Foam molded article production device, foam molded article production method, and foam molded article

Abstract

Provided is a foam molded article production device capable of providing a high expansion ratio. The foam molded article production device produces a foam molded article having a bottom surface and an upright wall structure around the bottom surface, and comprises: a mold including a fixed mold, a first movable mold, and a second movable mold and forming, when clamped, a cavity corresponding to the foam molded article, the cavity including a bottom surface cavity corresponding to the bottom surface between the fixed mold, the first movable mold, and the second movable mold, and an upright wall cavity corresponding to the upright wall structure between the first movable mold and the second movable mold, the second movable mold being capable of performing core-back so as to expand the bottom surface cavity; a foam resin injection unit capable of injecting a foam resin in which a molding resin and a high-pressure gas are mixed into the cavity to fill the cavity with the foam resin; a core-back drive unit for causing the second movable mold to perform core-back to further foam the foam resin with which the bottom surface cavity has been filled, thereby forming the foam molded article; and a mold drive unit for performing the clamping and opening of the fixed mold, the first movable mold, and the second movable mold.

Description

Manufacturing apparatus for foam-molded products, manufacturing method for foam-molded products, and foam-molded products

[0001] The present disclosure relates to an apparatus for manufacturing a foam-molded product with a high expansion ratio, a method for manufacturing a foam-molded product, and a foam-molded product.

[0002] In recent years, there has been an increasing need for lighter, stronger, and lower cost parts in the fields of home appliances, automotive interiors, etc. Among these, foam molded products are being actively adopted in various fields to meet the demand for lighter weight, higher strength, and lower cost.

[0003] 8 is a cross-sectional view showing a configuration in which double-sided tape 21 is attached to a vehicle body 20 to form an automotive member 10, as disclosed in Patent Document 1. According to the configuration described in Patent Document 1, grooves 14 recessed inward from the vehicle body side surface are formed in a position near the terminal of at least a portion of terminal peripheral region 13 of outer peripheral edge 12 so as to roughly follow outer peripheral edge 12, so that surface 15n of terminal peripheral region 13 on the vehicle body side, which is outward from groove 14, and surface 15m of terminal peripheral region 13 on the vehicle body side, which is inward from groove 14, are formed to be roughly flush with each other, and terminal 16 of terminal peripheral region 13 is formed in a roughly arc shape from outer surface 17 to outer peripheral edge 12 at the tip of surface 15n on the vehicle body side.

[0004] Japanese Patent Application Laid-Open No. 2020-006527

[0005] In this conventional example, double-sided tape 21 is applied to a vehicle body 20, and an automotive component 10 is formed on top of the tape. However, because groove 14 is formed between surface 15n of the terminal peripheral region and surface 15m of the terminal peripheral region so as to roughly follow outer periphery 12, high expansion ratio molding (2x or more) is not possible, and the presence of groove 14 reduces the thickness and strength of the component.

[0006] The present disclosure is intended to solve the above-mentioned problems, and has an object to provide an apparatus for manufacturing foam-molded products that can achieve a high expansion ratio.

[0007] The foam-molded product manufacturing apparatus according to the present disclosure is an apparatus for manufacturing foam-molded products that manufactures foam-molded products having a bottom surface and a standing-wall structure surrounding the bottom surface, the apparatus comprising a mold comprising a fixed mold, a first movable mold, and a second movable mold, and when the mold is clamped, a cavity corresponding to the foam-molded product is formed, including a bottom cavity corresponding to the bottom surface between the fixed mold, the first movable mold, and the second movable mold, and a standing-wall cavity corresponding to the standing-wall structure between the first movable mold and the second movable mold, the second movable mold being capable of core-backing to expand the bottom cavity, a foam-molded resin injection unit that can inject a foam-molded resin that is a mixture of molding resin and high-pressure gas into the cavity to fill the cavity with the foam-molded resin, a core-back drive unit that cores back the second movable mold to further foam the foam-molded resin filled in the bottom cavity to produce the foam-molded product, and a mold drive unit that clamps and opens the fixed mold, the first movable mold, and the second movable mold.

[0008] The method for manufacturing a foam-molded product according to the present disclosure is a method for manufacturing a foam-molded product that produces a foam-molded product having a bottom surface and a standing wall structure surrounding the bottom surface, and includes a mold clamping process in which a fixed mold, a first movable mold, and a second movable mold are clamped together to form a cavity corresponding to the foam-molded product, including a bottom cavity corresponding to the bottom surface between the fixed mold, the first movable mold, and the second movable mold, and a standing wall cavity corresponding to the standing wall structure between the first movable mold and the second movable mold; an injection process in which a foaming resin that is a mixture of molding resin and high-pressure gas is injected into the cavity to fill the cavity with the foaming resin; a core-back process in which the second movable mold is cored back to further foam the foaming resin filled in the bottom cavity to produce the foam-molded product; and a mold-opening process in which the fixed mold, the first movable mold, and the second movable mold are opened to remove the foam-molded product.

[0009] The foam-molded product according to the present disclosure has a bottom surface and a standing wall structure surrounding the bottom surface, with the bottom surface and the standing wall structure defining a recess, and the bottom surface has a lower density than the standing wall structure.

[0010] The foam-molded product manufacturing device according to the present disclosure can conform to the shape of the mold, enabling high expansion ratio molding (2x or more).

[0011] 1 is a schematic cross-sectional view showing a state in which the fixed mold, the first movable mold, and the second movable mold are clamped together in the method for manufacturing a foam-molded product according to the first embodiment. FIG. 1 is a schematic cross-sectional view showing a state in which foaming resin has been injected into the cavity after mold clamping in the method for manufacturing a foam-molded product according to the first embodiment. FIG. 1 is a schematic cross-sectional view showing a state in which the second movable mold is being cored back while maintaining the outer peripheral wall surface around the bottom of the molded product in the method for manufacturing a foam-molded product according to the first embodiment. FIG. 1 is a schematic cross-sectional view showing a state in which the core-back of the second movable mold has been completed in the method for manufacturing a foam-molded product according to the first embodiment. FIG. 1 is a schematic cross-sectional view showing a state in which the mold-opening operation is being performed in the method for manufacturing a foam-molded product according to the first embodiment. FIG. 1 is a schematic cross-sectional view showing a mold-closing operation of the fixed mold, the first movable mold, and the second movable mold in the method for manufacturing a foam-molded product according to the first embodiment. FIG. 2 is a timing chart for the method for manufacturing a foam-molded product according to the first embodiment. FIG. 2 is a schematic cross-sectional view showing a state in which H&C (heat and cool) units are arranged in the fixed mold and the first movable mold in the manufacturing apparatus for a foam-molded product according to the first embodiment. 5-B is a schematic cross-sectional view showing a plurality of second movable parts capable of core-backing. FIG. 5-C is a schematic cross-sectional view showing a state of the corner of the corner of FIG. 5-A after core-backing. FIG. 5-D is a schematic cross-sectional view showing a state of the corner of the corner of FIG. 5-C after core-backing. FIG. 5-E is a schematic cross-sectional view showing a state of the corner of the corner of FIG. 5-E after core-backing. FIG. 5-F is a schematic cross-sectional view showing a state of the corner of the corner of FIG. 5-E after core-backing. FIG. 5-G is a schematic cross-sectional view showing a state of the corner of the corner of FIG. 5-E after core-backing. FIG. 5-H is a schematic cross-sectional view showing a cycle of physical foam molding according to the first embodiment and an operation for releasing the mold clamping force before core-backing. FIG. 5-H is a table showing the time for releasing the mold clamping force and the core-back transition time required for a mold opening amount of 2 mm in the method for producing a foam-molded product according to the first embodiment.9 is a diagram showing the relationship between the core-back transition time, including the time for releasing the mold clamping force, and the mold opening amount in the manufacturing method for a foam-molded product according to Embodiment 1. FIG. 1 is a cross-sectional view showing the cross-sectional structure of an automobile part of Patent Document 1. FIG. 2 is a schematic plan view showing a toilet seat as a foam-molded product. FIG. 3 is a schematic cross-sectional view showing the cross-sectional structure before core-backing, as seen in the A-A direction of FIG. 9. FIG. 4 is a schematic cross-sectional view showing the cross-sectional structure after core-backing, as seen in the A-A direction of FIG. 9. FIG. 5 is a schematic plan view showing three measurement points for the glossiness of a toilet seat in an example.

[0012] The foam-molded product manufacturing apparatus of the first aspect is an apparatus for manufacturing foam-molded products that manufactures foam-molded products having a bottom surface and a standing-wall structure surrounding the bottom surface, and is a mold comprising a fixed mold, a first movable mold, and a second movable mold, and when the mold is clamped, a cavity corresponding to the foam-molded product is formed, including a bottom cavity corresponding to the bottom surface between the fixed mold, the first movable mold, and the second movable mold, and a standing-wall cavity corresponding to the standing-wall structure between the first movable mold and the second movable mold, and the second movable mold is configured as the second movable mold. The second movable mold is configured as a mold that can be cored back to expand the bottom cavity, a foaming resin injection unit that can inject a foaming resin that is a mixture of molding resin and high-pressure gas into the cavity and fill the cavity with the foaming resin, a core-back drive unit that cores back the second movable mold to further foam the foaming resin filled in the bottom cavity to produce the foam-molded product, and a mold drive unit that clamps and opens the fixed mold, the first movable mold, and the second movable mold.

[0013] The second aspect of the manufacturing apparatus for foam-molded products is the same as the first aspect, in that the bottom cavity formed between the fixed mold and the first movable mold and the second movable mold may have a larger radius of curvature on the inner side formed between the fixed mold and the second movable mold than the radius of curvature on the outer side formed between the fixed mold and the first movable mold.

[0014] The third aspect of the manufacturing apparatus for foam-molded products is the same as the first aspect, in which the bottom cavity formed between the fixed mold and the first movable mold and the second movable mold has a chamfered C-surface on the outer surface side formed between the fixed mold and the first movable mold and on the inner surface side formed between the fixed mold and the second movable mold, and the amount of chamfering of the C-surface on the inner surface side may be greater than the amount of chamfering of the C-surface on the outer surface side.

[0015] The foam-molded product manufacturing apparatus according to the fourth aspect may be any one of the first to third aspects, wherein the thickness W of the upright wall cavity relative to the average thickness t of the bottom cavity is 0.5t to 1.5t.

[0016] The apparatus for producing a foam-molded product according to a fifth aspect is any one of the first to fourth aspects, wherein the second movable mold may have a plurality of second movable molds that can independently perform core back.

[0017] The method for manufacturing a foam-molded product according to the sixth aspect is a method for manufacturing a foam-molded product that produces a foam-molded product having a bottom surface and a standing wall structure surrounding the bottom surface, and includes a mold clamping process in which a fixed mold, a first movable mold, and a second movable mold are clamped together to form a cavity corresponding to the foam-molded product, including a bottom cavity corresponding to the bottom surface between the fixed mold, the first movable mold, and the second movable mold, and a standing wall cavity corresponding to the standing wall structure between the first movable mold and the second movable mold; an injection process in which a foaming resin that is a mixture of molding resin and high-pressure gas is injected into the cavity to fill the cavity with the foaming resin; a core-back process in which the second movable mold is cored back to further foam the foaming resin filled in the bottom cavity to produce the foam-molded product; and a mold-opening process in which the fixed mold, the first movable mold, and the second movable mold are opened to remove the foam-molded product.

[0018] The seventh aspect of the method for manufacturing a foam-molded product is the same as the sixth aspect, wherein the bottom cavity formed between the fixed mold and the first movable mold and the second movable mold may have a larger radius of curvature on the inner side formed between the fixed mold and the second movable mold than the radius of curvature on the outer side formed between the fixed mold and the first movable mold.

[0019] The eighth aspect of the method for manufacturing a foam-molded product is the same as the sixth aspect, except that the bottom cavity formed between the fixed mold and the first movable mold and the second movable mold has a chamfered C-surface on both the outer surface side formed between the fixed mold and the first movable mold and the inner surface side formed between the fixed mold and the second movable mold, and the amount of chamfering of the C-surface on the inner surface side may be greater than the amount of chamfering of the C-surface on the outer surface side.

[0020] The method for producing a foam-molded product according to the ninth aspect may be any of the sixth to eighth aspects, wherein the thickness W of the upright wall cavity relative to the average thickness t of the bottom cavity in the mold clamping step prior to the core-back step is 0.5t to 1.5t.

[0021] A tenth aspect of the method for producing a foam-molded article is any one of the sixth to ninth aspects, wherein the second movable mold may have a plurality of second movable molds that can be independently cored back.

[0022] The foam-molded product according to the eleventh aspect has a bottom surface and a standing wall structure surrounding the bottom surface, and the bottom surface and the standing wall structure form a recess, and the bottom surface has a lower density than the standing wall structure.

[0023] A foam-molded article according to a twelfth aspect is the foam-molded article according to the eleventh aspect, wherein the density of the bottom surface may be half or less than that of the upright wall structure.

[0024] The manufacturing apparatus for foam-molded products according to the thirteenth aspect may further include a mold temperature control unit (H&C) that controls the surface temperature of at least one of the fixed mold, the first movable mold, and the second movable mold in the first aspect.

[0025] The apparatus for producing a foam-molded product according to a fourteenth aspect may be the first aspect, wherein the foaming resin injection section controls the holding pressure in the cavity within the mold.

[0026] The fifteenth aspect of the manufacturing apparatus for foam-molded products may be such that, in the first aspect described above, the surface temperature of at least one of the fixed mold, the first movable mold, and the second movable mold may be set to a temperature exceeding the Tg point (glass transition point) of the foamed resin during the injection process.

[0027] The method for producing a foam-molded product according to the sixteenth aspect may be any of the sixth to ninth aspects, in which the second movable mold is cored back in the core-back process and cooling of at least one surface of the fixed mold, the first movable mold, and the second movable mold is initiated.

[0028] A seventeenth aspect of the method for producing an expansion-molded article is any one of the sixth to ninth and sixteenth aspects, wherein after the injection step, the pressure in the cavity within the mold may be maintained at a predetermined pressure for a predetermined time.

[0029] The method for producing a foam-molded product according to the eighteenth aspect may be any of the sixth to ninth and seventeenth aspects, in which, after the injection step, cooling of at least one surface of the fixed mold, the first movable mold and the second movable mold is initiated, and the pressure in the cavity within the mold may be maintained at a predetermined pressure for a predetermined time.

[0030] A foam-molded article according to a nineteenth aspect may be the foam-molded article of the eleventh or twelfth aspect, wherein the foam-molded article has a glossiness of 50% or more.

[0031] A foam-molded article according to a twentieth aspect may be the foam-molded article of the eleventh, twelfth, or nineteenth aspect, wherein the foam-molded article has an expansion ratio of 2 or more.

[0032] The foam-molded article according to the 21st aspect may be any of the foam-molded articles according to the 11th, 12th, 19th, and 20th aspects, and may have a surface-side skin layer facing the surface side, a back-side skin layer facing the back side, and a foam layer between the surface-side skin layer and the back-side skin layer.

[0033] The foam-molded article according to the 22nd aspect is any one of the 11th, 12th, and 19th to 21st aspects, wherein the foam-molded article comprises at least one selected from the group consisting of acrylic (PMMA), polypropylene (PP), polycarbonate (PC), and acrylonitrile butadiene styrene (ABS).

[0034] A toilet seat according to a twenty-third aspect is made of the foam-molded article according to any one of the eleventh, twelfth, nineteenth to twenty-second aspects.

[0035] Hereinafter, a manufacturing apparatus for a foam-molded product, a manufacturing method thereof, and a foam-molded product according to embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0036] 1-A to 1-F are schematic cross-sectional views showing the operation of a foam-molded product manufacturing apparatus 200. The foam-molded product manufacturing apparatus 200 according to the first embodiment includes a fixed mold 201, a first movable mold 202, a second movable mold 203, an H&C (heat & cool) 204, and a hydraulic cylinder 205. The fixed mold 201, the first movable mold 202, and the second movable mold 203 form a mold. A mold driver closes and opens the fixed mold 201, the first movable mold 202, and the second movable mold 203. When the mold is clamped, a cavity 220 corresponding to the foam-molded product is defined between the fixed mold 201, the first movable mold 202, and the second movable mold 203. The cavity 220 includes a bottom cavity 216 corresponding to the bottom surface, and a standing-wall cavity 218 corresponding to the standing-wall structure, between the first movable mold 202 and the second movable mold 203. The second movable mold 203 can be cored back to expand the bottom cavity 216. The second movable mold 203 also has a foaming resin injection unit (not shown) that injects a foaming resin, which is a mixture of molding resin and high-pressure gas, into the cavity 220. The foaming resin injection unit can fill the cavity with the foaming resin. The core-back drive unit cores back the second movable mold 203, further foaming the foaming resin filled in the bottom cavity 216 to produce a foam-molded product.

[0037] <Regarding Corner C Before Core-Backing> FIG. 5-A is a schematic cross-sectional view showing the state of corner C when the corner on the fixed mold (cavity mold) 201 side before core-backing and the corner on the second movable mold (core mold) 203 side are both right angles. FIG. 5-B is a schematic cross-sectional view showing the state of corner C in FIG. 5-A after core-backing. As shown in FIG. 5-A , at the interface between the foamed resin 206 and the mold, a core-side skin layer 212 is formed on the second movable mold (core mold) 203 side, and a cavity-side skin layer 213 is formed on the fixed mold (cavity mold) 201 side. Core-backing of the second movable mold 203 further expands the foamed resin in the bottom cavity. In this case, since the foamed resin 206 expands inside the core-side skin layer 212, as shown in FIG. 5-B , the higher the expansion ratio (2 times or more) of the core-side skin layer 212 during core-backing, the more the skin layer stretches and becomes excessive. The inventors have discovered that if the core-side corner is a right angle before core backing, a groove 214 is formed in the excess part of the core-side skin 212, and sufficient foaming does not occur, resulting in a thin area, which may lead to a decrease in strength.

[0038] Fig. 5-C is a schematic cross-sectional view showing a state in which a rounded corner is provided before the core is backed. Fig. 5-D is a schematic cross-sectional view showing the state of the corner of Fig. 5-C after the core is backed. Specifically, in Fig. 5-C, a cavity-side corner R208 and a core-side corner R209 are provided at the corner. The radius of curvature of the cavity-side corner R208 is １ The radius of curvature R of the corner R209 closer to the core ２ (R １ <R ２ The inventors discovered that the above problem can be solved by making the core-side corner curved rather than right-angled, shortening the line length of the core-side skin layer compared to when the corner is right-angled, and increasing the radius of curvature compared to the cavity-side corner, leading to the present disclosure. This allows slack in the core-side skin layer 212 to be absorbed when the foaming resin is further expanded during core-back. As a result, the corner shape after core-back is as shown in Figure 5-D.

[0039] FIG. 5-E is a schematic cross-sectional view showing a state in which a C-face is provided at the corner before core backing. FIG. 5-F is a schematic cross-sectional view showing the state of the corner of FIG. 5-E after core backing. As shown in FIG. 5-E, by making the core-side corner of the corner a C-face rather than a right angle, it is possible to further shorten the line length of the core-side skin layer 212 compared to FIG. 5-C. Furthermore, after core backing, slack in the core-side skin layer 212 can be absorbed during further foaming of the foaming resin during core backing. As a result, the corner shape shown in FIG. 5-F is obtained.

[0040] As described above, the bottom cavity formed between the fixed mold 201, the first movable mold 202, and the second movable mold 203 may have a larger radius of curvature on the inner surface side formed between the fixed mold 201 and the second movable mold 203 than on the outer surface side formed between the fixed mold 201 and the first movable mold 202. Note that the inner surface side (core-side corner) formed between the fixed mold 201 and the second movable mold 203 and / or the outer surface side (cavity-side corner) formed between the fixed mold 201 and the first movable mold 202 are not limited to the curved surface shape shown in FIG. 5-C , and may also have a chamfered C-face as shown in FIG. 5-E . When the outer surface side formed between the fixed mold 201 and the first movable mold 202 and the inner surface side formed between the fixed mold 201 and the second movable mold 203 are each a chamfered C-face, the amount of C-face chamfering on the inner surface side may be larger than the amount of C-face chamfering on the outer surface side. Furthermore, when the inner surface (core side corner) and the outer surface (cavity side corner) have a mixture of curved and C-shaped surfaces, the curved surfaces can also be converted into "C-shaped chamfer amounts" and compared.

[0041] The wall thickness W of the vertical wall cavity 218 may be 0.5t to 1.5t relative to the average wall thickness t of the bottom cavity 216. As shown in Figure 4, it is recommended to set W in the range of 0.5t to 1.5t relative to the average wall thickness t before core back. If W is less than 0.5t, the vertical wall will deform during core back, and if the vertical wall thickness W is 1.5t or more, the vertical wall will be too thick, causing sink marks on the exterior surface. The height H should be set so that H is equal to or greater than the average wall thickness x expansion ratio.

[0042] <Second Movable Part> FIG. 3-3 is a schematic cross-sectional view showing a case where multiple second movable dies 203 (partial core-backs) that can be independently core-backed are provided. By core-backing the second movable parts 203, the foaming resin filled in the bottom cavity 216 can be further foamed inside the core-side skin layer 212, resulting in high-expansion foaming. In this case, the wall surface of the standing wall around the bottom surface can be maintained. The second movable die 203 may have multiple second movable dies that can be independently core-backed. Multiple second movable parts 203 can be used when it is desired to change the foaming ratio depending on the location.

[0043] <H&C (Heat & Cool)> The H&C 204 is in a state where the mold surface temperature has reached the maximum set temperature. The H&C 204 may be located only on the fixed mold 201, as shown in FIG. 1-A. However, this is not limited to this. The H&C 204 may be located on both the fixed mold 201 and the first movable mold 202, as shown in FIG. 3-1. Alternatively, the H&C 204 may be located on the fixed mold 201, the first movable mold 202, and the second movable mold 203, as shown in FIG. 3-2. The H&C placement can be determined according to the application. The upper temperature limit (Heat temperature setting) of the H&C 204 can be set to exceed the Tg point (glass transition temperature) of the material properties published by the molding resin manufacturer. The lower temperature limit (Cool temperature setting) can be set to the maximum recommended mold temperature published by the molding resin manufacturer. Setting the temperature below the maximum recommended mold temperature lengthens the heat cycle time, reducing mass productivity. Setting the temperature above the maximum temperature results in core-back without forming a skin layer, making the foam-molded product 207 prone to deformation. The hydraulic cylinder 205 is turned off during this process. Using the H&C 204, the temperature can be controlled all the way to the end, eliminating temperature variations and controlling the internal pressure to increase, allowing partial core-back to soften the skin layer on the surface of the foamed resin, allowing it to conform to the end shape. Alternatively, using the H&C 204, cooling may be initiated immediately after injection of the foamed resin, as shown in the timing chart of Figure 2. Alternatively, as described below, the cavity in the mold may be maintained at a high dwell pressure and maintained in a heated state for a predetermined period of time before core-back, and cooling may then be initiated simultaneously with core-back.

[0044] <Method of Manufacturing a Foam-Molded Product> FIGS. 1A to 1F are schematic cross-sectional views showing each step of the method of manufacturing a foam-molded product. FIG. 2 is a timing chart of the operation of the foam-molded product manufacturing apparatus (operation of the mold 200, injection, core-back), H&C (heat & cool) 204, and hydraulic cylinder 205 shown in FIGS. 1A to 1F. The method of manufacturing a foam-molded product according to the first embodiment involves a series of cycles: (1) mold clamping ( FIG. 1A ), (2) injection of foaming resin ( FIG. 1B ), (3) core-backing of the second movable mold ( FIG. 1C and FIG. 1D ), (4) mold opening ( FIG. 1E ), (5) removal of the foam-molded product ( FIG. 1F ), and (6) mold clamping. The foam-molded product 207 is a foam-molded product in which the foamed portion is surrounded by a skin layer.

[0045] (1) FIG. 1-A is a schematic cross-sectional view showing a state in which a fixed mold 201, a first movable mold 202, and a second movable mold 203 are clamped together in the manufacturing method for a foam-molded product according to the first embodiment. The cavity defined between the fixed mold 201, the first movable mold 202, and the second movable mold 203 includes a bottom cavity 216 corresponding to the bottom between the fixed mold 201, the first movable mold 202, and the second movable mold 203, and a standing-wall cavity 218 corresponding to the standing-wall structure between the first movable mold 202 and the second movable mold 203. As shown in FIG. 4 , the thickness W of the standing-wall cavity 218 is preferably set in the range of W = 0.5t to 1.5t, where t is the average wall thickness before core-back. If W is less than 0.5t, the standing wall will deform during core-back. If the standing-wall thickness W is greater than 1.5t, the standing wall will be too thick, resulting in sink marks on the exterior surface. The height H may be set to satisfy the following condition: H≧average wall thickness×expansion ratio.

[0046] (2) Figure 1-B is a schematic cross-sectional view showing the state in which foam resin 206 is injected into the cavity after mold clamping in the manufacturing method for a foam-molded product according to embodiment 1. <Foam Resin> Foam resin 206 is a molding resin mixed with high-pressure gas. Examples of molding resins include polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene (AS), polyamide (PA), polyacetal (POM), polylactic acid (PLA), polybutylene terephthalate (PBT), polyurethane (PU), polycarbonate (PC), polystyrene (PS), polyvinyl chloride (PVC), acrylic (PMMA), polyhydroxyalkanoate (PHA), polyphenylene sulfide (PPS), and nylon (PA6, PA66, etc.). Among these resins, acrylic (PMMA), polypropylene (PP), polycarbonate (PC), and acrylonitrile butadiene styrene (ABS) are preferred. Furthermore, alloys of the respective resins may be used. The molding resin is preferably contained in an amount of at least 50 wt % or more, more preferably 80 wt % or more, based on the total composition. In addition, nitrogen (N ２ ), carbon dioxide (CO ２ ) CO ２ Although N dissolves in a large amount in resin, the viscosity is easily reduced, and the foaming rate can be increased, the bubbles tend to become large in some places, making it difficult to achieve a good cross-section condition. ２ Although the amount of nitrogen (N) dissolved in the resin is small, the effect of viscosity reduction is low and it is easy to realize fine bubbles throughout the molded product. ２ ) is recommended.

[0047] At this time, the fixed mold 201, first movable mold 202, and second movable mold 203 are in a closed state, and the H&C 204 has reached its highest mold surface temperature, and the temperature is controlled all the way to the mold edge, resulting in a state with no temperature unevenness. After injection is complete, cooling begins in the H&C 204 and continues until mold opening begins. The hydraulic cylinder 205 only needs to be turned on hydraulically between the completion of mold clamping and before core back.

[0048] (3) Figure 1-C is a schematic cross-sectional view showing the second movable die being cored back while maintaining the outer peripheral wall surface around the bottom of the molded product in the manufacturing method for a foam-molded product according to embodiment 1. After the foam resin 206 is completely filled, a skin layer is formed and the molded product is softened. The second movable die 203 is cored back in the direction of the arrow while maintaining the outer peripheral wall surface of the molded product. At this time, the hydraulic cylinder 205 is turned on and turned off after the second movable die 203 is cored back. The H&C 204 continues cooling until mold opening begins. The cooling time is set to 100 seconds or more and 120 seconds or less. Setting the cooling time to 100 seconds or more can suppress deformation of the external surface, while setting it to 120 seconds or less can prevent one cycle from becoming too long, ensuring mass productivity. The core-back transition time of the second movable die 203 is preferably set to 3 seconds or more and 15 seconds or less. If the time is less than 3 seconds, the skin layer of the foamed resin 206 is stretched suddenly when the second movable mold 203 is cored back, causing cracks (tears) on the cavity side of the corners of the molded product. Furthermore, the skin layer is thin and soft if the time is less than 3 seconds, so the external surface is easily deformed. On the other hand, if the time is more than 15 seconds, the skin layer is formed first, resulting in insufficient foaming and preventing foaming to the required thickness.

[0049] During core-back transition, as shown in FIG. 6 , after the foaming resin is injected, a release operation of the mold clamping force occurs before the second movable mold 203 cores back. The operation time varies depending on the molding machine, but it takes a minimum of approximately 2 seconds. Therefore, it is desirable to set the time required for the release operation of the mold clamping force to the minimum. FIG. 7A is a table showing the release time of the mold clamping force and the core-back transition time required for a mold opening amount of 2 mm in the manufacturing method for a foam-molded product according to embodiment 1. FIG. 7B is a diagram showing the relationship between the core-back transition time, including the release time of the mold clamping force, and the mold opening amount in the manufacturing method for a foam-molded product according to embodiment 1. The vertical axis of FIG. 7B represents the mold opening amount (unit: mm), and the horizontal axis represents time (seconds (s)). For the first 2 seconds, a release operation of the mold clamping force (the mold opening amount remains 0) occurs as shown in FIG. 6 , and the mold opening amount remains 0 mm. As shown in FIG. 7B , after the release operation of the mold clamping force is completed, the second movable mold 203 cores back. The mold opening amount and core-back transition time are set taking into consideration the operation time required to release the mold clamping force.

[0050] (4) Figure 1-D is a schematic cross-sectional view showing the state in which core-backing of the second movable mold 203 is completed in the manufacturing method of a foam-molded product according to embodiment 1. The fixed mold 201 and the first movable mold 202 are in a closed state. The hydraulic pressure of the hydraulic cylinder 205 is turned off when core-backing is completed, and the H&C 204 is cooling to the set minimum temperature at this time, and continues cooling until mold opening begins.

[0051] (5) Figure 1-E is a schematic cross-sectional view showing the mold opening operation in the manufacturing method for foam-molded products according to embodiment 1. The hydraulic cylinder 205 is in the OFF state, and the hydraulic pressure is turned ON when mold opening is complete. The foam-molded product 207 is then ejected by an ejector pin, a core, or a stripper plate, and removed from the mold 200. At this point, the H&C 204 begins heating from the start of the mold opening operation, and heats up to the set maximum temperature.

[0052] (6) Figure 1-F is a schematic cross-sectional view showing the operation of closing the mold (closing the mold 200) after removing the foam-molded product 207 from the fixed mold 201, first movable mold 202, and second movable mold 203 in the manufacturing method for a foam-molded product according to embodiment 1. At this point, the H&C 204 continues heating until it reaches the set maximum temperature before the foam resin is injected. At this time, the hydraulic cylinder 205 is in the OFF state and remains OFF until mold clamping is complete. In this way, the high-expansion molded product 207 is molded.

[0053] <Foam-molded product> The foam-molded product 207 according to the first embodiment has a bottom surface and a standing wall structure surrounding the bottom surface, and the bottom surface and the standing wall structure define a recess. The bottom surface, which is foamed at a high expansion ratio by the core-back of the second movable mold 203, has a lower density than the standing wall structure in which the wall surface is maintained. The density of the bottom surface may be half or less than that of the standing wall structure.

[0054] The foam-molded product may have a glossiness of 50% or more. The glossiness may be measured, for example, according to JIS Z8741-1997 (ISO2813:1994). In this case, the angle of incidence from the light source to the surface to be measured may be any of 20°, 60°, or 85°, but may be measured, for example, at an angle of incidence of 60°. Measurement may also be performed using, for example, a glossmeter (manufactured by Nippon Denshoku Industries Co., Ltd.). The device is not limited to the above. The glossiness is expressed, for example, as the ratio (%) of the luminous flux of light reflected from the surface to be measured, assuming that the luminous flux of light reflected from a standard surface is 100%.

[0055] The foam-molded product may have an expansion ratio of 2 or more. Here, the "expansion ratio" is expressed as the ratio (%) or ratio of the wall thickness after core-back to the wall thickness before core-back. Specifically, it is expressed by the following formula: [Expansion ratio (%)] = ((Wall thickness after core-back) / (Wall thickness before core-back)) × 100 For example, if the wall thickness before core-back is 4 mm and the wall thickness after core-back is 6 mm, the expansion ratio is 150% (1.5 times), and if the wall thickness after core-back is 8 mm, the expansion ratio is 200% (2 times).

[0056] Furthermore, the foam-molded product may have, for example, a surface-side skin layer (cavity-side skin layer 213) facing the surface side, a back-side skin layer (core-side skin layer 212) facing the back side, and a foam layer between the surface-side skin layer and the back-side skin layer, as shown in Figure 5-A.

[0057] The foam-molded article may also contain at least one selected from the group consisting of acrylic (PMMA), polypropylene (PP), polycarbonate (PC), and acrylonitrile butadiene styrene (ABS).

[0058] Fig. 9 is a schematic plan view showing a toilet seat 30 as a foam-molded product. Fig. 10A is a schematic cross-sectional view showing the cross-sectional structure before core-backing, as viewed in the A-A direction in Fig. 9. Fig. 10B is a schematic cross-sectional view showing the cross-sectional structure after core-backing, as viewed in the A-A direction in Fig. 9. Furthermore, the foam-molded product may be a toilet seat 30 as shown in Fig. 9. As shown in Figs. 10A and 10B, the toilet seat 30 has a cross-sectional structure in which the bottom surface 34, which contacts the buttocks, is mainly foamed by the core-back. This provides strength to the bottom surface 34, and the foam structure also provides thermal insulation.

[0059] (Embodiment 2) The foam-molded product manufacturing apparatus according to Embodiment 2 differs from the foam-molded product manufacturing apparatus according to Embodiment 1 in that it includes a mold temperature control unit (H&C) 204 that controls the surface temperature of at least one of the fixed mold, first movable mold, and second movable mold. Furthermore, the holding pressure in the cavity within the mold may be controlled by a foaming resin injection unit. In the foam-molded product manufacturing apparatus according to Embodiment 2, after injection of the foaming resin and before core-backing of the second movable mold 203, the foaming resin injection unit maintains the holding pressure in the cavity 220 within the mold at a predetermined pressure for a predetermined period of time. After core-backing of the second movable mold 203, the mold temperature control unit (H&C) 204 may start cooling the surface of at least one of the fixed mold 201, first movable mold 202, and second movable mold 203. In the foam-molded product manufacturing apparatus according to Embodiment 2, cooling is not performed immediately after injection molding and before core-backing, but rather the holding pressure is maintained at a predetermined pressure for a predetermined period of time, thereby maintaining the dissolution of gas in the foaming resin during core-backing. This prevents the generation of gas that is no longer completely dissolved in the foamed resin when the foamed resin flows into the gaps created by the core-back. If the foamed resin is cooled immediately before core-backing, the gas dissolved in the foamed resin becomes insoluble before the foamed resin fully flows into the gaps created by the core-back, generating gas, which then solidifies upon cooling. In this case, foaming marks (swirl marks) due to unintended foaming may appear at the interface with the mold, resulting in poor appearance. Foaming marks are, for example, gas marks with streaky or spiral-like irregularities. According to the foam-molded product manufacturing apparatus of embodiment 2, before core-backing the second movable mold 203, a predetermined pressure is maintained for a predetermined time, and the mold temperature is maintained by the mold temperature control unit (H&C) 204. Therefore, when the foamed resin flows into the gaps created by the core-backing, the generation of gas due to the gas being no longer dissolved in the foamed resin can be prevented, thereby preventing the generation of foaming marks (swirl marks) due to unintended foaming. Alternatively, since the mold temperature is high when the foaming resin is injected, the swirl marks that were once formed are transferred to the mold by the mold pressure and disappear, resulting in high gloss.

[0060] The foaming resin injection unit can maintain a holding pressure of 10 MPa in the mold cavity for a period exceeding 0 seconds. The holding pressure is preferably 10 MPa or more and 150 MPa or less, more preferably 60 MPa or more and 80 MPa or less, and the holding time is preferably more than 0 seconds and 10 seconds or less, more preferably 5 seconds or more and 10 seconds or less.

[0061] Example: Figure 11 is a plan view schematic diagram showing three measurement points 38A, 38B, and 38C for the gloss of a toilet seat 30 in this example. Toilet seats as foam-molded products were manufactured under the following five conditions, Condition 1 to Condition 5, and evaluated. The common conditions were that the resin was acrylic (PMMA) and the temperature during injection was 255°C. The evaluation was performed by measuring the gloss at measurement points 38A, 38B, and 38C shown in Figure 11 using a gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS Z8741-1997 (ISO2813:1994). Measurement points 38A, 38B, and 38C were: measurement point 38A on the flat surface near gate mark 36; measurement point 38C on the flat surface farthest from gate mark 36; and measurement point 38B on the flat surface at the midpoint. The "flat area" was chosen because gloss measurement requires a flat surface for the light beam from the light source to enter and reflect. Three measurement locations were selected based on the distance from the gate. In other words, it takes approximately three seconds for the foam resin to be injected through the gate and fill up to the measurement location farthest from the gate. Therefore, filling is faster near the gate, and the dwell pressure tends to be high. On the other hand, at the measurement location farthest from the gate, sufficient dwell pressure is not achieved, which is thought to make gas more likely to be generated from the foam resin. At the measurement location at the midpoint, filling is slower than near the gate but faster than at the farthest measurement location, and the dwell pressure increase is intermediate between the two. Note that gloss measurements were performed at a 60° incident angle from the light source.

[0062] <Condition 1> Under Condition 1, toilet seats were fabricated using conventional injection molding, which does not dissolve gas in the resin. The manufacturing equipment was not equipped with a mold temperature control unit (H&C), nor a heater; only cooling was performed. The mold temperature was preferably 60°C to 130°C, more preferably 80°C to 100°C. The cavity pressure after completion of injection via speed control was preferably 10 MPa to 150 MPa, more preferably 60 MPa to 80 MPa, and the pressure retention time was preferably 0 seconds to 10 seconds, more preferably 5 seconds to 10 seconds. The thickness of the toilet seat bottom was 4 mm. In this case, the glossiness at measurement point 38A was 64.8%, the glossiness at measurement point 38B was 69.4%, and the glossiness at measurement point 38C was 66.2%.

[0063] <Condition 2> In condition 2, nitrogen gas N ２ The resin was melted at a gas pressure of 10 MPa to form a foamed resin, and the foamed resin was injected and foam-molded using a core back. The wall thickness before the core back was 4 mm, the wall thickness after the core back was 8 mm, and the expansion ratio was 200% (2 times). Note that the foamed resin conditions were the same under conditions 2 to 5. The manufacturing equipment was not equipped with a mold temperature control unit (H&C), nor was it equipped with a heater; only cooling was performed. The mold temperature was preferably 60°C or higher and 130°C or lower, and more preferably 80°C or higher and 100°C or lower. The pressure held in the cavity after the end of injection by speed control was preferably 10 MPa or higher and 150 MPa or lower, and more preferably 60 MPa or higher and 80 MPa or lower. The pressure holding time was preferably 0 seconds or higher and 10 seconds or lower, and more preferably 0.5 seconds or higher and 2 seconds or lower. In this case, the glossiness at measurement point 38A was 41.7%, the glossiness at measurement point 38B was 23.7%, and the glossiness at measurement point 38C was 20.0%.

[0064] <Condition 3> Condition 3 differs in that the manufacturing equipment is equipped with a mold temperature control unit (H&C). Specifically, in the injection process, after filling with the foaming resin, the mold temperature is preferably 150°C or higher and 250°C or lower, and more preferably 180°C or higher and 210°C or lower. Thereafter, the second movable mold is cored back and cooled to 90°C or lower. The other conditions are the same as those of condition 2. In this case, the glossiness at measurement point 38A was 55.2%, the glossiness at measurement point 38B was 31.4%, and the glossiness at measurement point 38C was 33.6%.

[0065] <Condition 4> Under Condition 4, after the injection process, the foaming resin is filled into the cavity in the mold by the foaming resin injection unit, and the dwell pressure is preferably 10 MPa or more and 150 MPa or less, more preferably 60 MPa or more and 80 MPa or less, and the dwell time is preferably more than 0 seconds and 10 seconds or less, more preferably 0.5 seconds or more and 2 seconds or less. This differs from Condition 4 in that the second movable mold is then cored back and cooling is initiated. The other conditions are the same as Condition 3. In this case, the glossiness at measurement point 38A was 61.3%, the glossiness at measurement point 38B was 52.7%, and the glossiness at measurement point 38C was 50.5%.

[0066] <Condition 5> In Condition 5, after the foaming resin is filled in the mold cavity during the injection process, the foaming resin injection unit applies a dwell pressure of 10 MPa or more and 150 MPa or less, preferably 60 MPa or more and 80 MPa or less, to the mold cavity, and the dwell time is preferably 0 seconds or more and 10 seconds or less, more preferably 0.5 seconds or more and 2 seconds or less. This condition differs from Condition 2 in that the second movable mold is then cored back and cooling is initiated. The other conditions are the same as Condition 2. In this case, the glossiness at measurement point 38A was 36.3%, the glossiness at measurement point 38B was 37.7%, and the glossiness at measurement point 38C was 37.1%.

[0067] Of the above, condition 1 is based on normal injection molding and is therefore considered for reference only. Comparing toilet seats under conditions 2 to 5, under conditions 2 and 5, gloss levels of less than 50% were obtained at all measurement points. Under condition 3, gloss levels of 50% or more were obtained only at measurement point 38A near gate mark 36, but all measurement points further away only achieved gloss levels of less than 50%. On the other hand, the toilet seat under condition 4 achieved gloss levels of 50% or more at all three measurement points.

[0068] As described above, under condition 4, after injection by speed control was completed, the mold temperature was maintained at 150°C or higher, a holding pressure of 60 MPa was maintained in the cavity within the mold for 1 second, and then the second movable mold was cored back and cooling was performed by the mold temperature control unit (H&C). This is thought to have prevented the gas dissolved in the foamed resin from dissolving and generating gas when the foamed resin flows into the gap created by the cored back, thereby preventing the occurrence of foam marks (swirl marks) due to unintended foaming and achieving a high gloss.

[0069] The foam-molded article according to the present disclosure contributes to weight reduction through high foaming ratio molding in the exteriors of various household electrical appliances, for example, toilet seats, and in the field of automotive applications.

[0070] DESCRIPTION OF SYMBOLS 200... Mold 201... Fixed mold 202... First movable mold 203... Second movable mold 204... H&C (heat & cool device) 205... Hydraulic cylinder 206... Foamed resin 207... Foam-molded product 208... Cavity side corner R 209... Core side corner R 210... Inside cavity 212... Core side skin layer 213... Cavity side skin layer 214 Groove 216 Bottom cavity 218 Standing wall cavity 220 Cavity W... Standing wall thickness t... Average thickness before core back H... Height 10... Automotive part 11... Foamed resin molded product 111... Foam portion 112... Skin portion 12... Outer periphery 13... Terminal peripheral region 14... Groove 15m, 15n... Surface of terminal peripheral region 16... Terminal 17... Outer surface 20... Vehicle body 21...Double-sided tape 30 Toilet seat 32 Standing wall 34 Bottom surface 36 Gate mark 38A, 38B, 38C Measurement points

Claims

1. A foam-molded product manufacturing apparatus for manufacturing a foam-molded product having a bottom surface and a standing-wall structure surrounding the bottom surface, comprising: a mold comprising a fixed mold, a first movable mold, and a second movable mold, which, when the mold is clamped, forms a cavity corresponding to the foam-molded product, including a bottom cavity corresponding to the bottom surface between the fixed mold, the first movable mold, and the second movable mold, and a standing-wall cavity corresponding to the standing-wall structure between the first movable mold and the second movable mold, and the second movable mold is capable of being cored back to enlarge the bottom cavity; a foaming resin injection unit that can inject a foaming resin that is a mixture of molding resin and high-pressure gas into the cavity and fill the cavity with the foaming resin; a core-back drive unit that cores back the second movable mold and further foams the foaming resin filled in the bottom cavity to produce a foam-molded product; and a mold drive unit that clamps and opens the fixed mold, the first movable mold, and the second movable mold.

2. The apparatus for manufacturing foam-molded products described in claim 1, wherein the bottom cavity formed between the fixed mold and the first movable mold and the second movable mold has a larger radius of curvature on the inner side formed between the fixed mold and the second movable mold than on the outer side formed between the fixed mold and the first movable mold.

3. The bottom cavity formed between the fixed mold and the first movable mold and the second movable mold has a chamfered C-surface on the outer surface side formed between the fixed mold and the first movable mold and on the inner surface side formed between the fixed mold and the second movable mold, and the amount of chamfering of the C-surface on the inner surface side is greater than the amount of chamfering of the C-surface on the outer surface side.

4. The foam-molded product manufacturing apparatus according to claim 1, wherein the average wall thickness W of the vertical wall cavity is 0.5t to 1.5t relative to the average wall thickness t of the bottom cavity.

5. The foam molding manufacturing apparatus according to claim 1, wherein the second movable mold has a plurality of second movable molds that can be independently cored back.

6. A method for manufacturing a foam-molded product for manufacturing a foam-molded product having a bottom surface and a standing wall structure surrounding the bottom surface, comprising: a mold clamping process in which a fixed mold, a first movable mold, and a second movable mold are clamped together to form a cavity corresponding to the foam-molded product, including a bottom cavity corresponding to the bottom surface between the fixed mold, the first movable mold, and the second movable mold, and a standing wall cavity corresponding to the standing wall structure between the first movable mold and the second movable mold; an injection process in which a foaming resin obtained by mixing molding resin and high-pressure gas is injected into the cavity to fill the cavity with the foaming resin; a core-back process in which the second movable mold is cored back to further foam the foaming resin filled in the bottom cavity to form a foam-molded product; and a mold-opening process in which the fixed mold, the first movable mold, and the second movable mold are opened to remove the foam-molded product.

7. A method for manufacturing a foam-molded product as described in claim 6, wherein the bottom cavity formed between the fixed mold and the first movable mold and the second movable mold has a larger radius of curvature on the inner side formed between the fixed mold and the second movable mold than on the outer side formed between the fixed mold and the first movable mold.

8. A method for manufacturing a foam-molded product as described in claim 6, wherein the bottom cavity formed between the fixed mold and the first movable mold and the second movable mold has a chamfered C-surface on the outer surface side formed between the fixed mold and the first movable mold and an inner surface side formed between the fixed mold and the second movable mold, and the amount of C-surface chamfering on the inner surface side is greater than the amount of C-surface chamfering on the outer surface side.

9. A method for producing a foam-molded product according to claim 6, wherein the average wall thickness W of the vertical wall cavity relative to the average wall thickness t of the bottom cavity in the mold clamping step prior to the core-back step is 0.5t to 1.5t.

10. The method for producing a foam-molded product according to claim 6, wherein the second movable mold has a plurality of second movable molds that can be independently cored back.

11. A foam-molded product having a bottom surface and a standing wall structure surrounding the bottom surface, the bottom surface and the standing wall structure forming a recess, wherein the bottom surface has a lower density than the standing wall structure.

12. The foam-molded product according to claim 11, wherein the bottom surface has a density that is half or less than that of the upstanding wall structure.

13. The apparatus for producing foam-molded products according to claim 1, further comprising a mold temperature control unit (H&C) for controlling the surface temperature of at least one of the fixed mold, the first movable mold, and the second movable mold.

14. The foam molding manufacturing device according to claim 1, wherein the foam resin injection section controls the holding pressure in the cavity within the mold.

15. A method for producing a foam-molded product according to claim 6, wherein in the injection step, the surface temperature of at least one of the fixed mold, the first movable mold and the second movable mold is set to a temperature exceeding the Tg point (glass transition point) of the foaming resin.

16. A method for producing a foam-molded product according to claim 6, wherein cooling of at least one surface of the fixed mold, the first movable mold, and the second movable mold is initiated while the second movable mold is cored back during the core-back process.

17. The method for producing a foam-molded product according to claim 6 or 16, wherein after the injection step, the pressure in the cavity within the mold is maintained at a predetermined pressure for a predetermined period of time.

18. A method for producing a foam-molded product as described in claim 6, wherein after the injection process, cooling of at least one surface of the fixed mold, the first movable mold, and the second movable mold is initiated, and the dwell pressure in the cavity within the mold is maintained at a predetermined pressure for a predetermined time.

19. The foam-molded product according to claim 11, wherein the foam-molded product has a gloss level of 50% or more.

20. The foam-molded product according to claim 11, wherein the foam-molded product has an expansion ratio of 2 or more.

21. The foam-molded product according to claim 11, having a surface-side skin layer facing the surface side, a back-side skin layer facing the back side, and a foam layer between the surface-side skin layer and the back-side skin layer.

22. The foam-molded article according to claim 11, wherein the foam-molded article comprises at least one selected from the group consisting of acrylic (PMMA), polypropylene (PP), polycarbonate (PC), and acrylonitrile butadiene styrene (ABS).

23. A toilet seat comprising the foam-molded product according to any one of claims 11, 12, 19 to 22.

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