JP2844942B2 - Method for manufacturing resin hollow molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin molded article having a resin portion including a hollow portion and a skin.

[0002]

2. Description of the Related Art As a method for producing a resin molded product having a hollow portion, there is known a method described in Japanese Patent Publication No. 61-59899 and Japanese Patent Application Laid-Open No. 2-102221 disclosed by the present applicant. I have. In these methods, a hollow portion is formed by injecting a pressurized gas into a molten resin in a resin molded portion sealed in a mold.

[0003]

However, when the above-mentioned conventional method is applied to a resin molded product having a skin and an attempt is made to form a hollow portion in the molten resin in contact with the skin, the molten resin is insulated by the skin. As a result, the efficiency of cooling from the mold surface decreases. As a result, there has been a problem that it becomes difficult to cool particularly the periphery of the hollow portion of the molten resin in contact with the skin, and it takes a considerable time until the whole molded article is cooled to a predetermined temperature or lower.

The present invention has been made to solve the above-mentioned problems in the prior art, and is a hollow resin capable of efficiently and quickly cooling a molded article having a resin portion including a hollow portion and a skin. An object of the present invention is to provide a method for manufacturing a molded article.

[0005]

In order to solve the above-mentioned problems, a method for manufacturing a resin molded product according to the present invention comprises (1) a step of arranging a skin on a predetermined mold surface of a mold; Disposing a molten resin material in a mold; and (3) forming a hollow portion in the resin material by injecting a gas into the resin material disposed in the mold,
(4) a step of injecting a coolant into the hollow portion to cool the resin material, and (5) a step of releasing the resin material integrated with the skin from a mold.

[0006]

[Function] A skin and a molten resin material are arranged in a mold, a hollow portion is formed in the resin material, and then a coolant is injected into the hollow portion. However, the inner surface of the hollow part is cooled by a coolant. Therefore, cooling can be performed faster than when cooling only from the mold surface via the skin.

[0007]

FIG. 1 is a conceptual diagram showing the configuration of a resin molding apparatus for producing a hollow resin molded product by applying one embodiment of the present invention. This resin molding device is a stamping molding device 10.
0, a resin supply device 200, and a fluid supply device 300. The stamping molding apparatus 100 has an upper mold 110 and a lower mold 120. In this embodiment, in order to mold a product having an undercut, the upper mold 110 is provided with slide dies 111 and 112 at positions corresponding to the undercut portion of the molded product. Also,
The lower mold 120 has a resin injection hole 121 and a fluid injection hole 1.
22, and a fluid discharge hole 123 are formed. The fluid supply device 300 has a pressurized gas supply unit 310 and a coolant supply unit 320, and these two systems are switched by the switching valve EV1 and connected to the fluid injection hole 122.

In order to manufacture a hollow resin molded product, first, a preformed skin sheet is stamped with a stamping molding apparatus 100.
Into the cavity. Then, after filling the cavity of the mold with the thermoplastic resin, a pressurized gas is injected into the molten resin to form a hollow portion. 2 to 4 are cross-sectional views showing steps until a hollow portion is formed in the resin molded product.

FIG. 2 shows a state in which the preformed skin sheet 10 is fitted into the concave mold surface of the upper mold 110. The skin sheet 10 is a sheet in which a non-foamable skin 12 is laminated on the surface of a foam sheet 11. As the material of the foam sheet 11, a thermoplastic resin such as polypropylene or polyvinyl chloride, urethane, or the like is used. As the material of the skin 12, a thermoplastic resin such as polypropylene or polyvinyl chloride is used. Such a skin sheet 10 is shaped in advance by a forming method such as vacuum forming so as to match the mold surface of the upper mold 110.
During the molding, a grain pattern is transferred to the surface of the skin 12.

When the worker inserts the shaped skin sheet 10 from below the upper mold 110, as shown in FIG.
The skin sheet 10 is held by the upper mold 110.
In this step, the upper mold 110 is retracted above the lower mold 120. As shown in the figure, the molded article manufactured in this embodiment has two undercut portions U1 and U2, and a hollow portion is formed in these undercut portions U1 and U2 as described later. Is done.

After the skin sheet 10 is inserted into the upper mold 110, the upper mold 110 is lowered, and a part of the mold surface of the upper mold 110 is removed from the mold surface of the lower mold 120 as shown in FIG. A cavity 130 is formed in contact with the part. However, at this point, the upper mold 110 and the lower mold 120 are not completely clamped, but are held with a slight distance therebetween. The resin material 20 melted from the resin supply device 200 through the resin injection hole 121 of the lower mold 120 is filled with the cavity 1.
Inject into 30. As the resin material 20, a thermoplastic resin such as polyvinyl chloride or polypropylene is used.

After injecting a predetermined amount of resin material 20, FIG.
As shown in (1), the upper mold 110 is further lowered to press (stamp) the resin material 20 in the cavity 130. Since the resin flows into the large undercut portion U2 when the hollow portion is formed in the next step, the resin has not completely flowed in the step of FIG.

Next, the pressurized gas 3 is supplied from the fluid supply device 300.
0 is supplied, and the pressurized gas 30 is injected into the molten resin material 20 through the fluid injection hole 122 of the lower mold 120 as shown in FIG. The injection of the pressurized gas 30 is performed by the pressurized gas supply unit 310 shown in FIG. First, the switching valve EV1 and the solenoid valve EV2 of the pressurized gas supply unit 310 are closed, and a gas such as nitrogen or air is supplied from the gas cylinder GC1 to the pressure reducing valve RV1 and the check valve CV.
1 to the piston type accumulator AC1. The gas pressure at this time is preferably about 5 to 8 atm. Then, the solenoid valve EV2 communicating with the hydraulic pressure source OS is opened, the gas in the piston type accumulator AC1 is compressed at a pressure of about 140 atm, and the solenoid valve EV2 is closed. Next, the solenoid valve EV1 at the outlet of the pressurized gas supply unit 310 is opened, and the gas in the piston type accumulator AC1 is pressed into the cavity of the mold via the fluid injection hole 122.

When the pressurized gas is injected into the resin material in this manner, as shown in FIG. 5, the pressurized gas 30 is supplied to the hollow portion V in the undercut portions U1 and U2 where the thickness of the resin material is large.
The resin material 20 is expanded while forming 1, V2. The pressurized gas 30 injected into the hollow portions V1 and V2 presses the skin sheet 10 against the upper mold 110 and presses the resin material 20 against the lower mold 120 to form a resin molded product into a desired shape. You. By providing the hollow portion in the undercut portion in this way, the thickness of the resin can be reduced, so that there is an advantage that so-called sink marks and warpage can be prevented. In addition, the lower mold 120 and the cavity 13
The shape of the nozzle for injecting a resin material or a pressurized gas into the nozzle can be, for example, the one described in JP-B-61-59899 described above.

FIG. 6 shows a resin molded article 1 thus molded.
It is a perspective view which shows a part of. This molded article 1 has a shape elongated in the Y direction, and its XZ section corresponds to the section shown in FIG. Nozzle for injecting resin, pressurized gas and coolant (hereinafter referred to as "injection nozzle")
Is provided, for example, at a portion substantially corresponding to the center in the Y direction (longitudinal direction) of the molded product.

Although not shown in FIGS. 2 to 5, the lower mold 120 has a fluid discharge hole 123 (see FIG. 1) for discharging pressurized gas in the hollow portions V1 and V2, and a gas vent. A mechanism is provided. FIG. 7 is a sectional view of the molding apparatus 100 corresponding to the AA section of the molded article in FIG. In the figure,
Lower mold 1 corresponding to back surface 41 of hollow portion V2 of molded article 1
The mold surface 20 is provided with a gas vent 141.
Although the gas vent 141 is connected to the fluid discharge hole 123, the gas vent 141 is closed by the piston 131 as shown in FIG.

The injection of the pressurized gas 30 causes the resin material 20
When the hollow portions V1 and V2 are formed in the piston, as shown in FIG. 8, the piston 131 of the degassing mechanism is driven to move backward. When the piston 131 retreats, the resin is broken by the gas pressure of the pressurized gas 30 in the hollow portion, and the pressurized gas 30 is discharged to the outside through the gas vent 141 and the fluid discharge hole 123. Next, a coolant is injected into the hollow portions V1 and V2 from the coolant supply unit 320 (FIG. 1).

The injection of the coolant by the coolant supply unit 320 is performed as follows. First, the solenoid valves EV1 and EV
With the valve 3 closed, the coolant is supplied from the coolant tank CT to the hydraulic cylinder AC2 via the pressure reducing valve RV2 and the check valve CV2. Then, the electromagnetic valves EV1 and EV3 are opened, and the hydraulic cylinder AC2 is driven by the hydraulic pressure source OS to inject the coolant 40 into the hollow portions V1 and V2. The coolant 40 is injected by an amount experimentally determined in advance so as to sufficiently fill the hollow portions V1 and V2.

In the process shown in FIG.
The resin is injected into the mold at 0 ° C. to 220 ° C., and when the coolant is injected, the resin material in the hollow portions V1 and V2 is 170 ° C. to 180 °
It is about ℃. Then, the resin material 20 is cooled by the coolant 40, and when the temperature becomes 100 ° C. or less, the cooling is completed. When cooling is completed, the switching valve EV
1 is switched to the coolant supply section 320 side, and the pressurized gas 30 is injected into the fluid injection hole 122 and the hollow portions V1 and V2, so that the coolant 40 existing in the fluid injection hole 122 and the hollow portions V1 and V2 is changed. Collected in the coolant tank CT. After this,
Slide the slide molds 111 and 112 to move the upper mold 1
By raising 10, resin molded article 1 can be taken out.

As described above, if the coolant is injected into the hollow portions V1 and V2 of the resin, the cooling is completed in, for example, several tens of seconds. On the other hand, when the coolant is not injected into the hollow portions V1 and V2, it takes about 10 minutes or more for cooling. Therefore, it can be seen that the embodiment has a great effect on shortening the cooling time.

As a coolant, an alcoholic solvent such as ethylene glycol, water, nitrogen gas or the like can be used. However, since the heat capacity of a liquid is larger than that of a gas, the cooling effect is large. However, a coolant that does not react with the resin material 20 is desirable. Moreover, you may make it cool a coolant below room temperature as needed. Cooling the coolant below room temperature has the advantage that the cooling time can be further reduced. Further, the cooling time can be reduced even if the coolant 40 is continuously injected until the resin material 20 in the mold is cooled.

FIGS. 9 and 10 are sectional views showing other examples of the gas vent. FIG. 9 is a cross-sectional view of the molding apparatus 100 corresponding to the BB cross section of the molded product 1 in FIG. In the figure, a hollow portion V is provided at the end of the molded product 1 in the Y direction (longitudinal direction).
The portion including 1 protrudes. Projection 1b of this molded product
The mold surface of the upper mold 110 in contact with the
Is provided. Thus, it is preferable to provide the gas vent at the end of the molded product. Although the gas vent 142 is connected to the fluid discharge hole 123a, in the steps of FIGS.
As shown in FIG. 9, the gas vent 142 is closed by the piston 132.

FIG. 10 shows a state in which the piston 132 is retracted, the resin material 20 in the protrusion 1b is broken, and the pressurized gas 30 flows into the fluid discharge hole 123a from the hollow portion V2, as in FIG. 9 and 10, the fluid discharge holes 123a are provided in the upper mold 110, but may be provided in the lower mold 120.

FIG. 11 and FIG. 12 are plan views of the resin molded product 1. The position of the gas vent and the injection nozzle of the coolant (in this embodiment, the same as the nozzle for injecting the resin material or the pressurized gas) It is an explanatory view showing the relationship with the position of ().
In FIG. 11, the injection nozzle 121a (shown by a black circle in the figure).
Are located at the center in the longitudinal direction of the resin molded product 1, and gas vents 142 (shown by white circles in the figure) are provided at positions of the protruding portions 1 b at both ends of the resin molded product 1. FIG.
In this example, injection nozzles 121a are provided at quarters from both ends of the resin molded product 1, respectively.
41 is provided at the center of the back surface of the resin molded product 1.
In the case of FIG. 12, gas vents may be further provided at both ends of the resin molded product 1.

As described above, if the gas vent is provided at at least one position farthest from the position of the coolant injection nozzle in the longitudinal direction of the hollow portion of the resin molded product, the gas is injected from the injection nozzle. Since the coolant proceeds toward the gas vent while filling the hollow portion, there is an advantage that the hollow portion can be cooled well.

The present invention is not limited to the above embodiment, but can be implemented in various modes without departing from the gist of the present invention. For example, the following modifications are possible. (1) In the above embodiment, the resin material is injected into the mold. However, as illustrated in FIG. 1 of Japanese Patent Publication No. 61-59899, the molten resin material is injected into the mold. Injection may be performed, or a molten resin material may be charged onto a mold as illustrated in FIG. 1 of JP-A-2-102221. As described above, generally, the molten resin material may be arranged in the mold.

(2) In the above embodiment, the skin sheet 10 has the skin 12 and the foam sheet 11, but the skin sheet does not need to have the foam sheet, and may be any sheet having at least the skin portion. . However, when a skin sheet having a foam sheet is used, the effect of shortening the cooling time according to the present invention becomes more remarkable because the heat insulation effect of the skin sheet is large.

[0028]

As described above, in the method for manufacturing a resin hollow molded article according to the present invention, a skin and a molten resin material are arranged in a mold, and a hollow portion is formed in the resin material. Since the coolant is injected, the resin material is insulated by the skin and is difficult to be cooled, but the inner surface of the hollow portion is cooled by the coolant. Therefore, there is an effect that cooling can be performed faster than when cooling is performed only from the mold surface via the skin.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of a molding apparatus to which an embodiment of the present invention is applied.

FIG. 2 is a process cross-sectional view showing steps of resin injection and stamping in the example.

FIG. 3 is a process cross-sectional view showing steps of resin injection and stamping in the example.

FIG. 4 is a process cross-sectional view showing steps of resin injection and stamping in the example.

FIG. 5 is a process cross-sectional view showing steps of resin injection and stamping in the example.

FIG. 6 is a perspective view showing a molded product manufactured in the example.

FIG. 7 is a sectional view of a mold showing a state of a gas vent before a coolant is injected.

FIG. 8 is a sectional view of a mold showing a state of a gas vent at the time of injection of a coolant.

FIG. 9 is a cross-sectional view of a mold showing a state of another gas vent before injection of a coolant.

FIG. 10 is a cross-sectional view of a mold showing another state of a gas vent during injection of a coolant.

FIG. 11 is an explanatory diagram showing a positional relationship between a coolant injection nozzle and a gas vent.

FIG. 12 is an explanatory diagram showing a positional relationship between a coolant injection nozzle and a gas vent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 10 Skin sheet 11 Skin 12 Foam sheet 20 Resin material 30 Pressurized gas 40 Coolant 100 Molding device 110 Upper mold 111, 112 Slide mold 120 Lower mold 121 Resin injection hole 122 Fluid injection hole 123 Fluid discharge hole 131 , 132 piston 141, 142 gas vent 200 resin supply device 300 fluid supply device 310 pressurized gas supply unit 320 coolant supply unit

Continuation of the front page (72) Inventor Hikaru Ando 1 Ogataai Nagahata, Kasuga-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. (56) References Table 3-3-1588 (JP, A) (58) (Int.Cl. ⁶ , DB name) B29C 45/00-45/84 B29C 49/00-49/80

Claims (1)

(57) [Claims] 1. A method for manufacturing a resin molded article having a resin portion including a hollow portion and a skin, comprising: (1) a step of arranging a skin on a predetermined mold surface of a mold; Disposing a molten resin material in a mold; and (3) injecting a gas into the resin material disposed in the mold,
A step of forming a hollow portion in the resin material; (4) a step of injecting a coolant into the hollow portion to cool the resin material; and (5) a mold for molding the resin material integrated with the skin. And a step of releasing from the mold.