JP3440537B2 - In-mold coat injection molding method and injection molding apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-mold coat injection molding method and an injection molding apparatus for simultaneously performing injection molding of a thermoplastic resin material and decorating a surface of a molded product such as painting.

Since the appearance of an injection molded product is impaired if there are pinholes, weld lines, whitening, etc. on the surface, an independent coating process is generally provided after the injection molding process, and surface decoration such as painting is performed as a secondary process. I am giving it. However, since the number of steps increases if coating is performed in an independent coating process, a method of performing surface coating at the same time as injection molding is performed, and at that time, it is desired to be able to perform clean coating without uneven coating or peeling.

[0003]

2. Description of the Related Art One conventional method is to provide a paint outlet on a mold composed of an upper mold and a lower mold, and then spray-coat the inner surface of the cavity and then injection-mold a thermoplastic resin material for simultaneous coating. is doing. Another method is to open the mold slightly while leaving the primary molded product of the resin molding material pressure-molded in the mold and leave it in the mold, and apply a predetermined amount of paint to the gap between it and the molded product. After injection, the mold is pressed again and the product is simultaneously coated.

[0004]

However, in these conventional methods, for example, when the coated surface of the molded product is not large but the surface has irregularities or holes and the shape is complicated, the former method is one in which the paint discharge port is Since the paint film is fixed to the mold, the paint film is likely to be non-uniform in a portion having a complicated shape, and uneven coating is likely to occur due to flow of the paint film due to injection pressure during injection molding.

Further, the latter method requires a high-pressure injection device for injecting the paint at a high pressure because the narrow space between the molded article and the molded product is narrow when the surface to be coated is not flat and has a complicated shape but has a large area. There is a problem that if the paint does not turn around even if it is injected, the unpainted part remains and it cannot be completely painted, or in both methods, the adhesive force of the paint film is small and the paint film is easily peeled off.

In view of the above problems, it is an object of the present invention to provide an in-mold coat injection molding method capable of simultaneously performing injection molding of a thermoplastic resin material and performing a clean surface coating without coating unevenness or peeling.

[0007]

[0008]

[Means for Solving the Problems] To achieve the above object
In the in-mold coat injection molding method of the present invention,
Uses a mold having a movable mold having a paint injection hole and a vacuum suction hole opened in each cavity inner face the fixed mold and the least even molten resin into the cavity inner surface open mold a step of cell Tsu preparative heat-resistant film that the contact surfaces coated with heat-resistant rubber adhesive, a step of adsorbing the cavity inner surface while evacuating the heat-resistant film from the vacuum suction holes, after closing the mold, It comprises a step of injecting a paint from the paint injection hole between the inner surface of the cavity of the mold and the heat-resistant film, and a step of injecting and molding a molten resin into the cavity and simultaneously decorating the molded product.

[0009]

[0010]

[0011]

[Action] key heat rubber adhesive sets heat-resistant film coated on Yabiti inner surface, a method of injection molding the injected molten resin paint between the heat-resistant film and the cavity inner surface, placed in the cavity inner surface heat Since the film is heated and softened, it is vacuum-sucked to the inner surface of the cavity while being evacuated from the vacuum suction holes, so that the film can be adsorbed without wrinkles.

Further, since the heat-resistant film is coated with a heat-resistant rubber-based adhesive in advance on at least the surface which comes into contact with the molten resin, the heat-resistant film is a molded product (or a paint when the adhesive is coated on both surfaces). The film can be strongly adhered to the film, and a predetermined amount of paint is injected between the inner surface of the mold cavity and the heat-resistant film through the paint injection hole according to the size of the paint surface, so that there is no uneven coating. The surface of the molded product can be decorated at the same time as the molding.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention will be described in detail below with reference to the embodiments shown in the drawings. The first method will be described with reference to the first and second embodiments, and the second method will be described with reference to one embodiment.

First, in the first embodiment according to the first method, a flat plate-shaped molded product 10 having a length of 50 mm, a width of 50 mm and a height of 2 mm, that is, 10-1 shown in the perspective view of FIG. Molded product 10-1
One side (paper surface side) including the side surface of is the painted surface.

As shown in the schematic side sectional view of the mold of FIG.
The mold 1 of this molded product 10-1 is composed of a movable mold 1-1 and a fixed mold 1-2 which are fitted to each other on split surfaces (parting surfaces), and is clamped in a vertical injection molding device. For a pressure mold clamping device (not shown) with a pressure of 50 tons, the fixed mold 1-2 is on the upper side, and the two movable molds 1-1 (1-1a, 1-1b) are on the lower rotary table 35. It is attached to the place, one movable mold 1-1a is fixed mold 1-
2 is rotated and moved downward, pushed up and fitted, and while performing injection molding, a predetermined pretreatment is performed on the other movable mold 1-1b.
The fixed mold 1-2 is a runner 1b for introducing the molten resin supplied from the molten resin supply device 34 to a position corresponding to the side surface of the molded product.
Vent hole 1c that communicates with the outside air for exhausting during injection molding
To the optimum position.

Next, the molding process of this molded product will be described. 3 (a), (b), (c), (d) are schematic side sectional views showing the molding step of FIG. 1 in order, and FIG. 4 is a schematic side sectional view showing the next take-out step of FIG. is there.

In the step of forming the release film shown in FIG. 3 (a), the release film is movable toward the coating area of the convex top surface 1d of the movable mold 1-1a corresponding to the coating surface of the molded product. First, a silicone-based release agent is spray-applied with a thickness of 10 to 20 μm using the agent injection device 11. The solvent in the release agent is volatilized by the heat of which the temperature of a sheath heater (not shown) incorporated in the movable mold 1-1a is adjusted to form the release film 2.

The release agent injection device 11 is a well-known device and is composed of a paint tank (not shown) and an injection nozzle with a flow rate control valve connected to high-pressure air. The release agent injection device 11 can be freely moved by a robot such as a manipulator to face a target. Apply by spraying.

Next, in the step of forming the paint film shown in FIG. 3B, a urethane resin-based paint having a thickness of 20 to 30 μm is formed on the surface of the release film 2 using the same paint spraying device 12. And the paint film 3 is laminated.

Further, in order to further strengthen the adhesion strength between the paint film 3 and the molded product, a similar nitrile rubber type resin adhesive is applied to form the adhesive film 4. The adhesive film 4 may be omitted if the adhesion strength between the paint film 3 and the molded product can be secured.

In the semi-curing process of the coating film shown in FIG. 3 (c),
The heat of the heating means 13 (for example, the temperature control heat of the movable mold 1-1 and
The solvent in the paint film 3 is volatilized by the radiant heat of the far-infrared heating device or the convection heat of the hot air heating device to bring the paint film 3 into a semi-cured state that does not flow. The adjustment temperature of the movable mold is about 70 ° C, the temperature of the heating device is about 130 ° C, and the heating time is about 3 minutes.

In the injection molding process shown in FIG. 3D, the movable mold 1-1a is closed to the fixed mold 1-2 and the molten resin 14 supplied from the molten resin supply device 34, that is, the ABS resin is injected. To do. The coating film 3 is activated by the heat of the molten resin 14 at a high temperature, and the coating film 3 and the molten resin 14 are pressed against each other in the cooling process by the holding pressure by a mold clamping pressure device (not shown).

The injection molding condition is that the resin temperature is about 220
℃, mold temperature about 70 ℃, injection pressure about 1500kgf / cm ² . In the process of taking out the molded product of FIG. 4, after the pressure holding and cooling, the mold 1 is opened and the molded product 10 whose surface is decorated with the paint film 3
Take out -1. The molded product 10-1 is coated with the area shown in the figure in a checkerboard pattern and is discharged.

Although the first method can easily coat a molded product having a simple shape as in the first embodiment, as shown in the perspective view of the second embodiment of the first method of FIG. Article 10
-2 is particularly effective in the case of a complex shape having a circular hole 10a and a concavo-convex portion 10b on a part of the coating surface and having a small roundness (rounded portion 10c) on the ridgeline.

In this case as well, the surface of the molded article is cleaned by the same steps as those in the first embodiment, that is, the steps of forming the release film and the coating film, the semi-curing step of the coating film, and the injection molding step. It can be injection molded and painted at the same time. However, the spray coating in each process of forming the release film and the paint film should be carefully done by accurately directing the injection device (nozzle) to the complicatedly shaped local part such as the hole 10a and the uneven part 10b so that there is no coating unevenness. To do.

The first method according to the first method described above,
In the second embodiment, a portion which does not need to be coated or a portion which should not be attached is hidden and coated with a mask. A cross-cut test was performed on the molded article coated by the first method to evaluate the adhesion of the coating film. 100 squares of 5mm square were created at any place of the molded product, and the result of the peeling test by forcing the adhesive tape and 100/100
Therefore, there was no peeling of the paint film and sufficient adhesion was obtained.

In particular, the angular portion of the outer shape of the first embodiment (corner portion 10b shown in FIG. 1), the hole portion of the second embodiment, the uneven portion and the ridge rounded portion (the hole portion 10a shown in FIG. 5, the uneven portion). Part 10b,
It was confirmed that the rounded portion 10c) was also painted well with good adhesion.

In this way, the mold release film and the paint film are preliminarily laminated on the inner surface of the cavity of the mold corresponding to the coated surface of the molded product, and the molten resin is injection-molded in the semi-cured state to thereby perform injection molding. There is no flow of the paint film due to the injection pressure at the time, the paint film is activated by the high-temperature molten resin, and the injection pressure puts it in a pressure-pressed state, so the paint film and the molded product are pressed and do not peel off. High adhesion can be obtained.

In particular, since the coating is performed using a movable spraying device, even if the coating surface of the molded product has a complicated shape with irregularities, holes, etc., it is possible to precisely and carefully apply it to the local area. It is possible to obtain a uniform and clean painted surface without uneven coating.

Further, since the release film is interposed, the coating film is well separated and does not remain on the inner surface of the cavity. Furthermore, considering the degree of adhesion between the paint film and the molded product, if necessary, a heat-resistant rubber adhesive is further laminated and applied on the paint film to further strengthen the adhesion strength between the paint film and the molded product. be able to.

Next, the second method will be described. This second
The method of (1) is effective for a dish-shaped molded product having a relatively large surface and a relatively large surface and a flat surface without a complicated shape. For example, as shown in the perspective view of Fig. 6, length 250mm x width 350mm x height
Molded product 10 that covers the 20 mm electronic device housing, ie 10
A case of coating the surface area (paper surface side) including the side surface of -3 will be described as an example.

As shown in the schematic side sectional view of the mold and the injection molding apparatus of FIG. 7, the mold 21 of this molded product has a movable mold 21-1 and a fixed mold 21-2 which are fitted to each other at a split surface. The movable mold 21-1 is mounted on the left side and the fixed mold 21-2 is mounted on the right side of a pressure mold clamping device with a mold clamping pressure of 50 tons of a horizontal injection molding device (not shown).

The movable die 21-1 has a cavity 21a with an inner surface 1
Gate 21a-2 branching from runner 21a-1 at one location to two locations
Equipped with multiple paint injection holes 21b and multiple vacuum suction holes 21c.
And open.

The runner 21a-1 is connected to the molten resin supply device 34, the paint injection hole 21b is connected to the paint supply device 31, and the vacuum suction hole 21c is connected to the vacuum exhaust device 32. The paint injection hole 21b and the vacuum suction hole 21c should be
21a A flow control valve (not shown) having a needle core that is flush with the inner surface is provided. Further, a ventilation hole 21d communicating with the outside air is opened at the optimum position of the fixed mold 21-2.

Next, the molding process of this molded product will be described. 8A, 8B, and 8C are schematic side sectional views showing the molding step of FIG. 7 in order, FIG. 9 is a schematic side sectional view showing the next injection molding step of FIG. 8, and FIG. FIG. 10 is a schematic side cross-sectional view and a partial cross-sectional view of the molded product in the step of taking out the molded product next to FIG. 9.

FIG. 8 (a) (for easy understanding of the drawing, FIG.
In the process of setting the heat-resistant film (the paint injection hole and the vacuum suction hole are not shown), the movable mold 21-1 is opened and the heat-resistant film 22 is placed on the upper surface of the cavity 21a.
Supplied from and set for positioning. This heat resistant film 22
Has a heat-resistant rubber adhesive 22a (hereinafter abbreviated as an adhesive) applied in advance to at least the surface in contact with the molten resin.

The heat-resistant film is preferably a nylon film or a polyester film, and the adhesive to be adhered to the heat-resistant film is preferably a chloroprene rubber or nitrile rubber-based adhesive because it is inexpensive and easily available. Then, in order to apply the adhesive to the heat resistant film, it is applied by spray coating or a roll coater.

Next, in the step of adsorbing the heat-resistant film shown in FIG. 8 (b) (the gate of FIG. 7 is omitted for the sake of clarity), the heat-resistant film 22 thus set is heated by the heating means 13,
That is, heat for softening is softened by using heat for controlling the temperature of the mold 21 (control temperature is about 70 ° C.) and if necessary, for example, radiant heat of a far infrared heating device or convection heat of a hot air heating device. When the heat resistant film 22 begins to soften, the movable mold 21
-1 is closed slowly and the heat-resistant film 22 is sandwiched by the split surfaces.
Although it was pushed in, at that time, the air in the cavity 21a was exhausted from the vacuum suction hole 21c of the movable mold 21-1, and conversely, it was heated to about 100 ° C from the ventilation hole 21d of the fixed mold 21-2. Air is sent in and heat resistant film 22 is placed in cavity 21a.
Adsorb on the inner surface. All paint injection holes 21b are closed.

The plurality of vacuum suction holes 21c are formed such that the heat-resistant film 22 is stretched as uniformly as possible during vacuum suction according to the shape of the inner surface of the cavity of the mold 21, that is, the shape of the coated surface of the molded product, so that wrinkles and wrinkles do not occur. The opening is arranged at an optimum position so that tearing does not occur, and an appropriate film thickness is selected.

In the paint injection step of FIG. 8 (c), after the movable mold 21-1 is closed to the fixed mold 21-2, the coating surface area is obtained from the plurality of paint injection holes 21b in which the flow rate control valves are opened. The paint film 23 is formed by injecting a predetermined amount of paint corresponding to the size of the above into the gap between the inner surface of the cavity 21a of the fixed mold 21-2 and the heat resistant film 22.

As the paint, a thermosetting acrylic urethane paint is usually used, but the paint is selected in consideration of the adhesion to the heat resistant film. If the adhesive force between the paint and the heat-resistant film is weak, a heat-resistant film on which the adhesive having good adhesiveness is applied in advance is also used on the coating surface side of the paint.

In the injection molding process of FIG. 9 (the heat-resistant film with the adhesive shown in FIG. 8C is omitted in order to make the drawing easy to see), the paint film 23 is a temperature control heat of the mold 21. A molten resin 14 such as an ABS resin supplied from a molten resin supply device 34 is injected from the gate into the cavity when it is semi-cured by a (heat-adjustable sheath heater (not shown) is incorporated). The injection molding conditions are resin temperature of about 220 ℃, mold temperature of about 70 ℃, injection pressure of about 1000 kgf / cm.
^Set to ² .

In the step of removing the molded product shown in FIG. 10 (a),
After holding pressure by a mold clamping and pressurizing device (not shown) and cooling and molding, open the movable mold 21-1 and bond it onto the molding resin 14a as shown in the partial cross-sectional view of the molded product in Fig. 10 (b). A molded product 10-3 having the agent 22a, the heat-resistant film 22, and the paint film 23 laminated in this order and the surface thereof being decorated is taken out. In the molded product 10-3, the area shown in the figure is painted in a checkered pattern and is discharged. The heat-resistant film protruding from the end surface of the molded product is cut and removed together with burrs.

As in the first method, in order to improve the mold release of the molded product, a silicon-based release agent having a thickness of 10 to 20 μm is set on the inner surface of the cavity of the mold before setting the heat resistant film.
You may provide the process of apply | coating with and drying.

A cross-cut test was performed on the molded article coated by the second method in order to evaluate the adhesion of the coating film. We made 100 squares of 5 mm square in any place on the molded product, and applied a pressure sensitive adhesive tape to perform a forced peeling test. As a result, 100/100 was no peeling from the paint film or heat resistant film. Good adhesion was obtained. In addition, FIG.
The film was cut from the position indicated by the one-dot chain line in (1) and the thickness of the paint film was examined. As a result, the thickness of the paint film was 20 ± 5 μm and a uniform film thickness was obtained.

In the second method, when the heat-resistant film set on the inner surface of the cavity and sandwiched by the split surfaces of the mold is softened by heating, the vacuum suction hole on the inner surface of the cavity is evacuated and hot air is blown from the ventilation hole to form a vacuum. Since suction is performed, the heat resistant film can be sufficiently softened and adsorbed along the inner surface of the cavity without causing wrinkles.

Since the heat-resistant film is coated with an adhesive in advance on at least the surface in contact with the molten resin, the adhesive and the paint film are activated by the heat from the molten resin, and the heat-resistant film is molded through the adhesive. Further, the paint film can be strongly adhered to the product and to the heat-resistant film (via the adhesive in the case of a heat-resistant film having adhesive applied on both sides).

Further, since a predetermined amount of paint is injected from a plurality of locations depending on the size of the coating surface area from the paint injection hole between the cavity inner surface of the mold and the heat resistant film, the activated paint film is made of molten resin. Spread even thinner by molding pressure,
Moreover, since the heat-resistant film can protect the paint film and prevent the paint from flowing out, it is possible to decorate the surface of the molded product uniformly and cleanly without uneven coating at the same time as molding.

Next, a molded product obtained by using a chloroprene rubber adhesive as the adhesive in the above-mentioned embodiment of the second method and using a polypropylene film as the heat-resistant film is also uniform without coating unevenness as in the above-mentioned embodiment. A painted surface was obtained. When this molded product was subjected to the same evaluation test, a sufficient adhesion without peeling at 100/100 and a uniform film thickness of 20 ± 5 μm were similarly obtained.

It should be noted that the viscosity and temperature of paints and adhesives used in all the examples described above are optimally adjusted,
It goes without saying that it will be set.

[0051]

As described above in detail, according to the present invention,
In surface decoration such as painting of injection molded products, the first method is to form a paint film in a semi-cured state in advance on a mold and then injection-mold a molten resin to obtain a clean surface without uneven coating or peeling. Can be painted. In particular, it is possible to cleanly coat a complex-shaped painted surface that cannot be painted cleanly by the conventional method simultaneously with injection molding.

In the second method, a heat-resistant film is provided as an inner layer under the paint film to protect the paint film by the heat-resistant film and prevent the paint film from flowing out. Therefore, there is no uneven coating as in the first method. Uniform and clean surface coating is possible. Further, by using an adhesive together, it is possible to sufficiently secure the adhesion to the molded product and to obtain a highly durable coated surface without peeling, which is a very useful effect in the industry.

[Brief description of drawings]

FIG. 1 is a perspective view of a molded article of a first embodiment according to the first method of the present invention.

FIG. 2 is a schematic side sectional view of a mold for molding the molded product of FIG.

FIG. 3 is a schematic side sectional view showing the molding process of FIG. 1 in order.

FIG. 4 is a schematic side sectional view showing a take-out step next to FIG.

FIG. 5 is a perspective view of a molded product of a second embodiment according to the first method of the present invention.

FIG. 6 is a perspective view of a molded product of an embodiment according to the second method of the present invention.

7 is a schematic side sectional view of a mold and an injection molding apparatus for molding the molded product of FIG.

FIG. 8 is a schematic side sectional view showing the molding process of FIG. 7 in order.

9 is a schematic side sectional view showing an injection molding step following FIG.

FIG. 10 is a schematic side sectional view and a partial sectional view of the molded product in the step of taking out the molded product next to FIG.

[Explanation of symbols]

1,21 Mold 13 Heating means 1-1,21-1 Movable mold 14 Molten resin 1-2,21-2 Fixed mold 21b Paint injection hole 1a, 21a Cavity 21c Vacuum suction hole 2 Release film 22 Heat resistant film 3 Paint film 22a Heat-resistant rubber adhesive (adhesive) 4 Adhesive film 31 Paint supply device 10 Molded product 32 Vacuum exhaust device 11 Release agent injection device 33 Film supply device 12 Paint injection device 34 Molten resin supply device

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Kimura 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Takayuki Fujiwara, 1015, Kamedotachu, Nakahara-ku, Kawasaki, Kanagawa Prefecture Fujitsu Limited ( 56) References JP-A-6-71693 (JP, A) JP-A-62-253420 (JP, A) SAIKAI 63-30126 (JP, U) JP-B 63-45291 (JP, B2) JP-B Hei 5-41089 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (3)

(57) [Claims] 1. A paint injection hole and vacuum suction on the inner surface of the cavity.
Use a mold consisting of a movable mold with holes and a fixed mold
Open the mold and melt at least the inner surface of the cavity.
Heat resistant with a heat resistant rubber adhesive applied to the surface that contacts the molten resin
The process of setting the film and the capping process while evacuating the heat resistant film from the vacuum suction hole.
The step of adsorbing to the inner surface of the mold, and after closing the mold, the inner surface of the cavity of the mold and the heat resistant filter
Step of injecting paint from the paint injection hole between the rum and
If, at the same time formed when injection molding a molten resin into the cavity
An in-motion process including a step of decorating a shaped product
Ludcoat injection molding method. 2. The heat resistant film is exhausted from a vacuum suction hole.
In the process of adsorbing on the inner surface of the cavity,
To heat and soften the thermal film by heating means
The in-mold coat injection molding according to claim 1.
Method. 3. A cavity is held by a mold clamping pressure device.
The paint injection hole and the vacuum suction hole that open at least on the inner surface
And a mold comprising a movable mold and a fixed mold having
At least in the predetermined position of the
A film that sets a heat-resistant film coated with a rubber adhesive
Film supply device and the heat-resistant film while evacuating from the vacuum suction hole.
Between the inner surface of the cavity of the mold and the heat-resistant film
Paint supply device that injects a predetermined amount of paint from the paint injection hole
And inject the molten resin into the cavity and decorate it at the same time as molding
An injection molding device characterized in that