JPH08309789A - Mold for in-mold coating molding method and injection molding method using the same - Google Patents

Abstract

PURPOSE: To provide a mold not leaving the mark of a film raw material injection part on the surface of an injection molded product and preventing the leakage of a film raw material to the mating surface of the mold from the vicinity of the film raw material injection part. CONSTITUTION: A mold 10 used in an in-mold coating molding method consists of a fixed mold part 11 and a movable mold part 12 and is equipped with the main cavity 14 formed by both mold parts 11, 12 and the auxiliary cavity 20 communicating with the main cavity 14. A film raw material injection part 24 for injecting a film raw material into the boundary part of the resin in the main cavity and the mold surface of the main cavity or the space formed between the resin in the main cavity and the mold surface of the cavity is provided in the central region 21 of the auxiliary cavity 20 and the thickness of the auxiliary cavity from the central region 21 of the auxiliary cavity to the communication part 23 of the auxiliary cavity with the main cavity is larger than the thickness of the end part region of the auxiliary cavity.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can easily and surely form a film having various functions on the surface of an injection molded product.
The present invention relates to an injection molding method to which an in-mold coating molding method is applied and a mold used in the injection molding method.

[0002]

2. Description of the Related Art Various coatings may be formed on the surface of an injection-molded product for the purpose of modifying the surface characteristics of the injection-molded product made of a thermoplastic resin. Examples of such a film include a paint film, a hard coat film, an ultraviolet protection film, and an antifogging film. Usually, after manufacturing an injection-molded product by the injection molding method, a film having various functions is formed on the surface of the injection-molded product in another step. Examples of the method for forming the coating include spraying the coating raw material and immersing the injection-molded article in the liquid coating raw material. Due to such steps, there are various steps until a final product having a film formed on the surface is obtained. Therefore, in such an injection-molded product, there are major problems such as reduction of the manufacturing process up to the final product, reduction of manufacturing equipment, reduction of processing / processing time, reduction of manufacturing cost, and the like.

In-mold coating molding is one of the methods for solving the above problems and modifying the surface characteristics of an injection-molded article made of a thermoplastic resin in a short process and at low cost. For example, in Japanese Unexamined Patent Publication (Kokai) No. Hei 5-301251, a thermosetting paint is resin-molded after the completion of injection of a thermoplastic resin into a mold to reduce the mold clamping force of the mold or with the same mold clamping force. A technique of injecting between a painted surface of a product and a mold is disclosed. Alternatively, in Japanese Unexamined Patent Publication No. 5-318527, a thermoplastic resin is injection-molded, an uncured thermosetting resin is subsequently injected, and then the thermosetting resin is cured so that a part of the surface is thermosetting. A method for producing a molded body made of a thermoplastic resin coated with a resin is disclosed.

Any of these methods is a very effective method for forming a surface-modified film such as a coating film in the same mold on the surface of an injection-molded article made of a thermoplastic resin. However, these methods do not impair the appearance of the surface of the injection-molded product, and the coating raw material injected from the coating raw material injection portion of the various coating raw materials provided in the die is injected from the fitting portion of the die. There is no mention of a specific method for preventing leakage and reliably forming a film on the surface of the injection-molded article.

Further, in any of the methods disclosed in the above-mentioned respective publications, the coating material injection portion for injecting the coating material is provided on the mold surface of the cavity for molding the injection molded product. On the surface of the molded injection-molded product, a trace of the coating material injection portion remains, and the appearance of the surface of the injection-molded product is impaired.

As a method for solving such a problem that the trace of the coating material injection portion remains and the appearance of the surface of the injection-molded product is impaired, a method for injecting the coating material into the end region of the cavity provided in the mold is used. The method of providing the auxiliary cavity is
It is disclosed in Japanese Examined Patent Publication No. 4-9127. This method is extremely effective for compression molding such as SMC (sheet molding compound) as a method of leaving no trace of the coating material injection portion on the surface of the molded product and not impairing the appearance of the molded product. However, this publication does not describe any solution for preventing the leakage of the coating material from the fitting surface of the mold. In the compression molding method, burrs are unavoidable in the molded product due to the supplied molding material. Therefore, even if some coating material such as paint leaks to the fitting surface of the mold, a coating is formed on the burr of the molded product, and the coating material does not leak from the fitting surface of the mold. As described above, in the compression molding method, it is necessary to remove the burrs from the molded product, and it is not necessary to form a film only on the surface of the molded product.

[0007]

However, in the injection molding method using the thermoplastic resin, it is usually required that the injection molded product has no burr. Therefore, when the in-mold coating molding method is applied to the injection molding method using the thermoplastic resin,
If the coating material leaks from the mating surface of the mold, the mold is immediately contaminated. Therefore, it is necessary to remove the leaked coating material, and the productivity is significantly reduced. That is, if the techniques disclosed in the above-mentioned publications are simply applied to the in-mold coating molding method in the injection molding method using the thermoplastic resin, the problem that the trace of the coating material injection portion remains on the surface of the molded product, Also, the problem that the coating material leaks from the fitting surface of the mold cannot be solved at the same time.

Therefore, an object of the present invention is to provide an injection molding method to which the in-mold coating molding method is applied, in which traces of the coating material injection portion do not remain on the surface (coating surface) of the injection molded product, and the coating material is a coating film. It is an object of the present invention to provide a mold that does not leak from the raw material injecting section to the fitting surface of the mold, and an injection molding method using the mold.

[0009]

A mold of the present invention for achieving the above object is a mold having a fixed mold part and a movable mold part used in an in-mold coating molding method. A main cavity formed by the fixed mold part and the movable mold part and an auxiliary cavity communicating with the main cavity, and the resin injected into the main cavity and the main cavity in the central region of the auxiliary cavity. An auxiliary cavity is provided with a coating material injection part for injecting the coating material into the space formed between the resin injected into the main cavity or the resin surface injected into the main cavity and the mold surface of the main cavity. The cavity thickness of the auxiliary cavity extending from the central region to the communicating portion between the auxiliary cavity and the main cavity is thicker than the cavity thickness of the end region of the auxiliary cavity.

A first aspect of the present invention for achieving the above object
The injection molding method according to the aspect includes a main cavity formed by a fixed mold section and a movable mold section, and an auxiliary cavity communicating with the main cavity, and a central cavity of the auxiliary cavity has a main cavity inside the main cavity. A coating material injection section for injecting a coating material is provided at the boundary between the injected resin and the mold surface of the main cavity, and the coating material injection section is provided from the central region of the auxiliary cavity to the communication section between the auxiliary cavity and the main cavity. An injection molding method using a mold in which the cavity thickness of the auxiliary cavity is thicker than the cavity thickness of the end region of the auxiliary cavity, wherein after the molten resin made of a thermoplastic resin is injected into the main cavity, Mold internal pressure generated by the resin injected into the cavity is 0kg / cm
It is characterized in that the coating material is injected into the boundary from the coating material injection portion in a state higher than ^2- G.

In the injection molding method according to the first aspect of the present invention, (A) the first mode in which the mold clamping force of the mold is kept constant (B) the mold clamping force of the mold is The second mode in which the mold clamping force at the time of injecting the molten resin is reduced before the injection (C) The mold clamping force at the die is more than the mold clamping force at the time of injecting the molten resin before injecting the coating material. Decrease and then
After separating the movable mold part from the fixed mold part with the cavity formed by the fixed mold part and the movable mold part, the coating material is injected into the boundary between the resin in the main cavity and the mold surface of the main cavity. The third form can be mentioned. In all of these cases, the coating material is injected into the boundary between the resin in the main cavity and the mold surface of the main cavity with the mold internal pressure higher than 0 kg / cm ² -G.

In the injection molding method according to the first aspect of the present invention, the mold pressure P (kg / cm) at the time of injecting the coating material is
It is desirable that the value of ( ^2- G) satisfies 0 <P ≦ 500 kg / cm ² -G, and more preferably 0 <P ≦ 300 kg / cm ² -G. Alternatively, after injecting the coating material, the mold pressure at the time when the coating material is solidified is P '(kg / c
m ² −G), it is desirable that 0 <P ′. When the value of P or P ′ decreases to 0 kg / cm ² -G, depending on the type of thermoplastic resin used, it becomes impossible to continue to pressurize the resin in the main cavity or the injected coating material, and the coating surface There are cases where the transferability of the mold surface of the main cavity to the mold becomes insufficient, and the adhesion of the film to the thermoplastic resin decreases. On the other hand, P
When the value of exceeds 500 kg / cm ² -G, the coating material easily flows into the easily contractible portion of the molten resin, and as a result, the thickness of the coating is reduced, the thickness is uneven, or the coating is an injection molded product. There is a problem that it is formed only in a part of. However, by setting the value of P or P ′ as described above, the coating material can be surely injected into the boundary between the resin in the main cavity and the mold surface of the main cavity.

In the injection molding method according to the first aspect of the present invention, the pressure holding period after injecting the molten resin made of the thermoplastic resin into the main cavity provided in the mold is 3 seconds or more, The holding pressure is preferably 300 kg / cm ² -G or more. Holding pressure is 300 kg / cm ² -G
If the pressure holding period is less than 3 seconds and the holding pressure period is less than 3 seconds, the mold internal pressure P at the time of injecting the coating material may depend on the type of thermoplastic resin used
Is easily reduced to 0 kg / cm ² -G. If the mold internal pressure decreases in this way, it will not be possible to continue to pressurize the resin in the main cavity or the injected coating material, resulting in insufficient transferability of the mold surface of the main cavity to the coating surface, The adhesion of the film to the plastic resin may decrease. However, if the holding pressure and the holding pressure are set to the values described above, the main cavity is overfilled with the resin, and the coating material is injected with the mold pressure higher than 0 kg / cm ² -G. You can, and
The coating material injected at the boundary between the resin in the main cavity and the mold surface of the main cavity can be continuously pressurized.

If the injection of the coating material is started before the end of the holding pressure period, there is a risk that the molten resin in the auxiliary cavity will flow into the apparatus for injecting the coating material. Therefore, such a risk can be avoided by starting the injection of the coating material at the same time as or after the end of the pressure holding period. In addition, it is preferable to start the injection of the coating material within 5 seconds after the end of the holding pressure period.
It is possible to further improve the adhesion of the film to the thermoplastic resin.

The mold internal pressure can be measured by mounting a pressure sensor on the mold surface of the main cavity. Further, the holding pressure refers to a work of continuously applying pressure to the molten resin in the main cavity from a resin injection portion such as a gate portion provided in the mold after injecting the molten resin, and thereby, the volume of the main cavity or more can be obtained. Of molten resin is introduced into the main cavity. The pressure applied to the molten resin at this time is a holding pressure. The predetermined period means a pressure-holding period (pressure-holding time), which is a period (time) from when a predetermined amount of the molten resin is injected until the weight of the molded product does not increase even if the pressure is further held.

Alternatively, in the injection molding method according to the second aspect of the present invention for achieving the above object, a main cavity formed by a fixed mold part and a movable mold part and communicating with the main cavity. And a coating material injection section is provided in the central region of the auxiliary cavity,
By an injection molding method using a mold in which the cavity thickness of the auxiliary cavity extending from the central region of the auxiliary cavity to the communicating portion between the auxiliary cavity and the main cavity is thicker than the cavity thickness of the end region of the auxiliary cavity. There
(A) a step of injecting a molten resin made of a thermoplastic resin into the main cavity while holding the mold with a predetermined mold clamping force, and (b) a step of holding pressure for a predetermined period,
(C) By reducing the mold clamping force of the mold, the resin in the main cavity and the mold surface of the main cavity and between the resin in the auxiliary cavity and the central region of the auxiliary cavity are connected to the communicating portion. A step of forming a space between the auxiliary cavity and the mold surface, and then injecting a coating material into the space from a coating material injection part. In this case, the thermoplastic resin preferably comprises a non-reinforced amorphous resin or amorphous alloy resin.

In the step (c), the mold clamping force may be released when the mold clamping force is reduced, and the fixed mold part and the movable mold part of the mold may be separated from each other.

The mold clamping force in the step (a) is F ₀ ,
When the mold clamping force after reduction in the step (c) is F ₁ , 0 ≦ F ₁ / F ₀ ≦ 0.3, more preferably 0 ≦ F ₁
It is desirable that / F ₀ ≦ 0.1. If the value of F ₁ / F ₀ exceeds 0.3, depending on the type of thermoplastic resin used, the compression state of the resin in the main cavity that occurs during injection of the coating material will be non-uniform and the thickness of the coating will be non-uniform. Or a film may be formed only on a part of the injection molded product.

Further, it is desirable that the time from the end of the pressure holding period to the injection of the coating material is 10 to 120 seconds. Further, it is desirable that the mold clamping force is reduced within 10 seconds before the coating material is injected.

In the mold of the present invention or in the injection molding method of the present invention, the auxiliary cavity and the main cavity are formed in the mold surface of the auxiliary cavity on the side where the coating material is injected, from the central region of the auxiliary cavity. It is preferable that there is no step due to the difference between the thickness of the cavity over the communicating portion and the thickness of the cavity in the end region of the auxiliary cavity.
Note that, hereinafter, the communicating portion between the auxiliary cavity and the main cavity may be simply referred to as the communicating portion. The mold surface of the auxiliary cavity on the side where the coating material is injected from the central region of the auxiliary cavity to the communicating portion may be flat or curved, and in some cases, such metal mold may be used. Concavities and convexities may be formed on the mold surface from the central region of the auxiliary cavity toward the communicating portion.

Further, the cavity thickness in the end region of the auxiliary cavity is 1.5 mm or less, and the cavity thickness in the central region of the auxiliary cavity is 2.0 mm or more, more preferably 3.0 mm or more. desirable. The lower limit of the cavity thickness in the end region of the auxiliary cavity is any thickness as long as the injected molten resin is filled and the injected coating material does not leak from the end region of the auxiliary cavity. However, it is preferably about 0.5 mm. The upper limit of the cavity thickness in the central region of the auxiliary cavity depends on the size of the main cavity.
About 0 mm is sufficient. The thickness of the cavity extending from the central region of the auxiliary cavity to the communicating portion need not be constant. For example, the cavity thickness of the central region may be gradually increased from the central region where the coating material injection part is provided toward the communication part, or the cavity of the auxiliary cavity at the part connecting the coating material injection part and the communication part. Maximum thickness,
The cavity thickness in the central region may be reduced along a direction substantially perpendicular to the direction connecting the coating material injection part and the communication part.

Alternatively, in order to prevent the coating material from leaking from the coating material injection portion to the fitting surface of the die more reliably, the die on the side where the coating material is injected in the end region of the auxiliary cavity is injected. A groove (hereinafter,
(Sometimes referred to as a coating material outflow prevention groove) may be provided. In this case, the width of the groove is 3 mm or less,
The depth is preferably 0.2 mm or more. The lower limit of the width of the coating material outflow prevention groove may be about 0.3 mm,
The upper limit of the depth may be about 5 mm.

As the thermoplastic resin applicable to the injection molding method according to the first aspect of the present invention, polystyrene (P
S) resin, high impact polystyrene (HIPS) resin, acrylonitrile-butadiene-styrene copolymer (AB
S) resin, polypropylene (PP) resin, general-purpose resin such as polymethylmethacrylate (PMMA) resin, polycarbonate (PC) resin, modified polyphenylene ether (PPE) resin, polyamide (PA) resin, polyethylene terephthalate (PET) resin, poly Engineering plastics such as butylene terephthalate (PBT) resin, polyphenylene sulfide (PPS) resin, liquid crystal polyester resin, etc., or polymer alloys by a combination thereof, and further, these materials containing polymer alloys are used as fiber-based fillers and scale-like fillers. Although a composite material reinforced by the like may be used, it is particularly effective to use a reinforced crystalline resin or a crystalline resin alloy material, or a crystalline resin-rich resin alloy material. The thermoplastic resin used is not particularly limited, but may be limited depending on the compatibility with the coating material used. Here, whether or not the thermoplastic resin is a crystalline thermoplastic resin is generally judged by whether or not a clear melting point (a temperature showing a sharp endotherm) is confirmed by a differential scanning calorimetry (DSC) method. It A resin having a clear melting point is a crystalline thermoplastic resin.

As the thermoplastic resin applicable to the injection molding method according to the second aspect of the present invention, polystyrene (P
S) resin, high impact polystyrene (HIPS) resin, acrylonitrile-butadiene-styrene copolymer (AB
S) resin, polypropylene (PP) resin, general-purpose resin such as polymethylmethacrylate (PMMA) resin, polycarbonate (PC) resin, modified polyphenylene ether (PPE) resin, polyamide (PA) resin, polyethylene terephthalate (PET) resin, poly Engineering plastics such as butylene terephthalate (PBT) resin, polyphenylene sulfide (PPS) resin, liquid crystal polyester resin, etc., or polymer alloys by a combination thereof, and further, these materials containing polymer alloys are used as fiber-based fillers and scale-like fillers. Although a composite material reinforced with a non-reinforced amorphous thermoplastic resin or an amorphous resin-rich non-reinforced polymer alloy may be used, it is particularly effective. The thermoplastic resin used is not particularly limited, but may be limited depending on the compatibility with the coating material used. here,
Whether or not the thermoplastic resin is an amorphous thermoplastic resin is generally judged by whether or not a clear melting point (a temperature showing a sharp endotherm) is confirmed by a differential scanning calorimetry (DSC) method. The resin for which a clear melting point is not confirmed is an amorphous thermoplastic resin.

As the coating material applicable to the first or second injection molding method of the present invention, oxidative polymerization type paints such as alkyd resin type, epoxy resin ester type and fatty acid modified urethane resin type, epoxy resin type and polyurethane are used. -Based, unsaturated polyester-based multi-liquid reactive coatings, alkyd resin-based, epoxy resin-based, polyurethane-based, vinyl resin-based heat-curable coatings, epoxy acrylate oligomers,
Urethane acrylate oligomers, polyester acrylate oligomers, radical polymerization type paints consisting of these oligomers and ethylenically unsaturated monomers, or various kinds of these paints mixed with metal powder, special pigments, special additives such as UV absorbers, etc. Examples thereof include functional coatings, fluororesin-based lacquers, silicone resin-based lacquers, hard coating agents such as silane-based hard coating agents, and the like.

The first aspect of the present invention is based on the shape of the injection molded product to be molded, the type of thermoplastic resin used, the type of coating material used, the injection molding apparatus used, the injection molding conditions, etc.
Either the injection molding method according to the second aspect or the injection molding method according to the second aspect may be selected.

In the injection molding method according to the first and second aspects of the present invention, the coating material may be injected while the mold is slightly opened. Furthermore, in the injection molding method according to the second aspect of the present invention, when the mold clamping force is reduced and the injection is performed, a corresponding mold opening amount is also observed in this step. Therefore, in the mold of the present invention, with respect to the entire cavity including the auxiliary cavity, even if the fixed mold part and the movable mold part are separated by the total value of these mold opening amounts,
It is desirable to have a mating structure in which the main and auxiliary cavities are formed and maintained.

[0028]

When the in-mold coating molding method is applied to the injection molding method using the thermoplastic resin, there are roughly two kinds of coating material injection methods. The first coating material injection method is a spaceless injection method in which the coating material is injected without forming a space between the resin injected into the cavity and the mold surface of the cavity,
This method corresponds to the injection molding method according to the first aspect of the present invention. The second film material injection method is a space injection method in which a space is formed between the resin injected into the cavity and the mold surface of the cavity, and the film material is injected into this space. Corresponds to the injection molding method according to the second aspect of the present invention.

In the injection molding method according to the first aspect of the present invention, the coating material is injected with the mold pressure of 0 kg / cm ² -G or more. On the other hand, in the injection molding method according to the second aspect of the present invention, the mold pressure is 0 kg / cm ² -G.
After that, the coating material is injected. Generally, the injection molding method according to the first aspect of the invention provides better coating properties, but in the case of non-reinforced amorphous resin systems, the injection molding method according to the second aspect of the invention. The coating properties tend to be better. Depending on the shape of the main cavity, the type of thermoplastic resin used, and the type of coating raw material used, the mold clamping force may be the same or reduced, or the mold clamping force may be released and the molds may be separated from each other. Inject the coating material in any of the states.

Now, in the injection molding method according to the first aspect of the present invention, the injected coating material is used to compress the resin in the cavity while slightly opening the mold, and Flows into the boundaries of. on the other hand,
In the injection molding method according to the second aspect of the present invention, the injected coating material fills the space volume, and while compressing the resin in the cavity while slightly opening the mold, It flows into the space formed between the cavity and the cavity.

As described above, in any case, the injected coating material coats the surface of the resin while compressing the resin in the cavity to some extent. The compression amount of the resin at this time is larger as the thickness of the molded product, in other words, the cavity thickness of the cavity is larger.

The mold or injection molding method of the present invention skillfully utilizes this tendency. That is, since the auxiliary cavity communicating with the main cavity formed by the fixed mold section and the movable mold section is provided, and the coating material injection section is provided in the central region of the auxiliary cavity, the trace of the coating material injection section remains. It can be prevented from remaining on the surface of the molded product formed by the main cavity. Further, since the cavity thickness of the auxiliary cavity extending from the central region of the auxiliary cavity to the communicating portion is thicker than the cavity thickness of the end region of the auxiliary cavity, the coating material injected from the coating material injecting portion is selectively The central region of the auxiliary cavity, which is a thick wall portion, is covered with almost no flow toward the end region of the auxiliary cavity. Therefore, it is possible to effectively prevent the coating material injected from the coating material injection portion from leaking from the end region of the auxiliary cavity to the fitting surface of the mold.

[0033]

EXAMPLES The mold and injection molding method of the present invention will be described below with reference to the drawings, but the present invention is not limited to these examples.

Example 1 Example 1 relates to the injection molding method according to the first aspect of the present invention. A schematic cross-sectional view of the mold 10 in Example 1 is shown in FIG. The shapes of the main cavity 14 and the auxiliary cavity 20 are shown in the schematic perspective view of FIG. Also, lines AA, BB and C in FIG.
Main cavity 14 and auxiliary cavity 20 along C
A schematic cross-sectional view of the portion is shown in FIGS. 3, 4 and 5.

The mold 10 of Example 1 has a main cavity 14 formed by a fixed mold part 11 and a movable mold part 12. The mold 10 further includes an auxiliary cavity 20 formed by the fixed mold portion 11 and the movable mold portion 12 and communicating with the main cavity 14. Then, in the central region 21 of the auxiliary cavity 20, a coating material injection portion 24 for injecting a coating material is provided. The cavity thickness extending from the central region 21 of the auxiliary cavity 20 to the communicating portion 23 between the auxiliary cavity 20 and the main cavity 14 is thicker than the cavity thickness of the end region 22 of the auxiliary cavity 20. In the figure, reference numeral 13 is a fitting portion between the fixed mold portion 11 and the movable mold portion 12, and reference numeral 15
Is a gate portion, and reference numeral 30 is a known coating material injection device.

The shape of the auxiliary cavity 20 is as follows. The central region 21 of the auxiliary cavity 20 is
Communication part 23 between auxiliary cavity 20 and main cavity 14
It is surrounded by the end region 22 except for a considerable portion of. Further, in the mold surface 20A of the auxiliary cavity on the side where the coating material is injected, the central region 21 of the auxiliary cavity 20 is formed.
There is no step due to the difference between the cavity thickness extending from the end to the communicating portion 23 and the cavity thickness of the end region 22 of the auxiliary cavity, and it is flat. The cavity thickness of the central region 21 was constant. [Dimensions of Auxiliary Cavity] Width (W): 30 mm Length (L): 30 mm Thickness of end region (T ₁ ): 1.2 mm Thickness of central region (T ₂ ): 2.8 mm

The shape of the main cavity 14 is approximately 100 m in length.
m × width 30 mm × depth 10 mm × wall thickness 3 mm. The injection molded product has a box shape.

As an injection molding device, I manufactured by Toshiba Machine Co., Ltd.
Using S100 molding machine (maximum mold clamping force 100 ton f),
The injection molding method according to the first aspect of the present invention is executed. The injection molding method according to the first aspect of the present invention will be described below with reference to FIGS. 6 and 7 which are schematic cross-sectional views of a mold and the like. The injection molding device is not shown in FIGS. 6 and 7.

After the mold was closed and the mold was clamped with a mold clamping force of 100 tons f, a molten resin 40 made of a thermoplastic resin was injected into the main cavity 14 through the gate portion 15 and filled. The injected molten resin 40 flows into the auxiliary cavity 20 via the communicating portion 23,
Was also filled with molten resin 40 (see FIG. 6). The injection conditions etc. are shown below. After the injection of the predetermined amount of the molten resin 40 was completed, the pressure holding step was performed. [Thermoplastic resin used] Polyamide MXD6 resin Rennie 1022H manufactured by Mitsubishi Engineering Plastics Co., Ltd. [Mold temperature, molten resin injection conditions, pressure holding conditions] Movable mold part: 120 ° C Fixed mold part: 120 ° C resin temperature: 280 ° C injection pressure: 1000 kg / cm ² -G holding pressure: between 800 kg / cm ² -G dwell time: 9 seconds

After the pressure holding step was completed, the mold clamping force was reduced. The conditions for reducing the mold clamping force are as follows. The mold internal pressure generated by the resin injected into the main cavity 14 after the mold clamping force was reduced was about 220 kg / cm ² -G immediately before the injection of the coating material. [Clamping force reduction condition] Clamping force after reduction: Approximately 5 tons f Reduction started: Immediately after the pressure holding process ends

Next, in a state where no space is formed between the mold surface of the main cavity 14 and the resin injected into the main cavity 14, the coating material injection part 24 provided in the central region 21 of the auxiliary cavity 20. From the coating material injection device 30
Using the above, a predetermined amount of the coating material 41 was injected into the boundary between the thermoplastic resin in the main cavity 14 and the mold surface of the main cavity 14 (see FIG. 7). The film to be formed is a paint film, the composition of which is exemplified below. Coating material 4
The injection of 1 is immediately after the completion of the mold clamping force reduction, and the injection time is 1.5
Seconds Further, the injection pressure of the coating material 41 is about 350-
It was 400 kg / cm ² -G. [Composition of coating material as coating material] Urethane acrylate oligomer: 12 parts by weight Epoxy acrylate oligomer: 20 parts by weight Styrene: 20 parts by weight Zinc stearate: 0.5 parts by weight 8% Cobalt octylate: 0.5 parts by weight Titanium oxide: 10 parts by weight Talc: 15 parts by weight Calcium carbonate: 20 parts by weight t-butyl peroxybenzoate: 2 parts by weight

70 seconds after the injection of the coating material 41, an injection molded article made of a thermoplastic resin, whose schematic perspective view is shown in FIG. 8A, was taken out from the mold. The entire outer surface of the injection-molded product 50 is covered with a cured film 55.
The film thickness of No. 5 was about 50 μm on average. The film 55 covered the injection molded part 52 corresponding to the central region 21 of the auxiliary cavity 20 and the injection molded part 51 corresponding to the main cavity 14. Further, although a part of the injection-molded product portion 53 corresponding to the end region 22 of the auxiliary cavity 20 is covered with the film 55, a film is formed on the injection-molded product part 54 near the fitting portion 13 of the mold. Had not formed. This is because the cavity thickness of the auxiliary cavity 20 extending from the central region 21 of the auxiliary cavity 20 to the communicating portion 23 is thicker than the cavity thickness of the end region 22 of the auxiliary cavity 20, so that the injection from the coating material injection portion 24 is performed. This is because the formed coating material 41 selectively flows from the central region 21 of the auxiliary cavity 20 which is a thick portion to the communication portion 23, and hardly flows toward the end region 22 of the auxiliary cavity 20. . The parts 52, 53, 54 of the injection-molded product molded by the auxiliary cavity 20 are finally cut and removed.

FIG. 9 shows the mold internal pressure in the central portion of the main cavity 14 and the movement of the movable mold portion 12 in this series of injection of molten resin and injection of the coating material. In addition, in FIG. 9, the solid line indicates the mold internal pressure, and the broken line indicates the displacement amount of the movable mold part.

Example 2 In Example 2, the mold structure and size were the same as in Example 1 except that the thickness (T ₂ ) of the central region of the auxiliary cavity was 3.5 mm. ,
The same thermoplastic resin as in Example 1 was used, and the injection conditions of the molten resin and the injection conditions of the coating material were the same as in Example 1. A schematic perspective view of the obtained injection-molded article made of the thermoplastic resin is shown in FIG. The entire outer surface of the injection-molded product 50 is covered with a cured film 55.
The average film thickness was about 50 μm. The film 55 covered the injection molded part 52 corresponding to the central region 21 of the auxiliary cavity 20 and the injection molded part 51 corresponding to the main cavity 14. Further, in Example 2, since the thickness (T ₂ ) of the central region of the auxiliary cavity is thicker than that of Example 1, unlike Example 1, the auxiliary cavity 2
The portion 53 of the injection-molded product corresponding to the end region 22 of 0 is
It was not covered with the film 55.

(Embodiment 3) Embodiment 3 is a modification of Embodiment 1 and prevents the coating material from flowing out to the mold surface 20A of the end region 22 of the auxiliary cavity 20 on the side where the coating material is injected. A groove 25 (coating material outflow prevention groove 25) is provided. The shape of the auxiliary cavity 20 was as follows. The structure and size of the mold are the same as in Example 1 except that the coating material outflow prevention groove 25 is provided. A schematic cross-sectional view of the mold 10 in Example 3 is shown in FIG. The shapes of the main cavity and the auxiliary cavity are shown in the schematic perspective view of FIG.

The central region 21 of the auxiliary cavity 20 is surrounded by the end region 22 except for a considerable portion of the communicating portion 23. In addition, on the mold surface 20A of the auxiliary cavity on the side where the coating material is injected, the cavity thickness extending from the central region 21 of the auxiliary cavity 20 to the communicating portion 23,
There is no step due to the difference in cavity thickness of the end region 22 of the auxiliary cavity 20, and it is flat. The cavity thickness of the central region 21 was constant. [Dimension of Auxiliary Cavity] Width: 30 mm Length: 30 mm Thickness of end region: 1.2 mm Thickness of central region: 2.8 mm

The size of the coating material outflow prevention groove 25 is shown below. The coating material outflow prevention groove 25 has a portion corresponding to the communicating portion 23 between the auxiliary cavity 20 and the main cavity 14 on the mold surface 20A of the end region 22 of the auxiliary cavity 20 on the side where the coating material is injected. It is provided so as to surround the central region 21 of the auxiliary cavity 20. [Coating material outflow preventing grooves of Dimensions width (W _0): 0.5mm depth (D _0): 1mm

In Example 3, the same thermoplastic resin as in Example 1 was used, and the injection conditions of the molten resin and the injection conditions of the coating material were the same as in Example 1.

FIG. 12 shows a schematic perspective view of a molded injection-molded article. The cured film 55 covers the entire outer surface of the injection-molded product 50, and the film thickness of the film 55 is about 50 μm on average.
It was m. The coating 50 is an auxiliary cavity 20 surrounded by a thin rib 56 formed by a coating material outflow prevention groove.
The injection-molded part 52 corresponding to the central region 21 and the injection-molded part 51 corresponding to the main cavity 14 were covered. Further, the portion 53 of the injection molded product corresponding to the end region 22 of the auxiliary cavity 20 outside the thin rib 56 was not covered with the film 55. Furthermore, no film was formed on the portion 54 of the injection-molded product near the fitting portion 13 of the mold.

(Embodiment 4) Embodiment 4 is also a modification of Embodiment 1. In Example 4, the same injection molding apparatus and mold as in Example 1 were used, a thermoplastic resin was injected into the main cavity 14 under the injection conditions shown below, and the main cavity 14 and the auxiliary cavity 20 were made of molten resin. After filling, the pressure-holding operation was performed. [The thermoplastic resin used] PBT resin Novadur 501 manufactured by Mitsubishi Engineering Plastics Co., Ltd.
0R5 [Mold temperature and molten resin injection condition, pressure holding condition] Movable mold part: 120 ° C Fixed mold part: 120 ° C Resin temperature: 240 ° C Injection pressure: 1000kg / cm ² -G Holding pressure : 600 kg / cm ² -G Holding time: 10 seconds

After the pressure-holding step, unlike the first embodiment, in the same mold clamping force, no space is formed between the mold surface of the main cavity 14 and the resin injected into the main cavity 14. Then, using the same coating material injection device as in Example 1, a predetermined amount of the same coating material as in Example 1 was applied to the boundary between the mold surface of the main cavity 14 and the resin injected into the main cavity 14. Injected. The coating material was injected immediately after the pressure holding operation was completed, and the injection time was 1.5 seconds. Further, the injection pressure of the coating material is about 330 to 380 kg / cm ² -G
And The mold pressure immediately before the coating material was injected was about 150k.
It was g / cm ² -G.

70 seconds after the injection of the coating material, the injection-molded article made of the thermoplastic resin was taken out of the mold. The surface of the injection-molded product was covered with a cured film, and the film thickness of the film was about 50 μm on average. The coating covered the injection-molded part corresponding to the central region of the auxiliary cavity and the injection-molded part corresponding to the main cavity. on the other hand,
No film was formed on the part of the injection molded product corresponding to the end region of the auxiliary cavity and the part of the injection molded product corresponding to the fitting part of the mold.

Example 5 Example 5 relates to the injection molding method according to the second aspect of the present invention. Also in Example 5, the same injection molding apparatus as in Example 1 was used. The structures of the mold and the auxiliary cavity 20 in the fifth embodiment are the same as those in the first embodiment.

Hereinafter, the injection molding method according to the second aspect of the present invention will be described with reference to FIGS. 6, 13 and 7 which are schematic sectional views of a mold and the like.

First, a molten resin made of a thermoplastic resin is injected into the main cavity 14 while holding the mold with a predetermined mold clamping force (100 ton f), and is injected into the main cavity 14 and the auxiliary cavity 20. Filled with molten resin. The injected molten resin 40 flowed into the auxiliary cavity 20 via the communicating portion 23, and the auxiliary cavity 20 was also filled with the molten resin 40 (see FIG. 6). The injection conditions are shown below. [Thermoplastic resin used] PC / PET alloy resin Iupilon MB2112 manufactured by Mitsubishi Engineering Plastics Co., Ltd. [Mold temperature and injection conditions] Movable mold part: 120 ° C Fixed mold part: 120 ° C Resin temperature: 280 ° C Injection pressure: 1000kg / cm ² -G

After the injection of the molten resin 40 was completed, the pressure was maintained for a predetermined period. Holding pressure is 500 kg / cm ² −
G, holding pressure time was 10 seconds.

After the pressure holding step was completed, the mold clamping force was reduced. The mold clamping force after the reduction was set to about 5 tons f, and the reduction start time was set to 20 seconds after the end of the pressure holding process. At this time, the mold pressure is 0 kg /
cm ² −G, a space 42 is formed between the resin 40 in the main cavity 14 and the mold surface of the main cavity 14,
In addition, a space 43 is formed between the resin 40 in the auxiliary cavity 20 and the mold surface 20A of the auxiliary cavity extending from the central region 21 of the auxiliary cavity 20 to the communicating portion 23 (see FIG. 13).

Then, the same coating material 41 as in Example 1 was used.
The coating material 41 was injected into the spaces 42 and 43 from the coating material injection part 24 (see FIG. 7). The conditions for injecting the coating material 41 were as follows. The injection pressure of the coating material 41 was set to about 20 to 50 kg / cm ² -G. [Injection conditions for coating material] Injection start time: Immediately after completion of mold clamping force reduction Injection time: 1.5 seconds

70 seconds after the injection of the coating material, the injection molded article made of the thermoplastic resin was taken out of the mold. The surface of the injection-molded product was covered with a cured film, and the film thickness of the film was about 50 μm on average. The coating covered the injection-molded part corresponding to the central region 21 of the auxiliary cavity 20 and the injection-molded part corresponding to the main cavity 14. However, the end region 2 of the auxiliary cavity 20
No film was formed on the portion 53 of the injection-molded product corresponding to 2 and the portion of the injection-molded product near the fitting portion 13 of the mold. This is because the cavity thickness of the auxiliary cavity 20 extending from the central region 21 of the auxiliary cavity 20 to the communication portion 23 is thicker than the cavity thickness of the end region 22 of the auxiliary cavity 20, and thus the central region 21 of the auxiliary cavity 20. A space 43 is formed between the mold surface 20A of the auxiliary cavity 20 and the resin in the auxiliary cavity 20 so as to extend from the space 23 to the communication portion 23, and the coating material 41 selectively flows in the space 43, and the auxiliary cavity 20 This is because there is almost no flow toward the end region 22 of.

(Comparative Example 1) In Comparative Example 1, a main cavity 14 having a schematic perspective view shown in FIG.
And using a mold provided with the auxiliary cavity 20,
And, except that the following coating material injection conditions are different,
Injection of molten resin into the main cavity 14, the main cavity 14 and the auxiliary cavity 2 under the same method and conditions as in Example 1.
Filling of molten resin into 0, reduction of mold clamping pressure, injection of film raw material, and curing were performed. The mold used was the same as the mold used in Example 1 except for the shape of the auxiliary cavity 20.
In Comparative Example 1, the cavity thickness (T) of the auxiliary cavity 20 was constant. [Shape of Auxiliary Cavity] Width (W): 30 mm Length (L): 30 mm Thickness (T): 2.8 mm [Conditions for Injecting Coating Raw Material] Injection start time: Immediately after completion of reduction of mold clamping force Injection time: 1 .5 seconds Curing time: 70 seconds Mold pressure immediately before injection of coating material: about 220 kg / cm ² -G Injection pressure of coating material: about 300 to 350 kg / c
m ² -G

70 seconds after the injection of the coating material, the injection-molded article made of the thermoplastic resin was taken out of the mold. The entire outer surface of the injection-molded product was covered with a cured film, and the film thickness of the film was about 30 μm on average. It should be noted that almost the entire outer surface of the injection-molded product corresponding to the auxiliary cavity 20 was also covered with a film, and a hardened film that was considered to have flowed out from the auxiliary cavity 20 was confirmed in the fitting portion 13 of the mold. .

COMPARATIVE EXAMPLE 2 In Comparative Example 2, the main cavity 14 having a schematic perspective view shown in FIG.
In addition, except that a mold provided with the auxiliary cavity 20 is used, the molten resin is injected into the main cavity 14 and the molten resin is filled into the main cavity 14 and the auxiliary cavity 20 by the same method and conditions as in Example 1. The mold clamping pressure was reduced, the coating material was injected, and the coating was cured. The mold used was the same as the mold used in Example 1 except for the shape of the auxiliary cavity 20. 1 is a schematic cross-sectional view of a mold 10 in Comparative Example 2.
5 shows.

The shape of the auxiliary cavity 20 in Comparative Example 2 was as follows. The end region 22 of the auxiliary cavity 20 is different from that of the first embodiment in that the fitting portion 13 of the mold is
Is formed only toward the center region 21 of the auxiliary cavity 20 and is not surrounded by the end region 22. That is, the central region 21 extends to the edge of the auxiliary cavity 20 along a direction substantially perpendicular to the direction connecting the coating material injection part 24 and the communication part 23. The cavity thickness of the central region 21 was constant. [Dimensions of Auxiliary Cavity] Width (W): 30 mm Length (L): 30 mm Thickness of end region (T ₁ ): 1.2 mm Thickness of central region (T ₂ ): 2.8 mm

FIG. 16 shows a schematic perspective view of the molded injection-molded article 50. The cured film 55 is an injection molded product 50.
Covers the entire outer surface of the film, and the film thickness of the film 55 is about 3 on average.
It was 0 μm. It should be noted that almost the entire outer surface of the injection-molded product corresponding to the auxiliary cavity 20 was also covered with a film, and a hardened film that was considered to have flowed out from the auxiliary cavity 20 was confirmed in the fitting portion 13 of the mold. .

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The conditions and materials used in the examples are mere examples and can be changed as appropriate. Further, the structures of the injection molding device and the mold are also examples, and the design can be appropriately changed. The shape and size of the auxiliary cavity and the arrangement position with respect to the main cavity are also examples, and the design can be appropriately changed depending on the shape of the injection-molded product to be molded.
In the mold described in the embodiment, the coating material injecting device 30 is attached to the fixed die portion 11, but the coating material injecting device 30 may be attached to the movable die portion 12.
As a result, for example, a film can be formed on the inner surface of a box-shaped injection molded product. Furthermore, if the coating material injection device 30 is attached to each of the fixed mold portion 11 and the movable mold portion 12, for example, a coating can be formed on both the front side and the inner surface of a box-shaped injection molded product.

[0066]

EFFECTS OF THE INVENTION According to the present invention, no trace of the coating material injection portion remains on the surface of the molded product. Moreover, by defining the cavity thickness in the central region and the end region of the auxiliary cavity, it is possible to reliably prevent the coating material from leaking from the coating material injection portion to the fitting surface of the mold.
Furthermore, by providing a coating material outflow prevention groove on the die surface on the side where the coating material is injected in the end region of the auxiliary cavity, the coating material can be more reliably transferred from the coating material injection part to the fitting surface of the die. It can be prevented from leaking out.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a mold according to a first embodiment.

FIG. 2 is a schematic perspective view showing the shapes of a main cavity and an auxiliary cavity in the first embodiment.

FIG. 3 is a schematic cross-sectional view of a main cavity and an auxiliary cavity according to the first embodiment.

FIG. 4 is a schematic cross-sectional view of the main cavity and the auxiliary cavity according to the first embodiment at a position different from that of FIG.

5 is a first example in a position different from those in FIGS. 3 and 4;
3 is a schematic cross-sectional view of a main cavity and an auxiliary cavity in FIG.

FIG. 6 is a schematic cross-sectional view of a mold or the like for explaining the injection molding method of Example 1.

7 is a schematic cross-sectional view of the mold and the like for explaining the injection molding method of the first embodiment, following FIG.

FIG. 8 is a schematic perspective view of injection-molded articles in Examples 1 and 2.

FIG. 9 is a diagram showing a mold internal pressure and a moving state of a movable mold part in a central portion of a main cavity in a process of injecting a molten resin and injecting a coating material in Example 1.

FIG. 10 is a schematic sectional view of a mold according to a third embodiment.

FIG. 11 is a schematic perspective view showing the shapes of a main cavity and an auxiliary cavity in Example 3.

FIG. 12 is a schematic perspective view of an injection-molded article in Example 3.

FIG. 13 is a schematic cross-sectional view of a mold and the like for explaining the injection molding method of Example 5.

14 is a schematic perspective view showing the shapes of a main cavity and an auxiliary cavity in Comparative Example 1. FIG.

15 is a schematic perspective view showing the shapes of a main cavity and an auxiliary cavity in Comparative Example 2. FIG.

16 is a schematic perspective view of an injection molded product in Comparative Example 2. FIG.

[Explanation of symbols]

 10 Mold 11 Fixed Mold Part 12 Movable Mold Part 13 Fitting Part of Fixed Mold Part and Movable Mold Part 14 Main Cavity 15 Gate Part 20 Auxiliary Cavity 21 Central Area of Auxiliary Cavity 22 End Area of Auxiliary Cavity 23 communication part 24 coating material injection part 25 coating material outflow prevention groove 30 coating material injection device 40 molten resin 41 coating material 50 injection molded product 55 coating 56 thin rib

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Izumida 5-6-2 Higashihachiman, Hiratsuka City, Kanagawa Sanryo Engineering Plastics Co., Ltd. Technical Center (72) Yoshiaki Yamamoto Mitsufuchi, Komaki City, Aichi Prefecture Nishinomon 878 Dainippon Paint Co., Ltd. (72) Inventor Kenji Yonemochi Mitsubuchi, Komaki City, Aichi Nishinomon 878 Dainippon Paint Co., Ltd.

Claims (14)

[Claims] 1. A mold having a fixed mold part and a movable mold part, which is used in an in-mold coating molding method, comprising: a main cavity formed by the fixed mold part and the movable mold part; An auxiliary cavity communicating with the main cavity is provided, and in the central region of the auxiliary cavity, the boundary between the resin injected into the main cavity and the mold surface of the main cavity, or the resin injected into the main cavity and the main cavity. Is provided with a coating material injection portion for injecting the coating material into the space formed between the mold surface of the auxiliary cavity, and the auxiliary material extending from the central region of the auxiliary cavity to the communicating portion between the auxiliary cavity and the main cavity. A mold characterized in that the cavity thickness of the cavity is thicker than the cavity thickness of the end region of the auxiliary cavity. 2. The mold surface of the auxiliary cavity on the side where the coating material is injected, the cavity thickness extending from the central region of the auxiliary cavity to the communicating portion between the auxiliary cavity and the main cavity, and the end of the auxiliary cavity. The mold according to claim 1, wherein there is no step due to a difference in cavity thickness between the partial regions. 3. The cavity thickness in the end region of the auxiliary cavity is 1.5 mm or less, and the cavity thickness in the central region of the auxiliary cavity is 2.0 mm or more. The mold described in 2. 4. The mold according to claim 3, wherein the cavity thickness of the central region of the auxiliary cavity is 3.0 mm or more. 5. A groove for preventing the outflow of the coating material is provided on the mold surface on the side where the coating material is injected in the end region of the auxiliary cavity.
The mold according to any one of 1. 6. The mold according to claim 5, wherein the groove has a width of 3 mm or less and a depth of 0.2 mm or more. 7. A main cavity formed by a fixed mold part and a movable mold part, and an auxiliary cavity communicating with the main cavity, and a resin injected into the main cavity in a central region of the auxiliary cavity. A coating material injection part for injecting the coating material is provided at the boundary between the mold cavity surface of the main cavity and the cavity, and the cavity of the auxiliary cavity extending from the central region of the auxiliary cavity to the communication part between the auxiliary cavity and the main cavity. An injection molding method using a mold whose thickness is thicker than the cavity thickness of the end region of the auxiliary cavity, in which a molten resin made of a thermoplastic resin is injected into the main cavity and then injected into the main cavity. With the in-mold pressure generated by the molded resin being higher than 0 kg / cm ² -G,
An injection molding method comprising injecting a coating material into the boundary from a coating material injection part. 8. A main cavity formed by a fixed mold part and a movable mold part, and an auxiliary cavity communicating with the main cavity, wherein a film material injecting part is provided in a central region of the auxiliary cavity. This is an injection molding method using a mold in which the cavity thickness of the auxiliary cavity extending from the central region of the cavity to the communicating portion between the auxiliary cavity and the main cavity is thicker than the cavity thickness of the end region of the auxiliary cavity. And (b) a step of injecting a molten resin made of a thermoplastic resin into the main cavity while holding the mold with a predetermined mold clamping force, and (b) a step of holding pressure for a predetermined period. (C) By reducing the mold clamping force of the mold, the connection between the resin in the main cavity and the mold surface of the main cavity, and between the resin in the auxiliary cavity and the central region of the auxiliary cavity is performed. Part forms a space between the mold surface of the auxiliary cavity over the then injection molding method characterized by comprising a coating material step of injecting from the coating material injection portion in such space. 9. The injection molding method according to claim 8, wherein the thermoplastic resin is composed of a non-reinforced amorphous resin or an amorphous alloy resin. 10. The mold surface of the auxiliary cavity on the side into which the coating material is injected in the mold, the cavity thickness extending from the central region of the auxiliary cavity to the communicating portion between the auxiliary cavity and the main cavity, The injection molding method according to any one of claims 7 to 9, wherein there is no step due to a difference in cavity thickness in the end region of the auxiliary cavity. 11. The mold according to claim 1, wherein a cavity thickness of an end region of the auxiliary cavity is 1.5 mm or less, and a cavity thickness of a central region of the auxiliary cavity is 2.0 mm or more. The injection molding method according to any one of claims 7 to 10. 12. The injection molding method according to claim 11, wherein in the mold, the cavity thickness in the central region of the auxiliary cavity is 3.0 mm or more. 13. The mold according to claim 7, wherein a groove for preventing the outflow of the coating material is provided on the surface of the die on the side where the coating material is injected in the end region of the auxiliary cavity. The injection molding method according to claim 12. 14. In the mold, the width of the groove is 3 mm.
It is below and the depth is 0.2 mm or more, The injection molding method of Claim 13 characterized by the above-mentioned.