according to any one of claims 1 or 2, characterized in that the diffusion barrier layer ( 22 ) is applied in the form of a lacquer, a dispersion or a powder ( 24 ). 4. The method according to claim 1, characterized in that the diffusion barrier layer ( 22 ) is placed as a preform on the tool surface ( 14 , 16 ) or inserted, drawn or pressed as a film on the tool surface ( 14 , 16 ). 5. The method according to claim 4, characterized in that the preform or the Foil one or more layers of the same and / or different materials includes. 6. The method according to any one of claims 4 or 5, characterized in that the Preform or the film a plastic layer, especially with metallocene Catalysts made of polyethylene (PE-Me), and / or plastics with metallic Components and / or a metal layer and / or an adhesion-promoting layer includes.   7. The method according to any one of the preceding claims, characterized in that the diffusion barrier layer ( 22 ) is applied when the tool ( 10 , 12 ) is open or closed. 8. The method according to any one of the preceding claims, characterized in that the introduction of the plastic mass ( 30 ) takes place after partial or full hardening of the diffusion barrier layer ( 22 ). 9. The method according to any one of the preceding claims, characterized in that before the introduction of the plastic compound ( 30 ) an adhesion-promoting layer is applied to the side of the diffusion barrier layer ( 22 ) facing the plastic compound ( 30 ). 10. plastic molded part, produced by introducing a flowable plastic mass into a mold space formed by two mold halves, solidifying the plastic mass and demolding the plastic molded part from the opened mold, characterized by at least one before the plastic mass ( 30 ) is introduced into the mold space ( 26 ) on at least one of the two tool surfaces ( 14 , 16 ) of the tool halves ( 10 , 12 ) delimiting the mold space ( 26 ) and connected to the introduced plastic compound ( 30 ) diffusion barrier layer ( 22 ). 11. Plastic fuel tank according to claim 10 executed in partial or shell Full monocoque construction.