FR3067965A1 - 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

Method of manufacturing an injected part

The invention generally relates 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 with a transparent layer;

- partial firing of the coating;

- injection of a plastic part on a second face of the transparent layer opposite the first;

- complete baking of the coating.

US 2007/0160831 describes such a process. In some cases, the coating may stick to the injection tool. This is due to the fact that the coating is not fully cured 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 stuck to the injection tool, so that the coating layer does not have the required quality.

In this context, the invention aims to propose a manufacturing process which guarantees better quality.

To this end, the invention relates to a manufacturing process of the aforementioned type, characterized in that a protective film is placed on the coating before the injection step, the injection step being carried out with the film protective coating.

Thus, the coating is not directly pressed against the injection tool during the injection step. It is caught between the transparent layer on one side and the protective film on the other side. It is the protective film which bears against the internal surface of the injection tool. There is therefore no longer any risk of the coating being damaged during the injection step, despite the high pressure inside the tool cavity during the injection.

Another possibility would be not to use a protective film but to fully cure the coating before the injection step.

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

This alternative process has the defect that the injection pressure can cause cracks in the cured coating layer. This is related to the fact that the 100% baked coating loses its surface flexibility. Microcracks can generate polluting particles which are deposited on the surface of parts subsequently injected into the same mold. This results in a high reject rate. The microcracks also contribute to weakening the transparent layer, and cause a loss of protection with respect to hydrocarbons, creams, etc.

The manufacturing process may also have one or more of the characteristics below, considered individually or in all technically possible combinations:

- the coating is an anti-reflective varnish;

- the coating is of polyolefin, polyurethane or acrylic nature;

- the protective film is placed on the coating during the coating deposition step;

the protective film is at least partially transparent to ultraviolet rays and / or to infrared radiation;

- The method comprises a thermoforming step, between the partial cooking 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 cooking 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 carried out by ultraviolet rays;

- at the injection stage, the plastic is injected at a pressure above 300 bar.

- the protective film is held in place on the part until it is finally fixed in the vehicle, before being definitively removed.

Other characteristics and advantages of the invention will emerge from the detailed description which is given below, by way of indication and in no way limitative, with reference to the appended figures among which:

- Figures 1 to 6 show successive stages of the manufacturing process 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 intended for the manufacture of an injected part. This injected part is typically intended to be integrated into the interior of a vehicle, for example a motor vehicle such as a car or a truck.

The injected part is for example an element of the cover of a vehicle dashboard, or an element of the trim of a window, or an element of a central console, or is a decorative element intended to be integrated on any other interior structure.

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 visible light.

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

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 part, typically towards the passenger compartment of the vehicle.

The coating 1 is deposited in the uncooked 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 polyolefin, polyurethane or acrylic nature.

The coating 1 is for example an anti-reflective varnish, or a protective coating against mechanical or chemical attack by 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 depot station

8. The transparent layer 5 runs continuously at the deposition station 8. The coating 1 is deposited on the first face 3 by a head not shown, and spread on the first face 3 by a roller 9 of the "roller coating" type .

As a variant, 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 made of 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 during 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 covering 1 at an installation 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 reel 13.

As the transparent layer 5 travels through station 12, the film 11 is unwound and is placed on the covering 1. It is pressed onto the free surface of the covering 1 by a plating roller 15.

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

The method preferably also includes a partial firing step for the coating 1 (see FIG. 2).

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

Typically, 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.

As a variant, partial cooking is carried out by heating, or by any other suitable means.

The partial firing step aims to partially solidify the coating 1. Typically, this is obtained by partial crosslinking of the material constituting the coating. However, the firing 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 transparent layer 5 is deformed when hot. This step aims to give the transparent layer 5 its final shape or a shape close to its final shape.

Advantageously, the method also includes a cutting step (Figure 4), after the partial cooking step.

Typically, this cutting step is carried out after the thermoforming step, when the process includes such a step.

During the cutting step, the transparent layer 5 coated with the coating 1 and the protective film 11 is cut. Certain parts of the coated transparent layer 5 are eliminated, so as to give the coated transparent layer 5 the appropriate shape and extent.

The method also includes a step of injecting a plastic part 17 onto a second face 19 of the transparent layer 5, opposite 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 applicable.

The plastic part 17 is rigid, and gives a stable shape to the injected part. It is for example made of PC, PC + ABS or PC + ABS reinforced with glass fibers.

The injection step is carried out with the protective film 11 on the coating 1.

The injection step is typically carried out 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 internal 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 material fills the free part of the cavity, and places a strong stress on the protective film 11 against the internal surface of the cavity.

The state of the part, after extraction from the injection tool, is shown in Figure 5.

The process also includes a complete cooking step for the coating 1 (see FIG. 6).

This step occurs after the injection step.

The complete cooking step is preferably carried out by ultraviolet rays, like the partial cooking step.

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

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

This is possible because the protective film 11 allows the ultraviolet rays to pass at least partially.

As a variant, complete cooking is carried out by heating, or by any other means.

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

It is typically taken off after the injected part has been permanently installed on board the vehicle.

The protective film 11 is chosen so as to withstand the injection step without modifying the optical quality of the part, that is to say the uniformity 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 rate 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 itself by the protective film 11.

The manufacturing process of the invention can 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 in the coating deposition step, but after the partial curing step, or even after the thermoforming step or the cutting step.

Claims (10)

1. - Process for manufacturing an injected part, the process comprising the following steps: - depositing a coating (1) on a first face (3) with a transparent layer (5); - partial firing of the coating (1); - injection of a part (17) of a plastic material on a second face (19) of the transparent layer (5) opposite 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 anti-reflective varnish. 3. - Method according to claim 1 or 2, characterized in that the coating (1) is of polyolefin, polyurethane or acrylic nature. 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 to infrared radiation. 6. - Method according to any one of the preceding claims, characterized in that the method comprises a thermoforming step, between the partial cooking step and the injection step, during which the transparent layer (5) coated with the coating (1) and the protective film (11) is thermoformed. 7. - Method according to any one of the preceding claims, characterized in that the method comprises a cutting step, between the partial cooking step and the injection step, during which the transparent layer (5) coated with the coating (1) and the protective film (11) is cut. 8. - Method 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 is injected at a pressure greater than 300 bar. 10.- Method according to any one of the preceding claims, characterized in that the protective film (11) is laminated (9) on the coating (1).