JPH05309724A - Molding method for resin molded piece having hollow part - Google Patents

Abstract

PURPOSE:To enable a large hollow part to be formed by enabling a wall thickness of resin around the hollow part to be uniformized in a molding method wherein the hollow part is formed inside a molded piece by injecting gas into a cavity of a molding tool with which stamping molding of thermoplastic resin is carried out. CONSTITUTION:A thermoplastic resin 22 fed on a bottom tool 16 equipped with a gas hole 30 for injecting gas is made to be of two layer construction consisting of an upper layer part and a lower layer part 38. Thereby, the gas injected when the mold is closed enters a boarder surface between the upper layer part 36 and the lower layer part 38, and expands time upper layer part 36 and the lower layer part to a state wherein the boader surface 52 is expanded. A hollow part is enabled to be formed stably lest their wall thickness should be locally thinned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a resin molded product having a hollow portion, and more particularly to a technique for forming a hollow portion by injecting a gas into a cavity of a mold for molding a thermoplastic resin. It is a thing.

[0002]

2. Description of the Related Art When a molten thermoplastic resin supplied onto a lower mold is molded between the lower mold and the upper mold, it is pressurized by a gas injection means into a cavity formed by the lower mold and the upper mold. There is known a method for molding a resin molded product in which a hollow portion is formed by the gas by injecting the gas to expand the thermoplastic resin so as to uniformly adhere to the cavity. The method described in Japanese Patent Application Laid-Open No. 2-102021 is an example.

[0003]

However, in the molding method of the type in which gas is injected into the cavity as described above, the volume of the thermoplastic resin supplied into the molding die is smaller than the volume of the cavity, and the volume of the thermoplastic resin is smaller than that of the cavity. Since there is a gap between them, even if the gas is fed into the thermoplastic resin under a certain condition, the flow deformation of the resin that is expanded by the gas is not constant from time to time. For this reason, it is difficult to properly expand the thermoplastic resin so that the gap is uniformly reduced, the position of the hollow portion is biased, and the thickness of the resin around the hollow portion becomes non-uniform, resulting in a large proportion of defective products. There was a problem. Further, since it is necessary to set the thickness of the resin to be thicker in consideration of the generation of the thin portion due to the displacement of the hollow portion, there is a limit to the size of the hollow portion that can be formed.

The present invention has been made in view of the above circumstances. An object of the present invention is to form a resin having a uniform wall thickness around a hollow portion and to form a large hollow portion. To provide a method.

[0005]

To achieve the above object, the gist of the method of the present invention is to supply a molten thermoplastic resin onto a lower mold, and to apply the thermoplastic resin to the lower mold. There is a step of molding between the upper molds, and a step of injecting a gas pressurized by a gas injecting means into the cavity formed by the lower mold and the upper mold. It is a molding method for molding a resin molded product so that a hollow portion is formed, wherein the thermoplastic resin supplied onto the lower mold has a multi-layer structure of two or more layers.

[0006]

In the method of molding a resin molded product having a hollow portion as described above, since the thermoplastic resin has a multilayer structure of two or more layers and is supplied onto the lower mold, the gas injected into the cavity is In the thermoplastic resin of the multi-layered structure, it exclusively enters the boundary surface between the first layer penetrated by injection and the second layer on the inner side of the first layer. For this reason, the thermoplastic resin is allowed to flow along the boundary surface between the first layer and the second layer.
Of the upper mold and the lower mold are expanded so as to be separated from each other, and expanded so as to uniformly adhere to the molding surfaces of the upper mold and the lower mold. As a result, an appropriate hollow portion is stably formed in the molded resin molded product, the wall thickness of the resin around it becomes uniform, and the occurrence of defective products can be suppressed to a small extent. In addition, since it is not necessary to set the resin thickness to a large thickness in consideration of the occurrence of a thin portion due to the displacement of the hollow portion, it is possible to form a relatively large hollow portion by reducing the thickness to the necessary and sufficient thickness. Becomes

Further, according to the method of the present invention, for example, the rigidity of the molded article can be improved by appropriately determining the thickness of the first layer, the second layer or the subsequent layers in the multilayer structure and the kind of the resin material. Since the strength can be set arbitrarily with the hollow part as the boundary, the flexibility of the strength design of the resin molded product having the hollow part is expanded, and the resin molding having the hollow part with the minimum amount of material while ensuring the required strength. It is possible to mold the product.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view showing a molding die 12 of a molding apparatus for performing stamping molding by applying the molding method of the present invention. The molding die 12 is a resin molded product having a hollow portion shown in FIG. The vehicle interior component (for example, a package tray) 10 is molded as described above. In FIG. 1, a molding die 12 is a lower die 1 fixed on a bolster 14.
6 and an upper die 20 fixed to a ram 18 driven downward with a predetermined press stroke. In the state where the ram 18 is positioned at the rising end which is the initial position and the molding die 12 is opened, the molten thermoplastic resin 22 is supplied onto the lower die 16 and is superposed thereon. When the material 24 is placed, the ram 18 is driven to the lower end to close the mold 12, and the molding surfaces 26 and 2 of the lower mold 16 and the upper mold 20, respectively.
8, the thermoplastic resin 22 is press-molded into a predetermined shape, and at the same time, the thermoplastic resin 22 and the skin material 24 are integrally bonded. The interior article 10 shown in FIG. 7 is in a final finished state, and the edges thereof are trimmed after or simultaneously with the molding. The molding surface 26 of the lower mold 16 has the lower mold 16 when the mold is closed.
And gas holes 3 for injecting the pressurized gas into the cavity 48 (see FIG. 4) formed by the upper mold 20.
0 is provided at one or more places so that the high pressure gas from the gas supply source 34 can be supplied through the passage 32 in the lower mold 16. In this embodiment, the gas holes 30,
The passage 32 and the gas supply source 34 constitute gas injection means.

As the thermoplastic resin 22, ABS,
Polyethylene, polypropylene resin, etc., or their blends, polymer alloys, and those in which reinforced fibers and inorganic / organic fillers are mixed are used. It is equipped with excellent strength performance. Further, as the skin material 24, a non-woven fabric, a knitted fabric, a woven fabric, or a soft resin film such as a vinyl chloride film lined with them, and a cushion layer laminated with them are used. The interior article 10 is provided with physical properties in terms of properties and feel. As is apparent from FIG. 1, the thermoplastic resin 22 has a two-layer structure composed of an upper layer portion 36 and a lower layer portion 38, and the lower layer portion 38 has a temperature higher than that of the upper layer portion 36 from the molten state. A material whose viscosity changes little with a decrease is used.

The two-layered thermoplastic resin 22 as described above
2 is a resin supply device 40 for supplying resin onto the lower mold 16.
Shown in. The resin supply device 40 is provided in the vicinity of the molding device with a slider device or the like (not shown) so as to extend from the side of the molding die 12 and to arrange the nozzle 44 above the lower mold 16. The nozzle 44 is configured to be horizontally movable in a predetermined direction with respect to the lower mold 16, that is, in the front-rear, left-right direction in FIG. The stamping molding of this embodiment is hot fluid stamping molding, and the two kinds of resins forming the upper layer portion 36 and the lower layer portion 38 of the thermoplastic resin 22 have a melting temperature of 160 ° C. to 250 ° C. in advance.
Each is melted at about ° C and is guided to the nozzle 44. When the resin supply device 40 is operated, the upper layer 36 is interlocked with the horizontal movement of the nozzle 44.
The thermoplastic resin 22 in which the lower portion and the lower portion 38 are integrated is squeezed out downward. The supply amount at this time is an amount that is insufficient to fill the cavity 48 of the molding die 12, that is, an amount that substantially corresponds to the amount obtained by subtracting the volume of the hollow portion 50 in the interior component 10 of FIG. 7. FIG. 3 is a perspective view showing a state where the thermoplastic resin 22 is supplied onto the lower mold 16. In addition,
The nozzle 44 is provided with a heater (not shown) for preventing the temperature of the molten thermoplastic resin 22 from decreasing.

Next, a detailed description will be given of the step of molding the interior product 10 by the above stamping molding apparatus.

First, in the material supplying step, the ram 18
2 with the mold 12 at the rising end and the mold 12 opened.
After the resin supply device 40 extends from the side and the nozzle 44 is positioned above the lower mold 16,
By being horizontally moved to the right in FIG. 2 at a predetermined speed, the molten thermoplastic resin 22 composed of the upper layer portion 36 and the lower layer portion 38 squeezed out from the nozzle 44 is moved to the lower mold 16.
Supplied on. Following this, the skin material 24 conveyed from another place is positioned and arranged on the thermoplastic resin 22 as shown in FIG. At this time, the lower layer portion 38 of the thermoplastic resin 22 comes into contact with the lower mold 16 and is in a state of being cooled to some extent. However, as described above, the resin constituting the lower layer portion 38 is cooled even if the temperature thereof is lowered. Since the viscosity does not change significantly, the fluidity of the resin is ensured and the gas injection resistance does not increase in the subsequent pressing step and gas injection step, so that the interior component 10 can be molded well. A tension force may be applied to the skin material 24 from the surroundings with a predetermined tension by a tension device or the like so as to prevent the formation of wrinkles due to slack. Further, an intermediate adhesive layer such as an adhesive film may be interposed between the thermoplastic resin 22 and the skin material 24.

Next, when the pressing process is started, the ram 1
8 is driven downward from the rising end, and the upper die 20 is lowered toward the lower die 16. The upper die 20 presses the skin material 24 and the thermoplastic resin 22 and descends to the lower end to close the molding die 12, and the lower die 16 and the upper die 20 form a cavity 48. FIG. 4 shows the state at this time. In the narrow portion of the cavity 48, the thermoplastic resin 2
2 and the skin material 24 are press-molded by the molding surfaces 26 and 28 of the lower mold 16 and the upper mold 20, respectively. In the wide portion of the cavity 48, there is a gap between the molding surface 28 of the upper die 20 and the skin material 24, so that the portion is unmolded.

Subsequently, in the gas injection step, the high pressure gas is supplied from the gas supply source 34 through the passage 32 to the gas hole 30 in the lower die 16 and injected into the cavity 48. The gas pressure of the above high-pressure gas is 40 kgf / cm ^{2 to} 150 kg
It is predetermined to a predetermined value suitable for molding the interior component 10 within the range of f / cm ² . FIG. 5 is a diagram showing a transient state at this time, and the injected gas passes through the lower layer portion 38 and then is exclusively applied to the boundary surface 52 between the lower layer portion 38 and the upper layer portion 36, as shown on the left side of FIG. Then, as shown in the right side of FIG. 5, the boundary surface 52 is expanded to form the hollow portion 50 of the interior component 10 while applying pressure so as to separate the upper layer portion 36 and the lower layer portion 38. .. Therefore, the upper layer portion 36 pushes up the skin material 24 toward the molding surface 28 of the upper mold 20 and is expanded without causing an extreme change in wall thickness. On the other hand, the lower layer portion 38 has a cavity 48 along the molding surface 26 of the lower mold 16.
Is made to flow toward the outer peripheral side.

When the gas is continuously supplied and a sufficient gas pressure is applied, the upper layer portion 36 and the lower layer portion 38 of the thermoplastic resin 22 which are spread and separated at the boundary surface 52 are separated from each other by the lower mold. 16 and the upper mold 20 are expanded so as to be in intimate contact with the molding surfaces 26 and 28 of the upper mold 20. As shown in FIG. 6, the upper layer portion 36 and the lower layer portion 38 are molded into a predetermined shape so that the skin material 24 is integrally bonded to the upper layer portion 36, and an appropriate hollow portion 50 having a predetermined volume inside. Is formed, and the stamping molding of the interior component 10 is completed. Here, the hollow portion 50 has a boundary surface 52 formed by gas.
Since the upper layer portion 36 and the lower layer portion 38 are well separated so as to be expanded and are stably formed without being displaced, the wall thicknesses of the upper layer portion 36 and the lower layer portion 38 become appropriate wall thickness dimensions and Be uniform.

In the method for molding the interior component 10 having such a hollow portion, the gas flows into the boundary surface 52 and the upper layer portion 36 and the lower layer portion 38 are well separated, so that the inside of the thermoplastic resin 22 is The appropriate hollow portion 50 is stably formed, and the thicknesses of the upper layer portion 36 and the lower layer portion 38 around the hollow portion 50 are uniform, so that an extremely thin portion does not occur. Can be suppressed to. In addition, since it is not necessary to set the wall thicknesses of the upper layer portion 36 and the lower layer portion 38 to be thicker in consideration of the positional deviation of the hollow portion 50, the wall thickness around the hollow portion 50 can be reduced to a necessary and sufficient thickness. It becomes possible to form a relatively large hollow portion 50.

Further, in the present embodiment, as the resin forming the lower layer portion 38, a material having a smaller viscosity change than the upper layer portion 36 due to the temperature decrease from the molten state is used, so that the resin fluidity is good in the pressing step and In the gas injection step, there is an advantage that the injection resistance is kept small and the hollow portion 50 is well formed.

Further, according to the molding method of the present embodiment, the thickness of the upper layer portion 36 and the lower layer portion 38 above and below the boundary surface 52 in the two-layer structure are appropriately changed and set, whereby the interior component 10 is Since the strength such as rigidity can be arbitrarily set on the upper side and the lower side of the hollow portion 50, the flexibility of the strength design of the interior article 10 is expanded, and the interior article is made of the minimum amount of material while ensuring the required strength. It is possible to mold 10.

The vehicle package tray has conventionally been formed by inserting a reinforcing material such as a sheet metal member, but according to the interior component 10 of this embodiment in which the hollow portion 50 is formed, no reinforcing material is required. And the weight is reduced,
There are advantages such as easy separation processing during recycling.

Next, another embodiment of the material supplying step in the method of the present invention will be described.

In the material supply process by the resin supply device 60 shown in FIG. 8, the resin is supplied in a supply form different from that in the above-mentioned embodiment. Resin supply device 60
Like the resin supply device 40, is disposed in the vicinity of the molding device so as to extend laterally above the lower mold 62 and nozzles the thermoplastic resin 64 along a predetermined direction with respect to the lower mold 62. It can be squeezed out from 66. This thermoplastic resin 64 has a concentric biaxial structure, and as can be seen from FIG. 9 which is a sectional view taken along line IX-IX in FIG.
It is composed of an inner layer portion 68 and an outer layer portion 70 surrounding the inner layer portion 68 concentrically. The two types of resin forming the inner layer portion 68 and the outer layer portion 70 are introduced into the nozzle 66 through the inside of the resin supply device 60 in a molten state. In the outer layer portion 70, as in the lower layer portion 38,
A material having a smaller viscosity change than the inner layer portion 68 with respect to the temperature decrease from the molten state is used. 10 is a sectional view taken along line XX in FIG.

Although not shown, this resin supply device 60
When the gas is injected from the gas holes 74 into the thermoplastic resin 64 supplied by the gas, the gas is injected into the inner layer portion 68 and the outer layer portion 70.
Of the thermoplastic resin 64, the pressure is applied so that the boundary 72 is expanded to separate the inner layer portion 68 and the outer layer portion 70 from each other. Can be formed. As a result, a relatively large hollow portion can be formed while ensuring a thickness not less than a certain value when the outer layer portion 70 is expanded, and the thin portion is locally thinned or the hollow portion is opened. It is possible to suppress the generation of defective products.

The resin supply device 80 shown in FIG. 11 has an inner layer portion 6 of the thermoplastic resin 64 in the resin supply device 60 described above.
8 is replaced by an air layer 82, and X in FIG.
As shown in FIG. 12, which is a sectional view taken along line II-XII, the thermoplastic resin 84 is formed into a hollow cylindrical shape and is squeezed out from the nozzle 86. The thermoplastic resin 84 in a state of being supplied onto the lower mold 88 is in a state in which the air layer 82 is crushed by its own weight, but FIG. 13 is a sectional view taken along line XIII-XIII in FIG.
As shown in FIG. 13A or FIG. 13B, an air layer 82 partially exists inside. This thermoplastic resin 84
When the gas is injected from the gas holes 92 into the crushed air layer 82, the gas exclusively enters the crushed air layer 82 and exerts a pressure so as to restore the air layer 82.
An appropriate hollow portion can be stably formed inside the inside of the inner wall 4. As a result, the thickness of the thermoplastic resin 84 becomes uniform, and a resin molded product having a relatively large hollow portion can be molded while ensuring the required strength.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, in the above-described embodiment, the thermoplastic resin 2
The case where the molding method of the present invention is applied to the molding of the interior component 10 for a vehicle in which the skin material 24 is integrally bonded to 2 is applied. However, in addition to this, in the interior wall, fittings, furniture, etc. The molding method of the present invention can be similarly applied to the molding of a resin molded product having a hollow portion.

Further, in the above-mentioned embodiment, the hot fluid stamping molding in which the thermoplastic resin 22 is in a molten state at a melting temperature of about 160 ° C to 250 ° C is used.
The molding method of the present invention can also be applied to the solid-phase stamping molding of a thermoplastic resin heated to 30 ° C to 150 ° C.

In the above-described embodiment, the thermoplastic resin 22 is composed of two layers, the upper layer portion 36 and the lower layer portion 38, and the thermoplastic resin 64 is the inner layer portion 68 and the outer layer portion 7.
Although it is composed of two layers of 0, each may have a multilayer structure of three layers or more, and may include an air layer inside thereof.

Further, in the above-described embodiment, the lower layer portion 38 of the thermoplastic resin 22 and the outer layer portion 70 of the thermoplastic resin 64 are used.
However, in order to secure the resin fluidity in the pressing process and to reduce the injection resistance in the gas injection process, the lower mold 16,6
Although a material having a small viscosity change with respect to the temperature decrease when contacting with 2 has been used, selection of such a resin is not essential in the present invention.

Further, in the above-mentioned embodiment, the thermoplastic resin 2 squeezed out from the resin supply device 40, 60, 80.
2, 64, 84 were supplied onto the lower molds 16, 62, 88, respectively, but in addition to this, the heated thermoplastic resin is conveyed to another place apart from the molding apparatus to form a multilayer structure. Various supply forms can be carried out without any problem even if they are stacked in such a manner that they are stacked, or they are heated and transported in advance in the state of a multilayer structure and supplied in the state shown in FIG.

Further, in the above embodiment, the gas holes 3
Although 0, 74 and 92 are provided in the lower molds 16, 62 and 88 to inject gas into the cavity 48, the gas does not necessarily have to be injected from the lower mold. Further, the number of gas holes can be appropriately changed according to the shape of the molded product, and the number of gas holes can be one or more.

Further, in the above-described embodiment, the high pressure gas is supplied by entering the gas injection step after closing the upper die 20 and the lower die 16 in the pressing step, but from the middle of the pressing step. It does not matter if the gas injection process is started.

Although not illustrated one by one, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a sectional view of a molding die of a stamping molding apparatus which is an embodiment to which a molding method of the present invention is applied.

FIG. 2 is a diagram showing a material supply process by a resin supply device of the molding apparatus of FIG.

FIG. 3 is a perspective view showing a thermoplastic resin supplied onto a lower mold in the molding apparatus of FIG.

FIG. 4 is a cross-sectional view showing a pressing step in the molding apparatus of FIG.

5 is a cross-sectional view showing a transient state of a gas injection process in the molding apparatus of FIG.

FIG. 6 is a cross-sectional view showing a state where a gas injection step has been completed in the molding apparatus of FIG.

7 is a cross-sectional view showing a final finished state of a resin molded product having a hollow portion molded by the molding device of FIG.

FIG. 8 is a cross-sectional view showing another aspect of the material supplying step in the molding method of the present invention.

9 is a sectional view taken along line IX-IX in FIG.

10 is a sectional view taken along line XX in FIG.

FIG. 11 is a cross-sectional view showing another aspect of the material supplying step in the molding method of the present invention.

12 is a sectional view taken along line XII-XII in FIG.

13 is a sectional view taken along line XIII-XIII in FIG.

[Explanation of symbols]

 10: Interior product (resin molded product having a hollow part) 16, 62, 88: Lower mold 20: Upper mold 22, 64, 84: Thermoplastic resin 30, 74, 92: Gas hole 32: Passage 34: Gas supply source 36: Upper layer part 38: Lower layer part 48: Cavity 50: Hollow part 68: Inner layer part 70: Outer layer part 82: Air layer

Claims (1)

[Claims] 1. A step of supplying a molten thermoplastic resin onto a lower mold, a step of molding the thermoplastic resin between the lower mold and the upper mold, and a cavity formed by the lower mold and the upper mold. And a step of injecting a gas pressurized by a gas injecting means into the thermoplastic resin, which is a molding method for molding a resin molded article so that a hollow portion is formed by the gas inside the thermoplastic resin, A method for molding a resin molded product having a hollow portion, wherein the thermoplastic resin supplied onto the lower mold has a multi-layer structure of two or more layers.