JP7524018B2 - Thermoplastic resin expanded beads, thermoplastic resin expanded bead molded product, expanded resin composite, method for producing thermoplastic resin expanded beads, and method for producing thermoplastic resin expanded bead molded product - Google Patents

Description

The present invention relates to thermoplastic resin foamed beads, a thermoplastic resin foamed bead molded product, a foamed resin composite, a method for producing thermoplastic resin foamed beads, and a method for producing a thermoplastic resin foamed bead molded product.

Molded articles (expanded thermoplastic resin bead molded articles) made of expanded beads containing a thermoplastic resin (expanded thermoplastic resin beads) are lightweight and have excellent heat insulating properties, shock absorbing properties, and mechanical strength. For this reason, applications of expanded thermoplastic resin bead molded articles (sometimes simply referred to as "expanded thermoplastic resin bead molded articles") to automobiles, aircraft, railway vehicles, etc. have been considered.
Among thermoplastic resins, polyester-based resins such as polyethylene terephthalate (PET) can be used to produce expanded bead moldings having excellent rigidity and heat resistance, and therefore, studies on expanded bead moldings using polyester-based resins are being conducted.

One method for producing expanded bead moldings is in-mold foam molding. Here, we will explain in-mold foam molding. Thermoplastic resin expanded beads (sometimes simply called "expanded beads") are filled into the cavity of a mold. The expanded beads in the cavity are heated and expanded with a heating medium such as hot water or steam to form secondary expanded beads, while the expansion pressure of the expanded beads causes the secondary expanded beads to be thermally fused together to obtain an expanded bead molding of the desired shape.

For example, Patent Document 1 discloses a method for producing a foamed bead molding in which a mold is filled with pre-foamed beads of polyethylene terephthalate (PET) with a low degree of crystallinity, the mold surface is heated to a temperature higher than the glass transition temperature Tg of PET to perform in-mold foam molding, and then the mold surface is cooled for a predetermined time so that the temperature does not become lower than the glass transition temperature Tg. According to the invention of Patent Document 1, after the heating for in-mold foam molding is completed, the molded body is not removed from the mold, but is cooled so that the surface temperature of the mold does not become lower than Tg, thereby promoting crystallization of the foamed bead molding and improving the heating dimensional stability. However, the invention of Patent Document 1 has a problem in that the molding time is long because a cooling process is required to promote crystallization. Note that "heating dimensional stability" means a property that is unlikely to cause elongation or shrinkage when the temperature of the foamed bead molding is increased.

In response to these problems, Patent Document 2 proposes a method for producing expanded beads that contains a specific ratio of crystalline polyester resin and amorphous polyester resin with a specific glass transition temperature Tg. According to the invention of Patent Document 2, since it contains an amorphous thermoplastic polyester resin that has a higher glass transition temperature Tg than the crystalline polyester resin, the expanded bead molding obtained by in-mold expansion molding using the expanded thermoplastic polyester resin beads has excellent heating dimensional stability without requiring a process for increasing the crystallinity.

International Publication No. 2000/035650 JP 2014-070153 A

However, although the invention of Patent Document 2 has excellent dimensional stability when heated, it becomes soft and weak when heated (it has low heat resistance), and therefore there is a risk of its rigidity decreasing as the temperature increases.
Therefore, an object of the present invention is to provide expanded thermoplastic resin beads having excellent heat resistant strength.

As a result of intensive research, the inventors discovered that a mixture of crystalline polyester resin and amorphous polyester resin is not sufficiently compatible with each other, and therefore softens and deforms when it reaches the glass transition temperature of the lower of the two polyester resins. Based on this knowledge, they discovered that the heat resistance can be increased by incorporating two highly compatible resins, and thus completed the present invention.

That is, the present invention has the following aspects.
＜1＞
Contains a thermoplastic resin,
The thermoplastic resin includes a polyester resin and a polyimide resin,
The thermoplastic resin foam particles have a single glass transition temperature Tg.
＜2＞
The thermoplastic resin expanded particles according to <1>, wherein the glass transition temperature Tg is 80 to 130° C.
＜3＞
The thermoplastic resin expanded beads according to <1> or <2>, wherein the absolute value of the difference between the endothermic amount and the exothermic amount determined by heat flux differential scanning calorimetry at a heating rate of 10° C./min is 3 to 35 J/g.
＜4＞
The content ratio of the polyester resin to the total mass of the thermoplastic resin is 40 to 95 mass %,
The content ratio of the polyimide resin to the total mass of the thermoplastic resin is 5 to 60 mass%.
<1> to <3>,
＜5＞
The expanded thermoplastic resin particles according to any one of <1> to <4>, wherein the temperature at which the loss tangent tan δ is maximized in solid viscoelasticity measurement at a heating rate of 5° C./min and a frequency of 1 Hz is 120 to 230° C.
＜6＞
The expanded thermoplastic resin particles according to any one of <1> to <5>, wherein the polyimide-based resin is a polyetherimide-based resin.
＜７＞
The thermoplastic resin expanded particles according to any one of <1> to <6>, wherein the polyester-based resin contains a plant-derived polyester-based resin.
＜8＞
The thermoplastic resin expanded particles according to any one of <1> to <7>, wherein the thermoplastic resin contains recycled materials.

＜9＞
The method for producing expanded thermoplastic resin particles according to any one of <1> to <8>, further comprising a step of extruding a thermoplastic resin composition containing the thermoplastic resin and a foaming agent, and foaming the composition to obtain expanded thermoplastic resin particles.
＜10＞
The method for producing expanded thermoplastic resin particles according to <9>, wherein the thermoplastic resin composition further contains a crosslinking agent.

<11>
Contains a thermoplastic resin,
The thermoplastic resin includes a polyester resin and a polyimide resin,
A foamed thermoplastic resin bead molding having a single glass transition temperature Tg.
＜12＞
The thermoplastic resin foamed bead molding according to <11>, wherein the glass transition temperature Tg is 80 to 130° C. or less.
＜13＞
The absolute value of the difference between the endothermic amount and the exothermic amount measured by heat flux differential scanning calorimetry at a heating rate of 10 ° C. / min is 3 to 35 J / g.
＜14＞
The content ratio of the polyester resin to the total mass of the thermoplastic resin is 40 to 95 mass %,
The content ratio of the polyimide resin to the total mass of the thermoplastic resin is 5 to 60 mass%.
<11> to <13>,
＜15＞
<11> to <14>, wherein the temperature at which the loss tangent tan δ is maximized in solid viscoelasticity measurement at a heating rate of 5° C./min and a frequency of 1 Hz is 120 to 230° C. The expanded thermoplastic resin bead molding according to any one of <11> to <14>.
＜16＞
The expanded thermoplastic resin bead molding according to any one of <11> to <15>, wherein the polyimide-based resin is a polyetherimide-based resin.
＜１７＞
The thermoplastic resin foamed bead molding according to any one of <11> to <16>, wherein the polyester-based resin contains a plant-derived polyester-based resin.
＜18＞
The thermoplastic resin foamed bead molding according to any one of <11> to <17>, wherein the thermoplastic resin contains recycled materials.

＜19＞
11. 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 9 or 10; 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.

＜20＞
<11> to <18>. A foamed resin composite comprising: an expanded thermoplastic resin bead molding according to any one of <11> to <18>; and a fiber-reinforced resin layer provided on at least a part of a surface of the expanded thermoplastic resin bead molding.

The thermoplastic resin foam particles of the present invention can improve heat resistance.

FIG. 1 is a flow diagram showing an example of a production process for a plant-derived polyester resin. FIG. 1 is a flow diagram showing an example of a production process for a plant-derived polyester resin. FIG. 1 is a flow diagram showing an example of a production process for a plant-derived polyester resin. 1 is a schematic side cross-sectional view showing an example of an apparatus for producing expanded thermoplastic resin beads of the present invention. 1 is a front view showing an example of an apparatus for producing expanded thermoplastic resin beads of the present invention. FIG. 1 is a front view showing an example of an apparatus for producing expanded thermoplastic resin beads of the present invention. FIG. 1 is a cross-sectional view of a foamed resin composite body according to one embodiment of the present invention. 1 is a DSC curve of the expanded beads of Example 3. 13 is a graph showing the measurement results of loss tangent tan δ in Example 3. 1 is a graph showing the measurement results of loss tangent tan δ in Comparative Example 1.

In this document, "~" indicates a range that includes both ends as the lower and upper limits.

(Thermoplastic resin expanded particles)
The expanded thermoplastic resin particles (expanded particles) of the present invention contain a thermoplastic resin. The expanded particles 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 thermoplastic resin expanded bead moldings (expanded bead moldings) that are molded by so-called in-mold foam molding.

<Thermoplastic resin>
The thermoplastic resin of the expanded beads contains a polyester resin and a polyimide resin. The expanded beads of the present invention contain both a polyester resin and a polyimide resin, and thus the heat resistance strength of the expanded beads molding can be increased.

<Polyester resin>
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), a copolymer of terephthalic acid, ethylene glycol, and cyclohexane dimethanol, and mixtures thereof. As the polyester-based resin, 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 resin may be a polyester resin derived from a petrochemical product, a plant-derived polyester resin such as so-called bio-PET, or a mixture of these.
Examples of plant-derived polyester resins include polyethylene terephthalate resins, plant-derived polyethylene furanoate resins, and plant-derived polytrimethylene terephthalate resins.
The polyester resin may be made from recycled materials.
These polyester resins may be used alone or in combination of two or more.

Hereinafter, the plant-derived polyester resin will be described.
Plant-derived polyester resins are polymers derived from plant materials such as sugar cane 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 as raw materials. Plant-derived polyester resins include those in which some of the monomers are "derived from plant materials".

We will explain plant-derived polyester resins using PET and PEF as examples.

The synthesis reaction of PET is shown in formula (1). PET is synthesized by the dehydration reaction of 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).

[In formula (1), n is the stoichiometric coefficient (degree of polymerization) and is a number between 250 and 1100.]

Ethylene glycol is produced industrially by oxidizing ethylene and hydrating it, and terephthalic acid is produced industrially by oxidizing paraxylene.
As shown in FIG. 1, when ethylene is obtained by a dehydration reaction of plant-derived ethanol (bioethanol), and PET is synthesized from ethylene glycol (bioethanol-derived ethylene glycol) and terephthalic acid derived from a petrochemical product, the PET produced is 30% by mass plant-derived PET.
Furthermore, as shown in FIG. 2, when paraxylene is obtained by a dehydration reaction of plant-derived isobutanol (bioisobutanol) and PET is synthesized from terephthalic acid synthesized from this paraxylene and ethylene glycol derived from bioethanol, the PET produced is 100% plant-derived PET by mass.

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

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

Furandicarboxylic acid (FDCA) can be obtained, for example, by dehydrating plant-derived fructose or glucose to obtain hydroxymethylfurfural (HMF), and then oxidizing the HMF.
As shown in FIG. 3, when both FDCA and ethylene glycol are plant-derived, the produced PEF is 100% by mass plant-derived PEF.

The glass transition temperature Tg of the polyester resin is preferably 50 to 100°C, more preferably 60 to 90°C, and even more preferably 70 to 85°C. If Tg is equal to or higher than the lower limit, the heat resistance and dimensional stability upon heating can be improved. If Tg is equal to or lower than the upper limit, the molding cycle can be shortened to increase productivity and moldability. Note that "moldability" refers to the ability to approximate a desired shape when, for example, foamed particles are filled into a mold cavity and heated to cause secondary foaming; the closer to the desired shape, the "better" the moldability.

The melting point of the 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 and dimensional stability under heat can be 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.

The intrinsic viscosity (IV value) of the polyester resin is preferably 0.5 to 1.5, more preferably 0.6 to 1.3, and even more preferably 0.7 to 1.2. When the IV value is equal to or greater than the lower limit, cell breakage during foaming is suppressed, and the open cell ratio can be further reduced. When the IV value is equal to or less than the upper limit, the density can be further reduced, the surface can be made smoother, and the beauty of the appearance can be improved.
The IV value can be measured by the method of JIS K7367-5 (2000).

The number average molecular weight Mn of the polyester resin is from 9,000 to 45,000, preferably from 15,000 to 43,000, and more preferably from 20,000 to 40,000.
When Mn is equal to or greater than the lower limit, the cold resistance (i.e., mechanical strength at low temperatures) can be further improved. When Mn is equal to or less than the upper limit, the heat resistance can be further improved.

The Z-average molecular weight Mz of the polyester resin is from 50,000 to 500,000, preferably from 180,000 to 450,000, and more preferably from 100,000 to 400,000.
If Mz is within the above range, the cold resistance (i.e., mechanical strength at low temperatures) can be further improved.

Mn and Mz can be measured by the following method.
[Molecular weight of polyester resin]
Take 5 mg of sample from the measurement object, add 0.5 mL of hexafluoroisopropanol (HFIP) and 0.5 mL of chloroform in this order, and shake gently by hand. Leave it for 24 ± 1.0 hr. After confirming that the sample is completely dissolved, dilute it to 10 mL with chloroform, shake gently by hand, and mix. Then, filter it with a non-aqueous 0.45 μm chromato disk manufactured by GL Science Co., Ltd. or a non-aqueous 0.45 μm syringe filter manufactured by Shimadzu GLC Co., Ltd. to obtain a measurement sample. Measure the measurement sample with a chromatograph under the following measurement conditions, and obtain the number average molecular weight Mn and Z average molecular weight Mz of the sample from the standard polystyrene calibration curve prepared in advance.

〔measuring device〕
Measurement device: "HLC-8320GPC EcoSEC" gel permeation chromatograph (with built-in RI detector and UV detector) manufactured by Tosoh Corporation.
[GPC measurement conditions]
・Column (sample side)
Guard column = 1 TSK guard column HXL-H (6.0 mm x 4.0 cm) manufactured by Tosoh Corporation.
Measurement column: TSKgel GMHXL (7.8 mm I.D. x 30 cm) x 2 columns in series, manufactured by Tosoh Corporation.
<Reference side>
Two resistance tubes (inner diameter 0.1 mm x 2 m) in series.
Column temperature = 40°C.
Mobile phase = chloroform.
<Dynamic phase flow rate>
Sample side pump = 1.0 mL/min.
Reference pump = 0.5 mL/min.
Detector = UV detector (254 nm).
Injection volume = 15 μL.
Measurement time = 26 minutes.
Sampling pitch = 500 ms.

[Standard polystyrene sample for calibration curve]
The standard polystyrene samples for the calibration curve are those having mass average molecular weights Mw of 5,620,000, 3,120,000, 1,250,000, 442,000, 131,000, 54,000, 20,000, 7,590, 3,450, and 1,320 and are selected from the product names "STANDARD SM-105" and "STANDARD SH-75" manufactured by Showa Denko K.K.
The above calibration curve standard polystyrene is grouped into A (5,620,000, 1,250,000, 131,000, 20,000, 3,450) and B (3,120,000, 442,000, 54,000, 7,590, 1,320). A is weighed (2 mg, 3 mg, 4 mg, 4 mg, 4 mg) and then dissolved in 30 mL of chloroform. B is weighed (3 mg, 4 mg, 4 mg, 4 mg, 4 mg) and then dissolved in 30 mL of chloroform.
The standard polystyrene calibration curve is obtained by preparing a calibration curve (cubic equation) from the retention times obtained after injecting 50 μL of each of the prepared solutions A and B. The number average molecular weight Mn and Z average molecular weight Mz are calculated using the calibration curve.

The content ratio of polyester-based resin to the total mass of thermoplastic resin contained in the expanded beads is preferably 40 to 95 mass%, more preferably 45 to 90 mass%, even more preferably 50 to 80 mass%, and particularly preferably 50 to 70 mass%. If the content ratio of polyester-based resin is equal to or higher than the above lower limit, moldability can be improved. If the content ratio of polyester-based resin is equal to or lower than the above upper limit, heat resistance strength can be further improved.

<Polyimide resin>
The polyimide resin is not particularly limited, but is preferably a polymer containing a cyclic imide group as a repeating unit, and is preferably a polymer having melt moldability.
Examples of polyimide-based resins include polyetherimides described in U.S. Pat. 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, and Japanese Patent No. 2,598,478, and the like; Examples of the polymers include those described in Japanese Patent Publication No. 2599171, Japanese Patent Publication No. 9-48852, Japanese Patent No. 2565556, Japanese Patent No. 2564636, Japanese Patent No. 2564637, Japanese Patent No. 2563548, Japanese Patent No. 2563547, Japanese Patent No. 2558341, Japanese Patent No. 2558339, and Japanese Patent No. 2834580. 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 be made from recycled materials.
These polyimide resins may be used alone or in combination of two or more.

The polyimide resin is preferably a compound represented by the following formula (3):

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

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

Polyimide resins can be prepared by conventionally known manufacturing methods. For example, they can be obtained by dehydrating and condensing either or both of tetracarboxylic acid and its acid anhydride, which are raw materials from which R in formula (3) can be derived, and 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 methods for producing polyimide resins include a method in which polyamic acid is obtained and then subjected to heat ring closure. Alternatively, examples include a method in which chemical ring closure is performed using an acid anhydride and a chemical ring closure agent such as pyridine or carbodiimide, and a method in which the above tetracarboxylic anhydride and the above diisocyanate from which R' can be derived are heated to decarboxylate and polymerize.

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)propane. 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 its acid anhydride, etc.

Examples of diamines include benzidine, diaminodiphenylmethane, diaminodiphenylethane, diaminodiphenylpropane, diaminodiphenylbutane, diaminodiphenylether, diaminodiphenylsulfone, diaminodiphenylbenzophenone, o, m, p-phenylenediamine, tolylenediamine, xylylenediamine, and aromatic primary diamines having the 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 -octamethylenediamine, 1,9-nonamethylenediamine, 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 as a structural unit of these aliphatic and alicyclic primary diamines, and the like.

The glass transition temperature Tg of the polyimide resin is preferably 190 to 240°C, more preferably 200 to 230°C, and even more preferably 210 to 220°C. If Tg is equal to or higher than the lower limit, the heat resistance and dimensional stability upon heating can be improved. If Tg is equal to or lower than the upper limit, the molding cycle can be shortened to increase productivity and improve moldability.

The melt flow rate (MFR) of the polyimide resin is preferably 3 to 30 g/10 min, more preferably 5 to 25 g/10 min, and even more preferably 7 to 20 g/10 min. If the MFR is equal to or higher than the lower limit, the molding cycle can be shortened to increase productivity and moldability. If the MFR is equal to or lower than the upper limit, heat resistance and dimensional stability under heat can be further improved.

The number average molecular weight of the polyimide resin is preferably 5,000 to 50,000, more preferably 6,000 to 39,000, and even more preferably 7,000 to 27,000. If the number average molecular weight of the polyimide resin is equal to or greater than the lower limit, the impact resistance can be further improved. If the number average molecular weight of the polyimide resin is equal to or less than the upper limit, the moldability can be further improved.

The content of polyimide resin relative to the total mass of thermoplastic resin contained in the expanded beads is preferably 5 to 60 mass%, more preferably 10 to 55 mass%, even more preferably 20 to 50 mass%, and particularly preferably 30 to 50 mass%. If the content of polyimide resin is equal to or greater than the lower limit, the heat resistance strength can be further improved. If the content of polyimide resin is equal to or less than the upper limit, the moldability can be further improved.

The thermoplastic resin contained in the expanded particles may contain recycled raw materials. Either the polyester-based resin or the polyimide-based resin may contain recycled raw materials, or both the polyester-based resin and the polyimide-based resin may contain recycled raw materials. A part or all of the polyester-based resin may be recycled raw materials for polyester-based resins, and a part or all of the polyimide-based resin may be recycled raw materials for polyimide-based resins.
Examples of recycled raw materials include the following raw materials:
1) Foamed beads or foamed bead molded bodies or other foamed bodies are pulverized to obtain flake-like resin, which is then remelted in an extruder, extruded in the form of strands from a nozzle die, cooled, and pelletized to produce recovered pellets.
2) Recycled PET made by crushing PET bottles to obtain flake-like resin, which is remelted in an extruder and extruded into strands through a nozzle die, which are then cooled and pelletized.

Other resins
The expanded beads are substantially free of thermosetting resin. "Substantially free" means that the expanded beads are completely free of thermosetting resin or are free of thermosetting resin to such an extent that the quality of the expanded beads is not affected. The content of the thermosetting resin in the expanded beads is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and most preferably 0% by mass, based on 100 parts by mass of the thermoplastic resin.

The thermoplastic resin may include a thermoplastic resin (other thermoplastic resin) other than the polyester resin and the polyimide resin. Examples of the other thermoplastic resin include polyolefin resins such as polyethylene and polypropylene, polystyrene resins, polyphenylene ether resins, polyamide resins, polycarbonate resins, polyarylate resins, polyphenylsulfone resins, polysulfone resins, and polyethersulfone resins.

The combined proportion of polyester-based resin and polyimide-based resin relative to the total mass of thermoplastic resin is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and most preferably 100% by mass. If the combined proportion of polyester-based resin and polyimide-based resin is equal to or more than the above lower limit, the heat resistance of the expanded particles can be further increased.

<Physical Properties>
The expanded beads have a single glass transition temperature Tg. The polyester resin and the polyimide resin are compatible with each other, resulting in a single glass transition temperature Tg. Since the expanded beads have a single glass transition temperature Tg, the glass transition temperature Tg is higher than the glass transition temperature Tg of the polyester resin, and the heat resistance of the expanded bead molding is increased.
The term "single glass transition temperature" means that the glass transition temperature Tg can be recognized as a single temperature on the lower side 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, it means that the glass transition temperature Tg can be recognized as a single temperature range (30 to 300° C.) in the second heating process.
The glass transition temperature Tg of the expanded beads is, for example, preferably 80 to 130° C., more preferably 85 to 125° C., and even more preferably 90 to 120° C. When Tg is equal to or higher than the lower limit, the heat resistance and dimensional stability upon heating of the expanded beads molded article can be further improved. When Tg is equal to or lower than the upper limit, the molding cycle can be shortened to increase productivity and moldability.
The glass transition temperature Tg of the expanded beads is 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 regarded as the same as the glass transition temperature Tg of the thermoplastic resin constituting the expanded beads.

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 lower limit, the degree of crystallization 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 upper limit, the degree of crystallization is not too high, and excellent secondary foaming properties and heat fusion properties are exhibited, and moldability and mechanical strength can be improved.
The endothermic heat release difference is the difference between the amount of heat absorbed and the amount of heat released, as determined by heat flux differential scanning calorimetry at a heating rate of 10° C./min.
The endothermic heat generation difference in the expanded beads can be regarded as the same as the endothermic heat generation difference of the thermoplastic resin constituting the expanded beads.

In the expanded beads, the temperature at which the loss tangent tan δ 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 tan δ is maximized is equal to or higher than the lower limit, the temperature at which the expanded bead molding softens is higher, and the heat resistance of the expanded bead molding can be further improved. If the temperature at which the loss tangent tan δ is maximized is equal to or lower than the upper limit, the temperature at which the expanded bead molding softens is not excessively high, and the moldability can be further improved.
The temperature at which the loss tangent tan δ 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.

<Foaming Agent>
Examples of the blowing agent include saturated aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, and hexane, ethers such as dimethyl ether, fluorocarbons such as methyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, and monochlorodifluoromethane, carbon dioxide, and nitrogen, with dimethyl ether, propane, normal butane, isobutane, carbon dioxide, and nitrogen being preferred. These blowing agents may be used alone or in combination of two or more.

The amount of foaming agent contained is not particularly limited, but is preferably, for example, 0.1 to 12 parts by mass per 100 parts by mass of resin.

<Optional ingredients>
The expanded beads of the present embodiment may contain other components (optional components) in addition to the thermoplastic resin and the foaming agent.
Optional components include cell regulators, stabilizers, UV absorbers, colorants, antioxidants, crystallization accelerators, lubricants, crosslinking agents, surfactants, shrinkage inhibitors, flame retardants, and deterioration inhibitors.

Examples of the crosslinking agent include acid dianhydrides such as pyromellitic anhydride, polyfunctional epoxy compounds, oxazoline compounds, oxazine compounds, etc. By blending a crosslinking agent in the resin composition, cell breakage during foaming is suppressed, and the open cell ratio can be further reduced.
The content of the crosslinking agent is preferably, for example, 0.08 to 0.8 parts by mass with respect to 100 parts by mass of the resin.

The cell regulator is, for example, a mixture of inorganic powder such as talc, silica, etc. These cell regulators increase the closed cell ratio of the expanded beads, making it easier to form the expanded beads.
The content of the cell regulator is preferably, for example, 0.2 to 5 parts by mass with respect to 100 parts by mass of the resin.

Examples of the stabilizer include calcium zinc-based heat stabilizers, tin-based heat stabilizers, and lead-based heat stabilizers.
The content of the stabilizer is preferably, for example, 1 part by mass or less with respect to 100 parts by mass of the resin.

Examples of the ultraviolet absorbing agent include a cesium oxide-based ultraviolet absorbing agent and a titanium oxide-based ultraviolet absorbing agent.
The content of the ultraviolet absorbing agent is preferably, for example, 1 part by mass or less with respect to 100 parts by mass of the resin.

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 part by mass or less with respect to 100 parts by mass of the resin.

Examples of colorants include titanium oxide, carbon black, titanium yellow, iron oxide, ultramarine blue, 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 for food containers, it is preferable to select from the above colorants a product registered with the Hygienic Council.
The content of the colorant is, for example, preferably 2 parts by mass or less with respect to 100 parts by mass of the resin.

Examples of the crystallization promoter include silicates, carbon, metal oxides, etc. Examples of silicates include talc, which is hydrated magnesium silicate. Examples of carbon include carbon black, carbon nanofiber, carbon nanotubes, carbon nanohorns, activated carbon, graphite, graphene, coke, mesoporous carbon, glassy carbon, hard carbon, soft carbon, etc., and 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, for example, preferably 3 parts by mass or less with respect to 100 parts by mass of the resin.

The above-mentioned optional components may each be used alone or in combination of two or more.
The total amount of the optional components contained in the expanded beads is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, based on the total mass of the expanded beads.

<Physical Properties>
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, 0.5 to 5 mm.
The average particle size of the expanded particle group is a value expressed as D50.
Specifically, a low tap type sieve shaker (manufactured by Iida Manufacturing Co., Ltd.) was used to shake the powder using JIS standard sieves (JIS Approximately 25 g of the sample was classified for 10 minutes using a sieve sizer (Z8801-1:2006), and the weight of the sample on the sieve was measured. A cumulative weight distribution curve was created from the results obtained, and the particle size (median size) at which the cumulative weight was 50% was taken as the average particle size.

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 improved, and the moldability and mechanical strength can be improved. The open cell ratio of the expanded beads can be determined by the method described in JIS K7138:2006 "Rigid foamed plastics - Determination of open cell ratio and closed cell ratio".

The apparent density of the expanded beads is, for example, preferably 0.027 to 0.675 g/cm ³ , more preferably 0.045 to 0.45 g/cm ³ , and even more preferably 0.0675 to 0.27 g/cm ^3. When the apparent density is equal to or higher than the lower limit, the cushioning force of the expanded beads molding can be increased. When the apparent density is equal to or lower than the upper limit, the mechanical strength of the expanded beads molding can be increased.

The bulk expansion ratio of the expanded particles 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 cushioning force can be increased. If the bulk expansion ratio is equal to or less than the upper limit, the mechanical strength can be increased.

The average bubble 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 bubble diameter is equal to or greater than the lower limit, the cushioning power can be increased. If the average bubble diameter is equal to or less than the 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.

<Production Method>
Examples of the method for producing the expanded beads of the present invention include a method in which a resin composition containing a thermoplastic resin and a foaming agent is extruded and foamed to obtain expanded beads, and a method in which a thermoplastic resin is extruded to obtain resin particles, and the obtained resin particles are impregnated with a foaming agent to obtain expanded beads.
More specifically, the method for producing the expanded beads may be, for example, the following method.
1) A method in which a thermoplastic resin and a foaming agent are fed into an extruder and melt-kneaded, and the molten resin composition is extruded into the air through holes in a die provided at the tip of the extruder to cause foaming, and while being extruded and foamed, the composition is cut into spherical particles, which are then dropped into water and cooled to obtain foamed particles.
2) A method in which a thermoplastic resin and a foaming agent are fed into an extruder and melt-kneaded, and the molten resin composition is extruded into water through holes in a die provided at the tip of the extruder to foam and cool, and the extruded, foamed, cooled and simultaneously cut to obtain cut, expanded spherical particles.
3) A method in which a thermoplastic resin and a foaming agent are fed into an extruder and melt-kneaded, the molten resin composition is extruded into water through holes in a die provided at the tip of the extruder and cooled, and is cut at the same time as being extruded and cooled to obtain cut spherical expandable particles, and the expandable particles are heated to obtain expanded particles.
4) A method in which a thermoplastic resin is fed into an extruder and melt-kneaded, the molten thermoplastic resin is extruded into the air through holes in a die provided at the tip of the extruder, cut as it is extruded, the cut spherical resin particles are dropped into water and cooled to obtain 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.
5) A method in which a thermoplastic resin is fed into an extruder and melt-kneaded, the molten thermoplastic resin is extruded into water through holes in a die provided at the tip of the extruder and cooled, the resin is extruded and cooled and simultaneously cut to obtain spherical 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.
6) A method in which a thermoplastic resin is fed into an extruder and melt-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 guided into water to cool, and after cooling, the resin is cut to a specified length to obtain cylindrical 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.

Below, we will explain in more detail the method of extruding the resin composition into the air to foam it, then cutting it into spherical particles that are then dropped into water to cool.

The extruder used for producing the expanded beads of the present invention will be described.
The expanded bead manufacturing apparatus 10 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 penetrates a front part 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 on the front end surface 1a of the nozzle die 1 at equal intervals on the same imaginary circle A centered on the rotation axis 2 (see FIG. 5).

The number of nozzles in the nozzle die 1 (i.e., the number of outlets 11) is preferably 2 to 80. If the number of nozzles is one, the production efficiency of expanded beads may decrease. If the number of nozzles is more than 80, extruded foams extruded and foamed from adjacent nozzles may come into contact with each other and coalesce. In addition, expanded beads obtained by cutting the extruded foam may coalesce with each other. 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 0.2 to 2 mm. If the opening diameter of the outlet 11 is less than 0.2 mm, the extrusion pressure may become too high, making extrusion foaming difficult. If the opening diameter of the outlet 11 is more than 2 mm, the diameter of the expanded particles may become large, decreasing the efficiency of filling the mold. The opening diameter of the outlet 11 is more preferably 0.3 to 1.6 mm, and particularly preferably 0.4 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, fracture 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 and extrusion foaming may not be possible. The length of the land portion is more preferably 5 to 20 times.

A rotary shaft 2 is disposed in a portion of the front end surface 1a of the nozzle die 1 surrounded by the nozzle outlet portion 11 so as to protrude forward.
One or more rotary blades 5 are integrally provided on the outer circumferential surface of the rear end of the rotating 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 rotating shaft 2, the multiple rotary blades 5 are arranged at equal intervals in the circumferential direction of the rotating shaft 2. Also, Fig. 5 shows, as an example, a case in which four rotary blades 5 are integrally provided on the outer circumferential surface of the rotating shaft 2.
As the rotating shaft 2 rotates, the rotating blade 5 moves along an imaginary circle A on which the nozzle outlet 11 is formed while constantly contacting the front end face 1a, and is configured to be able to cut the extruded foam extruded from the nozzle outlet 11 in sequence and continuously.
The expanded bead manufacturing apparatus 10 is provided with a cooling member 4 surrounding at least the front end surface 1a of the nozzle die 1 and the rotating shaft 2. The cooling member 4 is provided with a cylindrical cooling drum 41 with a bottom, which has a front part 41a having a circular shape larger in diameter than the nozzle die 1 and a cylindrical peripheral wall part 41b extending rearward from the outer periphery of the front part 41a.

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

An exhaust port 41e is formed in the lower surface of the front end of the peripheral wall portion 41b. The exhaust port 41e penetrates the peripheral wall portion 41b. An exhaust pipe 41f is connected to the exhaust port 41e on the outer surface of the peripheral wall portion 41b.
The extruder is not particularly limited as long as it is a conventionally used extruder, and examples thereof include a single screw extruder, a twin screw extruder, and a tandem type extruder in which a plurality of extruders are connected together.

A method for producing expanded beads using the expanded bead producing apparatus 10 will be described.
The cooling liquid 42 is supplied from the supply pipe 41d into the cooling drum 41 through the supply port 41c. The supplied cooling liquid 42 advances forward (toward the front part 41a) in a spiral shape along the inner circumferential surface of the peripheral wall part 41b due to centrifugal force associated with the flow speed when being supplied. While the cooling liquid 42 advances along the inner circumferential surface of the peripheral wall part 41b, the cooling liquid 42 gradually spreads in a direction perpendicular to the advancement direction (i.e., the circumferential direction of the peripheral wall part 41b). The cooling liquid 42 that has spread in the circumferential direction of the peripheral wall part 41b entirely covers the inner circumferential surface of the peripheral wall part 41b in front of the supply port 41c.

The cooling liquid 42 is not particularly limited as long as it can cool the foamed particles, and examples thereof include water and alcohol. Considering the disposal after use, water is preferable.
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 is not 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.

While rotating the rotary blade 5, the resin composition is extruded from the outlet 11 of the nozzle.
The glass transition temperature Tg of the polyester resin (raw polyester resin) blended in the resin composition is preferably 50 to 100°C, more preferably 60 to 90°C, and even more preferably 70 to 85°C. If Tg is equal to or higher than the lower limit, the heat resistance and dimensional stability upon heating can be further improved. If Tg is equal to or lower 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 foamed particles are filled into a cavity of a mold and heated to cause secondary foaming, and the closer to the desired shape, the "better" the moldability.

The melting point of the raw 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 and dimensional stability under heat can be 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.

The intrinsic viscosity (IV value) of the raw material polyester resin is preferably 0.5 to 1.5, more preferably 0.6 to 1.3, and even more preferably 0.7 to 1.2. When the IV value is equal to or higher than the lower limit, cell breakage during foaming can be suppressed, and the open cell ratio can be further reduced. When the IV value is equal to or lower than the upper limit, the density can be further reduced, and the surface of the foamed bead molding can be made smoother, improving the beauty of the appearance.
The IV value can be measured by the method of JIS K7367-5 (2000).

The number average molecular weight Mn of the raw material polyester resin is from 9,000 to 45,000, preferably from 15,000 to 43,000, and more preferably from 20,000 to 40,000.
When Mn is equal to or greater than the lower limit, the cold resistance (i.e., mechanical strength at low temperatures) of the expanded bead molding can be further improved. When Mn is equal to or less than the upper limit, the heat resistance of the expanded bead molding can be further improved.

The Z-average molecular weight Mz of the raw material polyester resin is from 50,000 to 500,000, preferably from 80,000 to 450,000, and more preferably from 100,000 to 400,000.
When Mz is within the above range, the cold resistance of the foamed bead molding can be further improved.

The resin composition is extruded from the nozzle die 1 to become an extruded foam, which is then cut by the rotary blade 5 to become particulate cut pieces. All of the rotary blades 5 rotate while constantly in contact with the front end face 1a, and the extruded foam extruded from the nozzle die 1 is cut in the atmosphere at regular time intervals to become particulate cut pieces by the shear stress generated between the rotary blade 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 cooled excessively.

The resin composition is prevented from foaming in the nozzle of the nozzle mold 1. The resin composition is not foamed immediately after being discharged from the outlet 11 of the nozzle, and starts to foam a short time after being discharged. Therefore, the extruded foam is composed of an unfoamed portion immediately after being discharged from the outlet 11 of the nozzle, and a foamed portion that is continuous with the unfoamed portion and is extruded ahead of the unfoamed portion and is in the process of foaming.
The unfoamed portion maintains its state from the time it is discharged from the outlet 11 of the nozzle until foaming begins. The time during which this unfoamed portion is maintained can be adjusted by the resin pressure at the outlet 11 of the nozzle, the amount of foaming agent, etc. If the resin pressure at the outlet 11 of the nozzle is high, the resin composition does not foam immediately after being extruded from the nozzle mold 1, and maintains an unfoamed state. The adjustment of the discharge pressure of the thermoplastic resin at the outlet 11 of the nozzle can be adjusted by the opening diameter of the outlet 11 of the nozzle, the extrusion amount, and the melt viscosity and melt tension of the resin composition. In addition, by adjusting the amount of foaming agent to an appropriate amount, the thermoplastic resin composition is prevented from foaming inside the nozzle mold 1, and the unfoamed portion can be reliably formed.
Since all of the rotary blades 5 are constantly in contact with the front end face 1a while cutting the extruded foam, the extruded foam becomes particulate cut material in the unfoamed portion immediately after being discharged from the nozzle outlet 11.

The rotation speed of the rotary blade 5 is preferably 2000 to 10000 rpm, more preferably 2000 to 9000 rpm, and particularly preferably 2000 to 8000 rpm. If the rotation speed is equal to or higher than the lower limit, the extruded foam can be cut more reliably by the rotary blade 5, preventing coalescence and making the foam particles more uniform in shape. If the rotation speed is equal to or lower than the upper limit, sufficient time is ensured until the foam reaches the cooling liquid 42 described below, and the bulk expansion ratio can be further increased.

As shown in FIG. 6, the particulate cut material P cut by the rotary blade 5 is scattered toward the inner wall of the cooling drum 41 due to the cutting stress of the rotary blade 5 at the same time as cutting, and collides with the cooling liquid 42 that covers the inner surface of the peripheral wall portion 41b. The particulate cut material continues to foam until it collides with the cooling liquid 42, and the particulate cut material grows into an approximately spherical shape due to foaming. Therefore, the resulting foamed particles are approximately spherical. At this time, it is preferable that the particulate cut material P collides with the cooling liquid 42 obliquely 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 particulate cut material P collides with the cooling liquid 42, the particulate cut material P collides with the cooling liquid 42 from the direction following the flow of the cooling liquid 42, so that the particulate cut material P is not repelled by the surface of the cooling liquid 42, and the particulate cut material P smoothly and reliably enters the cooling liquid 42, is cooled by the cooling liquid 42, and becomes a foamed particle.

According to this embodiment, after the extruded foam is cut by the rotary blade 5, the particulate cut material is immediately cooled by the cooling liquid 42, thereby preventing the particulate cut material from expanding excessively and obtaining expanded beads having the desired bulk expansion ratio.
In addition, since the particulate cut pieces are cooled immediately after cutting the extruded foam, the increase in the crystallinity of the expanded beads is suppressed. Therefore, the expanded beads exhibit excellent secondary foaming properties and heat fusion properties, and the resulting expanded bead molding has excellent mechanical strength. Furthermore, by increasing the crystallinity of the expanded bead molding of the polyester resin during in-mold foaming, the heating dimensional stability can be further improved.

The expanded particles 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 outside the cooling drum 41. The discharged expanded particles are separated from the cooling liquid 42 and dried as necessary. Methods for separating the expanded particles from the cooling liquid 42 include, for example, conventional solid-liquid separation methods such as passing through a sieve.

(Thermoplastic resin expanded particle molding)
The thermoplastic resin expanded bead molding (expanded bead molding) of the present embodiment is obtained by expanding and fusing expanded beads together. Examples of the expanded bead molding include parts of transportation equipment such as automobiles, aircraft, railroad cars, and ships, and cushioning materials and housings of electrical products. Examples of automotive parts include members used near the engine, exterior materials, and heat insulating materials. Examples of the expanded bead molding include food packaging containers such as fish boxes and vegetable boxes, and cushioning materials, packaging materials, structural members, and heat insulating materials used in electrical products.

The size of the foamed bead molding is not particularly limited and is determined appropriately taking into account the intended use.

The expanded bead molding exhibits a single glass transition temperature Tg. The polyester resin and the polyimide resin are compatible with each other, resulting 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 increasing the heat resistance 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 85 to 125° C., and even more preferably 90 to 120° C. If Tg is equal to or higher than the lower limit, the heat resistance and dimensional stability under heating of the expanded bead molding can be further improved. If Tg is equal to or lower than the upper limit, the moldability is improved and the appearance is beautifully finished.

The endothermic heat generation difference of the expanded bead molding is preferably 3 to 35 J/g, more preferably 10 to 30 J/g, and even more preferably 15 to 28 J/g. When the endothermic heat generation difference is equal to or greater than the lower limit, the crystallinity is increased and the heat dimensional stability of the expanded bead molding can be improved. When the endothermic heat generation 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 release difference is the difference between the amount of heat absorbed and the amount of heat released, as determined by heat flux differential scanning calorimetry at a heating rate of 10° C./min.

In the expanded bead molding, the temperature at which the loss tangent tan δ 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 tan δ is maximized is equal to or greater than the lower limit above, the temperature at which the expanded bead molding softens is higher, and the heat resistance of the expanded bead molding can be further improved. If the temperature at which the loss tangent tan δ is maximized is equal to or less than the upper limit above, the temperature at which the expanded bead molding softens does not become excessively high, and moldability can be further improved.

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 foamed plastics - Determination of open cell ratio and closed cell ratio".

The apparent density of the expanded bead molding is, for example, preferably 0.027 to 0.675 g/ ^cm3 , more preferably 0.045 to 0.45 g/ ^cm3 , and even more preferably 0.0675 to 0.27 g/ ^cm3 . When the apparent density of the expanded bead molding is equal to or higher 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 lower than the above upper limit, the expanded bead molding can be made lighter.

The expansion ratio of the expanded bead molding is, for example, preferably 2 to 50 times, more preferably 3 to 30 times, and even more preferably 5 to 20 times. If 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. If 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.

The average bubble diameter of the expanded bead molding is, for example, preferably 5 to 500 μm, more preferably 10 to 400 μm, and even more preferably 20 to 300 μm. When the average bubble diameter of the expanded bead molding is equal to or greater than the lower limit, the impact resistance of the expanded bead molding can be further improved. When the average bubble diameter of the expanded bead molding is equal to or less than the 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.

<Production Method>
The expanded bead molding using the expanded beads can be produced by a conventionally known production method.
Examples of the method for producing the expanded bead molding include the following method.
1) A method in which expanded beads (bulk expansion ratio: 2 to 50 times) are filled into a mold, which is then heated to cause secondary expansion of the expanded beads to form secondary expanded beads while fusing them together, and then an expanded bead molding (expansion ratio: 2 to 50 times) is produced by in-mold expansion molding (heat molding step).
2) A method in which expanded beads are heated to an arbitrary bulk expansion ratio to form pre-expanded beads (bulk expansion ratio: 2 to 50 times) (pre-expanding step), the pre-expanded beads are filled into a molding die, which is heated to cause secondary expansion of the pre-expanded beads to form secondary expanded beads while fusing them, and an expanded bead molding (expansion ratio: 2 to 50 times) is formed by in-mold expansion molding (heat molding step).

An example of a method for secondary foaming is to heat the inside of a mold cavity with water vapor.
The secondary foaming temperature is preferably, for example, 100 to 180°C.
The time for secondary expansion (that is, the time for supplying steam to the mold) is preferably 5 to 120 seconds.
In the secondary foaming, water vapor may be supplied into the cavity from the female mold side, or water vapor may be supplied into the cavity from the male mold side, or these may be alternately performed.
Furthermore, the expanded beads may be impregnated with an inert gas or air (hereinafter referred to as an inert gas or the like) to improve the secondary expansion power of the expanded beads (internal pressure application step). Examples of the inert gas include carbon dioxide, nitrogen, helium, and argon.
As a method for impregnating the expanded beads with an inert gas or the like, for example, there is a method in which the expanded beads are placed in an atmosphere of an inert gas or the like having a pressure equal to or higher than normal pressure, thereby impregnating the expanded beads with the inert gas or the like. The expanded beads may be impregnated with the inert gas or the like before being filled into a mold, or the expanded beads 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 having a gauge pressure (based on atmospheric pressure) of 0.1 to 2 MPa for 20 minutes to 24 hours.

Following the heat molding process, the foamed bead molded body in the mold may be further heated to increase the crystallinity of the thermoplastic resin (heat retention process).

(Foamed resin composite)
The foamed resin composite body has the foamed bead molding of the present invention and a fiber-reinforced resin layer (skin material) provided on at least a part 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 applications as a component for transport equipment. In addition, the foamed resin composite can also be suitably used as a building material, a windmill blade, a robot arm, a housing for an electrical appliance, a cushioning material for a helmet, a transport container such as an agricultural box or a thermal insulation container, a rotor blade for an industrial helicopter, or a packaging material for parts.
Examples of transport equipment components include structural members that constitute the main body of transport equipment such as automobiles, aircraft, railroad cars, ships, etc. Examples of structural members that constitute the main body of an automobile include door panels, door inners, bumpers, fenders, fender supports, engine covers, roof panels, trunk lids, floor panels, center tunnels, crash boxes, cowls, etc. For example, when a resin composite is used for a door panel that has conventionally been made of steel plate, it has substantially the same rigidity as a steel plate door panel and can be significantly lighter, thereby reducing the weight of the automobile.

For example, the 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.

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 examples thereof include carbon fibers, glass fibers, aramid fibers, boron fibers, metal fibers, etc. Among these, carbon fibers, glass fibers, and aramid fibers are preferred because they have excellent mechanical strength and heat resistance, and carbon fibers are more preferred.
The form of the fiber is not particularly limited, and examples thereof include woven fabrics, knitted fabrics, nonwoven fabrics, and face materials formed by bundling (sewing) fiber bundles (strands) of fibers aligned in one direction with synthetic resin threads such as polyamide resin, polyester resin, etc., or stitch threads such as glass fiber threads, etc. Examples of the weaving method of the fabric include plain weave, twill weave, satin weave, etc.
The fibers may be (1) a multilayer face material formed by laminating multiple sheets of woven fabric, knitted fabric, or nonwoven fabric together or in any combination thereof, or (2) a multilayer face material formed by bundling (stitching) multiple face materials formed by bundling (stitching) fiber bundles (strands) in which the fibers are aligned in one direction with a stitch thread such as a synthetic resin thread such as polyamide resin or polyester resin or a glass fiber thread, and 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 together with a stitch thread such as a synthetic resin thread such as polyamide resin or polyester resin or a glass fiber thread.

Examples of the resin contained in the fiber reinforced resin layer 104 include uncured thermosetting resins and thermoplastic resins. The thermosetting resin is 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 they have excellent heat resistance, elastic modulus, and chemical resistance. The thermosetting resin may contain additives such as a curing agent and a curing accelerator. The thermosetting resin may be used alone or in combination of two or more types.
The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resins such as polyethylene resins and polypropylene resins, acrylic resins, polyester resins, polyamide resins, and polycarbonate resins.
The resin content of the fiber reinforced resin layer 104 is preferably 20 to 70 mass %, more preferably 30 to 60 mass %, based on 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.

The method of impregnating the fibers with the resin is not particularly limited, and examples include (1) immersing the fibers in the resin, and (2) applying the resin to the fibers.

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.

The thickness of the fiber reinforced resin layer 104 is, for example, preferably 0.1 to 5 mm, and more preferably 0.3 to 3 mm. If the thickness of the fiber reinforced resin layer 104 is equal to or greater than the above 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 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 as or different from each other.

<Production 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 on 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 bonding the fiber-reinforced resin layer 104 to the surface of the expanded bead molding 102 using the thermoplastic resin as a binder. (4) a method of laminating a fiber-reinforced resin layer 104 in a softened state by heating on the surface of the foamed bead molding 102, and pressing the fiber-reinforced resin layer 104 against the surface of the foamed bead molding 102 to bond the fiber-reinforced resin layer 104 to the foamed bead molding 102. In the method (4), it is also possible to deform the fiber-reinforced resin layer 104 along 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 a high-temperature environment, the method (4) can also be used preferably.
By these methods, the fiber-reinforced resin layer 104 can be integrally provided on the surface of the foamed bead molding 102 .
Examples of a method for joining the fiber reinforced resin layer 104 to the surface of the expanded bead molding 102 include an autoclave method, a hand layup method, a spray-up method, a PCM (Prepreg Compression Molding) method, an RTM (Resin Transfer Molding) method, and a Vacuum assisted Resin Transfer Molding (VaRTM) method.

The foamed resin composite of the above embodiment has a flat-shaped foamed bead molding, but the present invention is not limited thereto, and the shape of the foamed 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 to this. 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.

In the expanded beads of this embodiment, the polyester resin and the polyimide resin are compatible with each other, and the thermoplastic resin has a single glass transition temperature, so that the glass transition temperature Tg is higher than the glass transition temperature Tg of the polyester resin, and the heat resistance strength is improved. Therefore, the expanded bead molded article obtained by hot molding the expanded beads has excellent heat resistance strength.
In addition, the expanded beads of the present embodiment exhibit excellent heat resistance without requiring a heat retention step, and therefore the productivity of the expanded bead molding can be improved. The expanded bead molding of the present embodiment exhibits excellent heat resistance even when the crystallinity is less than 20%.
Furthermore, the expanded bead molding of this embodiment is produced through a heat retention step, so that the crystallinity is increased and the dimensional stability upon heating is further improved.

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

(Raw materials used)
<Polyester Resin>
PET (A): manufactured by Far East New Century Co., Ltd., product name "CH-611", glass transition temperature Tg: 78 ° C., melting point: 251 ° C., IV value: 1.02, biomass degree: 0%.
PET (B): manufactured by INDRAMA, product name "RAMAPET N1B", glass transition temperature Tg: 78°C, melting point: 247°C, IV value: 0.80, biomass degree: 30%.
PET (C): manufactured by Far East New Century Co., Ltd., product name "CH-653", glass transition temperature Tg: 79 ° C., melting point: 248 ° C., IV value: 1.01, biomass degree: 27 to 30%.
PET (D): manufactured by Far East Ishizuka Green Pet Co., Ltd., product name "CB-603RJ", glass transition temperature Tg: 79 ° C., melting point: 248 ° C., IV value: 0.80, biomass degree: 0%, recycled PET from recycled PET bottles.

<Polyimide resin>
PEI (A): Polyetherimide, manufactured by SABIC Innovative Plastics, trade name "Ultem 1000", glass transition temperature Tg: 217°C, MFR: 9g/10min.
PEI (B): Polyetherimide, manufactured by SABIC Innovative Plastics, trade name "Ultem 1010", glass transition temperature Tg: 217°C, MFR: 17.8 g/10 min.

<Amorphous polyester resin>
PCT(G): Eastman Chemical Company, trade name "Traitan TX-1001", aromatic dicarboxylic acid component = terephthalic acid, diol component = 1,4-cyclohexanedimethanol and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, glass transition temperature Tg: 107°C, IV value: 0.72.

<Talc masterbatch>
Talc MB: A master batch consisting of PET = 72% by mass and talc = 28% by mass.

<Crosslinking Agent>
- PMDA: Pyromellitic anhydride.

(Evaluation method of expanded beads)
<Bulk density>
The bulk density of the expanded beads was measured in accordance with JIS K6911:1995 "General testing method for thermosetting plastics". Measurement was performed using an apparent density measuring device in accordance with JIS K6911, and the bulk density of the expanded beads was calculated based on the following formula (s1).
Bulk density of expanded beads (kg/m ³ )=[mass of measuring cylinder containing expanded beads (kg)−mass of measuring cylinder (kg)]/[volume of measuring cylinder (m ³ )] (s1)

<Bulk expansion ratio>
The bulk expansion ratio of the expanded beads was determined by dividing the density of the thermoplastic resin obtained from the blending ratio of each example by the bulk density of the expanded beads. The following values were used for the density of each resin.
-PET: 1.35g/cm ³ .
- PEI: 1.28g/cm ³ .
-PCT: 1.18g/cm ³ .

<Open cell ratio>
The open cell ratio of the expanded beads was measured by the following method. First, a sample cup for a volumetric air comparison type pycnometer was prepared, and the total mass A (g) of the expanded beads was measured so as to fill about 80% of the sample cup. Next, the total volume B (cm ³ ) of the expanded beads was measured by the 1-1/2-1 atmospheric pressure method using a pycnometer. For the measurement, a Tokyo Science "Volumetric Air Comparison Type pycnometer Model 1000" was used.
A wire mesh container was prepared, and the wire mesh container was immersed in water to measure the mass C (g) of the wire mesh container when immersed in water. All the expanded beads were placed in the wire mesh container, and the wire mesh container was immersed in water to measure the mass D (g) of the wire mesh container when immersed in water and the total amount of expanded beads placed in the wire mesh container. The masses of the expanded beads and the wire mesh container were measured using Yamato Scale's "Electronic Balance HB3000" (minimum scale 0.01 g).
The apparent volume E (cm ³ ) of the expanded beads was calculated based on the apparent volume E and the total volume B (cm 3 ) of the expanded beads, and the open cell ratio of the expanded beads was calculated based on the apparent volume E and the total volume B (cm ³ ) of the expanded beads using the following formula (s2). The volume of 1 g of water was taken as 1 cm ³ . In this measurement, the expanded beads were stored in advance for 16 hours in an environment of 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 ... (s2)
(E=A+(CD))

<Melting point, crystallization temperature, glass transition temperature Tg>
The melting point, crystallization temperature and glass transition temperature Tg were measured by 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 product was packed into the bottom of an aluminum measurement container at 5.5±0.5 mg without leaving any gaps, and then the container was covered with an aluminum lid. Differential scanning calorimetry was then carried out using a Hitachi High-Tech Science DSC7000X, AS-3 differential scanning calorimeter. The sample was heated and cooled in the following steps 1 to 4 under a nitrogen gas flow rate of 20 mL/min to obtain a DSC curve.
(Step 1) Hold 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 temperature increase process) and held for 10 minutes.
(Step 3) The sample is quickly removed and allowed to cool in an environment of 25±10°C.
(Step 4) Heat the mixture 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 attached to the device, the top temperatures of the melting peak and the crystallization peak observed during the second heating process were read as shown in Figure 8 (measurement results of Example 3), and were taken as the melting point and the crystallization temperature. The glass transition temperature Tg was calculated as the midpoint glass transition temperature from the DSC curve observed during the second heating process using the analysis software attached to the device. This midpoint glass transition temperature was obtained from 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 in the second heating process in a 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 used.

<Endothermic Amount (a), Heat Amount (b), Crystallinity>
The endothermic amount (a) (amount of heat of fusion) and the exothermic amount (b) (amount of heat of crystallization) were measured by 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 product was packed into the bottom of an aluminum measurement container at 5.5±0.5 mg without leaving any gaps, and then the container was covered with an aluminum lid. Differential scanning calorimetry was then carried out 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 in the following steps 1 and 2 to obtain a DSC curve.
(Step 1) Hold at 30°C for 2 minutes.
(Step 2) Heat the temperature from 30° C. to 300° C. at a rate of 10° C./min (first heating process).
Alumina was used as the reference material. The endothermic heat (a) and the calorific heat (b) were calculated using analysis software attached to the device. Specifically, as shown in FIG. 4, the endothermic heat (a) was calculated from the area enclosed by the line connecting the point where the DSC curve leaves the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline, and the DSC curve. The calorific heat (b) was calculated from the area enclosed by the line connecting the point where the DSC curve leaves the low-temperature baseline and the point where the DSC curve returns to the high-temperature baseline, and the DSC curve.
The degree of crystallinity is determined by the following method. First, the difference between the endothermic amount (a) and the exothermic amount (b) is determined. The difference is divided by the theoretical heat of fusion of a completely crystalline polyethylene terephthalate, 140.1 J/g, to determine the degree of crystallinity.
That is, the crystallinity is calculated from the following formula (s3).
Crystallinity (%)=(endothermic amount (a) (J/g)−heat generation amount (b) (J/g))/140.1 (J/g)×100 (s3)

(Method of evaluating expanded bead moldings)
<Density>
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". Expanded bead moldings of 100 cm3 or ^more were cut without changing the original cell structure of the material, and the mass was measured. The density was calculated by the following formula (s4).
Density (g/cm ³ )=mass (g) of expanded bead molding/volume (cm ³ ) of expanded bead molding (s4)

<Expansion ratio>
The bulk expansion ratio of the expanded bead molding 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 molding obtained. The following values were used for the density of each resin.
-PET: 1.35g/cm ³ .
- PEI: 1.28g/cm ³ .
-PCT: 1.18g/cm ³ .

<Solid viscoelasticity measurement>
The solid viscoelasticity was measured using an "EXSTRAR DMS6100" viscoelasticity spectrometer manufactured by SII Nano Technology Co., Ltd. The surface skin layer was removed from the foamed bead molding, and a cylindrical sample with a diameter of about 10 mm and a thickness of about 2 mm was cut out. The conditions were as follows.
Mode: Compression control mode.
Atmosphere: Nitrogen atmosphere.
- Frequency: 1Hz.
Heating rate: 5°C/min.
・Measurement temperature: 30°C to 300°C.
Strain amplitude: 5 μm.
-Minimum compression force: 100mN.
Tension gain: 1.5.
Initial force amplitude: 100 mN.
The analysis was performed using analysis software provided with the device. The temperature at which the loss tangent tan δ is maximum is the temperature at which the loss tangent tan δ is maximum in the measured values in the temperature range of 50 to 240°C.
The dimensions of the test pieces were measured using a "DIGIMATIC" CD-15 type manufactured by Mitutoyo Corporation.

<Dimensional change rate upon heating (evaluation of dimensional stability upon heating)>
The thermal dimensional change rate of the expanded bead molding was measured by the method B described in JIS K6767:1999 "Foamed plastics - Polyethylene - Test method". A test piece having a planar shape of a square with a side of 150 mm and a thickness of the expanded bead molding was cut out from the expanded bead molding. Three parallel 100 mm straight lines were drawn at 50 mm intervals in the vertical and horizontal directions of the center of the test piece. The lengths of the three straight lines were measured in the vertical and horizontal directions, and their arithmetic mean value L0 was taken as the initial dimension. Thereafter, the test piece was left in a hot air circulation dryer set at 100 ° C. and 120 ° C. for 168 hours to perform a heating test. After the heating test, the test piece was taken out and left at 25 ° C. for 1 hour. Next, the lengths of the three straight lines drawn on the surface of the test piece in the vertical and horizontal directions were measured, and their arithmetic mean value L1 was taken as the dimension after heating. The thermal dimensional change rate was calculated based on the following formula (s5).
Heat dimensional change rate (%) = 100 × | (L1 - L0) | / L0 ... (s5)
The results of the measurement of the rate of dimensional change of the expanded bead moldings at each set temperature were evaluated according to the following criteria.

<Evaluation Criteria>
⊚: The rate of dimensional change upon heating is less than 1.0%.
◯: The rate of dimensional change upon heating is 1.0% or more and less than 1.5%.
Δ: The rate of dimensional change upon heating is 1.5 or more and less than 2.0.
×: The rate of dimensional change upon heating is 2.0 or more.

<Flexural modulus (heat resistance)>
The flexural modulus in the bending test was measured according to the method described in JIS K7221-1:2006. The flexural modulus was measured using a Shimadzu Corporation "Autograph AG-X plus 100kN" universal testing machine and a Shimadzu Corporation "TRAPEZIUM X" universal testing machine data processing machine. Test pieces were cut out from the foamed bead moldings to a size of 25 mm wide x 130 mm long x 20 mm thick. The test speed was 10 mm/min. The radius of the tip of the pressure wedge and the support stand was 5R. The distance between the supports was 100 mm. The test pieces were conditioned for 16 hours under a standard atmosphere of JIS K7100:1999 symbol "23/50", class 2, and then used for measurement.
The measurements were carried out under standard atmosphere and at 80° C. At 80° C., the specimens were conditioned for 24 hours in a thermostatic chamber set at 80° C., then removed from the thermostatic chamber, and immediately placed on a jig installed in a thermostatic chamber attached to a Shimadzu Corporation "TCR2A type" thermostatic chamber, and held for 3 minutes before measurement. The number of specimens at each of the above atmospheric temperatures was 5.
The flexural modulus was calculated by setting the load region where the slope of the linear part of the load-strain relationship was maximum, and processing the data from the universal testing machine. The arithmetic mean of the flexural modulus measurements for each test piece was taken as the flexural modulus value.
The retention rate was calculated based on the following formula (s6) using the flexural modulus at 80° C. (E80) and the flexural modulus under standard atmosphere (23° C.) (E23).
Retention rate (%)=(E80)/(E23)×100...(s6)
The results of the retention of the flexural modulus of the expanded bead moldings were evaluated according to the following criteria.

<Evaluation Criteria>
A: Retention rate is 80% or more.
A: The retention rate is 75% or more and less than 80%.
Δ: The retention rate is 70% or more and less than 75%.
×: The retention rate is less than 70%.

<Appearance>
The surface of the expanded bead molding was visually inspected and evaluated according to the following criteria.
<Evaluation Criteria>
⊚: There are no gaps between the foamed particles, the surface of the molded article is very smooth, and the appearance of the molded article is very good.
◯: The gaps between the expanded particles are very small, the surface of the molded article is almost smooth, and the appearance of the molded article is good.
Δ: The gaps between the foamed particles are small, there are small irregularities on the surface of the molded article, and the appearance of the molded article is somewhat poor.
x: There are many gaps between the expanded particles, the surface of the molded article is significantly uneven, and the appearance of the molded article is significantly poor.

<Overall evaluation>
The evaluation results of the thermal dimensional change rate, flexural modulus and appearance were classified according to the following evaluation criteria.

Evaluation Criteria
: All items were rated as 'A'.
◯: All items were rated as either "◎" or "◯", with at least one being "◯".
Δ: There were no "x" marks in the evaluation of any item, and at least one "Δ" mark was given in the evaluation of any item.
×: Any of the items was rated as “×”.

Example 1
Expanded beads were produced by the following procedure using a production apparatus similar to the expanded bead production apparatus 10 shown in FIGS.
First, according to the formulation in the table, the polyester resin, the polyimide resin, the talc master batch and the crosslinking agent were fed to a single-screw extruder having a cylinder diameter D of 65 mm and an L (cylinder length) / D (cylinder diameter) ratio of 34, and were melt-kneaded at 290 ° C. Then, from the middle of the extruder, butane (isobutane: normal butane = 35: 65 (mass ratio)) was pressed into the molten melt-kneaded product in the amount shown in the table, and uniformly dispersed in the molten kneaded product to obtain a resin composition. After that, the molten resin composition was heated to 300 ° C. at the front end of the extruder, and the resin composition was extruded and foamed from each nozzle of the multi-nozzle type nozzle mold 1 attached to the front end of the extruder. The extrusion rate of the resin composition was 30 kg / h.
The nozzle die 1 had 20 nozzles with an outlet portion 11 having a diameter of 1 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 portion of the rotating shaft 2 with a phase difference of 180° in the circumferential direction of the rotating 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 1a of the nozzle die 1.

The cooling member 4 was provided with a cooling drum 41 consisting of a front part 41a having a circular shape at the front and a cylindrical peripheral wall part 41b extending rearward from the outer periphery of the front part 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 17684 cm ³ .
The cooling liquid 42 advances forward in a spiral shape along the inner peripheral surface of the peripheral wall portion 41b of the cooling drum 41 due to centrifugal force associated with the flow speed when it is supplied from the supply pipe 41d to the inner peripheral surface of the peripheral wall portion 41b of the cooling drum 41. As the cooling liquid 42 advances along the inner peripheral surface of the peripheral wall portion 41b, the cooling liquid 42 gradually spreads in a direction perpendicular to the advancement direction, and entirely covers the inner peripheral surface of the peripheral wall portion 41b forward of the supply port 41c of the cooling drum 41.

The rotary blade 5 disposed on the front end surface 1a was rotated at a rotation speed of 3400 rpm, and the extruded foam extruded and foamed from the outlet 11 of each nozzle of the nozzle die 1 was cut by the rotary blade 5 to produce roughly spherical granular cut pieces. The extruded foam consisted of an unfoamed portion immediately after being extruded from the nozzle of the nozzle die 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 outlet 11 of the nozzle, and the cutting of the extruded foam was carried out in the unfoamed portion.
In the production of the expanded beads, first, the rotating shaft 2 was not attached to the nozzle die 1, and the cooling member 4 was retracted from the nozzle die 1. In this state, the resin composition was extruded and foamed from the extruder to produce an extruded foam, which was confirmed to consist of an unfoamed part immediately after being extruded from the nozzle of the nozzle die 1 and a foamed part in the process of foaming that was continuous with the unfoamed part. Next, the rotating shaft 2 was attached to the nozzle die 1 and the cooling member 4 was disposed at a predetermined position, and then the rotating shaft 2 was rotated to cut the extruded foam with the rotating blade 5 at the open end of the outlet 11 of the nozzle to produce particulate cut products.

The particulate cut pieces are thrown outward or forward by the cutting stress of the rotary blade 5, and collide 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 pieces enter the cooling liquid 42 and are 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 by a dehydrator.

An in-mold foaming molding machine equipped with molds (male and female molds) was prepared. When the male and female molds were clamped together, a rectangular parallelepiped cavity with inside dimensions of 300 mm length × 400 mm width × 30 mm height was formed between the male and female molds.
Then, after filling the mold with the foamed particles in a state where the mold cracking is removed by 3 mm, steam was introduced from the female mold for 30 seconds so that the inside of the cavity was 0.08 MPa (gauge pressure) (one-sided heating), then steam was introduced from the male mold for 30 seconds so that the inside of the cavity was 0.08 MPa (gauge pressure) (reverse one-sided heating), then steam was supplied from both the male and female molds for 30 seconds so that the inside of the cavity was 0.12 MPa (gauge pressure) (double-sided heating), the foamed particles were heated and secondary foamed, and the secondary foamed particles were heat-fused and integrated with each other. After that, the introduction of steam into the cavity was stopped and the state was maintained for 300 seconds (heat retention process), and finally, a cooling liquid was supplied into the cavity to cool the foamed particle molding in the mold, and the cavity was opened to take out the foamed particle molding.
At this time, the time required from the step of filling the mold with the expanded beads to obtaining an expanded bead molded article (molding cycle time) was 600 seconds.

(Examples 2-3, 6, 8-9, 11-13, Comparative Examples 1, 3-4)
The polyester resin, polyimide resin, talc master batch, crosslinking agent and foaming agent were blended as shown in the table, and the molding conditions were as shown in the table. Except for this, the procedure of Example 1 was repeated to prepare expanded beads and expanded bead moldings.
FIG. 9 shows the measurement results of the loss tangent tan δ of Example 3, and FIG. 10 shows the measurement results of the loss tangent tan δ of Comparative Example 1.

Example 4
The same expanded beads as in Example 3 were used to prepare an expanded bead molding in the same manner as in Example 1, except that the molding conditions shown in the table were used.

Example 5
The expanded beads were prepared in the same manner as in Example 1, except that the polyester resin, polyimide resin, talc master batch, crosslinking agent, and foaming agent were mixed as shown in the table. The expanded beads thus prepared were allowed to stand in a thermostatic chamber at 150° C. for 1 hour to expand the expanded beads, thereby obtaining pre-expanded beads. The physical properties of the obtained pre-expanded beads are shown in the table.
The pre-expanded particles were left at room temperature (23° C.) for 1 day, then sealed in a pressure vessel, and the inside of the pressure vessel was replaced with nitrogen gas, after which nitrogen gas was injected until the impregnation pressure (gauge pressure) reached 0.5 MPa, and the particles were allowed to stand in an environment of 20° C., and pressure curing was carried out for 8 hours (internal pressure application step).
The pre-expanded beads subjected to the internal pressure application step were heated with steam at 0.30 MPa (gauge pressure) for 30 seconds to cause secondary expansion, and the secondary expandability was confirmed to be almost the same as that of the expanded beads obtained in Example 3.
Using the pre-expanded beads subjected to the internal pressure imparting step, an expanded bead molding was produced in the same manner as in Example 1, except that the molding conditions shown in the table were used.

(Example 7)
The same expanded beads as in Example 6 were used to prepare expanded bead moldings in the same manner as in Example 1, except that the molding conditions shown in the table were used.

Example 10
The same expanded beads as in Example 3 were remelted in a twin-screw extruder, extruded into strands from a nozzle die, cooled, and pelletized to prepare recovered pellets. Except for following the blending and molding conditions in the table, the same procedure as in Example 1 was followed to prepare expanded beads and expanded bead molded articles.

(Comparative Example 2)
The same expanded beads as those in Comparative Example 1 were used to produce expanded bead moldings in the same manner as in Example 1, except that the molding conditions shown in the table were used.

(Comparative Example 5)
The same expanded beads as in Comparative Example 4 were used to prepare expanded bead moldings in the same manner as in Example 1, except that the molding conditions shown in the table were used.

In Examples 1 to 13 in which the present invention was applied, the heat resistance strength (flexural modulus) was evaluated as "△" to "◎", and the overall evaluation was evaluated as "△" to "◎".
Comparative Examples 1 and 2, which did not contain PEI, and Comparative Examples 3 to 5, which did not have a single glass transition temperature, were rated "x" for heat resistance strength (flexural modulus) and the overall rating was "x".
From the above results, it was confirmed that the application of the present invention can improve the heat resistance strength of the expanded thermoplastic resin bead molding.

(Example 14)
<Preparation of foamed resin composite>
A fiber-reinforced resin layer-forming material (CFRP, "Pyrofil Prepreg TR3523 381GMX" manufactured by Mitsubishi Rayon Co., Ltd., basis weight: 200 g/m ² ) having a thickness of 0.22 mm was prepared, which was made by adding 40 mass% of uncured epoxy resin as a thermosetting resin to a fiber-reinforced substrate formed from a twill weave of carbon fiber. Two layers of the fiber-reinforced resin layer-forming material were placed on both sides of the foamed bead molding obtained in Example 3 to form a laminate, and the fiber-reinforced resin layer-forming material was bonded to the surface of the foamed bead molding by an autoclave method. Specifically, a pressure of 0.3 MPa was applied to the laminate, and the laminate was heated at 130°C for 60 minutes to cure the thermosetting resin in the fiber-reinforced resin layer-forming material, and the fiber-reinforced resin layer-forming material was bonded to both sides of the foamed bead molding by the cured thermosetting resin.
The appearance of the resulting foamed resin composite was visually observed, and it was confirmed that the surface of the skin material was free of irregularities and that the foamed resin composite had a beautiful appearance.

100: foamed resin composite body 102: foamed bead molding 104: fiber-reinforced resin layer

Claims (18)

Contains a thermoplastic resin,
The thermoplastic resin includes a polyester resin and a polyimide resin,
The polyimide resin is a polyetherimide resin,
The thermoplastic resin foam particles have a single glass transition temperature Tg. The thermoplastic resin foam particles according to claim 1, wherein the glass transition temperature Tg is 80 to 130°C. The thermoplastic resin expanded particles according to claim 1 or 2, in which the absolute value of the difference between the endothermic heat amount and the heat generated heat amount determined by heat flux differential scanning calorimetry at a heating rate of 10°C/min is 3 to 35 J/g. The content ratio of the polyester resin to the total mass of the thermoplastic resin is 40 to 95 mass %,
The content ratio of the polyimide resin to the total mass of the thermoplastic resin is 5 to 60 mass%.
The expanded thermoplastic resin particles according to any one of claims 1 to 3. The expanded thermoplastic resin particles according to any one of claims 1 to 4, wherein the temperature at which the loss tangent tan δ is maximized in solid viscoelasticity measurement at a heating rate of 5°C/min and a frequency of 1 Hz is 120 to 230°C. The expanded thermoplastic resin particles according to any one of claims 1 to 5 , wherein the polyester-based resin comprises a plant-derived polyester-based resin. The expanded thermoplastic resin particles according to any one of claims 1 to 6 , wherein the thermoplastic resin contains recycled materials. The method for producing expanded thermoplastic resin beads according to any one of claims 1 to 7 , further comprising a step of extruding and foaming a thermoplastic resin composition containing the thermoplastic resin and a foaming agent to obtain expanded thermoplastic resin beads. The method for producing expanded thermoplastic resin beads according to claim 8 , wherein the thermoplastic resin composition further contains a crosslinking agent. Contains a thermoplastic resin,
The thermoplastic resin includes a polyester resin and a polyimide resin,
The polyimide resin is a polyetherimide resin,
A foamed thermoplastic resin bead molding having a single glass transition temperature Tg. The foamed thermoplastic resin bead molding according to claim 10 , wherein the glass transition temperature Tg is 80 to 130° C. or less. The thermoplastic resin foamed bead molding according to claim 10 or 11 , wherein the absolute value of the difference between the endothermic amount and the exothermic amount determined by heat flux differential scanning calorimetry at a heating rate of 10 ° C. / min is 3 to 35 J / g. The content ratio of the polyester resin to the total mass of the thermoplastic resin is 40 to 95 mass %,
The content ratio of the polyimide resin to the total mass of the thermoplastic resin is 5 to 60 mass%.
The expanded thermoplastic resin bead molding according to any one of claims 10 to 12 . The thermoplastic resin foamed bead molding according to any one of claims 10 to 13 , wherein the temperature at which the loss tangent tan δ is maximized in solid viscoelasticity measurement at a heating rate of 5 ° C. / min and a frequency of 1 Hz is 120 to 230 ° C. The thermoplastic resin foamed bead molding according to any one of claims 10 to 14 , wherein the polyester-based resin comprises a plant-derived polyester-based resin. The thermoplastic resin foamed bead molding according to any one of claims 10 to 15 , wherein the thermoplastic resin contains recycled materials. 10. 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 8 or 9 ; 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. The thermoplastic resin foamed bead molding according to any one of claims 10 to 16 , and a fiber-reinforced resin layer provided on at least a portion of the surface of the thermoplastic resin foamed bead molding. A foamed resin composite.

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