JP7713310B2 - Mold device for sandwich molded body and method for manufacturing sandwich molded body - Google Patents

Description

The present invention relates to a mold apparatus for a sandwich molded body used for molding a sandwich molded body for forming, for example, an outer panel of an automobile, and to a method for producing a sandwich molded body using the mold apparatus for a sandwich molded body.

In recent years, plastic exterior panels have been used to replace conventional metal exterior panels for automobile exterior panels such as bumpers and fenders in order to reduce weight. As a component for forming such plastic exterior panels, a sandwich molded body is known in which the intermediate core layer and the skin layers sandwiching the core layer from the front and back are made of different materials (see, for example, Patent Document 1). In the above-mentioned sandwich molded body, there is known an example in which the skin layer is made of polypropylene resin, which has excellent appearance, and the core layer is made of a composite material of polypropylene, which has excellent mechanical properties, and glass fiber or carbon fiber.

JP 2001-353749 A

However, when complex shapes such as sliding doors are sandwich molded, various problems arise. For example, when the above-mentioned sandwich molded body is injection molded, the skin material that forms the skin layer may accumulate in the four corners and center of the sliding door, forming a skin material pool 104, as shown in Figure 10. In this case, problems such as warping of the panel that constitutes the sliding door, deterioration of molding dimensional accuracy, and deformation of the panel during in-line painting due to insufficient filling of the core material and inability to ensure heat resistance may occur.

In addition, core material overflow 106 may occur, forming core material in the weld area. In this case, problems such as fibers protruding from the exterior panel can occur, causing surface roughness to increase and deteriorating the quality of the exterior panel.

An object of the present invention is to provide a mold apparatus for sandwich molded bodies, which molds sandwich molded bodies that are precisely molded and have ensured heat resistance, and a method for producing sandwich molded bodies using the mold apparatus for sandwich molded bodies.

The mold device for a sandwich molded body of the present invention is
A mold device for a sandwich molded body having a mold for injection molding a sandwich molded body made of different resin materials for a core layer located in the middle and skin layers sandwiching the core layer from the front and back,
The mold is
A cavity in which the sandwich molded body is formed;
a primary gate for supplying a skin material constituting the skin layer to the cavity;
a secondary gate for supplying a core material constituting the core layer to the cavity;
an overflow portion through which excess skin material and core material are discharged during injection molding;
The overflow portion is a space formed along an edge of the hollow portion.

In this way, by forming an overflow section along the edge of the cavity, the mold can be opened at a specific time, the resin material can be discharged into the overflow section, and the core material can be distributed to the end of the cavity, increasing the filling rate of the core material. This prevents the panel from warping, which could lead to a deterioration in molding dimensional accuracy, or the panel from deforming due to insufficient core material filling, which could result in insufficient core material filling and therefore insufficient heat resistance. This makes it possible to mold a sandwich molded body that is precisely molded and has sufficient heat resistance.

In addition, the mold device for a sandwich molded body of the present invention is
The mold is characterized in that a blocking portion is formed between the cavity portion and the overflow portion, which blocks the cavity portion from the overflow portion when the mold is in a closed state.
By providing the blocking portion in this manner, it is possible to clearly distinguish the main body and the excess portion for the sandwich molded body after the sandwich molded body is completed.

In addition, the mold device for a sandwich molded body of the present invention is
The overflow portion includes an outer overflow portion that surrounds most of the outer periphery of the hollow portion, and an inner overflow portion that is surrounded by the inner periphery of the hollow portion.

In this way, by surrounding most of the outer periphery of the cavity with an outer overflow section, the core material can be distributed all around the cavity. Also, by forming an inner overflow section on the inner periphery of the cavity, it is possible to mold with precision even when the panel has openings such as windows.

In addition, the mold device for a sandwich molded body of the present invention is
An opening/closing control unit that opens and closes the mold,
The opening/closing control section is characterized in that it is any one of a hydraulic cylinder, an air cylinder, and an electric control section.
In this way, a plurality of types of devices can be applied to the opening/closing control section.

In addition, the mold device for a sandwich molded body of the present invention is
The sandwich molded article after demolding is a panel used as an outer panel of an automobile.
That is, the mold apparatus for forming a sandwich molded body of the present invention is suitably used for molding outer panels of automobiles.

Further, the method for molding a sandwich molded body of the present invention includes the steps of:
A method for molding a sandwich molded body using the above-mentioned mold device for a sandwich molded body,
A first opening step of opening the mold;
a closing step of closing the mold after the first opening step;
a second opening step of opening the mold again after the closing step;
a cooling step of cooling the mold after the second opening step,
The first opening step, the closing step, and the second opening step are performed during the injection of the resin material, and the cooling step is performed after the injection of the resin material.
In this manner, by repeatedly opening and closing the mold while the resin material is being injected, the resin material can be accurately discharged into the overflow portion, and the core material can be reliably distributed to the end of the cavity portion.

Further, the method for molding a sandwich molded body of the present invention includes the steps of:
The first opening step and the second opening step are both performed while the core material is being injected into the cavity.
In this way, by opening the mold while the core material is being injected, it is possible to more reliably ensure that the core material reaches the ends of the cavity.

Further, the method for molding a sandwich molded body of the present invention includes the steps of:
The core material injected during a period overlapping with the first opening step is injected from the first secondary gate, and the core material injected during a period overlapping with the second opening step is injected from the second secondary gate.
In this way, by opening the mold each time the core material is injected from each secondary gate, it is possible to more reliably ensure that the core material reaches the ends of the cavity.

Further, the method for molding a sandwich molded body of the present invention includes the steps of:
The first opening step is performed in an overlapping manner with a pressurizing step of applying a holding pressure to the mold.
This allows the fibers contained in the core material to be dispersed more uniformly, making it possible to suppress deformation of the resulting sandwich molded body.

According to the present invention, it is possible to provide a mold device for a sandwich molded body, which molds a sandwich molded body that is precisely molded and has ensured heat resistance, and a method for manufacturing a sandwich molded body using the mold device for a sandwich molded body.

1 is a schematic diagram showing a cavity of a mold device for a sandwich molded body according to an embodiment, viewed from the front, and a cross-sectional view of a portion thereof. 1 is a schematic diagram of a mold device for a sandwich molded body according to an embodiment, viewed from the side. FIG. 11 is a table showing the injection time of a resin material and the opening time of a cavity according to an embodiment. 13A to 13C are diagrams showing a state in which the mold is opened during the process of filling a cavity in the mold with resin material in the embodiment. 11 is a diagram showing a state in which a cavity of a mold in the embodiment is filled with a resin material. FIG. FIG. 6 is an enlarged view of the circled area in FIG. 5 . FIG. 1 is a diagram showing a state in which a cavity in a conventional mold is filled with a resin material. FIG. 8 is an enlarged view of the circled area in FIG. 7 . 1A and 1B are diagrams showing a sandwich molded body produced by a mold according to an embodiment. FIG. 1 is a diagram showing a process for injection molding a sandwich molded body according to a conventional technique.

The following describes an embodiment of the present invention with reference to the drawings. Fig. 1(a) is a schematic diagram of the cavity 20 of a mold device for sandwich molded bodies (hereinafter abbreviated as mold device) according to an embodiment, viewed from the front, and Fig. 1(b) is the mold 4 portion of the A-A cross section shown in Fig. 1(a). Also, Fig. 2 is a schematic diagram of the mold device 2 shown in Fig. 1(a) viewed from the side.

The mold device 2 is a device used to mold a sandwich molded body 30 (see FIG. 9) in which a core layer located in the middle and skin layers sandwiching the core layer from the front and back are made of different resin materials. As shown in FIGS. 1 and 2, the mold device 2 is equipped with a flat rectangular mold 4, a first resin unit (not shown) that supplies the mold 4 with a skin material 32 (see FIG. 4), which is the first resin material that constitutes the skin layer, a second resin unit (not shown) that supplies the mold 4 with a core material 34 (see FIG. 4), which is the second resin material that constitutes the core layer, a first nozzle 8 that is a flow path for the skin material 32, a second nozzle 10 that is a flow path for the core material 34, a hydraulic cylinder (not shown) that is an opening/closing control unit that opens and closes the mold 4, and a control sensor 12 (see FIG. 5) that controls the degree to which the mold 4 is opened.

At the tip of the first nozzle 8, primary gates 8a and 8b are provided, which serve as supply ports for the skin material 32, and at the tip of the second nozzle 10, secondary gates 10a and 10b are provided, which serve as supply ports for the core material 34.

As shown in FIG. 1(b), the mold 4 includes a fixed mold 4a and a movable mold 4b. The mold 4 also includes a cavity 20 in which the sandwich molded body 30 is formed, a film gate 22 which is an inlet for introducing resin material into the cavity 20, and an overflow section 24 for discharging excess resin material (skin material 32, core material 34) from the cavity 20 during injection molding.

Here, the cavity 20 is supplied at both ends with skin material 32 by primary gates 8a, 8b, and with core material 34 by secondary gates 10a, 10b.
In addition, the overflow portion 24 is formed along the edge of the hollow portion 20, and includes an outer overflow portion 24a that surrounds most of the outer periphery of the hollow portion 20 (the portion other than the film gate 22), and an inner overflow portion 24b that surrounds the outer periphery of the window portion 23 formed within the hollow portion 20 (that is surrounded by the inner periphery of the hollow portion 20 at the window portion 23).

In addition, between the overflow portion 24 and the cavity portion 20, a blocking portion 18 is formed to block the overflow portion 24 and the cavity portion 20 when the mold 4 is closed. Specifically, between the outer overflow portion 24a and the cavity portion 20, a first blocking portion 18a protruding from the fixed mold 4a is formed on the outer overflow portion 24a side, and a second blocking portion 18b protruding from the movable mold 4b is formed on the cavity portion 20 side. Similarly, between the inner overflow portion 24b and the cavity portion 20, a first blocking portion 18a protruding from the fixed mold 4a is formed on the inner overflow portion 24b side, and a second blocking portion 18b protruding from the movable mold 4b is formed on the cavity portion 20 side.

Next, a molding method of the sandwich molded body 30 (see FIG. 9) using the mold device 2 will be described with reference to the table shown in FIG. 3, taking as an example the case of manufacturing a panel constituting a sliding door among the outer panels of an automobile. First, as shown in FIG. 1(b), the movable mold 4b, which is movable, is moved toward the fixed mold 4a to close the mold 4. Next, the primary gate 8a of the mold 4 is opened by a gate opening/closing unit (not shown), and the skin material 32, which will be the surface layer of the sandwich molded body 30, is injected into the first nozzle 8 by the first resin unit. As shown in FIG. 4(a), the skin material 32 is supplied from the primary gate 8a to the cavity 20. Here, as shown in FIG. 3, the time when the skin material 32 is first injected at the start of molding is set as the reference time, and the skin material 32 continues to be injected from the primary gate 8a for 3 seconds from the reference time.

Next, two seconds after the reference time, the secondary gate 10a of the mold 4 is opened by the gate opening/closing unit, and the second resin unit injects the core material 34, which will be the intermediate layer of the sandwich molded body 30, into the second nozzle 10, and the core material 34 is supplied from the secondary gate 10a to the cavity 20. The core material 34 also continues to be injected from the secondary gate 10a for three seconds from the reference time.

Here, the supply of the core material 34 from the secondary gate 10a is performed with a holding pressure applied to the mold 4 by an injection cylinder (not shown). That is, the application of the holding pressure starts 2 seconds after the reference time and continues for 3 seconds. This pressure increases the uniformity of the distribution of the fibers contained in the core material 34.

As a result, as shown in FIG. 4(a), the skin material 32 and the core material 34 are filled into the portion that constitutes the upper portion of the sliding door (the side where the window portion 23 is located).
Three seconds after the reference time, the injection of the skin material 32 by the first resin unit is stopped, and the primary gate 8a is closed by the gate opening/closing unit. As shown in Fig. 4(b), the movable mold 4b is moved by a hydraulic cylinder (not shown) to open the mold 4 (first opening step). This causes the cavity 20 to expand, and the excess skin material 32 and core material 34 are discharged into the overflow unit 24.

When the mold 4 is open, the distance T between the fixed mold 4a and the movable mold 4b is preferably 0.3 mm or more and 1.0 mm or less, and more preferably 0.4 mm or more and 0.7 mm or less.

The mold 4 is kept open for 2.5 seconds, and 4.5 seconds after the reference time, the hydraulic cylinder moves the movable mold 4b toward the fixed mold 4a, and the mold 4 is closed (closing process), as shown in Figure 3(c).

Five seconds after the reference time, application of the holding pressure is stopped, injection of the core material 34 by the second resin unit is stopped, and the secondary gate 10a is closed by the gate opening/closing unit. At the same time, the primary gate 8b is opened and the skin material 32 is supplied to the cavity 20, and the skin material 32 continues to be injected for three seconds. Eight seconds after the reference time, injection of the skin material 32 by the first resin unit is stopped, and the primary gate 8b is closed by the gate opening/closing unit.

At the same time, the secondary gate 10b is opened and the core material 34 is supplied to the cavity 20, where it continues to be injected for 3 seconds. During this time, 9 seconds after the reference time, the mold 4 is opened again (second opening step) as shown in FIG. 3(b), and the excess skin material 32 and core material 34 are discharged into the overflow section 24. The mold 4 is kept open for 2.5 seconds, and 10.5 seconds after the reference time, the mold 4 is closed again as shown in FIG. 3(c).

Here, Fig. 5 is a diagram showing a cross section seen from above of the mold device 2 when the core material 34 is being supplied, and Fig. 6 is an enlarged view of the circled portion shown in Fig. 5 after the supply of the core material 34 has been completed. As described above, by opening the mold 4 during the injection molding of the core material 34 and temporarily expanding the space of the cavity 20, as shown in Figs. 5 and 6, the core material 34 can be spread to the end of the cavity 20, and the filling rate of the core material 34 can be increased.

Note that Fig. 7 is a cross-sectional view of the mold device 2 viewed from above when resin material is supplied to the cavity 20 without opening the mold 4 as in the conventional case, and Fig. 8 is an enlarged view of the circle shown in Fig. 7. In this case, as shown in Figs. 7 and 8, the core material 34 cannot reach the end of the cavity 20.

11 seconds after the reference time, the injection of the core material 34 by the second resin unit is stopped, and the secondary gate 10b is closed by the gate opening/closing unit. At the same time, a cooling device (not shown) is operated to cool the mold 4 for 20 seconds (cooling process). The cooling time is preferably 10 seconds or more and 30 seconds or less.

When the skin material 32 and core material 34 in the cavity 20 are cooled and hardened, the two are integrated to form a sandwich molded body 30, and when the movable mold 4b is moved to open the mold 4, the sandwich molded body 30 is released as a panel.

According to the invention of this embodiment, by forming an overflow portion 24 along the edge of the cavity portion 20 and opening the mold 4 at a specific timing, the resin material is discharged into the overflow portion 24, and the core material 34 is spread to the end of the cavity portion 20, thereby increasing the filling rate of the core material 34. This prevents the panel from warping, which deteriorates the molding dimensional accuracy, and the panel from being deformed due to insufficient filling of the core material 34, which makes it difficult to ensure heat resistance. In addition, since the core material 34 is less likely to overflow into the weld portion (see Figure 10), it is possible to prevent deterioration of the quality of the panel, such as fibers protruding from the panel and causing surface roughness. Therefore, it is possible to mold a sandwich molded body 30 that is precisely molded and has ensured heat resistance.

In addition, by surrounding most of the outer periphery of the hollow portion 20 with the outer overflow portion 24a, the core material 34 can be distributed all around the hollow portion 20. In addition, by forming the inner overflow portion 24b on the inner periphery of the hollow portion 20, it is possible to mold with high precision even if the panel has an opening such as a window portion 23.

In addition, by repeatedly opening and closing the mold 4 during the injection molding of the resin material, the resin material can be accurately discharged into the overflow section 24, and the core material 34 can be reliably distributed to the end of the cavity section 20.

Furthermore, by opening the mold 4 while the core material 34 is being injected, the core material 34 can be more reliably distributed to the ends of the cavity 20 .
Furthermore, by opening the mold 4 each time the core material 34 is injected from each of the secondary gates 10a, 10b, the core material 34 can be more reliably distributed to the ends of the cavity 20.

In addition, by performing the first release process in conjunction with the pressurization process, the fibers contained in the core material 34 are more uniformly dispersed, and deformation of the resulting sandwich molded body 30 can be suppressed.

In the above embodiment, the opening/closing control unit is a hydraulic cylinder, but instead of a hydraulic cylinder, an air cylinder or an electric control unit may be used as the opening/closing control unit.

In addition, in the above-described embodiment, the table shown in FIG. 3 is an example, and the injection time of the resin material and the opening time of the overflow section 24 do not have to be exactly as shown, and various modifications are possible without departing from the scope of the present invention.

In addition, in the above embodiment, the sandwich molded body 30 is exemplified as an automobile exterior panel having a window portion 23, but the present invention can also be applied when manufacturing a sandwich molded body 30 that does not have a window portion 23.

In the above-described embodiment, the skin material 32 contains a propylene-based resin.
Examples of the propylene-based resin include a propylene homopolymer and a copolymer of propylene and at least one selected from ethylene and an α-olefin having 4 or more carbon atoms. The copolymer may be a propylene-based random copolymer or a propylene-based block copolymer.

Examples of α-olefins having 4 or more carbon atoms include 1-butene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, and ethyl-1-pentene. Examples of α-olefins having 4 to 20 carbon atoms include 1-butene, trimethyl-1-butene, methylethyl-1-butene, 1-octene, methyl-1-pentene, ethyl-1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene. Among these, 1-butene, 1-pentene, 1-hexene, and 1-octene are preferred.

Propylene-based resins are preferably propylene homopolymers and propylene block copolymers. Propylene block copolymers are also called impact polypropylenes and are usually mixtures of polypropylene homopolymers and propylene-ethylene copolymers.

The propylene-based resin may contain a propylene-based resin modified with an unsaturated carboxylic acid or a derivative thereof, such as maleic anhydride, fumaric acid, or (meth)acrylic acid. In such modified propylene-based resins, the content of the unsaturated carboxylic acid or a derivative thereof is preferably 0.01 to 10% by mass.

The core material 34 contains a fiber-reinforced propylene-based resin. The fiber-reinforced propylene-based resin imparts excellent heat resistance and mechanical strength to the molded article of the present embodiment.
Examples of the propylene-based resin in the fiber-reinforced propylene-based resin include the propylene-based resins described in the description of the skin material 32. However, the propylene-based resin contained in the fiber-reinforced propylene-based resin and the propylene-based resin contained in the skin material 32 may be the same resin or different resins. In addition, a part or all of the propylene-based resin may be recycled material.

Examples of the fibers in the fiber-reinforced propylene-based resin include glass fibers; carbon fibers; metal fibers such as aluminum fibers, aluminum alloy fibers, copper fibers, brass fibers, steel fibers, stainless steel fibers, and titanium fibers; natural fibers such as cotton fibers, silk fibers, wood fibers, and cellulose fibers; ceramic fibers such as silicon carbide fibers, silicon nitride fibers, alumina fibers, and zirconia fibers; and synthetic fibers made of synthetic resins such as fully aromatic polyamide (aramid), fully aromatic polyester, fully aromatic polyesteramide, fully aromatic polyether, fully aromatic polycarbonate, fully aromatic polyazomethine, polyphenylene sulfide, polyparaphenylene benzobisoxazole, poly(para-phenylene benzobisthiazole), polybenzimidazole, polyether ether ketone, polyamide imide, polyimide, polytetrafluoroethylene, polyvinyl alcohol, polyolefin, polyarylate, and fluorine-based polymers. Examples of the glass fibers include filament-like fibers obtained by melt spinning glass such as E glass, C glass, S glass, and alkali-resistant glass. Among the fibers, glass fibers and carbon fibers are preferred from the standpoint of rigidity and heat resistance.

If necessary, the fibers may be subjected to a surface treatment such as a coupling agent treatment, a surfactant treatment, an ultraviolet irradiation treatment, an electron beam irradiation treatment, or a plasma irradiation treatment. Examples of coupling agents include amino group-containing alkoxysilanes such as γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane, as well as hydrolysates thereof.

The fibers may be short or long, but long fibers are preferred because they provide superior physical properties to the resulting molded product, and short fibers are preferred from the viewpoint of fluidity during molding. A mixture of short and long fibers may also be used. The short fibers may be chopped fiber (cut fiber) short fibers or pulp-like short fibers having fibrils.

Reference Signs List 2 Mold device 4 Mold 4a Fixed mold 4b Movable mold 8 Nozzles 8a, 8b Primary gate 10 Nozzles 10a, 10b Secondary gate 12 Control sensor 18 Blocking section 18a First blocking section 18b Second blocking section 20 Cavity section 22 Film gate 23 Window section 24 Overflow section 24a Outer overflow section 24b Inner overflow section 30 Sandwich molded body 32 Skin material 34 Core material 104 Skin material reservoir 106 Core material overflow

Claims (9)

A mold device for a sandwich molded body, comprising a mold for injection molding a sandwich molded body, the sandwich molded body being made of different resin materials for a core layer located in the middle and skin layers sandwiching the core layer from the front and back, and an opening/closing control unit for controlling the opening/closing operation of the mold ,
The mold is
A cavity in which the sandwich molded body is formed;
a primary gate for supplying a skin material constituting the skin layer to the cavity;
a secondary gate for supplying a core material constituting the core layer to the cavity;
an overflow portion formed along an edge of the cavity, through which excess skin material and the core material are discharged during injection molding;
The opening/closing control unit, while the core material is being injected into the cavity,
a first opening operation for opening the mold to transition from a closed state in which the overflow portion and the cavity portion are blocked to an open state in which the overflow portion and the cavity portion are in communication with each other;
a closing operation for closing the mold and transitioning the mold from the open state to the closed state after the first opening operation;
A mold device for a sandwich molded body, characterized in that the opening and closing operations of the mold are controlled so as to perform the above. Further comprising a cooling unit for cooling the mold,
2. The mold apparatus for a sandwich molded body according to claim 1, wherein the cooling section cools the mold after the closing operation is completed and the core material is injected into the cavity. A mold apparatus for a sandwich molded body as described in claim 1 or 2, characterized in that a blocking portion is formed between the cavity portion and the overflow portion, which blocks the cavity portion from the overflow portion when the mold is closed. The mold device for a sandwich molded body according to any one of claims 1 to 3, characterized in that the overflow portion includes an outer overflow portion surrounding most of the outer periphery of the hollow portion, and an inner overflow portion surrounded by the inner periphery of the hollow portion. The mold device for a sandwich molded body according to any one of claims 1 to 4 , characterized in that the opening and closing control section is any one of a hydraulic cylinder, an air cylinder, and an electric control section. The mold apparatus for a sandwich molded body according to any one of claims 1 to 5 , characterized in that the sandwich molded body after demolding is a panel used as an outer panel of an automobile. A method for manufacturing a sandwich molded body using a mold device for a sandwich molded body having a mold for injection molding a sandwich molded body formed by using different resin materials for a core layer located in the middle and skin layers sandwiching the core layer from the front and back , comprising:
The mold is
A cavity in which the sandwich molded body is formed;
a primary gate for supplying a skin material constituting the skin layer to the cavity;
a secondary gate for supplying a core material constituting the core layer to the cavity;
an overflow portion, which is a space formed along the edge of the cavity portion and through which excess skin material and core material are discharged during injection molding;
Equipped with
a first opening step of opening the mold while the core material is being injected into the cavity, thereby transitioning from a closed state in which the overflow portion and the cavity portion are blocked to an open state in which the overflow portion and the cavity portion are in communication with each other;
a closing step of closing the mold and transitioning the mold from the open state to the closed state while the core material is being injected into the cavity portion after the first opening step;
A method for producing a sandwich molded body, comprising : The method for producing a sandwich molded body according to claim 7, further comprising a cooling step of cooling the mold after the closing step is completed and the core material is injected into the cavity. The method for manufacturing a sandwich molded body according to claim 7 or 8 , wherein the first opening step is performed in an overlapping manner with a pressurizing step of applying a holding pressure to the mold.