JP2002172657A - In-mold coating mold and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-mold coating mold and method for injecting a paint in the gap, which is formed between the surface of a mold cavity and the surface of a molded article by the fine mold opening operation of a mold, under low pressure and efficiently manufacturing the molded article wherein the paint is closely bonded to the surface of a thermoplastic resin molded article using a flat type mold. SOLUTION: In the in-mold coating mold constituted so that molds are opened at a predetermined interval after the thermoplastic resin molded article is molded in the cavity formed by the molds to inject a predetermined coating agent in the gap between the surface of the obtained thermoplastic resin molded article and the cavity surface of the molds by a coating agent injection machine and the molds are again clamped after the injection of the coating agent is completed to cure the coating agent in the molds to manufacture the molded article wherein the coating agent is closely bonded to and integrated with the surface of the thermoplastic resin molded article, a sub-cavity constituting a part of the back surface of a main cavity and a movable core advancing into the retreating from the sub-cavity on the inner side of the outer peripheral part on the anti-coating surface side of the sub-cavity are provided to the outer entire periphery of the main cavity and a high temperature part is provided at the position opposed to the movable core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for injecting a coating material between a surface of a resin molded article molded in a mold and a cavity surface of a mold, and then curing the coating material in the mold. A mold for in-mold coating and a method for in-mold coating to obtain a molded product in which the coating agent is tightly integrated with the surface of the resin molded product, especially in-mold coating with measures to prevent leakage of the coating material during re-clamping The present invention relates to a metal mold and an in-mold coating method.

[0002]

2. Description of the Related Art For the purpose of improving the quality of thermoplastic resin molded products used for automobiles, home appliances, building materials, etc. by adding added value such as decorativeness, and reducing costs by reducing the number of molding steps, gold is used. After injecting a coating material (paint) between the surface of the thermoplastic resin molded product molded in the mold and the mold cavity surface, the coating material is cured in the mold to cover the surface of the thermoplastic resin molded product. There has been proposed an in-mold coating molding method (also referred to as an in-mold coating method) for producing a molded product in which an agent is adhered and integrated. The use of this in-mold coating method is considered especially for molding various parts for automobiles with high demands on appearance and quality, such as bumpers, door mirror covers, fenders, door panels, back door panels, wheel caps and side covers for motorcycles. Have been.

[0003] Further, as a mold (for injection molding) generally used for conventional in-mold coating molding, a flat type having no shear edge structure is frequently used. The sealing surface cannot seal. Therefore, when the coating agent is injected, it flows out of the cavity, it is difficult to form a good coating on the surface of the molded product, and the leaked coating agent adheres to the parting surface. When molding is repeated as it is, the parting surface is damaged by the clamping pressure, and the life of the mold is greatly shortened. In addition, paint residue adhering to the mold is mixed into the molded product to cause defective products, resulting in lower molded product yield,
This has led to a significant decline in production efficiency.

As a prior art for preventing paint leakage by using a general injection molding die (flat type), JP-A-6-328505, "Injection molding die",
Japanese Patent Application Laid-Open No. 52262/1992 “Mold for in-mold coating molding method” and the like. Japanese Patent Application Laid-Open No. 6-328505 discloses that a shear edge structure (a gap between a fixed mold and a movable mold is reduced over the entire circumference) and that a paint pool space is provided outside (a mating surface side). Discloses a technique for preventing paint leakage. That is, at the time of injection molding, the molten resin can seal the paint at the shear edge structure portion, and even if this seal is not sufficient, when the paint is injected into the mold after injection molding, the shear edge structure portion The paint that has flowed out further accumulates in the paint pool space and does not leak to the parting surface, and in the case of repeated molding, the paint in the shear edge structure and the paint pool space seals itself. It is described that the effect can be exerted.

[0005] Japanese Patent Application Laid-Open No. 9-52262 discloses that
When the coating material is injected between the injection-molded molten resin and the mold surface of the cavity, the thickness of the coating can be accurately controlled and the coating material can be prevented from flowing into the molten resin injection section. Techniques are disclosed. In other words, a recess is formed in the runner part away from the opening of the molten resin injection part, and the flow resistance of the coating material in this part is increased, thereby eliminating the leakage of the coating material and accurately controlling the thickness of the coating. Possible techniques are described.

However, in Japanese Patent Application Laid-Open No. 6-328505, since there is no minute mold opening operation, a high pressure is required for injecting the paint, and a minute gap is formed in the shear edge structure due to volume shrinkage due to cooling and solidification of the resin. There is a problem that paint is generated and causes paint leakage, and paint flowing out of the shear edge structure portion is accumulated in the paint pool space in each molding cycle and the paint enters the parting surface. . For this reason, efficient production was not possible. In Japanese Patent Application Laid-Open No. 9-52262,
The main purpose is to prevent paint from flowing back to the gate / runner section.
There is no description of paint leakage to the parting surface.
That is, the paint injected from the paint injection section provided in the sub-cavity flows out to the side opposite to the cavity and enters the parting surface side. However, since there is no concave portion on the side opposite to the cavity, it is not possible to prevent the paint from flowing out. Also, because of the mold opening operation, it is not possible to provide a recess in a direction perpendicular to the mold opening direction. Furthermore, there is a problem that the reliability of paint leakage in the concave portion is lacking. When paint leakage occurs, the mold is easily contaminated. If the contaminated mold is used without being cleaned, defective molded products frequently occur. Further, if the mold is cleaned each time paint leakage occurs, the production efficiency will be greatly reduced.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to form a gap between a mold cavity surface and a molded product surface by a minute mold opening operation of a mold, and inject paint at a low pressure into the gap. To provide a mold for in-mold coating and a method for in-mold coating for efficiently manufacturing a molded product in which a paint adheres to the surface of a thermoplastic resin molded product using a flat mold. is there.

[0008]

According to a first aspect of the present invention, a thermoplastic resin molded article is formed in a mold, and the mold is opened at a predetermined interval. Then, a predetermined amount of coating agent is injected between the surface of the obtained thermoplastic resin molded article and the cavity surface of the mold by a coating agent injection machine, and after the injection of the coating agent is completed, the mold is closed again. Then, the coating material is cured in the mold to produce a molded product in which the coating material is tightly integrated with the surface of the thermoplastic resin molded product. A sub-cavity constituting a part of the back surface of the main cavity, a movable core that moves into and out of the sub-cavity inside the outer peripheral portion on the side opposite to the painting surface of the sub-cavity; And a part.

Next, in a second invention mainly based on the first invention, a thin portion is provided in a sub cavity between the outer peripheral portion of the main cavity and the movable core. Further, in the third invention, a sub-cavity which constitutes a part of the back surface of the main cavity is formed on the entire outer periphery of the main cavity, and the sub-cavity is moved into and out of the sub-cavity on the inner side of the sub-cavity on the side opposite to the coating surface. Movable core, and a high-temperature portion at a position facing the movable core, using an in-mold coating mold having a mold, after molding by injecting and filling the molten resin in the main cavity and the sub-cavity, With the movable core biased, the micro mold is opened, a coating agent is injected between the surface of the molded product and the mold cavity surface, and then re-clamping is performed. The resin was cured in a mold, and a coating agent was tightly integrated on the surface of the thermoplastic resin molded article.

[0010]

Embodiments of the present invention will be described below in detail. First, the mold structure of the present invention will be described with reference to FIG. In-mold coating mold 1 in the present invention
Is provided with a sub-cavity 33 all around the outside of the main cavity 2 so as to constitute a part of the back surface of the main cavity, and the main cavity 2 and the sub-cavity 33 communicate with each other near the lower part of the outer periphery of the main cavity 2. . In this part, the sub-cavity forms part of the back of the main cavity. On the side of the fixed mold near the center of the main cavity, a gate 22 for supplying molten resin 25 into the cavity is provided. In addition, a paint injection port 26 is provided on the movable mold side near the center of the main cavity.

Next, the sub cavity 33 will be described. On the fixed mold side (gate 22 side) near the outer periphery of the sub-cavity 33, a movable core 40 that is movable in and out of the sub-cavity 33 is disposed all around. It is fixed. A plurality of the piston rods 42 are arranged at positions where the entire circumference is equally divided. The piston rod 42 is fixed to the movable core 40 by screwing or welding. The non-movable core side of the piston rod 42 is connected to a movable core drive device such as a hydraulic cylinder or a servo mechanism. The movable core 4 is driven by the driving device based on a control signal from a control device (not shown).
0 is advanced to press a part of the molded product against the movable mold cavity surface. In this manner, the paint injected into the gap formed between the surface of the molded product and the surface of the mold cavity by the micro mold opening operation leaks out of the sub-cavity in the mold re-clamping process. When the movable core 40 is at the retracted position, the lower surface of the sub cavity 33 is configured to be flat. Further, as the driving device of the movable core, pneumatic pressure, hydraulic pressure and the like are preferable, but an electric / mechanical type may be used.

As shown in FIG. 2, a high-temperature portion (heater 23 in this embodiment) is disposed near the movable mold near the movable core 40 in the sub cavity. This high-temperature portion is used to raise the temperature of the mold cavity surface to instantaneously cure the paint that has entered the part where the molded product is pressed against the movable mold cavity surface by the movable core 40, so as to reliably prevent paint leakage. belongs to.

Next, another embodiment of the present invention will be described with reference to FIG. The present embodiment relates to claim 2, in which a minute mold opening is performed to form a gap for injecting a coating agent. This gap is formed between the surface of the molded product and the mold cavity. Immediately before or immediately after the mold opening, the movable core 40 is advanced to press the outer peripheral portion of the sub-cavity portion of the molded product against the movable mold cavity surface. At this time, a thin portion 34 is provided to facilitate deformation of the sub cavity portion. Since the thin portion 34 has low rigidity, the force required to deform the sub-cavity portion of the molded product can be reduced. Therefore, the output of the driving device of the movable core 40 can be reduced by the effect of the thin portion, the mold can be made compact, and the deformation of the sub-cavity portion of the molded product is the main cavity which is the final product of the molded product. It is possible to prevent the portion from being affected.

The shape of the sub-cavity is preferably annular, but if the product shape is rectangular or otherwise, it can be matched to the shape of the main cavity. Therefore, movable core 4
The shape of 0 also matches the shape of the main cavity.

Next, the molding method of the present invention will be described.
A description will be given based on FIG. Movable mold 20 and fixed mold 30
With the mold clamped, the molding material 25 in a molten state is injected from the gate 22 into the main cavity 2 and the sub-cavity 33, and is shaped. Next, after the elapse of the preset cooling time,
The vicinity of the outer periphery of the sub cavity portion of the molded product is pressed against the movable mold cavity surface. Thereafter, the movable mold 20 is slightly opened to form a gap for paint injection (the state of FIG. 1). In this state, as shown in FIG. 1, the sub cavity portion of the molded product is pressed against the cavity surface of the movable mold 20 by the movable core 40. The airtightness of the space (gap) 24 on the upper surface of the main cavity inside the pressed portion and the space (gap) 24 on the upper surface of the inside of the sub-cavity are secured. Therefore, the paint can be easily applied to the gap (in a vacuum state) between the mold cavity surface and the molded product surface, and
Can be injected at low pressure. Further, since the above-mentioned space is in a vacuum state, the entrainment of gas when the paint (coating agent) is injected is eliminated.

The movable core 40 can be biased after the movable mold 20 is opened. That is, the molding material 25 in a molten state is injected and filled into the main cavity and the sub-cavity in a state where the movable mold 20 and the fixed mold 30 are clamped. The core 40 is urged to press the outer peripheral portion of the molded product in the sub cavity against the heater 23 of the movable mold 20. After that, paint is injected between the mold cavity surface and the surface of the molded product, and the mold is re-clamped by applying the mold clamping force again to spread the paint on the surface of the molded product and maintain the mold-clamped state for a predetermined time. To cure the paint. Thereafter, the mold is opened to take out the molded product, and the subcavity portion is cut off to obtain the molded product. In this case, it is preferable to make a cut in the movable core 40 so that air existing between the molded product and the mold cavity surface when the paint is injected is easily released. By setting the cut position near the final filling position of the paint, the air can be easily discharged. Then, the paint is instantaneously hardened by contacting the heater 23, so that the paint does not leak outside the cut position.

Next, after a predetermined amount of coating agent (paint) is injected into the gap between the mold cavity surface and the molded product surface from the paint injection port 26 by a coating agent injection machine, a predetermined mold clamping force is applied. After re-clamping, the mold is opened after holding the mold-clamped state for a predetermined time, and the molded product is taken out. After taking out the molded article, the molded article is obtained by separating the sub-cavity portion of the molded article from the molded article. The sub-cavity can be easily separated by using a hot blade or the like. The entire surface of the obtained molded article was coated with paint, and the surface property accurately transferred the mold cavity. The adhesion between the coating film and the base resin was also good.

Although the embodiments of the mold for in-mold coating and the method for in-mold coating according to the present invention have been described in detail, these are literal examples, and the present invention is not limited to these specific examples. It is not something to be done. For example, gate 22
May be provided instead of one, and a plurality of paint inlets may be provided. In addition, it is possible to reverse the fixed mold and the movable mold by providing a gate on the side opposite to the painted surface where the gap between the molded product surface and the cavity surface is created by the mold opening operation It is.
In addition, although not enumerated one by one, the present invention can be embodied in an aspect in which various changes, modifications, improvements, and the like are added based on the knowledge of those skilled in the art. It goes without saying that, unless departing from the scope of the present invention, any of them is included in the scope of the present invention.

[0019]

As described above, the gist of the present invention is as follows. An in-mold coating metal having a sub-cavity that forms a part of the back surface of the main cavity all around the outside of the main cavity, and a movable core that moves into and out of the sub-cavity inside the outer peripheral portion on the side opposite to the coating surface of the sub-cavity. The mold is clamped using a mold, and the molten resin is injected and filled into the main cavity and the sub-cavity to form the mold. After that, the movable core is urged and the minute mold is opened, so that the surface of the molded product and the metal The coating agent was injected between the mold cavity surface, and then re-clamped to cure the coating agent in the mold.

Therefore, since the vicinity of the outer peripheral portion of the sub-cavity portion of the molded product is firmly pressed against the mold sub-cavity surface by the movable core, the paint does not leak outside from this portion. Therefore, even if the pressure in the sub-cavity rises due to the re-clamping of the mold, the paint does not leak inside (to the main cavity side) from this projection.

Further, the surface of the molded product is in a vacuum state by slightly opening the mold, and by re-clamping the mold,
The paint can be spread to every corner of the surface of the molded article without gas accumulation. Further, by providing a high-temperature portion such as a heater at a position facing the movable core of the sub-cavity, the paint can be instantaneously cured, so that the paint leakage to the outside of the mold can be reliably prevented. For this reason, it is possible to increase the mold clamping force at the time of re-clamping.

As described above, the effects of the mold for in-mold coating and the method for in-mold coating of the present invention are summarized as follows. (1) Since the minute mold opening effect can be used, the paint can be injected at a low pressure between the mold cavity surface and the molded product surface, and the sealing function for preventing the paint from leaking out of the mold has been improved. Therefore, the re-clamping force can be increased.
Therefore, the paint can be evenly spread over the entire painted surface. (2) Since there is no paint leakage, all of the injected paint adheres to the surface of the molded product. Therefore, by controlling the paint injection amount, it is possible to obtain a coating film thickness as specified. For this reason, it is possible to efficiently produce a high-quality molded product in which the front surface and the back surface near the end surface are painted.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mold for in-mold coating according to an embodiment of the present invention, showing only a main part, and a minute mold opening is performed after completion of injection filling of a molten resin into a main cavity. Indicates the status.

FIG. 2 is a schematic cross-sectional view of a mold according to the present embodiment, in which a movable core is provided inside an outer peripheral portion of a sub-cavity and a heater is mounted at a position facing the movable core.

FIG. 3 is an embodiment in which a thin portion is provided in a sub cavity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 In-mold coating mold 2 Main cavity 20 Movable mold 22 Gate 23 Heater 24 Gap 25 Molten resin (molding material) 26 Paint inlet 30 Fixed mold 33 Subcavity 34 Thin part 40 Movable core 42 Piston rod

Claims (3)

[Claims] Hall 1. After molding a thermoplastic resin molded article in a mold, the mold is opened at a predetermined interval to cover the surface of the obtained thermoplastic resin molded article with the cavity surface of the mold. A predetermined amount of the coating agent is injected by an agent injection machine, and after the injection of the coating agent is completed, the mold is re-clamped, and the coating agent is cured in the mold, and is applied to the surface of the thermoplastic resin molded article. An in-mold coating mold for producing a molded article in which a coating agent is closely adhered and integrated, wherein a sub-cavity constituting a part of a back surface of the main cavity is formed on the entire outer periphery of the main cavity, and an anti-coating of the sub-cavity is performed. A mold for in-mold coating, comprising: a movable core that advances and retreats into the sub-cavity inside a surface side outer peripheral portion; and a high-temperature portion at a position facing the movable core. 2. The mold for in-mold coating according to claim 1, further comprising a thin portion in a subcavity between the outer peripheral portion of the main cavity and the movable core. 3. A sub-cavity which constitutes a part of the back surface of the main cavity around the entire outer periphery of the main cavity, and a movable core which advances and retreats into the sub-cavity inside the outer peripheral portion of the sub-cavity on the side opposite to the coating surface. After molding by injecting and filling the molten resin into the main cavity and the sub-cavity using an in-mold coating mold having a high-temperature portion at a position facing the movable core, the movable core is urged. In the state where the mold is opened, the coating agent is injected between the surface of the molded product and the mold cavity surface, and then re-clamped, and the coating agent is cured in the mold, An in-mold coating method, wherein a coating agent is closely adhered to and integrated with the surface of the thermoplastic resin molded article.