Foamed thermoplastic resin particles, molded body of foamed thermoplastic resin particles, foamed resin composite, method for producing foamed thermoplastic resin particles, and method for producing molded body of foamed thermoplastic resin particles

Abstract

This foamed thermoplastic resin particle comprises a thermoplastic resin, the thermoplastic resin including a polyester-based resin, a polyimide-based resin, and a phosphorus-based flame-retardant, wherein the content of the polyimide-based resin is 5-45% by mass based on the total mass of the thermoplastic resin, and the content of phosphorus is 0.15-1.00% by mass based on the total mass of the thermoplastic resin. The content of the polyimide-based resin is preferably 25-45% by mass.

Description

Expanded thermoplastic resin beads, expanded thermoplastic resin beads molded body, expanded resin composite, method for producing expanded thermoplastic resin beads, and method for producing expanded thermoplastic resin beads molded body

[0001] The present invention relates to a thermoplastic resin foamed bead, a thermoplastic resin foamed bead molded article, a foamed resin composite, a method for producing a thermoplastic resin foamed bead, and a method for producing a thermoplastic resin foamed bead molded article. This application claims priority from Japanese Patent Application No. 2022-094483, filed on June 10, 2022, the contents of which are incorporated herein by reference.

[0002] Molded articles (expanded thermoplastic resin bead molded articles) made from expanded beads containing a thermoplastic resin (expanded thermoplastic resin beads) are lightweight and have excellent heat insulation, shock absorption, and mechanical strength. For this reason, the application of expanded thermoplastic resin bead molded articles (sometimes simply referred to as "expanded bead molded articles") to automobiles, aircraft, railway vehicles, etc. Among thermoplastic resins, polyester-based resins such as polyethylene terephthalate (PET) can be used to produce expanded bead molded articles with excellent rigidity and heat resistance, and therefore, expansion bead molded articles using polyester-based resins are being studied.

[0003] One method for producing an expanded bead molding is in-mold foam molding. The following describes in-mold foam molding. Expanded thermoplastic resin beads (sometimes simply referred to as "expanded beads") are filled into a mold cavity. The expanded beads in the cavity are heated with a heating medium such as hot water or steam to expand and become secondary expanded beads. The expansion pressure of the expanded beads causes the secondary expanded beads to be thermally fused together and integrated, yielding an expanded bead molding of the desired shape.

[0004] The glass transition temperature (Tg) of polyester resins is lower than that of polystyrene resins. Therefore, expanded thermoplastic resin beads and expanded thermoplastic resin beads have low heat resistance. To improve heat resistance, expanded thermoplastic resin beads and expanded thermoplastic resin beads containing polyester resins and polyimide resins and having a single glass transition temperature (Tg) have been proposed (Patent Document 1).

[0005] In addition, in certain applications, expanded bead moldings are required to have flame retardancy. For example, Patent Document 2 proposes a thermoplastic resin expanded bead molding containing a polyphenylene ether resin, which is an amorphous resin, and a flame retardant. Also, Patent Document 3 proposes a polyester resin foam containing a polyester resin, which is a crystalline resin, and a bromine-based flame retardant. Alternatively, for example, Patent Document 4 proposes a flame-retardant polyester resin foam containing a polyester resin and a polyarylate resin.

[0006] JP 2022-57468 A International Publication No. 2011 / 019057 JP 2006-249158 A JP 2000-63553 A

[0007] However, the invention of Patent Document 1 improves heat resistance but does not consider flame retardancy. In addition, increasing the amount of polyimide resin to further improve heat resistance requires a specialized molding machine capable of in-mold foam molding at increased steam pressure. Therefore, using a general-purpose molding machine, it is difficult to mold the foamed bead molding into the desired shape (poor moldability). The invention of Patent Document 2 imparts flame retardancy, but because it contains an amorphous resin, it is prone to elongation or shrinkage when heated, etc. That is, the invention of Patent Document 2 has low dimensional stability under heat and poor heat resistance. The invention of Patent Document 3 uses a bromine-based flame retardant to improve flame retardancy, but requires greater environmental consideration. The invention of Patent Document 4 relates to a foam sheet and does not consider its application to expanded thermoplastic resin beads and their moldings.

[0008] Therefore, an object of the present invention is to provide expanded thermoplastic resin beads that are excellent in flame retardancy and heat resistance, and also in moldability for forming expanded bead moldings.

[0009] In general, unfoamed resins containing flame retardants exhibit excellent flame retardancy. However, foamed resins containing flame retardants have significantly lower flame retardancy than unfoamed resins containing flame retardants. Foamed resins also contain less resin per unit volume than unfoamed resins, which allows for resource conservation. However, because foamed resins contain less resin per unit volume, they are less likely to form a char layer upon combustion, resulting in a longer burning time. This is thought to result in a lower flame retardancy of foamed resins. Additionally, foamed resins contain less resin per unit volume than unfoamed resins, making them more susceptible to softening due to combustion heat and more likely to cause resin dripping during combustion. Furthermore, foamed resins containing crystalline resins experience a rapid decrease in viscosity when melted during combustion. This makes foamed resins more susceptible to resin dripping during combustion. Increasing the content of flame retardants in foamed resins to improve flame retardancy improves flame retardancy, but at the expense of reduced mechanical properties. In addition, because flame retardants have the effect of plasticizing resins, increasing the content of flame retardants leads to adverse effects such as a decrease in the heat resistance of the foamed resin and an inhibition of foamability due to a decrease in extensional viscosity. Furthermore, as disclosed in Patent Document 4, increasing the content of super engineering plastics such as polyarylate resins reduces the foamability of the thermoplastic resin foam beads and the foam moldability. Thus, simply blending a flame retardant into a foamed resin does not provide the desired physical properties. After extensive research, the present inventors discovered that by setting the content of the polyimide resin and the content of the phosphorus-based flame retardant within specific ranges, it is possible to improve flame retardancy, heat resistance, and moldability, and thus completed the present invention.

[0010] That is, the present invention has the following aspects. <1> Expanded thermoplastic resin beads comprising a thermoplastic resin, wherein the thermoplastic resin comprises a polyester resin, a polyimide resin, and a phosphorus-based flame retardant, wherein the content of the polyimide resin is 5 to 45 mass% relative to the total mass of the thermoplastic resin, and the content of phosphorus is 0.15 to 1.00 mass% relative to the total mass of the thermoplastic resin. <2> Expanded thermoplastic resin beads according to <1>, wherein the content of the polyimide resin is 25 to 45 mass% relative to the total mass of the thermoplastic resin. <3> Expanded thermoplastic resin beads according to <1> or <2>, wherein the glass transition temperature Tg is 80 to 130°C.

[0011] <4> A foamed thermoplastic resin bead molding comprising two or more foamed thermoplastic resin beads thermally fused together, the foamed thermoplastic resin comprising a thermoplastic resin, a polyester resin, a polyimide resin, and a phosphorus-based flame retardant, the polyimide resin content being 5 to 45 mass% relative to the total mass of the thermoplastic resin, and the phosphorus content being 0.15 to 1.00 mass% relative to the total mass of the thermoplastic resin. <5> The foamed thermoplastic resin bead molding according to <4>, having a flame retardancy of V-0, V-1, or V-2 as measured in accordance with the UL-94 vertical method (11 mm vertical flame test) of the UL standard. <6> The foamed thermoplastic resin bead molding according to <4>, having a polyimide resin content of 25 to 45 mass% relative to the total mass of the thermoplastic resin. <7> The foamed thermoplastic resin bead molding according to <6>, having a flame retardancy of V-0 or V-1 as measured in accordance with the UL-94 vertical method (11 mm vertical flame test) of the UL standard. <8> The expanded thermoplastic resin bead molded article according to any one of <4> to <7>, having a glass transition temperature Tg of 80 to 130° C. <8-1> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8>, wherein the polyester-based resin is at least one selected from the group consisting of polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polyethylene naphthalate resin (PEN), polyethylene furanoate resin (PEF), polybutylene naphthalate resin (PBN), polytrimethylene terephthalate resin (PTT), a copolymer of terephthalic acid, ethylene glycol, and cyclohexanedimethanol, and mixtures thereof. <8-2> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8>, wherein the polyester-based resin is polyethylene terephthalate resin. <8-3> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molding according to any one of <1> to <8>, wherein the polyester-based resin is a crystalline polyethylene terephthalate resin (C-PET).<8-3> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8>, wherein the polyester-based resin is at least one selected from the group consisting of petrochemical-derived polyester-based resins and plant-derived polyester-based resins (for example, polyethylene terephthalate resin, plant-derived polyethylene furanoate resin, and plant-derived polytrimethylene terephthalate resin). <8-4> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8-3>, wherein the polyimide-based resin is a compound represented by the following formula (3):

[0012] [In formula (3), R represents an aromatic group having 6 to 42 carbon atoms, and R' represents at least one divalent organic group selected from the group consisting of a divalent aromatic group having 6 to 30 carbon atoms, an aliphatic group having 2 to 30 carbon atoms, and an alicyclic group having 4 to 30 carbon atoms. p represents the number of repeating units.]

[0013] <8-5> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8-4>, wherein the content of the polyimide resin is 25 to 40 mass% relative to the total mass of the thermoplastic resin. <8-6> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8-5>, wherein the phosphorus-based flame retardant is at least one selected from the group consisting of phosphate compounds, polyphosphoric acid compounds, red phosphorus, organic phosphate ester compounds, phosphazene compounds, phosphonic acid compounds, phosphinic acid compounds, phosphine oxide compounds, phosphorane compounds, and phosphoramide compounds. <8-7> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to <8-6>, wherein the phosphate compound is at least one selected from the group consisting of melamine phosphate, guanidine phosphate, ammonium phosphate, amide ammonium phosphate, and carbamate phosphate, and the polyphosphoric acid compound is at least one selected from the group consisting of melamine polyphosphate, guanidine polyphosphate, ammonium polyphosphate, amide ammonium polyphosphate, and carbamate polyphosphate. <8-8> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8-7>, wherein the phosphorus content is 0.25 to 0.80 mass% relative to the total mass of the thermoplastic resin.

[0014] <8-9> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8-8>, wherein the content of the polyimide resin is 30 to 40% by mass, relative to the total mass of the thermoplastic resin, the content of the phosphorus is 0.30 to 0.66% by mass, relative to the total mass of the thermoplastic resin, and the expanded thermoplastic resin beads have a crystallinity of 3.3 to 6.3% and a glass transition temperature Tg of 91.2 to 94.5° C. <8-10> The expanded thermoplastic resin beads or the expanded thermoplastic resin bead molded article according to any one of <1> to <8-9>, wherein the expanded thermoplastic resin beads have an open cell ratio of 3.4 to 16%.

[0015] <9> An expanded resin composite having the thermoplastic resin foamed bead molding according to any one of <4> to <8-10> and a fiber-reinforced resin layer provided on at least a part of the surface of the expanded thermoplastic resin foamed bead molding.

[0016] <10> A method for producing expanded thermoplastic resin beads, comprising a step of extruding and foaming a thermoplastic resin composition containing a thermoplastic resin and a blowing agent to obtain expanded thermoplastic resin beads, wherein the thermoplastic resin contains a polyester resin, a polyimide resin, and a phosphorus-based flame retardant, the content of the polyimide resin being 5 to 45 mass% relative to the total mass of the thermoplastic resin, and the content of phosphorus being 0.15 to 1.00 mass% relative to the total mass of the thermoplastic resin. <11> The method for producing expanded thermoplastic resin beads according to <10>, wherein the content of the polyimide resin is 25 to 45 mass% relative to the total mass of the thermoplastic resin.

[0017] <12> A method for producing an expanded thermoplastic resin bead molded article, comprising obtaining the expanded thermoplastic resin beads by the method for producing expanded thermoplastic resin beads according to <10> or <11>, filling the obtained expanded thermoplastic resin beads into a cavity of a mold, heating the expanded thermoplastic resin beads in the cavity to form secondary expanded beads, and heat-fusing the secondary expanded beads to each other to obtain an expanded thermoplastic resin bead molded article. <13> A battery case or a battery case comprising the expanded thermoplastic resin bead molded article according to any one of <4> to <8-10>.

[0018] The expanded thermoplastic resin beads of the present invention can improve the flame retardancy and heat resistance of the expanded bead molded article, as well as the moldability.

[0019] Fig. 1 is a flow diagram showing an example of a manufacturing process for a plant-derived polyester-based resin. Fig. 2 is a flow diagram showing an example of a manufacturing process for a plant-derived polyester-based resin. Fig. 3 is a flow diagram showing an example of a manufacturing process for a plant-derived polyester-based resin. Fig. 4 is a side cross-sectional schematic diagram showing an example of a manufacturing apparatus for expanded thermoplastic resin beads of the present invention. Fig. 5 is a front schematic diagram showing an example of a manufacturing apparatus for expanded thermoplastic resin beads of the present invention. Fig. 6 is a cross-sectional view of an expanded resin composite according to one embodiment of the present invention.

[0020] In this document, "~" indicates a range that includes both the upper and lower limits.

[0021] (Expanded Thermoplastic Resin Beads) The expanded thermoplastic resin beads (expanded beads) of the present invention contain a thermoplastic resin. The expanded beads are particles obtained by granulating and expanding a thermoplastic resin composition (hereinafter sometimes simply referred to as a "resin composition") containing a thermoplastic resin and a blowing agent. The expanded beads are particulate foams. The expanded beads are used as a raw material for a thermoplastic resin expanded bead molding (expanded bead molding) molded by so-called in-mold expansion molding.

[0022] <Thermoplastic Resin> The thermoplastic resin of the expanded beads contains a polyester resin, a polyimide resin, and a phosphorus-based flame retardant. The expanded beads of the present invention contain both a polyester resin and a polyimide resin, thereby improving the heat resistance strength of the expanded bead molding. In addition, the expanded beads of the present invention contain a phosphorus-based flame retardant, thereby imparting flame retardancy to the expanded bead molding.

[0023] <Polyester-Based Resins> Examples of polyester-based resins include polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polyethylene naphthalate resin (PEN), polyethylene furanoate resin (PEF), polybutylene naphthalate resin (PBN), polytrimethylene terephthalate resin (PTT), copolymers of terephthalic acid, ethylene glycol, and cyclohexanedimethanol, and mixtures thereof. Polyethylene terephthalate resin is preferred, and crystalline polyethylene terephthalate resin (C-PET) is more preferred. C-PET is a polyester-based resin in which the acid component is terephthalic acid and the glycol component is ethylene glycol. The polyester-based resin may be a petrochemical-derived polyester-based resin, a plant-derived polyester-based resin such as so-called bioPET, or a mixture thereof. Examples of plant-derived polyester-based resins include polyethylene terephthalate resin, plant-derived polyethylene furanoate resin, and plant-derived polytrimethylene terephthalate resin. Furthermore, the polyester-based resin may be made from recycled raw materials. These polyester resins may be used singly or in combination of two or more.

[0024] Plant-derived polyester resins will be described below. Plant-derived polyester resins are polymers derived from plant materials such as sugarcane and corn. "Derived from plant materials" includes polymers synthesized or extracted from plant materials. For example, "derived from plant materials" includes polymers obtained by polymerizing monomers synthesized or extracted from plant materials. "Monomers synthesized or extracted from plant materials" includes monomers synthesized using compounds synthesized or extracted from plant materials. Plant-derived polyester resins include those in which some of the monomers are "derived from plant materials."

[0025] Plant-derived polyester resins will be explained using PET and PEF as examples.

[0026] The synthesis reaction of PET is shown in formula (1). PET is synthesized by a dehydration reaction between n moles of ethylene glycol and n moles of terephthalic acid (Benzen-1,4-dicarboxylic acid). The stoichiometric mass ratio in this synthesis reaction is ethylene glycol:terephthalic acid = 30:70 (mass ratio).

[0027]

[0028] [In formula (1), n ​​is a stoichiometric coefficient (degree of polymerization) and is a number from 250 to 1100.]

[0029] Ethylene glycol is industrially produced by oxidizing and hydrating ethylene. Terephthalic acid is industrially produced by oxidizing paraxylene. As shown in FIG. 1 , when ethylene is obtained by dehydrating plant-derived ethanol (bioethanol) and PET is synthesized from ethylene glycol (bioethanol-derived ethylene glycol) synthesized from this ethylene and petrochemical-derived terephthalic acid, the resulting PET is 30% plant-derived by mass. As shown in FIG. 2 , when paraxylene is obtained by dehydrating plant-derived isobutanol (bioisobutanol) and PET is synthesized from terephthalic acid synthesized from this paraxylene and bioethanol-derived ethylene glycol, the resulting PET is 100% plant-derived by mass.

[0030] The synthesis reaction of PEF is shown in formula (2). PEF is synthesized by a dehydration reaction between n moles of ethylene glycol and n moles of furandicarboxylic acid (2,5-furandicarboxylic acid).

[0031]

[0032] [In formula (2), n is a stoichiometric coefficient (degree of polymerization) and is a number from 250 to 1100.]

[0033] Furandicarboxylic acid (FDCA) can be obtained, for example, by dehydrating plant-derived fructose or glucose to obtain hydroxymethylfurfural (HMF), which is then oxidized. As shown in Figure 3, when both FDCA and ethylene glycol are plant-derived, the resulting PEF is 100% plant-derived.

[0034] The content of the polyester-based resin relative to the total mass of the thermoplastic resin contained in the expanded beads is preferably 55 to 95 mass%, more preferably 55 to 75 mass%, even more preferably 60 to 75 mass%, and particularly preferably 60 to 70 mass%. If the content of the polyester-based resin is equal to or greater than the above-mentioned lower limit, moldability can be improved. If the content of the polyester-based resin is equal to or less than the above-mentioned upper limit, heat resistance strength can be further improved.

[0035] <Polyimide Resin> As the polyimide resin, a polymer containing a cyclic imide group as a repeating unit is preferred, and a polymer having a melt-molded body is more preferred. For example, U.S. Patent No. 4,141,927, Japanese Patent No. 2,622,678, Japanese Patent No. 2,606,912, Japanese Patent No. 2,606,914, Japanese Patent No. 2,596,565, Japanese Patent No. 2,596,566, polyetherimides described in Japanese Patent No. 2,598,478, Japanese Patent No. 2,598,536, Japanese Patent No. 2,599,171, JP-A-9-48,852, Japanese Patent No. 2,565,556, Japanese Patent No. 2,564,636, Japanese Patent No. 2,564,637, Japanese Patent No. 2,563,548, Japanese Patent No. 2,563,547, Japanese Patent No. 2,558,341, Japanese Patent No. 2,558,339, and Japanese Patent No. 2,834,580. The main chain of the polyimide resin may contain structural units other than cyclic imide as long as the effects of the present invention are not impaired. Examples of structural units other than cyclic imide include aromatic, aliphatic, alicyclic, alicyclic ester units, and oxycarbonyl units. The polyimide resin may also be made from recycled raw materials. The polyimide resin may also be a plant-derived resin such as biopolyimide. These polyimide resins may be used alone or in combination of two or more.

[0036] The polyimide resin is preferably, for example, a compound represented by the following formula (3).

[0037]

[0038] [In formula (3), R represents an aromatic group having 6 to 42 carbon atoms, and R' represents at least one divalent organic group selected from the group consisting of a divalent aromatic group having 6 to 30 carbon atoms, an aliphatic group having 2 to 30 carbon atoms, and an alicyclic group having 4 to 30 carbon atoms. p represents the number of repeating units.]

[0039] As the polyimide resin, a polyetherimide resin having a structural unit with an ether bond is preferred from the viewpoint of improving compatibility with polyester resins.

[0040] Polyimide resins can be prepared by conventionally known production methods. For example, they can be obtained by dehydration condensation of either or both of a tetracarboxylic acid and its acid anhydride, which are raw materials from which R in formula (3) can be derived, with one or more compounds selected from the group consisting of aliphatic primary diamines and aromatic primary diamines, which are raw materials from which R' in formula (3) can be derived. Specific examples of production methods for polyimide resins include a method in which a polyamic acid is obtained and then subjected to thermal ring closure. Other examples include a method in which a chemical ring closure is performed using an acid anhydride and a chemical ring closure agent such as pyridine or carbodiimide, or a method in which the tetracarboxylic acid anhydride and a diisocyanate from which R' can be derived are heated to decarboxylate and polymerize.

[0041] Examples of tetracarboxylic acids include pyromellitic acid, 1,2,3,4-benzenetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,2',3,3'-biphenyltetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 2,2',3,3'-benzophenonetetracarboxylic acid, bis(2,3-dicarboxyphenyl)methane, bis(3,4-dicarboxyphenyl)methane, 1,1'-bis(2,3-dicarboxyphenyl)ethane, and 2,2'-bis(3,4-dicarboxyphenyl). Examples of suitable acid anhydrides include propane, 2,2'-bis(2,3-dicarboxyphenyl)propane, bis(3,4-dicarboxyphenyl)ether, bis(2,3-dicarboxyphenyl)ether, bis(3,4-dicarboxyphenyl)sulfone, bis(2,3-dicarboxyphenyl)sulfone, 2,3,6,7-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 2,2'-bis[(2,3-dicarboxyphenoxy)phenyl]propane, and acid anhydrides thereof.

[0042] Examples of diamines include benzidine, diaminodiphenylmethane, diaminodiphenylethane, diaminodiphenylpropane, diaminodiphenylbutane, diaminodiphenylether, diaminodiphenylsulfone, diaminodiphenylbenzophenone, o, m, p-phenylenediamine, tolylenediamine, xylenediamine, and aromatic primary diamines having a hydrocarbon group of these aromatic primary diamines as a structural unit, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 2,2-dimethyl-1,3-propanediamine, 1,6-hexamethylenediamine, 1,8-dimethyl-2,2-dimethyl-1,3-propanediamine, 1,6-dimethyl-2,2-dimethyl-1,3-propane ... Examples of the diamine include 1,9-octamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,4-cyclohexanedimethylamine, 2-methyl-1,3-cyclohexanediamine, isophoronediamine, and the like, as well as aliphatic and alicyclic primary diamines having a hydrocarbon group of these aliphatic and alicyclic primary diamines as a structural unit.

[0043] The content of the polyimide resin relative to the total mass of the thermoplastic resin contained in the expanded beads is 5 to 45 mass%, preferably 25 to 45 mass%, and more preferably 25 to 40 mass%. If the content of the polyimide resin is equal to or greater than the lower limit, the heat resistance strength and flame retardancy can be further improved. If the content of the polyimide resin is equal to or less than the upper limit, the moldability can be further improved.

[0044] [Method for measuring the content of polyimide-based resin] When it is necessary to know the content of polyimide-based resin relative to the total mass of thermoplastic resin contained in the expanded beads and the expanded bead molding described below, the content of polyimide-based resin can be measured by the following method. For example, the expanded beads and the expanded bead molding can be sliced ​​to prepare thin samples (e.g., samples with a thickness of 0.2 mm), and the content of polyimide-based resin can be measured for these samples. An example of a method for measuring the content of polyimide-based resin relative to the total mass of a mixed resin of polyester-based resin and polyimide-based resin is shown below.

[0045] A sample having a thickness of 0.2 mm was cut out from the expanded beads and the expanded bead molded article, and this was used as the measurement sample. Infrared spectroscopic analysis of the measurement sample surface was carried out under the following conditions to obtain an infrared absorption spectrum. Measurement equipment: "Nicolet iS10" Fourier transform infrared spectrophotometer manufactured by Thermo SCIENTIFIC Corporation and single-reflection horizontal ATR Smart-iTR manufactured by Thermo SCIENTIFIC Corporation. ATR crystal: Diamond-attached KRS-5 (angle = 42°). Measurement method: Single-reflection ATR method. Measurement wavenumber range: 4000 cm －１ ~675cm －１ Wavenumber dependence of measurement depth: Uncorrected. Detector: Deuterated triglycine sulfate (DTGS) detector and KBr beam splitter. Resolution: 4 cm －１ - Number of accumulations: 16 (same for background measurement).

[0046] From the obtained infrared absorption spectrum chart, the peak heights of D1410 and D1778 are determined, and the content of polyimide resin is calculated from the following formula (p) obtained from a calibration curve prepared using a standard sample: Content of polyimide resin (mass%) = 100 - {1.987 × R ２ +19.589×R+22.44} ...(p) R=D1410 / D1778

[0047] D1410 is a polyester resin-derived wavelength of 1410 cm －１ ±5cm －１The maximum absorbance difference (measured absorbance - baseline absorbance) from the baseline in the infrared absorption spectrum curve in the region of 1400 cm. The baseline is the wave number of 1400 cm in the infrared absorption spectrum curve. －１ ±5cm －１ The minimum absorption position at 1420 cm in the infrared absorption spectrum curve －１ ±5cm －１ D1778 is the line connecting the minimum absorption position at the wave number 1778 cm of the polyimide resin. －１ ±5cm －１ The maximum absorbance difference (measured absorbance - baseline absorbance) from the baseline in the infrared absorption spectrum curve in the region of 1760 cm －１ ±5cm －１ The minimum absorption position at 1800 cm in the infrared absorption spectrum curve －１ ±5cm －１ The standard sample is prepared as follows.

[0048] [Preparation of Standard Sample] First, a mixture was prepared by mixing a polyester resin (PET: manufactured by Far Eastern New Century Co., Ltd., trade name "CH-653"), a polyimide resin (polyetherimide (PEI) resin: manufactured by SABIC Innovative Plastics, trade name "Ultem1000"), and pyromellitic dianhydride (PMDA) according to the formulation shown in Table 1. This mixture was placed in a Labo Plastomill twin-screw extruder (manufactured by Toyo Seiki Seisakusho, Ltd., model: 2D15W, bore diameter 15 mm, L / D = 17) and melt-kneaded at 350°C to prepare a resin composition. This resin composition was extruded through a nozzle die (diameter 3.0 mm) attached to the front end of the Labo Plastomill twin-screw extruder. The extruded resin composition was immediately cooled in a cooling water bath. The cooled strand-shaped resin composition is then thoroughly drained and cut into small pellets with a length of approximately 2 mm and a diameter of approximately 3 mm using a pelletizer to prepare standard samples (A to I). The compositions of the standard samples (A to I) are shown in Table 1.

[0049]

[0050] [Creation of Calibration Curve] The calibration curve is created as follows. Infrared spectroscopic analysis of the surfaces of the standard samples (A to I) is carried out under the following conditions to obtain infrared absorption spectra. Measurement equipment: "Nicolet iS10" Fourier transform infrared spectrophotometer manufactured by Thermo SCIENTIFIC Corporation and single-reflection horizontal ATR Smart-iTR manufactured by Thermo SCIENTIFIC Corporation. ATR crystal: Diamond-attached KRS-5 (angle = 42°). Measurement method: Single-reflection ATR method. Measurement wavenumber range: 4000 cm －１ ~675cm －１ Wavenumber dependence of measurement depth: Uncorrected. Detector: Deuterated triglycine sulfate (DTGS) detector and KBr beam splitter. Resolution: 4 cm －１ ・Number of measurements: 16 (same for background measurement) ・Number of measurements: 10

[0051] From the infrared absorption spectrum chart obtained in each measurement, data processing is performed in the same manner as when determining the content ratio of polyimide-based resin, the peak heights of D1410 and D1778 are determined, and the absorbance ratio (R = D1410 / D1778) is calculated. The blending ratio of polyester-based resin against the absorbance ratio of each standard sample (A to I) is plotted, and the logarithmic approximation formula in the plot is used as a calibration curve.

[0052] In the expanded beads, the mass ratio of polyester resin to polyimide resin is preferably 55:45 to 95:5, more preferably 60:40 to 85:15, and even more preferably 60:40 to 75:25.

[0053] The thermoplastic resin contained in the expanded beads may contain recycled materials. The recycled materials may be contained in either the polyester resin or the polyimide resin, or in both the polyester resin and the polyimide resin. A portion or all of the polyester resin may be recycled polyester resin materials, or a portion or all of the polyimide resin may be recycled polyimide resin materials. Examples of recycled materials include the following: 1) Recovered pellets obtained by crushing expanded beads or foams such as expanded bead molded articles, remelting the resin flakes in an extruder, extruding them into strands through a nozzle die, cooling them, and pelletizing them. 2) Recycled PET obtained by crushing PET bottles, remelting the resin flakes in an extruder, extruding them into strands through a nozzle die, cooling them, and pelletizing them.

[0054] Phosphorus-Based Flame Retardants Phosphorus-based flame retardants include phosphate compounds, polyphosphate compounds, red phosphorus, organic phosphate ester compounds, phosphazene compounds, phosphonic acid compounds, phosphinic acid compounds, phosphine oxide compounds, phosphorane compounds, and phosphoramide compounds. Phosphate compounds include melamine phosphate, guanidine phosphate, ammonium phosphate, ammonium amide phosphate, and carbamate phosphate. Polyphosphate compounds include melamine polyphosphate, guanidine polyphosphate, ammonium amide phosphate, and carbamate polyphosphate. Phosphorus-based flame retardants include various phosphorus-containing compounds, such as low-molecular-weight compounds and polymeric compounds having repeating units. These phosphorus-based flame retardants are included in the mass excluding the total mass of ash and blowing agent. Therefore, in the present invention, the phosphorus-based flame retardant is treated as part of the thermoplastic resin. The phosphorus-based flame retardant may be blended alone into the resin composition or as a masterbatch (MB). The above-mentioned phosphorus-based flame retardants may be used alone or in combination of two or more. These phosphorus-based flame retardants may be used in combination with other flame retardants than phosphorus-based flame retardants, such as halogen-based flame retardants, nitrogen-based flame retardants, silicon-based flame retardants, and inorganic flame retardants, as long as the effects of the present invention are not impaired.

[0055] The content of the phosphorus-based flame retardant is preferably 0.15 to 1.00 mass%, more preferably 0.25 to 0.90 mass%, and even more preferably 0.25 to 0.80 mass%, expressed as the phosphorus content (elemental phosphorus content) relative to the total mass of the thermoplastic resin. If the phosphorus content is equal to or greater than the lower limit, flame retardancy can be improved. If the phosphorus content is equal to or less than the upper limit, moldability can be improved.

[0056] <<Other Resins>> The expanded beads are substantially free of thermosetting resins. "Substantially free" means that the expanded beads are completely free of thermosetting resins or contain only a small amount of thermosetting resin that does not affect the quality of the expanded beads. The content of the thermosetting resin in the expanded beads is preferably 5.0% by mass or less, more preferably 2.0% by mass or less, even more preferably 1.0% by mass or less, and most preferably 0% by mass, based on 100 parts by mass of the thermoplastic resin.

[0057] The thermoplastic resin may include a thermoplastic resin (other thermoplastic resin) other than the polyester resin and the polyimide resin, such as a polyolefin resin (e.g., polyethylene or polypropylene), a polystyrene resin, a polyphenylene ether resin, a polyamide resin, a polycarbonate resin, a polyarylate resin, a polyphenylsulfone resin, a polysulfone resin, or a polyethersulfone resin.

[0058] The total proportion of the polyester resin and the polyimide resin relative to the total mass of the thermoplastic resin is preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 98 mass% or more, and particularly preferably 99 mass% or more. When the total proportion of the polyester resin and the polyimide resin is equal to or more than the lower limit, the heat resistance strength of the expanded beads can be further increased.

[0059] <Blowing Agent> Known blowing agents can be used as the blowing agent. Blowing agents can be broadly divided into physical blowing agents and chemical blowing agents. Of these, it is preferable to use a physical blowing agent. Examples of physical blowing agents include saturated aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, and hexane; ethers such as dimethyl ether; chlorofluorocarbons such as methyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, and monochlorodifluoromethane; carbon dioxide; and nitrogen. Dimethyl ether, propane, normal butane, isobutane, carbon dioxide, and nitrogen are preferred. These blowing agents may be used alone or in combination of two or more.

[0060] The content of the foaming agent is not particularly limited, but is preferably, for example, 0.10 to 12 parts by mass relative to 100 parts by mass of the thermoplastic resin.

[0061] <Optional Components> The expanded beads of the present embodiment may contain other components (optional components) in addition to the thermoplastic resin and the blowing agent. Examples of the optional components include a cell regulator, a stabilizer, an ultraviolet absorber, a colorant, an antioxidant, a crystallization accelerator, a lubricant, a crosslinking agent, a surfactant, a shrinkage inhibitor, a flame retardant, and a deterioration inhibitor.

[0062] Examples of crosslinking agents include acid dianhydrides such as pyromellitic dianhydride, polyfunctional epoxy compounds, oxazoline compounds, and oxazine compounds. Adding a crosslinking agent to the resin composition suppresses cell breakage during foaming and further reduces the open cell ratio. The content of the crosslinking agent is preferably 0.080 to 0.80 parts by mass, more preferably 0.15 to 0.50 parts by mass, even more preferably 0.20 to 0.45 parts by mass, and particularly preferably 0.25 to 0.40 parts by mass, per 100 parts by mass of the resin. When the content of the crosslinking agent is equal to or greater than the lower limit, the Z-average molecular weight Mz of the expanded beads can be further increased, thereby further improving moldability. When the content of the crosslinking agent is equal to or less than the upper limit, the expanded beads can be well expanded during in-mold foaming and can be well thermally fused to each other, thereby further improving moldability.

[0063] The cell regulator is, for example, a mixture of inorganic powders such as talc and silica. These cell regulators increase the closed cell rate of the expanded beads and facilitate the formation of expanded beads. The content of the cell regulator is preferably, for example, 0.20 to 5.0 parts by mass per 100 parts by mass of the thermoplastic resin.

[0064] Examples of the stabilizer include calcium zinc-based heat stabilizers, tin-based heat stabilizers, lead-based heat stabilizers, etc. The content of the stabilizer is preferably, for example, 1.0 part by mass or less with respect to 100 parts by mass of the thermoplastic resin.

[0065] Examples of the ultraviolet absorber include a cesium oxide-based ultraviolet absorber, a titanium oxide-based ultraviolet absorber, etc. The content of the ultraviolet absorber is preferably, for example, 1.0 part by mass or less with respect to 100 parts by mass of the thermoplastic resin.

[0066] Examples of the antioxidant include cerium oxide, cerium oxide / zirconia solid solution, cerium hydroxide, carbon, carbon nanotubes, titanium oxide, and fullerene. The content of the antioxidant is preferably, for example, 1.0 part by mass or less relative to 100 parts by mass of the thermoplastic resin.

[0067] Examples of colorants include titanium oxide, carbon black, titanium yellow, iron oxide, ultramarine, cobalt blue, calcined pigments, metallic pigments, mica, pearl pigments, zinc oxide, precipitated silica, and cadmium red. When the expanded beads of this embodiment are used in food containers, it is preferable to select a colorant registered with the Hygienic Council from among the above colorants. The content of the colorant is preferably, for example, 2.0 parts by mass or less per 100 parts by mass of the thermoplastic resin.

[0068] Examples of the crystallization accelerator include silicates, carbon, metal oxides, etc. Examples of silicates include talc, which is hydrous magnesium silicate. Examples of carbon include carbon black, carbon nanofibers, carbon nanotubes, carbon nanohorns, activated carbon, graphite, graphene, coke, mesoporous carbon, glassy carbon, hard carbon, and soft carbon. Examples of carbon black include furnace black, acetylene black, ketjen black, and thermal black. Examples of metal oxides include zinc oxide and titanium oxide. The content of the crystallization accelerator is preferably, for example, 3.0 parts by mass or less relative to 100 parts by mass of the thermoplastic resin.

[0069] The optional components may be used alone or in combination of two or more. The total amount of the optional components contained in the expanded beads is preferably 0.10 to 5.0 parts by mass, more preferably 0.50 to 3.0 parts by mass, based on the total mass of the expanded beads.

[0070] <Physical Properties> Expanded beads exhibit a single glass transition temperature Tg. The compatibility of the polyester resin and the polyimide resin results in a single glass transition temperature Tg. The single glass transition temperature Tg of the expanded beads is higher than the glass transition temperature Tg of the polyester resin, thereby increasing the heat resistance strength of the expanded bead molding. Note that "single glass transition temperature" refers to a single glass transition temperature Tg that can be recognized as being lower than the crystallization peak observed in the second heating process in a heat flux differential scanning calorimetry chart (DSC curve) at a heating rate of 10°C / min. However, if no crystallization peak is observed in the second heating process, this refers to a single glass transition temperature Tg that can be recognized as being lower than the crystallization peak observed in the second heating process in the temperature range (30 to 300°C) of the second heating process. The glass transition temperature Tg of the expanded beads is, for example, preferably 80 to 130°C, more preferably 80 to 125°C, even more preferably 80 to 120°C, and particularly preferably 80 to 100°C. When Tg is equal to or greater than the above lower limit, the heat resistance strength and dimensional stability upon heating of the expanded bead molded article can be further improved. When Tg is equal to or less than the above upper limit, the molding cycle can be shortened to increase productivity and moldability. The glass transition temperature Tg of the expanded beads can be determined by heat flux differential scanning calorimetry at a heating rate of 10°C / min. The glass transition temperature Tg of the expanded beads can be considered to be the same as the glass transition temperature Tg of the thermoplastic resin constituting the expanded beads.

[0071] The absolute value of the difference between the amount of heat absorbed and the amount of heat generated in the expanded beads (endothermic heat generation difference) is preferably 3 to 35 J / g, more preferably 5 to 25 J / g, and even more preferably 7 to 15 J / g. When the endothermic heat generation difference is equal to or greater than the above-mentioned lower limit, the degree of crystallinity is increased, and the heat resistance strength and dimensional stability upon heating of the expanded bead molded article can be further improved. When the endothermic heat generation difference is equal to or less than the above-mentioned upper limit, the degree of crystallinity is not too high, and excellent secondary foaming properties and heat fusion properties are exhibited, thereby improving moldability and mechanical strength. The endothermic heat generation difference is the difference between the amount of heat absorbed and the amount of heat generated, determined by heat flux differential scanning calorimetry at a heating rate of 10°C / min. Note that the endothermic heat generation difference in the expanded beads can be considered to be the same as the endothermic heat generation difference of the thermoplastic resin constituting the expanded beads.

[0072] The size of the expanded beads is appropriately selected depending on the application, and the average particle diameter of the expanded beads is, for example, 0.50 to 5.0 mm. The average particle diameter of the expanded beads is a value expressed as D50. Specifically, using a low tap type sieve shaker (manufactured by Iida Seisakusho Co., Ltd.), JIS standard sieves (JIS Approximately 25 g of sample was classified for 10 minutes using a sieve (Z8801-1:2006), and the weight of the sample on the sieve was measured. A cumulative weight distribution curve was created from the obtained results, and the particle diameter (median diameter) at which the cumulative weight reached 50% was taken as the average particle diameter.

[0073] The open cell ratio of the expanded beads is preferably 20% or less, more preferably 18% or less, and even more preferably 16% or less. When the open cell ratio of the expanded beads is equal to or less than the above upper limit, the secondary expandability of the expanded beads can be further improved, and the moldability and mechanical strength can be further improved. The open cell ratio of the expanded beads can be determined by the method described in JIS K7138:2006 "Rigid foam plastics - Determination of open cell ratio and closed cell ratio."

[0074] The bulk density of the expanded particles is, for example, 0.027 to 0.675 g / cm ３ is preferred, and 0.045 to 0.45 g / cm ３ More preferably, 0.0675 to 0.27 g / cm ３ When the bulk density is equal to or greater than the above lower limit, the cushioning power of the expanded bead molding can be increased, and when the bulk density is equal to or less than the above upper limit, the mechanical strength of the expanded bead molding can be increased.

[0075] The bulk expansion ratio of the expanded beads is, for example, preferably 2 to 50 times, more preferably 3 to 30 times, and even more preferably 5 to 20 times. If the bulk expansion ratio is equal to or greater than the lower limit, the amount of resin per volume can be further reduced, thereby increasing the cushioning force. If the bulk expansion ratio is equal to or less than the upper limit, the mechanical strength can be increased.

[0076] The average cell diameter of the expanded beads is, for example, preferably 5 to 500 μm, more preferably 10 to 400 μm, and even more preferably 20 to 300 μm. If the average cell diameter is equal to or greater than the above lower limit, the cushioning force can be increased. If the average cell diameter is equal to or less than the above upper limit, the mechanical strength can be increased. The average cell diameter can be measured in accordance with the test method of ASTM D3576-77.

[0077] The temperature at which the loss tangent tanδ of the expanded beads is maximized in solid viscoelasticity measurement at a heating rate of 5°C / min and a frequency of 1 Hz is preferably 120 to 230°C, more preferably 130 to 225°C, and even more preferably 150 to 220°C. If the temperature at which the loss tangent tanδ is maximized is equal to or greater than the above-mentioned lower limit, the temperature at which the expanded bead molding softens increases, thereby further improving the heat resistance strength of the expanded bead molding. If the temperature at which the loss tangent tanδ is maximized is equal to or less than the above-mentioned upper limit, the temperature at which the expanded bead molding softens does not become excessively high, thereby further improving moldability. The temperature at which the loss tangent tanδ of the expanded beads is maximized can be determined by molding an expanded bead molding and measuring the solid viscoelasticity of the expanded bead molding.

[0078] The Z-average molecular weight Mz of the expanded beads is 2.5 × 10 ５ ~5.0 x 10 ５ is 2.9 × 10 ５ ~5.0 x 10 ５ is preferred, and 3.2 × 10 ５ ~5.0 x 10 ５ When the Z-average molecular weight Mz of the expanded beads is equal to or greater than the lower limit, the open cell ratio of the expanded beads can be suppressed, and moldability can be improved. When the Z-average molecular weight Mz of the expanded beads is equal to or less than the upper limit, the expanded beads can be well expanded and well heat-fused together during in-mold foam molding, and moldability can be improved.

[0079] The number average molecular weight Mn of the expanded beads is 0.10 × 10 ５ ~0.30 x 10 ５ is preferable, and 0.15 × 10 ５ ~0.25 x 10 ５ More preferably, 0.18 × 10 ５ ~0.23 x 10 ５ When the number average molecular weight Mn of the expanded beads is equal to or greater than the above lower limit, the impact resistance can be improved. When the number average molecular weight Mn of the expanded beads is equal to or less than the above upper limit, the moldability can be further improved.

[0080] The mass average molecular weight Mw of the expanded beads is 0.50 × 10 ５ ~2.0 x 10 ５ is preferable, and 0.70 × 10 ５ ~1.5 x 10 ５ More preferably, 0.80 × 10 ５ ~1.2 × 10 ５ When the mass average molecular weight Mw of the expanded beads is equal to or greater than the above lower limit, the impact resistance can be improved. When the mass average molecular weight Mw of the expanded beads is equal to or less than the above upper limit, the moldability can be further improved.

[0081] The molecular weight distribution of the expanded beads, expressed as Mw / Mn, is preferably 3.0 to 7.0, more preferably 3.5 to 6.5, and even more preferably 4.0 to 6.0. When the molecular weight distribution of the expanded beads is equal to or greater than the lower limit, the impact resistance can be further improved. When the molecular weight distribution of the expanded beads is equal to or less than the upper limit, the moldability can be further improved.

[0082] The number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the expanded beads are adjusted by combining the types and amounts of the raw polyester resin and raw polyimide resin, which will be described later, and the type and amount of the crosslinking agent, etc. The number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the expanded beads can be considered to be the same as the number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the thermoplastic resin that constitutes the expanded beads.

[0083] [Method for measuring number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz] The number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz can be measured by the following method. 5 mg of sample is taken from the object to be measured, and 0.5 mL of hexafluoroisopropanol (HFIP) and 0.5 mL of chloroform are added thereto, in that order, and gently shaken manually. This is left to soak for 6±1.0 hours. After confirming that the sample is completely dissolved, it is diluted with chloroform to 10 mL, and this is gently shaken manually and mixed. The solution is then filtered through a non-aqueous 0.45 μm chromatodisc manufactured by GL Sciences Inc. or a non-aqueous 0.45 μm syringe filter manufactured by Shimadzu GLC Corporation to obtain a measurement sample. The measurement sample is measured using a chromatograph under the following measurement conditions, and the number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the sample are determined from a previously prepared standard polystyrene calibration curve.

[0084] [Measurement equipment] Measurement equipment = Tosoh Corporation's "HLC-8320GPC EcoSEC" gel permeation chromatograph (built-in RI detector and UV detector). [GPC measurement conditions] Columns <Sample side> Guard column = Tosoh Corporation's TSK guard column HXL-H (6.0 mm x 4.0 cm) x 1. Measurement column = Tosoh Corporation's 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 (254 nm). Injection volume = 15 μL. Measurement time = 25 minutes. Sampling pitch = 500 ms.

[0085] [Standard Polystyrene Samples for Calibration Curve] Standard polystyrene samples for calibration curve were obtained from Showa Denko K.K. under the trade names "STANDARD SM-105" and "STANDARD SH-75" and had mass average molecular weights Mw 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 standard polystyrenes for the calibration curve were grouped into 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). A was weighed (2 mg, 3 mg, 4 mg, 4 mg, 4 mg) and dissolved in 30 mL of chloroform. B was weighed (3 mg, 4 mg, 4 mg, 4 mg, 4 mg) and dissolved in 30 mL of chloroform. The standard polystyrene 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 calibration curve was used to calculate the number average molecular weight Mn, mass average molecular weight Mw, and Z-average molecular weight Mz.

[0086] The crystallinity of the expanded beads is preferably 3.0 to 10%, more preferably 3.0 to 9.0%, and even more preferably 3.0 to 7.0%. When the crystallinity of the expanded beads is equal to or greater than the lower limit, heat resistance is further improved. When the crystallinity of the expanded beads is equal to or less than the upper limit, secondary expansion occurs well during in-mold expansion molding, and the expanded beads are more firmly heat-fused together, thereby further increasing the mechanical strength of the expanded bead molding. The crystallinity can be adjusted by combining the type and amount of crosslinking agent, the temperature during production of the expanded beads, etc.

[0087] <Production Method> Examples of the method for producing expanded beads of the present invention include a method of extruding a resin composition containing a thermoplastic resin and a blowing agent, foaming the extruded resin composition, and then forming expanded beads; and a method of extruding a thermoplastic resin to form resin particles, impregnating the resulting resin particles with a blowing agent to form expandable particles, and then heating the expandable particles to form expanded beads. More specific examples of the method for producing expanded beads include the following: 1) A method of feeding a thermoplastic resin and a blowing agent into an extruder, melt-kneading the resin composition, extruding the molten resin composition into the air through a die hole at the end of the extruder to foam it, cutting the extruded and foamed resin composition simultaneously, and cooling the cut expanded spherical particles in water to obtain expanded beads. 2) A method of feeding a thermoplastic resin and a blowing agent into an extruder, melt-kneading the resin composition, extruding the molten resin composition into the water through a die hole at the end of the extruder to foam it, cooling the extruded and foamed resin composition simultaneously, and cutting the cut expanded spherical particles in water to obtain expanded beads. 3) A method of feeding a thermoplastic resin and a blowing agent into an extruder and melt-kneading them, extruding the molten resin composition through a die hole at the tip of the extruder into water and cooling it, cutting it while extruding and cooling it to obtain cut spherical expandable particles, and heating the expandable particles to obtain expanded particles. 4) A method of feeding a thermoplastic resin into an extruder and melt-kneading it, extruding the molten thermoplastic resin through a die hole at the tip of the extruder into the air and cutting it while extruding it, throwing the cut spherical resin particles into water and cooling it to obtain resin particles, impregnating the resin particles with a blowing agent to obtain expandable particles, and heating the expandable particles to obtain expanded particles. 5) A method of feeding a thermoplastic resin into an extruder and melt-kneading it, extruding the molten thermoplastic resin through a die hole at the tip of the extruder into water and cooling it, cutting it while extruding it while cooling it to obtain cut spherical resin particles, impregnating the resin particles with a blowing agent to obtain expandable particles, and heating the expandable particles to obtain expanded particles. 6) A method in which a thermoplastic resin is fed into an extruder and melted and kneaded, the molten thermoplastic resin is extruded in the form of strands from holes in a die provided at the tip of the extruder, and after extrusion, the resin is introduced into water to cool, and after cooling, the resin is cut to a predetermined length to obtain columnar resin particles, the resin particles are impregnated with a blowing agent to obtain expandable particles, and the expandable particles are heated to obtain expandable particles.

[0088] The method of extruding a resin composition into the air to foam it, cutting it into spherical particles, and then dropping them into water to cool will be described in more detail below.

[0089] An extruder used in producing expanded beads of the present invention will be described. The expanded bead production apparatus 10 shown in Fig. 4 has an extruder (not shown) and a nozzle die 1 provided at the tip of the extruder. A rotating shaft 2 is connected to the tip of the nozzle die 1. The rotating shaft 2 passes through a front portion 41a of a cooling drum 41 constituting a cooling member 4 (described later) and is connected to a driving member 3 such as a motor. A plurality of nozzle outlets 11 are formed at equal intervals on the front end surface 1a of the nozzle die 1 on the same imaginary circle A centered on the rotating shaft 2 (see Fig. 5).

[0090] The number of nozzles in the nozzle mold 1 (i.e., the number of outlets 11) is preferably 2 to 80. A single nozzle may result in a decrease in the production efficiency of expanded beads. A nozzle number greater than 80 may result in contact and coalescence between extruded foams extruded from adjacent nozzles. Furthermore, expanded beads obtained by cutting the extruded foam may coalesce. The number of nozzles is more preferably 5 to 60, and particularly preferably 8 to 50. The diameter (opening diameter) of the nozzle outlet 11 in the nozzle mold 1 is preferably 0.20 to 2.0 mm. If the opening diameter of the outlet 11 is less than 0.20 mm, the extrusion pressure may become too high, making extrusion foaming difficult. If the opening diameter of the outlet 11 is greater than 2.0 mm, the diameter of the expanded beads may become too large, resulting in a decrease in the efficiency of filling the mold. The opening diameter of the outlet 11 is more preferably 0.30 to 1.6 mm, and particularly preferably 0.40 to 1.2 mm. The length of the land portion of the nozzle die 1 is preferably 4 to 30 times the opening diameter of the outlet portion 11 of the nozzle of the nozzle die 1. If the length is less than 4 times, fractures may occur and stable extrusion foaming may not be possible. If the length is more than 30 times, too much pressure may be applied to the nozzle die 1, making extrusion foaming impossible. The length of the land portion is more preferably 5 to 20 times.

[0091] A rotary shaft 2 is disposed in a forwardly protruding manner in a portion of the front end surface 1a of the nozzle mold 1 surrounded by the nozzle outlet 11. One or more rotary blades 5 are integrally provided on the outer peripheral surface of the rear end of the rotary shaft 2, and all of the rotary blades 5 are constantly in contact with the front end surface 1a during rotation. When multiple rotary blades 5 are integrally provided on the rotary shaft 2, the multiple rotary blades 5 are arranged at equal intervals circumferentially around the rotary shaft 2. FIG. 5 shows, as an example, a case in which four rotary blades 5 are integrally provided on the outer peripheral surface of the rotary shaft 2. As the rotary shaft 2 rotates, the rotary blades 5 move along an imaginary circle A, which defines the nozzle outlet 11, while constantly in contact with the front end surface 1a, so as to be able to cut the extruded foam extruded from the nozzle outlet 11 in a sequential and continuous manner. The expanded bead manufacturing apparatus 10 is provided with a cooling member 4 surrounding at least the front end surface 1a of the nozzle mold 1 and the rotary shaft 2. The cooling member 4 includes a cylindrical cooling drum 41 with a bottom, which has a front portion 41a that is circular from the front and has a larger diameter than the nozzle mold 1, and a cylindrical peripheral wall portion 41b that extends rearward from the outer periphery of the front portion 41a.

[0092] A supply port 41c for supplying the cooling liquid 42 is formed in an area of ​​the peripheral wall 41b facing the outer surface of the nozzle die 1. The supply port 41c penetrates the peripheral wall 41b. A supply pipe 41d for supplying the cooling liquid 42 into the cooling drum 41 is connected to the supply port 41c on the outer surface of the peripheral wall 41b. The cooling liquid 42 is configured to be supplied obliquely forward through the supply pipe 41d along the inner circumferential surface of the peripheral wall 41b of the cooling drum 41.

[0093] An outlet 41e is formed on the lower surface of the front end of the peripheral wall 41b. The outlet 41e penetrates the peripheral wall 41b. An outlet pipe 41f is connected to the outlet 41e on the outer surface of the peripheral wall 41b. The extruder is not particularly limited as long as it is a conventional, commonly used extruder, and examples thereof include a single-screw extruder, a twin-screw extruder, and a tandem extruder in which multiple extruders are connected together.

[0094] A method for manufacturing expanded beads using the expanded bead manufacturing apparatus 10 will now be described. Coolant 42 is supplied from the supply pipe 41d into the cooling drum 41 via the supply port 41c. The supplied coolant 42 advances forward (toward the front portion 41a) in a spiral pattern along the inner circumferential surface of the peripheral wall portion 41b due to centrifugal force associated with the flow rate at the time of supply. As the coolant 42 advances along the inner circumferential surface of the peripheral wall portion 41b, it gradually spreads in a direction perpendicular to the direction of advancement (i.e., the circumferential direction of the peripheral wall portion 41b). The coolant 42 that has spread in the circumferential direction of the peripheral wall portion 41b completely covers the inner circumferential surface of the peripheral wall portion 41b forward of the supply port 41c.

[0095] The cooling liquid 42 is not particularly limited as long as it can cool the expanded beads, and examples thereof include water, alcohol, etc., but water is preferred in consideration of disposal after use. The temperature of the cooling liquid 42 is preferably 10 to 40°C. If the temperature of the cooling liquid is 10°C or higher, the nozzle die 1 located near the cooling drum 41 will not be excessively cooled, and the resin composition can be more smoothly extruded from the outlet portion 11. If the temperature of the cooling liquid is 40°C or lower, the particulate cut material can be cooled more quickly.

[0096] The glass transition temperature Tg of the polyester resin (raw material polyester resin) blended into the resin composition is preferably 50 to 100°C, more preferably 60 to 90°C, and even more preferably 70 to 85°C. If the Tg is equal to or greater than the lower limit, the heat resistance strength and dimensional stability under heat can be further improved. If the Tg is equal to or less than the upper limit, the molding cycle can be shortened to increase productivity and improve moldability. Note that "moldability" refers to, for example, the ability to approximate a desired shape when the expanded beads are filled into a mold cavity and heated to cause secondary expansion; the closer the shape is to the desired shape, the "better" the moldability.

[0097] The melting point of the raw material polyester resin is preferably 230 to 270°C, more preferably 240 to 260°C, and even more preferably 245 to 255°C. If the melting point is equal to or higher than the lower limit, the heat resistance strength and dimensional stability under heat can be further improved. If the melting point is equal to or lower than the upper limit, the molding cycle can be shortened to increase productivity and moldability.

[0098] The intrinsic viscosity (IV value) of the raw material polyester resin is preferably 0.50 to 1.5, more preferably 0.60 to 1.3, and even more preferably 0.70 to 1.2. If the IV value is equal to or greater than the lower limit, cell breakage during foaming can be suppressed, further reducing the open cell ratio. If the IV value is equal to or less than the upper limit, the density can be reduced, the surface of the expanded bead molding can be made smoother, and the appearance can be improved. The IV value can be measured by the method of JIS K7367-5 (2000).

[0099] The number average molecular weight Mn of the raw material polyester resin is 0.050 × 10 ５ ~0.40 x 10 ５ is preferable, and 0.10 × 10 ５ ~0.35 x 10 ５ More preferably, 0.15 × 10 ５ ~0.30 x 10 ５ When the number average molecular weight Mn of the raw material polyester resin is equal to or greater than the lower limit, the impact resistance can be improved. When the number average molecular weight Mn of the raw material polyester resin is equal to or less than the upper limit, the heat resistance can be further improved.

[0100] The mass average molecular weight Mw of the raw material polyester resin is 0.30 × 10 ５ ~1.3 × 10 ５ is preferable, and 0.40 × 10 ５ ~1.2 × 10 ５ More preferably, 0.50 × 10 ５ ~1.2 × 10 ５ When the mass average molecular weight Mw of the raw material polyester resin is within the above range, the impact resistance can be further improved.

[0101] The Z-average molecular weight Mz of the raw material polyester resin is 0.20 × 10 ５ ~2.5 x 10 ５ is preferable, and 0.30 × 10 ５ ~2.0 x 10 ５ More preferably, 0.90 × 10 ５ ~1.8 x 10 ５When the Z-average molecular weight Mz of the raw material polyester resin is equal to or greater than the lower limit, the heat resistance can be improved. When the Z-average molecular weight Mz of the raw material polyester resin is equal to or less than the upper limit, the moldability can be improved.

[0102] The molecular weight distribution of the raw material polyester resin, expressed as Mw / Mn, is preferably 1.5 to 5.0, more preferably 2.0 to 4.0, and even more preferably 2.5 to 3.5. When the Mw / Mn of the raw material polyester resin is within the above range, moldability can be further improved. The number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the raw material polyester resin can be measured by the same methods as those for the number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the expanded beads.

[0103] The glass transition temperature Tg of the polyimide resin (raw material polyimide resin) blended into the resin composition is preferably 190 to 240°C, more preferably 200 to 230°C, and even more preferably 210 to 220°C. When the glass transition temperature Tg of the raw material polyimide resin is equal to or higher than the above lower limit, the heat resistant strength and heat resistance can be further improved. When the glass transition temperature Tg of the raw material polyimide resin is equal to or lower than the above upper limit, the molding cycle can be shortened to increase productivity and moldability.

[0104] The melt flow rate (MFR) of the raw material polyimide resin is preferably 3.0 to 30 g / 10 min, more preferably 5.0 to 25 g / 10 min, and even more preferably 7.0 to 20 g / 10 min. When the MFR of the raw material polyimide resin is equal to or greater than the lower limit, the molding cycle can be shortened, improving productivity and moldability. When the MFR is equal to or less than the upper limit, the heat resistance strength and heat resistance can be further improved.

[0105] The number average molecular weight Mn of the raw material polyimide resin is 0.10 × 10 ５ ~0.50 x 10 ５ is preferable, and 0.15 × 10 ５ ~0.30 x 10 ５ More preferably, 0.20 × 10 ５ ~0.25 x 10 ５When the number average molecular weight Mn of the raw material polyimide resin is equal to or greater than the lower limit, the impact resistance can be further improved. When the number average molecular weight Mn of the raw material polyimide resin is equal to or less than the upper limit, the moldability can be further improved.

[0106] The mass average molecular weight Mw of the raw material polyimide resin is 0.20 × 10 ５ ~0.80 x 10 ５ is preferable, and 0.30 × 10 ５ ~0.70 x 10 ５ More preferably, 0.40 × 10 ５ ~0.60 x 10 ５ When the mass average molecular weight Mw of the raw material polyimide resin is equal to or greater than the above lower limit, the impact resistance can be further improved. When the mass average molecular weight Mw of the raw material polyimide resin is equal to or less than the above upper limit, the moldability can be further improved.

[0107] The Z-average molecular weight Mz of the raw material polyimide resin is 0.40 × 10 ５ ~1.2 × 10 ５ is preferable, and 0.50 × 10 ５ ~1.0 x 10 ５ More preferably, 0.60 × 10 ５ ~0.90 x 10 ５ When the Z-average molecular weight Mz of the raw material polyimide resin is equal to or greater than the lower limit, the heat resistance can be improved. When the Z-average molecular weight Mz of the raw material polyimide resin is equal to or less than the upper limit, the moldability can be improved.

[0108] The molecular weight distribution of the raw material polyimide resin, expressed as Mw / Mn, is preferably 1.0 to 3.0, more preferably 1.5 to 2.5, and even more preferably 2.0 to 2.5. When the Mw / Mn of the raw material polyimide resin is within the above range, moldability can be further improved. The number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the raw material polyimide resin can be measured by the same methods as those for the number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the expanded beads.

[0109] These resin compositions are extruded from the nozzle outlet 11 while rotating the rotary blades 5. The resin composition is extruded and foamed from the nozzle die 1 to form an extruded foam, which is then cut by the rotary blades 5 into granular cut pieces. All of the rotary blades 5 rotate while constantly contacting the front end faces 1a, and the extruded foam extruded and foamed from the nozzle die 1 is cut into granular cut pieces in the atmosphere at regular time intervals by shear stress generated between the rotary blades 5 and the edge of the nozzle outlet 11. At this time, water may be sprayed onto the extruded foam in a mist form, as long as the extruded foam is not excessively cooled.

[0110] The resin composition is prevented from foaming within the nozzle of the nozzle mold 1. The resin composition is not yet foamed immediately after being discharged from the nozzle outlet 11 and begins to foam a short time after being discharged. Therefore, the extruded foam consists of an unfoamed portion immediately after being discharged from the nozzle outlet 11 and a foamed portion that is continuous with the unfoamed portion and is extruded prior to the unfoamed portion. The unfoamed portion maintains its state from the time of being discharged from the nozzle outlet 11 until foaming begins. The time for which this unfoamed portion is maintained can be adjusted by the resin pressure at the nozzle outlet 11, the amount of foaming agent, etc. If the resin pressure at the nozzle outlet 11 is high, the resin composition will not foam immediately after being extruded from the nozzle mold 1 and will maintain an unfoamed state. The discharge pressure of the thermoplastic resin at the nozzle outlet 11 can be adjusted by the opening diameter of the nozzle outlet 11, the extrusion rate, and the melt viscosity and melt tension of the resin composition. In addition, by adjusting the amount of foaming agent to an appropriate amount, it is possible to prevent the thermoplastic resin composition from foaming inside the nozzle die 1 and reliably form an unfoamed portion. Since all of the rotary blades 5 cut the extruded foam while always in contact with the front end face 1a, the extruded foam becomes particulate cut pieces in the unfoamed portion immediately after being discharged from the nozzle outlet 11.

[0111] The rotation speed of the rotary blade 5 is preferably 2,000 to 10,000 rpm, more preferably 2,000 to 9,000 rpm, and particularly preferably 2,000 to 8,000 rpm. If the rotation speed is equal to or greater than the lower limit, the extruded foam can be cut more reliably by the rotary blade 5, preventing coalescence and allowing the foamed particles to have a more uniform shape. If the rotation speed is equal to or less than the upper limit, a sufficient time is ensured for the foam to reach the cooling liquid 42, which will be described later, and the bulk expansion ratio can be further increased.

[0112] As shown in FIG. 6 , the granular cut pieces P cut by the rotary blade 5 are simultaneously scattered toward the inner wall of the cooling drum 41 due to the cutting stress of the rotary blade 5 and collide with the cooling liquid 42 that coats the inner circumferential surface of the peripheral wall portion 41b. The granular cut pieces continue to foam before colliding with the cooling liquid 42, and grow into a substantially spherical shape. Therefore, the resulting foamed beads are substantially spherical. At this time, it is preferable that the granular cut pieces P collide with the cooling liquid 42 obliquely relative to the surface of the cooling liquid 42 and from upstream to downstream in the flow direction X of the cooling liquid 42 (see FIG. 6 ). When the granular cut pieces P collide with the cooling liquid 42, by colliding with the cooling liquid 42 in a direction following the flow of the cooling liquid 42, the granular cut pieces P are not repelled by the surface of the cooling liquid 42, but smoothly and reliably enter the cooling liquid 42, are cooled by the cooling liquid 42, and become foamed beads.

[0113] According to this embodiment, after the extruded foam is cut by the rotary blade 5, the cut particles are immediately cooled with the cooling liquid 42, thereby preventing excessive expansion of the cut particles and obtaining expanded beads with the desired bulk expansion ratio. In addition, because the cut particles are immediately cooled after cutting the extruded foam, an increase in the crystallinity of the expanded beads is suppressed. As a result, the expanded beads exhibit excellent secondary expandability and heat fusion properties, and the resulting expanded bead moldings have excellent mechanical strength. Furthermore, by increasing the crystallinity of the expanded bead moldings during in-mold expansion molding, the dimensional stability under heating can be further improved.

[0114] The expanded beads cooled by the cooling liquid 42 flow together with the cooling liquid 42 through the discharge port 41e into the discharge pipe 41f and are discharged out of the cooling drum 41. The discharged expanded beads are separated from the cooling liquid 42 and dried as necessary. Methods for separating the expanded beads from the cooling liquid 42 include, for example, conventionally known solid-liquid separation methods such as passing through a sieve.

[0115] (Expanded Thermoplastic Resin Bead Molded Article) The expanded thermoplastic resin bead molded article (expanded bead molded article) of this embodiment is obtained by expanding and fusing expanded beads together. Examples of expanded bead molded articles include parts for transportation equipment such as automobiles, railway vehicles, aircraft, and ships, cushioning materials and housings for electrical products, transport containers, packaging materials, structural members, and heat insulating materials. Examples of automobile parts include battery cases, battery trays, members used near the engine, exterior materials, and heat insulating materials. Examples of railway vehicle members include seat core materials, exterior materials, and heat insulating materials.

[0116] The size of the expanded bead molding is not particularly limited and is determined appropriately taking into consideration the intended use.

[0117] The ratio of the polyester resin to the thermoplastic resin of the expanded bead molding is the same as the ratio of the polyester resin to the thermoplastic resin of the expanded beads.The ratio of the polyimide resin to the thermoplastic resin of the expanded bead molding is the same as the ratio of the polyimide resin to the thermoplastic resin of the expanded beads.

[0118] The content of polyimide-based resin in the expanded bead molding can be measured by slicing the expanded bead molding from the surface along a direction perpendicular to the thickness direction (planar direction) to a desired thickness (e.g., 0.2 mm), using this as a measurement sample, in the same manner as the content of polyimide-based resin in the expanded beads.

[0119] The expanded bead molding exhibits a single glass transition temperature Tg. The compatibility of the polyester resin and the polyimide resin results in a single glass transition temperature Tg. The expanded bead molding has a single glass transition temperature Tg, which is higher than the glass transition temperature Tg of the polyester resin, thereby enhancing the heat resistance strength of the expanded bead molding. The glass transition temperature Tg of the expanded bead molding is, for example, preferably 80 to 130°C, more preferably 80 to 125°C, even more preferably 80 to 120°C, and particularly preferably 80 to 100°C. When Tg is equal to or greater than the lower limit, the heat resistance strength and dimensional stability under heat of the expanded bead molding can be further enhanced. When Tg is equal to or less than the upper limit, the moldability is improved and the appearance is beautifully finished.

[0120] The endothermic / heat-generating difference of the expanded bead molding is preferably 3.0 to 35 J / g, more preferably 10 to 30 J / g, and even more preferably 15 to 28 J / g. When the endothermic / heat-generating difference is equal to or greater than the lower limit, the crystallinity is increased, and the dimensional stability of the expanded bead molding upon heating can be improved. When the endothermic / heat-generating difference is equal to or less than the upper limit, the crystallinity is not too high, and the impact resistance of the expanded bead molding can be improved. The endothermic / heat-generating difference is the difference between the amount of endotherm and the amount of heat generated, as determined by heat flux differential scanning calorimetry at a heating rate of 10°C / min.

[0121] The Z-average molecular weight Mz of the expanded bead molding is 2.5 × 10 ５ ~5.0 x 10 ５ is 2.9 × 10 ５ ~5.0 x 10 ５ is preferred, and 3.2 × 10 ５ ~5.0 x 10 ５ When the Z-average molecular weight Mz of the expanded bead molding is equal to or greater than the lower limit, the open cell ratio can be further reduced, improving moldability. When the Z-average molecular weight Mz of the expanded bead molding is equal to or less than the upper limit, the expansion ratio can be further increased, and the expanded beads can be well thermally fused to each other, improving moldability.

[0122] The number average molecular weight Mn of the expanded bead molding is 0.10 × 10 ５ ~0.30 x 10 ５ is preferable, and 0.15 × 10 ５ ~0.25 x 10 ５More preferably, 0.18 × 10 ５ ~0.23 x 10 ５ When the number average molecular weight Mn of the expanded bead molding is equal to or greater than the above lower limit, the impact resistance can be improved. When the number average molecular weight Mn of the expanded bead molding is equal to or less than the above upper limit, the moldability can be further improved.

[0123] The mass average molecular weight Mw of the expanded bead molding is 0.50 × 10 ５ ~2.0 x 10 ５ is preferable, and 0.70 × 10 ５ ~1.5 x 10 ５ More preferably, 0.80 × 10 ５ ~1.2 × 10 ５ When the mass average molecular weight Mw of the expanded bead molding is equal to or greater than the above lower limit, the impact resistance can be improved. When the mass average molecular weight Mw of the expanded bead molding is equal to or less than the above upper limit, the moldability can be further improved.

[0124] The number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the expanded bead molding can be measured in the same manner as the number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the expanded beads. The number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the expanded bead molding can be adjusted by combining the types and amounts of the raw polyester resin and raw polyimide resin, as well as the type and amount of the crosslinking agent. The number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the expanded bead molding can be considered to be the same as the number-average molecular weight Mn, mass-average molecular weight Mw, and Z-average molecular weight Mz of the thermoplastic resin that constitutes the expanded bead molding.

[0125] The temperature at which the loss tangent tanδ of the expanded bead molding is maximized in solid viscoelasticity measurement at a heating rate of 5°C / min and a frequency of 1 Hz is preferably 120 to 230°C, more preferably 130 to 225°C, and even more preferably 150 to 220°C. If the temperature at which the loss tangent tanδ is maximized is equal to or greater than the above-mentioned lower limit, the temperature at which the expanded bead molding softens increases, thereby further improving the heat resistance strength of the expanded bead molding. If the temperature at which the loss tangent tanδ is maximized is equal to or less than the above-mentioned upper limit, the temperature at which the expanded bead molding softens does not become excessively high, thereby further improving moldability.

[0126] The open cell ratio of the expanded bead molding is, for example, preferably 20% or less, more preferably 18% or less, and even more preferably 16% or less. When the open cell ratio of the expanded bead molding is equal to or less than the above upper limit, the impact resistance of the expanded bead molding can be further improved. The open cell ratio of the expanded bead molding can be determined by the method described in JIS K7138:2006 "Rigid foam plastics - Determination of open cell ratio and closed cell ratio."

[0127] The apparent density of the expanded bead molding is, for example, 0.027 to 0.675 g / cm ３ is preferred, and 0.045 to 0.45 g / cm ３ More preferably, 0.0675 to 0.27 g / cm ３ When the apparent density of the expanded bead molding is equal to or greater than the above lower limit, the impact resistance of the expanded bead molding can be further improved. When the apparent density of the expanded bead molding is equal to or less than the above upper limit, the expanded bead molding can be made lighter.

[0128] The expansion ratio of the expanded bead molding is, for example, preferably 2 to 50, more preferably 3 to 30, and even more preferably 5 to 20. When the expansion ratio of the expanded bead molding is equal to or greater than the above lower limit, the impact resistance of the expanded bead molding can be further improved. When the expansion ratio of the expanded bead molding is equal to or less than the above upper limit, the mechanical strength of the expanded bead molding can be further improved.

[0129] The average cell diameter of the expanded bead molding is, for example, preferably 5.0 to 500 μm, more preferably 10 to 400 μm, and even more preferably 20 to 300 μm. When the average cell diameter of the expanded bead molding is equal to or greater than the above-mentioned lower limit, the impact resistance of the expanded bead molding can be further improved. When the average cell diameter of the expanded bead molding is equal to or less than the above-mentioned upper limit, the surface smoothness of the expanded bead molding can be further improved. The average cell diameter of the expanded bead molding can be measured in accordance with the method described in ASTM D2842-69.

[0130] The flame retardancy (UL94 flame retardancy grade) of the expanded bead moldings measured in accordance with the UL-94 vertical method (11 mm vertical flame test) is preferably V-2 or higher, more preferably V-1 or higher, and even more preferably V-0. The flame retardancy grade of the expanded bead moldings can be adjusted by adjusting the content of the polyimide resin and the content of the phosphorus-based flame retardant, for example. For example, by adjusting the content of the polyimide resin to 25 mass% or higher relative to the total mass of the thermoplastic resin, the flame retardancy can be further improved, more reliably achieving V-1 or higher. The UL94 flame retardancy grades increase in the order of V-2, V-1, and V-0. Examples of the UL-94 vertical method (11 mm vertical flame test) include the method described by Hosogai Aki et al., "Material Flammability Test for the Purpose of Fire Safety Evaluation," Journal of the Combustion Society of Japan, Vol. 56, No. 175, 2014, pp. 47-58.

[0131] <Manufacturing Method> Expanded bead molded articles using expanded beads can be manufactured by a conventionally known manufacturing method. Examples of manufacturing methods for expanded bead molded articles include the following: 1) A method in which expanded beads (bulk expansion ratio: 2 to 50 times) are filled into a mold, heated to cause secondary expansion of the expanded beads, which are fused together while forming secondary expanded beads, and then subjected to in-mold expansion molding to form an expanded bead molded article (expansion ratio: 2 to 50 times) (heat molding step). 2) A method in which expanded beads are heated to expand to a desired bulk expansion ratio to form pre-expanded beads (bulk expansion ratio: 2 to 50 times) (pre-expansion step), the pre-expanded beads are filled into a mold, heated to cause secondary expansion of the pre-expanded beads, which are fused together while forming secondary expanded beads, and then subjected to in-mold expansion molding to form an expanded bead molded article (expansion ratio: 2 to 50 times) (heat molding step).

[0132] Examples of methods for secondary expansion include heating the mold cavity with steam. The secondary expansion temperature is preferably 100 to 180°C. The secondary expansion time (i.e., the time for supplying steam to the mold) is preferably 5 to 120 seconds. During secondary expansion, steam may be supplied into the cavity from the female mold side, or from the male mold side, or these may be alternately performed. Furthermore, the secondary expansion power of the expanded beads may be improved by impregnating the expanded beads with an inert gas or air (hereinafter referred to as "inert gas" or the like) (internal pressure application step). Examples of inert gases include carbon dioxide, nitrogen, helium, and argon. Examples of methods for impregnating the expanded beads with an inert gas or the like include placing the expanded beads in an atmosphere of an inert gas or the like having a pressure equal to or higher than atmospheric pressure, thereby impregnating the expanded beads with the inert gas or the like. The expanded beads may be impregnated with an inert gas or the like before being filled into a mold, or may be impregnated by filling the expanded beads into a mold and then placing the mold together with the expanded beads in an atmosphere of an inert gas or the like. When the inert gas is nitrogen, the expanded beads may be left in a nitrogen atmosphere with a gauge pressure (based on atmospheric pressure) of 0.1 to 2 MPa for 20 minutes to 24 hours.

[0133] Following the heat molding step, the foamed bead molded article in the mold may be further heated to increase the crystallinity of the thermoplastic resin (heat retention step).

[0134] The expanded thermoplastic resin bead molded article of the present invention is suitable for, for example, electrical components and heat-resistant components for motorcycles, electric bicycles and automobiles, and is particularly suitable for use as internal components of hard disks, which require precision molding, and electrical components for motorcycles, electric bicycles and automobiles.

[0135] Examples of electrical components for motorcycles, electric bicycles, and automobiles include battery cases.

[0136] Suitable examples of heat-resistant parts for automobiles include alternator terminals, alternator connectors, IC regulators, light dimmer potentiometer bases, various valves such as exhaust gas valves, engine coolant joints, carburetor main bodies, carburetor spacers, exhaust gas sensors, coolant sensors, oil temperature sensors, brake pad wear sensors, throttle position sensors, crankshaft position sensors, air flow meters, brake pad wear sensors, air conditioner thermostat bases, heating hot air flow control valves, radiator motor brush holders, water pump impellers, turbine vanes, wiper motor-related parts, distributors, starter switches, starter relays, transmission wire harnesses, window washer nozzles, air conditioner panel switch boards, fuel-related electromagnetic valve coils, fuse connectors, horn terminals, electrical component insulating plates, step motor rotors, brake pistons, solenoid bobbins, ignition device cases, wheel caps, lamp sockets, lamp housings, lamp extensions, lamp reflectors, and the like.

[0137] (Foamed Resin Composite) A foamed resin composite comprises the foamed bead molding of the present invention and a fiber-reinforced resin layer (skin material) provided on at least a portion of the surface of the foamed bead molding. The foamed resin composite has excellent heat resistance and mechanical strength and can be used in a wide range of transportation equipment components. In addition, the foamed resin composite can also be suitably used as building materials, wind turbine blades, robot arms, electrical appliance housings, helmet cushioning, agricultural product boxes, transport containers such as thermal insulation containers, industrial helicopter rotor blades, and parts packaging materials. Examples of transportation equipment components include structural members that constitute the body of transportation equipment such as automobiles, railcars, aircraft, and ships. Examples of structural members that constitute the body of an automobile include door panels, door liner panels, bumpers, fenders, fender supports, engine covers, roof panels, trunk lids, floor panels, center tunnels, crash boxes, and cowls. For example, using a resin composite for a door panel that was previously made of steel plate provides substantially the same rigidity as a steel plate door panel while significantly reducing its weight, thereby contributing to weight reduction of the automobile. Examples of structural members that make up the main body of a railway vehicle include a back shell, a table, a leg rest, a wall panel, and a floor panel.

[0138] For example, a foamed resin composite 100 in FIG. 7 has a flat foamed bead molding (foam layer) 102 and fiber-reinforced resin layers 104 provided on both sides of the foamed bead molding 102 .

[0139] The foam layer 102 is the foamed bead molding of the present invention described above. The fibers constituting the fiber-reinforced resin layer 104 are not particularly limited and include, for example, carbon fiber, glass fiber, aramid fiber, boron fiber, and metal fiber. Among these, carbon fiber, glass fiber, and aramid fiber are preferred due to their excellent mechanical strength and heat resistance, with carbon fiber being more preferred. The form of the fibers is not particularly limited and includes, for example, woven fabrics, knitted fabrics, nonwoven fabrics, and face materials formed by bundling (sewing) fiber bundles (strands) of fibers aligned in one direction with a stitch thread such as a synthetic resin thread of polyamide resin or polyester resin, or a glass fiber thread. Examples of weaving methods for the fabric include plain weave, twill weave, and satin weave. The fibers may be (1) a multilayer face material formed by laminating multiple sheets of woven fabric, knitted fabric, or nonwoven fabric together or any combination thereof, or (2) a multilayer face material formed by bundling (stitching) multiple face materials formed by aligning fibers in one direction into fiber bundles (strands) with a stitch thread such as a synthetic resin thread of polyamide resin, polyester resin, or glass fiber thread, and then overlapping the multiple face materials so that the fiber directions of the fiber bundles are oriented in different directions, and integrating (stitching) the overlapped face materials with each other with a stitch thread such as a synthetic resin thread of polyamide resin, polyester resin, or glass fiber thread.

[0140] Resins contained in the fiber-reinforced resin layer 104 include uncured thermosetting resins and thermoplastic resins. Thermosetting resins are not particularly limited, and examples thereof include epoxy resins, unsaturated polyester resins, phenolic resins, melamine resins, polyurethane resins, silicone resins, maleimide resins, vinyl ester resins, cyanate ester resins, and resins obtained by prepolymerizing maleimide resins and cyanate ester resins. Epoxy resins and vinyl ester resins are preferred because of their excellent heat resistance, elastic modulus, and chemical resistance. Thermosetting resins may contain additives such as curing agents and curing accelerators. Thermosetting resins may be used alone or in combination. Thermoplastic resins are not particularly limited, and examples thereof include polyolefin-based resins such as polyethylene-based resins and polypropylene-based resins, acrylic-based resins, polyester-based resins, polyamide-based resins, and polycarbonate-based resins. The resin content of the fiber-reinforced resin layer 104 is preferably 20 to 70% by mass, and more preferably 30 to 60% by mass, relative to the total mass of the fiber-reinforced resin layer 104. If the resin content is equal to or greater than the lower limit, the bonding between the fibers is enhanced, and the mechanical strength of the resulting foamed resin composite is enhanced. If the resin content is equal to or less than the upper limit, the amount of resin present between the fibers is not too large, and the mechanical strength of the fiber-reinforced resin layer 104 is enhanced, and the mechanical strength of the resulting foamed resin composite is enhanced.

[0141] The method for impregnating the fibers with the resin is not particularly limited, and examples thereof include (1) a method of immersing the fibers in the resin, and (2) a method of coating the fibers with the resin.

[0142] In this embodiment, the materials of the fiber-reinforced resin layers located on both sides of the foamed bead molding may be the same or different.

[0143] The thickness of the fiber-reinforced resin layer 104 is, for example, preferably 0.10 to 5.0 mm, and more preferably 0.30 to 3.0 mm. If the thickness of the fiber-reinforced resin layer 104 is equal to or greater than the above-mentioned lower limit, the mechanical strength of the foamed resin composite 100 can be further increased. If the thickness of the fiber-reinforced resin layer 104 is equal to or less than the above-mentioned upper limit, the weight of the foamed resin composite 100 can be further reduced. In this embodiment, the thicknesses of the fiber-reinforced resin layers 104 located on both sides of the foamed bead molding 102 may be the same or different.

[0144] <Manufacturing Method> The method for providing the fiber-reinforced resin layer 104 on the surface of the expanded bead molding 102 is not particularly limited, and examples thereof include: (1) a method of laminating and bonding the fiber-reinforced resin layer 104 to the surface of the expanded bead molding 102 via an adhesive; (2) a method of laminating a fiber-reinforced resin layer 104 impregnated with a thermoplastic resin on the surface of the expanded bead molding 102 and bonding the fiber-reinforced resin layer 104 to the surface of the expanded bead molding 102 using the thermoplastic resin as a binder; and (3) a method of laminating the expanded bead molding 102 (4) a method in which a fiber-reinforced resin layer 104 impregnated with an uncured thermosetting resin is laminated on the surface of the foamed bead molding 102, and the fiber-reinforced resin layer 104 is bonded to the foamed bead molding 102 using a cured thermosetting resin as a binder; and (5) a method in which a fiber-reinforced resin layer 104 in a heated and softened state is laminated on the surface of the foamed bead molding 102, and the fiber-reinforced resin layer 104 is pressed against the surface of the foamed bead molding 102, thereby bonding the fiber-reinforced resin layer 104 to the foamed bead molding 102. In method (4), the fiber-reinforced resin layer 104 can also be deformed to conform to the surface of the foamed bead molding 102. Here, since the foamed bead molding 102 of the present invention has excellent load-bearing capacity in high-temperature environments, method (4) can also be preferably used. These methods allow the fiber-reinforced resin layer 104 to be integrally formed on the surface of the foamed bead molding 102. Examples of methods for joining the fiber-reinforced resin layer 104 to the surface of the expanded bead molding 102 include an autoclave method, a hand lay-up method, a spray-up method, a PCM (Prepreg Compression Molding) method, an RTM (Resin Transfer Molding) method, and a VaRTM (Vacuum assisted Resin Transfer Molding) method.

[0145] Although the foamed resin composite of the above-described embodiment has a flat expanded bead molding, the present invention is not limited thereto, and the shape of the expanded bead molding can be appropriately determined depending on the application. That is, the shape of the foamed resin composite can be appropriately determined depending on the application. In the above-described embodiment, a fiber-reinforced resin layer is provided on both sides of the expanded bead molding, but the present invention is not limited thereto, and a fiber-reinforced resin layer may be provided on only one side of the expanded bead molding, or a fiber-reinforced resin layer may be provided on only a portion of the surface of the expanded bead molding.

[0146] The expanded bead molding of this embodiment contains a polyester-based resin, which improves dimensional stability under heating and enhances heat resistance. The expanded beads of this embodiment contain a polyimide-based resin, which increases the glass transition temperature Tg and enhances heat resistance strength. Therefore, the expanded bead molding obtained by heat molding the expanded beads has excellent heat resistance strength. In addition, the expanded bead molding of this embodiment has a polyimide-based resin content within a specific range, which improves heat resistance strength and provides excellent moldability. Furthermore, the expanded bead molding of this embodiment contains a specific amount of phosphorus-based flame retardant, which provides excellent flame retardancy and moldability.

[0147] In one preferred embodiment of the expanded thermoplastic resin beads or expanded thermoplastic resin bead molded article of the present invention, the content of the polyimide resin is 30 to 40% by mass, based on the total mass of the thermoplastic resin, the content of the phosphorus is 0.30 to 0.66% by mass, based on the total mass of the thermoplastic resin, and the crystallinity of the expanded thermoplastic resin beads is 3.3 to 6.3%. In this embodiment, it is even more preferable that the open cell ratio of the expanded thermoplastic resin beads is 3.4 to 16%. According to the above embodiment, particularly excellent moldability, thermal dimensional change rate, flammability test results, and flame retardancy can be achieved.

[0148] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0149] (Raw materials used) <Polyester resin> PET (A): manufactured by Lotte Chemical Co., Ltd., trade name "BCB80", glass transition temperature Tg: 78.7°C, melting point: 247.2°C, IV value: 0.80, biomass ratio: 30%. PET (B): manufactured by Mitsui Chemicals, Inc., trade name "SA-135", glass transition temperature Tg: 75.0°C, melting point: 247.0°C, IV value: 0.82, biomass ratio: 0%.

[0150] <Polyimide Resin> PEI (A): Polyetherimide, manufactured by SABIC Innovative Plastics, trade name "Ultem 1000", glass transition temperature Tg: 217°C, MFR: 9 g / 10 min.

[0151] <Phosphorus-based flame retardants> Flame retardant (a): PET masterbatch containing flame retardant, manufactured by Toyocolor Co., Ltd., trade name "NF POLY 1450 MB", phosphorus content: 4.4% by mass. Flame retardant (b): PET masterbatch containing flame retardant, manufactured by Toyocolor Co., Ltd., trade name "NF POLY 1477 MB", phosphorus content: 3.0% by mass. Flame retardant (c): Flame retardant, manufactured by Teijin Limited, trade name "Fireguard FCX-210", phosphorus content: 15% by mass.

[0152] <Talc Masterbatch> Nucleating agent MB: A masterbatch consisting of PET = 58 mass % and talc = 42 mass %.

[0153] <Crosslinking agent> PMDA: pyromellitic anhydride.

[0154] <Blowing agent> Butane: a mixture of isobutane and normal butane, where the ratio of isobutane to normal butane is 35:65 (mass ratio).

[0155] (Evaluation Method) <Density> <Bulk Density of Expanded Beads> The bulk density of the expanded beads was measured in accordance with JIS K6911:1995 "General Testing Methods for Thermosetting Plastics." Measurement was performed using an apparent density measuring instrument in accordance with JIS K6911, and the bulk density of the expanded beads was calculated based on the following formula (s1). The bulk density (g / cm) of the expanded beads was ３ ) = [mass of the measuring cylinder containing the foam particles (g) - mass of the measuring cylinder (g)] / [capacity of the measuring cylinder (cm ３ ) )] ... (s1)

[0156] <Density of Expanded Bead Molding> The density of the expanded bead molding was measured by the method described in JIS K7222:1999 "Foamed plastics and rubber - Measurement of apparent density". ３ The expanded bead moldings were cut without changing the original cell structure of the material, and the masses were measured. The densities were calculated using the following formula (s2). Density (g / cm ３ ) = Mass of expanded bead molding (g) / Volume of expanded bead molding (cm ３ ) ... (s2)

[0157] <Expansion Ratio> <Expanded Beads> The bulk expansion ratio of the expanded beads was determined by calculating the density of the thermoplastic resin from the blending ratio of each example and dividing the density of the thermoplastic resin by the bulk density of the expanded beads. The following values ​​were used for the density of each resin: PET: 1.35 g / cm ３ . ・PEI: 1.28g / cm ３ . Flame retardant MB: 1.35 g / cm ３ .

[0158] <<Expanded Bead Molded Article>> The expansion ratio of the expanded bead molded article was determined by calculating the density of the thermoplastic resin from the blending ratio of each example and dividing the density of the thermoplastic resin by the density of the expanded bead molded article obtained. The following values ​​were used for the density of each resin: PET: 1.35 g / cm ３ . ・PEI: 1.28g / cm ３ . Flame retardant MB: 1.35 g / cm ３ .

[0159] <Open Cell Ratio> The open cell ratio of the expanded beads was measured by the following method. First, a sample cup of a volumetric air comparison type hydrometer was prepared, and the total mass A (g) of the expanded beads was measured to fill about 80% of the sample cup. Next, the total volume B (cm ３) was measured using a hydrometer by the 1-1 / 2-1 atmosphere method. For the measurement, a "Volumetric Air Comparison Hydrometer Model 1000" manufactured by Tokyo Science Co., Ltd. was used. A wire mesh container was prepared, and the wire mesh container was immersed in water, and the mass C (g) of the wire mesh container in the immersed state was measured. All the expanded beads were placed in the wire mesh container, and the wire mesh container was immersed in water, and the combined mass D (g) of the wire mesh container in the immersed state and the total amount of expanded beads placed in the wire mesh container was measured. For the mass measurement of the expanded beads and the wire mesh container, an "Electronic Balance HB3000" (minimum scale 0.01 g) manufactured by Yamato Seisei Co., Ltd. was used. The apparent volume E (cm) of the expanded beads was calculated based on the following formula: ３ ) is calculated, and the apparent volume E and the total volume B (cm ３ The open cell ratio of the expanded beads was calculated by the following formula (s3) based on the volume of 1 g of water to 1 cm ３ In this measurement, the expanded particles were stored for 16 hours in an environment conforming to JIS K7100-1999, symbol 23 / 50, grade 2, and then the measurement was carried out in the same environment. Open cell ratio (%) = 100 × (E - B) / E (s3) (E = A + (C - D))

[0160] <Glass Transition Temperature Tg> The glass transition temperature Tg was measured according to the method described in JIS K7121:1987 and JIS K7121:2012. However, the sampling method and temperature conditions were as follows. A sample cut out from the expanded beads or the expanded bead molded article was packed into the bottom of an aluminum measurement container in an amount of 5.5±0.5 mg without leaving any gaps, and then the container was covered with an aluminum lid. Next, differential scanning calorimetry was performed using a Hitachi High-Tech Science DSC7000X, AS-3 differential scanning calorimeter. The sample was heated and cooled under a nitrogen gas flow rate of 20 mL / min according to the following steps 1 to 4 to obtain a DSC curve. (Step 1) The sample was held at 30°C for 2 minutes. (Step 2) The temperature was increased from 30°C to 300°C at a rate of 10°C / min (first heating step), and held for 10 minutes. (Step 3) The sample was quickly removed and allowed to cool in an environment of 25±10°C. (Step 4) The temperature was raised from 30°C to 300°C at a rate of 10°C / min (second heating process). Alumina was used as the reference material. Using the analysis software provided with the instrument, the temperatures at the top of the melting peak and crystallization peak observed during the second heating process were read and used as the melting point and crystallization temperature. The glass transition temperature Tg was calculated from the DSC curve observed during the second heating process using the analysis software provided with the instrument. This midpoint glass transition temperature was determined according to the standard (9.3). The glass transition temperature Tg was determined as the glass transition temperature Tg on the lower side of the crystallization peak observed during the second heating process in the heat flux differential scanning calorimetry chart (DSC curve) at a heating rate of 10°C / min. However, when no crystallization peak was observed in the second heating process, the glass transition temperature Tg in the temperature range (30 to 300° C.) in the second heating process was adopted.

[0161] <Endotherm (a), Heat Release (b), Crystallinity> The endotherm (a) (heat of fusion) and heat release (b) (heat of crystallization) were measured according to the methods described in JIS K7121:1987 and JIS K7121:2012. However, the sampling method and temperature conditions were as follows. A sample cut out from the expanded beads or the expanded bead molded article was packed into the bottom of an aluminum measurement container in an amount of 5.5±0.5 mg without leaving any gaps, and then the container was 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 and cooled under a nitrogen gas flow rate of 20 mL / min according to the following steps 1 and 2 to obtain a DSC curve. (Step 1) Hold at 30°C for 2 minutes. (Step 2) Heat from 30°C to 300°C at a rate of 10°C / min (first heating step). Alumina was used as the reference material. The endothermic value (a) and the calorific value (b) were calculated using the analysis software provided with the instrument. Specifically, as shown in Figure 4, the endothermic value (a) was calculated from the area enclosed by the line connecting the point where the DSC curve deviates from the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline, as well as the area of ​​the DSC curve. The calorific value (b) was calculated from the area enclosed by the line connecting the point where the DSC curve deviates from the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline, as well as the area of ​​the DSC curve. The crystallinity is determined by the following method. First, the difference between the endothermic value (a) and the calorific value (b) is calculated. The crystallinity is determined by dividing this difference by the theoretical heat of fusion of perfectly crystalline polyethylene terephthalate, 140.1 J / g. Crystallinity (%) = (endothermic amount (a) (J / g) - calorific value (b) (J / g)) / 140.1 (J / g) x 100... (s4)

[0162] <Phosphorus Content> The phosphorus content of the expanded beads or expanded bead molded products was determined by an order analysis method of X-ray fluorescence analysis. Phosphorus intensity was measured under the following conditions using a "ZSX Primus IV" X-ray fluorescence analyzer manufactured by Rigaku Corporation, and the phosphorus content relative to the total mass of the thermoplastic resin was determined by order analysis. Approximately 0.5 g of the measurement target was formed into a thin film using a heat press molding machine, and the film was placed in a 30 mm diameter sample case attached to the device to prepare a measurement sample.

[0163] <<Apparatus conditions>> Apparatus: ZSX Primus IV. X-ray tube target: Rh. Measurement diameter: 30 mm. Spin: None. Atmosphere: Vacuum. Sample form: Metal. Balance component: C ３０ H ２３ O ８ N. - Sample film: None. - Sample weight and thickness: Set <Qualitative element conditions> - P-Kα. - Tube: Rh (30 kV-100 mA). - Filter: Be30. - Attenuator: 1 / 1. - Slit: S4. - Analyzing crystal: GeH. - 2θ: 141.2 deg (measurement range: 137 to 144 deg). - Detector: PC. - PHA: 150 to 300. - Step: 0.05 deg. - Time: 0.15 sec.

[0164] <Flame Retardance> Flame retardance was measured in accordance with the method described in the vertical flame test (V) in UL94:1996. Foamed beads were molded into foamed molded articles measuring 300 mm length x 400 mm width x 11 mm height, and test pieces measuring 125 mm length x 13 mm width x 11 mm thickness (with a skin layer only in the thickness direction) were cut out from the molded articles and used for measurement. The test pieces were conditioned under the conditions of ASTM D618 before use. Measurements were performed in an environment with a temperature of 10 to 35°C and a humidity of 45 to 75%, and flame retardance was evaluated according to the vertical flame test (V) described in UL94:1996.

[0165] <Evaluation criteria> A: The result of the combustion test is V-0. B: The result of the combustion test is V-1. C: The result of the combustion test is V-2. D: The result of the combustion test is not V-0 to V-2 (non-compliant).

[0166] <Dimensional Change Upon Heat (Heat Resistance)> The dimensional change upon heat of the expanded bead molding was measured using Method B described in JIS K6767:1999 "Foamed Plastics - Polyethylene - Test Methods." Test specimens having a square shape with sides of 150 mm and a thickness equal to that of the expanded bead molding were cut from the expanded bead molding. Three parallel 100 mm lines were drawn at 50 mm intervals in the longitudinal and transverse directions of the center of the test specimen. The lengths of the three lines in each of the longitudinal and transverse directions were measured, and the arithmetic mean value L0 of these was taken as the initial dimension. The test specimen was then subjected to a heating test by placing it in a hot air circulation dryer set at 180°C for 168 hours. After the heating test, the test specimen was removed and left at 25°C for 1 hour. The lengths of the three lines drawn on the surface of the test specimen in each of the longitudinal and transverse directions were measured, and the arithmetic mean value L1 of these was taken as the post-heat dimension. The dimensional change upon heat was calculated using the following formula (s5): Dimensional change rate upon heating (%)=100×|(L1−L0)| / L0 (s5) The dimensional change rate upon heating of the foamed bead moldings measured at each set temperature was evaluated according to the following criteria.

[0167] <Evaluation Criteria> A: The rate of dimensional change upon heating is less than 1.0%. B: The rate of dimensional change upon heating is 1.0% or more and less than 2.0%. C: The rate of dimensional change upon heating is 2.0% or more.

[0168] <Moldability> The surface of the expanded bead molding was visually inspected and evaluated according to the following criteria.

[0169] <Evaluation Criteria> A: No gaps between the expanded beads, the surface of the molded article is very smooth, and the appearance of the molded article is very good. B: There are very few gaps between the expanded beads, the surface of the molded article is almost smooth, and the appearance of the molded article is good. C: There are few gaps between the expanded beads, and there are small irregularities on the surface of the molded article, and the appearance of the molded article is somewhat poor. D: There are many gaps between the expanded beads, and there are large irregularities on the surface of the molded article, or obvious shrinkage is observed during molding, and the appearance of the molded article is significantly poor.

[0170] <Overall Evaluation> The evaluation results of moldability, dimensional change rate upon heating, combustion test, and flame retardancy were classified according to the following evaluation criteria.

[0171] <Evaluation Criteria> A: The rating was "A" in all evaluations. B: The rating was "A" or "B" in all evaluations, with at least one rating being "B". C: The rating was "A", "B", or "C" in all evaluations, with at least one rating being "C". D: At least one rating was "D" in all evaluations.

[0172] Example 1: Expanded beads were produced using a manufacturing apparatus similar to the expanded bead manufacturing apparatus 10 shown in Figures 4 to 6 according to the following procedure. First, a polyester resin, a polyimide resin, a phosphorus-based flame retardant, a talc masterbatch, and a crosslinking agent were fed into a single-screw extruder with a cylinder diameter D of 65 mm and an L (cylinder length) / D (cylinder diameter) ratio of 34 according to the formulation shown in the table, and the mixture was melt-kneaded at 290°C. Next, butane (isobutane:normal butane = 35:65 (mass ratio)) as a blowing agent was injected into the molten mixture midway through the extruder in the amount shown in the table, and uniformly dispersed throughout the molten mixture to produce a resin composition. The molten resin composition was then heated to 300°C at the front end of the extruder, and the resin composition was extruded and foamed through each nozzle of a multi-nozzle nozzle mold 1 attached to the front end of the extruder. The extrusion rate of the resin composition was 36 kg / h. The nozzle die 1 had 50 nozzles, each with an outlet portion 11 having a diameter of 0.8 mm, and all of the outlet portions 11 were positioned at equal intervals on an imaginary circle A having a diameter of 139.5 mm. Two rotary blades 5 were integrally provided on the outer circumferential 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, and each rotary blade 5 was configured to move on the imaginary circle A while always in contact with the front end surface 1 a of the nozzle die 1.

[0173] The cooling member 4 was equipped with a cooling drum 41, which consisted of a circular front portion 41a and a cylindrical peripheral wall portion 41b extending rearward from the outer periphery of the front portion 41a and having an inner diameter of 320 mm. A cooling liquid 42 at 20°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. ３The cooling liquid 42 proceeded 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 liquid 42 was supplied from the supply pipe 41d to the inner circumferential surface of the circumferential wall 41b of the cooling drum 41. As the cooling liquid 42 proceeded along the inner circumferential surface of the circumferential wall 41b, the cooling liquid 42 gradually spread in a direction perpendicular to the direction of advancement, and completely covered the inner circumferential surface of the circumferential wall 41b forward of the supply port 41c of the cooling drum 41.

[0174] The rotary blade 5 disposed on the front end surface 1a was rotated at 3,400 rpm, and the extruded foam extruded and foamed from the outlet 11 of each nozzle of the nozzle mold 1 was cut by the rotary blade 5 to produce approximately spherical cut particles. The extruded foam consisted of an unfoamed portion immediately after extrusion from the nozzle of the nozzle mold 1 and a foamed portion in the process of foaming that was continuous with the unfoamed portion. The extruded foam was cut at the open end of the nozzle outlet 11, and the cutting of the extruded foam took place in the unfoamed portion. In producing the expanded beads described above, the rotary blade 2 was first removed from the nozzle mold 1 and the cooling member 4 was retracted from the nozzle mold 1. In this state, the resin composition was extruded and foamed from the extruder to produce an extruded foam, and it was confirmed that the extruded foam consisted of an unfoamed portion immediately after extrusion from the nozzle of the nozzle mold 1 and a foamed portion in the process of foaming that was continuous with the unfoamed portion. Next, after attaching the rotating shaft 2 to the nozzle mold 1 and arranging the cooling member 4 in a predetermined position, the rotating shaft 2 was rotated and the extruded foam was cut with the rotating blade 5 at the open end of the nozzle outlet portion 11 to produce particulate cut material.

[0175] The particulate cut material was thrown outward or forward by the cutting stress of the rotary blade 5, and collided with the cooling liquid 42 flowing along the inner surface of the cooling drum 41 of the cooling member 4 from a direction oblique to the surface of the cooling liquid 42, so as to follow the cooling liquid 42 from the upstream side to the downstream side of the flow of the cooling liquid 42, and the particulate cut material entered the cooling liquid 42 and was immediately cooled, thereby producing foamed beads. The obtained foamed beads were discharged together with the cooling liquid 42 through the discharge port 41e of the cooling drum 41, and then separated from the cooling liquid 42 in a dehydrator.

[0176] An in-mold foam molding machine equipped with molds (male and female molds) was prepared. Two types of molds were used depending on the evaluation items. The two types of molds were mold A, in which a rectangular parallelepiped cavity with internal dimensions of 300 mm length x 400 mm width x 30 mm height was formed between the male and female molds when the male and female molds were clamped, and mold B, in which a rectangular parallelepiped cavity with internal dimensions of 300 mm length x 400 mm width x 11 mm was formed. For mold A, the mold was filled with foamed particles with a mold crack of 3 mm. For mold B, the mold was filled with foamed particles with a mold crack of 1 mm. After filling the mold with the expanded beads, steam was introduced into the cavity from the female mold for 60 seconds to a gauge pressure of 0.30 MPa (one-sided heating), then steam was introduced into the cavity from the male mold for 45 seconds to a gauge pressure of 0.30 MPa (reverse one-sided heating), and then steam was supplied from both the male and female molds for 60 seconds to a gauge pressure of 0.33 MPa (double-sided heating). This heated the expanded beads, causing secondary expansion and heat fusing the secondary expanded beads together to form a single unit. The introduction of steam into the cavity was then stopped, and the process was maintained for 110 seconds (heat retention step). Finally, a cooling liquid was supplied into the cavity to cool the expanded bead molding in the mold, and the cavity was opened to remove the expanded bead molding. The expanded bead moldings molded with mold A were evaluated for moldability and thermal dimensional change. The expanded bead moldings molded with mold B were evaluated for flammability and flame retardancy. A comprehensive evaluation was conducted based on these results, and the results are shown in the table.

[0177] (Examples 2 to 20, Comparative Examples 1 to 4) Expanded beads and expanded bead molded articles were produced in the same manner as in Example 1, except that the polyester resin, polyimide resin, talc masterbatch, phosphorus-based flame retardant, crosslinking agent, and blowing agent were used in the formulations shown in the tables, and the molding conditions shown in Tables 2 to 7 were used. The resulting expanded beads and expanded bead molded articles were subjected to moldability, thermal dimensional change, combustion test, flame retardancy evaluation, and overall evaluation, and the results are shown in the tables. Note that in Comparative Examples 3 and 4, the moldability was rated "D," and expanded bead molded articles suitable for evaluation could not be obtained, so the thermal dimensional change, combustion test, and flame retardancy evaluation were not performed.

[0178]

[0179]

[0180]

[0181]

[0182]

[0183]

[0184] Examples 1 to 20, to which the present invention was applied, achieved combustion test results of V-0 to V-2 and overall ratings of "A" to "C." Comparative Examples 1 and 2, which did not contain a phosphorus-based flame retardant, failed the combustion test and were rated "D" for flame retardancy. Comparative Example 3, in which the phosphorus content was 1.32% by mass, and Comparative Example 4, in which the polyimide resin content relative to the total mass of the thermoplastic resin was 50% by mass, achieved moldability of "D." These results confirm that the application of the present invention can improve flame retardancy and heat resistance, and also improve the moldability of expanded bead moldings.

[0185] The expanded thermoplastic resin particles obtained in Examples 1, 3, and 6 were measured for the content of polyimide resin relative to the total mass of the thermoplastic resin by the method described above in "Method for measuring the content of polyimide resin." The results are shown in Table 8.

[0186]

[0187] 100: Foamed resin composite 102: Foamed bead molding 104: Fiber reinforced resin layer

Claims

1. Contains a thermoplastic resin, the thermoplastic resin includes a polyester-based resin, a polyimide-based resin, and a phosphorus-based flame retardant; The content of the polyimide resin is 5 to 45% by mass relative to the total mass of the thermoplastic resin, The expanded thermoplastic resin particles have a phosphorus content of 0.15 to 1.00 mass % relative to the total mass of the thermoplastic resin.

2. The expanded thermoplastic resin particles according to claim 1, wherein the content of the polyimide resin is 25 to 45 mass % based on the total mass of the thermoplastic resin.

3. The expanded thermoplastic resin particles according to claim 1 or 2, which have a glass transition temperature Tg of 80 to 130°C.

4. Two or more thermoplastic resin foam particles are thermally fused to each other, Contains a thermoplastic resin, the thermoplastic resin includes a polyester-based resin, a polyimide-based resin, and a phosphorus-based flame retardant; The content of the polyimide resin is 5 to 45% by mass relative to the total mass of the thermoplastic resin, The expanded thermoplastic resin bead molding has a phosphorus content of 0.15 to 1.00 mass % relative to the total mass of the thermoplastic resin.

5. The thermoplastic resin foamed bead molding according to claim 4, wherein the flame retardancy measured in accordance with the UL-94 vertical method (11 mm vertical flame test) of the UL standard is V-0, V-1 or V-2.

6. The expanded thermoplastic resin bead molding according to claim 4, wherein the content of the polyimide resin is 25 to 45 mass % based on the total mass of the thermoplastic resin.

7. The thermoplastic resin foamed bead molding according to claim 6, wherein the flame retardancy measured in accordance with the UL-94 vertical method (11 mm vertical flame test) of the UL standard is V-0 or V-1.

8. The foamed thermoplastic resin bead molding according to any one of claims 4 to 7, wherein the glass transition temperature Tg is 80 to 130°C.

9. A foamed resin composite comprising the thermoplastic resin foamed bead molding according to any one of claims 4 to 7, and a fiber-reinforced resin layer provided on at least a part of the surface of the thermoplastic resin foamed bead molding.

10. The method includes a step of extruding a thermoplastic resin composition containing a thermoplastic resin and a foaming agent, and foaming the composition to obtain foamed thermoplastic resin particles, the thermoplastic resin includes a polyester-based resin, a polyimide-based resin, and a phosphorus-based flame retardant; The content of the polyimide resin is 5 to 45% by mass relative to the total mass of the thermoplastic resin, The method for producing expanded thermoplastic resin particles, wherein the phosphorus content is 0.15 to 1.00 mass% based on the total mass of the thermoplastic resin.

11. The method for producing expanded thermoplastic resin beads according to claim 10, wherein the content of the polyimide resin is 25 to 45 mass% based on the total mass of the thermoplastic resin.

12. 12. A method for producing a thermoplastic resin foamed bead molding, comprising the steps of: obtaining the thermoplastic resin foamed beads by the method for producing thermoplastic resin foamed beads according to claim 10 or 11; filling the obtained thermoplastic resin foamed beads into a cavity of a mold; heating the thermoplastic resin foamed beads in the cavity to form secondary foamed beads; and heat-fusing the secondary foamed beads together to obtain a thermoplastic resin foamed bead molding.

13. A battery case or a battery case comprising the expanded thermoplastic resin bead molding according to any one of claims 4 to 7.