Foamed molded body, method for producing foamed molded body, and method for suppressing appearance defects of foamed molded body

Abstract

To provide a foam molded body in which appearance defects such as avatar and swirls are suppressed, a method for manufacturing a foam molded body in which appearance defects of the molded body can be suppressed, and a method for suppressing appearance defects of a foam molded body.SOLUTION: The present invention provides a foam molded body including a foam layer, and a skin layer covering the foam layer and having a specific bubble diameter; and a method for manufacturing a foam molded body or a method for suppressing appearance defects.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present 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 Art

[0002] Injection foamed molded bodies of thermoplastic resins such as polypropylene-based resins and acrylonitrile-butadiene-styrene copolymer-based resins are used as automotive members from the viewpoints of being lightweight and having excellent rigidity. As one of the injection foaming molding methods, there is the core-back method. The core-back method is a method in which a thermoplastic resin composition containing a foaming agent is injection molded to fill the mold with the thermoplastic resin composition, and then the position of the movable mold is slid to expand the cavity volume to obtain a molded product. By using this molding method, the surface layer of the molded body becomes a non-foamed layer (skin layer), and the inside of the molded body becomes a foamed layer (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When an injection foamed molded body is used as an automotive interior part such as a console box, a door trim, a deck side trim, a back door trim, an instrument panel, or an automotive exterior part such as an arch mold, a rocker mold, or a sash mold, the injection foamed molded body is desired to be lightweight, thin-walled, and have good appearance.

[0005] However, on the surface of the injection foam molded article, there are likely to occur appearance defects such as circular or elliptical small depressions (sometimes referred to as "avatar") and linear traces (sometimes referred to as "swirl") formed on the surface of the molded article along the flow of the resin during molding, which may cause problems in appearance. The avatar is generated by bubbles remaining on the resin surface and bursting during injection foam molding, and the swirl is caused by the portion where the bubbles burst being stretched by the flow of the resin, respectively.

[0006] In view of such a situation, an object of the present disclosure is to provide a foam molded article in which appearance defects such as avatar and swirl are suppressed, a method for manufacturing a foam molded article capable of suppressing appearance defects of the molded article, and a method for suppressing appearance defects of the foam molded article.

Means for Solving the Problems

[0007] The means for solving the above problems include the following aspects. <1> A foam molded article comprising a foam layer and a skin layer covering the foam layer, wherein the maximum diameter of the bubbles in the foam layer is 0.90 mm or less. <2> The foam molded article according to <1>, wherein the average thickness of the skin layer is 0.3 mm to 0.7 mm. <3> The foam molded article according to <1> or <2>, wherein the average diameter of the bubbles in the foam layer is 0.02 mm to 0.15 mm. <4> Injecting a resin material into the cavity of a mold to fill the resin material into the cavity, Expanding the volume of the cavity to foam the resin material filled in the cavity, including, The foam molded article after molding comprises a foam layer and a skin layer covering the foam layer, the average thickness of the skin layer is 0.3 mm to 0.7 mm, Expanding the volume of the cavity includes core-backing the mold so that the thickness of the foam molded article after molding is within ±0.2 mm of a preset target thickness, A method for manufacturing a foam molded article. <5> By core-backing the mold so that the thickness of the foamed molded body after molding is within ±0.2 mm with respect to a preset target thickness, the maximum diameter of the bubbles in the foamed molded body after molding is controlled to 0.90 mm or less. The method for producing a foamed molded body according to <4>. <6> The average diameter of the bubbles in the foamed layer is 0.02 mm to 0.15 mm. The method for producing a foamed molded body according to <4> or <5>. <7> Injecting a resin material into the cavity of the mold to fill the resin material in the cavity, Expanding the volume of the cavity to foam the resin material filled in the cavity, including, The foamed molded body after molding includes 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 core-backing the mold so that the thickness of the foamed molded body after molding is within ±0.2 mm with respect to a preset target thickness. Method for suppressing appearance defects of a foamed molded body. <8> By core-backing the mold so that the thickness of the foamed molded body after molding is within ±0.2 mm with respect to a preset target thickness, the maximum diameter of the bubbles in the foamed molded body after molding is controlled to 0.90 mm or less. The method for suppressing appearance defects of a foamed molded body according to <7>. <9> The average diameter of the bubbles in the foamed layer is 0.02 mm to 0.15 mm. The method for suppressing appearance defects of a foamed molded body according to <7> or <8>.

Effect of the Invention

[0008] According to the present disclosure, there are provided a foamed molded body with suppressed appearance defects such as avatar and swirl, a method for producing a foamed molded body capable of suppressing appearance defects of the molded body, and a method for suppressing appearance defects of a foamed molded body.

Brief Description of the Drawings

[0009]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0010] Hereinafter, the embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present invention.

[0011] In the present disclosure, the term "step" includes not only a step independent of other steps but also the step even if it cannot be clearly distinguished from other steps as long as the purpose of the step is achieved. In the numerical range indicated by "~" in the present disclosure, the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of other stepwise described numerical ranges. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, each component may contain a plurality of corresponding substances. When there are a plurality of substances corresponding to each component in the composition, the content rate or content of each component means the total content rate or content of the plurality of substances present in the composition unless otherwise specified. In the present disclosure, the terms "layer" or "film" include cases where, when observing the region where the layer or film exists, in addition to being formed over the entire region, it is also formed only in a part of the region. When embodiments in the present disclosure are described with reference to the drawings, the configuration of the embodiments is not limited to the configuration shown in the drawings. Also, the sizes of the members in each figure are conceptual, and the relative size relationships between the members are not limited thereto. Further, in each drawing, members having substantially the same function may be given the same reference numeral throughout the drawings, and redundant descriptions may be omitted.

[0012] ≪Foamed molded article≫ The foamed molded article of the present disclosure includes a foamed layer and a skin layer covering the foamed layer, and the maximum diameter of the bubbles in the foamed layer is 0.90 mm or less.

[0013] Regarding the problem of appearance defects in the foamed molded article, the inventors initially speculated that appearance defects occurred due to insufficient foaming in the foaming process and proceeded with the study. Generally, in the core-back method, if the foaming is insufficient, the resin material cannot follow the mold, and appearance defects are likely to occur. However, conversely, it has been found that by controlling the foaming state and controlling the bubble size to 0.90 mm or less, appearance defects are suppressed. The reason for this is not necessarily clear, but it is presumed that when the sizes of the bubbles in the foamed layer are relatively uniform, the occurrence of surface dents is suppressed.

[0014] The relationship between the maximum diameter of the bubbles in the foamed layer and appearance defects will be described with reference to FIGS. 1A and 1B. FIG. 1A shows a cross-sectional view of a foamed molded article according to an embodiment of the present disclosure. In FIG. 1A, the maximum diameter of the bubbles in the foamed layer is 0.20 mm or less, and the average bubble diameter is 0.10 mm. Appearance defects are suppressed in the foamed molded article shown in FIG. 1A. On the other hand, FIG. 1B is a cross-sectional view of a foamed molded article in which bubbles having a bubble diameter of 0.93 mm are present in the foamed layer. The foamed molded article shown in FIG. 1B has dents on the surface and appearance defects.

[0015] The foamed molded body includes a foamed layer and a skin layer that covers the foamed layer. The foamed layer is a layer formed by foaming a resin material, and the skin layer is a layer formed by cooling and solidifying this resin material. The foamed layer is a layer formed by foam-molding the resin material filled in a mold, and the skin layer is a layer formed by cooling and solidifying the resin material and having a lower foaming ratio than the foamed layer. The foamed molded body may be manufactured by the manufacturing method of the foamed molded body described later.

[0016] The maximum diameter of the bubbles in the foamed layer of the foamed molded body of the present disclosure is 0.90 mm or less, preferably 0.50 mm or less, more preferably 0.40 mm or less, and even more preferably 0.20 mm or less. The lower limit value of the maximum diameter of the bubbles is not particularly limited, and from the viewpoint of causing sufficient foaming, the maximum diameter of the bubbles may be 0.02 mm or more, 0.05 mm or more, or 0.10 mm or more. The maximum diameter of the bubbles of the foamed molded body is the maximum major axis when any cross-section obtained by cutting the foamed molded body in the thickness direction is observed with a 3D measuring machine (magnification 50 times). Here, the cross-section of the foamed molded body is a cross-section cut along the core-back direction when the mold is core-backed in the foaming process described later. The maximum diameter of the bubbles can be adjusted by adjusting the degree of foaming of the resin material, adjusting the degree of core-back, and the like.

[0017] The average diameter of the bubbles in the foamed layer of the foamed molded body is preferably 0.02 mm to 0.15 mm, and more preferably 0.05 mm to 0.10 mm. When the average diameter of the bubbles in the foamed layer is within the above range, appearance defects tend to be suppressed better. The average diameter of the bubbles is obtained as the average value of the major axes of 30 bubbles by observing any cross-section obtained by cutting the foamed molded body in the thickness direction with a 3D measuring machine (magnification 50 times). The average diameter of the bubbles can be adjusted by adjusting the degree of foaming of the resin material, adjusting the degree of core-back, and the like.

[0018] The thickness of the foam layer in the foam molded body is not particularly limited and can be set according to the thickness of the target foam molded body. For example, the average thickness of the foam layer of the foam molded body may be 0.5 mm to 4.2 mm, or may be 1.0 mm to 4.0 mm. When the foam molded body is manufactured by the core-back method, the thickness of the foam layer along the moving direction of the core-back is defined as the thickness of the foam layer. The thickness of the foam layer may vary depending on the part of the foam molded body.

[0019] The thickness of the skin layer in the foam molded body is not particularly limited. The average thickness of the skin layer is preferably 0.3 mm to 0.7 mm, and more preferably 0.3 mm to 0.6 mm. The thickness of the skin layer can be adjusted by factors such as the temperature of the mold forming the cavity. Generally, the thickness of the skin layer of the foam molded body formed by foam molding is technically about 0.3 mm or more. Also, when the average thickness of the skin layer is 0.7 mm or less, a sufficient amount of resin material tends to be used for foaming, which is preferable from the viewpoints 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 a foam molded body that is lightweight and has more suppressed appearance defects tends to be produced.

[0020] The average thicknesses of the foam layer and the skin layer in the foam molded body are determined as the average values of the thicknesses at five randomly selected locations by cross-sectional observation. As shown in FIGS. 1A and 1B, the boundary between the skin layer and the foam layer is visible.

[0021] Hereinafter, the resin material used for manufacturing the foam molded body will be described in detail.

[0022] - Resin Material - The resin material is preferably a resin material containing a resin and a foaming agent, and may contain other components such as additives as necessary.

[0023] Examples of the resin used for the resin material include at least one selected from the group consisting of polyethylene resins, polypropylene resins (PP), composite polypropylene 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). Among these, at least one selected from the group consisting of polypropylene resins (PP), composite polypropylene resins (PPC), and acrylonitrile-butadiene-styrene copolymer resins (ABS) is preferable.

[0024] Examples of the foaming agent include organic foaming agents such as azodicarbonamide, and inorganic foaming agents such as sodium hydrogen carbonate (also known as sodium bicarbonate, baking soda). In the foam molding of automotive interior parts, organic foaming agents are preferable from the viewpoints of improving environmental test performance, coating film performance (such as hot water resistance), and the like.

[0025] Examples of the organic foaming agent include azodicarbonamide (ADCA), N,N-dinitrosopentamethylenetetramine (DPT), 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH), hydrazodicarbonamide (HDCA), etc., and azodicarbonamide (ADCA) is preferable. In particular, when manufacturing exterior parts, it is preferable to use azodicarbonamide (ADCA) in which the decomposition product contains almost no water.

[0026] The content rate of azodicarbonamide (ADCA) in the total amount of the foaming agent is preferably 50% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0027] The decomposition temperature of the foaming agent is preferably 50°C to 250°C, more preferably 50°C to 220°C. Depending on the usage form, the decomposition temperature of the foaming agent may be 130°C to 250°C.

[0028] The content rate of the foaming agent in the resin material is preferably set as appropriate according to the type of the foaming agent and the like. For example, when azodicarbonamide (ADCA) is used as the foaming agent, from the viewpoints of foamability, moldability, and coating film performance, the content rate 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. Note that the content rate of ADCA means the ratio in the mixture (composition) before being charged into the cylinder of the injection machine described later.

[0029] The resin material may contain components other than the resin and the foaming agent. For example, the resin material may contain a filler, glass fiber, carbon fiber, or the like.

[0030] From the viewpoint of increasing the crystallization peak temperature, melt tension, etc. of the foam molded body, the resin material preferably contains a polypropylene resin having a branched chain, and more preferably contains a polypropylene resin having a branched chain together with a polypropylene-based resin as the aforementioned resin.

[0031] When the resin material contains a polypropylene resin having a branched chain, the content rate of the polypropylene resin having a branched chain is preferably 4% by mass or more, more preferably 6% by mass or more, and even more preferably 8% by mass or more with respect to the total amount of the resin material.

[0032] When the resin material contains a polypropylene resin having a branched chain, the content rate of the polypropylene resin having a branched chain may be 20% by mass or less, or may be 16% by mass or less.

[0033] The MFR (melt flow rate) of the polypropylene resin having a branched chain at 230°C is preferably 35 g / 10 min or more, more preferably 40 g / 10 min or more, and even more preferably 50 g / 10 min or more.

[0034] The MFR of the polypropylene resin having a branched chain at 230°C may be 100 g / 10 min or less, or may be 80 g / 10 min or less. Note that the MFR is the value measured at 230°C under a load of 2.16 kg (i.e., a load of 21.18 N) in accordance with JIS K7210-1(2014).

[0035] 〔Applications of the Foamed Molded Body〕 The applications of the foamed molded body produced by the production method of the present disclosure are not particularly limited, and it can be suitably used for automotive interior parts such as console boxes, door trims, deck side trims, back door trims, instrument panels, and automotive exterior parts such as arch moldings, rocker moldings, and sash moldings. In particular, the foamed molded body of the present disclosure can be suitably used for automotive interior and exterior parts that are not painted because appearance defects are suppressed.

[0036] ≪Method for Producing Foamed Molded Body≫ The method for producing a foamed molded body of the present disclosure includes filling the resin material into the cavity of the mold by injecting the resin material into the cavity of the mold (also referred to as the injection step in the present disclosure), and expanding the volume of the cavity to foam the resin material filled in the cavity (also referred to as the foaming step in the present disclosure). The foamed molded body after molding includes 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 core-backing the mold so that the thickness of the foamed molded body after molding is within ±0.2 mm of a preset target thickness. The method for producing a foamed molded body of the present disclosure may include any other steps as necessary in addition to the above. The details of the resin material are as described above.

[0037] In the method for manufacturing a foamed molded body of the present disclosure, in the foaming step, the foaming state can be controlled and appearance defects can be suppressed by core-backing the mold so that it is within ±0.2 mm with respect to the target thickness. The target thickness is the thickness of the foamed molded body to be obtained. The management width of ±0.2 mm in the method for manufacturing a foamed molded body of the present disclosure is a width that is distinguished from general design tolerances from the viewpoint of technically ensuring the suppression of appearance defects, and is often smaller than normal design tolerances. The foamed molded body obtained according to the manufacturing method of the present disclosure has a stable foaming state, that is, the sizes of the bubbles are relatively uniform, and the generation of bubbles that are too large in size is suppressed. Therefore, it is considered that the occurrence of appearance defects can be suppressed. Therefore, according to the method for manufacturing a foamed molded body of the present disclosure, even when complicated inspections such as cross-sectional observation of the foamed molded body are not performed, the quality can be technically guaranteed.

[0038] Since the average thickness of the skin layer of the foamed molded body after molding is 0.3 mm to 0.7 mm, the thickness of the foamed layer of the foamed molded body to be molded is calculated as a value obtained by subtracting the average thickness of the skin layer from the target thickness. By adjusting the degree of foaming by adjusting the core-back distance so that the thickness of the foamed layer of the foamed molded body becomes the value calculated in this way, the generation of bubbles that are too large in size can be suppressed, and appearance defects can be suppressed. Therefore, it is considered that by controlling the core-back distance within ±0.2 mm with respect to the target thickness of the foamed molded body, the suppression of appearance defects can be technically ensured.

[0039] By managing the core-back distance within a width of ±0.2 mm, it is possible to suppress the occurrence of appearance defects such as the core-back amount being too large and the bubbles growing too much, or the resin material peeling off from the mold. Conversely, it is also possible to suppress the occurrence of insufficient foaming due to the core-back amount being too small, or the rigidity becoming insufficient due to the thickness of the molded body becoming thin.

[0040] In the method for manufacturing the foamed molded article of the present disclosure, the mold is core-back so that the thickness of the foamed molded article after molding is within ±0.2 mm with respect to the target thickness, whereby the maximum diameter of the bubbles in the foamed molded article after molding is preferably controlled to 0.90 mm or less, more preferably controlled to 0.50 mm or less, and even more preferably controlled to 0.20 mm or less. The lower limit value of the maximum diameter of the bubbles is not particularly limited, and from the viewpoint of causing sufficient foaming, the maximum diameter of the bubbles may be controlled to 0.02 mm or more, may be controlled to 0.05 mm or more, or may be controlled to 0.10 mm or more. By examining in advance the relationship between the core-back distance and the maximum diameter of the bubbles when using any resin material, it is possible to control the maximum diameter of the bubbles.

[0041] The average diameter of the bubbles in the foamed layer of the foamed molded article after molding is preferably 0.02 mm to 0.15 mm, and more preferably 0.05 mm to 0.10 mm. When the average diameter of the bubbles in the foamed layer is within the above range, appearance defects tend to be better suppressed.

[0042] In addition, details of the foamed molded article manufactured by the method for manufacturing the foamed molded article of the present disclosure can be applied to the details of the foamed molded article of the present disclosure described above.

[0043] To explain the method for manufacturing the foamed molded article of the present disclosure, FIG. 2 shows a schematic configuration diagram of an example of a molding apparatus for the foamed molded article. Note that the method for manufacturing the foamed molded article of the present disclosure is not limited to the configuration shown in FIG. 2.

[0044] FIG. 2 shows a schematic configuration diagram of a molding apparatus applicable to the manufacture of a foamed molded article. The molding apparatus 16 shown in FIG. 2 includes a fixed-side mold 17 and a movable-side mold 19 that is movable in the opening and closing direction with respect to the fixed-side mold 17 and forms a cavity 18 that is a gap between the fixed-side mold 17.

[0045] Further, the molding apparatus 16 includes a gate 21 that penetrates the fixed mold 17 to the cavity 18, and an injection machine 22 that injects and fills the molten resin material R into the cavity 18 through the gate 21. The injection machine 22 includes a hopper (supply unit) (not shown) and a cylinder (not shown). In this injection machine 22, a mixture containing a resin, a foaming agent, and additives used as necessary is supplied from the hopper (supply unit) to the cylinder, stirred in the cylinder by a screw or the like to be prepared as the resin material R, and the resin material R is injected and filled into the cavity 18 through the gate 21 at a predetermined pressure. Note that the injection machine 22 is not limited to the above configuration as long as it can inject and fill the molten resin material R into the cavity 18 through the gate 21.

[0046] When the resin material R contains a thermoplastic resin, the resin material R is heated to be fluidized and supplied into the cavity 18.

[0047] Also, the fixed mold 17 and the movable mold 19 are normally at a temperature lower than that of the molten resin material R. Therefore, when the resin material R is filled into the cavity 18, cooling and solidification of the resin material R start from the portions in contact with the fixed mold 17 and the movable mold 19, and a skin layer is formed.

[0048] Next, the movable mold 19 is opened (core-back) by a predetermined amount in the opening direction (mold-opening direction) with respect to the fixed mold 17 to foam the unfixed resin material R to form a foam layer. Then, the fixed mold 17 and the movable mold 19 are opened, and the foam molded body is removed from the movable mold 19 to obtain the foam molded body. In the method for manufacturing a foam molded body of the present disclosure, the mold is core-backed so that the thickness of the foam molded body after molding is within ±0.2 mm with respect to a preset target thickness. In the foam molded body after molding, the thickness of the skin layer is 0.3 mm to 0.7 mm.

[0049] ≪Method for Suppressing Appearance Defects of Foam Molded Body≫ The method for suppressing appearance defects of the foam molded body of the present disclosure includes filling the resin material into the cavity of the mold by injecting the resin material into the cavity of the mold (i.e., the injection step), and expanding the volume of the cavity to foam the resin material filled in the cavity (i.e., the foaming step). The foam molded body after molding includes 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 core-backing the mold so that the thickness of the foam molded body after molding is within ±0.2 mm of a preset target thickness.

[0050] Similar to the method for manufacturing the foam molded body of the present disclosure described above, according to this method, appearance defects of the foam molded body can be favorably suppressed. Details of each step in the method for suppressing appearance defects of the foam molded body, and details of the foam molded body to be manufactured can apply the above-described contents to the method for manufacturing the foam molded body of the present disclosure and the foam molded body of the present disclosure, respectively.

Example

[0051] Next, embodiments of the present disclosure will be specifically described by way of examples, but the embodiments of the present disclosure are not limited to these examples.

[0052] <Example 1> Using the molding apparatus schematically shown in FIG. 2, a molded body was produced by injection foam molding by the core-back method. The target thickness of the molded body was set to 3.4 mm, and the core-back distance was set. The thickness of the molded body after molding was within ±0.2 mm of the target thickness. The average thickness of the skin layer was 0.5 mm.

[0053] <Comparative Example 1> In Example 1, a molded body was produced in the same manner as in Example 1 except that the core-back distance was increased. The thickness of the molded body after molding was more than 0.2 mm larger than the target thickness set in Example 1. The average thickness of the skin layer was 0.5 mm.

[0054] In Example 1 and Comparative Example 1, after molding, the presence or absence of appearance defects of the molded body was visually observed. As a result, no appearance defects were found in Example 1, but appearance defects were found in Comparative Example 1. Further, a cross-section of the molded body cut in the thickness direction was observed with a 3D measuring machine (magnification: 50 times), and the maximum diameter and average diameter of the bubbles were determined by the method described above.

[0055] The appearance and cross-sectional view of the part where no appearance defect occurred in Example 1 are shown in FIG. 3. The maximum diameter of the bubbles was 0.487 mm.

[0056] In addition, when the average diameter of the bubbles at the part where no appearance defect occurred in Example 1 (a part different from FIG. 3) was measured, the average diameter of 30 bubbles was 0.08 mm.

[0057] The appearance and cross-sectional view of two parts where appearance defects occurred in Comparative Example 1 are shown in FIG. 4. The maximum diameters of the bubbles were 1.116 mm and 1.039 mm, respectively.

[0058] As can be seen from the above, when the maximum diameter of the bubbles in the foam layer of the foam molded body is 0.90 mm or less, appearance defects are suppressed.

[0059] The disclosure of Japanese Patent Application No. 2019-187117 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated as being incorporated by reference.

Explanation of Reference Numerals

[0060] 16 Molding device 17 Fixed mold 18 Cavity 19 Movable mold 21 Gate 22 Injection machine R Resin material

Claims

1. A foamed body comprising a foamed layer and a skin layer covering the foamed layer, wherein an average thickness of the foamed layer in the foamed molded body is from 0.5 mm to 4.2 mm, and an average diameter of bubbles in the foamed layer is from 0.05 mm to 0.15 mm.

2. The foamed molded body according to Claim 1, wherein a maximum diameter of bubbles measured in the same cross section as the average diameter of the bubbles in the foamed layer is 0.50 mm or less.

3. The foamed molded body according to Claim 1 or Claim 2, wherein the bubbles are bubbles formed by thermal decomposition of a foaming agent.

4. The foamed molded body according to any one of Claims 1 to 3, which is an automotive interior part or exterior part.

5. Injecting a resin material into a cavity of a mold to fill the resin material in the cavity, and expanding the volume of the cavity to foam the resin material filled in the cavity, wherein the foamed molded body after molding comprises a foamed layer and a skin layer covering the foamed layer, and an average diameter of bubbles in the foamed layer is from 0.05 mm to 0.15 mm, wherein expanding the volume of the cavity includes core-backing the mold so that a thickness of the foamed molded body after molding is within ±0.2 mm with respect to a preset target thickness, and by core-backing the mold so that the thickness of the foamed molded body after molding is within ±0.2 mm with respect to the preset target thickness, an average thickness of the foamed layer in the foamed molded body after molding is controlled to be from 0.5 mm to 4.2 mm. A method for manufacturing a foamed molded body.

6. The method according to Claim 5, wherein a maximum diameter of bubbles measured in the same cross section as the average diameter of the bubbles in the foamed layer of the foamed molded body is 0.50 mm or less.

7. The method according to Claim 5 or Claim 6, wherein the bubbles are formed by thermal decomposition of a foaming agent.

8. The method according to any one of Claims 5 to 7, wherein the foamed molded body is an automotive interior part or exterior part.

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