JPH091564A - Manufacture of foamed resin molding - Google Patents

Abstract

PURPOSE: To be able to mold with excellent mold releasability without using a mold release agent by disposing a resin sheet having mold releasability previously formed in a mold surface shape on a least one mold surface of split molds. CONSTITUTION: A predetermined quantity of a foamed resin is injected from an injection port in a cavity space formed between a resin sheet 10 for an upper mold and a resin sheet 20 for a lower mold after the upper mold 1 and the lower mold 2 are closed, and foam-molded. Since the formed molding has mold releasability at the sheet 10 for the upper mold and the sheet 20 for the lower mold, it is easily released, and the sheet 10 for the upper mold and the sheet 20 for the lower mold are again used for molding. Accordingly, since the molding can be conducted almost without using the agent, various malfunction due to the agent is avoided.

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 foamed resin molded article, and more particularly to a method for producing a foamed resin molded article which does not require a release agent.

[0002]

2. Description of the Related Art For example, in foam molding of urethane,
First, a mold release agent is applied to the mold surface of the split mold, and then a foaming resin material is injected to mold. Therefore, the release agent may adhere to the surface of the molded product, resulting in a defect. For example, when coating a molded product, if a release agent is attached, coating defects such as cissing and poor adhesion are likely to occur. In order to prevent such an obstacle, it is necessary to wash the molded product before coating to remove the release agent, which results in a large number of steps.

Further, when the mold release agent is applied to the mold surface, it is necessary to apply it to every corner of the complicated mold surface, so that the number of man-hours for the coating operation is large. Further, since the mold release agent may be deposited on the mold surface to impair the shape of the molded product, there is a problem that the mold surface must be frequently washed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to perform molding with good mold releasability using little or no mold release agent.

[0005]

A method for producing a foamed resin molded article according to the present invention, which solves the above-mentioned problems, is a method in which a resin sheet having releasability formed in advance in a mold surface shape is used for at least one of split molds. It is arranged on the mold surface, a foamed resin material is supplied between the resin sheet and the mold surface of the other mold to mold the molded product, and the split mold is opened to release the molded product from the resin sheet. To do.

As the resin sheet, a releasable sheet having poor adhesion to the molding material is used, and for example, polypropylene (PP), silicone resin, fluorine resin such as "Teflon" (trademark), etc. can be used. . Further, in order to form the resin sheet in the mold surface shape in advance, it can be formed by using vacuum molding, pressure molding, compression molding, injection molding, blow molding or the like.

Since the amount of compressive deformation also increases as the thickness of this resin sheet increases, it is desirable that the resin sheet be thin, but if it is too thin, the strength will be low and it will be easily damaged, making repeated use difficult. Therefore, it is preferable that the optimum thickness (t) of the resin sheet is 0.2 mm or more and the thinnest possible thickness is used. By the way, when the thickness of the resin sheet is partially non-uniform, the adhesiveness between the mating mold and the resin sheet on the mold splitting surface when the mold is closed is impaired, and burrs of the molded product occur due to extrusion of the foamed resin material. There are cases. Therefore, in the method for manufacturing a foamed resin molded product of the second invention which prevents such a problem, an elastic sealing material is arranged between the resin sheet and one of the molds on the split surface of the split mold, and the elastic sealant is elastic when the mold is closed. It is characterized in that the sealing material is configured to elastically deform.

By arranging the elastic sealing material in this way, the elastic sealing material is elastically deformed by the mold closing force, and the resin sheet is pressed against the mating mold by the reaction force, so that the leakage of the foamed resin material is prevented. You can Even in the conventional foam molding, an elastic sealing material is arranged between the pair of split molds to prevent the foamed resin material from leaking. However, in this case, since the elastic sealant is in direct contact with the release agent and the foamed resin material, it is necessary to select an elastic sealant that is not easily attacked by the solvent in which the release agent is dissolved or the foamed resin material. However, the durability was not sufficient.

However, in the present invention, since the foamed resin material and the elastic sealing material do not come into direct contact with each other, the elastic sealing material may be any of known elastically deformable sealing materials such as urethane foam, rubber sponge, silicone sponge and nonwoven fabric. Choices are made and durability issues are resolved. It is desirable that the elastic sealing material is provided in a ring shape that goes around the cavity.

Further, in the case of foam molding, it is necessary to let the foaming gas escape to the outside during molding in order to prevent defective molding due to gas accumulation. In the method for producing a foamed resin molded product of the third invention, which allows the foaming gas to easily escape when a resin sheet is used, a cavity and an external space are provided between the resin sheet and the other mold on the split surface of the split mold. It is characterized in that a gas vent groove communicating with and is provided.

The degassing groove may be provided in the other mold, or may be provided in one mold and the resin sheet may be provided with a groove having substantially the same shape as this groove. Further, when a pair of resin sheets is provided on both mold surfaces, a gas vent groove is formed between the pair of resin sheets, so that contact between the foamed resin material and the mold surface does not occur and the gas vent groove is also formed. There is no need to apply a release agent.

On the other hand, when air tends to remain between the resin sheet and the mold surface, such as when the resin sheet has a non-uniform thickness, it is difficult to arrange the resin sheet along the mold surface without fail. May be In the method for producing a foamed resin molded article according to the fourth aspect of the invention, which prevents such a problem, at least one of the split molds has a vent hole that communicates the space between the mold surface of the one mold and the resin sheet with the outside. It is provided that the air existing in the space is discharged from the ventilation hole when the resin sheet is arranged on the mold surface. As a result, the resin sheet surely comes into close contact with the mold surface, and it is possible to accurately manufacture a molded product having a mold surface shape.

Further, in the method for producing a foamed resin molded product according to the fifth invention which prevents the above-mentioned problems, at least one of the split molds has a vent hole for communicating the space between the mold surface of the one mold and the resin sheet with the outside. When the resin sheet is placed on the mold surface, the resin sheet is brought into close contact with the mold surface by vacuum suction through the ventilation hole, and when the molded product is released from the mold, pressurized air is supplied through the ventilation hole. By doing so, the resin sheet is separated from the mold surface.

If pressurized air is supplied from the ventilation hole when the mold is opened, the resin sheet is lifted from the mold surface together with the molded product by the compressed air, and the mold release becomes easier. In the case of integral skin molding, it is sufficient to place the resin sheet on the mold surface of one mold, but if not, the resin sheet is formed so as to be arranged on the mold surfaces of all the split molds. Is desirable. For example, when a pair of upper and lower molds is used, it is preferable to use a pair of resin sheets having respective mold surface shapes.

Even when a plurality of resin sheets are used, it is desirable to dispose an elastic sealing material between the resin sheet and one of the molds on the split surface of the split mold as described above. With this configuration, the reaction force due to the elastic deformation of the elastic sealing material strengthens the pressure contact force between the resin sheets facing each other, and the leakage of the foamed resin material from between the resin sheets is prevented.

Further, in the case of foam molding, an injection port for injecting a foam resin material may be provided on a mold splitting surface or the like. However, since the foam resin material comes into contact with the injection port, conventionally the injection port and its It was also necessary to apply a release agent to the plug that blocks the inlet. In the method for producing a foamed resin molded product according to the sixth invention for solving this problem, the resin sheet is arranged in each of a plurality of split molds, and the foamed resin material is arranged between a pair of resin sheets arranged to face each other. It is characterized in that it is injected from an injection port formed from a part of. As a result, it becomes unnecessary to apply the release agent to the injection port, and it is not necessary to apply the release agent at all.

[0017]

In the method for producing a foamed resin molded product of the present invention, a resin sheet having a mold surface shape is formed in advance. This can be easily formed by using a mold having an exactly desired mold surface and molding it so as to have a predetermined thickness. Even when the resin sheet is repeatedly used, it is preferable to previously form a plurality of resin sheets. When resin sheets are used for a plurality of molds, it is necessary to mold the mold surface shape of each mold.

This resin sheet is placed on the mold surface of at least one of the split molds before molding. The mold surface of one of the molds may be formed in the shape of the back surface of the resin sheet, and does not necessarily have to have a shape similar to the target surface of the molded product. 4th
If the vent hole is provided in one of the molds as in the invention or the fifth invention, the resin sheet and the mold surface can be surely brought into close contact with each other by pressing with a hand or suction from the vent hole. At this time, since the foamed resin material contacts only the resin sheet on at least one of the mold surfaces, it is not necessary to apply the release agent.

After the mold is closed, a molded product is molded in a cavity formed between the resin sheet and the other mold (counter mold). When the resin sheet is also arranged in the mating mold, the molded product is molded in the cavity formed by the resin sheets. When the injection port is formed of a resin sheet as in the sixth invention, the foamed resin material is injected from the injection port and foam molding is performed. Of course, it is not necessary to apply a release agent to the injection port.

At this time, if the elastic sealing material is interposed as in the second aspect of the invention, the resin sheet and the mating mold or the resin sheets are surely pressed against each other on the mold splitting surface, so that the foamed resin material is surely prevented from protruding. It prevents the occurrence of burr. If a gas vent groove is provided as in the third aspect of the invention, the gas during foam molding can be easily released. After molding, the split mold is opened and the molded product is taken out. At this time, as in the fifth aspect of the invention, the molded product can be easily released from the mold together with the resin sheet by supplying the pressurized air from the ventilation hole. If the resin sheet is thin, the molded product can be easily demolded by peeling the resin sheet while deforming it.

[0021]

The present invention will be specifically described below with reference to examples. (Embodiment 1) FIG. 1 shows a cross-sectional view of a foam molding die used in this embodiment. This mold consists of an upper mold 1 and a lower mold 2,
An upper die resin sheet 10 is arranged on the die surface of the upper die 1, and a lower die resin sheet 20 is placed on the die surface of the lower die 2. The upper mold resin sheet 10 and the lower mold resin sheet 2
0 is formed from PP to a thickness of 0.2 to 0.5 mm, and has the mold surface shapes of the upper mold 1 and the lower mold 2, respectively, and has a mold surface having a predetermined molded product shape on the back surface. It is formed by vacuum forming in advance.

In the mold constructed as described above, the upper mold 1
After the lower mold 2 is closed, a predetermined amount of foamed resin is injected into the cavity space formed between the upper mold resin sheet 10 and the lower mold resin sheet 20 from an injection port (not shown) to perform foam molding. Be seen. The formed product is easily released from the upper mold resin sheet 10 and the lower mold resin sheet 20 because they have mold releasability, and the upper mold resin sheet 10 and the lower mold resin sheet 20 are separated from each other. It is used again for molding. Therefore, in this embodiment, since the molding can be performed with almost no release agent, various problems due to the release agent are avoided. (Example 2) In Example 1, the upper mold resin sheet 10 was used.
Alternatively, when the thickness of the lower mold resin sheet 20 is not uniform or when the mold closing force is small, the foamed resin protrudes between the upper mold resin sheet 10 and the lower mold resin sheet 20 on the mold splitting surface. May be burr. When burrs are generated in this manner, a post-processing step of cutting the burrs from the molded product after molding is required, resulting in an increase in man-hours.

Therefore, in this embodiment, as shown in FIG. 2, a ring groove 21 is formed around the cavity of the lower mold 2 at the boundary with the cavity, and a ring made of urethane foam is formed in the ring groove 21. The seal ring 3 in the shape of a circle is arranged.
The seal ring 3 is arranged in the ring groove 21 and approximately half of its cross-sectional area projects from the mold split surface. Then, when the lower die resin sheet 20 is placed on the lower die 2 and the die is closed with the upper die 1 having the upper die resin sheet 10, the seal ring 3 is pressed by the lower die resin sheet 20 on the die splitting surface and is elastic. Deformation occurs, and conversely, the elastic force from the seal ring 3 locally acts on the lower mold resin sheet 20. Therefore, due to the elastic force from the seal ring 3, the pressure contact force between the lower mold resin sheet 20 and the upper mold resin sheet 10 is increased at the position of the seal ring 3, and a high sealing property is exhibited.

Therefore, in the present embodiment, even if the upper mold resin sheet 10 or the lower mold resin sheet 20 has a non-uniform thickness or the mold closing force is small, the upper mold resin sheet is used on the mold dividing surface. It is possible to prevent the foamed resin from protruding between the resin sheet 10 and the lower mold resin sheet 20 to form burrs, and it is possible to manufacture a molded product that does not require post-processing. (Embodiment 3) In the case of foam molding, it may be necessary to allow foam gas to escape from the cavity during or after molding. Therefore, in this embodiment, as shown in FIG. 3, a mold groove 11 that communicates the cavity with the outside is provided on the mold dividing surface of the upper mold 1, and the upper mold resin sheet 10 is protruded to the back surface side and fitted into the mold groove 11. The convex portion 12 is provided. A sheet groove 13 is formed on the surface side of the convex portion 12.

Since the sheet groove 13 communicates with the cavity space and the outside, it functions as a gas vent groove for allowing the foaming gas to easily escape to the outside of the mold, and it is possible to prevent the occurrence of defective products due to gas accumulation. Further, when the seal ring 3 is provided on the mold split surface as in the second embodiment, the seal ring 3 is partially cut off at the mold groove 11. As a result, the seat groove 1
Since the elastic force from the seal ring 3 does not act on 3,
Communication between the cavity space and the outside is ensured, and the seat groove 13
Functions as a gas vent groove.

When the mold closing force is small, the seal ring 3 may be partially cut off without forming the mold groove 11 and the seat groove 13. In this case, the pressure contact force between the upper mold resin sheet 10 and the lower mold resin sheet 20 becomes small at the portion where the seal ring 3 is cut off, and the gas can escape to the outside. (Embodiment 4) FIG. 4 shows a sectional view of a foam molding die used in Embodiment 4. This mold is the same as that of the second embodiment except that the upper mold 1 and the lower mold 2 have a plurality of vent holes 14 and 22 for communicating the mold surface with the outside.

The ventilation holes 14 and 22 are connected to a vacuum source and a compressed air source, respectively, which are not shown, and are configured so that the supply of vacuum-compressed air can be switched by a timer and a solenoid valve (not shown). In this embodiment, first, the seal ring 3 is arranged in the mold groove 11 on the mold dividing surface of the lower mold 2, and the upper mold resin sheet 10 and the lower mold resin sheet 20 are respectively arranged on the mold surface. Then, a vacuum source is connected to the ventilation holes 14 and 22, and a negative pressure is supplied between the mold surfaces of the upper mold 1 and the lower mold 2 and the upper mold resin sheet 10 and the lower mold resin sheet 20. As a result, the upper mold resin sheet 10 and the lower mold resin sheet 20 are adsorbed to the mold surfaces of the upper mold 1 and the lower mold 2, respectively, and an accurate mold surface shape is secured.

In this state, foam molding is performed in the same manner as in Example 1, and the upper mold 1 and the lower mold 2 are opened after the molding is completed. At this time, the molded product is in close contact with the lower mold resin sheet 20 on the lower mold 2 side. Then, a compressed air source is connected to the ventilation hole 22, and pressurized air is supplied between the mold surface of the lower mold 2 and the lower mold resin sheet 20. As a result, the lower mold resin sheet 20 is peeled off from the mold surface of the lower mold 2 while being in close contact with the molded product. Since the lower mold resin sheet 20 is easily deformed, it can be peeled off from the molded product so that the molded product can be easily released from the mold. (Embodiment 5) In foam molding, it is desirable to form a mold with an injection port for injecting the foam resin into the cavity. However, since the foamed resin adheres to the injection port, it is necessary to apply the release agent to the injection port and the plug that closes the injection port.

Therefore, in this embodiment, as shown in FIG. 5, the upper mold resin sheet 10 and the lower mold resin sheet 20 are injected into the injection port 15 formed in the mold dividing surface of the upper mold 1 and the lower mold 2. Groove 1
6, 23 are engaged with each other. Then, the space surrounded by the injection grooves 16 and 23 is used as an injection port. With this structure, it is not necessary to apply the release agent to the injection port. Further, if the plug itself is formed of a releasing resin such as PP, it is not necessary to apply the releasing agent, and it is possible to eliminate the use of the releasing agent in foam molding.

In the above embodiment, the upper mold resin sheet 1 is used.
0 and the injection groove 16 and 23 of the lower mold resin sheet 20 formed the injection hole, but as shown in FIG. 6, one resin sheet (here, the upper mold resin sheet 10) should form the injection hole. You can also (Embodiment 6) FIG. 7 shows a mold used in this embodiment and a sectional view showing the inside of the mold immediately before molding. This mold is composed of an upper mold 1 ′ and a lower mold 2 ′, and a skin 4 is arranged on the mold surface of the lower mold 2 ′. An upper mold resin sheet 10 'is arranged on the mold surface of the upper mold 1'. Between the skin 4 and the upper mold resin sheet 10 ′, the resin core material 5 is held in a floating state on the pin 24 protruding from the lower mold 2 ′ and penetrating the skin 4.

In this embodiment, when the upper mold 1'and the lower mold 2'are closed, the foamed resin is injected between the skin 4 and the upper mold resin sheet 10 'to perform foam molding. The skin 4 and the upper mold resin sheet 10 'are pressed against each other on the mold splitting surface, and the skin 4 develops self-elasticity due to compression. Therefore, the skin 4 and the upper mold resin sheet 10' are in close contact with each other and the foamed resin is provided therebetween. It is prevented that it protrudes and becomes a burr.

By the foaming of the foamed resin, the upper mold resin sheet 10 'and the skin 4 are pressed against the mold surfaces of the upper mold 1'and the lower mold 2', respectively, to have an accurate mold surface shape, and the core material 5 is embedded. A molded product whose surface is integrally covered with the skin 4 is manufactured. Even when the resin sheet is arranged only on one of the mold surfaces as in the present embodiment, application of the release agent is almost unnecessary, and various problems caused by the release agent are avoided.

[0033]

[Effects of the Invention] That is, according to the method for producing a resin molded product of the present invention, since it is possible to produce with good releasability without using a release agent, various problems caused by the release agent can be avoided. be able to. According to the manufacturing method of the second aspect of the invention, burrs can be effectively prevented, and according to the third aspect of the invention, problems due to gas accumulation can be reliably prevented.
Further, according to the fourth and fifth aspects, the resin sheet can be surely brought into close contact with the mold surface, so that the defective shape can be prevented. According to the fifth aspect, the molded product can be easily released from the mold, and according to the sixth aspect, the use of the release agent can be further reduced and the release agent can be eliminated at all. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mold used in one embodiment of the present invention before mold closing.

FIG. 2 is a sectional view of a main part of a mold used in a second embodiment of the present invention before closing the mold.

FIG. 3 is a sectional view of an essential part of a mold used in a third embodiment of the present invention after the mold is closed.

FIG. 4 is a cross-sectional view of a mold used in a fourth embodiment of the present invention before closing the mold.

FIG. 5 is a cross-sectional view of an essential part of a mold used in a fifth embodiment of the present invention after the mold is closed.

FIG. 6 is a cross-sectional view showing another embodiment of the mold used in the fifth embodiment of the present invention after the mold is closed.

FIG. 7 is a sectional view of a mold used in a sixth embodiment of the present invention before mold closing.

[Explanation of symbols]

1: Upper mold 2: Lower mold 3: Seal ring (elastic sealing material) 4: Skin 5: Core material 10: Upper mold resin sheet 15: Injection port 20: Lower mold resin sheet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B29C 39/28 7726-4F B29C 39/28 // B29K 105: 04

Claims (6)

[Claims] 1. A mold-releasing resin sheet formed in advance in a mold surface shape is disposed on the mold surface of at least one of the split molds, and foam is formed between the resin sheet and the mold surface of the other mold. A method for producing a foamed resin molded product, comprising supplying a resin material to mold a molded product, opening the split mold, and releasing the molded product from the resin sheet. 2. An elastic seal member is arranged between the resin sheet and the one mold on the mold split surface of the split mold, and the elastic seal member is elastically deformed when the mold is closed. The method for producing a foamed resin molded article according to claim 1. 3. A degassing groove is provided between the resin sheet and the other mold on the mold split surface of the split mold, the gas vent groove communicating the cavity with the outside. Of the foamed resin molded article of. 4. At least one of the split molds is provided with a ventilation hole that communicates a space between the mold surface of the one mold and the resin sheet with the outside, and the resin sheet is arranged on the mold surface. The method for producing a foamed resin molded article according to claim 1, wherein the air present in the space is discharged from the ventilation hole during the process. 5. At least one of the split molds is provided with a ventilation hole that communicates a space between the mold surface of the one mold and the resin sheet with the outside, and the resin sheet is arranged on the mold surface. In this case, the resin sheet is brought into close contact with the mold surface by vacuum suction through the ventilation hole, and when the molded product is released from the mold, pressurized air is supplied through the ventilation hole to the resin sheet. The method for producing a foamed resin molded article according to claim 1, wherein the mold is separated from the mold surface. 6. The resin sheet is arranged in each of a plurality of split molds, and the foamed resin material is formed between a pair of the resin sheets arranged to face each other, and an injection port formed from a part of the resin sheet. The method for producing a foamed resin molded article according to claim 1, further comprising injecting.