Aromatic polyester resin foam molded body and method for producing same

Abstract

One of the purposes of the present invention is to provide: an aromatic polyester resin foam molded body for a core material of a composite structure member, the aromatic polyester resin foam molded body having a small maximum peak height (Sp) without having a slit mark on the surface; and a method for producing the same.　The present invention pertains to an aromatic polyester resin foam molded body for a core material of a composite structure member. The foam molded body contains 90% by mass or more of a polyethylene terephthalate, and has a surface crystallinity of 20-30% and a thermal history peak temperature of 125-200°C as determined by a differential scanning calorimeter (DSC). The maximum peak height (Sp) of the surface of the foam molded body is 0.25 mm or less. The fusion rate of the foam particles that constitute the foam molded body is 60% or more.

Description

Aromatic polyester resin foam molded product and method for producing same

[0001] The present invention relates to an aromatic polyester resin foam molded article and a method for producing the same.

[0002] In-mold foam molded articles are used as core materials for composite structural components due to their advantages, such as light weight and thermal insulation. A method for producing in-mold foam molded articles involves filling a cavity in a mold with foamed beads, heating the foamed beads to expand, and then thermally fusing the expanded beads together using the expansion pressure to produce a foam having a desired shape (sometimes referred to as the bead expansion molding method). A known bead expansion molding method involves introducing a heating medium, such as steam, into the mold cavity to heat and expand the foamed beads (steam heating method). In the steam heating method, a slit is provided in the mold to allow the heating medium, such as steam, to be introduced into the mold cavity. This results in slit marks on the surface of the resulting molded article (see Patent Document 1).

[0003] Another method for producing an in-mold foamed article has been reported, in which a molten resin raw material into which a foaming agent has been injected is extrusion foam-molded to produce a cylindrical molded article, which is then cut open to form a sheet, which is then used as a core material (Patent Document 2).

[0004] When a foamed molded article is used as a core material, the slit marks can prevent the core material from being integrated with the skin material. Furthermore, depending on the type and thickness of the skin material and the conditions for compounding, small protrusions caused by the slit marks can be formed on the surface of the composite structural member, which can impair the surface smoothness of the composite structural member.

[0005] In the method of producing a cylindrical molded product by extrusion foam molding and then cutting it open to form a sheet, no slit marks are left, but it is difficult to produce a thick core material and a step of forming the product into a sheet after foam molding is required.

[0006] JP 2014-080022 A JP 2016-069460 A

[0007] An object of the present invention is to provide an aromatic polyester resin foam molded article for use as a core material for a composite structural member, which has no slit marks on its surface (preferably the surface to be laminated with a skin material, more preferably the surface to be laminated with a skin material and having the largest area, even more preferably the surface to be laminated with a skin material and having the largest area, excluding areas corresponding to the end areas in plan view).An object of the present invention is to provide an aromatic polyester resin foam molded article for use as a core material for a composite structural member, which has a small maximum peak height (Sp) on its surface (preferably the surface to be laminated with a skin material, more preferably the surface to be laminated with a skin material and having the largest area, even more preferably the surface to be laminated with a skin material and having the largest area, excluding areas corresponding to the end areas in plan view), and a method for producing the same.An object of the present invention is to provide an aromatic polyester resin foam molded article for use as a core material for a composite structural member, which has a high fusion rate of foamed particles within the core, and a method for producing the same. An object of the present invention is to provide a method for producing an aromatic polyester resin foam molded article for use as a core material for a composite structural member, which method enables the production of a thick core material.

[0008] The present inventors have discovered that by heating and expanding foamed beads in a heated mold without introducing steam into the molding space of the mold (hot press foam molding method), it is possible to obtain a foamed molded article for a core material having a surface that is free of slit marks and has a small maximum peak height (Sp) (preferably the surface onto which a skin material is to be laminated, more preferably the surface onto which a skin material is to be laminated and which has the largest area, and even more preferably the surface onto which a skin material is to be laminated and which has the largest area and which excludes areas corresponding to the end areas in plan view), despite it being a bead foam molding method, and that the fusion rate of the foamed beads inside the foamed molded article obtained in this way is surprisingly not low.

[0009] The present invention typically includes the following aspects. Item 1. A foam molded aromatic polyester resin for use as a core material of a composite structural member, the foam molded product containing 90% by mass or more of polyethylene terephthalate, the foam molded product having a surface crystallinity of 20 to 30% and a thermal history peak temperature of 125 to 200°C as measured by a differential scanning calorimeter (DSC), the foam molded product having a maximum peak height (Sp) on the surface of 0.25 mm or less, and the foam particles constituting the foam molded product having a fusion rate of 60% or more. Item 2. A composite structural member comprising the foam molded product according to Item 1 as a core material. Item 3. a first step of placing foamed beads of the aromatic polyester resin in the molding space of the mold and closing the mold; and a second step of heating the mold after the first step to expand and heat-seal the foamed beads contained in the molding space to form the foamed mold; the mold has a vent hole on a side surface thereof that communicates with the molding space, and gas in the molding space can be discharged to the outside of the mold through the vent hole during heating in the second step; and the foamed molded article contains 90% by mass or more of polyethylene terephthalate. A method for producing a foam molded article, wherein the foam molded article has a surface crystallinity of 20 to 30% and a thermal history peak temperature of 125 to 200°C as measured by a differential scanning calorimeter (DSC), a maximum peak height (Sp) on the surface of the foam molded article of 0.25 mm or less, and a fusion rate of the foamed beads constituting the foam molded article of 60% or more. Item 4. The method for producing a foam molded article according to Item 3, wherein in the first step, the foamed beads are pressurized by closing the mold, and in the second step, the pressurized foamed beads are expanded and heat-fused. Item 5. The foam molded article according to Item 1, which has no slit marks on its surface. Item 6. A composite structural member comprising the foam molded article according to Item 5 as a core material.Item 7. The method for producing a foam molded article according to Item 3 or 4, wherein the foam molded article has no slit marks on its surface.

[0010] The present invention provides an aromatic polyester resin foam molded article for use as a core material for a composite structural member, which has no slit marks on its surface (preferably the surface to which a skin material is to be laminated, more preferably the surface to which a skin material is to be laminated and which has the largest area, and even more preferably the surface to which a skin material is to be laminated and which has the largest area and which excludes the area corresponding to the edge area in plan view) and has a small maximum peak height (Sp), as well as a method for producing the same. Using this foam molded article as a core material makes it possible to produce a composite structural member that does not have unevenness on the surface of the skin material due to slit marks, even when a thin skin material is used. The present invention also provides an aromatic polyester resin foam molded article for use as a core material for a composite structural member, which has a high fusion rate of foamed particles inside the core material, as obtained by hot press foam molding, and a method for producing the same. Using a foam molded article with a high fusion rate inside as a core material can improve the mechanical strength of the resulting composite structural member. According to the present invention, a method for producing an aromatic polyester resin foam molded article for use as a core material for a composite structural member can be provided, which requires less energy during foam molding than methods such as steam heating, which use steam to heat and foam foamed beads in a mold.

[0011] 1A is a perspective view, and FIG. 1B is a front view and a plan view of a foam molded article for illustrating the surface to be measured for maximum peak height (Sp). A schematic perspective view of a foam molded article according to one embodiment. A schematic perspective view of a molding die used in one embodiment. A schematic view of one embodiment of a method for producing a foam molded article. A cross-sectional view illustrating a production apparatus used to obtain expanded beads in the examples. A cross-sectional view illustrating a production apparatus used to obtain expanded beads in the examples. A cross-sectional view illustrating a production apparatus used to obtain expanded beads in the examples. A differential scanning calorimeter (DSC) measurement curve obtained from a surface portion sample of a foam molded article produced in Comparative Example 1 (heating temperature 90°C). A differential scanning calorimeter (DSC) measurement curve obtained from a surface portion sample of a foam molded article produced in Comparative Example 2 (heating temperature 100°C). A differential scanning calorimeter (DSC) measurement curve obtained from a surface portion sample of a foam molded article produced in Example 1 (heating temperature 120°C). 1 is a differential scanning calorimeter (DSC) measurement curve obtained from a surface portion sample of a foam molded article produced in Example 2 (heating temperature 140°C). 2 is a differential scanning calorimeter (DSC) measurement curve obtained from a surface portion sample of a foam molded article produced in Example 3 (heating temperature 160°C). 3 is a differential scanning calorimeter (DSC) measurement curve obtained from a surface portion sample of a foam molded article produced in Example 4 (heating temperature 180°C). 4 is a differential scanning calorimeter (DSC) measurement curve obtained from a surface portion sample of a foam molded article produced in Comparative Example 4 (steam heating method, heating temperature 120°C). 5 is a differential scanning calorimeter (DSC) measurement curve obtained from a surface portion sample of a foam molded article produced in Comparative Example 5 (no vent hole, heating temperature 120°C).

[0012] In this specification, the phrase "comprising" is intended to encompass the phrases "consisting essentially of" and "consisting of." In the numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in a certain stage can be arbitrarily combined with the upper or lower limit of a numerical range in the same paragraph or in another stage. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from the example. In this specification, with respect to a numerical range, "to" means equal to or greater than the leftmost numerical value and equal to or less than the rightmost numerical value. For example, "0.5 to 10% by mass" and "0.5% to 10% by mass" both mean "0.5% by mass or greater and 10% by mass or less." Furthermore, with respect to a numerical range, "equal to or greater than" means "equal to or greater than," and "equal to or less than" means "equal to or less than."

[0013] (Aromatic polyester resin foam molded article) The aromatic polyester resin foam molded article of the present invention is a fused body of expanded aromatic polyester resin particles. More specifically, it is a molded article in which a plurality of expanded aromatic polyester resin particles are thermally fused together to form an integrated body. The aromatic polyester resin foam molded article may contain 90% by mass or more of an aromatic polyester resin. In this specification, a molded article molded by heating and expanding expanded beads in a mold is also referred to as a bead foam molded article.

[0014] (Aromatic polyester resin) The aromatic polyester resin may be a polyester containing an aromatic dicarboxylic acid component and a diol component, and examples thereof include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc., and polyethylene terephthalate is preferred. The aromatic polyester resin may be used alone or in combination of two or more.

[0015] In addition to the aromatic dicarboxylic acid component and the diol component, the aromatic polyester resin may contain, as constituent components, for example, tricarboxylic acids such as trimellitic acid, tetracarboxylic acids such as pyromellitic acid, and other polycarboxylic acids having three or more valences, anhydrides thereof, triols such as glycerin, and polyhydric alcohols having three or more valences, such as tetraols such as pentaerythritol.

[0016] The aromatic polyester resin may include a modified aromatic polyester resin crosslinked by a crosslinking agent. As the crosslinking agent, a known agent may be used, for example, an acid dianhydride such as pyromellitic anhydride, a polyfunctional epoxy compound, an oxazoline compound, an oxazine compound, etc. The crosslinking agent may be used alone or in combination of two or more.

[0017] When the aromatic polyester resin is modified by crosslinking with a crosslinking agent, the aromatic polyester resin and the crosslinking agent are supplied to an extruder during the production of expanded aromatic polyester resin beads, and the aromatic polyester resin is crosslinked with the crosslinking agent in the extruder. From the viewpoint of performing extrusion foaming well, the amount of crosslinking agent supplied to the extruder is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 1 part by mass, per 100 parts by mass of the aromatic polyester resin.

[0018] The mass average molecular weight (Mw) of the aromatic polyester resin is preferably 45,000 to 100,000, and more preferably 60,000 to 90,000, in order to provide excellent extrusion foamability and excellent secondary foamability of the resulting expanded beads. When the aromatic polyester resin constituting the expanded beads is a modified aromatic polyester resin, the mass average molecular weight (Mw) of the aromatic polyester resin means the mass average molecular weight of the modified aromatic polyester resin.

[0019] The mass average molecular weight (Mw) of an aromatic polyester resin refers to the polystyrene (PS) equivalent mass average molecular weight measured using gel permeation chromatography (GPC). Specifically, the mass average molecular weight is measured as follows: 0.5 mL of hexafluoroisopropanol (HFIP) and 0.5 mL of chloroform are added to 5 mg of sample in this order and dissolved (immersion time: 6.0±1.0 hours (complete dissolution)) to obtain a sample solution. After confirming that the sample is completely dissolved in the solution, chloroform is added to the sample solution to dilute it to a volume of 10 mL and shaken to mix. The sample solution is filtered through a non-aqueous 0.45 μm syringe filter manufactured by Shimadzu GLC Corporation to obtain a filtrate. The filtrate is measured using a chromatograph under the following measurement conditions. The mass average molecular weight (Mw) is determined from a previously prepared standard polystyrene calibration curve. Apparatus used: Tosoh Corporation "HLC-8320GPC EcoSEC" gel permeation chromatograph (built-in RI detector and UV detector) (GPC measurement conditions) Columns: Sample side: Guard column = Tosoh Corporation TSK guard column HXL-H (6.0 mm x 4.0 cm) x 1 Measurement column = Tosoh Corporation TSKgel GMHXL (7.8 mm I.D. x 30 cm) x 2 in series Reference side: Resistance tube (0.1 mm inner diameter x 2 m) x 2 in series Column temperature = 40°C Mobile phase = chloroform Mobile phase flow rate: Sample side pump = 1.0 mL / min Reference side pump = 0.5 mL / min Detector: UV detector Wavelength: 254 nm Injection volume: 15 μL Measurement time: 10 min - 32 min Runtime: 20 min Sampling pitch: 500 msec. Standard polystyrene samples for the calibration curve were "STANDARD SM-105" and "STANDARD SH-75" manufactured by Showa Denko K.K., with mass average molecular weights of 5,620,000, 3,120,000, 1,250,000, 442,000, 151,000, 53,500, 17,000, 7,660, 2,900, and 1,320.The polystyrene standards for the calibration curve were grouped into groups A (5,620,000, 1,250,000, 151,000, 17,000, 2,900) and B (3,120,000, 442,000, 53,500, 7,660, 1,320), and then 2 mg, 3 mg, 4 mg, 4 mg, and 4 mg of A were weighed and dissolved in 30 mL of chloroform. Similarly, 3 mg, 4 mg, 4 mg, 4 mg, and 4 mg of B were weighed and dissolved in 30 mL of chloroform. The polystyrene standard calibration curve was obtained by injecting 50 μL of each of the prepared A and B solutions and creating a calibration curve (cubic equation) from the retention times obtained after measurement. The mass-average molecular weight was calculated using the calibration curve.

[0020] The aromatic polyester resin foam molded article may have a surface crystallinity of 20 to 30% and a thermal history peak temperature of 125 to 200°C, as measured by a differential scanning calorimeter (DSC).

[0021] The crystallinity of the surface of the foamed molded article may be 21 to 26%. The crystallinity of the foamed molded article is determined by the methods described in JIS K7122:1987 and JIS K7122:2012, and more specifically, by the methods described in the Examples.

[0022] The thermal history peak temperature of the surface of the foamed molded article is preferably 130 to 200° C. The thermal history peak temperature of the foamed molded article is determined by the method described in the Examples.

[0023] The aromatic polyester resin foam molded article may have a maximum peak height (Sp) on its surface of 0.25 mm or less. The maximum peak height (Sp) on the surface is preferably 0.01 to 0.25 mm, 0.01 to 0.20 mm, 0.01 to 0.15 mm, or 0.01 to 0.12 mm. The maximum peak height (Sp) is determined by a method using a measuring device in accordance with ISO 25178, and more specifically, by the method described in the Examples.

[0024] The surface to be measured for the maximum peak height (Sp) is preferably a surface onto which a skin material is to be laminated, and is the surface, in a projection (plan view) with that surface facing up, excluding the area from the long side of the projection view to a length equivalent to 10% of the average length of the long and short sides of the projection view (the sum of the lengths of the long and short sides divided by 2) and the area from the short side of the projection view to a length equivalent to 10% of the average length of the long and short sides of the projection view (also referred to in this specification as the "surface excluding the area corresponding to the end area in the plan view"); more preferably, it is the surface with the largest area onto which a skin material is to be laminated, excluding the area corresponding to the end area in the plan view.

[0025] The surface excluding the area corresponding to the plan view end area will be described with reference to FIG. 1. While FIG. 1 shows a foam molded article of a specific shape, the shape of the foam molded article is not limited to this. FIG. 1 shows a perspective view (A), a front view, and a plan view (B) of the foam molded article. The length of the long side E1 in the plan view is 20 cm, and the length of the short side E2 is 10 cm. The average length of the long side E1 and the short side E2 is 15 cm, and 10% of that is 1.5 cm. The area extending from the long side E1 to 1.5 cm is region F1, and the area extending from the short side E2 to 1.5 cm is region F2. Regions F1 and F2 are the "plan view end area." The area excluding areas F1 and F2 from the plan view is region F3 (17 cm x 7 cm). The surface f3 of the foam molded article corresponding to region F3 is the "surface excluding the area corresponding to the plan view end area." In addition, in FIG. 1, the "areas corresponding to the plan view end areas" are areas f1 and f2 on the surface, which correspond to areas F1 and F2.

[0026] The aromatic polyester resin foam molded article is a thermally fused article of foamed beads. The fusion rate of the foamed beads constituting the interior of the thermally fused article (i.e., the foamed beads inside the foam molded article) may be 60% or more. The fusion rate may be 60 to 90%, 60 to 85%, 70% or more, 75% or more, or 80% or more. The fusion rate can be determined by counting the breaks of 150 foamed beads within any range on the fracture surface of a foam molded article measuring 200 mm x 200 mm x 10 mm thick, divided into two pieces; in detail, it is determined by the method described in the Examples.

[0027] (Method for producing an aromatic polyester resin foam molded article) In the method for producing an aromatic polyester resin foam molded article of the present invention, aromatic polyester resin-containing foamed beads filled in a mold are heated by hot press molding and expanded to form a molded article. Therefore, compared to a steam heating method in which the foamed beads in the mold are heated and expanded by steam introduced into the mold through a slit in the mold, this method is superior in that there are no slit marks on the surface of the foam molded article (preferably the surface where a skin material is to be laminated, more preferably the surface where a skin material is to be laminated and having the largest area, and even more preferably the surface where a skin material is to be laminated and having the largest area and excluding the area corresponding to the end area in plan view), and the energy required for foam molding is small. This production method is suitable for producing the aromatic polyester resin foam molded article of the present invention.

[0028] One embodiment of the method for producing an aromatic polyester resin foam molded article of the present invention is a method for producing an aromatic polyester resin foam molded article using a molding mold having a molding space for molding the foam molded article, wherein the molding mold has a pair of molding members arranged opposite each other, and is configured so that the molding space can be opened and closed and the volume of the molding space can be changed by moving the pair of molding members toward and away from each other, and the method includes a first step of placing foamed beads of the aromatic polyester resin in the molding space of the molding mold and closing the molding mold, and a second step of, after the first step, heating the molding mold to expand and heat-seal the foamed beads contained in the molding space to form the foam molded article.

[0029] In this manufacturing method, when the molding die has vent holes on its side surface, gas within the molding space can be discharged to the outside of the molding die during the heating in the second step.

[0030] In the first step, the foamed beads can be pressurized by closing the molding die, and in the second step, the pressurized foamed beads can be expanded and heat-sealed.

[0031] The molding die is usually a pair of two mold members, a male mold and a female mold, which can be opened and closed freely, and the molding space is formed when the mold is closed.

[0032] Hereinafter, an embodiment of the manufacturing method of the present invention will be described, mainly taking as an example the case of manufacturing a plate-shaped expanded bead molded product 100 (length 200 mm, width 200 mm, thickness 10 mm) as shown in Figure 2. As shown in Figure 2, the expanded bead molded product 100 of this embodiment is formed by thermally fusing a plurality of expanded aromatic polyester resin beads 60 together after expansion. Both the expanded aromatic polyester resin beads 60 and the expanded bead molded product 100 of this embodiment contain 90 mass% or more of aromatic polyester resin.

[0033] The bead foam molded body 100 of this embodiment is a flat plate as shown in Figure 2, and the vertical direction in Figure 2 will be referred to as the thickness direction D1 below. The left-right direction in Figure 2 will also be referred to as the width direction D2, and the depth direction in Figure 2 will also be referred to as the length direction D3. Either or both of the upper and lower surfaces of the bead foam molded body 100 shown in Figure 2 may be surfaces onto which a skin material is to be laminated. The bead foam molded body 100 of this embodiment is a molded product produced using a molding die, and the thickness direction D1 coincides with the opening and closing direction of the molding die. The molding die used in this embodiment includes a pair of molding members arranged opposite each other, and is configured so that the molding space can be opened and closed and the volume of the molding space can be changed by moving the pair of molding members closer and farther apart.

[0034] First, a method for producing the bead foam molded product 100 will be described with reference to Figures 3 and 4. The expanded aromatic polyester resin beads 60 filled into the mold can be prepared according to a general method for producing expanded beads used in bead expansion molding. For example, an aromatic polyester resin material containing polyethylene naphthalate and polyethylene terephthalate, and optionally a crosslinking agent, can be supplied to an extruder and melt-kneaded in the presence of a foaming agent to prepare a molten mixture, which can be extruded and foamed to prepare an extruded foam, and the extruded foam can be cut to prepare expanded beads (also referred to as pre-expanded beads).

[0035] In the manufacturing method of this embodiment, an aromatic polyester resin material and, if necessary, a crosslinking agent are supplied to an extruder, and melt-kneaded in the presence of a foaming agent to prepare a melt-kneaded mixture, and the melt-kneaded mixture is extruded and foamed to prepare an extruded foam, and the extruded foam is cut to prepare expanded beads (also referred to as pre-expanded beads) 60'; STEP 1; a molding die M (FIG. 3) is prepared, which has a molding space Mv corresponding to the shape (in this embodiment, "plate-shaped") of the bead expansion molded body 100 to be manufactured, and a vent hole V (height 1 mm, length 100 mm) penetrating from the molding space Mv to the outside of the mold, and a plurality of expanded beads 60' are placed in the molding space Mv of the molding die M; STEP 3; by closing the molding die M, the plurality of expanded beads 60' placed in the molding space Mv are pressurized with a mold material to compress the expanded beads 60'; and STEP 4; and STEP 5 is carried out in which the foamed beads 60 that have been expanded by heating and thermally fused to each other are filled into the molding space Mv to form a foamed bead body 100 having a shape corresponding to the molding space Mv inside the molding mold M, and STEP 6 is carried out in which the molding mold M is cooled to cool the foamed bead body 100 inside.

[0036] As described above, in the manufacturing method of a bead foam molded body of this embodiment, a bead foam molded body 100 in which a plurality of expanded beads 60 are heat-fused to one another is manufactured using a molding mold M equipped with a molding space Mv and vent holes V for molding the bead foam molded body 100. By using a molding mold M equipped with vent holes V, gas in the molding space Mv can be discharged to the outside of the molding mold M during foam molding. This is advantageous in that there are no slit marks on the surface of the foam molded body, the maximum peak height (Sp) on the surface is small, and the fusion rate inside the foam molded body is improved.

[0037] The mold M used in this embodiment comprises a pair of mold members arranged to face each other, and is configured so that the molding space can be opened and closed and the volume of the molding space can be changed by moving the pair of mold members toward and away from each other (FIG. 3). More specifically, the mold M used in this embodiment comprises a female mold Ma and a male mold Mb arranged opposite each other in the vertical direction so that the mold mating surface MP is a horizontal plane. That is, the mold M of this embodiment is configured so that the vertical direction is the opening and closing direction.

[0038] The female mold Ma is disposed below the mold mating surface MP and has an accommodating recess Ma1 that is recessed downward from the mold mating surface MP at a position corresponding to the center of the mold mating surface MP and opens upward (toward the male mold Mb), and is configured to be able to accommodate foamed resin particles (foamed particles 60') before heat fusion in the accommodating recess Ma1. The female mold Ma has a vent hole V penetrating its side wall so that gas in the molding space Mv can be discharged to the outside of the molding mold M during foam molding.

[0039] The male mold Mb is disposed above the mold mating surface MP and has a protrusion Mb1 that protrudes downward (toward the female mold Ma) from the mold mating surface MP at a position corresponding to the center of the mold mating surface MP.

[0040] The cross-sectional shape of the protrusion Mb1 of the male mold Mb in a horizontal plane is the same from the base end (upper end) in the protrusion direction to the tip end (lower end), and in this embodiment, is a square prism. The cross-sectional shape of the space formed in the accommodation recess Ma1 of the female mold Ma is the same from the lower end to the upper end, and is a square prism whose dimension in the thickness direction D1 is longer than that of the protrusion Mb1 of the male mold Mb. In other words, the accommodation recess Ma1 is formed so that its recess depth is deeper than the protrusion dimension of the protrusion Mb1.

[0041] The molding die M of this embodiment is formed so that the recess depth of the installation recess Ma1 of the female die Ma is deeper than the protrusion height of the protrusion Mb1 of the male die Mb, so that even when the protrusion Mb1 enters the installation recess Ma1 and the female die Ma and the male die Mb are abutted at the mold mating surface MP, the tip of the protrusion Mb1 does not reach the bottom of the installation recess Ma1, and a molding space Mv having a rectangular parallelepiped shape (in this embodiment, a "flat square plate shape") is formed inside. That is, in the molding die M of this embodiment, the wall surface of the female die Ma at the bottom of the installation recess Ma1 and the tip surface (lower end surface) of the protrusion Mb1 form molding surfaces that define the molding space Mv.

[0042] As described above, the molding die M of this embodiment is configured so that the volume of the molding space Mv can be changed by moving the pair of mold members (female die Ma and male die Mb) closer to or farther away from each other.

[0043] In the method for producing a bead foam molded body of this embodiment, a mold M is used, and a first step (STEP 1-3) is performed in which a plurality of expanded aromatic polyester resin particles (expanded particles 60') composed of the resin composition are placed in the molding space Mv of the mold M and the mold is closed. After the first step, a second step (STEP 4-6) is performed in which the expanded particles (expanded particles 60') placed in the molding space Mv are heated to a fusion-bondable state using the heated mold M, thereby expanding and thermally fusing the expanded particles (expanded particles 60') to each other, thereby producing the bead foam molded body 100. During heating in the second step, gas within the molding space Mv can be discharged to the outside of the mold through a vent hole V in the mold M. This is advantageous in that there are no slit marks on the surface of the foam molded body, the maximum peak height (Sp) on the surface is reduced, and the fusion rate within the foam molded body is improved. The mold M may be heated in the first step or at a stage prior to the first step, or may be heated after the completion of the first step. In order to make the expanded beads fusion-compatible more quickly, the first step is preferably carried out using a mold whose molding surface is heated to a temperature equal to or higher than the glass transition temperature of the aromatic polyester resin.

[0044] The size of the expanded beads is not particularly limited, and they are usually formed to have an average particle diameter of 0.5 to 10 mm, more preferably 1.0 to 5 mm. The average particle diameter of the expanded beads means the diameter of a sphere having the same volume as the average volume per expanded bead. The average volume per expanded bead can be determined, for example, as follows.

[0045] (Method of determining average volume) A sample cup for an air comparison type hydrometer is prepared, and an arbitrary number N (pieces) of approximately 50 to 100 foamed resin beads are placed in the sample cup. The foamed beads are generally conditioned for 12 hours or more in a space adjusted to 23°C and 65% RH. Next, the total volume V (mm ３) is measured by the 1-1 / 2-1 atmospheric pressure method using an air comparison hydrometer. The air comparison hydrometer is calibrated using standard balls (large 28.9 cc, small 8.5 cc). The volumetric air comparison hydrometer can be, for example, a commercially available product from Tokyo Science Co., Ltd. under the trade name "Air Comparison Hydrometer 1000 Type." The average volume of the expanded beads is then calculated by the following formula: Average volume (mm ３ ) = V / N

[0046] The bead foam molded body 100 formed from the expanded beads preferably has an expansion ratio of 2 or more. The expansion ratio is more preferably 2.5 or more, and particularly preferably 3 or more. In order to ensure that the foam molded body exhibits excellent strength, the expansion ratio is preferably 50 or less. The expansion ratio may be 40 or less, 30 or less, or 20 or less.

[0047] The bead foam molded body 100 formed from the expanded beads preferably has a bulk density of 675 g / L or less. The bulk density is more preferably 540 g / L or less, and particularly preferably 450 g / L or less. The bulk density is preferably 27 g / L or more in order to provide the foam molded body with excellent strength. The bulk density may be 34 g / L or more, 45 g / L or more, or 68 g / L or more.

[0048] When the expanded beads are placed in the molding space of the mold in the first step, the amount of the expanded beads placed (the volume of the expanded beads including the spaces between the expanded beads (apparent volume)) can be, for example, 0.5 to 3 times the volume of the molding space, and preferably 1 to 2 times. If the amount of the expanded beads placed is more than 1 time the volume of the molding space, the expanded beads will be pressurized when placed. This pressurized state of the expanded beads when placed is advantageous in that there are no slit marks on the surface of the foamed molded article, the maximum peak height (Sp) on the surface is reduced, and the fusion rate inside the foamed molded article is increased.

[0049] In the second step, the heating temperature of the mold may be, for example, 105 to 195° C., and preferably 120 to 180° C. A heating temperature within this range is advantageous in that the foamed beads are sufficiently fused, the fusion rate inside the foamed molded article is high, there are no slit marks on the surface of the foamed molded article, and the maximum peak height (Sp) on the surface is small.

[0050] In the second step, gas within the molding space can be discharged to the outside of the mold through vent holes provided on the side of the mold. The provision of vent holes is advantageous in that it improves the expandability of the expanded beads and improves the fusion rate inside the foamed molded article. The shape and size of the opening of the vent hole (particularly the opening on the molding space side) may be any shape and size that prevents all or part of the expanded beads contained in the molding space from entering the opening of the vent hole. The vent hole has an opening on the molding space side and an opening on the outside of the mold. The shapes of both openings may be the same or different. The shape of the opening of the vent hole may be, for example, round, elliptical, polygonal (rectangle, pentagon, hexagon, etc.), etc.

[0051] The number of vent holes may be one or more and is not particularly limited. From the viewpoint of efficiently discharging gas from the molding space, it is preferable that there are more than one vent hole per mold, and more preferably 2, 4, 8, 12, 16, etc. Furthermore, the number of vent holes per side surface of the mold may be one or more, and when there are more than one vent hole, it may be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] The vent hole is preferably located on the side of the mold that forms the molding space, closer to the surface opposite the surface being pressurized. For example, when the mold is pressurized from above, the vent hole opening on the side of the mold is preferably located near the bottom of the molding space from the viewpoint of efficient exhaust (FIGS. 3 and 4). The vent hole opening on the side of the mold may be located within a range of 20% or less, 18% or less, 16% or less, 15% or less, 13% or less, 12% or less, 11% or less, or 10% or less of the height of the side of the molding space from the bottom of the molding space (the reference plane for height; height 0), and may be within a range of 0% or more, 0.0001% or more, 0.001% or more, or 0.01% or more. These upper and lower limits may be appropriately combined to form a numerical range. For example, 0.0001% and 20% may form a range of 0.0001 to 20%. In the case of the mold used in the examples, the height of the side surface of the molding space is 10 mm, and the vent hole opening is located at a height of 1 mm from the bottom surface of the molding space, so the vent hole opening is located in an area within 10% of the height of the side surface of the molding space from the bottom surface of the molding space.

[0053] The area of ​​one side surface that forms the molding space and has a vent hole (the area including the vent hole opening) and the area of ​​the opening of the vent hole (when there are multiple vent holes on the side surface, the total area of ​​the openings of all the vent holes) may be 0.5 to 8%, 0.75 to 7%, or 1 to 6% of the area of ​​the side surface.

[0054] As mentioned above, the size of the opening of the vent hole may be any size that prevents all or part of the expanded beads contained in the molding space from entering the opening of the vent hole. The size of the opening of the vent hole may be such that, if the diameter of the largest circle that can fit into the opening (also referred to as the "maximum circle diameter") is B (mm), B is 20 to 55%, 25 to 50%, and preferably 20 to 45% of the average particle diameter (mm) of the expanded beads. The maximum circle diameter B may be, for example, 0.5 to 2.5 mm, and preferably 0.8 to 1.5 mm.

[0055] In the second step, the expanded beads are preferably expanded and heat-sealed under pressure. The amount of expanded beads accommodated in the second step (the volume (apparent volume) of the expanded beads including the spaces between the expanded beads) can be, for example, 0.5 to 3 times the volume of the molding space, and preferably 1 to 2 times. If the amount is more than 1 time the volume of the molding space, the expanded beads will be pressurized during heating. Expanding and heat-sealing the expanded beads under pressure in the second step is advantageous in that there are no slit marks on the surface of the foamed molded article, the maximum peak height (Sp) on the surface is reduced, and the fusion rate inside the foamed molded article is increased.

[0056] In the steam heating method, a heating medium such as steam is introduced into the molding space to directly heat the expanded beads, so that the expanded beads inside the molding space can be sufficiently heated, resulting in a high internal fusion rate of the expanded bead molded body. On the other hand, in the heat press method, the heat from the heated mold can generally sufficiently heat the expanded beads in contact with the mold, but the heat transfer to the expanded beads inside the molding space is relatively small, which is disadvantageous for heating the expanded beads inside the molding space. However, surprisingly, the internal fusion rate of the expanded bead molded body obtained by the manufacturing method of the present invention using expanded aromatic polyester resin beads was 60% or more, which was a high value for an expanded bead molded body manufactured by the heat press method (Examples 1 to 4).

[0057] (Composite structural member) The composite structural member of the present invention comprises a foam molded article as a core material. For example, the composite structural member of the present invention is formed by laminating a skin material onto the surface of the foam molded article of the present invention.

[0058] In composite structural members, a skin material is primarily used to protect the surface of the foam molded body and to obtain superior properties that cannot be obtained with the foam molded body alone. For example, the use of a skin material can further improve heat resistance and mechanical strength. The skin material may be laminated over the entire surface of the foam molded body, or over only a portion of the surface.

[0059] Examples of the skin material include fiber reinforced materials, metal sheets, resin films, etc. Among these, fiber reinforced materials are preferred.

[0060] The fibers constituting the fiber reinforcement are not particularly limited, and examples thereof include carbon fiber, glass fiber, aramid fiber, boron fiber, and metal fiber. Carbon fiber, glass fiber, and aramid fiber are preferred because of their excellent heat resistance and mechanical strength, and carbon fiber is more preferred. The fiber reinforcement may be impregnated with a thermosetting resin or a thermoplastic resin. In other words, the skin material may be a prepreg.

[0061] The thermosetting resin is not particularly limited, and examples thereof include epoxy resin, unsaturated polyester resin, phenol resin, melamine resin, polyurethane resin, silicone resin, maleimide resin, vinyl ester resin, cyanate ester resin, and resin obtained by prepolymerizing maleimide resin and cyanate ester resin. Epoxy resin or vinyl ester resin is preferred because of its excellent heat resistance, elastic modulus, and chemical resistance. Only one type of thermosetting resin may be used, or two or more types may be used in combination.

[0062] The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resins, polyester resins, thermoplastic epoxy resins, polyamide resins, thermoplastic polyurethane resins, sulfide resins, and acrylic resins. Polyester resins and thermoplastic epoxy resins are preferred because they have excellent adhesion between the skin material and the foam molded body or between the fibers constituting the fiber reinforcement. Only one type of thermoplastic resin may be used, or two or more types may be used in combination.

[0063] The metal sheet is not particularly limited, and examples thereof include aluminum sheet, stainless steel sheet, iron sheet, steel sheet, titanium sheet, etc. Aluminum sheet is preferred because it is both lightweight and has excellent mechanical strength. Note that aluminum sheet also includes aluminum alloy sheet containing 50% by mass or more of aluminum.

[0064] The resin film is not particularly limited, and examples thereof include polyolefin-based resin films, polyester-based resin films, acrylic-based resin films, etc. Examples of the polyolefin-based resin films include polyethylene-based resin films, polypropylene-based resin films, etc. Examples of the polyester-based resin films include polyethylene terephthalate films.

[0065] The skin material is preferably laminated and integrated with the foam molded article. The method for laminating and integrating a skin material onto the surface of a foam molded article is not particularly limited, and examples thereof include: (1) a method of laminating and integrating a skin material onto the surface of a foam molded article using an adhesive; (2) a method of laminating a skin material (preferably a fiber-reinforced material) impregnated with a thermoplastic resin onto the surface of a foam molded article, and integrating the skin material onto the surface of the foam molded article using the thermoplastic resin impregnated in the skin material as a binder; (3) a method of laminating a skin material (preferably a fiber-reinforced material) impregnated with an uncured thermosetting resin onto the surface of a foam molded article, and integrating the skin material onto the surface of the foam molded article by curing the thermosetting resin using the thermosetting resin impregnated in the skin material as a binder; (4) a method of disposing a heated and softened skin material on the surface of a foam molded article, and pressing the skin material against the surface of the foam molded article to deform the skin material along the surface of the foam molded article as necessary, and integrating the skin material onto the surface of the foam molded article; and (5) other methods generally used in molding fiber-reinforced resin sheets. Examples of such methods include autoclave, hand lay-up, spray-up, PCM (Prepreg Compression Molding), RTM (Resin Transfer Molding), VaRTM (Vacuum assisted Resin Transfer Molding), etc. The autoclave, RTM, and VaRTM methods are preferred because they improve the adhesion between the skin material and the foam molded article or between the fibers constituting the fiber reinforcement.

[0066] In addition to the inherent lightweight, soundproofing, thermal insulation, and vibration-damping properties of foamed molded articles, composite structural members incorporate various additional functions (heat resistance, abrasion resistance, abrasion resistance, beautiful appearance, chemical resistance, water resistance, oil resistance, stain resistance, etc.) through integration with skin materials. Therefore, in addition to the applications traditionally associated with aromatic polyester resin foamed molded articles, composite structural members can be used in a variety of fields, including construction, transportation equipment (automobiles, motorcycles, buses, trains, aircraft, ships, etc.), space, energy technology (e.g., wind turbine rotors), sports (various exercise equipment, etc.), the electrical industry, and the electronics industry. Examples of such composite structural members include aircraft equipment structures (e.g., helicopter blades), interior and exterior materials for various vehicles, materials for sporting goods, materials for leisure goods, sandwich structural materials, and wind power generation blades. Examples of automotive components include door panels, door liner parts, bumpers, fenders, fender supports, engine covers, roof panels, trunk lids, floor panels, instrument panels, center clusters, center tunnels, and crash boxes. For example, by using composite structural members for door panels that have traditionally been made of steel plate, door panels that have roughly the same rigidity as steel plate door panels can be significantly lighter and have improved thermal insulation and soundproofing properties.

[0067] Hereinafter, one embodiment of the present invention will be described in more detail using examples, etc., but the present invention is not limited to these. The methods for determining various physical properties in the examples, etc. are described below. The surface of the foamed molded article measured in the examples, etc. is the upper surface of the foamed molded article (the surface that is in contact with the male mold during production). Therefore, the surface properties of the foamed molded article measured in the examples, etc. are the properties of the upper surface of the foamed molded article.

[0068] (Average particle size of expanded beads) The average particle size of expanded beads was measured by the following method. First, several types of sieves with different mesh sizes specified in JIS (mesh size 6.70 mm, mesh size 5.60 mm, mesh size 4.75 mm, mesh size 4.00 mm, mesh size 3.35 mm, mesh size 2.80 mm, mesh size 2.36 mm, mesh size 2.00 mm, mesh size 1.70 mm, mesh size 1.40 mm, mesh size 1.18 mm, mesh size 1.00 mm, mesh size 0.850 mm, mesh size 0.710 mm, mesh size 0.600 mm, mesh size 0.500 mm) were prepared, and 50 g of expanded beads were sieved through the sieves in the order of large to small mesh sizes. Then, the expanded beads were unable to pass through the sieves with mesh sizes of a predetermined size depending on the particle size of each particle, and remained on each sieve. The average particle size of the expanded beads remaining on each sieve was determined based on the size of the sieve openings, as shown in the following table. For example, the particle size of the expanded beads remaining on a sieve with an opening size of 1.70 mm was determined to be 1.85 mm.

[0069]

[0070] (Bulk density of expanded particles) Approximately 1000 cm ３ The expanded particles were placed in a measuring cylinder to give a volume of 1000 cm ３ The graduated cylinder was visually inspected from the horizontal direction, and if even one foam particle was found within 1000 cm ３ When the weight reached the mark, the filling of the expanded beads into the measuring cylinder was completed. Next, the mass of the expanded beads filled into the measuring cylinder was weighed to two decimal places, and this mass was designated as W (g). The bulk density of the expanded beads was then calculated using the following formula: Bulk density (g / L) = W

[0071] (Apparent volume of expanded particles) 1000 cm ３ A measuring cylinder capable of measuring 1 L was prepared, and the expanded beads were filled into the measuring cylinder. The measuring cylinder was visually observed from the horizontal direction, and the mark reached by at least one expanded bead was regarded as the apparent volume (cm) of the expanded beads. ３ )

[0072] (Density of foam molded article) The mass (a) and volume (b) of a foam molded article (which was dried at 25°C for 20 hours or more after molding) were measured to have three or more significant figures, and the density (g / L) of the foam molded article was calculated using the formula (a) / (b).

[0073] (Internal fusion rate of foamed molded article) A cut line of about 2 mm depth was made on the top surface of the foamed molded article with a cutter knife, and the foamed molded article was divided into two along the cut line to expose the fracture surface. An arbitrary area containing 150 foamed beads was determined on the fracture surface, and the 150 foamed beads within that area were observed. The number of foamed beads broken within the foamed beads (a) and the number of foamed beads broken at the interface between the foamed beads (b) were counted, and the values ​​obtained by substituting these values ​​into the formula [(a) / ((a)+(b))]×100 were used to determine the fusion rate (%). The foamed molded article used as a sample for measuring the fusion rate was basically flat, approximately 10 mm thick, approximately 200 mm wide, and approximately 200 mm long, and the cut line was formed so as to cross the center of the foamed molded article in the longitudinal direction toward the width direction. If the number of expanded beads observed on the fracture surface is less than 150, all of the expanded beads on the fracture surface are observed, and the number of expanded beads that have broken within the expanded beads (a) and the number of expanded beads that have broken at the interface between the expanded beads (b) are counted, and these results are substituted into the above formula to calculate the fusion rate.

[0074] (Maximum peak height (Sp) on the surface of a foam molded article) The maximum peak height (Sp) on the surface of a foam molded article was measured using a measuring device (Keyence VR-3200) conforming to ISO 25178. Details of the measurement method are described below. [Sample] The surface of the foam molded article to be measured was cut into a size of 5 cm x 6 cm and attached to a flat metal plate with double-sided tape. The surface to be measured was the surface with the largest area and the surface that came into contact with the male mold during foam molding, and was the surface targeted for measuring the maximum peak height (Sp) described above. [Measurement conditions] Magnification: 12x Measurement conditions: Expert Measurement mode: Super fine Measurement direction: Both sides Measurement brightness adjustment: Auto (80) Missing point / saturation point display: ON [Analysis] The following analysis was performed using the captured images. Analysis was performed using Keyence's analysis application. [Analysis conditions] Image processing: After surface correction was performed over the entire area Filter settings: No cutoff End effect correction: Unchecked Surface roughness analysis was performed over the entire area to determine the maximum peak height (Sp). Measurements were taken three times, and the average value was calculated.

[0075] (DSC Measurement) A sample was prepared by thinly slicing a foamed molded article within a thickness of 2 mm from the surface using a utility knife. The sample (5.5±0.5 mg) was packed tightly at the bottom of an aluminum measurement container, and then covered with an aluminum lid. Differential scanning calorimetry was then performed using a Hitachi High-Tech Science DSC7000X, AS-3 differential scanning calorimeter. The sample was heated at a nitrogen gas flow rate of 20 mL / min in the following steps to obtain a DSC curve. Alumina was used as the reference material. (Step 1) The sample was held at 30°C for 2 minutes. (Step 2) The temperature was increased from 30°C to 290°C at a rate of 10°C / min.

[0076] (Crystallization temperature, melting temperature) The crystallization temperature and melting temperature of the surface of the foamed molded article were determined from the DSC curve obtained in the DSC measurement. Using analysis software attached to the differential scanning calorimeter, the top temperatures of the crystallization peak and melting peak observed during the temperature rise process were read from the DSC curve and defined as the crystallization temperature and melting temperature (melting point), respectively.

[0077] (Crystallization degree) The crystallinity was measured by the method described in JIS K7122:1987 and JIS K7122:2012. From the DSC curve obtained in the DSC measurement, the area of ​​the melting peak, the heat of fusion C1 (J / g) calculated from the area of ​​the melting peak, and the area of ​​the crystallization peak, the heat of crystallization C2 (J / g) calculated from this area, were identified using analysis software attached to the differential scanning calorimeter. The heat of crystallization was subtracted from the heat of fusion to determine the difference. The crystallinity was determined by dividing this difference by 140.1 J / g, which is the theoretical heat of fusion of fully crystalline polyethylene terephthalate. Specifically, the heat of fusion was calculated from the area enclosed by the DSC curve and the straight line connecting the point where the DSC curve departs from the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline. The heat of crystallization was calculated from the area enclosed by the line connecting the point where the DSC curve departs from the low-temperature baseline and the point where the DSC curve returns to the high-temperature side, and the DSC curve. In other words, the crystallinity was calculated using the following formula: Crystallinity (%) = ((C1 - C2) / 140.1) x 100

[0078] (Thermal History Peak Temperature) The thermal history peak temperature was determined from the DSC curve obtained in the DSC measurement. Using analysis software attached to the differential scanning calorimeter, the temperature at the apex of the endothermic peak located below the melting temperature was determined, and this was taken as the thermal history peak temperature.

[0079] Example 1 (1) Production of Expanded Beads Expanded beads were produced using the production apparatus shown in FIGS. 5 to 7 according to the following procedure.

[0080] Plant-derived polyethylene terephthalate (intrinsic viscosity: 0.80, density: 1400 kg / m ３ 95% by mass of polyethylene naphthalate (intrinsic viscosity: 0.50, density: 1330 kg / m, melting point: 247.2°C, glass transition temperature: 78.7°C, mass average molecular weight: 74,000, plant content: 30%) ３An aromatic polyester resin composition was obtained by blending 100 parts by mass of an aromatic polyester resin material containing 5% by mass of polyethylene terephthalate (polyethylene terephthalate content: 60% by mass, talc content: 40% by mass, intrinsic viscosity of polyethylene terephthalate: 0.82), 1.8 parts by mass of a masterbatch obtained by incorporating talc into polyethylene terephthalate (polyethylene terephthalate content: 60% by mass, talc content: 40% by mass, intrinsic viscosity of polyethylene terephthalate: 0.82), and 0.25 parts by mass of pyromellitic anhydride.

[0081] The resulting aromatic polyester resin composition was fed to a single-screw extruder having a bore diameter of 65 mm and an L / D ratio of 35, and melt-kneaded at 290° C. The kneading time was 15 minutes.

[0082] Next, butane (containing 35% by mass of isobutane and 65% by mass of normal butane) as a foaming agent was introduced into the extruder, and the foaming agent was pressurized into the molten aromatic polyester resin composition, thereby uniformly dispersing the foaming agent in the aromatic polyester resin composition. At this time, the amount of butane added was 1.2 parts by mass per 100 parts by mass of the aromatic polyester resin material.

[0083] Thereafter, the molten aromatic polyester resin composition was cooled to 270°C at the front end of the extruder, and then extrusion foamed from each nozzle of the multi-nozzle mold 1 attached to the front end of the extruder. The extrusion rate of the aromatic polyester resin composition was set to 38 kg / hour.

[0084] The multi-nozzle mold 1 had 50 nozzles, each with an outlet 11 diameter of 0.8 mm, and all of the nozzle outlets 11 were arranged at equal intervals on an imaginary circle A with a diameter of 139.5 mm, which was assumed to be on the front end surface 1a of the multi-nozzle mold 1.

[0085] Two rotary blades 5 were integrally provided on the outer peripheral surface of the rear end of the rotary shaft 2, with a phase difference of 180° in the circumferential direction of the rotary shaft 2. Each rotary blade 5 was configured to move on an imaginary circle A while constantly contacting the front end surface 1a of the multi-nozzle mold 1. The rotary shaft 2 passed through the front part 41a of a cooling drum 41 constituting the cooling member 4, and was connected to a driving member 3 which was a motor.

[0086] The cooling member 4 included a cooling drum 41. The cooling drum 41 had a front portion 41a that was circular at the front and a cylindrical peripheral wall portion 41b that extended rearward from the outer periphery of the front portion 41a and had an inner diameter of 320 mm. Cooling water 42 at 30°C was supplied into the cooling drum 41 through a supply pipe 41d and a supply port 41c of the cooling drum 41. The internal volume of the cooling drum 41 was 17,684 cm ３ It was.

[0087] The cooling water 42 flows forward in a spiral along the inner circumferential surface of the circumferential wall 41b of the cooling drum 41 due to centrifugal force generated by the flow rate when the cooling water 42 is supplied from the supply pipe 41d to the inner circumferential surface of the circumferential wall 41b of the cooling drum 41. As the cooling water 42 flows along the inner circumferential surface of the circumferential wall 41b, the cooling water 42 gradually spreads in a direction perpendicular to the direction of its movement. As a result, the inner circumferential surface of the circumferential wall 41b forward of the supply port 41c of the cooling drum 41 is entirely covered with the cooling water 42. In FIG. 7, the cooling water 42 flows in the direction indicated by the arrow X.

[0088] The rotary blade 5 disposed on the front end surface 1a of the multi-nozzle mold 1 was rotated at a rotation speed of 2500 rpm, and the extrudate (extruded foam) of the aromatic polyester resin extruded and foamed from the outlet portion 11 of each nozzle of the multi-nozzle mold 1 was cut by the rotary blade 5 to produce approximately spherical granular cut products.

[0089] The extrudate of the aromatic polyester resin consisted of an unfoamed portion immediately after being extruded from the nozzle of the multi-nozzle mold 1 and a foamed portion in the process of foaming that was continuous with the unfoamed portion. The extrudate of the aromatic polyester resin was cut at the open end of the outlet 11 of the nozzle, and the cutting of the extrudate of the aromatic polyester resin took place in the unfoamed portion.

[0090] When producing the expanded beads, first, the rotating shaft 2 was not attached to the multi-nozzle mold 1, and the cooling member 4 was retracted from the multi-nozzle mold 1. In this state, an extrudate of an aromatic polyester resin was extruded and foamed from the extruder, and it was confirmed that the extrudate of the aromatic polyester resin consisted of an unfoamed portion immediately after being extruded from the nozzle of the multi-nozzle mold 1 and an expanded portion in the process of expanding that was continuous with the unfoamed portion. After this confirmation, the rotating shaft 2 was attached to the multi-nozzle mold 1, the cooling member 4 was disposed in a predetermined position, and then the rotating shaft 2 was rotated, and the extrudate of the aromatic polyester resin was cut with the rotary blade 5 at the open end of the nozzle outlet 11 to produce granular cut pieces.

[0091] The resulting particulate cut material was thrown outward or forward by the cutting stress of the rotary blade 5. The thrown particulate cut material collided obliquely with the surface of the cooling water 42 flowing along the inner surface of the cooling drum 41 of the cooling member 4, from the upstream side to the downstream side of the flow of the cooling water 42, so as to follow the cooling water 42, and the particulate cut material entered the cooling water 42 and was immediately cooled.

[0092] The particulate cut material was discharged together with cooling water 42 through the discharge port 41 e of the cooling drum 41, and then separated from the cooling water 42 in a dehydrator. In this manner, expanded beads (expanded aromatic polyester resin beads) were produced.

[0093] (2) Preparation of foam molded article A foam molded article was prepared according to the following procedure.

[0094] A straight plate-shaped molding space measuring 200 mm in length, 200 mm in width, and 10 mm in depth (volume Vmin: 400 cm ３Foam molding was performed using a heating and compressing machine having a mold (Figs. 3 and 4) with a vent hole (height 1 mm, length 100 mm) in its side wall. One vent hole was provided on each side wall, allowing gas in the molding space to be exhausted to the outside of the mold. The mold was heated to a set temperature of 120°C, and 60 g of expanded beads (average particle diameter 2.5 mm; bulk density 150 g / L) was filled into the mold. The mold was closed using a hydraulic compression mechanism and heated for 15 minutes. Immediately after heating, cooling was performed for 5 minutes to bring the mold temperature to 60°C or below. After cooling, the bead foam molded article was removed from the mold. The apparent volume of 60 g of expanded beads (volume including the space between the beads) was approximately 429 cm. ３ For this reason, molding was carried out by applying pressure in the opening and closing directions of the mold at a compression rate of approximately 7%.

[0095] Examples 2 to 4 and Comparative Examples 1 and 2 Foam molded articles were obtained in the same manner as in Example 1, except that the heating temperature of the mold in the foam molded article preparation step was changed to the temperatures shown in Table 1.

[0096] Comparative Example 3 A foam molded article was produced in the same manner as in Example 1, except that in the foam mold production step, the heating temperature of the mold was changed to the temperature shown in Table 1. However, the molded article shrunk significantly, and it was not possible to obtain a foam molded article having a shape corresponding to the shape of the mold.

[0097] Comparative Example 4 A foamed molded article was obtained in the same manner as in Example 1, except that in the foamed molded article preparation step, the foamed molded article was obtained by the steam heating method described below.

[0098] (2) Preparation of foam molded article A foam molded article was prepared according to the following procedure.

[0099] An in-mold foam molding machine was prepared, which was equipped with a mold including a male mold and a female mold. When the male mold and the female mold were clamped together, a molding space having a rectangular parallelepiped shape with interior dimensions of 200 mm length x 200 mm width x 10 mm height was formed between the male and female molds.

[0100] The mold had a total of 252 circular supply ports, each 8 mm in diameter, spaced 20 mm apart to supply steam for heating from outside the mold through the mold to the expanded beads in the molding space. Each supply port had a lattice (slit; lattice width 1 mm) on its entire surface to prevent the expanded beads filled in the mold from leaking out of the mold through the supply port. The mold was also configured to allow steam to be smoothly supplied from outside the mold into the molding space through the supply ports.

[0101] The foamed beads were filled into the molding space of the mold in the same manner as in Example 1. Steam at 120°C was supplied into the molding space to heat and expand the foamed beads, and the secondary foamed beads were integrated by thermal fusion. Next, cooling water was supplied into the molding space to cool the foamed molded body in the molding space, and the mold was then opened to remove the foamed molded body.

[0102] Comparative Example 5 A foam molded article was obtained in the same manner as in Example 1, except that a mold without vent holes was used in the foam molded article preparation step. The mold used here was the same as the mold used in Example 1, except that it did not have vent holes.

[0103] The foamed molded articles obtained in the examples and comparative examples were subjected to various tests. Table 2 shows the outline of the examples and comparative examples and the test results.

[0104]

[0105] The fusion rates within the foam molded articles were 60% or higher for the foam molded articles of Examples 1 to 4, which were higher than those of the foam molded articles of Comparative Examples 1, 2, and 5. The maximum peak height (Sp) of the foam molded articles on the surface was smaller for the foam molded articles of Examples 1 to 4 than for the foam molded articles of Comparative Examples 1, 4, and 5. No slit marks were observed in the foam molded articles of Examples 1 to 4, while slit marks were observed on the entire surface of the foam molded article of Comparative Example 4. The foam molded articles of Examples 1 to 4 had a surface crystallinity within the range of 20 to 30% and a thermal history peak temperature within the range of 125 to 200°C, while the foam molded articles of Comparative Examples 1, 2, 4, and 5 had either or both of the surface crystallinity and the thermal history peak temperature outside these ranges. The foam molded articles had a surface crystallinity within the range of 20 to 30% and a thermal history peak temperature within the range of 125 to 200°C, resulting in a high internal fusion rate and a small Sp.

[0106] E1: long side, E2: short side, F1: region from the long side to a length equivalent to 10% of the average length of the long side and the short side (the sum of the long side length and the short side length divided by 2), F2: region from the short side to a length equivalent to 10% of the average length of the long side and the short side, F3: region excluding the region corresponding to the end of the plan view, f1: region corresponding to the plan view region F1, f2: region corresponding to the plan view region F2, f3: surface of the foam molded article corresponding to the plan view region F3 1: multi-nozzle mold, 1a: front end surface, 2: rotating shaft, 3: driving member, 4: cooling member, 5: rotating blade, 11: outlet portion, 41: cooling drum, 41a: front portion, 41b: peripheral wall portion, 41c: supply port, 41d: supply pipe, 41e: discharge port, 42: cooling water 60': Expanded beads (expanded beads before fusion; pre-expanded beads), 60: Expanded beads (after fusion), 100: Bead expansion molded body, D1: Thickness direction (opening and closing direction of the molding die), M: Molding die, Ma: Female die, Mb: Male die, Mv: Molding space

Claims

1. An aromatic polyester resin foam molded product for use as a core material for composite structural members, the foam molded product containing 90% by mass or more of polyethylene terephthalate, the foam molded product having a surface crystallinity of 20-30% and a thermal history peak temperature of 125-200°C, as measured by a differential scanning calorimeter (DSC), the maximum peak height (Sp) of the surface of the foam molded product being 0.25 mm or less, and the fusion rate of the foamed particles constituting the foam molded product being 60% or more.

2. A composite structural member comprising the foamed molded article according to claim 1 as a core material.

3. A method for producing an aromatic polyester resin foamed molded product using a mold having a molding space for molding the foamed molded product, the mold having a pair of mold members arranged to face each other, and configured such that the molding space can be opened and closed and the volume of the molding space can be changed by moving the pair of mold members toward and away from each other, the method comprising: a first step of placing foamed particles of the aromatic polyester resin in the molding space of the mold and closing the mold, and a second step of forming the foamed molded product by heating the mold after the first step, thereby foaming and heat-sealing the foamed particles contained in the molding space, the mold having a vent hole on the side that leads to the molding space, and during heating in the second step, gas in the molding space can be discharged to the outside of the mold through the vent hole in the mold, the foamed molded product contains 90% by mass or more of polyethylene terephthalate, the foamed molded product has a surface crystallinity of 20-30% and a thermal history peak temperature of 125-200°C, as measured by a differential scanning calorimeter (DSC); the foamed molded product has a maximum peak height (Sp) of 0.25 mm or less on the surface; and the foamed particles constituting the foamed molded product have a fusion rate of 60% or more.

4. A method for producing a foamed molded article as described in claim 3, wherein in the first step, the foamed beads are pressurized by closing the molding die, and in the second step, the pressurized foamed beads are foamed and heat-sealed.

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