JP7567697B2 - Rotational molding apparatus and method - Google Patents

Description

This disclosure relates to a rotational molding device that enables molding of multiple different colored materials onto the surface of a hollow molded product, and a rotational molding method performed by the rotational molding device.

Patent Document 1 describes a multi-color slush molding method in which the space inside a mold is divided by partitions, and different colored powders are filled into each divided space to form different colored surface layers along the inner surface of each mold.

Japanese Patent Application Publication No. 5-309675

However, the above-mentioned conventional technology is a molding method for non-hollow resin molded products that have a front and back surface. Therefore, even if the partition plate of the above-mentioned conventional technology is applied to rotational molding for molding hollow resin molded products, the partition plate will remain in the hollow internal space of the molded product, and a new means for recovering the partition plate is required, which increases the number of processes and the cost.

Therefore, there is a need for a technology that can easily realize rotational molding of hollow molded products with multiple surface layers while minimizing increases in the number of processes and costs.

This disclosure can be realized in the following forms:

(1) According to one embodiment of the present disclosure, a rotational molding device for molding a hollow molded product having a plurality of surface layers is provided. The rotational molding device includes a rotational molding die having a plurality of mold parts divided along a parting line, a partition member disposed between the mold parts on both sides of the parting line and partitioning the mold space of the rotational molding die into mold space parts corresponding to the mold parts on both sides, and a heating device for heating the rotational molding die in rotational molding for melting a molding material disposed in the mold space part . The partition member is a member having a melting temperature equal to or higher than the melting temperature of the molding material. The heating device heats the first stage rotational molding at a first heating temperature that is equal to or higher than the melting temperature of the molding material and lower than the melting temperature of the partition member, and heats the second stage rotational molding after the first stage rotational molding at a second heating temperature that is equal to or higher than the melting temperature of the partition member.
According to this form of rotational molding device, during rotational molding, while the surface layer is being molded by welding the molding material to the inner surface of the rotational molding die, the rotational molding die is heated so that the partition member does not melt, thereby preventing the molding materials placed in the partitioned mold space from mixing with each other. In addition, by melting the partition member after molding the surface layer, it is possible to eliminate the need to recover the partition member remaining in the hollow of the molded product. This makes it possible to simply realize the rotational molding of a hollow molded product having multiple surface layers while suppressing an increase in the number of processes and costs.
(2) In the rotational molding apparatus of the above-described form, a fixing member that clamps and fixes the partition member between the mold parts on both sides, the fixing member having a lower thermal conductivity than the rotational molding die, may be provided.
With this form of rotational molding device, while the surface layer is being molded by welding the molding material to the inner surface of the rotational molding die, the sealing member can delay the temperature of the partition member from rising to its melting temperature so as to prevent the molding material placed in the partitioned mold space from being mixed in .
(3 ) In the rotational molding apparatus of the above-mentioned form, there may be two partition members stacked with a space between them between the mold parts on both sides, and the space between the two partition members may be a space in which a molding material is placed to be used for molding a layer that is laminated on the inner surface of a surface layer that is molded with the molding material.
According to the rotary forming apparatus of this embodiment, the partition member is melted after forming the surface layer, whereby the layer to be laminated on the inner surface of the surface layer can be formed.
The present disclosure can be realized in various forms, such as a rotational molding method, in addition to the rotational molding apparatus of the above-mentioned form.

1 is an explanatory diagram showing a schematic configuration of a rotational molding device as a first embodiment. FIG. FIG. 2 is an explanatory diagram showing an enlarged view of an area Aea shown in FIG. 1 . 1 is an explanatory diagram showing a lower mold from the upper mold side before the upper mold is mated with the lower mold; FIG. 1A to 1C are explanatory diagrams illustrating a rotational molding method performed by a rotational molding device. FIG. 5 is an explanatory diagram showing an enlarged view of a region Aeb of the molded product shown in FIG. 4 . FIG. 11 is an explanatory diagram showing a schematic configuration of a rotational molding device as a second embodiment. 7 is an explanatory diagram showing an enlarged view of a part of a molded product produced by the rotational molding apparatus of FIG. 6. FIG. 11 is an explanatory diagram showing a schematic configuration of a rotational molding device as a third embodiment. FIG. 9 is an explanatory diagram showing a molded product produced by the rotational molding apparatus of FIG. 8 .

A. First embodiment:
FIG. 1 is an explanatory diagram showing a schematic configuration of a rotational molding apparatus according to a first embodiment. This rotational molding apparatus includes a rotational molding die 100, and a rotation device and a heating device (not shown). The rotation device is a device that rotates a die in rotational molding, and can be a device of various rotation types, such as a device of a rotation type ("single-axis rotation + swing motion" type) that rotates a die on a table that swings widely from side to side like a pendulum, or a device of a two-axis rotation type. The heating device is a device that heats a die in rotational molding, and can be a device of various heating types, such as a direct flame type, a hot air circulation oven type, and a medium circulation type. Note that FIG. 1 shows an example of the rotational motion of a die by a rotation type (single-axis rotation + swing motion) and the heating of the die by a hot air circulation oven type.

The rotational molding die 100 is composed of a lower die 110 and an upper die 120, which are multiple die parts that are divided along a parting line PL. The lower die 110 has a die structure part 111 and a flange part 112. The upper die 120 also has a die structure part 121 and a flange part 122. The die structure part 111 and the die structure part 121 are parts that constitute the die space 102 of the rotational molding die 100. The flange part 112 and the flange part 122 are parts that are fastened to fix the die structure part 111 and the die structure part 121 in a mold-matched state. The rotational molding die 100 is composed of various metal materials such as SS (structural rolled steel), aluminum, nickel, etc.

Between the lower die 110 and the upper die 120, which are the die parts on both sides of the die parting line PL, a film-like partition member 130 is arranged along the die parting line PL. The partition member 130 is sandwiched and fixed between the lower die 110 and the upper die 120 via a seal member 140 provided at the end of the die space 102 side of the lower die 110 and the upper die 120, respectively. The seal member 140 is a fixing member that sandwiches and fixes the partition member 130 between the lower die 110 and the upper die 120. The seal member 140 is also a member that seals the die space 102. The partition member 130 is a member that partitions the die space 102 into a die space portion 102L on the lower die 110 side and a die space portion 102U on the upper die 120 side. The mold space portion 102L of the lower mold 110 is the portion into which the first molding material m1 is poured during rotational molding, and the mold space portion 102U of the upper mold 120 is the portion into which the second molding material m2 is poured during rotational molding.

The molding materials m1 and m2 are made of the same type of thermoplastic resin material but different colors. As the same type of resin material, various resin materials can be used, such as various general-purpose resins such as PP (polypropylene), PC (polycarbonate), PA (polyamide), PVC (polyvinyl chloride), ABS, PMMA, etc., and various elastomer resins such as TPO, TPC, TPU, etc. Resin materials of different colors are, for example, materials in which the same type of resin material mentioned above contains different coloring materials.

It is preferable that the partition member 130 is made of the same type of resin material as the molding material used. Also, a resin material different from the molding material used may be used for the partition member 130. In this case, however, it is preferable that a resin material that has good bonding properties between the molding material and the partition member when the partition member is melted in the rotational molding described below is used. Also, a material that has a higher melting temperature than the melting temperature of the molding materials m1 and m2 is used for the partition member 130.

The sealing member 140 can be made of various materials that have lower thermal conductivity than the metal members that make up the rotational molding die 100 and have higher heat resistance than the heating temperature. For example, a sealing member made of a silicone resin material can be used.

2 is an explanatory diagram showing an enlarged view of the area Aea shown in FIG. 1. FIG. 3 is an explanatory diagram showing the lower mold 110 from the upper mold 120 side before the upper mold 120 is matched. As shown in FIGS. 2 and 3, the flange portion 112 of the lower mold 110 is provided with a plurality of pins 113 along the outer periphery of the mold structure portion 111. The partition member 130 is provided with pin holes 133 into which each pin 113 is inserted. As shown in FIG. 3, the partition member 130 is placed on the lower mold 110 so that each pin 113 of the lower mold 110 is inserted into each pin hole 133 of the partition member 130, whereby the partition member 130 is fixed by each pin 113 and held on the lower mold 110. Therefore, the second molding material m2 to be poured into the mold space portion 102U of the upper mold 120 can be placed on the partition member 130 as shown in FIG. 3. This allows the second molding material m2 to be placed on the partition member 130 before the upper mold 120 is aligned and placed on the lower mold 110.

2, the flange portion 122 of the upper mold 120 is provided with pin holes 123 at positions corresponding to the pins 113 of the lower mold 110. By placing the upper mold 120 on the lower mold 110 so that the pins 113 of the lower mold 110 are inserted into the pin holes 123 of the upper mold 120, the upper mold 120 can be easily aligned with the lower mold 110. Therefore, each pin 113 of the lower mold 110 is used as a partition member holding pin for holding the partition member 130 on the lower mold 110, and also as a reference pin for alignment.

The multiple holes 114 provided in the flange portion 112 of the lower mold 110 shown in FIG. 3 are the fastening holes described above. Although not shown, the flange portion 122 of the upper mold 120 also has multiple fastening holes corresponding to the multiple holes 114 of the lower mold 110. Fastening may be performed by clamps rather than by inserting bolts into the fastening holes.

Figure 4 is an explanatory diagram showing a rotational molding method performed by a rotational molding device. First, the partition member 130 and molding materials m1 and m2 are set in the rotational molding die 100. Specifically, first, the first molding material m1 is poured into the inside of the lower die 110. Next, the pin hole 133 of the partition member 130 is inserted into the pin 113 for fixing the partition member material of the lower die 110, and the partition member 130 is temporarily fixed on the lower die 110. Next, the second molding material m2 is placed on the temporarily fixed partition member 130. Next, the pin hole 123 of the upper die 120 is inserted into the pin 113 for the mold alignment reference of the lower die 110, and the lower die 110 and the upper die 120 are aligned, and the flange portion 112 of the lower die 110 and the flange portion 122 of the upper die 120 are fastened. This creates the rotational molding die 100 in which the partition member 130 and molding materials m1 and m2 are set.

Next, the set rotational molding die 100 is rotated by the rotation device and heated by the heating device to perform rotational molding. The rotation speed, oscillation angle, and oscillation speed during the rotational motion are set to preset states.

In rotational molding, in the first stage, the first molding material m1 is welded to the inner surface of the lower mold 110 to form the surface layer PM1, and the second molding material m2 is welded to the inner surface of the upper mold 120 to form the surface layer PM2, and in the second stage, the partition member 130 is melted.

Here, the first heating temperature in the first stage of rotational molding is set to a temperature at which the partition member 130 does not melt, i.e., a temperature equal to or higher than the melting temperature of the molding materials m1 and m2 and lower than the melting temperature of the partition member 130. The second heating temperature in the second stage of rotational molding is set to a temperature at which the partition member 130 melts, i.e., an allowable temperature equal to or higher than the melting temperature of the partition member 130 and lower than the heat resistance temperature of the device. For example, the melting temperature of the molding materials m1 and m2 is 130°C, the melting temperature of the partition member 130 is 150°C, and the allowable temperature is 170°C. In this case, the first heating temperature can be set to a temperature equal to or higher than 130°C and lower than 150°C, and can be set to a constant temperature such as 130°C or 140°C. The second heating temperature can be set to a temperature equal to or higher than 150°C and lower than 170°C, and can be set to a constant temperature such as 150°C or 160°C. The first heating temperature may be set to change from the melting temperature of the molding material to the melting temperature of the partition member between the start and end of heating. The second heating temperature may be set to change from the melting temperature of the partition member to the allowable temperature between the start and end of heating, with the end of the first stage of heating being the start of the second stage of heating. For example, the first heating temperature may be set to change from 130°C to 150°C, and the second heating temperature may be set to change from 150°C to 170°C. The melting temperature and heating temperature of the molding material described above are examples and are not limited thereto. The melting temperature of the molding material changes depending on the melting temperature of the member used as the molding material. The heating temperature may be set appropriately depending on the melting temperature of the member used as the molding material. The heating temperature is preferably the temperature of the inner surface of the rotational molding die 100 on the side of the mold space 102 (see FIG. 1) with which the molding material comes into contact. However, this is not limited to this, and may be an indirect temperature that is correlated with the temperature of the inner surface of the rotational molding die 100, such as the temperature of the outer surface of the rotational molding die 100, the ambient temperature of the rotational molding die 100, the set temperature of the heating device, etc. In this case, the heating temperature may be set to a temperature that causes the temperature of the inner surface of the rotational molding die 100 to become the target temperature.

After the rotational molding is completed, the rotational molding die 100 is cooled, and then the rotational molding die 100 is opened to remove the molded product PM. This makes it possible to obtain a two-color molded hollow molded product PM having a first surface layer PM1 and a second surface layer PM2. The cooling can be performed, for example, by natural cooling while continuing the rotation of the die. It can also be performed using various cooling means such as water cooling. Note that the cooling is complete when the temperature falls below the softening temperature of the molding material.

Figure 5 is an explanatory diagram showing an enlarged view of the region Aeb of the molded product PM shown in Figure 4. The boundary portion of the partition member 130 between the first surface layer PM1 and the second surface layer PM2 of the molded product PM becomes a joint portion 130m by melting, and the first surface layer PM1 and the second surface layer PM2 are joined to each other, and become a part of the molded product PM and are integrated. In addition, the portion of the partition member 130 that partitioned the mold space 102 (see Figure 1) adheres to the inner surface of the molded product PM after melting, becoming an inner surface adhesion portion 130f. In addition, the portion 130b of the partition member 130 sandwiched between the lower mold 110 and the upper mold 120 may remain associated with the joint portion 130m. This remaining portion 130b is removed in a later process. It is preferable to provide a means for considering the appearance of the joint portion 130m, such as arranging other parts to hide the joint portion 130m.

As described above, in the rotational molding device of the first embodiment, the partition member 130 does not melt while the molding materials m1 and m2 are being welded, thereby maintaining the partition of the mold space 102, and it is possible to prevent the molding materials m1 and m2 from mixing with each other. This makes it possible to mold a hollow molded product PM having two-colored surface layers PM1 and PM2. This makes it possible to omit the painting process.

In addition, after molding the surface layers PM1 and PM2, the portion 130b of the partition member 130 that divides the mold space 102 can be melted to form the inner surface attachment portion 130f, making it unnecessary to recover the partition member 130 remaining in the hollow of the molded product PM.

As a result, the rotational molding of a hollow molded product PM having two colored surface layers PM1 and PM2 can be easily achieved while minimizing increases in the number of processes and costs.

In the rotational molding device of the above embodiment, a member having a melting temperature higher than the melting temperature of the molding materials m1 and m2 is used as the partition member 130. However, this is not limited to this, and as described below, a member having a melting temperature equal to the melting temperature of the molding materials m1 and m2 may be used as the partition member 130. In addition, when the melting temperatures of the molding materials are different, it is preferable that the melting temperature of the partition member is equal to or higher than the highest melting temperature.

The seal member 140 that sandwiches and fixes the partition member 130 is made of a material with a lower thermal conductivity than the metal material that constitutes the rotational molding die 100, so that the heat conduction to the partition member 130 can be delayed. As a result, even if a material having a melting temperature equal to the melting temperature of the molding materials m1 and m2 is used as the partition member 130, the seal member 140 prevents the temperature of the partition member 130 from rising to the melting temperature while the surface layers PM1 and PM2 are being molded, so that the molding materials m1 and m2 are not mixed in. In this case, the first heating temperature and the second heating temperature can be constant heating temperatures equal to or higher than the melting temperatures of the molding materials m1 and m2 and the partition member 130.

The delay in the temperature rise of the partition member 130 can be set, for example, by adjusting the thermal conductivity of the sealing member 140, the external dimensions such as width wh and height wv shown in FIG. 2, and the distance from the mold surface such as distances dh1, dh2, and dv. For example, the lower the thermal conductivity, the more the temperature rise can be delayed. Also, the larger the external dimensions, the more the temperature rise can be delayed. The smaller the distance from the mold surface, the more the temperature rise can be delayed.

In addition, if a member having a melting temperature higher than the melting temperature of the molding materials m1 and m2 is used as the partition member 130, the seal member 140 for sandwiching the partition member 130 is not necessarily required and can be omitted. In this case, however, a separate member for sealing the mold space 102 is required.

B. Second embodiment:
6 is an explanatory diagram showing a schematic configuration of a rotational molding device according to a second embodiment. The rotational molding device according to the second embodiment differs from the rotational molding device according to the first embodiment in that two partition members 130 are stacked and arranged with a space between them along a parting line PL between a lower mold 110 and an upper mold 120 of a rotational molding die 100.

The space between the two partition members 130 constitutes a space in which the molding material ms is placed, which is used to mold the layers that are laminated on the inner surfaces of the surface layers PM1 and PM2 that are formed from the molding materials m1 and m2. Various types of resin materials, such as foamed resin materials, can be used as the molding material ms.

The rotational molding die 100 shown in Figure 6 in which molding materials m1, m2, and ms are arranged is constructed by adding the step of placing molding material ms on a temporarily fixed first partition member 130 and temporarily fixing a second partition member 130 on top of it to the steps (see Figure 4) for constructing the rotational molding die 100 in which molding materials m1 and m2 of the first embodiment are arranged.

In rotational molding, in the first stage, the first molding material m1 is welded to the inner surface of the lower mold 110 to form the surface layer PM1, and the second molding material m2 is welded to the inner surface of the upper mold 120 to form the surface layer PM2. Then, in the second stage, the partition member 130 is melted and the molding material ms is welded to the inner surfaces of the surface layers PM1 and PM2 to form a layer PMs in which the molding material ms is laminated (hereinafter referred to as the "laminated layer").

Figure 7 is an explanatory diagram showing an enlarged portion of the molded product PMB molded by the rotational molding device of Figure 6. Like the molded product PM (see Figure 5), the molded product PMB is molded integrally by joining two colored surface layers PM1, PM2 to each other via a joint 130m. In addition, a laminate layer PMs made of molding material ms is molded on the hollow inner surface of the molded product PMB. Note that molten partition members 130 (not shown) are included at the boundaries between the laminate layer PMs and the surface layers PM1, PM2 and within the laminate layer PMs.

Here, the melting temperature of the molding material ms is preferably higher than the melting temperature of the partition member 130 and higher than the heating temperature (second heating temperature) when melting the partition member 130. In this case, after melting the partition member 130, it is necessary to increase the heating temperature to a temperature equal to or higher than the melting temperature of the molding material ms. Also, as described above, when the molding material ms is a foamable resin, it is necessary to increase the heating temperature to a temperature equal to or higher than the foaming temperature of the foaming material contained in the molding material ms.

In the rotational molding device of the second embodiment, as in the rotational molding device of the first embodiment, a hollow molded product PMB having two color surface layers PM1, PM2 can be molded. Also, as in the rotational molding device of the first embodiment, it is possible to eliminate the need to recover the partition member 130. Also, a laminate layer PMs of molding material ms can be molded on the hollow inner surface of the molded product PMB. Therefore, it is possible to simply realize the rotational molding of a molded product PMB having two color surface layers PM1, PM2 and a laminate layer PMs on the inner surface of the molded product PMB, while suppressing an increase in processes and costs.

The conditions described in the first embodiment, such as the melting temperature of the molding material, the melting temperature of the partition member, the dimensions of the sealing member, the heating temperature, and the type of molding material, can also be applied to the second embodiment.

C. Third embodiment:
8 is an explanatory diagram showing a schematic configuration of a rotational molding device as a third embodiment. The rotational molding die 100C used in the rotational molding device of the third embodiment is composed of a lower die 110 and an upper die 120 similar to the rotational molding die 100 of the first embodiment, and an intermediate die 110M arranged between the lower die 110 and the upper die 120. The lower die 110 and the intermediate die 110M are two mold parts separated along a first parting line PL1, and the intermediate die 110M and the upper die 120 are two mold parts separated along a second parting line PL2. The two parting lines PL1 and PL2 are parallel lines aligned along the direction in which the three mold parts are stacked.

The intermediate mold 110M has a mold structure portion 111M and flange portions 112ML, 112MU. The flange portion 112ML on the lower mold 110 side is a portion that is fastened to the flange portion 112 of the lower mold 110 when the lower mold 110 and the intermediate mold 110M are mold-matched. The flange portion 112MU on the upper mold 120 side is a portion that is fastened to the flange portion 122 of the upper mold 120 when the intermediate mold 110M and the upper mold 120 are mold-matched. The lower flange portion 112ML is provided with a pin hole 123 for mold matching into which a pin 113 for mold matching reference is inserted. The upper flange portion 112MU is provided with a pin 113 that is a pin for temporarily fixing the partition member 130 and is also a pin for mold matching reference for the upper mold 120.

Between the divided lower mold 110 and intermediate mold 110M, a partition member 130 arranged along the first parting line PL1 is sandwiched and fixed between the lower mold 110 and intermediate mold 110M via a seal member 140. Also, between the divided intermediate mold 110M and upper mold 120, a partition member 130 arranged along the second parting line PL2 is sandwiched and fixed between the intermediate mold 110M and upper mold 120 via a seal member 140. The two partition members 130 arranged in parallel are members that partition the mold space 102 into three mold space portions 102L, 102M, and 102U along the direction in which the three mold portions are stacked. The mold space portion 102L of the lower mold 110 is the portion where the first molding material m1 is placed during rotational molding, the mold space portion 102U of the upper mold 120 is the portion where the second molding material m2 is placed during rotational molding, and the mold space portion 102M of the intermediate mold 110M is the portion where the third molding material m3 is placed during rotational molding. The molding materials m1, m2, and m3 are made of the same type of thermoplastic resin material but different colors.

The rotational molding die 100C shown in FIG. 8 in which the two partition members 130 and molding materials m1, m2, and m3 are set can be constructed by the following procedure. The first molding material m1 is poured into the lower die 110, and the first partition member 130 is temporarily fixed on the lower die 110. The third molding material m3 is placed on the temporarily fixed partition member 130, and the intermediate die 110M is molded and fastened on top of it. The second partition member 130 is temporarily fixed on the molded intermediate die 110M. The second molding material m2 is placed on the temporarily fixed partition member 130, and the upper die 120 is molded and fastened on top of it. In this way, the rotational molding die 100C in which the two partition members 130 and molding materials m1, m2, and m3 are set can be constructed.

In rotational molding, in the first stage, the first molding material m1 is welded to the inner surface of the lower mold 110 to form the surface layer PM1, the second molding material m2 is welded to the inner surface of the upper mold 120 to form the surface layer PM2, the third molding material m3 is welded to the inner surface of the intermediate mold 110M to form the surface layer PM3, and in the second stage, the partition member 130 is melted. Note that the first heating temperature in the first stage of rotational molding and the second heating temperature in the second stage of rotational molding may be set in the same manner as in the first embodiment.

Figure 9 is an explanatory diagram showing a molded product PMC molded by the rotational molding device of Figure 8. The molded product PMC is molded integrally by bonding three colored surface layers PM1, PM2, and PM3 to each other via bonding portion 130m. In addition, an inner surface attachment portion 130f is formed on the hollow inner surface of the molded product PMC, where the partition member 130 is melted and attached.

As described above, the rotational molding device of the third embodiment can mold a hollow molded product PMC having three colored surface layers PM1, PM2, and PM3. This makes it possible to omit the painting process. It is also possible to eliminate the need to recover the partition member 130 remaining inside the hollow of the molded product PMC. Therefore, it is possible to simply mold a hollow molded product PMC having three colored surface layers PM1, PM2, and PM3 by rotational molding while suppressing increases in processes and costs.

Although the rotational molding device using the above-mentioned rotational molding die 100C has been described as an example of molding a molded product PMC having three colored surface layers PM1, PM2, and PM3, the present invention is not limited to this. For example, it is also possible to mold a molded product with three surface devices having one surface layer of one color and two surface layers of the other color alternately. It is also possible to mold a molded product having surface layers of four or more colors. In other words, it is also possible to mold a molded product having multiple surface layers of two or more colors. When molding multiple surface layers, an intermediate mold may be provided between the upper mold and the lower mold according to the increasing number of surface layers.

The conditions described in the first embodiment, such as the melting temperature of the molding material, the melting temperature of the partition member, the dimensions of the sealing member, the heating temperature, etc., can also be applied to the third embodiment.

D. Other embodiments:
(D1) The rotational molding device of the first embodiment is described as an example of molding two-color surface layers PM1 and PM2 using two different color molding materials m1 and m2. However, this is not limited to this, and it is also possible to mold different types of surface layers using different types of molding materials. For example, it is possible to mold a hard surface layer and a soft surface layer using a hard material and a soft material that have good compatibility for bonding, such as general-purpose resin PP and elastomer resin TPO, or general-purpose resin ABS and elastomer resin TPC and TPU. It is also possible to mold an opaque surface layer and a transparent surface layer using an opaque material and a transparent material that have good compatibility for bonding, such as general-purpose resin ABS and general-purpose resin PC and PMMA. It is also possible to mold a transparent surface layer and a soft surface layer using a transparent material and a soft material that have good compatibility for bonding, such as general-purpose resin PC and elastomer resin TPC and TPU.

Similarly, in the rotational molding device of the third embodiment described above, it is also possible to mold multiple surface layers using multiple different types of molding materials.

The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features of the embodiments corresponding to the technical features in each form described in the Summary of the Invention column can be replaced or combined as appropriate to solve some or all of the above-described problems or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

100, 100C...rotational molding die, 102...mold space, 102L...mold space portion, 102M...mold space portion, 102U...mold space portion, 110...lower die, 111...mold structure portion, 112...flange portion, 110M...intermediate die, 111M...mold structure portion, 112ML...flange portion, 112MU...flange portion, 113...pin, 114...hole, 120...upper die, 121...mold structure portion, 122... Flange part, 123... Pin hole, 130... Partition member, 130b... Remaining part, 130f... Inner surface attachment part, 130m... Joint part, 133... Pin hole, 140... Seal member, Aea... Area, Aeb... Area, PL, PL1, PL2... Mold parting line, PM, PMB, PMC... Molded product, PM1, PM2, PM3... Surface layer, PMs... Lamination Layer, m1, m2, m3...molding material, ms...molding material

Claims (4)

A rotational molding apparatus for molding a hollow molded product having a plurality of surface layers, comprising:
a rotational molding die having a plurality of mold sections separated along a parting line;
a partition member disposed between the mold parts on both sides of the parting line and partitioning the mold space of the rotational molding die into mold space portions corresponding to the mold parts on both sides,
a heating device for heating the rotational molding die in rotational molding for melting a molding material placed in the mold space;
Equipped with
the partition member is a member having a melting temperature equal to or higher than the melting temperature of the molding material ,
The heating device includes:
In the first rotational molding step, the molding material is heated at a first heating temperature that is equal to or higher than the melting temperature of the molding material and lower than the melting temperature of the partition member;
A rotational molding apparatus , in a second stage of rotational molding after the first stage of rotational molding, heating at a second heating temperature that is a temperature equal to or higher than the melting temperature of the partition member . 2. The rotational molding apparatus of claim 1, further comprising:
A rotational molding apparatus comprising a fixing member that sandwiches and fixes the partition member between the mold portions on both sides, the fixing member having a lower thermal conductivity than the rotational molding die. 3. A rotational molding apparatus according to claim 1 or 2 ,
The two partition members are stacked and arranged with a space between them between the mold parts on both sides,
The space between the two partition members is a space in which a molding material used to mold a layer to be laminated on the inner surface of the surface layer molded by the molding material is disposed.
Rotational molding equipment. A rotational molding method for forming a hollow molded article having a plurality of surface layers, comprising the steps of:
A process of placing molding materials in the mold space portions partitioned by the partition members when inserting the partition members between the mold portions on both sides of the parting line of the rotational molding die, the partition members dividing the mold space of the rotational molding die into mold space portions corresponding to the mold portions on both sides;
heating the rotational molding die at a heating temperature equal to or higher than the melting temperature of the molding material, which is set for melting the molding material in rotational molding, to melt the molding material arranged in the mold space without melting a partition member having a melting temperature equal to or higher than the heating temperature, and then melting the partition member;
A rotational molding method comprising:

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