Foam molded article, method for producing foam molded article, and method for suppressing appearance defects in foam molded article

Abstract

A foam molded body provided with a foam layer and a skin layer covering the foam layer, the foam molded body being characterized in that: the maximum diameter of air bubbles in the foam layer is 0.90 mm or less; a method for producing a foam molded article or a method for suppressing appearance defects, the method comprising an injection step and a foaming step, the foam molded article after molding being provided with a foam layer and a skin layer covering the foam layer, the skin layer having an average thickness of 0.3 mm to 0.7 mm, expanding the volume of the cavity includes withdrawing the mold such that the thickness of the foam molded body after molding is within + / -0.2 mm with respect to a preset target thickness.

Description

[0001] This invention is a divisional application of the invention application with application number 2020800665371, application date October 6, 2020, entitled "Foamed Molded Body, Method for Manufacturing Foamed Molded Body and Method for Suppressing Appearance Defects of Foamed Molded Body". Technical Field

[0002] This disclosure relates to a foamed molded body, a method for manufacturing the foamed molded body, and a method for suppressing appearance defects of the foamed molded body. Background Technology

[0003] From the perspective of being lightweight and having excellent rigidity, injection-molded parts of thermoplastic resins such as polypropylene resins and acrylonitrile-butadiene-styrene copolymers are used as automotive components.

[0004] One method of injection molding is the core-removal method. The core-removal method refers to a method in which a thermoplastic resin composition containing a foaming agent is injected into a mold, the thermoplastic resin composition is filled into the mold, and then the movable mold is slid to expand the cavity volume to obtain a molded article. If this molding method is used, the surface layer of the molded article becomes a non-foamed layer (skin layer), and the interior of the molded article becomes a foamed layer (see, for example, Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-121793 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] When injection-molded parts are used as automotive interior parts such as console boxes, door panels, deck side panels, rear door panels, and dashboards; and automotive exterior parts such as arched trim, door sills, and box trims, lightweight, thin-walled, and aesthetically pleasing injection-molded parts are desired.

[0010] However, small, round or oval depressions (sometimes called "pits") and linear marks (sometimes called "vortices") formed on the surface of injection-molded articles are easily produced, which can sometimes cause aesthetic problems. Pits are caused by air bubbles remaining on the resin surface and bursting during injection molding, while vortices are caused by the elongation of the burst portion of the air bubble due to resin flow.

[0011] In view of this situation, the present disclosure aims to provide a foamed molded article that suppresses appearance defects such as pits and vortices, a method for manufacturing a foamed molded article that can suppress appearance defects, and a method for suppressing appearance defects of the foamed molded article.

[0012] Methods for solving problems

[0013] The methods used to solve the above problems include the following approaches.

[0014] <1> A foamed molded body having a foamed layer and a skin layer covering the foamed layer, wherein the maximum diameter of the air bubbles in the foamed layer is less than or equal to 0.90 mm.

[0015] <2> According to <1> the foamed molded body, the average thickness of the above-mentioned skin layer is 0.3mm~0.7mm.

[0016] <3> According to <1> or <2>, the average diameter of the bubbles in the foamed layer is 0.02mm to 0.15mm.

[0017] <4> A method for manufacturing a foamed molded body, comprising:

[0018] The resin material is filled into the cavity of the mold by injecting it into the cavity; and

[0019] By increasing the volume of the cavity, the resin material filled into the cavity is foamed.

[0020] The molded foamed body comprises a foamed layer and a skin layer covering the foamed layer, wherein the average thickness of the skin layer is 0.3 mm to 0.7 mm.

[0021] Expanding the volume of the cavity includes: removing the mold core in such a way that the thickness of the formed foamed body is within ±0.2 mm of the pre-set target thickness.

[0022] <5> According to the manufacturing method of the foamed body described in <4>, the mold core is removed so that the thickness of the foamed body after molding is within ±0.2mm of the preset target thickness, thereby controlling the maximum diameter of the air bubbles in the foamed body after molding to be less than or equal to 0.90mm.

[0023] <6> According to the manufacturing method of the foamed molded body described in <4> or <5>, the average diameter of the bubbles in the foamed layer is 0.02mm to 0.15mm.

[0024] <7> A method for suppressing poor appearance of foamed molded articles, comprising:

[0025] The resin material is filled into the cavity of the mold by injecting it into the cavity; and

[0026] By increasing the volume of the cavity, the resin material filled into the cavity is foamed.

[0027] The molded foamed body comprises a foamed layer and a skin layer covering the foamed layer, wherein the average thickness of the skin layer is 0.3 mm to 0.7 mm.

[0028] Expanding the volume of the cavity includes: removing the mold core in such a way that the thickness of the formed foamed body is within ±0.2 mm of the pre-set target thickness.

[0029] <8> According to the method for suppressing poor appearance of the foamed molded body described in <7>, the maximum diameter of the air bubbles in the molded foamed body is controlled to be less than or equal to 0.90 mm by removing the mold core in such a way that the thickness of the foamed molded body is within ±0.2 mm relative to the target thickness.

[0030] <9> According to the method for suppressing poor appearance of foamed molded articles as described in <7> or <8>, the average diameter of the bubbles in the foamed layer is 0.02 mm to 0.15 mm.

[0031] Invention Effects

[0032] According to this disclosure, a foamed molded article with appearance defects such as pits and vortices is provided, a method for manufacturing a foamed molded article with appearance defects that can be suppressed, and a method for suppressing appearance defects of a foamed molded article. Attached Figure Description

[0033] Figure 1A This is a cross-sectional view showing a foamed molded body according to one embodiment of the present disclosure.

[0034] Figure 1B This is a cross-sectional view of a foamed molded body containing bubbles with a diameter exceeding 0.90 mm.

[0035] Figure 2 This is a schematic diagram illustrating a forming apparatus equipped with a mold.

[0036] Figure 3 This is a view showing the appearance and cross-section of the foamed molded body of Example 1.

[0037] Figure 4 This is a view showing the appearance and cross-section of the foamed molded body of Comparative Example 1. Detailed Implementation

[0038] The following describes in detail the methods for implementing the present invention. However, the present invention is not limited to the embodiments described below. In the embodiments described below, the constituent elements (including element steps, etc.) are not essential unless specifically stated otherwise. Similarly, numerical values ​​and their ranges are not intended to limit the present invention.

[0039] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that can be clearly distinguished from other processes if their purpose can be achieved.

[0040] In this disclosure, the numerical range represented by "~" includes the values ​​before and after "~" as the minimum and maximum values, respectively.

[0041] In the numerical ranges described in this disclosure, the upper or lower limit of one numerical range can be replaced by the upper or lower limit of another numerical range described in other stages. Furthermore, the upper or lower limit of the numerical ranges described in this disclosure can also be replaced by the values ​​shown in the embodiments.

[0042] In this disclosure, each component may also contain multiple substances equivalent to each component. When multiple substances equivalent to each component are present in the composition, unless otherwise specified, the content or percentage of each component refers to the total content or percentage of the multiple substances present in the composition.

[0043] In this disclosure, the term "layer" or "membrane" includes not only the case where it is formed in the entire region when observing the area where the layer or membrane is present, but also the case where it is formed only in a part of the region.

[0044] In this disclosure, while embodiments are described with reference to the accompanying drawings, the configuration of these embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative sizes of the components are not limited thereto. Additionally, in all drawings, components with substantially the same function are given the same reference numerals, and sometimes repeated descriptions are omitted.

[0045] Foamed Molded Bodies

[0046] The foamed molded body disclosed herein has a foamed layer and a skin layer covering the foamed layer, wherein the maximum diameter of the air bubbles in the foamed layer is less than or equal to 0.90 mm.

[0047] Regarding the issue of poor appearance in foamed molded articles, the inventors initially hypothesized that insufficient foaming during the foaming process caused these defects and conducted research. Generally, if foaming is insufficient in the core-removal method, the resin material cannot follow the mold, easily leading to poor appearance. However, they found the opposite: by controlling the foaming state and keeping the bubble size less than or equal to 0.90 mm, poor appearance could be suppressed. The reason is not entirely clear, but it can be inferred that if the bubble size in the foamed layer is relatively uniform, surface depressions can be suppressed.

[0048] Regarding the relationship between the maximum diameter of air bubbles in the foam layer and poor appearance, using Figure 1A and Figure 1B Please provide an explanation. Figure 1A A cross-sectional view showing a foamed molded body according to one embodiment of the present disclosure. Figure 1A In the foam layer, the maximum diameter of the air bubbles is less than or equal to 0.20 mm, and the average diameter of the air bubbles is 0.10 mm. Figure 1A In the foamed molded article shown, poor appearance is suppressed. On the other hand, Figure 1B This is a cross-sectional view of a foamed molded body containing bubbles with a diameter of 0.93 mm in the foam layer. Figure 1B The foamed molded body shown has depressions on its surface, resulting in poor appearance.

[0049] A foamed molded body comprises a foamed layer and a skin layer covering the foamed layer. The foamed layer is a layer formed by foaming resin material, and the skin layer is a layer formed by cooling and solidifying the resin material. The foamed layer is formed by foaming resin material filled into a mold, and the skin layer is a layer formed by cooling and solidifying resin material with a lower foaming rate than the foamed layer. The foamed molded body can also be manufactured by the foamed molded body manufacturing method described later.

[0050] The maximum diameter of the air bubbles in the foamed layer of the foamed molded article disclosed herein is less than or equal to 0.90 mm, preferably less than or equal to 0.50 mm, more preferably less than or equal to 0.40 mm, and even more preferably less than or equal to 0.20 mm. There is no particular limitation on the lower limit of the maximum bubble diameter; from the viewpoint of generating sufficient foam, the maximum bubble diameter can be greater than or equal to 0.02 mm, greater than or equal to 0.05 mm, or greater than or equal to 0.10 mm.

[0051] The maximum diameter of the air bubbles in the foamed molded body is set as the maximum major diameter when the foamed molded body is cut along the thickness direction using a 3D measuring machine (50x magnification). Here, the cross-section of the foamed molded body is the cross-section cut along the core-removal direction when the mold is removed during the foaming process described later.

[0052] The maximum diameter of the bubbles can be adjusted by regulating the foaming degree of the resin material and the degree of core removal.

[0053] The average diameter of the bubbles in the foamed layer of the foamed article is preferably 0.02 mm to 0.15 mm, more preferably 0.05 mm to 0.10 mm. If the average diameter of the bubbles in the foamed layer is within the above range, there is a tendency to further suppress undesirable appearance.

[0054] The average diameter of the bubbles was determined by observing an arbitrary cross-section obtained by cutting the foamed molded body along its thickness direction using a 3D measuring machine (50x magnification), and using this cross-section as the average of the major diameters of 30 bubbles. The average diameter of the bubbles can be adjusted by regulating the degree of foaming of the resin material and the degree of core removal.

[0055] The thickness of the foam layer in a foamed molded body is not particularly limited and can be set according to the desired thickness of the foamed molded body. For example, the average thickness of the foam layer in a foamed molded body can be 0.5 mm to 4.2 mm, or 1.0 mm to 4.0 mm. When the foamed molded body is manufactured by the core-removal method, the thickness of the foam layer along the moving direction of the core removal is defined as the thickness of the foam layer. The thickness of the foam layer can also vary depending on the location of the foamed molded body.

[0056] The thickness of the skin layer in the foamed molded article is not particularly limited. The average thickness of the skin layer is preferably 0.3 mm to 0.7 mm, more preferably 0.3 mm to 0.6 mm. The thickness of the skin layer can be adjusted according to the temperature of the mold in the forming cavity, etc. Generally speaking, the thickness of the skin layer of the foamed article formed by foaming is technically greater than or equal to 0.3 mm. In addition, if the average thickness of the skin layer is less than or equal to 0.7 mm, there is a tendency to supply a sufficient amount of resin material for foaming, which is preferred from the viewpoint of weight reduction and suppression of appearance defects. Furthermore, by adjusting the average thickness of the skin layer to 0.3 mm to 0.7 mm, an appropriate thickness of the foam layer can be ensured, and there is a tendency to produce a lightweight foamed article in which appearance defects are further suppressed.

[0057] The average thickness of the foamed layer and the skin layer in the foamed molded body was calculated by observing the cross-section and taking the average thickness at five randomly selected locations. It should be noted that, as... Figure 1A and Figure 1B As shown, the boundary between the epidermis and the foam layer is identifiable.

[0058] The following is a detailed description of the resin materials used in the fabrication of foamed molded articles.

[0059] -Resin Materials-

[0060] The resin material is preferably a resin material containing resin and foaming agent, but it may also contain other components such as additives as needed.

[0061] The resin used as a resin material may be selected from at least one group consisting of polyethylene resins, polypropylene resins (PP), polypropylene composite resins (PPC), polystyrene resins, polyethylene terephthalate resins, polyvinyl alcohol resins, vinyl chloride resins, ionomer resins, polyamide resins, acrylonitrile-butadiene-styrene copolymer resins (ABS), polycarbonate resins, and polyphenylene sulfide resins (PPS). Preferably, it is selected from at least one group consisting of polypropylene resins (PP), polypropylene composite resins (PPC), and acrylonitrile-butadiene-styrene copolymer resins (ABS).

[0062] In addition, examples of foaming agents include organic foaming agents such as azodicarbonamide and inorganic foaming agents such as sodium bicarbonate (also known as sodium bicarbonate or baking soda). In the foaming and molding of automotive interior parts, from the viewpoint of improving environmental testing performance and coating performance (such as resistance to hot water), organic foaming agents are preferred.

[0063] Examples of organic foaming agents include azodicarbonamide (ADCA), N,N-dinitrospentamethylenetetramine (DPT), 4,4'-oxobis(benzenesulfonylhydrazine) (OBSH), and hydrazine dicarboxamide (HDCA), with azodicarbonamide (ADCA) being the most preferred. Particularly in the manufacture of exterior accessories, azodicarbonamide (ADCA) in which the decomposition products are essentially anhydrous is preferred.

[0064] The content of azodicarbonamide (ADCA) in the total amount of foaming agent is preferably greater than or equal to 50% by mass, more preferably greater than or equal to 80% by mass, even more preferably greater than or equal to 90% by mass, and particularly preferably greater than or equal to 95% by mass.

[0065] The decomposition temperature of the foaming agent is preferably 50℃~250℃, more preferably 50℃~220℃. Depending on the application, the decomposition temperature of the foaming agent can also be 130℃~250℃.

[0066] The content of the foaming agent in the resin material is preferably set appropriately according to the type of foaming agent. For example, when using azodicarbonamide (ADCA) as the foaming agent, from the viewpoint of foaming properties, formability, and coating performance, the content of azodicarbonamide (ADCA) in the resin material is preferably in the range of 0.05% by mass to 0.5% by mass, and more preferably in the range of 0.1% by mass to 0.4% by mass. It should be noted that the content of ADCA refers to the proportion in the mixture (composition) before it is fed into the barrel of the injection molding machine described later.

[0067] Resin materials can also contain components other than resin and foaming agent. For example, resin materials can also contain fillers, glass fibers, carbon fibers, etc.

[0068] From the perspective of improving the crystallization peak temperature and melt tension of the foamed molded body, the resin material preferably includes a branched polypropylene resin, and more preferably includes a polypropylene-based resin and a branched polypropylene resin as the above-mentioned resin.

[0069] When the resin material contains branched polypropylene resin, the content of branched polypropylene resin relative to the total amount of resin material is preferably greater than or equal to 4% by mass, more preferably greater than or equal to 6% by mass, and even more preferably greater than or equal to 8% by mass.

[0070] When the resin material contains branched polypropylene resin, the content of branched polypropylene resin may be less than or equal to 20% by mass or less than or equal to 16% by mass.

[0071] The MFR (melt flow rate) of the branched polypropylene resin at 230°C is preferably greater than or equal to 35 g / 10 min, more preferably greater than or equal to 40 g / 10 min, and even more preferably greater than or equal to 50 g / 10 min.

[0072] The MFR of branched polypropylene resin at 230°C can be less than or equal to 100 g / 10 min, or less than or equal to 80 g / 10 min.

[0073] It should be noted that the MFR is the value measured according to JIS K7210-1 (2014) at 230℃ and a load of 2.16kg (i.e., 21.18N).

[0074] Applications of foamed molded materials

[0075] The applications of the foamed molded articles manufactured by the method of this disclosure are not particularly limited, and they are suitable for automotive interior parts such as console boxes, door panels, deck side panels, rear door panels, and dashboards, as well as automotive exterior parts such as arched trim strips, door sill plates, and box-shaped trim strips. In particular, because the foamed molded articles of this disclosure suppress appearance defects, they are also suitable for automotive interior and exterior parts that are not painted.

[0076] Manufacturing Method of Foamed Molded Articles

[0077] The method for manufacturing a foamed molded body disclosed herein includes: filling the cavity of a mold by injecting resin material into it (also referred to herein as an injection step); and expanding the volume of the cavity to foam the resin material filled within it (also referred to herein as a foaming step). The molded foamed body comprises a foamed layer and a skin layer covering the foamed layer. The average thickness of the skin layer is 0.3 mm to 0.7 mm. Expanding the volume of the cavity includes: removing the mold core so that the thickness of the molded foamed body is within ±0.2 mm of a predetermined target thickness. The method for manufacturing a foamed molded body disclosed herein may also include any steps other than those described above, as needed. Details of the resin material are as described above.

[0078] In the manufacturing method of the foamed molded body disclosed herein, during the foaming process, the foaming state can be controlled and appearance defects can be suppressed by removing the mold core in a manner within ±0.2 mm relative to the target thickness. The target thickness refers to the thickness of the foamed molded body to be obtained. Regarding the ±0.2 mm control width in the manufacturing method of the foamed molded body disclosed herein, from the viewpoint of technically ensuring the suppression of appearance defects, it is a width different from general design tolerances and is often smaller than the usual design tolerances. It can be considered that the foamed state of the foamed molded body obtained according to the manufacturing method of this disclosure is stable, that is, the bubble size is relatively uniform, and the generation of excessively large bubbles is suppressed, thus suppressing the generation of appearance defects. Therefore, according to the manufacturing method of the foamed molded body disclosed herein, quality can be technically guaranteed even without performing complex inspections such as cross-sectional observation of the foamed molded body.

[0079] Since the average thickness of the skin layer of the formed foamed body is 0.3mm to 0.7mm, the thickness of the foam layer of the foamed body to be formed is calculated as the target thickness minus the average thickness of the skin layer. By adjusting the core removal distance according to the calculated value of the foam layer thickness of the foamed body, the degree of foaming can be adjusted, thereby suppressing the generation of excessively large bubbles and preventing appearance defects. Therefore, it is believed that by controlling the core removal distance to within ±0.2mm of the target thickness of the foamed body, it is technically possible to ensure the suppression of appearance defects.

[0080] By controlling the core removal distance within ±0.2mm, it is possible to prevent excessive core removal, which could lead to excessive bubble growth or resin material peeling off from the mold and resulting in poor appearance. Conversely, it is also possible to prevent insufficient core removal, which could lead to insufficient foaming or insufficient rigidity due to thinning of the molded body.

[0081] In the method for manufacturing a foamed molded article disclosed herein, by removing the mold core in such a way that the thickness of the molded foamed article is within ±0.2 mm of the target thickness, the maximum diameter of the air bubbles in the molded foamed article is preferably controlled to be less than or equal to 0.90 mm, more preferably less than or equal to 0.50 mm, and even more preferably less than or equal to 0.20 mm. There is no particular limitation on the lower limit of the maximum diameter of the air bubbles. From the viewpoint of generating sufficient foam, the maximum diameter of the air bubbles can be controlled to be greater than or equal to 0.02 mm, greater than or equal to 0.05 mm, or greater than or equal to 0.10 mm. By investigating in advance the relationship between the core removal distance and the maximum diameter of the air bubbles when using any resin material, the maximum diameter of the air bubbles can be controlled.

[0082] The average diameter of the bubbles in the foamed layer of the molded foamed article is preferably 0.02 mm to 0.15 mm, more preferably 0.05 mm to 0.10 mm. If the average diameter of the bubbles in the foamed layer is within the above range, there is a tendency to further suppress poor appearance.

[0083] In addition, the details of the foamed articles manufactured by the manufacturing method of the foamed articles disclosed herein can be applied to the details of the foamed articles disclosed above.

[0084] To illustrate the method for manufacturing the foamed molded articles disclosed herein, Figure 2 This is a schematic diagram illustrating an example of a molding apparatus for a foamed article. It should be noted that the method for manufacturing a foamed article disclosed herein is not limited to... Figure 2 The structure shown.

[0085] Figure 2 This is a schematic diagram showing the configuration of a molding apparatus suitable for manufacturing foamed molded articles. Figure 2 The forming apparatus 16 shown includes a fixed side mold 17 and a movable side mold 19. The movable side mold 19 can move relative to the fixed side mold 17 in the opening and closing direction and forms a cavity 18 as a gap between it and the fixed side mold 17.

[0086] Furthermore, the molding apparatus 16 includes a gate 21 that extends through the fixed-side mold 17 to the cavity 18, and an injection molding machine 22 that injects molten resin material R into the cavity 18 through the gate 21. The injection molding machine 22 includes a hopper (supply section) and a barrel (not shown). In this injection molding machine 22, a mixture containing resin, foaming agent, and additives as needed is supplied from the hopper (supply section) to the barrel, and stirred in the barrel using a screw or the like to prepare resin material R. Under a predetermined pressure, the resin material R is injected into the cavity 18 through the gate 21. It should be noted that the injection molding machine 22 is not limited to the above configuration as long as it can inject molten resin material R into the cavity 18 through the gate 21.

[0087] When the resin material R contains a thermoplastic resin, the resin material R is heated to fluidize it and supplied into the cavity 18.

[0088] Furthermore, the fixed-side mold 17 and the movable-side mold 19 are typically at a temperature lower than that of the molten resin material R. Therefore, by filling the cavity 18 with the resin material R, the cooling and solidification of the resin material R begins from the portion in contact with the fixed-side mold 17 and the movable-side mold 19, forming a skin layer.

[0089] Next, the movable mold 19 is opened by a predetermined amount (core removal) relative to the fixed mold 17 in the opening direction (mold opening direction), causing the uncured resin material R to foam and form a foam layer. Then, the fixed mold 17 and the movable mold 19 are opened, and the foamed molded body is removed from the movable mold 19, thereby obtaining the foamed molded body. In the foamed molded body manufacturing method disclosed herein, the mold core is removed such that the thickness of the molded foamed body is within ±0.2 mm of a predetermined target thickness. In the molded foamed body, the thickness of the skin layer is 0.3 mm to 0.7 mm.

[0090] Methods for suppressing poor appearance of foamed molded articles

[0091] The method for suppressing appearance defects in the foamed molded body disclosed herein includes: filling the cavity with resin material by injecting resin material into the cavity of a mold (i.e., injection step), and foaming the resin material filled in the cavity by increasing the volume of the cavity (i.e., foaming step). The molded foamed body has a foamed layer and a skin layer covering the foamed layer. The average thickness of the skin layer is 0.3 mm to 0.7 mm. Increasing the volume of the cavity includes: removing the mold core in such a way that the thickness of the molded foamed body is within ±0.2 mm of a predetermined target thickness.

[0092] Similar to the method for manufacturing foamed molded articles disclosed above, this method can effectively suppress appearance defects in foamed molded articles. Details of each step in the method for suppressing appearance defects in foamed molded articles and details of the manufactured foamed molded articles can be applied to the methods for manufacturing foamed molded articles and the foamed molded articles of this disclosure described above, respectively.

[0093] Example

[0094] The embodiments of this disclosure will be described in detail below, but the embodiments of this disclosure are not limited to these embodiments.

[0095] <Example 1>

[0096] use Figure 2 The molding apparatus illustrated herein uses a core-removal method to fabricate a molded body through injection foaming. The target molded body thickness is set to 3.4 mm, and the core-removal distance is also set. The thickness of the molded body after molding is within ±0.2 mm of the target thickness. The average thickness of the skin layer is 0.5 mm.

[0097] <Comparative Example 1>

[0098] In Example 1, the molded body was manufactured in the same manner as in Example 1, except that the core-unwinding distance was increased. The thickness of the molded body after molding was greater than the target thickness set in Example 1, exceeding 0.2 mm. The average thickness of the skin layer was 0.5 mm.

[0099] In Example 1 and Comparative Example 1, the appearance defects of the molded body were visually inspected after molding. As a result, no appearance defects occurred in Example 1, but appearance defects occurred in Comparative Example 1. Furthermore, the cross-section obtained by cutting the molded body along the thickness direction was observed using a 3D measuring machine (50x magnification), and the maximum diameter and average diameter of the bubbles were determined by the above method.

[0100] The appearance and cross-section of the parts in Example 1 that did not produce any defects are shown in the figure. Figure 3 The maximum diameter of the bubble is 0.487 mm.

[0101] In addition, measurements were taken of the areas in Example 1 that did not produce any cosmetic defects (compared to...). Figure 3 The average diameter of the bubbles (from different locations) was measured, and the average diameter of the 30 bubbles was 0.08 mm.

[0102] The appearance and cross-sectional diagrams of the two areas that produced appearance defects in Comparative Example 1 are shown below. Figure 4 The maximum diameters of the bubbles were 1.116 mm and 1.039 mm, respectively.

[0103] As can be seen from the above, if the maximum diameter of the air bubbles in the foam layer of the foamed molded body is less than or equal to 0.90 mm, then poor appearance can be suppressed.

[0104] The disclosure of Japanese Patent Application No. 2019-187117 is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described herein, as well as those specifically described and incorporated herein by reference, are incorporated herein to the same extent.

[0105] Symbol Explanation

[0106] 16 Forming device

[0107] 17 Fixed Side Mold

[0108] 18 chambers

[0109] 19 Movable Side Mold

[0110] 21 gate

[0111] 22 injection machine

[0112] R resin material.

Claims

1. A foamed molded body having a foamed layer and a skin layer covering the foamed layer, wherein the maximum diameter of the air bubbles in the foamed layer is less than or equal to 0.90 mm.

2. The foamed molded body according to claim 1, wherein the average thickness of the skin layer is 0.3 mm to 0.7 mm.

3. The foamed molded body according to claim 1 or 2, wherein the average diameter of the bubbles in the foamed layer is 0.02 mm to 0.15 mm.

4. A method for manufacturing a foamed molded article, comprising: The resin material is filled into the cavity of the mold by injecting it into the cavity; as well as The resin material filling the cavity is foamed by increasing the volume of the cavity. The formed foamed body comprises a foamed layer and a skin layer covering the foamed layer, wherein the average thickness of the skin layer is 0.3 mm to 0.7 mm. Expanding the volume of the cavity includes: removing the mold core in such a way that the thickness of the formed foamed body is within ±0.2 mm relative to a pre-set target thickness.

5. The method for manufacturing a foamed molded body according to claim 4, wherein the mold core is removed such that the thickness of the foamed molded body after molding is within ±0.2 mm relative to a pre-set target thickness, thereby controlling the maximum diameter of the air bubbles in the foamed molded body to be less than or equal to 0.90 mm.

6. The method for manufacturing a foamed molded article according to claim 4 or 5, wherein the average diameter of the bubbles in the foamed layer is 0.02 mm to 0.15 mm.

7. A method for suppressing poor appearance of foamed molded articles, comprising: The resin material is filled into the cavity of the mold by injecting it into the cavity; as well as The resin material filling the cavity is foamed by increasing the volume of the cavity. The formed foamed body comprises a foamed layer and a skin layer covering the foamed layer, wherein the average thickness of the skin layer is 0.3 mm to 0.7 mm. Expanding the volume of the cavity includes: removing the mold core in such a way that the thickness of the formed foamed body is within ±0.2 mm relative to a pre-set target thickness.

8. The method for suppressing poor appearance of a foamed molded body according to claim 7, wherein the maximum diameter of the air bubbles in the molded foamed body is controlled to be less than or equal to 0.90 mm by removing the mold core in such a way that the thickness of the foamed molded body is within ±0.2 mm relative to the target thickness.

9. The method for suppressing poor appearance of foamed molded articles according to claim 7 or 8, wherein the average diameter of the bubbles in the foamed layer is 0.02 mm to 0.15 mm.

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