JP2698001B2 - In-mold coating method and injection mold for in-mold coating - 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 coating method and an injection mold for in-mold coating.

[0002]

2. Description of the Related Art In recent years, there has been a tendency to adopt an in-mold coating method for coating a molded article during the molding in response to automation of the molding operation. In this in-mold coating method, when a molten resin is filled in the cavity, the resin shrinks as it cools and solidifies, and a fine gap is generated between the cavity surface of the mold and the resin. A coating material is injected under high pressure to coat a molded article, and is proposed by Klaus.

[0003]

However, in such an in-mold coating method, as a result of utilizing minute gaps generated due to shrinkage of the resin in the cavity, the coating is susceptible to the influence of the viscosity of the coating material. Since the flow length is short, there is a drawback that the coating target is limited to a specific injection molded product.

The present invention has been made in view of the above problems, and provides an in-mold coating method capable of easily coating an injection-molded article without particularly limiting the object. It provides a mold.

[0005]

According to the in-mold coating method of the present invention, a fixed mold and a movable mold are clamped to form a cavity, and the cavity is filled with a molding material in a molten state by a short mold. After that, a coating material is injected into the cavity, and a high-pressure gas is injected into the molten molding material to form the molded product, thereby coating the molded product with the coating material. is there.

The injection molding die for in-mold coating of the present invention comprises a fixed die and a movable die which forms a cavity by clamping the fixed die. One or more coating material inlets are opened to at least one of the mold and the movable mold facing the cavity, and a gas inlet is formed in at least one of the fixed mold and the movable mold. It is characterized by the following.

[0007]

The fixed mold and the movable mold are clamped to form a cavity, and the cavity is filled with a molten molding material by a short mold. Then, a coating material is injected into a gap formed between the cavity and a molten molding material filled in the cavity with a short mold. Thereafter, high-pressure gas is injected into the molten molding material to form a molded article. At this time, the coating material injected into the gap formed between the cavity and the molding material filled in the cavity comes into close contact with the molded product, and can cover the molded product.

As a result, it is possible to easily apply the in-mold coating to the injection molded product.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an injection mold 1 according to the present invention. The mold 1 is composed of a fixed mold 2 and a movable mold 3. It is movable by a hydraulic cylinder (not shown) so that the mold can be opened and the mold can be clamped. A cavity C is formed by clamping the fixed mold 2 and the movable mold 3, and the cavity C is formed by the first sprue formed in the tip of the injection nozzle (not shown) and the fixed mold 3. 4, the runner 5, the second sprue 6, and the gate 7 communicate with each other. Therefore, at the time of injection molding, the molten resin injected from the injection nozzle is filled into the cavity C via the first sprue 4, the runner 5, the second sprue 6, and the gate 7.

The fixed mold 2 and the movable mold 3 are provided with coating material injecting machines 8 connected to a coating material supply pump (not shown).
The inlets 8a, 8a are opened facing the cavity surface, respectively. The movable mold 3 is provided with a gas passage 9 communicating with a high-pressure gas source (not shown) such as nitrogen gas. The gas inlet 9 a has an opening in the second sprue 6. Have been.

Next, the molding operation of the present embodiment will be described. After the movable mold 3 is clamped to the fixed mold 2, the first sprue 4, the runner 5, the second sprue 6, The cavity C is filled with a molding material in a molten state through the gate 7 by a short mold (see FIG. 2).
Thus, the short mold, ie, the filling of the molding material in an insufficient amount to fill the cavity C,
Since a gap is formed between the cavity surface of each of the molds 2 and 3 and the filled resin surface, the coating material supply pump is operated, and the coating material is discharged from the injection port 8 a through the coating material injection machine 8. Inject into the aforementioned gap. As a result, the coating material adheres to the uncured molding material surface and the cavity surfaces of the dies 2 and 3 and spreads to every corner of the gap (see FIG. 3). Thereafter, when a high-pressure gas is supplied to the second sprue 6 from the gas inlet 9a through the gas flow path 9, the high-pressure gas is filled into the cavity C through the molten molding material of the second sprue 6 and the gate 7. Blown into the uncured molding material. As a result,
The uncured molding material flows along the cavity C while forming a hollow portion, and a molded article S matching the cavity C is formed (see FIG. 4). At this time, the coating material adhering to the cavity surfaces of the molds 2 and 3 and the coating material floating in the gaps also adhere to the surface of the molded product S, so that the entire surface of the molded product S is covered with the coating material. Will be.

As a coating material used in such an in-mold coating method, it is necessary to select a material compatible with the resin. The coating material may be an antistatic agent, a primer, an antibacterial agent, or the like, other than the paint, and may be in the form of a liquid or a powder such as a powder. When a powder coating material is used, it is preferable to separately provide a suction port.

The injection structure of the coating material is such that a needle valve is used, a porous material such as sintered metal or a slit that is formed by closely adhering a block is used to prevent infiltration of molten resin. However, there is no particular limitation as long as it allows passage of the coating material.

[0015]

As described above, according to the present invention, the fixed mold and the movable mold are clamped to form a cavity,
After filling the cavity with the molding material in a molten state by a short mold, a coating material is injected into a gap formed between the cavity and the molding material in a molten state filled in the cavity. By injecting high-pressure gas into the molding material and molding the molded product, the coating material injected into the gap formed between the cavity and the molding material filled in the cavity adheres to the molded product, and the molding is performed. The surface of the product can be covered with a coating material, and the injection molded product can be easily applied with in-mold coating.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the overall configuration of an injection mold according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing a molding process using the injection mold of FIG.

FIG. 3 is an enlarged cross-sectional view showing a molding process using the injection mold of FIG. 1;

FIG. 4 is an enlarged cross-sectional view illustrating a molding process using the injection molding die of FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injection molding die 2 fixed die 3 movable die 4,6 sprue 5 runner 7 gate 8 coating material injection machine 8a injection port 9 gas flow path 9a gas injection port C cavity S molded product

Claims (2)

(57) [Claims] 1. A fixed-side mold and a movable-side mold are clamped to form a cavity, a molding material in a molten state is filled into the cavity by a short mold, and a coating material is injected into the cavity. An in-mold coating method characterized in that a molding material is coated by injecting a high-pressure gas into a molding material in a molten state to form the molding. 2. A fixed mold and a movable mold that forms a cavity by clamping the fixed mold.
At least one of the fixed mold or the movable mold is opened with one or a plurality of coating material injection ports facing the cavity, and further, a gas injection port is formed in at least one of the fixed mold or the movable mold. An injection mold for in-mold coating, characterized by being formed.