JP5093744B2 - In-mold coating mold - Google Patents

Description

  In the present invention, after molding a molded article of a thermoplastic resin in a mold, a thermosetting paint is injected between the molded article of the resin and the cavity surface of the mold and cured in the mold. Thus, the present invention relates to an in-mold coating molding die suitable for molding an in-mold coating molded product that coats and decorates the surface of a resin molded product with a paint (sometimes referred to as a coating film).

  Conventionally, the painting method has been widely used as a method for improving the decorativeness of molded products, but recently, for the purpose of omitting the painting process, resin molding and coating with a coating film are placed in the same mold. An in-mold coating method (sometimes referred to as an in-mold coating method) was proposed.

In order to explain an example of the in-mold coating forming method, FIG. 6 shows a flowchart explaining the outline of the process. The in-mold coating molding method shown in FIG. 6 is a resin molded product molded in a mold and a mold cavity after injection molding in a mold using a thermoplastic resin as a base material and then the mold is slightly opened. A gap is formed between the surface and the paint is injected into the gap using a paint injector.
After that, the mold is clamped again to uniformly extend the paint on the surface of the molded product, and then cured and coated.

The in-mold coating molding method performs molding and coating of the thermoplastic resin in the same mold, so the cost can be reduced by omitting the process, and at the same time, there is almost no volatilizing solvent, so environmentally friendly molding It's a method. Further, since there is no problem that floating dust adheres to a coating film before being cured during molding and becomes defective, a high quality product can be obtained.
Therefore, in particular, the use of the in-mold coating forming method has been studied for many parts such as bumpers, doors, door mirror covers, and fenders for automobiles that require high quality in appearance.

  As the paint used for the in-mold coating molding method, a thermosetting paint is generally used. For the paint injected into the mold, the mold temperature and the resin temperature are used to obtain the mold. Harden in. Therefore, the mold is usually set to a high temperature of 100 ° C. or higher.

  In addition, as a metal mold | die used for the said in-mold coating molding method, although a metal mold | die as disclosed by patent document 1, patent document 2, etc. is well-known, a coating material does not mainly leak from a metal mold | die. There are many things that are focused on the technology to do so.

JP 9-48044 A

JP-A-9-52257

By the way, in the case of performing the in-mold coating, basically, it is necessary to cure the paint on the resin molded product. Therefore, the paint is allowed to flow in the paint injection machine or from the paint tank to the paint injection machine. The equipment is designed so that the paint does not harden in the paint line.

However, at the time of actual molding, the tip of the paint injection machine etc. will be in contact with a high-temperature mold or resin for a long time, and as a result, the temperature of the paint injection machine will rise more than set. There is a fact that it will be done. For this reason, if the paint at the time of molding remains even slightly at the tip of the paint injector for some reason, there is a problem that the resin remaining there hardens at the tip. Of course, the paint injecting machine has a structure in which the temperature is adjusted by a cooling device or the like so as not to be affected by the mold temperature as much as possible, but it is only slightly affected by disturbances during continuous molding. A reasonable amount of paint hardens at the tip of the paint injector.

If the amount of hardened paint is small, there will be no problems such as clogging the tip of the paint injector, but the hardened material of the paint will become a solid called “striking” and it will flow into the paint flow in the next molding. As a result, “bump” disturbs the flow of the paint in the mold or appears on the surface of the coating film, thereby deteriorating the appearance of the molded product after coating. In particular, the in-mold coated molded product is often applied as a decoration on the design surface that forms its appearance, and in such a case, a slight “striking” causes a fatal defect.

  In addition, the above-mentioned cured product of the paint called “Batsu” may occur in the paint line connected to the paint injection machine. As a result, the “shock” disturbs the flow of the paint in the mold and deteriorates the appearance after covering the molded product.

  The present invention has been made in view of the problems in actual molding as described above, and in the stage before pouring the paint into the mold, the cured product of the paint caused by some cause is a solid matter. Thus, it is an object of the present invention to provide a mold for in-mold coating molding suitable for preventing the problem of poor appearance caused by flowing in a paint.

In order to solve the above problems, the mold for in-mold coating molding according to the present invention is:
(1) Inside a mold having a mold cavity formed by a male mold and a female mold, and having a coating material injection machine for coating the surface of a resin molded product molded by the mold cavity to form a decorative surface Cavity dimensions in the mold opening and closing direction, including an intermediate cavity that forms a thin portion adjacent to the mold cavity and an auxiliary cavity that is connected to the mold cavity via the intermediate cavity. The thin part is formed so that the minimum dimension is the minimum dimension from the paint injection port of the paint injection machine arranged in the auxiliary cavity to the decorative surface of the mold cavity, and the paint injected from the paint injection port and through the thin portion, and configured to inject into the decorative surface.

( 2 ) In the in-mold coating mold according to (1) , the minimum dimension in the cavity for forming the thin portion is provided from the paint injection port to the decorative surface with respect to the cavity dimension in the mold opening / closing direction. Compared to the dimensions of the other cavity portions thus formed, the dimensions were set to be 1 mm or more smaller.

  An in-mold coating molding die according to the present invention is an in-mold coating molding die provided with a coating material injection machine for coating a surface of a resin molded product molded in a mold cavity to form a decorative surface. In addition, a thin-walled cavity for forming a thin-walled portion is provided in the resin molded product between the paint-injecting port of the paint-injecting machine and the cavity for forming the decorative surface. The dimensions were set to the minimum dimension from the paint inlet to the decorative surface, and the paint injected from the paint inlet was injected into the decorative surface through the thin-walled cavity. Therefore, during the coating injection process for in-mold coating, the thickness of the flow path of the coating formed in the thin-walled cavity is extremely smaller than that of other cavities. However, it cannot be sandwiched between the narrow flow path parts and flow forward. Therefore, it is possible to prevent the cured product of the paint from flowing into the decorative surface of the mold cavity, and as a result, it is possible to obtain an in-mold coated molded article having an excellent appearance free from defects due to the above-mentioned “striking”.

  The minimum dimension of the thin cavity in the mold opening / closing direction is preferably 1 mm or more smaller than that of other cavity portions. If the dimensional difference in the mold opening / closing direction in the cavity is extremely smaller than 1 mm, the dimensional difference in the flow path is also reduced, which is not preferable because the ability to collect the cured product is reduced.

  Further, in the present invention, since the cured product of the coating is cured in a state where it is sandwiched between narrow channel portions of the thin-walled cavity, it is expected that the appearance will be poor. Therefore, it is usually preferable to design the mold so that the thin-walled cavities and the like are arranged in a portion that does not form an appearance.

Hereinafter, embodiments of an in-mold coating mold according to the present invention will be described with reference to the drawings.
1 to 6 relate to an embodiment of the present invention, FIG. 1 is a cross-sectional view showing a schematic structure for explaining the configuration of an in-mold coating mold, and FIG. 2 is an in-mold coating mold. It is explanatory drawing for demonstrating the auxiliary | assistant cavity and intermediate | middle cavity formed in a type | mold. FIG. 3 is a view for explaining the flow of the resin and the paint in the auxiliary cavity, the intermediate cavity and the mold cavity, and FIG. 4 is a conceptual diagram of a mechanism for collecting the cured product of the paint at the intermediate portion. FIG. 5 is a diagram for explaining the length (L) and thickness (W) of the intermediate portion. FIG. 6 is a flowchart for explaining steps of a general in-mold coating forming method.

A preferred example of the in-mold coating mold 100 (also referred to as the mold 100) according to the present invention will be described below with reference to FIGS.
A mold 100 shown in FIG. 1 includes a movable mold 10, a fixed mold 20, a paint injector 50, and the like. In one example of the embodiment shown in FIG. 1, the movable mold 10 is a female mold. Yes, the fixed mold 20 is a male mold.

The mold 100 is configured such that a fixed mold 20 that is a male mold and a movable mold 10 that is a female mold are fitted together in a so-called shear edge structure at a fitting portion of a continuous structure. In the fitted state, a mold cavity 15 and an auxiliary cavity 18 adjacent to the mold cavity 15 via the intermediate cavity T are formed therein.
Note that the above-described fitting portion (sometimes referred to as a “drilling portion”) of the climax structure is formed so as to surround the mold cavity 15, the intermediate cavity T, and the adjacent auxiliary cavity 18 from the periphery. The mold 100 prevents the resin filled in the mold cavity 15, the intermediate cavity T, and the auxiliary cavity 18 from leaking out of the mold 100 at the gaps.

Here, in the embodiment shown in FIG. 1, a molded product having a desired shape (in the present embodiment, a flat plate) is formed by the mold cavity 15, and an auxiliary cavity 18 (to be described later) and a thin cavity are used. Since the molded product formed by the provided intermediate cavity T is unnecessary and is cut after molding, the appearance of the product is not affected.
In the present embodiment, one surface of the resin molded product to be molded by the mold cavity 15 is a decorative surface in which decoration by coating affects the product appearance, and the auxiliary cavity 18 and the like are cut off after molding. .
However, it goes without saying that the embodiment of the present invention is not limited to this. For example, when an auxiliary cavity is not provided, a paint injection port is provided in the mold cavity and a part of the mold cavity is provided. And forming a thin-walled cavity to form a thin-walled portion, and the paint may flow through the thin-walled cavity from the paint inlet to the decorative surface (the part where the appearance of the coating affects the quality of the product), The part covered with the paint between the paint injection port and the thin cavity may be configured so that the appearance defect due to “bump” becomes a non-decorative surface that does not affect the quality of the product. Accordingly, it is possible to appropriately change the form within a range not departing from the technical idea of the present invention.

Next, the arrangement and shape of the intermediate cavity T shown in FIGS. 1 and 2 will be described.
The molded product molded by the mold 100 shown in FIG. 1 has a rectangular flat plate shape as suggested in FIG. 2 (2), and the auxiliary cavity 18 is intermediate to one side. Adjacent through cavity T. The auxiliary cavity 18 is provided with a paint injection port 51 of the paint injection machine 50 for injecting paint, and a resin injection port 61 of a hot runner for injecting and injecting resin.

As shown in FIG. 2B, the auxiliary cavity has a shape similar to a fan shape and gradually increases toward the mold cavity 15. The intermediate cavity T is formed so that the cavity surface to be formed communicates with one side of the mold cavity 15.
As shown in FIG. 2, the intermediate cavity T is in the direction from the auxiliary cavity 18 to the mold cavity 15, and once in the middle, the minimum dimension in the mold opening / closing direction is the entrance side of the mold cavity 15 (intermediate side) Cavity side) is formed so as to be smaller than the dimension, and the paint flowing from the auxiliary cavity 18 toward the mold cavity 15 in the paint injecting step described later passes through the flow path at the minimum dimension portion of the intermediate cavity T. The shape is narrowed down.

Next, the paint injector 50 will be briefly described.
The paint injection machine 50 according to the present embodiment is attached to the movable mold 10 so that the paint can be injected into the auxiliary cavity 18 from the paint injection port 51 disposed on the movable mold 10 side of the auxiliary cavity 18. It is configured. Further, a valve (not shown) is attached to the paint injection port 51 of the paint injection machine 50, and the valve is closed during the injection molding of the base material, so that the auxiliary cavity 18 of the mold 100 is closed. The injected resin is prevented from entering the paint injector 50 from the paint inlet 51.

  The paint injector 50 in the present embodiment is driven by a driving device (not shown) so that the paint supplied into the paint injector 50 can be accurately injected in a desired amount. Yes.

  Although the coating material injection machine 50 in the present embodiment is configured to inject the coating material from the movable mold 10 side of the auxiliary cavity 18 as described above, the present invention is not limited to this, and resin molding formed by the auxiliary cavity 18 is performed. What is necessary is just to comprise so that a coating material can be inject | poured into the clearance gap produced between the goods and the mold cavity surface, and the coating material injection | pouring machine 50 may be attached to the fixed mold | type 20, etc., if the conditions are satisfy | filled.

Hereinafter, an in-mold coating forming method using the mold 100 according to the present embodiment will be described.
First, as a first step, the mold 100 is clamped by a mold clamping device (not shown). In this state, the vicinity of the intermediate cavity T provided as a thin cavity for forming a thin portion is as shown in FIG.
Then, as shown in FIG. 3 (2), a thermoplastic resin as a base material is injected from the resin injection port 61 into the auxiliary cavity 18, and the injected resin passes through the intermediate cavity T through the intermediate cavity T. Filled into mold cavity. In the present embodiment, UT20B manufactured by UMGABS (former company name: Ube Saikon) Co., Ltd., which is an ABS resin, was used as the base material.

Thereafter, the substrate is cooled to a certain degree (a degree that can withstand the injection pressure of the paint described later).
After cooling the base material, the auxiliary cavity 18 is in a state where the mold is slightly opened (in the present embodiment, the movable mold 10 is moved in the mold opening direction by about 1 mm) as shown in FIG. In addition, a gap (also referred to as a paint gap or simply a gap) is generated between the resin molded product molded in the mold cavity 15 and the cavity surface of the movable mold 10.

As described above, the mold 100 is slightly opened to form a gap for injecting the paint between the resin molded product and the cavity surface of the movable mold 10. In parallel with the process, a gap is formed also in the intermediate cavity T to form a narrow channel through which the paint flows.
In addition, since the gap of the intermediate cavity T generated at this time is determined by the mold opening amount of the resin mold and the heat shrinkage amount, the heat shrinkage amount of the resin filled in the minimum dimension portion of the intermediate cavity T is determined by the mold. Since the amount of heat shrinkage filled in the cavity 15 is smaller, the size of the gap through which the paint flows inevitably becomes smaller in this portion. In order to collect the solid matter of the paint, it is preferable to determine the gap thickness (W) so that the thickness of the flow path through which the paint in the intermediate cavity T flows is 0.1 mm.

After the gap is generated, 25 ml (milliliter) of paint is injected from the paint injection port 51 into the gap by the paint injection machine 50. The covering surface area of the molded product molded with the mold used in the present embodiment is 2500 cm ² in total for the auxiliary cavity 18 and the mold cavity 15, and the thickness of the coating film is about 0.1 mm. . The paint used in the present embodiment is Praglas # 8000: Red (manufactured by Dainippon Paint Co., Ltd.).

  After injecting the paint, the movable mold 10 is moved in the direction of the fixed mold 20, the mold 100 is closed again and the mold is closed, and the paint in the gap is made to flow while spreading, and the surface of the molded product is covered with the paint. To do.

Note that when the coating material is injected in the above-described process, the size of the intermediate cavity T is extremely small as compared with other portions. Therefore, for some reason, even if the hardened material of the paint is mixed as a solid in the paint injected into the auxiliary cavity 18 from the paint injector 50, it is caught between the gap portions of the intermediate cavity T and beyond. Therefore, it is possible to prevent the mold cavity 15 from flowing into the decorative surface.
By enclosing the cured product of the paint in the auxiliary cavity and the intermediate cavity T that do not affect the appearance through the above steps, a good in-mold coated product having no appearance defect could be obtained.

  In addition, it is preferable that the minimum dimension in the mold opening / closing direction of the intermediate cavity T, which is a thin cavity, is 1 mm or more smaller than other cavity portions. If the dimensional difference in the mold opening / closing direction is extremely smaller than 1 mm, the dimensional difference of the flow path is also reduced, so that the ability to collect the cured product is reduced, which is not preferable.

It is sectional drawing which showed the general | schematic structure for demonstrating the structure of the metal mold | die for mold | cover inner mold | die concerning the embodiment of this invention. It is a figure for demonstrating the auxiliary | assistant cavity and intermediate | middle cavity which are related to embodiment of this invention and are formed in the metal mold | die for in-mold coating molding. It is a figure for demonstrating the flow of resin and a coating material of an auxiliary | assistant cavity, an intermediate | middle cavity, and a mold cavity in connection with embodiment of this invention. It is a conceptual diagram of the mechanism which concerns on embodiment of this invention and collects the hardened | cured material of a coating material in an intermediate | middle cavity. It is a figure explaining the length (L) and thickness (W) of an intermediate | middle cavity in connection with embodiment of this invention. It is a flowchart explaining the process of the in-mold coating method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Movable type 15 Mold cavity 18 Auxiliary cavity 20 Fixed mold 50 Paint injection machine 51 Paint injection port 60 Hot runner 61 Resin injection port 100 Mold for mold-in-mold coating T Intermediate cavity K Paint gap L Intermediate cavity length W Intermediate Cavity gap thickness

Claims (2)

For in-mold coating molding having a mold cavity formed by a male mold and a female mold, and having a coating material injection machine for coating the surface of a resin molded product molded by the mold cavity to form a decorative surface In the mold,
An intermediate cavity that forms a thin portion adjacent to the mold cavity, and an auxiliary cavity that leads to the mold cavity via the intermediate cavity;
About the cavity dimension in the mold opening and closing direction, the minimum dimension of the thin wall portion is formed to be the minimum dimension from the paint injection port of the paint injection machine arranged in the auxiliary cavity to the decorative surface of the mold cavity,
The injected paint from paint inlet, through the thin wall portion, mold coating mold to be injected into the decorative surface. Regarding the cavity dimension in the mold opening and closing direction, the minimum dimension in the cavity for forming the thin portion is smaller than the dimension of the other cavity part provided from the paint inlet to the decorative surface by 1 mm or more. The mold for in-mold coating molding according to claim 1.

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