Body panel molding process

Abstract

The invention relates to a method for molding a body panel (2) comprising at least one decorative pattern made on a film (4), the method comprising the following steps: Placing the film (4) in a mold (10), First molding of a first portion (20) of the body panel (2) made of polycarbonate transparent to visible light, the temperature of the mold (14) being at reinforced thermal regulation at a wall in contact with the film, Replacing one half of the mold (14) with another half of the mold (26), Second molding of a second portion (24) of the body panel (2) to encapsulate the film (4) in the body panel (2) using a second thermoplastic material chemically compatible with polycarbonate transparent to visible light and injected at a temperature lower than the injection temperature of the first portion (20) of the body panel (2). Abstract figure: figure 1

Description

Title of the invention: Body panel molding method

[0001] The invention relates to a method of molding body panels, more precisely to that of molding a body panel including a film overmolded in a main body, the film bearing at least one decorative pattern.

[0002] With a view to personalizing motor vehicles, it is known to produce body panels comprising one or more decorative motifs visible from the exterior of the vehicle.

[0003] It is known to encapsulate a decorative film in a main body forming a body panel, the decorative film being visible through the main body which is partly transparent to visible light. Such a method is for example disclosed by patent application FR 3 104 092 A1.

[0004] Given the desire to ensure that the body panel has satisfactory impact resistance, molding constraints may apply. For example, and in the context of the use of polycarbonate to form the main body of the body panel, it is necessary to carry out injection molding of the polycarbonate at a temperature which may be between 250°C and 270°C, and which may even exceed 280°C. The term “injection temperature” means the temperature of the plastic material injected at the outlet of the injection nozzle. This molding temperature makes it possible to obtain optimal impact resistance of the body panel, for example so that the latter complies with the impact resistance capabilities of a body panel fitted to a commercially available motor vehicle.

[0005] However, a high molding temperature can pose a problem for preserving the integrity of the decorative pattern(s) carried by a decorative film. Indeed, the decorative pattern(s) can be produced by depositing a material on the decorative film. This can, for example, be an ink deposited by screen printing or by inkjet. It can also be a deposit of indium to obtain one or more decorative patterns transparent to radar waves in the case where these decorative patterns are located in one or more areas of the body panel crossed by such waves.

[0006] A molding temperature above 250°C can lead to deterioration of the decorative pattern(s). For example, indium has a melting temperature well below 300°C, of ​​the order of 170-180°C. When the decorative film is overmolded with polycarbonate injected at a temperature above approximately 250°C, it is possible to reach the strength limit of the material(s) forming the decorative patterns, which can lead to deterioration of the visual appearance of the latter. This is therefore referred to as a washing effect of the decorative patterns (modification of the shape of the decorative pattern(s)). decorative by moving them or even reducing the intensity of their color).

[0007] It would be possible to reduce the injection temperature of polycarbonate. However, and for body panels which form large parts, this is not possible because: - too low a temperature could lead to molding problems and appearance defects in the molded part (mold filling defects, variations in thickness of the molded panels, and - a decrease in the molding temperature would lead to leaving the injection temperature window providing optimal impact resistance of the molded part, as explained above. This would therefore lead to a decrease in the desired mechanical properties of the molded part in terms of impact resistance.

[0008] The invention aims in particular to provide a method for molding a bodywork panel incorporating a decorative film comprising one or more decorative patterns as described above, the bodywork panel retaining satisfactory mechanical properties while avoiding degradation of the decorative patterns during molding.

[0009] To this end, the invention relates to a method for molding a bodywork panel made of two thermoplastic materials encapsulating at least in part a film comprising at least one decorative pattern made by depositing a material on at least one face of the film, the method comprising the following steps: - Placing the film in a mold, a first part of the film being arranged opposite a first cavity of the mold formed in a first half of the mold, and a second part of the film being pressed against the wall of a second half of the mold, - First molding of a first portion of the body panel by injection, in the first cavity of the mold, of polycarbonate transparent to visible light, this first portion overmolding the first part of the film, the temperature of the second half of the mold, lower than the injection temperature of the polycarbonate, being at reinforced thermal regulation at the level of the wall in contact with the film, - Replacing the second half of the mold with a third half of the mold, and placing the second part of the film opposite the second cavity of the mold formed in the third half of the mold, and - Second molding of a second portion of the body panel to encapsulate the film in the body panel by overmolding the second part of the film, the second portion being made by injecting, into the second cavity of the mold, a second chemically thermoplastic material compatible with polycarbonate transparent to visible light, the second injection being carried out at a temperature lower than the injection temperature of the first portion of the body panel.

[0010] Thus, the first molding is that of a polycarbonate transparent to visible light (to allow the decorative patterns present on the film to be viewed). This makes it possible to apply a molding temperature of the order of those mentioned above to obtain the desired mechanical properties (i.e. satisfactory impact resistance). During this first molding, the film is pressed against the wall of a mold half cooled in a reinforced manner. This pressing on an area of ​​the wall with thermal regulation by reinforced cooling makes it possible to reduce the temperature of the film due to the local temperature difference between the mold and the injected polycarbonate transparent to visible light, and therefore to avoid heating of the film which could lead to degradation of the decorative patterns.

[0011] During the second molding, the film is no longer in contact with any mold wall. On its first face, it is distant and isolated from the first half of the mold by the thickness of polycarbonate already overmolded. On its second face, the second thermoplastic material used is injected at a temperature lower than that of the polycarbonate, which protects the decorative pattern(s). The chemical compatibility with the polycarbonate transparent to visible light ensures the production of a body panel with optimal chemical adhesion between the materials forming it.

[0012] “Transparent” means a material having a light transmission of between 80% and 99%. “Chemically compatible” means a material capable of creating chemical adhesion, in particular under the effect of the molding temperature, adhesion retained after cooling of the body panel.

[0013] Reinforced thermal regulation means a capacity to cool the second half of the mold during the first molding, beyond more conventional thermal regulation. Indeed, a conventional mold is thermally regulated to be generally at a temperature between 80°C and 120°C, for example substantially equal to 100°C. In the present case, and to protect the decorative pattern(s), the reinforced thermal regulation makes it possible to reduce, at least locally in the immediate vicinity of the film, the temperature so that it is between 30°C and 50°C, for example substantially equal to 40°C.

[0014] “Part of the film” means any fraction of the latter in connection with the faces of the film. This may be a portion of one face of the film or several areas of several faces of the film, or even one or more complete faces of the film.

[0015] According to other optional characteristics of the molding process taken alone or in combination: - the film comprises a main body made of polycarbonate; - the polycarbonate transparent to visible light is injected at a temperature between 270°C and 300°C, preferably between 280°C and 300°C; - the second thermoplastic material is injected at a temperature between 220°C and 250°C, preferably between 230°C and 240°C; - the second material is chosen from thermoplastic polyurethanes or thermoplastic elastomers; - the at least locally thermally regulated mold half comprises a fluid circuit, a temperature regulating fluid circulating inside the fluid circuit during the first molding; and - the decorative pattern is made using a material chosen from ink, indium or varnish. Brief description of the figures

[0016] The invention will be better understood on reading the following description given solely by way of example and with reference to the appended drawings in which:

[0017] [Fig. 1] is a schematic representation of the first molding of the molding method according to the invention, and

[0018] [Fig.2] is a schematic representation of the second molding of the molding method according to the invention.

[0019] The figures being schematic representations, the shapes of the different elements or even the sizes of these elements, independently or in relation to each other, are produced for the purposes of illustration without reflecting the reality of a body panel. Detailed description

[0020] We now refer to [Fig. 1] illustrating a first molding of a bodywork panel 2 made of two thermoplastic materials at least partially encapsulating a film 4 comprising at least one decorative pattern (not illustrated) made by depositing a material on at least one face of the film 4.

[0021] One of the two thermoplastic materials used is polycarbonate transparent to visible light. The use of the latter makes it possible to obtain the mechanical properties stated above thanks to the molding temperature stated above, and to be able to visualize the decorative pattern. It is therefore understood that the polycarbonate transparent to visible light forms the part of the body panel 2 visible from the outside of a motor vehicle when it is mounted on a motor vehicle.

[0022] The second thermoplastic material is a thermoplastic material chemically compatible with polycarbonate (definition given above) and capable of being molded at a temperature lower than the molding temperature of polycarbonate. transparent to visible light for the aforementioned purpose of protecting the decorative motif.

[0023] Advantageously, the second thermoplastic material is injected at a temperature between 220°C and 250°C, preferably between 230°C and 240°C.

[0024] The second thermoplastic material is advantageously chosen from thermoplastic polyurethanes or thermoplastic elastomers. These materials can be molded at a temperature lower than that of molding the first portion of the body panel 2 in order to avoid any degradation of the decorative pattern(s) as explained above.

[0025] The use of thermoplastic elastomers is preferred because the latter are more flexible than thermoplastic polyurethanes. This flexibility prevents tension from being exerted on the polycarbonate transparent to visible light after shrinkage of the second thermoplastic material. "Shrinkage" means the contraction of the plastic material as it cools. Thermoplastic polyurethanes and thermoplastic elastomers have a greater shrinkage than that of polycarbonate transparent to visible light. In other words, thermoplastic elastomers, due to their flexibility, will not exert stress on the polycarbonate transparent to visible light that could affect the body panel 2, for example its shape by excessively curving it.

[0026] The film 4 advantageously comprises a main body also made of polycarbonate. It therefore withstands high molding temperatures, of the order of those of polycarbonate transparent to visible light.

[0027] At least one decorative pattern is produced on the film 4 by depositing a material on at least one face of the latter. The decorative pattern may for example be produced on a first face 6 and / or a second face 8 of the film 4, covering all or part of the latter. The decorative pattern may be made of a material chosen from an ink, indium or a varnish. As explained above, such materials have a temperature resistance limit below an optimal molding temperature of polycarbonate transparent to visible light.

[0028] The first step of the molding method consists of placing the film 4 comprising at least one decorative pattern in a mold 10. The film 4 comprises at least a first part, here the first face 6, arranged opposite a first cavity of the mold 10, here formed in a first half of the mold 12 and at least a second part, here the second face 8, pressed against a wall of the mold 10, here a wall of a second half of the mold 14. It will be noted here that lateral faces 16 and 18 of the film 4 are also arranged opposite the first cavity formed in the first half of the mold 12. Of course, the number of faces (and the fraction of each face) pressed against a wall of the mold 10 can vary from one case to another. It would be by possible example of pressing only a part of the second face 8 of the film 4 against the second half of the mold 14 (which would then take a shape allowing this pressing).

[0029] After the film 4 has been placed in the mold 10, the first molding of a first portion 20 of the bodywork panel 2 is carried out by injection of polycarbonate transparent to visible light, this first portion 20 overmolding the first part of the film 4 formed by the first face 6 and the lateral faces 16 and 18 (i.e. the part not pressed against a face of the second half of the mold 14), the second part of the film 4 formed by the second face 8 not being overmolded because pressed against a wall of the mold 10, here of the second half of the mold 14.

[0030] Advantageously, the polycarbonate transparent to visible light is injected at a temperature between 270°C and 300°C, preferably between 280°C and 300°C. This injection temperature makes it possible to obtain optimal mechanical properties, in particular impact resistance.

[0031] The decorative pattern is advantageously produced on the first face 6 and / or the second face 8 of the film 4, on all or part of the latter. In the case where the second face 8 of the film 4 alone carries one or more decorative patterns (or if the decorative pattern(s) are carried by faces or fractions of faces pressed against one half of the mold), the pressing against the second half of the mold 14 makes it possible to protect them from the high molding temperature of the polycarbonate transparent to visible light.

[0032] In the case where the first face 6 of the film 4 carries one or more decorative patterns (or if the decorative pattern(s) are carried by faces or fractions of faces arranged opposite the first injection cavity of the polycarbonate transparent to visible light), the second half of the mold 14 ensures, thanks to the reinforced thermal regulation, the thermal regulation of the film 4 so that the latter maintains a lower temperature than that of injection of the polycarbonate transparent to visible light, making it possible to avoid washing of the decorative pattern(s).As explained above, the second half of the mold 14 makes it possible, thanks to this reinforced thermal regulation, to reduce the temperature of the second half of the mold 14 so that it is preferably between 30°C and 50°C, for example substantially equal to 40°C, and therefore to protect the decorative pattern(s) against exposure to the very high injection temperature of the transparent polycarbonate in visible light. The reinforced thermal regulation can be localized to cool only the film 4, or even only the part(s) of the film 4 bearing the decorative pattern(s), or perhaps more global and cool a larger area than that in the immediate vicinity of the film 4. The second half of the mold 14 could comprise, in addition to a device allowing reinforced thermal regulation, standard thermal regulation means for cooling the rest of the second half of the mold 14 so that a portion . of the latter uncooled to be preferably between 30°C and 50°C or cooled to be preferably between 80°C and 120°C.

[0033] [Fig.l] illustrates a zone 22 thermally regulated in a reinforced manner. Local thermal regulation is advantageously carried out as close as possible to the film 4 so that it is as effective as possible.

[0034] Preferably, the at least locally thermally regulated mold half, here the second mold half 14, comprises a fluid circuit, a temperature regulating fluid circulating inside the fluid circuit during the first molding. The fluid used is for example water. This results in simple and effective thermal regulation.

[0035] Once the first molding has been carried out, the second part of the film 4, in the example illustrated the second face 8, is released from the wall of the second half of the mold 14 against which it was pressed and is placed opposite a second cavity of the mold 10 carried by a third half of the mold 26 in which the second cavity of the mold 10 is formed, the third half of the mold 26 replacing the second half of the mold 14, the first half of the mold 12 remaining present as illustrated in [Fig. 2]

[0036] After releasing the second part of the film 4 and placing the latter opposite the second cavity of the mold 10, a second molding of a second portion 24 of the body panel 2 is carried out to encapsulate the film 4 in the body panel 2 by overmolding the second part of the film 4 (here the second face 8), the second portion 24 being produced by injection, into the second cavity of the mold 10, of the second thermoplastic material chemically compatible with the polycarbonate transparent to visible light, the second injection being carried out at a temperature lower than the injection temperature of the first portion 20 of the body panel 2.

[0037] [Fig. 2] illustrates a second molding according to the invention. The face(s), or fractions of faces, not overmolded during the first molding, here the second face 8, are overmolded during this second molding (the other faces / fractions of faces already being overmolded by the polycarbonate transparent to visible light). The second face 8 is arranged opposite a second cavity formed in a third mold half 26.

[0038] Alternatively to replacing one half of the mold with another between the two molding steps, it would be possible to use two different molds. It would then be necessary to extract the assembly formed by the first portion 20 of the body panel 2 and the film 4 from the first mold to place it in a second mold in which the second portion 24 of the body panel 2 is molded. List of references

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[0050] 2: body panel 4: film 6: first face of the film 8: second face of the film 10: mold 12: first half of mold 14: second half of mold 16, 18: side faces of the film 20: first portion of the body panel 22: thermally regulated zone 24: second portion of the body panel 26: third half of mold

Claims

Claims

1. Method for molding a body panel (2) made of two thermoplastic materials at least partially encapsulating a film (4) comprising at least one decorative pattern made by depositing a material on at least one face of the film (4), the method being characterized in that it comprises the following steps: - Placing the film (4) in a mold (10), a first part (6, 16, 18) of the film (4) being arranged opposite a first cavity of the mold (10) formed in a first half of the mold (12), and a second part (8) of the film (4) being pressed against a wall of a second half of the mold (14), - First molding of a first portion (20) of the body panel (2) by injection, into the first cavity of the mold, of polycarbonate transparent to visible light, this first portion (20) overmolding the first part (6, 16, 18) of the film (4), the temperature of the second half of the mold (14),lower than the injection temperature of the polycarbonate transparent to visible light, being with reinforced thermal regulation at the wall in contact with the film, - Replacement of the second half of the mold (14) by a third half of the mold (26), and placement of the second part (8) of the film (4) opposite a second cavity of the mold (10) formed in the third half of the mold (26), - Second molding of a second portion (24) of the body panel (2) to encapsulate the film (4) in the body panel (2) by overmolding the second part of the film, the second portion (24) being produced by injection, into the second cavity of the mold (10), of a second thermoplastic material chemically compatible with the polycarbonate transparent to visible light, the second injection being carried out at a temperature lower than the injection temperature of the first portion (20) of the body panel (2).,

2. A molding method according to claim 1, wherein the film (4) comprises a main body made of polycarbonate.

3. A molding method according to any preceding claim, wherein the polycarbonate transparent to visible light is injected at a temperature between 270°C and 300°C, preferably between 280°C and 300°C.

4. A molding method according to any one of the preceding claims, wherein the second thermoplastic material is injected at a temperature between 220°C and 250°C, preferably between 230°C and 240°C.

5. A molding method according to any preceding claim, wherein the second material is selected from thermoplastic polyurethanes or thermoplastic elastomers.

6. A molding method according to any preceding claim, wherein the at least locally thermally regulated second mold half (14) comprises a fluid circuit, a temperature regulating fluid circulating inside the fluid circuit during the first molding.

7. A molding method according to any preceding claim, wherein the decorative pattern is made by a material selected from ink, indium or varnish.

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