Container, manufacturing method thereof, and foam preform

Abstract

An object of the present disclosure is to provide a foam suitable for products that are susceptible to quality deterioration due to light, a method for manufacturing the same, a container, and a foam preform. [Solution] The foam of the present disclosure is a molded product made from a molding material containing a thermoplastic resin, and the foam has a first non-foamed layer and a foamed layer. The foamed layer includes a first foamed layer having a plurality of bubbles 2 arranged three-dimensionally as shown in Figure 3 and a cell wall skeleton 4 separating adjacent bubbles. The first foamed layer has a reticulated cell structure 5 in which the cell wall skeleton has a reticulated cross section, and the reticulated cell structure includes open cells in which adjacent bubbles communicate with each other via openings 6 provided in the cell wall skeleton.

Description

[Technical Field]

[0001] The present disclosure relates to a foam and a method for producing the same, a container, and a foam preform. [Background technology]

[0002] Resin foam molding originated at the Massachusetts Institute of Technology (MIT) in the United States, and since the 1980s, the technology has been applied to a variety of fields. In Japan, it is still widely used in resin injection-molded products such as automobile parts. Technology using foams to make containers has been proposed (see, for example, Patent Document 1). Patent Document 1 discloses that a preferred form for using foams in containers is that each foam cell is independent in the foamed state, as well as the dimensions of the foam cells, the foam concentration gradient in the container wall, and the light-blocking performance range of the aggregate of closed cells. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-234627 Summary of the Invention [Problem to be solved by the invention]

[0004] In the container of Patent Document 1, light-blocking properties are imparted by the multiple scattering and reflection of light caused by the closed cell aggregate. On the other hand, for products that are susceptible to deterioration due to light such as ultraviolet rays, such as beer drinks or cosmetic emulsions, extremely high light-blocking properties are required for packaging. However, according to the inventors' investigations, it was found that foaming by closed cells alone, as in the container of Patent Document 1, does not provide the light-blocking properties required for such products that are susceptible to deterioration due to light.

[0005] An object of the present disclosure is to provide a foam suitable for products that are susceptible to quality deterioration due to light, a method for manufacturing the same, a container, and a foam preform. [Means for solving the problem]

[0006] The foam according to the present invention is made of a thermoplastic resin. (However, this does not apply when the thermoplastic resin is a polyolefin resin.) Foamed products made from molding materials containing A container having a body as an outer wall, The foam has a first non-foamed layer and a foamed layer, the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer, The foam layer is a first foam layer having a plurality of cells arranged three-dimensionally and a cell wall skeleton separating adjacent cells. a second foam layer between the first non-foam layer and the first foam layer; The first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, and the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings provided in the cell wall skeleton. In the open cells, the cells are broken at the openings, the second foam layer has a sea-island structure in which a plurality of islands of cells are dispersed in a sea of ​​the molding material as a matrix, and the length of the cells of the second foam layer in the surface direction of the outer wall is shorter than the length of one of the adjacent cells that constitute the open cells of the first foam layer. It is characterized by:

[0007] The foam according to the present invention is a container having as an outer wall a foam that is a molded product of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), the foam having a first non-foamed layer and a foamed layer, the first non-foamed layer being disposed on the inner surface side of the container and the foamed layer being disposed on the outer surface side of the container relative to the first non-foamed layer, the foamed layer including a first foamed layer having a plurality of bubbles randomly arranged in three dimensions and a bubble wall skeleton separating adjacent bubbles, The first foam layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, and the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings provided in the cell wall skeleton, and closed cells in which adjacent cells do not communicate with each other, the open cells are broken at the openings, the open cells and the closed cells exist in the same cross section in the surface direction of the outer wall, and the total length of the cells constituting the open cells in the same cross section is greater than the length of the closed cells.

[0008] The present invention container In the present invention, the foam layer further includes a second foam layer between the first non-foam layer and the first foam layer, the second foam layer having an islands-in-a-sea structure in which bubbles are dispersed in a matrix made of the molding material.

[0009] The present invention In a container Preferably, the foam further has a second non-foamed layer, and the foamed layer is located between the first non-foamed layer and the second non-foamed layer. This ensures smoothness on both the front and back surfaces of the foam.

[0010] In the container of the present invention, it is preferable that the first foamed layer further includes closed bubbles at the boundary between the second non-foamed layer and the first foamed layer, and that the length of the closed bubbles present at the boundary in the surface direction of the outer wall is shorter than the length of one of the adjacent bubbles that make up the continuous bubbles.

[0011] The present invention container In this case, it is preferable that the reticulated cell structure further includes closed cells in which adjacent cells are not connected to each other, thereby making it possible to obtain a foam having higher strength.

[0012] The present invention container When the thickness of the foam is 250 μm or more and 450 μm or less, the surface of the foam opposite to the first non-foamed layer side is subjected to CIE1976 L* a * b * When measuring the chromaticity coordinates of the color space, L * The value of is between 70 and 100, and a * The value of is between -1.0 and 0, and b * It is preferable that the value is −2.0 or more and 0 or less. When the foam is used as the outer wall of a container, the light blocking properties can be further improved.

[0013] The present invention container Then, the surface of the foam on the side of the first non-foamed layer and the surface opposite to the first non-foamed layer side were measured according to CIE1976 L in accordance with JIS Z 8781-4:2013. * a * b * When the chromaticity coordinates of the color space are measured, the L * The value of L on the surface of the first non-foamed layer side * or the value of L * and the value of a on the surface opposite to the first non-foamed layer side is larger than the value of a * The value of a on the surface of the first non-foamed layer side is * or the value of a on the surface of the first non-foamed layer side is the same as the value of a * is smaller than the value of b on the surface opposite to the first non-foamed layer side, * The value of b on the surface of the first non-foamed layer side * or the value of b on the surface of the first non-foamed layer side is the same as the value of * It includes forms where the value is less than .

[0014] The present invention container In the case where the foam has a thickness of 250 μm or more and 450 μm or less, the surface of the foam opposite to the first non-foamed layer side preferably has a D65 brightness of 70 or more as measured in accordance with ISO 2470-2:2008. When the foam is used as the outer wall of a container, the light-blocking properties can be further improved.

[0015] The present invention containerIn this case, when the D65 whiteness of the surface of the foam facing the first non-foamed layer and the surface opposite the first non-foamed layer side are measured in accordance with ISO2470-2:2008, the D65 whiteness value of the surface opposite the first non-foamed layer side is the same as the D65 whiteness value of the surface facing the first non-foamed layer side or is greater than the D65 whiteness value of the surface facing the first non-foamed layer side.

[0016] The present invention container When the reflectance is measured on the surface of the foam facing the first non-foamed layer and the surface opposite the first non-foamed layer in accordance with JIS R 3106:2019 "Test methods for transmittance, reflectance, and emissivity of flat glass and calculation methods for solar heat gain coefficient of architectural flat glass," the reflectance value at wavelengths of 240 to 800 nm on the surface opposite the first non-foamed layer is the same as the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer, or is greater than the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer, and is within a range of 0 to 20% of the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer.

[0017] The present invention container When the thickness of the foam is 250 μm or more and 450 μm or less, the transmittance of the foam to light in the wavelength range of 480 to 500 nm is preferably 15% or less.When the foam is used as the outer wall of a container, the light-blocking properties can be further improved.

[0018] The present invention container In the case where the foam has a gas barrier film on at least one of the surface on the first non-foamed layer side and the surface opposite to the first non-foamed layer side, when the foam is used as the outer wall of a container, deterioration of the contents of the container can be prevented.

[0019] The present invention containerIn the present invention, the thermoplastic resin is a polyethylene terephthalate resin, and the intrinsic viscosity of the polyethylene terephthalate resin is 0.63 to 0.86 dl / g.

[0020] The foam preform according to the present invention is made of a thermoplastic resin (However, this does not apply when the thermoplastic resin is a polyolefin resin.) The foamed preform is a molded product of a molding material containing the above-mentioned compound, and has a first non-foamed layer and a pre-foamed layer, and the pre-foamed layer has a plurality of spherical foam cells, and the particle size distribution based on the number of the spherical foam cells has a distribution width of 52 μm or more. and having a broad particle size distribution in which And the mode diameter is 49 to 62 μm. The distribution width is the width of the frequency distribution graph of the particle size distribution obtained under the following condition 1: It is characterized by: Condition 1: The particle size distribution is determined by observing the cross section of the foamed preform at a magnification of 200 times using a reflected light microscope and measuring the number and diameter of each of the spherical foam cells present in the observed image.

[0021] The foamed preform according to the present invention includes a form in which the mode diameter is larger than the average diameter in the particle size distribution based on the number of the spherical foamed cells.

[0022] The container according to the present invention is a container that is a blow-molded product of the foamed preform according to the present invention, wherein the outer wall of the container has a first non-foamed layer and a foamed layer, the first non-foamed layer of the foamed preform is a layer that will become the first non-foamed layer of the outer wall of the container, and the pre-foamed layer of the foamed preform is a layer that will become the foamed layer of the outer wall of the container, the first non-foamed layer is arranged on the inner surface side of the container, and the foamed layer is arranged on the outer surface side of the container than the first non-foamed layer, the foamed layer includes a first foamed layer having a plurality of bubbles randomly arranged in three dimensions and a bubble wall skeleton that separates adjacent bubbles, the first foamed layer has a reticulated cell structure in which the bubble wall skeleton has a reticulated cross section, and the reticulated cell structure includes open cells that communicate with adjacent bubbles via openings provided in the bubble wall skeleton, and the open cells have bubbles that break at the openings.

[0023] The present invention container The manufacturing method of the thermoplastic resin (However, this does not apply when the thermoplastic resin is a polyolefin resin.) a step of preparing a cylindrical, bottomed, non-foamed preform that is impregnated with an inert gas and is in an unfoamed state; a foaming step of converting the non-foamed preform into a foamed preform; and a blow molding step of blow molding the foamed preform into a foamed article, wherein the foaming step includes a heating step of heating the non-foamed preform from the outer surface side to obtain an intermediate body; and a waiting step of conducting heat unevenly distributed on the outer surface side of the intermediate body after the heating step to the inner surface side to reduce the temperature difference between the outer surface and the inner surface of the intermediate body, and the blow molding step includes forming a container having the foam as an outer wall; the foam has a first non-foamed layer and a foamed layer, the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer, The foam layer has a plurality of cells arranged three-dimensionally and a cell wall skeleton separating adjacent cells. a second foam layer between the first non-foam layer and the first foam layer; Including fruit,The first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, and the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings provided in the cell wall skeleton. the open cells are broken at the openings, the second foam layer has a sea-island structure in which islands of bubbles are dispersed in a sea of ​​the molding material as a matrix, the length of the bubbles in the second foam layer in the surface direction of the outer wall is shorter than the length of one of the adjacent bubbles constituting the open cells of the first foam layer, and the waiting step is a step performed without inputting heat, a step performed with residual heat from the heating step remaining, or a step performed with inputting heat to the extent that the outer surface temperature of the intermediate body is lowered. It is characterized by:

[0024] The method for manufacturing a container according to the present invention includes a step of preparing a bottomed, cylindrical non-foamed preform, which is a molded product made of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), impregnated with an inert gas and in an unfoamed state; a foaming step of converting the non-foamed preform into a foamed preform; and a blow molding step of blow molding the foamed preform to form a foam, wherein the foaming step includes a heating step of heating the non-foamed preform from the outer surface side to obtain an intermediate body, and a waiting step of conducting heat unevenly distributed on the outer surface side of the intermediate body after the heating step to the inner surface side to reduce the temperature difference between the outer surface and the inner surface of the intermediate body, and the blow molding step is a step of forming a container having the foam body as an outer wall, wherein the foam body has a first non-foamed layer and a foamed layer, the first non-foamed layer is arranged on the inner surface side of the container, and the foamed layer is arranged on the first non-foamed layer. the first foam layer is disposed closer to the outer surface of the container than the foam layer, the foam layer having a plurality of bubbles randomly arranged in three dimensions and a bubble wall skeleton separating adjacent bubbles, the first foam layer having a reticulated bubble structure in which the bubble wall skeleton has a reticulated cross section, the reticulated bubble structure including open cells in which adjacent bubbles communicate with each other through openings provided in the bubble wall skeleton, and closed cells in which adjacent bubbles do not communicate with each other, the open cells are broken at the openings, the open cells and the closed cells are present in the same cross section in the surface direction of the outer wall, and the total length of the cells constituting the open cells in the same cross section is greater than the length of the closed cells, and the waiting step is performed without heat input, with residual heat from the heating step remaining, or with heat input to the extent that the outer surface temperature of the intermediate is reduced.

[0025] The method for manufacturing a container according to the present invention includes a step of preparing a bottomed, cylindrical non-foamed preform, which is a molded product of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), impregnated with an inert gas and in an unfoamed state; a foaming step of converting the non-foamed preform into a foamed preform; and a blow molding step of blow-molding the foamed preform into a foamed article, wherein the foaming step includes a heating step of heating the non-foamed preform from the outer surface side to obtain an intermediate body; and a waiting step of conducting heat unevenly distributed on the outer surface side of the intermediate body to the inner surface side after the step to reduce the temperature difference between the outer surface and the inner surface of the intermediate body, and the foamed preform has a first non-foamed layer and a pre-foamed layer, and the pre-foamed layer has a plurality of spherical foam cells, and the particle size distribution based on the number of the spherical foam cells has a broad particle size distribution with a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm, and the distribution width is a particle size distribution obtained under the following condition 1: the blow molding step is a step of forming a container having the foam as an outer wall, the foam has a first non-foamed layer obtained by blow molding the first non-foamed layer of the foam preform, and a foamed layer obtained by blow molding the pre-foamed layer of the foam preform, the first non-foamed layer is disposed on the inner surface side of the container, the foamed layer is disposed on the outer surface side of the container with respect to the first non-foamed layer, and the foamed layer has a plurality of bubbles randomly arranged in three-dimensional directions and a plurality of bubbles adjacent to each other and a cell wall skeleton separating the cells from each other, wherein the first foam layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, and the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings provided in the cell wall skeleton, and the open cells are broken at the openings, and the waiting step is a step performed without inputting heat, a step performed with residual heat from the heating step remaining, or a step performed with inputting heat to the extent that the outer surface temperature of the intermediate body drops. Condition 1: The particle size distribution is determined by observing the cross section of the foamed preform at a magnification of 200 times using a reflected light microscope and measuring the number and diameter of each of the spherical foam cells present in the observed image. By forming the pre-foamed layer in this manner, it becomes easier to form open cells in the first foamed layer in the resulting container.

[0026] The present invention container In the manufacturing method of the present invention, the foaming step is preferably a step in which one cycle consisting of the heating step and the waiting step is performed two or more times. By performing the heating step and the waiting step multiple times, bubbles can be grown throughout the entire thickness direction of the intermediate body, and the difference in bubble size between the side close to the outer surface and the side close to the inner surface of the intermediate body can be further reduced.

[0027] The present invention container In the manufacturing method of the present invention, the foaming step is a step of forming a foamed preform having a first non-foamed layer and a pre-foamed layer, the pre-foamed layer having a plurality of spherical foam cells, and the number-based particle size distribution of the spherical foam cells preferably has a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm. In the obtained foam, open cells of the first foamed layer are easily formed. [Effects of the Invention]

[0028] According to the present disclosure, it is possible to provide a foam suitable for products that are susceptible to quality deterioration due to light, a method for manufacturing the same, a container, and a foam preform. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic partial cross-sectional view showing an example of a foam according to an embodiment of the present invention. [Figure 2]FIG. 2 is a schematic diagram illustrating a first foam layer. [Figure 3] 1 is an image showing an example of a reticulated bubble structure. [Figure 4] 1 is an image showing an example of an island structure. [Figure 5] 1 is a schematic partial cross-sectional view showing an example of a foamed preform according to the present embodiment. FIG. [Figure 6] FIG. 2 is a schematic diagram illustrating a pre-foamed layer. [Figure 7] 1 is an image showing a cross section in the thickness direction of the foamed bottle of Example 1. [Figure 8] 1A and 1B are images showing a cross section perpendicular to the thickness direction of the foamed bottle of Example 1, where (a) shows the second non-foamed layer, (b) shows the first foamed layer, (c) shows the second foamed layer, and (d) shows the first non-foamed layer. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these descriptions. Various modifications may be made to the embodiments as long as the effects of the present invention are achieved.

[0031] As shown in FIG. 1, the foam 1 according to this embodiment is a molded product made of a molding material containing a thermoplastic resin. The foam 1 has a first non-foamed layer 11 and a foamed layer 20. As shown in FIG. 2, the foamed layer 20 includes a first foamed layer 21 having a plurality of cells 2 arranged three-dimensionally and a cell wall skeleton 4 separating adjacent cells 2. As shown in FIG. 3, the first foamed layer 21 has a reticulated cell structure 5 in which the cell wall skeleton 4 has a reticulated cross section. The reticulated cell structure 5 includes open cells in which adjacent cells 2 communicate with each other via openings 6 formed in the cell wall skeleton 4.

[0032] The molding material is a material containing a thermoplastic resin as a main component. The thermoplastic resin is not particularly limited, but examples include polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile-butadiene-styrene resin (ABS), acrylonitrile-styrene resin (AS), acrylic resin (PMMA), and polyacetal (POM). Of these, PET is preferred as the thermoplastic resin. The molding material may consist solely of a thermoplastic resin, or may contain various known additives or colorants in addition to the thermoplastic resin, as long as they do not impair the effects of the present invention.

[0033] The foam 1 is not particularly limited, but is preferably in the form of a plate, wall, or sheet having a front and back surface, and is more preferably a blow-molded product.

[0034] The first non-foamed layer 11 is a layer that does not substantially contain bubbles 2 and is generally called a skin layer. The surface of the first non-foamed layer 11 preferably forms either the front or back surface of the foam 1. The thickness of the first non-foamed layer 11 is not particularly limited, and is preferably 3 to 15% of the total thickness of the foam 1, and more preferably 5 to 13%.

[0035] The foam layer 20 is a layer containing bubbles 2. The thickness of the foam layer 20 is not particularly limited, and is preferably 65 to 97% of the total thickness of the foam 1, and more preferably 67 to 95%.

[0036] The first foamed layer 21 is a layer of the foamed layer 20 in which the bubbles 2 have expanded excessively. As the bubbles 2 have grown larger, the solid portions around the bubbles 2 have been crushed, forming thin walls or thin columns. In the first foamed layer 21, the bubbles 2 are randomly arranged in the X, Y, and Z axes of the foam, as shown in FIG. 2 . Here, the X axis is the direction parallel to the surface of the foam 1, the Y axis is the direction parallel to the surface of the foam 1 and perpendicular to the X axis, and the Z axis is the direction perpendicular to the surface of the foam 1, i.e., the thickness direction of the foam 1. In the first foamed layer 21, most of the bubbles 2 have flat shapes with maximum widths in the X and Y axes, respectively, and are distributed with partial overlap in the Z axis direction.

[0037] FIG. 3 is a slice image of the foam 1 in the thickness direction observed using an X-ray transmission inspection device (μnRay7600F, manufactured by Matsusada Precision Co., Ltd.). The scale in the lower right corner of FIG. 3 indicates 0.25 mm. In FIG. 3, the white parts are cell walls 3, and the black parts are cells 2. As shown in FIG. 3, the periphery of each cell 2 is surrounded by a cell wall 3 made of the molding material. Adjacent cells 2 share a part of the cell wall 3. The cell wall skeleton 4 is a three-dimensional structure constituting the first foamed layer 21, in which the cell walls 3 surrounding each cell 2 are connected three-dimensionally. The cell wall skeleton 4 preferably has a three-dimensional mesh structure connected in a network-like manner in various directions in three-dimensional space, including the X, Y, and Z axis directions.

[0038] As an example, a cross section in the XY axis direction is shown in Fig. 3. The reticulated cell structure refers to a structure in which the cross sections of the cell wall skeletons 4 are spread out like a mesh when the cross section of the first foamed layer 21 is observed in any direction in the three-dimensional space, as shown in Fig. 3, and can also be said to be a structure in which multiple pores (spaces formed by cells 2) partitioned by the cross sections of the cell wall skeletons 4 are connected together.

[0039] The reticulated cell structure includes open cells 2a. Open cells 2a refer to a state in which the cell walls 3 separating the cells 2 have openings 6, so that the cells 2a1 communicate with adjacent cells 2a2, as shown in Figure 3; this state is also called broken cells. The openings 6 are the broken portions of the cell walls 3, which appear white in Figure 3. The cells 2a1 and 2a2 shown as examples in Figure 3 are both open cells and broken.

[0040] In the foam 1 according to this embodiment, the reticulated cell structure preferably further includes closed cells 2b, in which adjacent cells are not connected to each other. The inclusion of closed cells 2b allows the foam to have higher strength. Closed cells 2b refer to a state in which the cell walls 3 separating the cells 2 do not have openings 6, and the cells 2 form spaces independent of the surrounding cells 2.

[0041] In the foam 1 according to this embodiment, the foam layer 20 may further include a second foam layer 22 between the first non-foam layer 11 and the first foam layer 21. The second foam layer 22 has an island-in-sea structure 7 in which bubbles 2 are dispersed in a matrix 8 made of a molding material. FIG. 4 shows a slice image of the foam 1 in the thickness direction observed using an X-ray inspection device (μnRay7600F, manufactured by Matsusada Precision Co., Ltd.). The scale in the lower right corner of FIG. 4 indicates 0.25 mm. In FIG. 4, the white areas represent the matrix 8, and the black areas represent the bubbles 2. The second foam layer 22 is a layer of the foam layer 20 in which the degree of expansion of the bubbles 2 is small. Due to the small growth of the bubbles 2, the solid parts around the bubbles 2 remain in clumps, and islands of bubbles 2 are mixed in the sea of ​​the matrix 8 made of the molding material.

[0042] In this embodiment, it is preferable that the thickness of the first foam layer 21 is large, and the ratio of the thickness of the first foam layer 21 to the total thickness of the foam layer 20 is preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 100%. As the ratio of the thickness of the first foam layer 21 to the total thickness of the foam layer 20 increases, the differences in whiteness, chromaticity, and reflectance between the front and back can be almost eliminated, and the light-blocking performance of the foam 1 can be further improved.

[0043] As shown in FIG. 1 , the foam 1 according to this embodiment further includes a second non-foamed layer 12, and the foamed layer 20 is preferably located between the first non-foamed layer 11 and the second non-foamed layer 12. This ensures smoothness on both the front and back surfaces of the foam 1. The second non-foamed layer 12 is a layer that is substantially free of bubbles 2 and is generally referred to as a skin layer. The surface of the second non-foamed layer 12 preferably forms the surface opposite the first non-foamed layer 11 on either the front or back surface of the foam 1. The thickness of the second non-foamed layer 12 is not particularly limited, but is preferably 3 to 15%, more preferably 5 to 13%, of the total thickness of the foam 1. The thickness of the second non-foamed layer 12 is preferably equal to or thicker than the thickness of the first non-foamed layer 11.

[0044] The first non-foamed layer 11, the foamed layer 20, and the second non-foamed layer 12 are made of the same molding material and are laminated in the thickness direction (Z-axis direction) of the foam 1.

[0045] 1 shows a form in which the foam 1 is composed of the first non-foamed layer 11, the second foamed layer 22, the first foamed layer 21, and the second non-foamed layer 12, but the present invention is not limited to the form shown in Fig. 1 as long as it includes at least the first non-foamed layer 11 and the first foamed layer 21. For example, the foam 1 may be composed of only the first non-foamed layer 11 and the first foamed layer 21, or may be composed of only the first non-foamed layer 11, the second foamed layer 22, and the first foamed layer 21, or may be composed of only the first non-foamed layer 11, the first foamed layer 21, and the second non-foamed layer 12.

[0046] There may be no clear boundaries between the layers of the foam, and the structure may change continuously. In FIG. 1 , the boundary between the first non-foamed layer 11 and the second foamed layer 22, the boundary between the second foamed layer 22 and the first foamed layer 21, and the boundary between the first foamed layer 21 and the second non-foamed layer 12 are represented by dashed dotted lines. However, these dotted lines do not clearly indicate the boundaries, but merely show the approximate boundary positions. To give a specific example, near the boundary between the first non-foamed layer 11 and the second foamed layer 22, a region without bubbles and a region with a sea-island structure may coexist. Near the boundary between the second foamed layer 22 and the first foamed layer 21, a region with a sea-island structure and a region with a network-like cell structure may coexist. Near the boundary between the first foamed layer 21 and the second non-foamed layer 12, a region with a network-like cell structure and a region without bubbles may coexist.

[0047] In the foam 1 according to this embodiment, when the thickness of the foam 1 is 250 μm or more and 450 μm or less, the surface of the foam 1 opposite to the first non-foamed layer 11 side is subjected to CIE1976 L * a * b * When measuring the chromaticity coordinates of the color space, L * The value of is between 70 and 100, and a * The value of is between -1.0 and 0, and b * It is preferable that the value of is -2.0 or more and 0 or less. By setting it in such a range, the foam 1 can be visually recognized as being substantially white. When the foam 1 is used as the outer wall of a container, the contents of the container can be protected from light harmful to the contents, such as ultraviolet light. In this embodiment, when the foam 1 is used as the outer wall of a container, it is preferable that the surface of the foam 1 opposite to the first non-foamed layer 11 side is the outer surface of the container, and the surface of the foam 1 on the first non-foamed layer 11 side is the inner surface of the container. The L of the surface of the foam 1 opposite to the first non-foamed layer 11 side * The value of a on the surface of the foam 1 opposite to the first non-foamed layer 11 side is more preferably 80 or more and 90 or less. * The value of b on the surface of the foam 1 opposite to the first non-foamed layer 11 side is more preferably −0.5 or more and 0 or less. *It is more preferable that the value of L is not less than −0.9 and not more than 0. In the present embodiment, when the foam 1 has a bottle shape, * a * b * is the average value of the values ​​measured at three arbitrary points in the center of the bottle in the vertical direction. * a * b * is the average value of measurements taken at three arbitrary points in the center of the tray in the longitudinal direction.

[0048] When the thickness of the foam 1 is 250 μm or more and 450 μm or less, the surface of the foam 1 on the side of the first non-foamed layer 11 is subjected to CIE1976 L in accordance with JIS Z 8781-4:2013. * a * b * When measuring the chromaticity coordinates of the color space, L * The value of is between 45 and 100, and a * The value of is between -1.0 and 0, and b * It is preferable that the value of L is not less than −1.0 and not more than 0. * The value of a on the surface of the foam 1 on the side of the first non-foamed layer 11 is more preferably 70 or more and 80 or less. * The value of b on the surface of the foam 1 on the side of the first non-foamed layer 11 is more preferably −0.3 or more and 0 or less. * The value is more preferably −0.35 or more and 0 or less.

[0049] In the foam 1 according to this embodiment, the surface of the foam 1 on the non-foamed layer 11 side and the surface opposite to the first non-foamed layer 11 side are measured in accordance with CIE1976 L in accordance with JIS Z 8781-4:2013. * a * b * When the chromaticity coordinates of the color space were measured, the L * The value of L on the surface of the first non-foamed layer 11 side * or the value of L on the surface on the first non-foamed layer 11 side is the same as * and the value of a on the surface opposite to the first non-foamed layer 11 side is larger than the value of a* The value of a on the surface of the first non-foamed layer 11 side is * or the value of a on the surface of the first non-foamed layer 11 side is equal to the value of a * and the value of b on the surface opposite to the first non-foamed layer 11 side is smaller than the value of * The value of b on the surface of the first non-foamed layer 11 side is * or the value of b on the surface of the first non-foamed layer 11 side is the same as the value of b * As the thickness of the first foamed layer 21 increases, the L * The value of a * The value of b * and the value of L * The value of a * The value of b * When the entire foamed layer 20 is the first foamed layer 21, the difference between the L value of the surface opposite to the first non-foamed layer 11 side and the L value of the surface opposite to the first non-foamed layer 11 side tends to become smaller. * The value of a * The value of b * and the value of L * The value of a * The value of b * The value of the saturation voltage V is substantially the same as the value of the saturation voltage V. Here, "substantially the same" means that the difference is within the margin of error.

[0050] In the foam 1 according to this embodiment, when the thickness of the foam 1 is 250 μm or more and 450 μm or less, the D65 whiteness of the surface of the foam 1 opposite the first non-foamed layer 11, measured in accordance with ISO 2470-2:2008, is preferably 70 or more, more preferably 80 or more. When the foam is used as the outer wall of a container, the contents of the container can be protected from harmful light, such as ultraviolet rays. In this embodiment, when the foam 1 is in the shape of a bottle, the D65 whiteness is the average of values ​​measured at three arbitrary positions in the vertical center of the bottle. Furthermore, when the foam 1 is in the shape of a tray, the D65 whiteness is the average of values ​​measured at three arbitrary positions in the longitudinal center of the tray.

[0051] The D65 whiteness of the surface on the first non-foamed layer 11 side is preferably 35 or more, and more preferably 45 or more.

[0052] The foam 1 according to this embodiment includes an embodiment in which, when the D65 brightness of the surface of the foam 1 facing the first non-foamed layer 11 and the surface opposite the first non-foamed layer 11 are measured in accordance with ISO 2470-2:2008, the D65 brightness of the surface opposite the first non-foamed layer 11 is the same as or greater than the D65 brightness of the surface facing the first non-foamed layer 11. The difference in D65 brightness from the surface facing the first non-foamed layer 11 is preferably 0 to 35, and more preferably 0 to 25. As the thickness of the first foamed layer 21 increases, the difference in D65 brightness between the surface opposite the first non-foamed layer 11 and the surface facing the first non-foamed layer 11 tends to decrease. When the entire foam layer 20 is the first foam layer 21, the D65 whiteness value of the surface opposite the first non-foamed layer 11 side is substantially the same as the D65 whiteness value of the surface on the first non-foamed layer 11 side. Here, "substantially the same" means that the difference is within the margin of error.

[0053] When the reflectance of the surface of the foam of the present invention opposite the first non-foamed layer is measured in accordance with JIS R 3106:2019 "Test Methods for Transmittance, Reflectance, and Emissivity of Flat Glass and Calculation Method for Solar Heat Gain Coefficient of Architectural Flat Glass," the reflectance value at a wavelength of 390 nm on the surface opposite the first non-foamed layer is preferably 70% or more, more preferably 75% or more. When the foam 1 is used as the outer wall of a container, it can protect the contents of the container from harmful light, such as ultraviolet rays. In this embodiment, when the foam 1 is bottle-shaped, the reflectance is the average value of values ​​measured at three arbitrary positions in the vertical center of the bottle. Furthermore, when the foam 1 is tray-shaped, the reflectance is the average value of values ​​measured at three arbitrary positions in the longitudinal center of the tray.

[0054] In the foam of this embodiment, when the reflectance is measured on the surface of the foam facing the first non-foamed layer and the surface opposite the first non-foamed layer in accordance with JIS R 3106:2019 "Test methods for transmittance, reflectance, and emissivity of plate glass and calculation method for solar heat gain coefficient of architectural plate glass," the reflectance value at wavelengths of 240 to 800 nm on the surface opposite the first non-foamed layer is the same as the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer, or is greater than the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer, and is preferably within a range of 0 to 20%, more preferably within a range of 0 to 5%, of the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer.

[0055] The reflectance value at wavelengths of 240 to 2600 nm on the surface opposite the first non-foamed layer 11 side is preferably within the range of 0 to 20%, and more preferably within the range of 0 to 5%, of the reflectance value at wavelengths of 240 to 2600 nm on the surface on the first non-foamed layer 11 side.

[0056] In the foam according to this embodiment, when the thickness of foam 1 is 250 μm or more and 450 μm or less, the transmittance of foam 1 for light in the wavelength range of 480 to 500 nm is preferably 15% or less, more preferably 10 to 12%. When foam 1 is used as the outer wall of a container, it can protect the contents of the container from harmful light such as ultraviolet light. In this embodiment, when foam 1 is bottle-shaped, the light transmittance is a value measured at least one arbitrary position at the center of the bottle in the vertical direction. Furthermore, when foam 1 is tray-shaped, the light transmittance is a value measured at least one arbitrary position at the center of the tray in the longitudinal direction.

[0057] The foam 1 according to this embodiment preferably has a gas barrier film on at least one of the surface facing the first non-foamed layer 11 and the surface opposite the first non-foamed layer 11. When the foam 1 is used as the outer wall of a container, deterioration of the contents of the container can be prevented. The gas barrier film is not particularly limited and may be any of various known coating layers, such as a diamond-like carbon (DLC) film or various vapor deposition films. The gas barrier film may be provided only on the surface facing the first non-foamed layer 11, only on the surface opposite the first non-foamed layer 11, or on both the surface facing the first non-foamed layer 11 and the surface opposite the first non-foamed layer 11. The gas barrier film is preferably provided on either or both the surface of the first non-foamed layer 11 and the surface of the second non-foamed layer 12. When forming a vapor deposition film as the gas barrier film, for example, by vapor deposition on the surfaces of the non-foamed layers 11 and 12, thermal stress can be reduced. Furthermore, the non-foamed layers 11 and 12 have high smoothness, so that the gas barrier performance of the gas barrier film can be exhibited without being impaired.

[0058] In this embodiment, the intrinsic viscosity of the thermoplastic resin is not particularly limited as long as it is within a range suitable for molding. However, taking into consideration the ease of cell collapse, it is preferable to select a resin with a lower intrinsic viscosity from among those having an intrinsic viscosity suitable for molding into containers such as bottles and trays. In the foam according to this embodiment, the thermoplastic resin is a polyethylene terephthalate resin, and embodiments in which the intrinsic viscosity of the polyethylene terephthalate resin is 0.63 to 0.86 dL / g are included. The intrinsic viscosity of the polyethylene terephthalate resin is more preferably 0.63 to 0.82 dL / g. When the foam is a container such as a bottle or a tray, the intrinsic viscosity of the polyethylene terephthalate resin is the intrinsic viscosity measured on a piece cut out from the container.

[0059] A container according to this embodiment has the foam 1 according to this embodiment as an outer wall. The foam 1 according to this embodiment is suitable for use as the outer wall of a container. The container is not particularly limited, but examples thereof include bottles and trays. When the container is a bottle, the volume of the bottle is preferably 50 to 3,000 ml, more preferably 50 to 500 ml, and even more preferably 60 to 150 ml. The contents are not particularly limited, but are preferably substances that are susceptible to quality deterioration due to light such as ultraviolet light, such as beer or cosmetic emulsion.

[0060] The container according to this embodiment includes a configuration in which the first non-foamed layer 11 is disposed on the inner surface side of the container, and the foamed layer 20 is disposed on the outer surface side of the container relative to the first non-foamed layer 11. When the foam 1 further includes a second non-foamed layer 12, it is preferable that the second non-foamed layer 12 is disposed on the outer surface side of the container.

[0061] The foamed preform 100 according to this embodiment is a foamed preform molded from a molding material containing a thermoplastic resin, and has a first non-foamed layer 111 and a pre-foamed layer 120 as shown in FIG. 5. The pre-foamed layer 120 has a plurality of spherical foamed cells 102 as shown in FIG. 6. The particle size distribution based on the number of the spherical foamed cells 102 has a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm.

[0062] The foam preform 100 is preferably, for example, a hot parison or cold parison for blow molding. The shape of the foam preform 100 is not particularly limited, but for example, when the foam 1 is a bottle, it is a cylindrical shape with a bottom, and when the foam 1 is a tray, it is a disk shape or a bowl shape.

[0063] The first non-foamed layer 111 is a layer that becomes the first non-foamed layer 11 in the foam 1, and does not substantially contain the spherical foam cells 102. The surface of the first non-foamed layer 111 preferably forms the inner surface of the foamed preform 100.

[0064] The pre-foamed layer 120 is a layer that will become the foamed layer 20 in the foam 1, and contains dispersed spherical foam cells 102. The spherical foam cells 102 are substantially spherical and contain gas. A matrix 103 made of the molding material surrounds the spherical foam cells 102. As shown in FIG. 6, the pre-foamed layer 120 contains spherical foam cells 102 of various diameters.

[0065] In the pre-foamed layer 120, the particle size distribution based on the number of spherical foam cells 102 has a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm. The distribution width is more preferably 60 μm or more. The upper limit of the distribution width is not particularly limited, but is preferably 80 μm or less, more preferably 75 μm or less. The mode diameter is more preferably 52 to 58 μm. Having a broad particle size distribution, i.e., a wide distribution width within the above-mentioned range, allows the first foamed layer 21 to be formed, including broken cells, in the foam 1 obtained by blow molding the foamed preform 100. On the other hand, having a sharp particle size distribution, such as a distribution width of less than 52 μm, results in a foamed layer without broken cells, as in Patent Document 1, which has a grayish appearance with low whiteness and does not achieve the desired light-blocking performance. The particle size distribution is measured as follows. A predetermined position of the foamed preform 100 is cut into 10 mm squares, frozen, and cut with a diamond knife to obtain an observation cross section. The observation cross section is observed using a reflected light microscope at a magnification of 200x. The number and individual diameter of spherical foam cells present in the observation image are measured to determine the particle size distribution. The observation position is not particularly limited, but for example, if the foamed product 1 is a bottle, it is preferably at the vertical center of the body after molding, and if the foamed product 1 is a tray, it is preferably at the longitudinal center of the tray after molding.

[0066] 5, the foamed preform 100 preferably further comprises a second non-foamed layer 112 in addition to the first non-foamed layer 111 and the pre-foamed layer 120. The second non-foamed layer 112 is a layer that becomes the second non-foamed layer 12 in the foamed body 1, and does not substantially contain spherical foam cells 102. The surface of the second non-foamed layer 112 preferably forms the outer surface of the foamed preform 100.

[0067] The structure may change continuously without any clear boundaries between the layers of the foamed preform 100. In Fig. 5, the boundary line between the first non-foamed layer 111 and the pre-foamed layer 120 and the boundary line between the pre-foamed layer 120 and the second non-foamed layer 112 are shown by dashed dotted lines, but these do not indicate clear boundaries but merely show rough boundary positions.

[0068] In the foamed preform according to this embodiment, the particle size distribution based on the number of the spherical foam cells 102 includes a form in which the mode diameter is larger than the average diameter. A mode diameter larger than the average diameter means that there are many spherical foam cells 102 that have grown to large particle sizes. The average diameter is the number-average particle diameter determined by measuring the particle size distribution described above. The value of the mode diameter is preferably 5% to 35% of the value of the average diameter, and more preferably 7% to 34%.

[0069] In the particle size distribution based on the number of the spherical foam cells 102, the standard deviation is preferably 10 to 15 μm, and more preferably 11 to 12 μm.

[0070] The method for producing the foam 1 according to this embodiment includes a step of preparing a bottomed, cylindrical non-foamed preform, which is a molded product of a molding material containing a thermoplastic resin, impregnated with an inert gas, and in an unfoamed state; a foaming step of converting the non-foamed preform into a foamed preform; and a blow molding step of blow molding the foamed preform into a foam. The foaming step includes a heating step of heating the non-foamed preform from the outer surface side to obtain an intermediate body, and a blow molding step of conducting heat unevenly distributed on the outer surface side of the intermediate body after the heating step to the inner surface side to form a foam between the outer surface and the inner surface of the intermediate body. and a waiting process for reducing the temperature difference. The blow molding process is a process for forming a foam 1 having a first non-foamed layer 11 and a foamed layer 20 as shown in Figures 1 to 3, in which the foamed layer 20 includes a first foamed layer 21 having a plurality of cells 2 arranged three-dimensionally and a cell wall skeleton 4 separating adjacent cells 2, and the first foamed layer 21 has a reticulated cell structure 5 in which the cell wall skeleton 4 has a reticulated cross section, and the reticulated cell structure 5 includes open cells in which adjacent cells 2 communicate with each other via openings 6 provided in the cell wall skeleton 4.

[0071] The preparation step is a step of preparing a non-foamed preform. The non-foamed preform is substantially in a non-foamed state. The method for producing a non-foamed preform is not particularly limited, and preferably includes, for example, the steps of heating a molding material to form a resin melt, impregnating the resin melt with an inert gas, and filling a molding die with the inert gas-impregnated resin melt and performing injection molding while applying pressure to the resin melt in the molding die and maintaining the pressure. The inert gas is not particularly limited, and may be, for example, nitrogen gas or carbon dioxide gas. The non-foamed preform may be a preform already prepared as an inert gas-impregnated preform. The method for impregnating the resin melt with an inert gas is not particularly limited, and may include a method of injecting an inert gas converted into a supercritical fluid under high pressure into the resin melt to dissolve it, or a method of adjusting the filling rate of the resin melt and supplying an inert gas into a cylinder at a pressure lower than the cylinder pressure to dissolve it. The latter method can achieve a foamed state similar to that of the former method even at a low supply pressure by bringing the amount of gas dissolved close to the saturated concentration.

[0072] The foaming process is a process in which the inert gas impregnated inside the non-foamed preform is expanded to form spherical foam cells 102. The foaming process includes a heating process in which the non-foamed preform is heated from the outer surface side to obtain an intermediate body, and a waiting process in which the heat unevenly distributed on the outer surface side of the intermediate body after the heating process is conducted to the inner surface side to reduce the temperature difference between the outer surface and the inner surface of the intermediate body.

[0073] In the heating step, heating is preferably performed at a temperature equal to or higher than the glass transition point of the thermoplastic resin contained in the molding material. For example, when the thermoplastic resin is PET, the heating temperature is preferably 90 to 130°C, and more preferably 100 to 120°C. Here, the heating temperature refers to the temperature of the outer surface of the non-foamed preform or intermediate. The heating time is not particularly limited, but is preferably 5 to 20 seconds, and more preferably 10 to 15 seconds. The intermediate is a foamed preform precursor after the heating step and before the waiting step.

[0074] The waiting step is a step in which heat unevenly distributed on the outer surface side of the intermediate body during the heating step is transferred to the inner surface side by thermal conduction. This allows the spherical foam cells to grow sufficiently throughout the entire thickness direction of the foamed preform, resulting in a broad particle size distribution of the spherical foam cells not only on the side close to the outer surface of the foamed preform but also on the side close to the inner surface. While it is preferable not to input heat during the waiting step, it may be performed while residual heat from the heating step remains, or after inputting a small amount of heat. The residual heat or a small amount of heat input slows the rate at which the outer surface temperature of the preform drops. The waiting step allows heat to be transferred to the inner surface of the preform, thereby further improving the stability of the stretch molding. The waiting time during the waiting step is not particularly limited, but is preferably 5 to 20 seconds, more preferably 10 to 15 seconds.

[0075] In the foam manufacturing method according to the present embodiment, the foaming step is preferably a step of performing one cycle, consisting of a heating step and a waiting step, two or more times. By performing the heating step and waiting step multiple times, bubbles can be grown throughout the entire thickness direction of the intermediate body, thereby further reducing the difference in bubble size between the side closer to the outer surface and the side closer to the inner surface of the intermediate body. By performing one cycle of the heating step and waiting step two or more times, the temperature difference between the outer and inner surfaces of the foamed preform can be reduced in a short time while preventing deformation due to softening of the foamed preform, promoting foaming and achieving a broad particle size distribution of spherical foam cells over a wide range in the thickness direction of the preform. Furthermore, by conducting heat applied to the outer surface of the preform to the inner surface, the stability of stretch moldability can be improved and whitening can be suppressed. When one cycle is performed two or more times, the heating temperature and heating time of each heating step may be the same or different from each other, and the temperature and waiting time of each waiting step may be the same or different from each other. When one cycle is repeated two or more times, it is more preferable to shorten the waiting time each time, which can promote foaming and further improve the stability of the stretch molding.

[0076] When one cycle of the heating step and the waiting step is performed only once, it is preferable to perform the heating while cooling the outer surface of the intermediate body with air, which allows the heat from the outer surface to be conducted to the inner surface while preventing whitening, thereby allowing the outer and inner surfaces to be heated more uniformly.

[0077] In the foam manufacturing method according to this embodiment, the foaming step is a step of forming a foam preform 100 having a first non-foamed layer 111 and a pre-foamed layer 120 as shown in FIG. 5, and the pre-foamed layer 120 has a plurality of spherical foam cells 102 as shown in FIG. 6. The number-based particle size distribution of the spherical foam cells 102 preferably has a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm. This facilitates the formation of open cells 2a in the first foamed layer 21 in the resulting foam 1. The resulting foam preform may further have a second non-foamed layer 112 as shown in FIG. 5.

[0078] The blow molding step can be performed by a known method. The foam obtained by blow molding the foam preform that has been subjected to the foaming step described above has a first foam layer having a reticulated cell structure as shown in FIG.

[0079] Conventionally, blow molding is performed without a waiting period after heating in the foaming step. If blow molding is performed without a waiting period after heating, the spherical foam cells of the preform do not grow sufficiently, resulting in blow molding with multiple spherical cells having a substantially uniform particle size, i.e., a sharp particle size distribution. As a result, the resulting foam has a foam layer without broken cells, and the desired light-blocking performance is not achieved. In contrast, in the manufacturing method of the foam 1 according to the present embodiment, a waiting period is provided after heating in the foaming step, allowing spherical foam cells to grow throughout the entire thickness of the preform. More specifically, as shown in FIG. 6 , during the waiting period, previously generated spherical foam cells grow larger, while new spherical foam cells emerge and grow from the gaps between these grown spherical foam cells. It is believed that this mechanism results in the production of a preform with a broad particle size distribution. When such a preform is blow molded, a foam layer with broken cells is formed, thereby significantly improving the light-blocking performance of the foam 1. [Example]

[0080] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Furthermore, "parts" and "%" in the examples represent "parts by mass" and "% by mass", respectively, unless otherwise specified. The number of added parts is a value calculated on a solid content basis.

[0081] Example 1 A bottomed, cylindrical, unfoamed preform was prepared using PET resin (intrinsic viscosity: 0.76 dl / g), which was impregnated with nitrogen gas to a nearly saturated state but was not foamed. The unfoamed preform was heated at 100 to 120°C for 18 seconds using an infrared heater (first heating step), and then left unheated for 10 seconds to obtain an intermediate (first waiting step). The obtained intermediate was then heated at 100 to 120°C for 18 seconds using an infrared heater (second heating step), and then left unheated for 3 seconds to obtain a foamed preform (second waiting step). The obtained foamed preform was then blow-molded to obtain a foamed bottle with a volume of 500 ml.

[0082] (Comparative Example 1) An unfoamed preform similar to that of Example 1 was heated at 100 to 120°C for 18 seconds using an infrared heater to form a foamed preform, which was then immediately blow-molded to obtain a foamed bottle with a volume of 500 ml.

[0083] (Cross-section observation of foam preform) For the foamed preforms of Example 1 and Comparative Example 1, a cross section at the center of the bottle in the vertical direction after molding was observed at 200x magnification using an optical microscope (model: Eclipse LV100ND, manufactured by Nikon Corporation) to measure the particle size distribution of the spherical foam cells. In Example 1, the distribution width was 75 μm, the mode diameter was 55 μm, and the average diameter was 46 μm. In Comparative Example 1, the distribution width was 40 μm, the mode diameter was 40 μm, and the average diameter was 40 μm.

[0084] (Observation of the appearance of the foam bottle) The appearances of the foamed bottles of Example 1 and Comparative Example 1 were compared. As a result, the foamed bottle of Example 1 was white, whereas the foamed bottle of Comparative Example 1 was grayish. Furthermore, when a region including the center in the vertical direction of the foamed bottle was cut out and viewed through the glass, Example 1 had less light transmittance than Comparative Example 1.

[0085] (L * a * b * (chromaticity coordinate measurement of color space) The foamed bottle of Example 1 was measured using a spectrophotometer and color difference meter (PF-7000, manufactured by Nippon Denshoku Industries Co., Ltd.). * a * b * The chromaticity coordinates of the color space and the D65 whiteness were measured. The measurement position was the center position in the vertical direction of the bottle, and measurements were taken at three points. As a result, on the outer surface of the bottle, * The values ​​were 87.14, 86.83, and 87.05, respectively, with an average value of 87.00. * The values ​​are -0.23, -0.25, and -0.25, respectively, with an average value of -0.24. * The values ​​were -1.09, -1.19, and -1.17, respectively, with an average of -1.15, and the D65 whiteness was 71.55, 71.03, and 71.45, respectively, with an average of 71.34. On the inner surface of the bottle, L * The values ​​were 73.17, 72.92, and 73.44, respectively, with an average value of 73.18. * The values ​​are -0.18, -0.18, and -0.17, respectively, with an average value of -0.18. * The values ​​were -0.34, -0.34, and -0.39, respectively, with an average of -0.36, and the D65 whiteness was 45.76, 45.38, and 46.21, respectively, with an average of 45.78.

[0086] (reflectance) The reflectance of the foamed bottle of Example 1 was measured using an ultraviolet-visible-near-infrared spectrophotometer (UH4150, manufactured by Hitachi High-Technologies Corporation). The measurement position was the center position in the vertical direction of the bottle, and measurements were taken at three locations. As a result, over the entire measurement area, the reflectance of the outer surface of the bottle was the same as or greater than the reflectance of the inner surface of the bottle, and was within a range of 20% of the reflectance of the inner surface of the bottle. The measurement conditions were as follows: Measurement range: 240~2600nm Measurement method: Reflection method Reference: Aluminum oxide standard white plate Detector: Integrating sphere / photomultiplier tube (240-850nm), Integrating sphere / PbS (850-2600nm) Detector switching wavelength: 850nm Light source switching wavelength: 340nm Sampling interval: 1.00 nm Scan speed: 300nm / min Slit width: 6.00 nm (fixed)

[0087] (Light transmittance) The light transmittance of the foamed bottle of Example 1 was measured using a spectrophotometer (U-3900, manufactured by Hitachi High-Technologies Corporation). The measurement was performed at one location, which was the center position in the vertical direction of the bottle. As a result, the light transmittance at a wavelength of 500 nm was 12.9%.

[0088] (Cross-section observation of foam bottle) For the foamed bottle of Example 1, a cross section in the thickness direction and a cross section perpendicular to the thickness direction were observed at a magnification of 22x using an X-ray transmission inspection device (μnRay7600F, manufactured by Matsusada Precision Co., Ltd.). A cross-sectional image in the thickness direction is shown in FIG. 7, and a cross section perpendicular to the thickness direction is shown in FIG. 8. In FIG. 7, the right side of the paper is the outer surface side of the bottle, and the left side of the paper is the inner surface side of the bottle. As shown in FIG. 7, the foamed bottle had a second non-foamed layer on the outer surface side of the bottle and a first non-foamed layer on the inner surface side of the bottle, and a foamed layer was present between the first non-foamed layer and the second non-foamed layer. The second non-foamed layer was thicker than the first non-foamed layer. As shown in FIGS. 8(a) and 8(d), the second non-foamed layer and the first non-foamed layer were bubble-free. As shown in FIG. 8(b), the first foamed layer had a network-like bubble structure. As shown in FIG. 8(c), the second non-foamed layer had a sea-island structure. In addition, a foamed bottle with a volume of 100 ml was produced as a foam in the same manner as in Example 1. The cross-sectional state of the foamed bottle with a volume of 100 ml had the same structure as that of the foamed bottle of Example 1.

[0089] (Additional Note) A part or all of the above-described embodiments can be described as, but not limited to, the following additional notes. (Note 1) The foam according to the present invention is a molded product made from a molding material containing a thermoplastic resin, and the foam comprises a first non-foamed layer and a foamed layer. The foamed layer comprises a first foamed layer having a plurality of cells arranged three-dimensionally and a cell wall skeleton separating adjacent cells. The first foamed layer is characterized in that the cell wall skeleton has a reticulated cell structure with a reticulated cross section, and the reticulated cell structure includes open cells in which adjacent cells communicate with each other via openings provided in the cell wall skeleton. (Appendix 2) In the foamed product according to the present invention, the foamed layer may further include a second foamed layer between the first non-foamed layer and the first foamed layer, the second foamed layer having an islands-in-a-sea structure in which bubbles are dispersed in a matrix made of the molding material. (Note 3) The foam according to the present invention preferably further comprises a second non-foamed layer, the second non-foamed layer being between the first non-foamed layer and the second non-foamed layer, thereby ensuring smoothness on both the front and back surfaces of the foam. (Note 4) In the foam according to the present invention, the reticulated cell structure preferably further includes closed cells in which adjacent cells are not connected to each other, which can result in a foam with higher strength. (Appendix 5) In the foam according to the present invention, when the thickness of the foam is 250 μm or more and 450 μm or less, the surface of the foam opposite to the first non-foamed layer side is subjected to CIE1976 L * a * b * When measuring the chromaticity coordinates of the color space, L * The value of is between 70 and 100, and a * The value of is between -1.0 and 0, and b * It is preferable that the value is −2.0 or more and 0 or less. When the foam is used as the outer wall of a container, the light blocking properties can be further improved. (Appendix 6) In the foam according to the present invention, the surface of the foam on the side of the first non-foamed layer and the surface opposite to the first non-foamed layer are measured to have a viscosity of 1000 MPa or less in accordance with CIE1976 L in accordance with JIS Z 8781-4:2013. * a * b * When the chromaticity coordinates of the color space are measured, the L * The value of L on the surface of the first non-foamed layer side * or the value of L * and the value of a on the surface opposite to the first non-foamed layer side is larger than the value of a * The value of a on the surface of the first non-foamed layer side is * or the value of a on the surface of the first non-foamed layer side is the same as the value of a * is smaller than the value of b on the surface opposite to the first non-foamed layer side, * The value of b on the surface of the first non-foamed layer side * or the value of b on the surface of the first non-foamed layer side is the same as the value of * It includes forms where the value is less than . (Appendix 7) In the foam according to the present invention, when the thickness of the foam is 250 μm or more and 450 μm or less, the D65 brightness of the surface of the foam opposite the first non-foamed layer side, measured in accordance with ISO 2470-2:2008, is preferably 70 or more. When the foam is used as the outer wall of a container, the light-blocking properties can be further improved. (Appendix 8) The foam of the present invention includes a form in which, when D65 brightness is measured in accordance with ISO2470-2:2008 for the surface of the foam facing the first non-foamed layer and the surface opposite the first non-foamed layer, the D65 brightness value of the surface opposite the first non-foamed layer is the same as the D65 brightness value of the surface facing the first non-foamed layer or is greater than the D65 brightness value of the surface facing the first non-foamed layer. (Appendix 9) The foam of the present invention includes a form in which, when the reflectance of the surface of the foam facing the first non-foamed layer and the surface opposite the first non-foamed layer is measured in accordance with JIS R 3106:2019 "Test methods for transmittance, reflectance, and emissivity of plate glass and calculation method for solar heat gain coefficient of architectural plate glass," the reflectance value at wavelengths of 240 to 800 nm on the surface opposite the first non-foamed layer is the same as the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer, or is greater than the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer, and is within a range of 0 to 20% of the reflectance value at wavelengths of 240 to 800 nm on the surface facing the first non-foamed layer. (Note 10) When the foam according to the present invention has a thickness of 250 μm or more and 450 μm or less, the transmittance of the foam for light in the wavelength range of 480 to 500 nm is preferably 15% or less. When the foam is used as the outer wall of a container, the light-blocking properties can be further improved. (Note 11) The foam according to the present invention preferably has a gas barrier film on at least one of the surface on the first non-foamed layer side and the surface opposite to the first non-foamed layer side. When the foam is used as the outer wall of a container, deterioration of the contents of the container can be prevented. (Appendix 12) The foam according to the present invention includes an embodiment in which the thermoplastic resin is a polyethylene terephthalate resin, and the intrinsic viscosity of the polyethylene terephthalate resin is 0.63 to 0.86 dl / g. (Appendix 13) A container according to the present invention is characterized by having the foam according to the present invention as an outer wall. (Appendix 14) The container according to the present invention includes a configuration in which the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer. (Appendix 15) The foamed preform according to the present invention is a foamed preform that is a molded product of a molding material containing a thermoplastic resin, the foamed preform having a first non-foamed layer and a pre-foamed layer, the pre-foamed layer having a plurality of spherical foam cells, and the number-based particle size distribution of the spherical foam cells having a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm. (Appendix 16) The foamed preform according to the present invention includes a form in which the mode diameter is larger than the average diameter in the particle size distribution based on the number of the spherical foamed cells. (Appendix 17) A method for producing a foamed body according to the present invention includes a step of preparing a bottomed, cylindrical non-foamed preform, which is a molded product of a molding material containing a thermoplastic resin and is impregnated with an inert gas and is in an unfoamed state; a foaming step of converting the non-foamed preform into a foamed preform; and a blow molding step of blow molding the foamed preform into a foamed body, wherein the foaming step includes a heating step of heating the non-foamed preform from the outer surface side to obtain an intermediate body; and a blow molding step of conducting heat unevenly distributed on the outer surface side of the intermediate body after the heating step to the inner surface side to obtain the foamed body. and a waiting step of reducing the temperature difference between the outer surface and the inner surface of the intermediate body, wherein the blow molding step is a step of forming a foam comprising a first non-foamed layer and a foamed layer, the foamed layer having a plurality of cells arranged three-dimensionally and a cell wall skeleton separating adjacent cells, wherein the first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, and the reticulated cell structure includes open cells in which adjacent cells communicate with each other via openings provided in the cell wall skeleton. (Appendix 18) In the method for producing a foam according to the present invention, the foaming step is preferably a step in which one cycle consisting of the heating step and the waiting step is performed two or more times. By performing the heating step and the waiting step multiple times, it is possible to grow bubbles throughout the entire thickness of the intermediate body and further reduce the difference in bubble size between the side near the outer surface and the side near the inner surface of the intermediate body. (Appendix 19) In the method for producing a foamed product according to the present invention, the foaming step is a step of forming a foamed preform having a first non-foamed layer and a pre-foamed layer as the foamed preform, the pre-foamed layer having a plurality of spherical foam cells, and the number-based particle size distribution of the spherical foam cells preferably has a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm. This facilitates the formation of open cells in the first foamed layer in the obtained foamed product. [Explanation of symbols]

[0090] 1. Foam 2,2a1,2a2 bubbles 2a Open cell 2b Closed bubble 4. Bubble wall skeleton 5. Reticulated bubble structure 6 aperture 7 Sea-island structure 8. Matrix 11 First non-foamed layer 12 Second non-foamed layer 20 Foam layer 21 First foam layer 100 Foam preform 102 Spherical foam cells 103 Matrix 111 First non-foamed layer 112 Second non-foamed layer 120 Pre-foam layer

Claims

1. A container having, as an outer wall, a foamed body which is a molded product of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), The foam has a first non-foamed layer and a foamed layer, the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer, the foamed layer includes a first foamed layer having a plurality of bubbles arranged three-dimensionally and a bubble wall skeleton separating adjacent bubbles, and a second foamed layer between the first non-foamed layer and the first foamed layer, the first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings provided in the cell wall skeleton, and the open cells are broken at the openings; the second foam layer has a sea-island structure in which a plurality of islands of bubbles are dispersed in a sea of ​​the molding material as a matrix, A container characterized in that the length of the cells of the second foam layer in the surface direction of the outer wall is shorter than the length of one of the adjacent cells that constitute the continuous cells of the first foam layer.

2. A container having, as an outer wall, a foamed body which is a molded product of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), The foam has a first non-foamed layer and a foamed layer, the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer, the foam layer includes a first foam layer having a plurality of cells randomly arranged in three-dimensional directions and a cell wall skeleton separating adjacent cells, the first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings provided in the cell wall skeleton, and closed cells in which adjacent cells do not communicate with each other, and in the open cells, the cells are broken at the openings, the open cells and the closed cells are present in the same cross section in the surface direction of the outer wall, A container characterized in that the total length of the cells constituting the open cells in the same cross section is greater than the length of the closed cells.

3. 3. The container according to claim 2, wherein the foam layer further includes a second foam layer between the first non-foam layer and the first foam layer, the second foam layer having an islands-in-a-sea structure in which bubbles are dispersed in a matrix made of the molding material.

4. The foam further comprises a second non-foamed layer; 4. The container according to claim 1, wherein the foamed layer is located between the first non-foamed layer and the second non-foamed layer.

5. The first foamed layer further includes closed bubbles at a boundary portion between the second non-foamed layer and the first foamed layer, 5. The container according to claim 4, wherein the length of the closed cells present at the boundary portion in the surface direction of the outer wall is shorter than the length of one of the adjacent cells that make up the continuous cells.

6. 2. The container according to claim 1, wherein the reticulated cell structure further includes closed cells in which adjacent cells are not connected to each other.

7. When the thickness of the foam is 250 μm or more and 450 μm or less, the surface of the foam opposite to the first non-foamed layer side is subjected to a CIE1976 L ＊ a ＊ b ＊ When the chromaticity coordinates of the color space are measured, L ＊ The value of is 70 or more and 100 or less, and a ＊ The value of is -1.0 or more and 0 or less, and b ＊ The container according to any one of claims 1 to 3, characterized in that the value of is -2.0 or more and 0 or less.

8. The surface of the foam on the first non-foamed layer side and the surface opposite to the first non-foamed layer side are measured according to CIE1976 L in accordance with JIS Z 8781-4:2013. ＊ a ＊ b ＊ When measuring the chromaticity coordinates of the color space, L on the surface opposite to the first non-foamed layer side ＊ The value of L ＊ or the value of L ＊ is greater than the value of a on the surface opposite to the first non-foamed layer side ＊ The value of a on the surface of the first non-foamed layer side is ＊ or the value of a on the surface of the first non-foamed layer side is the same as the value of a ＊ is smaller than the value of b on the surface opposite to the first non-foamed layer side ＊ The value of b on the surface of the first non-foamed layer side ＊ or the value of b on the surface of the first non-foamed layer side ＊ 4. The container according to claim 1, wherein the value of

9. The container according to any one of claims 1 to 3, characterized in that when the thickness of the foam is 250 μm or more and 450 μm or less, the D65 whiteness of the surface of the foam opposite the first non-foamed layer side measured in accordance with ISO 2470-2:2008 is 70 or more.

10. When the D65 brightness of the surface of the foam on the first non-foamed layer side and the surface opposite to the first non-foamed layer side was measured in accordance with ISO 2470-2:2008, A container as described in any one of claims 1 to 3, characterized in that the D65 whiteness value of the surface opposite to the first non-foamed layer side is the same as or greater than the D65 whiteness value of the surface on the first non-foamed layer side.

11. When the reflectance of the surface of the foam on the first non-foamed layer side and the surface opposite to the first non-foamed layer side was measured in accordance with JIS R 3106:2019 "Test methods for transmittance, reflectance, and emissivity of plate glass and calculation methods for solar heat gain coefficient of architectural plate glass," The container according to any one of claims 1 to 3, characterized in that the reflectance value at wavelengths of 240 to 800 nm of the surface opposite to the first non-foamed layer side is the same as the reflectance value at wavelengths of 240 to 800 nm of the surface on the first non-foamed layer side, or is greater than the reflectance value at wavelengths of 240 to 800 nm of the surface on the first non-foamed layer side, and is within a range of 0 to 20% of the reflectance value at wavelengths of 240 to 800 nm of the surface on the first non-foamed layer side.

12. A container described in any one of claims 1 to 3, characterized in that when the thickness of the foam is 250 μm or more and 450 μm or less, the transmittance of the foam for light in the wavelength range of 480 to 500 nm is 15% or less.

13. The container according to any one of claims 1 to 3, characterized in that the foam has a gas barrier film on at least one of the surface on the first non-foamed layer side and the surface opposite to the first non-foamed layer side.

14. the thermoplastic resin is a polyethylene terephthalate resin, 4. The container according to claim 1, wherein the polyethylene terephthalate resin has an intrinsic viscosity of 0.63 to 0.86 dl / g.

15. In a foamed preform which is a molded product of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), The foam preform has a first non-foamed layer and a pre-foamed layer, The pre-foamed layer has a plurality of spherical foam cells, the particle size distribution of the spherical foam cells based on the number thereof is broad with a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm; The distribution width is a width of a frequency distribution graph of a particle size distribution obtained under the following condition 1. Condition 1: The particle size distribution is determined by observing the cross section of the foamed preform at a magnification of 200 times using a reflected light microscope and measuring the number and diameter of each of the spherical foam cells present in the observed image.

16. 16. The foam preform according to claim 15, wherein the mode diameter is larger than the average diameter in the particle size distribution based on the number of the spherical foam cells.

17. A container that is a blow-molded product of the foam preform according to claim 15 or 16, the outer wall of the container has a first non-foamed layer and a foamed layer; the first non-foamed layer of the foamed preform is a layer that will become the first non-foamed layer of the outer wall of the container, the pre-foamed layer of the foamed preform is a layer that will become the foamed layer of the outer wall of the container, the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer, the foam layer includes a first foam layer having a plurality of cells randomly arranged in three-dimensional directions and a cell wall skeleton separating adjacent cells, the first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, The container is characterized in that the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings provided in the cell wall skeleton, and in the open cells, the cells are broken at the openings.

18. A step of preparing a bottomed, cylindrical non-foamed preform, which is a molded product made of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), impregnated with an inert gas, and in a non-foamed state; a foaming step of converting the non-foamed preform into a foamed preform; a blow molding step of blow molding the foam preform to form a foam; Including, the foaming step includes a heating step of heating the non-foamed preform from its outer surface side to obtain an intermediate body, and a waiting step of conducting heat unevenly distributed on the outer surface side of the intermediate body after the heating step to its inner surface side to reduce the temperature difference between the outer surface and the inner surface of the intermediate body, the blow molding step is a step of forming a container having the foam as an outer wall, the foam has a first non-foamed layer and a foamed layer, the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer, the foamed layer includes a first foamed layer having a plurality of cells arranged three-dimensionally and a cell wall skeleton separating adjacent cells, and a second foamed layer between the first non-foamed layer and the first foamed layer, the first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings formed in the cell wall skeleton, and the open cells are broken at the openings; the second foam layer has a sea-island structure in which a plurality of islands of bubbles are dispersed in a sea of ​​the molding material as a matrix, a length of the cells of the second foam layer in a surface direction of the outer wall is shorter than a length of one of the adjacent cells constituting the open cells of the first foam layer; A method for manufacturing a container, characterized in that the waiting process is a process carried out without heat input, a process carried out with residual heat from the heating process remaining, or a process carried out with heat input to the extent that the outer surface temperature of the intermediate body drops.

19. A step of preparing a bottomed, cylindrical non-foamed preform, which is a molded product made of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), impregnated with an inert gas, and in a non-foamed state; a foaming step of converting the non-foamed preform into a foamed preform; a blow molding step of blow molding the foam preform to form a foam; Including, the foaming step includes a heating step of heating the non-foamed preform from its outer surface side to obtain an intermediate body, and a waiting step of conducting heat unevenly distributed on the outer surface side of the intermediate body after the heating step to its inner surface side to reduce the temperature difference between the outer surface and the inner surface of the intermediate body, the blow molding step is a step of forming a container having the foam as an outer wall, the foam has a first non-foamed layer and a foamed layer, the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer, the foam layer includes a first foam layer having a plurality of cells randomly arranged in three-dimensional directions and a cell wall skeleton separating adjacent cells, the first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, the reticulated cell structure including open cells in which adjacent cells communicate with each other through openings provided in the cell wall skeleton, and closed cells in which adjacent cells do not communicate with each other, and the open cells are broken at the openings; the open cells and the closed cells are present in the same cross section in the surface direction of the outer wall, the total length of the cells constituting the open cells in the same cross section is greater than the length of the closed cells, A method for manufacturing a container, characterized in that the waiting process is a process carried out without heat input, a process carried out with residual heat from the heating process remaining, or a process carried out with heat input to the extent that the outer surface temperature of the intermediate body drops.

20. A step of preparing a bottomed, cylindrical non-foamed preform, which is a molded product made of a molding material containing a thermoplastic resin (excluding cases where the thermoplastic resin is a polyolefin resin), impregnated with an inert gas, and in a non-foamed state; a foaming step of converting the non-foamed preform into a foamed preform; a blow molding step of blow molding the foam preform to form a foam; Including, The foaming step includes a heating step of heating the non-foamed preform from the outer surface side to obtain an intermediate body, and a waiting step of conducting heat unevenly distributed on the outer surface side of the intermediate body after the heating step to the inner surface side to reduce the temperature difference between the outer surface and the inner surface of the intermediate body, and a step of forming a foamed preform having a first non-foamed layer and a pre-foamed layer, the pre-foamed layer having a plurality of spherical foam cells, The particle size distribution of the spherical foam cells based on the number of cells has a broad distribution width of 52 μm or more and a mode diameter of 49 to 62 μm, The distribution width is the width of a frequency distribution graph of a particle size distribution obtained under the following condition 1: the blow molding step is a step of forming a container having the foam as an outer wall, the foamed body has a first non-foamed layer obtained by blow molding the first non-foamed layer of the foamed preform, and a foamed layer obtained by blow molding the pre-foamed layer of the foamed preform, the first non-foamed layer is disposed on the inner surface side of the container, and the foamed layer is disposed on the outer surface side of the container relative to the first non-foamed layer, the foam layer includes a first foam layer having a plurality of cells randomly arranged in three-dimensional directions and a cell wall skeleton separating adjacent cells, the first foamed layer has a reticulated cell structure in which the cell wall skeleton has a reticulated cross section, the reticulated cell structure includes open cells in which adjacent cells communicate with each other through openings formed in the cell wall skeleton, and the open cells are broken at the openings; A method for manufacturing a container, characterized in that the waiting process is a process carried out without heat input, a process carried out with residual heat from the heating process remaining, or a process carried out with heat input to the extent that the outer surface temperature of the intermediate body drops. Condition 1: The particle size distribution is determined by observing the cross section of the foamed preform at a magnification of 200 times using a reflected light microscope and measuring the number and diameter of each of the spherical foam cells present in the observed image.

21. The method for manufacturing a container according to any one of claims 18 to 20, characterized in that the foaming step is a step in which one cycle consisting of the heating step and the waiting step is performed two or more times.

22. the foaming step is a step of forming a foamed preform having a first non-foamed layer and a pre-foamed layer as the foamed preform, the pre-foamed layer having a plurality of spherical foam cells; 20. The method for manufacturing a container according to claim 18, wherein the particle size distribution of the spherical foamed cells based on the number of cells has a distribution width of 52 μm or more and a mode diameter of 49 to 62 μm.

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