FR3067965B1 - PROCESS FOR PRODUCING AN INJECTED PIECE - Google Patents

Abstract

The method comprises the following steps: depositing a coating (1) on a first face (3) of a transparent layer (5); - partial cooking of the coating (1); injecting a portion (17) of a plastic material onto a second face (19) of the transparent layer (5) opposite to the first; - complete cooking of the coating (1). The protective film (11) is placed on the coating (1) before the injection step, the injection step being carried out with the protective film (11) on the coating (1).

Description

The invention relates generally to the manufacture of injected parts.

More specifically, the invention relates to a method for manufacturing an injected part, of the type comprising the following steps: depositing a coating on a first face of a transparent layer; - partial cooking of the coating; injecting a part made of a plastic material onto a second face of the transparent layer opposite to the first; - complete baking of the coating. US 2007/0160831 discloses such a method. In some cases, the coating may stick to the injection tool. This is because the coating is not fully fired before the injection step and retains a partially liquid texture. During the injection step, the pressure inside the injection tool is very high, so that the coating layer is strongly pressed against the injection tool. At the time of demolding, particles of the coating may remain adhered to the injection tool, so that the coating layer does not have the required quality.

In this context, the invention aims to provide a manufacturing process to ensure a better quality. To this end, the invention relates to a manufacturing method of the aforementioned type, characterized in that a protective film is placed on the coating before the injection step, the injection step being performed with the film protection on the coating.

Thus, the coating is not directly pressed against the injection tool during the injection step. It is between the transparent layer on one side and the protective film on the other side. This is the protective film that bears against the inner surface of the injection tool. Thus, there is no longer any risk that the coating is damaged during the injection step, despite the high pressure inside the tool cavity during injection.

Another possibility would be not to use a protective film but to complete the firing of the coating before the injection step.

As a result, the coating would be fully cured before introduction into the injection tool. The risk of sticking the coating layer on an inner surface of the injection tool would be completely eliminated.

This alternative method has the defect that the injection pressure can cause cracks in the cured coating layer. This is due to the fact that the 100% baked coating loses its surface softness. Microcracking can generate polluting particles that settle on the surface of the parts injected later in the same mold. This results in a significant scrap rate. Microcracking also contributes to weaken the transparent layer, and generates a loss of protection vis-à-vis hydrocarbons, creams, etc ...

The manufacturing process may also have one or more of the following characteristics, considered individually or in any technically possible combination: the coating is an anti-glare varnish; the coating is of a polyolefin, polyurethane or acrylic nature; the protective film is placed on the coating in the coating deposition step; the protective film is at least partially transparent to ultraviolet rays and / or infra-red radiation; the method comprises a thermoforming step, between the partial firing step and the injection step, during which the transparent layer coated with the coating and the protective film is thermoformed; the method comprises a cutting step, between the partial firing step and the injection step, during which the transparent layer coated with the coating and the protective film is cut; - Partial cooking and / or complete cooking are performed by ultraviolet rays; in the injection step, the plastic material is injected at a pressure greater than 300 bar. - The protective film is held in place on the part until its final fixing in the vehicle, before being permanently removed. Other features and advantages of the invention will emerge from the detailed description given below, by way of indication and in no way limiting, with reference to the appended figures among which: FIGS. 1 to 6 represent successive steps of the method manufacturing of the invention; and - Figure 7 schematically shows the structure of the injected part obtained by the method of the invention.

The process shown in Figures 1 to 6 is provided for the manufacture of an injected part. This injected part is typically intended to be integrated into the passenger compartment of a vehicle, for example a motor vehicle such as a car or a truck.

The injected part is for example a component of the cap of a vehicle dashboard, or an element of the lining of an opening, or a component of a central console, or is a decorative element intended to be integrated on any other structure of the passenger compartment.

The method comprises a step of depositing a coating 1 on a first face 3 of a transparent layer 5 (see FIG. 1).

The transparent layer 5 is intended to cover the visible side of the injected part. It is transparent, in the sense that it transmits at least 90% of the visible light.

The transparent layer 5 is in any suitable material. Typically, it is made of a plastic material such as polycarbonate or PET. The transparent layer 5 typically has a thickness of between 30 .mu.m and 1000 .mu.m, preferably between 50 .mu.m and 500 .mu.m, more preferably between 100 .mu.m and 300 .mu.m.

The coating 1 is deposited on the first face 3 of the transparent layer, this first face 3 being intended to be turned towards the outside of the room, typically to the passenger compartment of the vehicle.

The coating 1 is deposited in the uncured state. In this state, the coating 1 is deformable, and has a viscous consistency.

The coating 1 is typically a crosslinkable coating.

The coating 1 is for example of a polyolefin, polyurethane or acrylic nature.

The coating 1 is for example an antireflection varnish, or a protective coating against mechanical or chemical attack of the transparent layer, or a decorative coating, etc.

Typically, the coating 1 is transparent.

The coating 1 is for example deposited on the first face 3 and then distributed on this face 3. It is for example deposited in several layers.

This operation is typically carried out continuously at a deposition station 8. The transparent layer 5 continuously travels at the deposition station 8. The coating 1 is deposited on the first face 3 by a not shown head, and spread over the first face 3 by a roll 9 of the "roller coating" type.

Alternatively, the coating 1 is laminated on the first face 3 in the form of a preformed sheet.

After deposition, the coating 1 forms a layer covering substantially the entire first face 3, and having for example a thickness of between 1 μm and 250 μm, preferably between 5 μm and 100 μm, and more preferably between 10 μm and 50 μm. .

According to the invention, a protective film 11 is placed on the coating 1 before the injection step.

The protective film is for example a material such as PET.

It has a thickness of between 20 μm and 250 μm, preferably between 30 μm and 150 μm, more preferably between 50 μm and 100 μm.

Advantageously, the protective film 11 is placed on the coating 1 in the deposition step (FIG. 1). The protective film 11 is laminated on the coating 1.

By this is meant that the protective film 11 is initially in the form of a sheet.

The protective film 11 is deposited on the coating 1 at a laying station 12.

This station 12 is typically placed downstream of the station 8 in the direction of movement of the transparent layer 5.

The protective film 11 is initially wound around a coil 13.

As the transparent layer 5 moves to the station 12, the film 11 is unwound, and is placed on the coating 1. It is pressed onto the free surface of the coating 1 by a plating roll 15.

Typically, the protective film 11 covers the entire surface of the coating 1.

The method preferably further comprises a step of partially curing the coating 1 (see FIG. 2).

This step occurs after the deposition step, and after the placement of the protective film 11.

Typically, the partial cooking is carried out by ultraviolet rays.

In this case, the protective film 11 is chosen to let the ultraviolet rays pass, at least partially.

Alternatively, the partial cooking is performed by heating, or by any other suitable means. The partial cooking step aims to partially solidify the coating 1. Typically, this is achieved by partial crosslinking of the material constituting the coating. However, the cooking is stopped before complete stiffening of the coating 1, so as to keep the coating layer 1 good formability.

Advantageously, the method comprises a thermoforming step (FIG. 3), after the partial cooking step.

During this step, the transparent layer 5 coated with the coating 1 and the protective film 11 is thermoformed.

By this is meant that at least part of the coated clearcoat 5 is hot deformed. This step aims to give the transparent layer 5 its final shape or a shape close to its final shape.

Advantageously, the method also comprises a cutting step (FIG. 4) after the partial cooking step.

Typically, this cutting step is performed after the thermoforming step, when the method comprises such a step.

During the cutting step, the transparent layer 5 coated with the coating 1 and the protective film 11 is cut. Portions of the coated clearcoat are removed to provide the coated clearcoat with the appropriate shape and extent.

The method also comprises a step of injecting a portion 17 of plastic material onto a second face 19 of the transparent layer 5, opposite to the first (FIG. 5).

This injection step occurs after the partial firing step of the coating 1. It typically occurs after the thermoforming step and / or the cutting step, if necessary.

Part 17 made of plastic is rigid, and gives a stable shape to the injected part. It is for example PC, PC + ABS or PC + ABS reinforced with fiberglass. The injection step is performed with the protective film 11 on the coating 1. The injection step is typically performed in an injection tool, not shown, having a cavity whose shape corresponds to the desired shape for the injected part.

The transparent layer 5, carrying the coating 1 and the protective film 11, is placed in the cavity, the protective film being in contact with the inner surface of the cavity. The plastic is then injected into the cavity.

The plastic is injected at a pressure greater than 300 bar, for example between 500 bar and 1500 bar.

The plastic fills the free portion of the cavity, and strongly urges the protective film 11 against the inner surface of the cavity. The state of the part, after extraction from the injection tool, is shown in FIG.

The method also comprises a complete firing step of the coating 1 (see FIG. 6).

This step occurs after the injection step. The complete firing step is preferably carried out by ultraviolet rays, such as the partial firing step.

This complete firing step makes it possible to completely harden the coating 1. Typically, this corresponds to complete crosslinking of the material constituting the coating.

Preferably, the complete cooking is carried out with the protective film 11 in place on the coating 1.

This is possible because the protective film 11 at least partially passes ultraviolet rays.

Alternatively, the complete cooking is carried out by heating, or by any other means.

It should be noted that the protective film 11 is intended to be able to peel off after the complete cooking step.

It is typically taken off after the injected part has been put in place permanently in the vehicle.

The protective film 11 is chosen so as to resist the injection step without modifying the optical quality of the part, that is to say the homogeneity of the gloss and the surface roughness. It should also be noted that the gloss of the coating is defined by the gloss of the protective film by duplication of the contact surface. In this way, it is possible to adjust the specular reflection ratio of the surface by the surface roughness of the protective film

Thus, at the end of the manufacturing process of the invention, the injected part comprises, as illustrated in FIG. 7, the plastic part 17 covered by the transparent layer 5, itself covered by the coating 1, covered himself by the protective film 11.

The manufacturing method of the invention may have multiple variants.

It may not include the thermoforming step, and / or the cutting step.

The alternative protective film is not placed on the coating at the coating deposition step, but after the partial firing step, or even after the thermoforming step or the cutting step.

Claims (10)

1. - A method of manufacturing an injected part, the method comprising the following steps: depositing a coating (1) on a first face (3) of a transparent layer (5); - partial cooking of the coating (1); injecting a portion (17) of a plastic material onto a second face (19) of the transparent layer (5) opposite to the first; - complete baking of the coating (1); characterized in that a protective film (11) is placed on the coating (1) before the injection step, the injection step being carried out with the protective film (11) on the coating (1) . 2. - Method according to claim 1, characterized in that the coating (1) is an antireflection varnish. 3. - Method according to claim 1 or 2, characterized in that the coating (1) is of polyolefin nature, polyurethane or acrylic. 4. - Method according to any one of the preceding claims, characterized in that the protective film (11) is placed on the coating (1) in the coating deposition step (1). 5. - Method according to any one of the preceding claims, characterized in that the protective film (11) is at least partially transparent to ultraviolet rays and / or infra-red radiation. 6. - Process according to any one of the preceding claims, characterized in that the method comprises a thermoforming step, between the partial firing step and the injection step, during which the transparent layer (5) coated with the coating (1) and the protective film (11) is thermoformed. 7. - Process according to any one of the preceding claims, characterized in that the method comprises a cutting step, between the partial firing step and the injection step, during which the transparent layer (5) coated with the coating (1) and the protective film (11) is cut. 8. - Process according to any one of the preceding claims, characterized in that the partial cooking and / or complete cooking are carried out by ultraviolet rays. 9. - Method according to any one of the preceding claims, characterized in that in the injection step, the plastic material is injected at a pressure greater than 300 bar. 10. A process according to any one of the preceding claims, characterized in that the protective film (11) is laminated (9) on the coating (1).