ARTIGO MOLDADO POR PROCESSO IN-MOLD DE CONTAS EXPANDIDAS DE RESINA À BASE DE POLIPROPILENO

Description

1 / 69 Item molded using an in-mold process from expanded polypropylene resin beads. Divided from BR112023026887-7, deposited on 06 / 17 / 2022 TECHNICAL FIELD

[0001] The present invention relates to a molded article of expanded polypropylene-based resin beads in which tubular expanded beads, each with through holes, are joined together by fusion, and to a method for producing it. BACKGROUND OF THE TECHNIQUE

[0002] A molded article of expanded polypropylene resin beads is lightweight and excellent in damping, stiffness, and similar properties, and is therefore used for various applications. The molded article of expanded polypropylene resin beads is produced, for example, by an in-mold molding method, in which the expanded polypropylene resin beads are filled into a mold and heated with steam to secondarily expand the expanded beads, and at the same time, the surfaces of the expanded beads are fused and bonded together by fusion to mold the expanded beads into a desired shape. Since the molded article of expanded beads immediately after molding tends to swell due to secondary expansion, in order to obtain a molded article of expanded beads having a desired shape, the molded article of expanded beads is cooled in a mold with water, air, or similar and then demolded.

[0003] When the expanded bead molded article is stored at normal temperature after in-mold molding, vapor flowing into the cells of the expanded bead molded article during in-mold molding condenses within the cells, the interior of the cells has negative pressure, and a volume contraction occurs in Petition 870260043645, dated 08 / 05 / 2026, page 12 / 189 2 / 69 Expanded bead molded article and the molded article can be greatly deformed. Therefore, after releasing the expanded bead molded article from the mold, an aging step is usually required, allowing the expanded bead molded article to remain for a predetermined period of time under a high-temperature atmosphere set to a temperature of, for example, about 60°C to 80°C to recover its shape.

[0004] In in-mold molding of expanded polypropylene-based resin beads, since the aging step requires capital investment as well as time and effort, omitting the aging step leads to a significant improvement in the productivity of the molded expanded bead article. For example, Patent Literature 1 discloses a technique for melting expanded beads including a foam layer and a melt-bondable layer while maintaining voids between the beads, and Patent Literature 1 describes that the aging step can be omitted. Furthermore, Patent Literature 2 discloses an in-mold molding technique for expanded beads using polypropylene-based resin prepared to have a specific melting point, melt flow index, average molecular weight Z, and similar values ​​within specific ranges, and according to Patent Literature 2, the aging time can be reduced. Prior Art Literature PATENT LITERATURE

[0005] Patent Literature 1: JP-A-2003-39565 Patent Literature 2: JP-A-2000-129028 SUMMARY OF THE INVENTION TECHNICAL PROBLEMS

[0006] However, in the technique described in Patent Literature 1, Petition 870260043645, dated 08 / 05 / 2026, page 13 / 189 3 / 69 Although the aging step can be omitted, since a large number of voids are formed between the expanded beads of the molded article, the appearance of the expanded bead molded article is significantly imperfect, and the rigidity, depending on the applications, is insufficient. In the technique described in Patent Literature 2, although the aging step can be shortened, the aging step is still necessary, and in the case of omitting the aging step, the expanded bead molded article shrinks significantly and deforms, and it is difficult to obtain the expanded bead molded article with the desired shape.

[0007] The present invention was made in view of such background, and an objective of the present invention is to provide a method for producing a molded article of expanded polypropylene-based resin beads capable of achieving the desired shape, as well as excellent appearance and rigidity, even when the aging step is omitted. WAYS TO SOLVE THE PROBLEM

[0008] One aspect of the present invention is a method for producing a molded article of expanded polypropylene resin beads, filling a mold with tubular expanded polypropylene resin beads, each having a through hole, and providing a heating means to fuse the expanded beads together, wherein the expanded beads have a foam layer made of a polypropylene resin, a closed-cell content of the expanded beads is 90% or more, an average hole diameter d of the through holes of the expanded beads is less than 1 mm, and a ratio [d / D] of the average hole diameter d to an average outer diameter D of the beads. Petition 870260043645, dated 08 / 05 / 2026, page 14 / 189 4 / 69 expanded is 0.4 or less, and an open cell content of the molded article of expanded beads is 2.5% or more and 12% or less.

[0009] Another aspect of the present invention is a molded article of expanded polypropylene-based resin beads, the molded article being formed by tubular expanded polypropylene-based resin beads bonded by fusion, each having a through hole between them, wherein a closed cell content of the molded expanded bead article is 90% or more, and an open cell content of the molded expanded bead article is 2.5% or more and 12% or less. EFFECTS OF THE INVENTION

[0010] According to the present invention, the molded article of expanded polypropylene-based resin beads having the desired shape and being excellent in appearance and rigidity can be obtained even when the aging step is omitted. Thus, according to the production method, the production efficiency of the molded article of expanded beads with excellent appearance and rigidity can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic view of the appearance of an expanded bill. Figure 2 is a schematic view of a cross-section of the expanded bead in a direction parallel to the direction of penetration of a passage hole in the expanded bead made of a layer of foam. Figure 3 is a schematic view of a cross-section of the expanded bead in the direction parallel to the direction of penetration of the hole through which the expanded bead passes, having a Petition 870260043645, dated 08 / 05 / 2026, page 15 / 189 5 / 69 foam layer (2) and a fusion bondable layer (3). Figure 4 is an explanatory diagram showing a method for calculating the area of ​​a high-temperature peak. EMBODIMENTS OF THE INVENTION

[0012] In the present description, A to B is described as a numerical range meaning A or more and B or less and is used as including the values ​​of A and B that are endpoints of the numerical range. Furthermore, in the case where a numerical value or a physical property value is expressed as a lower limit, this means that the numerical value or the physical property value is equal to or greater than the numerical value or the physical property value, while in a case where a numerical value or a physical property value is expressed as an upper limit, this means that the numerical value or the physical property value is equal to or less than the numerical value or the physical property value. Additionally, % by weight and % by mass and parts by weight and parts by mass are substantially synonymous, respectively.Furthermore, in the present description, expanded polypropylene-based resin beads are appropriately referred to as expanded beads, and the molded article of expanded beads is appropriately referred to as a molded article. Note that expanded beads having the foam layer made of polypropylene-based resin are generally called expanded polypropylene-based resin beads.

[0013] The molded article of expanded beads is produced by performing a molding step in which a large number of expanded beads are added to a mold and a heating medium, such as steam, is provided to fuse the expanded beads together. In other words, the molded article can be obtained by in-mold molding of the expanded beads.

[0014] Each of the expanded granules has a tubular shape. Petition 870260043645, dated 08 / 05 / 2026, page 16 / 189 6 / 69 with a through hole, the average hole diameter d of the through holes is less than 1 mm and a ratio d / D of the average hole diameter d to an average outer diameter D of the expanded beads is 0.4 or less. The expanded beads have a foam layer made of polypropylene-based resin and have a closed-cell content of 90% or more. By molding such expanded beads in a mold to produce a molded article having an open-cell content of 2.5% or more and 12% or less, the molded expanded bead article having a desired shape and being excellent in appearance and rigidity can be obtained even when the aging step is omitted. In a case where the aging step is omitted, for example, the shape of the molded article can be stabilized by letting the molded article rest for 12 hours or more after demolding in an environment of 23°C. However, it is also possible to perform the aging step.Note that, in the production method described above, pre-pressurization, in which internal pressure is applied to the expanded granules before they are filled into the mold, may be performed, or pre-pressurization may not be performed. It is possible to produce the molded article from expanded spheres having a desired shape and being excellent in appearance and rigidity, while omitting the aging step without performing pre-pressurization.

[0015] Figures 1 to 3 show the expanded bead, but the present invention is not limited to these drawings. As shown in Figure 1 and Figure 2, an expanded bead 1 has a tubular shape and has a through hole 11. The expanded bead 1 has a foam layer 2 composed of polypropylene-based resin. In addition, as shown in Figure 3, the expanded bead 1 preferably has a fusion-bondable layer 3 covering the foam layer 2. Petition 870260043645, dated 08 / 05 / 2026, p. 17 / 189 7 / 69

[0016] The foam layer is made of polypropylene-based resin. In the present description, polypropylene-based resin refers to a homopolymer of a propylene monomer and a propylene-based copolymer containing 50% or more by mass of a propylene-derived structural unit. The polypropylene-based resin is preferably a propylene-based copolymer obtained by copolymerizing propylene with another monomer. Preferred examples of propylene-based copolymers include copolymers of propylene and an α-olefin with 4 to 10 carbon atoms, such as an ethylene-propylene copolymer, a butene-propylene copolymer, a hexene-propylene copolymer, and an ethylene-propylene-butene copolymer. These copolymers are, for example, random copolymers, block copolymers, and the like, and are preferably random copolymers. Furthermore, polypropylene-based resin can contain a plurality of polypropylene-based resin types.

[0017] The polypropylene-based resin that constitutes the foam layer may contain a polymer other than the polypropylene-based resin, provided that the purpose and effect of this disclosure are not impaired. Examples of the other polymer include elastomers or thermoplastic resins other than polypropylene-based resin, such as polyethylene-based resin and polystyrene-based resin. The content of the other polymer in the polypropylene-based resin that constitutes the foam layer is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and 0, that is, it is particularly preferred that the foam layer contains substantially only polypropylene-based resin as the polymer.

[0018] The polypropylene-based resin that makes up the layer of Petition 870260043645, dated 08 / 05 / 2026, p. 18 / 189 8 / 69 foam is a random copolymer of ethylene-propylene, and the content of an ethylene component in the copolymer is preferably 0.5% by mass or more and 10% by mass or less. Note that the total ethylene component and propylene component in the random ethylene-propylene copolymer is 100% by mass. In this case, it is possible to mold the molded article with excellent rigidity at a lower molding heating temperature (i.e., with low molding pressure). From the point of view of further improving this effect, the content of the ethylene component in the copolymer is more preferably greater than 2.0% by mass and 5.0% by mass or less, even more preferably 2.5% by mass or more and 4.0% by mass or less, and with particular preference 2.8% by mass or more and 3.5% by mass or less. Note that the content of a monomer component in the copolymer can be obtained by measuring the IR spectrum.The ethylene component and the propylene component of the ethylene-propylene copolymer mean one ethylene-derived structural unit and one propylene-derived structural unit in the ethylene-propylene copolymer, respectively. Furthermore, the content of each monomer component in the copolymer means the content of one structural unit derived from each monomer in the copolymer.

[0019] The melting point Tmc of the polypropylene-based resin that constitutes the foam layer is preferably 155°C or less. In this case, the molded article with excellent appearance and rigidity can be molded at a lower molding temperature (i.e., with molding pressure). From the point of view of improving this effect, the melting point Tmc of the polypropylene-based resin that constitutes the foam layer is preferably 150°C or lower, and more preferably 145°C or lower. On the other hand, from the point of view of further improving the heat resistance, mechanical strength and the like of the molded article, the melting point Tmc of the polypropylene-based resin Petition 870260043645, dated 08 / 05 / 2026, p. 19 / 189 9 / 69 The polypropylene that constitutes the foam layer is preferably 135°C or higher, more preferably 138°C or higher, and even more preferably 140°C or higher.

[0020] The melting point of polypropylene-based resin is obtained based on JIS K7121:1987. Specifically, (2) The case of measuring the melting temperature after a definitive heat treatment is adopted as a state fit, a DSC curve is obtained by increasing the temperature of a specimen subjected to the state fit from 30°C to 200°C at a heating rate of 10°C / min, and the apex temperature of the melting peak is defined as the melting point. Note that when a plurality of melting peaks appear in the DSC curve, the apex temperature of the melting peak with the largest area is considered as the melting point.

[0021] From the point of view of further improving expansion and moldability, a molten mass flow rate (i.e., MFR) of the polypropylene-based resin constituting the foam layer is preferably 5 g / 10 min or more, more preferably 6 g / 10 min or more, and even more preferably 7 g / 10 min or more. On the other hand, from the point of view of further increasing the stiffness of the molded article, the MFR is preferably 12 g / 10 min or less, and more preferably 10 g / 10 min or less. Note that the MFR of the polypropylene-based resin is a value measured under test temperature conditions of 230°C and a load of 2.16 kg based on JIS K7210-1:2014.

[0022] The polypropylene-based resin that constitutes the foam layer preferably has a flexural modulus of 800 MPa or more and 1600 MPa or less. From the point of view of increasing the stiffness of the molded article and from the point of view of more reliably preventing dimensional change in the event of omitting the aging step, the flexural modulus of the polypropylene-based resin Petition 870260043645, dated 08 / 05 / 2026, page 20 / 189 The flexural modulus of the 10 / 69 polypropylene resin that constitutes the foam layer is preferably 800 MPa or more, more preferably 850 MPa or more, and even more preferably 900 MPa or more. On the other hand, from the point of view that a molded article excellent in appearance and rigidity can be molded at a lower molding temperature (i.e., with low molding pressure) and from the point of view of obtaining a molded article of expanded beads excellent in energy absorption capacity, the flexural modulus of the polypropylene-based resin that constitutes the foam layer is preferably less than 1,200 MPa, more preferably 1,100 MPa or less, and even more preferably 1,000 MPa or less. Note that the flexural modulus of the polypropylene-based resin can be obtained based on JIS K7171: 2008.

[0023] In the past, in particular, when expanded beads made of polypropylene-based resin with a flexural modulus of less than 1200 MPa are molded in a mold, the molded article tends to shrink and deform significantly, probably because the resistance to shrinkage and deformation after demolding is small if the aging step is omitted. According to the method for producing a molded article, for example, even when using expanded beads made of polypropylene-based resin with a flexural modulus of less than 1200 MPa, the aging step can be omitted.

[0024] The closed-cell content of the expanded beads is 90% or more. From the point of view of ensuring good in-mold moldability of the expanded beads, and from the point of view of achieving a good appearance and rigidity of the expanded beads, the closed-cell content of the foam layer is preferably 92% or more, and more preferably 95% or more.

[0025] The closed-cell content of expanded accounts can be Petition 870260043645, dated 08 / 05 / 2026, page 21 / 189 11 / 69 measured using an air comparison pycnometer based on Procedure C of ASTM-D2856-70. Specifically, the measurement is performed as follows. Using expanded beads having a bulk volume of approximately 20 cm3 after state adjustment as a measuring sample, an apparent volume Va was accurately measured by an ethanol immersion method as described below. After the measuring sample whose apparent volume Va was measured is sufficiently dry, a true volume value Vx of the measuring sample measured by the AccuPyc II 1340 manufactured by Shimadzu Corporation is measured according to Procedure C described in ASTM-D2856-70. Then, based on these volume values ​​Va and Vx, the closed-cell content is calculated by the following formula (I), and an average value of five samples (N = 5) is taken as the closed-cell content of the expanded beads.

[0026] Closed cell content (%) = (Vx - W / ρ) χ 100 / (Va - W / ρ) ... (I) given that Vx: the actual volume of the expanded beads measured by the method above, i.e., the sum of the volume of the resin that constitutes the expanded beads and the total volume of the closed cell portion in the expanded beads (unit: cm3). Va: the apparent volume (unit: cm3) of expanded beads measured from the rise in water level when the expanded beads are immersed in a measuring cylinder containing ethanol. W: weight of the measurement sample for expanded beads (unit: g), and ρ: density of the resin that constitutes the expanded beads (unit: g / cm3).

[0027] The molded article has an open-cell structure. The open-cell structure is a small portion of space that Petition 870260043645, dated 08 / 05 / 2026, page 22 / 189 12 / 69 communicates with the exterior of the molded article. The open cell structure is formed by the complicated connection of formed voids allowing the through holes of a plurality of expanded beads to communicate with each other, formed voids allowing the through holes of the expanded beads to communicate with the voids formed between the expanded beads, formed voids allowing the voids between the expanded beads to communicate with each other, open cell portions of the expanded beads that constitute the molded article, and the like.

[0028] In the above production method, a molded article with an open-cell content of 2.5% or more and 12% or less is produced. Based on this, even when the aging step is omitted, significant shrinkage, deformation, and the like are prevented, and a molded article having the desired shape and being excellent in appearance and rigidity can be produced. This is considered because when the molded article has an open-cell structure in a predetermined proportion, air flows rapidly into the cells of the molded article after demolding, and the internal pressure of the entire molded article increases, so that the dimensions of the molded article stabilize easily in an initial phase. In the case where the open-cell content of the molded article is less than 2.5%, when the aging step is omitted, the molded article may be significantly shrunk and deformed, and a molded article with the desired shape may not be obtained.From the point of view that significant shrinkage, deformation, and similar issues of the molded article can still be avoided even when the aging step is omitted, the open-cell content of the molded article is preferably 3% or more, more preferably 4% or more, and even more preferably 4.5% or more. On the other hand, in a case where the open-cell content of the molded article exceeds 12%, the appearance of... Petition 870260043645, dated 08 / 05 / 2026, p. 23 / 189 13 / 69 The molded article may deteriorate and its rigidity may deteriorate. From the point of view that the appearance and rigidity of the molded article may be further improved, the open cell content of the molded article is preferably 10% or less, more preferably 8% or less, even more preferably 7.5% or less, and with particular preference 6% or less.

[0029] The open cell content of the molded article is measured according to ASTM 2856-70 Procedure B. In other words, the open cell content is a corrected open cell content measured by a method of correcting for broken closed cells during the cutting of the considered measurement sample. As a measuring device, an automatic dry densitometer is used (specifically, AccuPyc II 1340 manufactured by Shimadzu Corporation). Specifically, the open cell content is measured as follows. To begin, the state of the molded article is adjusted by allowing the molded article to remain at 23°C for 12 hours. Then, a first test specimen with a cubic shape of 2.5 cm length x 2.5 cm width x 2.5 cm height is cut from a central portion of the molded article, and its geometric volume Va [unit: cm3] is measured. Specifically, Va is a value obtained by vertical dimension [cm] χ horizontal dimension [cm] x height dimension [cm].A real volume V1 [unit: cm3] of the first specimen is measured with the dry automatic densitometer. Then, the first specimen is divided into 8 equal parts to obtain a second cubic specimen 1.25 cm long x 1.25 cm wide x 1.25 cm high. Then, the real volume V2 [unit: cm3] of the second specimen is measured with the dry automatic densitometer. Note that the true volume V2 of the second specimen is the total value of the real volumes of the eight pieces cut from the first specimen. An open cell content Co [unit:%] is calculated by the following formula (II). Petition 870260043645, dated 08 / 05 / 2026, page 24 / 189 14 / 69

[0030] Note that, as the open cell content of the molded article, the first five test pieces are cut from the molded article, the open cell content is calculated by the method above, and an arithmetic mean value thereof is used as the result. The open cell content Co measured in this way is also referred to as the corrected continuous cell content. Co = (Va - 2V1 + V2) x 100 / Va ... (II)

[0031] Note that the open cell content Co in the present description is a physical property value measured in accordance with ASTM 2856-70 Procedure B as described above and is a physical property value that cannot be calculated based on the closed cell content of the molded article measured in accordance with ASTM 2856-70 Procedure C to be described later. Specifically, the relationship between the open cell content Co of the molded article measured in accordance with ASTM 2856-70 Procedure B and the closed cell content Bp of the molded article measured in accordance with ASTM 2856-70 Procedure C is represented by the following formula (III).The open cell content (Co) measured according to ASTM 2856-70 Procedure B is corrected by considering the closed cells broken when the specimen is cut, whereas in the method described in ASTM 2856-70 Procedure C, the closed cells broken when the specimen is cut are not considered, and therefore both are conceptually different. Furthermore, the proportion of closed cells broken when the specimen is cut is greatly affected by the shape (i.e., presence or absence of through holes, hole diameter of the through holes, and the like) of the expanded beads that constitute the molded article and by the closed cell content of the expanded beads. Additionally, it is also affected by the molding conditions (i.e., molding pressure, internal pressure of the expanded beads, filling method, and the like). Petition 870260043645, dated 08 / 05 / 2026, page 25 / 189 15 / 69 molded article of expanded beads. Thus, it is also difficult to estimate the value of the open-cell Co content based on the value of the closed-cell content of the molded article measured according to ASTM 2856-70 Procedure C.

[0032] Furthermore, the open cell content Co of the present description is conceptually different from the porosity of the molded article. The porosity of the molded article is measured and calculated, for example, as follows. Specifically, to begin with, a rectangular parallelepiped-shaped specimen (20 mm long x 100 mm wide x 20 mm high) is cut from the central portion of the molded article. Then, the specimen is immersed in a measuring cylinder containing ethanol, and the actual volume Vc [L] of the specimen is obtained from the rise in the liquid level of the ethanol. In addition, the apparent volume Vd [L] is obtained from the external dimension of the specimen. The porosity of the molded article can be obtained from the true volume Vc obtained and the apparent volume Vd by the following formula (IV). Thus, also in the measurement of the porosity of the molded article, broken closed cells are not considered when the specimen is cut.Furthermore, the method differs from a measurement method for open-cell Co content in that a liquid such as ethanol is used as the measuring medium. The porosity of the molded article is always greater than the open-cell Co content of the molded article. Co # 100-Bp ... (III) Porosity (%) = [(Vd - Vc) / Vd] χ 100 ... (IV)

[0033] A molded article having an open cell content of 2.5% or more and 12% or less is produced by in-mold molding of expanded beads that satisfy the following items (1) to (3).

[0034] (1) Expanded beads have through holes. In the case where the expanded beads do not have through holes, it is difficult Petition 870260043645, dated 08 / 05 / 2026, page 26 / 189 16 / 69 set the value for the open cell content of the molded article at 2.5% or more.

[0035] (2) The average hole diameter d of the through holes of the expanded beads is adjusted to less than 1 mm. By decreasing the average hole diameter, the open cell content tends to decrease, and by increasing the average hole diameter, the open cell content tends to increase. In the case where the average diameter of the through holes is 1 mm or more, it tends to be difficult to define the value of the open cell content of the molded article to 12% or less.

[0036] (3) The ratio [d / D] between the average hole diameter d of the through holes and the average outside diameter D of the expanded beads is defined as 0.4 or less. By decreasing the ratio [d / D], the open cell content tends to decrease, and by increasing the ratio [d / D], the open cell content tends to increase. In the case where the ratio [d / D] exceeds 0.4, it tends to be difficult to define the value of the open cell content of the molded article to 12% or less.

[0037] In addition to in-mold molding using expanded beads that satisfy items (1) to (3) above, for example, by controlling the following conditions (4) to (6) in in-mold molding, the open cell content of the molded article can be easily adjusted to a range of 2.5% or more and 12% or less.

[0038] (4) When internal pressure is applied to the expanded beads before loading the beads into the mold, secondary expansion easily occurs during molding, so the open cell content tends to decrease. Furthermore, when the internal pressure of the expanded beads increases, the expanded beads are more likely to swell during molding and thus the open cell content tends to decrease. From the point of view of preventing the open cell content from becoming too low and of more stably producing a molded article having an open cell content of 2.5% or Petition 870260043645, dated 08 / 05 / 2026, page 27 / 189 17 / 69 more, and from the point of view of the production efficiency of the molded article, the internal pressure of the expanded beads loaded into the mold is preferably 0.05 MPa (G) (G: gauge pressure) or less, more preferably 0.03 MPa (G) or less, even more preferably 0.01 MPa (G) or less, and 0 MPa (G), that is, it is particularly preferable to mold the expanded beads without applying internal pressure to the expanded beads. Note that, from the point of view of molding a good molded article of expanded beads, the lower limit of the internal pressure is 0 MPa (G).

[0039] (5) In the case of filling the expanded beads in the mold by a fissure filling method, when the fissure width (%) increases, as gaps between the expanded beads are easily filled, the open cell content tends to decrease, and when the fissure width (%) decreases, as gaps between the expanded beads are easily formed, the open cell content tends to increase. The fissure width is generally preferably in the range of 5% to 35%, more preferably in the range of 10% to 30%, and even more preferably in the range of 15% to 25%. Incidentally, note that the fissure filling method is a method for providing an open portion in the mold that does not completely close that die, to efficiently load the expanded beads in a quantity that exceeds the mold volume when filling it.This open portion is called a fissure, and the ratio (%) between the volume of the open portion and the volume of the mold is expressed as the fissure width (%). Incidentally, note that the fissure is finally closed when steam is introduced after the expanded beads are loaded into the mold, and as a result, the loaded expanded beads are mechanically compressed.

[0040] (6) When the molding temperature (specifically, the molding pressure) increases, the open cell content tends to Petition 870260043645, dated 08 / 05 / 2026, page 28 / 189 18 / 69 decrease, and when the molding temperature (specifically, the molding pressure) decreases, the open cell content tends to increase. However, from the point of view of the production efficiency of the molded article, it is preferable to perform the molding at low molding pressure. From this point of view, the molding pressure is, for example, preferably in the range of 0.20 MPa (G) (G: gauge pressure) to 0.30 MPa (G), more preferably in the range of 0.20 MPa (G) to 0.26 MPa (G), and even more preferably in the range of 0.22 MPa (G) to 0.24 MPa (G).

[0041] As described above, by controlling the molding conditions of the expanded beads as in (4) to (6), the open cell content of the molded article can be easily adjusted to a range of 2.5% or more and 12% or less. The conditions for adjusting the open cell content of the molded article are not necessarily limited to (4) to (6). In other words, by molding the expanded beads so that the open cell content of the molded article is 2.5% or more and 12% or less, a molded article with the desired shape and having excellent appearance and rigidity can be produced, being formed without aging.

[0042] Expanded beads are preferably expanded beads with a multi-layered structure, with a foam layer and a fusion-bondable layer covering the foam layer. In the case where the expanded beads have a fusion-bondable layer, the fusion-bondable layer is made, for example, of a polyolefin-based resin. Examples of polyolefin-based resins include polyethylene-based resin, polypropylene-based resin, and polybutene-based resin. From the point of view of adhesion to the foam layer, the polyolefin-based resin is preferably a polyethylene-based resin or a polypropylene-based resin, and more preferably a resin based on Petition 870260043645, dated 08 / 05 / 2026, p. 29 / 189 19 / 69 polypropylene. Examples of polypropylene-based resin include an ethylene-propylene copolymer, an ethylene-butene copolymer, an ethylene-propylene-butene copolymer, a propylene homopolymer and the like, and among these, the ethylene-propylene copolymer or the ethylene-propylene-butene copolymer is preferred.

[0043] The melting point Tms of the polyolefin-based resin that constitutes the melt-bondable layer is preferably lower than the melting point Tmc of the polypropylene-based resin that constitutes the foam layer. In other words, it is preferable that Tms < Tmc. In this case, the melting capacity of the expanded beads is improved and molding at a lower temperature becomes possible. Furthermore, in this case, significant shrinkage and deformation in the event of omission of the aging step can be more easily prevented. The reason for this is not clear, but it is considered that molding at a low molding heating temperature makes it possible to reduce the heat received by the expanded beads from the heating medium, such as steam in in-mold molding, and dimensional change due to thermal contraction of the molded article is more easily prevented.From the point of view above, Tmc - Tms > 5 is preferable, Tmc - Tms > 6 is more preferable, and Tmc - Tms > 8 is even more preferable. From the point of view of further suppression of delamination between the foam layer and the fusion-bondable layer, adhesion between expanded beads and the like, Tmc - Tms < 35 is preferable, Tmc - Tms < 20 is more preferable, and Tmc - Tms < 15 is even more preferable.

[0044] From the point of view of further improving the fusion capacity of expanded beads during molding, the Tms melting point of the polyolefin-based resin that constitutes the fusion-bondable layer is preferably 120°C or higher and 145°C or lower, and more preferably 125°C or higher and 140°C or lower. The melting point of Petition 870260043645, dated 08 / 05 / 2026, page 30 / 189 20 / 69 The polyolefin-based resin that constitutes the fusion-bondable layer is obtained based on JIS K7121:1987. Specifically, it is obtained under the same conditions and methods as the polypropylene-based resin that constitutes the foam layer described above.

[0045] From the point of view of reliably preventing delamination between the foam layer and the melt-bondable layer, the melt flow rate (MFR) of the polyolefin-based resin that constitutes the melt-bondable layer is preferably approximately the same as the MFR of the polypropylene-based resin that constitutes the foam layer, and specifically, is preferably 2 to 15 g / 10 min, more preferably 3 to 12 g / 10 min, and even more preferably 4 to 10 g / 10 min. Please note that, in the case where the polyolefin-based resin is a polypropylene-based resin, the MFR is a value measured under test temperature conditions of 230°C and a load of 2.16 kg according to JIS K7210-1:2014, and in the case where the polyolefin-based resin is a polyethylene-based resin, the MFR is a value measured under test temperature conditions of 190°C and a load of 2.16 kg according to JIS K7210-1:2014.

[0046] In the case where expanded beads are beads with a multi-layered structure including the foam layer and the fusion-bondable layer covering the foam layer, the foam layer is composed of polypropylene-based resin in an expanded state, and the fusion-bondable layer is composed of polyolefin-based resin in either the expanded or unexpanded state. The fusion-bondable layer is preferably in a substantially unexpanded state. The term substantially unexpanded state includes a state in which the fusion-bondable layer is not expanded and cells are not present, and a state in which the cells disappear after expansion, meaning that there is almost no cellular structure. The thickness of the fusion-bondable layer is, by Petition 870260043645, dated 08 / 05 / 2026, p. 31 / 189 21 / 69 example, from 0.5 to 100 mm. In addition, an intermediate layer may also be provided between the foam layer and the fusion-bondable layer.

[0047] The mass ratio (mass % ratio) of the resin constituting the foam layer and the resin constituting the fusion-bondable layer is preferably 99.5:0.5 to 80:20, more preferably 99:1 to 85:15, and even more preferably 97:3 to 90:10 from the point of view of improving moldability while maintaining the rigidity of the molded article. The mass ratio is represented by the resin constituting the foam layer: the resin constituting the fusion-bondable layer.

[0048] The expanded beads preferably have a crystalline structure in which an endothermic peak (i.e., a peak intrinsic to the resin) appears due to the inherent melting of the polypropylene-based resin and one or more melting peaks (i.e., high-temperature peaks) on a high-temperature side of the same in a DSC curve obtained when heated from 23°C to 200°C at a heating rate of 10°C / min. The DSC curve is obtained by differential scanning calorimetry (DSC) according to JIS K7121:1987, using 1 to 3 mg of expanded beads as a test sample.

[0049] The intrinsic resin peak is the endothermic peak due to the intrinsic melting of the polypropylene-based resin that constitutes the expanded beads and is considered to be due to endothermic melting of the crystals inherent to the polypropylene-based resin. On the other hand, the endothermic peak on the high-temperature side of the intrinsic resin peak (i.e., the high-temperature peak) is an endothermic peak that appears on the higher-temperature side than the intrinsic resin peak in the DSC curve. When this high-temperature peak appears, it is assumed that secondary crystals are present in the resin. Note that, as described above, in the DSC curve obtained when heating Petition 870260043645, dated 08 / 05 / 2026, p. 32 / 189 22 / 69 from 23°C to 200°C (i.e., a first heating) is carried out at a heating rate of 10°C / min, and then cooling from 200°C to 23°C is carried out at a cooling rate of 10°C / min, and heating from 23°C to 200°C (i.e., a second heating) is again carried out at a heating rate of 10°C / min, since only the endothermic peak due to the inherent melting of the polypropylene-based resin that constitutes the expanded beads is observed, the intrinsic resin peak and the high-temperature peak can be distinguished. The peak temperature of the intrinsic resin peak may be slightly different between the first heating and the second heating, but the difference is generally within 5°C.

[0050] The heat of fusion at the high-temperature peak of the expanded beads is preferably 5 to 40 J / g, more preferably 7 to 30 J / g, and even more preferably 10 to 20 J / g from the point of view of further improving the moldability of the expanded beads and from the point of view of obtaining a molded article with better rigidity.

[0051] Furthermore, the ratio of the heat of fusion of the high-temperature peak to the heat of fusion of all the melting peaks of the DSC curve (the heat of fusion of the high-temperature peak / the heat of fusion of all the melting peaks) is preferably 0.05 to 0.3, more preferably 0.1 to 0.25 and even more preferably 0.15 to 0.2.

[0052] By defining the ratio between the heat of fusion of the high-temperature peak and the heat of fusion of all fusion peaks within such a range, it is considered that the expanded beads have particularly excellent mechanical strength and excellent in-mold moldability due to the presence of secondary crystals represented as the high-temperature peak.

[0053] Here, the heat of fusion of all fusion peaks refers to the sum of the heat of fusion obtained from the areas of all fusion peaks in the DSC curve. Petition 870260043645, dated 08 / 05 / 2026, p. 33 / 189 23 / 69

[0054] The heat of fusion at each peak of the DSC curve of the expanded beads is a value obtained as follows. To begin, an expanded bead is collected from a group of expanded beads after state adjustment. Using the expanded beads as a test specimen, a DSC curve is obtained when the test specimen is heated from 23°C to 200°C at a heating rate of 10°C / min by a differential scanning calorimeter. Figure 4 shows an example of the DSC curve. As exemplified in Figure 4, the DSC curve has an intrinsic resin peak ΔH1 and a high-temperature peak ΔH2 having a vertex on the higher-temperature side than the vertex of the intrinsic resin peak ΔH1.

[0055] Next, a point α at a temperature of 80°C on the DSC curve and a point β at a final melting temperature T of the expanded beads are connected to obtain a straight line L1. Then, a straight line L2 parallel to a vertical axis of the graph is drawn from a point γ on the DSC curve corresponding to a valley portion between the intrinsic resin peak ΔH1 and the high-temperature peak ΔH2, and a point where the straight line L1 and the straight line L2 intersect is defined as δ. Note that the point γ can also be referred to as a maximum point existing between the intrinsic resin peak ΔH1 and the high-temperature peak ΔH2.

[0056] The intrinsic resin peak area ΔH1 is the area of ​​a portion enclosed by the intrinsic resin peak portion ΔH1 of the DSC curve, the α-δ line segment and the γ-δ line segment, and this is taken as the heat of fusion of the intrinsic resin peak.

[0057] The high-temperature peak area ΔH2 is the area of ​​a portion enclosed by the high-temperature peak portion ΔH2 of the DSC curve, the δ-β line segment and the γ-δ line segment, and this is considered to be the heat of fusion (i.e., the high-temperature peak heat) of the high-temperature peak (i.e., peak heat of Petition 870260043645, dated 08 / 05 / 2026, page 34 / 189 24 / 69 high temperature).

[0058] The area of ​​all melting peaks is the area of ​​a portion enclosed by the curve of the resin intrinsic peak portion ΔH1 of the DSC curve, the curve of the high-temperature peak portion ΔH2 and the line segment α-β (i.e., the straight line LI), and this is considered the heat of fusion of all melting peaks.

[0059] Expanded beads have through holes as described above. Expanded tubular beads that have through holes preferably have at least one tubular hole penetrating in an axial direction of the expanded columnar beads, such as a cylinder and a prism. It is more preferable that the expanded beads have a cylindrical shape and have the tubular hole penetrating in their axial direction.

[0060] In cases where expanded beads do not have through holes, the open cell content of the molded article tends to decrease to, for example, less than 2.5%. As a result, if the aging step is omitted, significant shrinkage and deformation of the molded article may not be prevented. If it is desired to increase the open cell content of the molded article using expanded beads without through holes, for example, the molding pressure is reduced to actively form voids between beads, but the appearance and rigidity of the molded article may be significantly deteriorated. On the other hand, even in cases where expanded beads have through holes, when the average hole diameter d is too large, the open cell content of the molded article tends to increase to, for example, more than 12%. As a result, the appearance and rigidity of the molded article may be deteriorated.In cases where it is desired to reduce the open cell content of the molded article using expanded beads having an excessively large average hole diameter d, for example. Petition 870260043645, dated 08 / 05 / 2026, page 35 / 189 25 / 69 considers increasing the molding pressure sufficiently, but the molded article may shrink thermally, impairing dimensional stability. From this point of view, the average hole diameter d of the expanded beads is less than 1 mm as described above. The average hole diameter d of the expanded beads is preferably 0.95 mm or less, more preferably 0.92 mm or less, and even more preferably 0.90 mm or less from the point of view of obtaining the molded article having the desired shape and obtaining a molded article with better appearance and rigidity even when the aging step is omitted. Note that, from the point of view that the value of the open cell content of the molded article can be more easily adjusted, the lower limit of the average hole diameter d of the expanded beads is preferably 0.2 mm or more, and more preferably 0.4 mm or more.

[0061] The average hole diameter d of the expanded beads can be adjusted not only by adjusting the hole diameter dr of the through holes in the resin particles to be described later, but also by adjusting the apparent density and the high-temperature peak heat of the expanded beads. Furthermore, the average hole diameter d can be more easily adjusted to a small value by forming the expanded beads into second-stage expanded beads produced by the two-stage expansion method.

[0062] The average hole diameter d of the through holes of the expanded beads is obtained as follows. 50 or more randomly selected expanded beads from the expanded bead group are cut perpendicular to the direction of penetration of the through holes in a position where the area of ​​the cut surface is maximized. The cut surface of each expanded bead is photographed, a cross-sectional area (specifically, an opening area) of the through-hole portions is obtained, the diameter of a Petition 870260043645, dated 08 / 05 / 2026, page 36 / 189 26 / 69 A perfect virtual circle having the same area as the cross-sectional area is calculated, and the arithmetic mean value thereof is taken as the average diameter of the hole d of the through holes of the expanded beads. Note that, even when the size of the through holes of each expanded bead is not uniform with respect to the diameter of the through hole in the direction of penetration, the diameter of the through hole of each expanded bead is determined by the diameter of the hole at a position where the area of ​​the cut surface of the expanded bead is maximized as described above.

[0063] The average outside diameter D of the expanded beads is preferably 2 mm or more, more preferably 2.5 mm or more, and even more preferably 3 mm or more from the point of view that the wall thickness of the expanded tubular beads increases and the secondary expansion capacity of the expanded beads and the rigidity of the molded article are improved. On the other hand, the thickness is preferably 5 mm or less, more preferably 4.5 mm or less, and even more preferably 4.3 mm or less from the point of view of improving the filling property in the mold during molding.

[0064] The d / D ratio of the average hole diameter d to the average outside diameter D of the expanded beads is 0.4 or less. In cases where the d / D ratio is too large, the open cell content of the molded article tends to increase to, for example, more than 12%. As a result, the appearance and rigidity of the molded item may be deteriorated. From the point of view of improving the appearance of the molded article, from the point of view of further improving rigidity, and from the point of view of further improving secondary expansion capacity, the d / D ratio is preferably 0.35 or less, more preferably 0.3 or less, and even more preferably 0.25 or less. Note that the d / D ratio is preferably 0.1 or more from the point of view of Petition 870260043645, dated 08 / 05 / 2026, p. 37 / 189 27 / 69 that the value of the open cell content of the molded article can be more easily adjusted.

[0065] The average outside diameter of the hole D of the expanded beads is obtained as follows. 50 or more randomly selected expanded beads from the expanded bead group are cut perpendicular to the direction of penetration of the through holes in a position where the area of ​​the cut surface is maximized. The cut surface of each expanded bead is photographed, the cross-sectional area (specifically the cross-sectional area also includes a portion of the opening of the through holes) of the expanded beads is obtained, the diameter of a perfect virtual circle having the same area as the cross-sectional area is calculated, and the arithmetic mean of these values ​​is taken as the average outside diameter D of the expanded beads.Note that even when the outer diameter of each expanded bead is not uniform in the direction of penetration, the outer diameter of each expanded bead is determined by the outer diameter at a position where the cut surface area of ​​the expanded bead in the direction perpendicular to the direction of penetration is maximized as described above.

[0066] The average wall thickness t of expanded tubular beads is preferably 1.2 mm or more and 2 mm or less. When the average wall thickness t is within this range, the wall thickness of the expanded beads is sufficiently thick so that the secondary expansion capacity during in-mold molding is further improved. In addition, the expanded beads are less likely to be crushed against an external force and the rigidity of the molded article is further improved. From this point of view, an average wall thickness t of the expanded beads is more preferably 1.3 mm or more, and even more preferably 1.5 mm or more. Petition 870260043645, dated 08 / 05 / 2026, p. 38 / 189 28 / 69

[0067] The average wall thickness t of the expanded beads is a distance from a surface (i.e., an external surface) of the expanded beads to an external periphery (i.e., internal surfaces of the expanded beads) of the through hole, and is a value obtained by the following formula (A). t = (Dd) / 2... (A) d: average hole diameter (mm) of through holes D: average outer diameter (mm) of the expanded beads

[0068] Furthermore, the t / D ratio between the average wall thickness te and the average outer diameter D of the expanded beads is preferably 0.35 or more and 0.5 or less. When t / D is within the above range, the filling property of the expanded beads is good and the secondary expansion capacity is further improved in the in-mold molding of the expanded beads. Consequently, the molded article with excellent appearance and rigidity can be produced at the lowest molding heating temperature.

[0069] From the point of view of a balance between the lightness and rigidity properties of the molded article, the apparent density of the expanded beads is preferably 10 kg / m3 or more and 150 kg / m3 or less, more preferably 15 kg / m3 or more and 100 kg / m3 or less, even more preferably 20 kg / m3 or more and 80 kg / m3 or less, and with particular preference 25 kg / m3 or more and 45 kg / m3 or less. In the past, in particular, in the case of producing a molded article with a low apparent density, it is likely that the molded article will be significantly deformed after demolding and it is difficult to omit the aging step. On the other hand, in the production method of the present disclosure, even when the apparent density is small, the aging step can be omitted and a good-looking molded article can be produced even without aging.

[0070] The apparent density of the expanded beads can be Petition 870260043645, dated 08 / 05 / 2026, page 39 / 189 29 / 69 obtained by immersing the expanded bead group (weight W (g) of the expanded bead group) left for 1 day under conditions of 50% relative humidity, 23°C and 1 atm in the measuring cylinder containing alcohol (e.g., ethanol) at 23°C using a wire screen or similar, obtaining a volume V (L) of the expanded bead group from the increase in alcohol level, dividing the weight of the expanded bead group by the volume of the expanded bead group (W / V) and converting units to [kg / m3].

[0071] From the point of view of further preventing significant shrinkage and deformation of the molded article in the event of omitting the aging step, the ratio between the apparent density of the expanded beads and the bulk density of the expanded beads (i.e., apparent density / bulk density) is preferably 1.7 or more, and more preferably 1.75 or more. On the other hand, the apparent density / bulk density is preferably 2.3 or less, more preferably 2.1 or less, and even more preferably 1.9 or less from the point of view of further increasing the stiffness of the molded article and from the point of view of further improving the appearance.

[0072] The bulk density of expanded beads is obtained as follows. Expanded beads are randomly drawn from the group of expanded beads and placed in the measuring cylinder with a volume of 1 L, a large number of expanded beads are accommodated up to a scale of 1 L, so that they are in a natural state of deposition, the mass W2 [g] of the accommodated expanded beads is divided by the accommodation volume V2 (1 L) (W2 / V2), and the unit is converted to [kg / m3], thus obtaining the bulk density of the expanded beads.

[0073] Expanded beads can be produced, for example, by a method in which polypropylene-based resin particles containing polypropylene-based resin as the base resin are Petition 870260043645, dated 08 / 05 / 2026, page 40 / 189 30 / 69 Dispersed in a dispersion medium (e.g., a liquid), the resin particles are impregnated with a blowing agent, and the resin particles containing the blowing agent are released along with the dispersion medium under low pressure (i.e., a dispersion medium release expansion method). Specifically, it is preferable that the resin particles be dispersed in the dispersion medium in a sealed container and, after heating, a blowing agent is introduced under pressure to impregnate the resin particles. After that, following a step of maintaining the growth of secondary crystals at a constant temperature, it is preferable to obtain expanded beads by releasing the contents into the sealed container at low pressure to expand the resin particles containing the blowing agent.Note that, in the case of fusion-bonded layer formation, resin particles having a multilayered structure including the core layer and the fusion-bonded layer covering the core layer are expanded, resulting in expanded beads with a multilayered structure including the foam layer and the fusion-bonded layer covering the foam layer.

[0074] Resin particles are produced, for example, as follows. To begin, the polypropylene-based resin that will be the base material resin and an additive, such as a cell nucleation agent supplied as needed, are fed into an extruder and heated and kneaded to obtain a melt-mixed resin product. After that, the melt-mixed resin product is extruded into a cylindrical filament having through holes from a small die orifice connected to an extruder tip, cooled, and cut to obtain resin particles. The extruded product is cut, for example, with a pelletizer. A cutting method can be selected from among a filament cutting method, a method of Petition 870260043645, dated 08 / 05 / 2026, page 41 / 189 31 / 69 hot cutting, an underwater cutting method and the like. In this way, cylindrical resin particles with through holes can be obtained. Note that, in the case of forming a melt-bondable layer, the melt-mixed resin product of each raw material is obtained using an extruder to form the core layer and an extruder to form the melt-bondable layer, each melt-mixed product being extruded and joined in a die to form a core-layer composite including a cylindrical core layer in the unexpanded state and a melt-bondable layer in the unexpanded state covering the outer surface of the cylindrical core layer, and the composite is cooled and cut while being extruded into a filament shape from pores of a die attached to a tip of the extruder, obtaining multilayer resin particles.

[0075] The diameter of the resin particles is preferably from 0.1 to 3.0 mm and more preferably from 0.3 to 1.5 mm. In addition, the length / outer diameter ratio of the resin particles is preferably from 0.5 to 5.0 and more preferably from 1.0 to 3.0. Furthermore, the average mass per bead (obtained from the mass of 200 randomly selected beads) is preferably from 0.1 to 20 mg, more preferably from 0.2 to 10 mg, even more preferably from 0.3 to 5 mg, and particularly preferably from 0.4 to 2 mg. The mass ratio of the core layer to the fusion-bonded layer in the case of multilayer resin particles is preferably 99.5:0.5 to 80:20, more preferably 99:1 to 85:15, and even more preferably 97:3 to 90:10. The mass ratio is represented by the core layer:fusion-bonded layer ratio.

[0076] By adjusting the hole diameter dr of the resin particle through holes, the average hole diameter d of the expanded bead through holes can be adjusted to the desired range above. The hole diameter dr of the core layer through holes of Petition 870260043645, dated 08 / 05 / 2026, page 42 / 189 The 32 / 69 resin particle size can be adjusted, for example, by the hole diameter (i.e., the inner diameter of the die) of a small die hole to form the through hole. Furthermore, by adjusting the bead diameter and the average mass of the resin particles, the average outer diameter and average wall thickness of the expanded beads can be adjusted to the desired range mentioned above.

[0077] From the point of view of the most reliable production of expanded beads in which the average hole diameter d of the through holes is less than 1 mm and the ratio d / D of the average hole diameter d to the average outside diameter D is 0.4 or less, the average hole diameter dr of the through holes of the resin particles is preferably less than 0.25 mm, more preferably less than 0.24 mm and even more preferably 0.22 mm or less. From the point of view of the stability of production of resin particles with through holes, the average hole diameter dr of the through holes of the resin particles is preferably 0.1 mm or more.

[0078] Furthermore, from the same point of view, the ratio dr / Dr of the average hole diameter dr to the average outside diameter Dr of the resin particles is preferably 0.4 or less, more preferably 0.3 or less, even more preferably 0.25 or less, and particularly preferably 0.2 or less. From the point of view of the production stability of resin particles having through holes, the ratio dr / Dr of the average hole diameter dr to the average outside diameter Dr of the resin particles is preferably 0.1 or more.

[0079] The average hole diameter dr of the through holes of the resin particles is obtained as follows. 50 or more randomly selected resin particles from the resin particle group are cut perpendicular to the direction of penetration of the through holes at the position where the cut surface area is maximized. Petition 870260043645, dated 08 / 05 / 2026, page 43 / 189 33 / 69 The cut surface of each resin particle is photographed, the cross-sectional area (specifically, the opening area) of the through-hole portions is obtained, the diameter of the perfect virtual circle having the same area as the cross-sectional area of ​​the through-hole portions is calculated, and the arithmetic mean thereof is taken as the average hole diameter dr of the resin particle through-holes. Note that even in the case where the through-hole size of each resin particle is not uniform with respect to the through-hole diameter in the penetration direction, the through-hole diameter of each resin particle is determined by the hole diameter at the position where the cut surface area of ​​the resin particle is maximized as described above.

[0080] The average outside diameter Dr of the resin particles is obtained as follows. 50 or more randomly selected resin particles from the resin particle group are cut perpendicular to the direction of penetration of the through holes at the position where the cut surface area is maximized. The cut surface of each resin particle is photographed, the cross-sectional area (specifically the cross-sectional area that also includes the opening portion of the through holes) of the resin particle is obtained, the diameter of the perfect virtual circle having the same area as the cross-sectional area is calculated, and the arithmetic mean of these values ​​is taken as the average outside diameter Dr of the resin particle.Note that even when the outer diameter of each resin particle is not uniform in the direction of penetration, the outer diameter of each resin particle is determined by the outer diameter at the position where the cross-sectional area of ​​the resin particle in the direction perpendicular to the direction of penetration is maximized, as described above.

[0081] Note that the diameter of the account, the ratio Petition 870260043645, dated 08 / 05 / 2026, page 44 / 189 34 / 69 length / outer diameter and average mass of resin particles in a filament cutting method can be prepared by appropriately altering the extrusion speed, absorption speed, cutting speed, and the like, when the melt-mixed resin product is extruded.

[0082] As a dispersion medium (specifically, the liquid) for dispersing the resin particles obtained as described above in the sealed container, an aqueous dispersion medium is used. The aqueous dispersion medium is a dispersion medium (specifically, a liquid) containing water as the main component. The proportion of water in the aqueous dispersion medium is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Examples of dispersion media other than water in the aqueous dispersion medium include ethylene glycol, glycerin, methanol, and ethanol.

[0083] Additives such as a cell nucleating agent, a crystal nucleating agent, a dye, a flame retardant, a flame retardant auxiliary, a plasticizer, an antistatic agent, an antioxidant, an ultraviolet inhibitor, a light stabilizer, a conductive filler, and an antibacterial agent may be added to the core layer of the resin particles as needed. Examples of cell nucleating agents include inorganic powders such as talc, mica, zinc borate, calcium carbonate, silica, titanium oxide, gypsum, zeolite, borax, aluminum hydroxide, and carbon; organic powders such as a phosphoric acid-based nucleating agent, a phenolic-based nucleating agent, an amine-based nucleating agent, and a polyfluoroethylene-based resin powder. In a case where a cell nucleating agent is added, the content of the cell nucleating agent is preferably 0.01 to 1 part by mass based on 100 parts in Petition 870260043645, dated 08 / 05 / 2026, p. 45 / 189 35 / 69 polypropylene-based resin mass.

[0084] In the dispersion medium release expansion method, it is preferable to add a dispersant to the dispersion medium so that the heated resin particles in the container do not fuse together. The dispersant can be any dispersant, provided it prevents the resin particles from fusing in the container, and can be used regardless of whether the dispersant is organic or inorganic. However, a fine inorganic substance is preferable from the point of view of ease of handling. Examples of dispersants include a clay mineral such as amsnite, kaolin, mica, clay, and the like. The clay mineral can be natural or synthetic. In addition, examples of dispersants include aluminum oxide, titanium oxide, basic magnesium carbonate, basic zinc carbonate, calcium carbonate, and iron oxide. One, two, or more types of dispersants are used. Among these, clay minerals are preferably used as dispersants.The dispersant is preferably added in an amount of about 0.001 to 5 parts by mass per 100 parts by mass of resin particles.

[0085] Note that, in a case where a dispersant is used, an anionic surfactant, such as sodium dodecylbenzenesulfonate, sodium alkylbenzenesulfonate, sodium lauryl sulfate or sodium oleate, is preferably used in combination as a dispersing aid. An additional amount of the dispersing aid is preferably from 0.001 to 1 part by mass per 100 parts by mass of resin particles.

[0086] As a blowing agent to expand the resin particles, a physical blowing agent is preferably used. Examples of physical blowing agents include inorganic physical blowing agents and organic physical blowing agents, and examples of inorganic physical blowing agents include dioxide Petition 870260043645, dated 08 / 05 / 2026, page 46 / 189 36 / 69 carbon, air, nitrogen, helium, argon and the like. In addition, examples of organic physical blowing agents include aliphatic hydrocarbons such as propane, butane and hexane, cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane, and halogenated hydrocarbons such as chlorofluoromethane, trifluoromethane, 1,1-difluoromethane, 1-chloro-1,1-dichloroethane, 1,2,2,2-tetrafluoroethane, methyl chloride, ethyl chloride and methylene chloride. Note that the physical blowing agent can be used alone or in combination with two or more types. Furthermore, inorganic physical blowing agents and organic physical blowing agents can be mixed and used. From the point of view of environmental impact and handling, inorganic physical blowing agents are preferable, and carbon dioxide is more preferably used.In cases where an organic physical blowing agent is used, it is preferable to use n-butane, i-butane, n-pentane, or i-pentane from the point of view of solubility in the polypropylene-based resin and expansion capacity.

[0087] The amount of blowing agent added based on 100 parts by mass of resin particles is preferably from 0.1 to 30 parts by mass and, more preferably, from 0.5 to 15 parts by mass.

[0088] In a production step of expanded beads, as a method of impregnating the resin particles with the expanding agent, a method of dispersing the resin particles in the aqueous dispersion medium in the sealed container, adjusting the pressure of the expanding agent while heating, and impregnating the resin particles with the expanding agent, are preferably used.

[0089] The internal pressure of the sealed container during expansion is preferably 0.5 MPa (G: gauge pressure) or more. On the other hand, the internal pressure of the sealed container is preferably Petition 870260043645, dated 08 / 05 / 2026, page 47 / 189 37 / 69 4.0 MPa (G) or less. Within the above range, expanded beads can be produced safely without risk of breakage, explosion, or similar damage to the sealed container.

[0090] By increasing the temperature of the aqueous dispersion medium in a production step of expanded beads from 1 to 5°C / min, the temperature during expansion can also be adjusted to an appropriate range.

[0091] Expanded beads having the crystal structure in which the melting peak (the resin-intrinsic peak) inherent to the resin and one or more melting peaks (the high-temperature peaks) appear on its high-temperature side in the DSC curve obtained by differential scanning calorimetry (DSC) are obtained, for example, as follows.

[0092] During the heating stage in the production of expanded beads, a holding stage is carried out at a temperature of (melting point of polypropylene-based resin: 20°C) or higher, and below (final melting temperature of polypropylene-based resin) for a sufficient period of time, preferably about 10 to 60 minutes. After that, the temperature is adjusted to a temperature of (melting point of polypropylene-based resin: -15°C) to (final melting temperature of polypropylene-based resin +10°C). Then, if necessary, a two-stage holding stage is carried out at that temperature for a more sufficient period of time, preferably about 10 to 60 minutes. Then, by releasing the expandable resin particles containing the expanding agent from inside the sealed container at low pressure and expanding the expandable resin particles, expanded beads having the crystalline structure described above can be obtained.The expansion is preferably carried out in a sealed container at a temperature of (melting point of polypropylene-based resin: 10°C) or higher, and more preferably at a temperature of. Petition 870260043645, dated 08 / 05 / 2026, p. 48 / 189 38 / 69 (melting point of polypropylene-based resin) or higher and (melting point of polypropylene-based resin +20°C) or lower.

[0093] Furthermore, in the production of expanded beads having a particularly low apparent density, it is possible to carry out the expansion in two stages whereby the expanded beads are loaded into a sealed pressurizable container, pressurized gas, such as air, is introduced under pressure into the interior of the container to increase the internal pressure of the expanded beads, and the expanded beads are heated in the container using a heating medium, such as steam, for a predetermined period of time to obtain the expanded beads having a particularly low apparent density.

[0094] The molded article can be obtained by molding the expanded beads in the mold as described above (i.e., the mold-in-mold method). The mold-in-mold method is performed by filling a mold with the expanded beads and hot-molding the expanded beads using a heating medium, such as steam. Specifically, after the expanded beads are filled into the mold, the heating medium, such as steam, is introduced into the mold to heat the expanded beads to be secondarily expanded and fused together to obtain a molded article with a molding space shape.

[0095] The molded article is formed, for example, by in-mold molding of expanded beads and is composed of a large number of expanded beads bonded together by fusion. The molded article has an open-cell structure. The open-cell structure is a small portion of space that communicates with the exterior of the molded article. The open-cell structure is formed by the complicated connection of formed voids allowing the through holes of a plurality of expanded beads to communicate with each other, voids Petition 870260043645, dated 08 / 05 / 2026, page 49 / 189 39 / 69 formed allowing the through holes of the expanded beads to communicate with the voids formed between the expanded beads, voids formed allowing the voids between the expanded beads to communicate with each other, open cell portions of the expanded beads that constitute the molded article and the like.

[0096] The open cell content of the molded article is 2.5% or more and 12% or less. In a case where the open cell content of the molded article is less than 2.5%, the molded article may be significantly shrunk and deformed if the aging step is omitted. On the other hand, in a case where the open cell content of the molded article exceeds 12%, the appearance and rigidity of the molded article may be damaged. From the point of view of more reliably preventing dimensional change when the aging step is omitted, the open cell content of the molded article is preferably 3% or more, more preferably 4% or more, and even more preferably 4.5% or more.From the point of view that the appearance and rigidity of the molded article can be further improved, the open cell content of the molded article is preferably 10% or less, more preferably 8% or less, even more preferably 7.5% or less, and with particular preference 6% or less.

[0097] From the point of view that dimensional change can be more sufficiently prevented even when the aging step is omitted, the porosity of the molded article is preferably 4% or more, more preferably 4.5% or more, and even more preferably 5% or more. On the other hand, from the point of view of further improving stiffness and appearance, the porosity of the molded article is preferably 12% or less, more preferably 10% or less, and even more preferably 8% or less. The porosity of the molded article can be measured by the measurement method described. Petition 870260043645, dated 08 / 05 / 2026, p. 50 / 189 40 / 69 above.

[0098] The closed-cell content of the molded article is 90% or more. If the content is less than 90%, the appearance and rigidity of the molded article may be compromised. From the point of view of further improving the appearance and rigidity of the molded article, the closed-cell content of the molded article is preferably 91% or more, and more preferably 92% or more.

[0099] The closed-cell content of the molded article is measured in accordance with ASTM 2865-70 Procedure C. Specifically, the closed-cell content of the molded article is measured as follows. To begin, a measuring sample of 2.5 cm length x 2.5 cm width x 2.5 cm height is cut from the central portion of the molded article and the geometric volume Va is obtained. Specifically, Va is a value obtained by vertical dimension [cm] χ horizontal dimension [cm] χ height dimension [cm]. Then, in accordance with Procedure C described in ASTM-D2856-70, the actual volume value Vx of the measuring sample is measured by the air comparison pycnometer (specifically, AccuPyc II 1340 manufactured by Shimadzu Corporation). The closed-cell content is calculated by the following formula (VII). Note that the closed cell rates of the five measurement samples are calculated and the arithmetic mean of these values ​​is adopted as the result. Closed cell content (%) = (Vx - W / ρ) χ 100 / (Va - W / ρ) ... (VII) Vx: actual volume of the measurement samples measured by the above method, i.e., the sum of the volume of the resin that constitutes the measurement samples and the total volume of the cells in the closed-cell portion of the measurement samples (unit: cm3) Va: geometric volume of the measurement samples (unit: cm3) Petition 870260043645, dated 08 / 05 / 2026, page 51 / 189 41 / 69 W: weight of the measurement samples (unit: g)

[00100] The density of the molded article is preferably 10 kg / m3 or more and 100 kg / m3 or less. In this case, the lightness and stiffness properties of the molded article can be improved in a well-balanced way. From the point of view of further improving the stiffness of the molded article, the density of the molded article is more preferably 20 kg / m3 or more, and even more preferably 25 kg / m3 or more. From the point of view of further improving the lightness property of the molded article, the density of the molded article is more preferably 80 kg / m3 or less, and even more preferably 50 kg / m3 or less. The density of the molded article is calculated by dividing the weight (g) of the molded article by the volume (L) obtained from the external dimension of the molded article and performing the unit conversion.Note that, for example, in a case where the molded article has a complicated shape, at least partially, and it is not easy to obtain the volume from the external dimension of the molded article, the volume of the molded article can be obtained by a submersion method.

[00101] Conventionally, in the case of producing a molded article with a low density, the molded article is remarkably easily deformed after demolding and, therefore, it is particularly difficult to omit the aging step. On the other hand, according to the expanded bead molded article in the present disclosure, the aging step can be omitted even when the apparent density is low, and the molded article having the desired shape and excellent appearance and rigidity even without aging is obtained. From the point of view of effectively exhibiting this effect, the density of the molded article is preferably adjusted to the above range.

[00102] From the point of view of further improving mechanical strength, the maximum bending strength of the molded article is, Petition 870260043645, dated 08 / 05 / 2026, p. 52 / 189 42 / 69 preferably, 250 kPa or more, more preferably 300 kPa or more, and even more preferably 320 kPa or more. The maximum bending strength can be measured according to JIS K7221-2:2006 with the maximum bending strength point of the molded article as the maximum bending strength.

[00103] The ratio [S / DE] of the maximum bending strength S of the molded article to the density DE of the molded article is preferably 9 kPa^m3 / kg or more and 15 kPa^m3 / kg or less. In this case, an excellent stiffness effect is obtained in the expanded bead molded article. From the point of view of further improving the stiffness of the molded article, the ratio [S / DE] of the maximum bending strength S of the molded article to the density DE of the molded article is more preferably 9.5 kPa^m3 / kg or more, and even more preferably 10 kPa^m3 / kg or more. Note that the density DE of the molded article to be used in the above calculation means the density of the specimen to be subjected to the maximum bending strength measurement.

[00104] Molded article is also used as a sound-absorbing material, a shock-absorbing material, a damping material and the like in various fields, such as in the field of vehicles, like automobiles, and in the field of construction. Examples

[00105] The present invention will now be described in more detail with reference to examples, but the present invention is by no means limited to these examples.

[00106] The following physical properties were measured and evaluated for the resin, expanded beads, and molded articles used in the examples and comparative examples. Note that the physical properties of the expanded beads were measured and evaluated after the state had been adjusted, allowing the expanded beads to remain for 24 hours under conditions of 50% relative humidity, 23°C, and 1 atm. Petition 870260043645, dated 08 / 05 / 2026, page 53 / 189 43 / 69 Furthermore, the physical properties of the molded article were measured and evaluated using a molded article without undergoing the aging step. Specifically, in the production of a molded article to be described later, the molded article, after demolding, was left to rest for 12 hours under conditions of 50% relative humidity, 23°C, and 1 atm to adjust the state, and the physical properties were measured and evaluated using the molded article. Polypropylene-based resin

[00107] Table 1 shows properties and similarities of the polypropylene-based resin used to produce the expanded beads. Note that the ethylene-propylene copolymer and the ethylene-propylene-butene copolymer used in this example are both random copolymers. Furthermore, the density of the polypropylene-based resin is 900 kg / m3. Table 1 Symbol Material Catalyst Comonomer Flexural Modulus (MPa) Melting Point (°C) MFR (g / 10 min) PP1 ZieglerNatta Ethylene-propylene Random Copolymer Ethylene 3.1% by mass 980 142 8 PP2 ZieglerNatta Ethylene-propylene Random Copolymer Ethylene 1.4% by mass 1470 153 7 PP3 Mixed Resin of PP1 (80% by weight) and PP2 (20% by weight) — Ethylene 2.8% by mass 1070 144 8 PP4 ZieglerNatta Ethylene-propylene Random Copolymer Ethylene 3.1% by mass Butene 3.8% by mass 650 133 6 Monomer component content in polypropylene-based resin

[00108] The content of the monomer component in the resin based on Petition 870260043645, dated 08 / 05 / 2026, page 54 / 189 44 / 69 Polypropylene (specifically, ethylene-propylene copolymer and ethylene-propylene-butene copolymer) was obtained by a known method based on the IR spectrum. Specifically, the known method refers to a method described in the Polymer Analysis Handbook (edited by the Polymer Analysis Research Council, Japan Society for Analytical Chemistry, publication date: January 1995, publisher: Kinokuniya, page number and item name: 615 to 616 II. 2.3 2.3.4 Propylene / ethylene copolymer, 618 to 619 II. 2.3 2.3.5 Propylene / butene copolymer (Copolymer of propylene / butene), that is, a quantification method based on the relationship between a value obtained by correcting the absorbance of ethylene and butene with a predetermined coefficient and the thickness of a film-like test specimen. More specifically, to begin, the polypropylene-based resin was hot-pressed in an environment at 180°C to be formed into a film, thus preparing a plurality of test specimens with different thicknesses. Then, the absorbances at 722 cm⁻¹ and 733 cm⁻¹ derived from ethylene (A722 and A733) and the absorbances at 766 cm⁻¹ derived from butene (Azee) were read, measuring the IR spectrum of each test specimen. Then, for each test specimen, the ethylene component content in the polypropylene-based resin was calculated using the following formulas (1) to (3).The value obtained by calculating the arithmetic mean of the ethylene component content for each test specimen was taken as the ethylene component content (unit: % by weight) in the polypropylene-based resin. (K'733)c = 1 / 0.96{(K'733)a-0.268(K'722)a} ... (1) (K'722)c = 1 / 0.96{(K'722)a-0.268(K'722)a} ... (2) Ethylene component content (%) = 0.575 {(K'722)c + (K'733)c} ... (3)

[00109] However, in formulas (1) to (3), K'a represents an apparent absorption coefficient at each wavenumber (K'a = A / ρί), K'c represents a corrected absorption coefficient, A represents absorbance, ρ represents Petition 870260043645, dated 08 / 05 / 2026, page 55 / 189 45 / 69 represents the density of the resin (unit: g / cm3), and et represents the thickness of the film-like specimen (unit: cm). Note that formulas (1) to (3) above can be applied to random copolymers.

[00110] In addition, for each test specimen, the butene component content in the polypropylene-based resin was calculated using the following formula (4). The value obtained by the arithmetic mean of the butene component content obtained for each test specimen was taken as the butene component content (%) of the polypropylene-based resin. Butene component content (%) = 12.3 (A766 / L) ... (4)

[00111] However, in formula (4), A represents absorbance and L represents the thickness (mm) of the film-like test specimen. Flexural modulus of polypropylene-based resin

[00112] Polypropylene-based resin was thermally pressed at 230°C to prepare a 4 mm sheet, and a specimen 80 mm long x 10 mm wide x 4 mm thick was cut from the sheet. The flexural modulus of this specimen was obtained according to JIS K7171:2008. Note that the radius R1 of the penetrator and the radius R2 of the support base are both 5 mm, the distance between the support points is 64 mm, and the test speed is 2 mm / min. Melting point of polypropylene-based resin

[00113] The melting point of the polypropylene-based resin was obtained according to JIS K7121:1987. Specifically, (2) The case of measuring the melting temperature after definitive heat treatment was used as a state-adjustment, the DSC curve was obtained by increasing the temperature of the specimen subjected to the state-adjustment from 30°C to 200°C with a heating rate of 10°C / min, and the temperature at the apex of the melting peak was defined as the melting point. Note that a differential heat flow scanning calorimeter (manufactured by SII NanoTechnology Inc., model number: DSC7020) was used as the measuring device. Melt flux content of polypropylene-based resin Petition 870260043645, dated 08 / 05 / 2026, page 56 / 189 46 / 69

[00114] The molten mass flow rate (i.e., MFR) of the polypropylene-based resin was measured under temperature conditions of 230°C and a load of 2.16 kg according to JIS K7210-1:2014. Melt mass flow rate of polypropylene-based resin

[00115] The melt mass flow rate (i.e., MFR) of the polypropylene-based resin was measured under conditions of 230°C temperature and a 2.16 kg load according to JIS K7210-1:2014.

[00116] Table 2 shows properties and similarities of multilayer resin particles and expanded beads. Petition 870260043645, dated 08 / 05 / 2026, page 57 / 189 47 / 69 Table 2 Expanded Bead Expanded Bead A Expanded Bead B Expanded Bead C Expanded Bead D Expanded Bead E Expanded Bead F Multilayer Resin Bead Foamed Layer — PP1 PP1 PP1 PP3 PP1 PP1 Fusion Layer — PP4 PP4 PP4 PP4 PP4 PP4 Fusion Bondable Layer Mass Ratio % 5 5 5 5 5 5 Resin Particle Mass mg 1.5 1.5 1.5 1.5 1.5 1.5 First Expansion Stage Expansion Temperature °C 150.1 147 146.2 153.6 149.5 146.4 Carbon Dioxide Pressure MPa(G) 2.6 3.8 3.8 2.6 1.9 3.3 Mass Ratio Times 19.1 38.3 36.0 18.5 17.0 45.0 Second Expansion Stage Internal Pressure MPa(G) 0.5 - - 0.5 0.5 - Drum Pressure MPa(G) 0.035 - - 0.035 0.035 - Expanded Account Bulk Density kg / m3 24.0 23.5 25.0 23.9 25.2 20.0 Bulk Ratio Times 37.5 38.3 36.0 37.7 35.7 45.0 Apparent Density kg / m3 42.6 41.6 44.5 42.3 40.3 55.5 Apparent Density / Bulk Density - 1.78 1.77 1.78 1.77 1.60 2.78 Closed Cell Content % 98.4 96.0 96.5 97.8 96.7 980 Peak heat of high temperature J / g 14.5 13.4 16.5 14.4 14.0 14.9 Average diameter of through hole d millimeters 0.70 0.95 0.89 0.75 - 3.31 Average External Diameter D millimeters 3.69 3.98 3.63 3.80 3.71 3.78 d / D - 0.19 0.24 0.25 0.20 - 0.88 Average wall thickness t millimeters 1.49 1.52 1.37 1.53 - 0.23 t / D - 0.40 0.38 0.38 0.40 - 0.06 Petition 870260043645, dated 08 / 05 / 2026, p. 58 / 189 48 / 69 Average hole diameter d of through holes

[00117] The average hole diameter of the through holes of the expanded beads was obtained as follows. 100 expanded beads randomly selected from the expanded bead group after state adjustment were cut perpendicular to the direction of penetration of the through holes at the position where the area of ​​the cut surface was substantially maximum. The cut surface of each expanded bead was photographed and the cross-sectional area (the opening area) of the through-hole portions in the cross-sectional photograph was obtained. The diameter of the perfect virtual circle having the same area as that of the cross-section of the through-hole portions was calculated, and the arithmetic mean of these was taken as the average hole diameter (d) of the through holes of the expanded beads. Average external diameter D

[00118] The average outside diameter of the expanded beads was obtained as follows. 100 randomly selected expanded beads from the expanded bead group after state adjustment were cut perpendicular to the direction of penetration of the through holes at the position where the area of ​​the cut surface was substantially maximum. The cut surface of each expanded bead was photographed to obtain the cross-sectional area of ​​the expanded bead (including the through-hole opening portion). The diameter of the perfect virtual circle having the same cross-sectional area as the expanded bead was calculated, and the arithmetic mean of these was taken as the average outside diameter (D) of the expanded beads. Average wall thickness t

[00119] The average wall thickness of the expanded beads was obtained using the following formula (5). Average wall thickness t = (average outside diameter D average hole diameter d) / 2 ... (5) Petition 870260043645, dated 08 / 05 / 2026, page 59 / 189 49 / 69 Bulk density and bulk ratio

[00120] The bulk density of the expanded beads was obtained as follows. Expanded beads were randomly selected from the expanded bead group after state adjustment, placed in a measuring cylinder with a volume of 1 L, a large number of expanded beads were accommodated up to the 1 L scale so that they were in a natural deposition state, the mass W2 [g] of the accommodated expanded beads was divided by the accommodation volume V2 (1[L]) (W2 / V2), and the unit was converted to [kg / m3], obtaining the bulk density of the expanded beads. In addition, the bulk ratio [times] of the expanded beads was obtained by dividing the density [kg / m3] of the resin that constitutes the foam layer of the expanded beads by the bulk density [kg / m3] of the expanded beads. Apparent density

[00121] The apparent density of the expanded beads was obtained as follows. To begin, the measuring cylinder containing ethanol at a temperature of 23°C was prepared, and an arbitrary quantity of the expanded bead group (a mass W1 [g] of the expanded bead group) after state adjustment was immersed in ethanol in the measuring cylinder using a wire screen. Then, considering the volume of the metal screen, the volume V1 [L] of the expanded bead group was measured, read from the rising water level. The apparent density of the expanded beads was obtained by dividing the mass W1 [g] of the expanded bead group placed in the measuring cylinder by the volume V1 [L] (W1 / V1) and converting the units to [kg / m3]. Closed cell content

[00122] The closed-cell content of the expanded beads was measured using an air comparison pycnometer based on Procedure C of ASTM-D2856-70. Specifically, it was obtained as follows. Using expanded beads having a total volume of approximately 20 cm3 Petition 870260043645, dated 08 / 05 / 2026, page 60 / 189 50 / 69 after state adjustment as a measuring sample, the apparent volume Va was accurately measured by the ethanol immersion method as described below. The measuring sample whose apparent volume Va was measured was sufficiently dried and then the actual volume value Vx of the measuring sample measured by the AccuPyc II 1340 manufactured by Shimadzu Corporation was measured according to Procedure C described in ASTM-D2856-70. Then, based on these volume values ​​Va and Vx, the closed-cell content was calculated by the following formula (5), and the average value of the five samples (N = 5) was taken as the closed-cell content of the expanded beads. Closed cell content (%) = (Vx - W / ρ) x 100 / (Va - W / ρ) ... (5) where Vx: actual volume of the expanded beads measured by the method above, i.e., the sum of the resin volume that constitutes the expanded beads and the total volume of the closed-cell portion in the expanded beads (unit: cm3). Va: apparent volume (unit: cm3) of the expanded beads measured from the rise in water level when the expanded beads are immersed in the measuring cylinder containing ethanol. W: weight of the measurement sample for expanded beads (unit: g), ep: density of the resin that constitutes the expanded beads (unit: g / cm3). Heat from peak high temperature of expanded beads

[00123] An expanded bead was collected from the expanded bead group after state adjustment. Using the expanded bead as a test specimen, the DSC curve was obtained when the test specimen was heated from 23°C to 200°C at a heating rate of 10°C / min by differential scanning calorimeter (specifically, DSC.Q 1000). Petition 870260043645, dated 08 / 05 / 2026, page 61 / 189 51 / 69 manufactured by TA Instruments). The area of ​​the high-temperature peak was obtained from the DSC curve, and this was taken as the heat of the high-temperature peak.

[00124] The above measurement was performed on five expanded accounts, and the arithmetic mean value is shown in Table 2.

[00125] The above measurement was performed on five expanded accounts, and the arithmetic mean value is shown in Table 2. Molded article

[00126] Tables 3 and 4 show the properties and similarities of the molded article. Petition 870260043645, dated 08 / 05 / 2026, page 62 / 189 52 / 69 Table 3 Example No. / Comparative Example No. Example 1 Example 2 Example 3 Example 4 Expanded Bead Expanded Bead A Expanded Bead B Expanded Bead C Expanded Bead D Molding Step Pre-pressurization performed or not performed - Not performed Not performed Not performed Not performed Internal bead pressure MPa(G) — — — — Crack width % 20 20 20 20 Molding pressure MPa(G) 0.22 0.22 0.22 0.22 Molded Article (Physical Property, Evaluation) Corrected open cell content % 3.9 5.3 5.3 4.1 Closed cell content % 92.3 91.1 90.8 91.7 Density of molded article kg / m3 34 33 36 34 Porosity % 12.0 6.6 9.9 11.9 Non-Aged Moldability Evaluation - Appearance Assessment - AAAA 50% Compressive Strength kPa 239 223 247 236 Density (compression) of the molded cut article kg / m3 33 32 36 33 Maximum bending strength S kPa 353 327 372 348 Density (bending) of the molded cut article DE kg / m3 33 32 36 33 S / DE kPa-eu3 / kg 10.6 10.2 10.3 10.5 Petition 870260043645, dated 08 / 05 / 2026, page 63 / 189 53 / 69 Table 4 Example No. / Comparative Example No. Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Expanded Bead Expanded Bead E Expanded Bead F Expanded Bead F Expanded Bead A Expanded Bead A Expanded Bead A Molding Step Pre-pressurization performed or not performed - Performed Not performed Performed Performed Performed Performed Internal bead pressure MPa(G) 0.15 — 0.15 0.15 0.08 0.15 Crack width % 10 20 20 10 20 20 Molding pressure MPa(G) 0.28 0.22 0.22 0.3 0.22 0.3 Molded Article (Physical Property, Evaluation) corrected open cell content % 0.4 35.8 17.4 0.6 0.9 0.3 Closed-cell content % 96.7 60.9 79.5 96.3 97.0 96.8 Density of molded article kg / m3 30 28 30 30 33 33 Porosity % 5.4 47.2 20.5 8.1 10.0 35. Evaluation of Non-Aged Moldability - xooxxx Appearance Evaluation - ACCAAA 50% Compressive Stress kPa 231 151 174 207 238 245 Density (compression) of the molded cut article kg / m3 29 28 28 28 33 32 Maximum Flexural Strength S kPa 326 201 245 287 349 357 Density (flexural) of the molded cut article DE kg / m3 29 28 28 28 33 32 S / DE kPa · m3 / kg 11.1 7.1 8.7 10.3 10.7 11.1 Petition 870260043645, dated 08 / 05 / 2026, page 64 / 189 54 / 69 Pre-pressurization stage

[00127] In a case where the pre-pressurization step was performed before molding the expanded beads, the pre-pressurization was performed as follows. Specifically, the expanded beads were placed in the sealed container, the expanded beads were pressurized with compressed air, and the internal pressures shown in Tables 3 and 4 were applied to the expanded beads before molding. Note that the internal pressure of the expanded beads is a measured value as follows. The internal pressure P (MPa (G)) of the expanded beads was calculated by the formula P = (W / M) χ R χ T + V, where Q (g) was the weight of the group of expanded beads in a state where the internal pressure was increased immediately before loading the beads into the mold, U (g) was the weight of the group of expanded beads after a lapse of 48 hours, and the difference between the weight Q (g) and U (g) was the increase in the amount of air W(g).In the formula, M represents the molecular weight of air, R represents the gas constant, T represents the absolute temperature, V represents the volume (L) obtained by subtracting the volume of the resin of the base material of the expanded bead group from the apparent volume of the expanded bead group and, in this example, M = 28.8 (g / mol), R = 0.0083 (MPa-U(K-mol)) and T = 296 (K).

[00128] Note that, in the case where the pre-pressurization step was not performed, a symbol - was displayed in the internal pressure column of the bill in the table. In this case, the internal pressure of the bill is 0 MPaG (i.e., the internal pressure is equal to atmospheric pressure). Open cell content

[00129] The open cell content (i.e., the corrected open cell content) was measured according to ASTM 2856-70 Procedure B. An automatic dry densitometer (specifically, AccuPyc II 1340 manufactured by Shimadzu Corporation) was used as the measuring device. To begin, the state of the molded article was adjusted. Petition 870260043645, dated 08 / 05 / 2026, page 65 / 189 55 / 69 allowing the molded article to remain at 23°C for 12 hours. Then, the first test specimen, with a cubic shape measuring 2.5 cm long x 2.5 cm wide x 2.5 cm high, was cut from the central portion of the molded article and its geometric volume Va [unit: cm3] was measured. Specifically, Va is a value obtained by the vertical dimension [cm] χ horizontal dimension [cm] χ height dimension [cm]. A real volume value V1 [unit: cm3] of the first test piece was measured with the dry automatic densitometer. Then, the first test specimen was divided into 8 equal parts to obtain a second cubic test specimen with a size of 1.25 cm long x 1.25 cm wide x 1.25 cm high. Open cell content

[00130] The open cell content (i.e., the corrected open cell content) was measured according to ASTM 2856-70 Procedure B. An automatic dry densitometer (specifically, AccuPyc II 1340 manufactured by Shimadzu Corporation) was used as the measuring device. To begin, the state of the molded article was adjusted by allowing the molded article to remain at 23°C for 12 hours. Then, the first test specimen, with a cubic shape of 2.5 cm length x 2.5 cm width x 2.5 cm height, was cut from the central portion of the molded article and its geometric volume Va [unit: cm3] was measured. Specifically, Va is a value obtained by the vertical dimension [cm] χ horizontal dimension [cm] χ height dimension [cm]. The actual volume V1 [unit: cm3] of the first test specimen was measured with the automatic dry densitometer.Next, the first specimen was divided into 8 equal parts to obtain a second cubic specimen with dimensions of 1.25 cm in length x 1.25 cm in width x 1.25 cm in height. Then, the actual volume V2 [unit: cm3] of the second specimen was measured using the dry automatic densitometer. Note that the actual volume V2 of... Petition 870260043645, dated 08 / 05 / 2026, page 66 / 189 56 / 69 second test specimen is the total value of the actual volumes of the eight pieces cut from the first test specimen. The open cell content Co [unit:%] is calculated by the following formula (6). Five first test specimens were cut from the molded article, the open cell content was calculated by the method above, and the arithmetic mean value of the same was used as the result. Co = (Va-2V1+V2)x100 / Va... (6) Closed cell content

[00131] The closed-cell content of the molded article was measured according to ASTM 2865-70 Procedure C. Specifically, the measurement was performed as follows. To begin, a measurement sample of 2.5 cm length x 2.5 cm width x 2.5 cm height was cut from the central portion of the molded article and the geometric volume Va was obtained. Specifically, Va is a value obtained by vertical dimension [cm] χ horizontal dimension [cm] χ height dimension [cm]. Then, according to Procedure C described in ASTM 2856-70, the actual volume value Vx of the measurement sample was measured using an air comparison pycnometer (specifically, AccuPyc II 1340 manufactured by Shimadzu Corporation).

[00132] The closed cell content was calculated using the following formula (7). Note that the closed cell rates of the five measurement samples were calculated, and the arithmetic mean of these was adopted as the result. Closed cell content (%) = (Vx - W / ρ) χ 100 / (Va - W / ρ) ...(7) Vx: actual volume of the measurement samples measured by the above method, i.e., the sum of the volume of the resin that constitutes the measurement samples and the total volume of the cells in the closed-cell portion of the measurement samples (unit: cm3) Va: geometric volume of the measurement samples (unit: Petition 870260043645, dated 08 / 05 / 2026, page 67 / 189 57 / 69 cm3) W: weight of measurement samples (unit: g) Density of the molded article

[00133] The density (kg / m3) of the molded article was calculated by dividing the weight (g) of the molded article by the volume (L) obtained from the external dimension of the molded article and converting the value to a unit. Evaluation of moldability without aging.

[00134] An assessment of moldability without aging was performed by evaluating the fusion bonding ability and recoverability of the molded article without performing the aging step of leaving the molded article to rest for a predetermined period of time in a high-temperature atmosphere adjusted to a temperature of approximately 60°C to 80°C after demolding. Specifically, in the production of a molded article, which is described further below, the molded article left to rest at 23°C for 12 hours after demolding was used to evaluate the fusion bonding ability and recoverability, which are described further below, and one case of obtaining a molded article with acceptable fusion bonding ability and recoverability whose evaluation results were rated as Good and other cases were rated as Poor. (Ability to bond by fusion)

[00135] The molded article was bent and broken, the number C1 of expanded beads present on the broken surface and the number C2 of broken expanded beads were obtained, and the ratio between the number of broken expanded beads and the number of expanded beads present on the broken surface (i.e., the fracture content of the material) was calculated. The fracture content of the material is calculated from the formula C2 / C1 x 100. The above measurement was performed five times using Petition 870260043645, dated 08 / 05 / 2026, page 68 / 189 58 / 69 different test specimens were analyzed, and the fracture content of the material was obtained. When the arithmetic mean value of the material's fracture content was 90% or more, this was defined as acceptable. Recoverability

[00136] A thickness near four corners (specifically, 10 mm inward from the corner in the central direction) and a thickness at the center (a portion equally divided in two, both longitudinally and laterally) of a molded article obtained using a flat surface mold 300 mm long, 250 mm wide, and 60 mm thick, were measured, respectively. Then, the ratio (unit:%) between the thickness of the thinnest portion and the thickness of the thickest portion was calculated among the measured portions, and the case where the ratio was 95% or more was considered acceptable. Appearance assessment

[00137] The evaluation was carried out based on the following criteria. A: The molded article has a good surface condition in which the voids between the beads are small on the surface of the molded article and the irregularities caused by through holes and the like are not noticeable. B: Irregularities due to gaps between beads and / or through holes and similar imperfections are slightly observed on the surface of the molded article. C: Irregularities due to gaps between beads and / or through holes and similar defects are noticeably observed on the surface of the molded article. 50% compressive stress

[00138] A test specimen 50 mm long x 50 mm wide x 25 mm thick was cut from the central portion of the molded article so that a film on the surface of the molded article did not Petition 870260043645, dated 08 / 05 / 2026, p. 69 / 189 59 / 69 was included in the test specimen. According to JIS K 6767:1999, a compression test was performed at a compression rate of 10 mm / min to obtain 50% compressive stress of the molded article. Note that the density of the test specimen used for measuring the 50% compressive stress was obtained in the same way as in measuring the density of the molded article, and the density (compression) of a cutout of the molded article is shown in Tables 3 and 4. Maximum bending strength

[00139] Flexural strength was measured according to JIS K72212:2006, and a maximum flexural strength point of the molded article was measured as the maximum flexural strength. Specifically, a specimen 120 mm long, 25 mm wide, and 20 mm thick was cut from the molded article, except for the surface film. Using this specimen, flexural strength was measured according to JIS K7221-2:2006, except that the descent speed of a pressurized wedge was set to 10 mm / min, the distance between the support points was set to 100 mm, the radius of a tip of the support base was set to 5 mm, and the radius of a tip of the pressurized wedge was set to 5 mm. Note that the density of the specimen used for measuring the maximum bending strength was obtained in the same way as in the measurement of the density of the molded article, and the density (bending) of the molded article cutout is shown in Tables 3 and 4. Porosity of the molded article

[00140] The porosity of the molded article was obtained as follows.

[00141] A rectangular parallelepiped-shaped test specimen (20 mm long x 100 mm wide x 20 mm high) was cut from the central portion of the molded article. The specimen was immersed in the measuring cylinder containing ethanol, and the actual volume Vc [L] of the specimen was obtained from the amount of increase in Petition 870260043645, dated 08 / 05 / 2026, page 70 / 189 60 / 69 liquid ethanol level. In addition, the apparent volume Vd [L] was obtained from the external dimension of the test specimen. The porosity of the molded article was obtained from the real volume Vc and the apparent volume Vd obtained, by the following formula (8). Porosity (%) = [(Vd - Vc) / Vd] x 100 ... (8)

[00142] Next, a method will be described for producing the expanded accounts and the molded article in Examples 1 to 6 and Comparative Examples 1 to 7. Example 1 Production of expanded polypropylene-based beads (expanded beads A)

[00143] Polypropylene-based resin 1 (abbreviated as PP1) was melt-mixed at a defined maximum temperature of 245°C in the extruder to form the core layer for obtaining the melt-mixed resin product. Note that PP1 is a random copolymer of ethylene-propylene and has an ethylene component content of 3.1% by mass. The characteristics of PP1 are shown in Table 1. In addition, polypropylene-based resin 4 (abbreviated as PP4) was melt-mixed at a fixed maximum temperature of 245°C in the extruder to form the melt-bondable layer for obtaining the melt-mixed resin product. Then, the respective melt-mixed resin products were extruded from the extruder to form the core layer and the melt-bondable layer, from the tip of a co-extrusion die having a small orifice to form the through holes.At this point, the respective melt-bonded resin products were joined in a die to form the sheath-core composite including the tubular core layer in the non-foamed state and the melt-bondable layer in the non-foamed state covering the outer surface of the tubular core layer. The composite was extruded from the pores of the die fixed at the tip of the... Petition 870260043645, dated 08 / 05 / 2026, page 71 / 189 61 / 69 extruder in a tubular wire with through holes, and the wire was cooled with cold water, the water temperature being adjusted to 10°C while the wire was removed and then cut with the pelletizer so that the mass was about 1.5 mg each. In this way, multilayer resin particles were obtained, composed of a tubular core layer with through holes and a fusion-bondable layer covering the core layer. Note that, in the production of the multilayer resin particles, zinc borate as a cell-adjusting agent was supplied to the extruder to form the central layer, and 500 ppm by mass of zinc borate were contained in the polypropylene-based resin.

[00144] 1 kg of multilayer resin particles was placed in a sealed 5 L container along with 3 L of water as a dispersing medium, and 0.3 parts by mass of kaolin as a dispersant and 0.004 parts by mass of a surfactant (sodium alkylbenzene sulfonate) were added to 100 parts by mass of the multilayer resin particles in the sealed container. Carbon dioxide as an expanding agent was added to the inside of the sealed container, the sealed container was then sealed, and the inside of the sealed container was heated to an expansion temperature of 150.1°C while being stirred. The pressure inside the container (i.e., the impregnation pressure and the carbon dioxide pressure) at this time was 2.6 MPa (G). After maintaining at the same temperature (i.e., 150.1°C) for 15 minutes, the contents of the container were released at atmospheric pressure to obtain the expanded beads. The expanded beads were dried at 23°C for 24 hours.

[00145] Subsequently, the expanded beads were placed in a pressure-resistant container and air was forced into the container, increasing the pressure inside the container, impregnating the cells with air and increasing the internal pressure of the expanded beads. Then, Petition 870260043645, dated 08 / 05 / 2026, page 72 / 189 62 / 69 steam was supplied to the expanded beads (one-stage expanded beads) removed from the pressure-resistant container so that the pressure (i.e., the drum pressure) in the pressure-resistant container was the pressure shown in Table 2, and the expanded beads were heated under atmospheric pressure. The pressures (i.e., the internal pressures) of the cells in the one-stage expanded beads removed from the pressure-resistant container were the values ​​shown in Table 2. As described above, the apparent density of the one-stage expanded beads was reduced to obtain the expanded beads (two-stage expanded beads). In this way, expanded beads with a bulk ratio of 37.5 were obtained. This is referred to as expanded beads A. Production of molded articles

[00146] In the production of the molded article, expanded beads dried at 23°C for 24 hours were used. Then, an exhaustion step was performed in which the expanded beads were loaded into a flat plate mold (specifically a metal die) 300 mm long x 250 mm wide x 60 mm thick, and the crack width was set to 20% (i.e., 12 mm). The metal die was fixed, and steam was supplied from both surfaces of the metal die for 5 seconds to preheat. After that, steam was supplied from one side of the metal die surface to heat that side until a pressure lower than the predetermined molding pressure of 0.08 MPa (G) was reached.Next, steam was supplied from the other side of the metal die surface until a pressure lower than the predetermined molding pressure by 0.04 MPa (G) was reached to perform the one-sided heating, and then heating (i.e., main heating) was carried out until the predetermined molding pressure was reached. After the heating was complete, a. Petition 870260043645, dated 08 / 05 / 2026, page 73 / 189 63 / 69 pressure was released and the molded article was cooled with water until the surface pressure from an expansion force of the molded article reached 0.04 MPa (G), and then demolded to obtain the molded article. The open cell content of the molded article thus produced was 3.9%. Note that the predetermined molding pressure was defined as a value at which the molding pressure is the lowest among the molding pressures at which an acceptable product can be obtained in the meltability assessment described above. Example 2

[00147] Expanded beads (i.e., expanded beads B) with a bulk ratio of 38.3 were obtained in the same manner as in the production of expanded beads A, except that the expansion temperature and carbon dioxide pressure were changed to the values ​​shown in Table 2 and the two-stage expansion was not performed. The molded article was obtained in the same manner as in Example 1, except that expanded beads B were used. The open cell content of the molded article thus produced was 5.3%. Example 3

[00148] Expanded beads (i.e., expanded beads C) with a bulk ratio of 36.0 were obtained in the same manner as in the production of expanded beads A, except that the expansion temperature and carbon dioxide pressure were changed to the values ​​shown in Table 2 and the two-stage expansion was not performed. Furthermore, the molded article was obtained in the same manner as in Example 1, except that expanded beads C were used. The open cell content of the molded article thus produced was 5.3%. Example 4

[00149] Expanded beads (i.e., expanded beads D) having a bulk ratio of 37.7 times were obtained in the same manner as in the production of expanded beads A, except that a mixed resin PP3 Petition 870260043645, dated 08 / 05 / 2026, page 74 / 189 64 / 69 obtained by mixing PP1 and PP2 in a mixing ratio of 80% by weight: 20% by weight was used as polypropylene-based resin to form the foam layer, and the expansion temperature was changed to the value shown in Table 2. Furthermore, the molded article was obtained in the same way as in Example 1, except that expanded beads D were used. The open-cell content of the molded article thus produced was 4.1%. Example 5

[00150] Expanded beads (i.e., expanded beads G) with a bulk ratio of 18.0 times were obtained in the same manner as in the production of expanded beads A, except that the expansion temperature was changed to the value shown in Table 2 and the two-stage expansion was not performed. Furthermore, the molded article was obtained in the same manner as in Example 1, except that expanded beads G were used. The open cell content of the molded article thus produced was 5.1%. Example 6

[00151] The molded article was obtained in the same manner as in Example 1, except that in the molding step, pre-pressurization was carried out so that the internal pressure of the expanded beads before being loaded into the mold became the value shown in Table 4, and the crack width was changed to the value shown in Table 4. The open cell content of the molded article thus produced was 3.5%. Comparative Example 1

[00152] The expanded beads (i.e., expanded granules E) having a bulk expansion of 35.7 were obtained in the same manner as in the production of expanded granules A, except that the resin particles without through holes were produced during the production of the multilayer resin particles, and the expansion temperature and Petition 870260043645, dated 08 / 05 / 2026, page 75 / 189 65 / 69 the carbon dioxide pressure was changed to the values ​​shown in Table 2. Furthermore, the molded article was obtained in the same way as in Example 1, except that expanded spheres E were used, and in the molding step, pre-pressurization was performed so that the internal pressure of the expanded beads before filling the beads in the mold became the value shown in Table 4, and the crack width and molding pressure were changed to the values ​​shown in Table 4. The open cell content of the molded article thus produced was 0.4%.

[00153] Note that, since expanded beads without passage holes, as in this example, have insufficient steam passage during molding, the appearance and rigidity of the molded article are significantly deficient if pre-pressurization is not performed. Consequently, in this example, pre-pressurization was performed as described above. Comparative Example 2

[00154] Expanded beads (i.e., expanded F beads) with a bulk ratio of 45.0 times were obtained in the same manner as in Example 1, except that the inner diameter of a small hole in the coextruded die provided with the small hole to form the through holes during the production of multilayer resin particles was changed, the expansion temperature and carbon dioxide pressure were changed to the values ​​shown in Table 2, and the two-stage expansion was not performed. Furthermore, the molded article was obtained in the same manner as in Example 1, except that expanded F beads were used. The open cell content of the molded article thus produced was 35.8%. Comparative Example 3

[00155] The molded article was obtained in the same way as in Comparative Example 2, except that in the molding step, the Petition 870260043645, dated 08 / 05 / 2026, page 76 / 189 66 / 69 pre-pressurization was performed so that the internal pressure of the expanded beads before being loaded into the mold became the value shown in Table 4. The open cell content of the molded article thus produced was 17.4%. Comparative Example 4

[00156] The molded article was obtained in the same manner as in Example 1, except that in the molding step, pre-pressurization was carried out so that the internal pressure of the expanded beads before being loaded into the mold became the value shown in Table 4, and the crack width and molding pressure were changed to the values ​​shown in Table 4. The open cell content of the molded article thus produced was 0.6%. Comparative Example 5

[00157] Furthermore, the molded article was obtained in the same manner as in Example 1, except that in the molding step, pre-pressurization was carried out so that the internal pressure of the expanded beads before being loaded into the mold became the value shown in Table 4; the open cell content of the molded article thus produced was 0.9%. Comparative Example 6

[00158] Furthermore, the molded article was obtained in the same manner as in Example 1, except that in the molding step, pre-pressurization was carried out so that the internal pressure of the expanded beads before being loaded into the mold became the value shown in Table 4, and the molding pressure was changed to the value shown in Table 4. The open cell content of the molded article thus produced was 0.3%. Comparative Example 7

[00159] Expanded accounts (i.e., expanded H accounts) with a bulk ratio of 36.7 times were obtained in the same way as in Petition 870260043645, dated 08 / 05 / 2026, page 77 / 189 67 / 69 Example 1, except that the inner diameter of the small hole in the coextruded die provided with the small hole to form the through holes was changed, the expansion temperature and carbon dioxide pressure were changed to the values ​​shown in Table 2, and the two-stage expansion was not performed during the production of the multilayer resin particles. Furthermore, the molded article was obtained in the same way as in Example 1, except that expanded H beads were used. The open cell content of the molded article thus produced was 15.0%.

[00160] As can be understood from Tables 2 to 3, according to Examples 1 to 6, the molded article having the desired shape and being excellent in appearance and rigidity can be produced even when the aging step is omitted.

[00161] On the other hand, as can be seen from Table 2 and Table 4 in Comparative Example 1, the open cell content of the molded article was too low because the molded article was produced using expanded beads without through holes. As a result, in a molding without aging, significant shrinkage and deformation of the molded article occurred (i.e., recoverability is not acceptable) and a good molded article could not be obtained.

[00162] In Comparative Example 2, the open cell content of the molded article was excessively high because the molded article was produced using expanded beads having an excessively large average through-hole diameter. As a result, the appearance of the molded article was poor and the rigidity was also compromised.

[00163] Comparative Example 3 is an example where molding was performed so that the open cell content was lower than that of Comparative Example 2. In Comparative Example 3, although the open cell content could be reduced, the reduction was insufficient and, as a result, it was not possible to obtain the molded article. Petition 870260043645, dated 08 / 05 / 2026, page 78 / 189 68 / 69 with good appearance and rigidity.

[00164] Comparative Example 4 is an example where the molded article was produced using the same expanded beads as Example 1 under different molding conditions. In Comparative Example 4, because the open cell content of the molded article was too low, significant shrinkage and deformation of the molded article occurred in molding without aging (i.e., recoverability is not acceptable), and it was not possible to obtain a good molded article.

[00165] In Comparative Example 5, similarly to Comparative Example 4, expanded beads similar to those in Example 1 were used, and the molded article was produced under different molding conditions. In Comparative Example 5, the open cell content of the molded article was higher than that of Comparative Example 4, but the open cell content was still too low, so that in molding without aging, significant shrinkage and deformation of the molded article occurred (i.e., recoverability is not acceptable), and a good molded article could not be obtained.

[00166] In Comparative Example 6, similarly to Comparative Example 4, expanded beads similar to those in Example 1 were used, and the molded article was produced under different molding conditions. In Comparative Example 6, the open cell content of the molded article is lower than in Comparative Example 4. In Comparative Example 6, because the open cell content of the molded article was too low, significant shrinkage and deformation of the molded article occurred in molding without aging (i.e., recoverability is not acceptable), and a good molded article could not be obtained.

[00167] In Comparative Example 7, although the average hole diameter of the through holes of the expanded beads was smaller than in Petition 870260043645, dated 08 / 05 / 2026, page 79 / 189 69 / 69 Comparative Example 2: The molded article was produced using expanded beads in which the average hole diameter of the through holes was still too large, so the open cell content of the molded article was too high. As a result, the appearance of the molded article was poor and the rigidity was also compromised. Petition 870260043645, dated 08 / 05 / 2026, page 80 / 189

Claims

1 / 3 CLAIMS 1. An in-mold molded article of expanded polypropylene-based resin beads (1) formed by fusion-bonded expanded tubular spheres of polypropylene-based resin, each having a through hole (11) between them, characterized in that a closed-cell content of the in-mold molded article of expanded beads measured in accordance with ASTM 2865-70 Procedure C is 90% or more, a corrected open-cell content of the in-mold molded article of expanded beads measured in accordance with ASTM 2856-70 Procedure B is 2.5% or more and 12% or less, the expanded beads (1) each having a foam layer (2) consisting of a polypropylene-based resin and a fusion-bondable layer (3) covering the foam layer (2), the polypropylene-based resin constituting the foam layer (2) is a random copolymer of ethylene-propylene containing 2.0% or more by mass and 5.0% or less by mass of ethylene component,the polypropylene-based resin that constitutes the foam layer (2) has a melting point of 135 °C or more and 145 °C or less, the polypropylene-based resin that constitutes the foam layer (2) has a molten mass flow rate of 7 g / 10 min or more and 10 g / 10 min or less measured under the conditions of a test temperature of 230 °C and a load of 2.16 kg based on JIS K7210-1:2014, and a closed cell content of the expanded beads (1) measured in accordance with ASTM 2865-70 Procedure C is 90% or more, the average diameter d of the through holes (11) of the dimensions Petition 870260043645, dated 08 / 05 / 2026, page. 185 / 189 2 / 3 expanded (1) is less than 1 mm, and the ratio [d / D] between the average diameter d of the holes and the average external diameter D of the expanded elevations (1) is 0.4 or less, the melt-bondable layer (3) is made of a polypropylene-based resin with a melting point Tms of 120 °C or more and 140 °C or less and a molten mass flow rate of 7 g / 10 min to 10 g / 10 min,measured under the conditions of a test temperature of 230 °C and a load of 2.16 kg, based on the JIS K72101:2014 standard, and a Tmc-Tms difference between the melting point Tmc of the foam layer (2) and the melting point Tms of the melt-bondable layer (3) is 15 °C or less.

2. In-mold molded article of expanded polypropylene-based resin beads (1), according to claim 1, characterized in that the corrected open cell content of the expanded bead molded article (1) is 4% or more and 8% or less.

3. In-mold molded article of expanded polypropylene-based resin beads (1), according to claim 1 or 2, characterized in that a ratio [S / DE] of a maximum flexural strength S of the in-mold molded article of expanded beads measured in accordance with JIS K7221-2:2006 with a maximum point of the maximum flexural strength of the molded article as the maximum flexural strength for a density DE of the in-mold molded article of expanded beads (1) is 9 kPa^m3 / kg or more and 15 kPa^m3 / kg or less.

4. In-mold molded article of expanded polypropylene-based resin beads (1), according to claim 1 or 2, characterized in that the density of the molded article is 20 kg / m3 or more and 50 kg / m3 or less, the density being calculated by dividing the weight (g) of the molded article by the volume (L) obtained from the external dimensions of the molded article. Petition 870260043645, dated 08 / 05 / 2026, p. 186 / 189 3 / 3

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